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Wang, Yaolun. "Vibrational measurement techniques applied on FE-model updating." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-45213.
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In this thesis, the dynamics of two plates overlapping and connected by three bolts are studied. The data collected in the test are used in modal analysis. The vibrational test and the modal analysis were made using an LMS system. Hammer excitation is used for the tests. The main purpose of this thesis is to study how the suspensions affect the extracted eigenfrequencies and modal dampings. In this thesis, more than 10 suspensions were examined. Another objective in this thesis work is to build an FE-model. This model is made using the software Abaqus. To improve the reliability of the FE-model, a set of reliable experimental data is used to calibrate the model. The calibrated FE-model, using the measurement data, has a dynamic behavior close to the measurement data.
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Yan, Kaidi. "The Abaqus/CAE Plug-in for Premium Threaded connection 3D parameter Finite Element Model." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78245.
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Finite Element Analysis (FEA) is proposed to simulate the connection response of practical in-service conditions and test the performance of Oil Country Tubular Goods (OCTG) premium threaded connections. A plug-in is developed in Abaqus/CAE for creating the 360-degree full 3D parametric finite element model with helical threads as an effective design and analysis tool. All size, position and material data of the model are parameterized. The premium connection plug-in accepts input from the Graphical User Interface (GUI) for further modification. Each premium connection component is programed as a collection of single-purpose independent functions organized as an independent module in order to allow users to modify specific function behavior conveniently. A main program is designed as an Abaqus kernel plug-in to achieve all the functions by calling these independent functions, making the plug-in flexible. Each single script file is not too long to jeopardize readability. The GUI of the plug-in is designed with proper layout arrangement and illustrations to make the plug-in user-friendly and easy to use. The premium connection FE model is used in a virtual test to validate the model against the ISO 13679 test protocol and is used to develop the seal metrics for points on the ISO 13679 sealability envelope. The plug-in can be used to develop and evaluate the design envelope of the premium connection.Master of Science
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Piątek-Sierek, Ewa. "Kalibracja parametrów określających właściwości betonu opisanego modelem plastyczno-degradacyjnym zaimplementowanym w programie ABAQUS." Rozprawa doktorska, [Nakł.aut.], 2013. http://dlibra.utp.edu.pl/Content/574.
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W pracy opisano i zidentyfikowano parametry podlegające kalibracji. Kalibrację modelu zaimplementowanego w programie ABAQUS przeprowadzono w oparciu o rezultaty badań własnych laboratoryjnych betonu oraz zależności empiryczne. Opracowano tzw. algorytm kalibracji oraz zamieszczono gotowe pakiety kalibracyjne dla betonów o typowych wartościach wytrzymałości na ściskanie.
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Li, Yumeng. "Study of Forming of Composite Materials with Abaqus CAE and The Preferred Fiber Orientation (PFO) Model." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1511719634128258.
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Feng, Fan. "Flutter Analysis of Stonecutters Cable-stayed Bridge using Finite Element Model." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32470.
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The current research analyzed the flutter response of the Stonecutters Cable-Stayed Bridge in Hong Kong, which has a twin deck configuration, under the effect of wind. The aerodynamic instability response of the bridge steel deck of the main span is mainly the focus of the current project.
Initially, a complete finite element bridge model was created in ABAQUS finite element software, representing all the structural elements of the Stonecutters Cable-Stayed Bridge in a lumped mass bridge model. The natural frequencies and the vibration modes were validated against the data available in the literature at first.
Secondly, the effect of the mean wind loading for wind speeds between 35 m/s and 211 m/s were determined. The vertical and horizontal displacements and the torsional angle at mid-span are indicated to determine the bridge performance under mean wind load.
Moreover the flutter instability was modeled based on Scanlan’s theory and the response of the bridge model at several different locations along the main and the side span and the top of the tower, were determined for wind speeds of 35 m/s and higher, where this critical aerodynamic instability is expected to occur. In addition, the responses of the bridge under natural wind data were also determined by applying a wind speed recorded data to the bridge model.
Finally, the critical flutter wind speed and the flutter frequency were determined by Fast Fourier Transform in MATLAB program. The flutter onset wind speed was also determined.
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Funtusov, E. "The computing of the casing scale model with using of ABAQUS system and tensile load." Thesis, Sumy state university, 2014. http://essuir.sumdu.edu.ua/handle/123456789/39217.
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The casing is under axial tensile loads during the life of the well because of the gravity force at lowering the casing. The critical section of the casing is situated on the wellhead and the tensile load arises because more joints are added to the string.
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Lantoine, Rémi. "A 3D sliding bearing finite element based on the Bouc-Wen model : Implementation in Abaqus." Thesis, KTH, Bro- och stålbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280479.
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As rail transportation is significantly more virtuous than airplanes or cars in terms of greenhousegases emissions, its development is being encouraged in several European countries, includingSweden. In addition, the development of railway lines on which trains can travel at higher speeds ismade in Sweden with the integration of existing infrastructure. On railway bridges, an increased trainspeed potentially leads to an increase in vibrations during passage, for which the structure may not bedesigned. It is therefore essential to know the dynamic properties of the structures used.Several studies highlight the influence of friction phenomena in sliding bearings on the dynamicproperties of bridges equipped with them. This Master Thesis is based on previous works that led tothe development of a finite element modelling the friction mechanisms that occur in these bearings.The friction occurring between a PTFE sliding plate and a steel surface is thus modelled using the Bouc-Wen model, a model for hysteresis phenomena. The finite element was developed as a Fortransubroutine, which can be integrated into the finite element calculation software Abaqus as a "userdefinedelement". It allows friction to be modelled along the longitudinal direction of the bridge onlyand can therefore only be used in two-dimensional models. The user-defined element is also based ona model that takes into account the influence of contact pressure and sliding velocity on the steel-PTFEcoefficient of friction. As several studies indicate, contact temperature can also have a significantinfluence on the value of the coefficient of friction but is not taken into account in the current model.In this project, the previously developed finite element was therefore generalized to account forfriction in both directions of the sliding plate by the means of a two-dimensional generalization of theBouc-Wen model. Based on experimental data available in scientific literature, the model forcalculating the coefficient of friction was also extended to take into account the influence of thecontact temperature. In addition, a model to update the contact temperature based on the theory ofsurface heating of semi-infinite bodies has been incorporated. Finally, this thesis presents theintegration of this updated finite element on three-dimensional models of the Banafjäl Bridge, locatedin northern Sweden. Simulations to estimate the fundamental frequencies and resonance modes ofthe structure as well as the temperature increase that can occur in a bearing during the passage of atrain were carried out on this model.
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Kodavati, Venkata Seshank, and Devi Prasad Buraga. "Study of Numerical Model Parameters and Crack Tip of a Packaging Materials." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13840.
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Packaging industries widely use Low-Density Polyethylene (LDPE) in manufacturing different types of containers to store the food products. They are difficult to model numerically in order to have similar experimental response. This research deals with the study of numerical material model parameters of continuum LDPE. It is carried out with the help of experiments along with the numerical simulation of LDPE. Study of stress-strain distribution at crack tip and elements close to the tip is carried out in the LDPE material with the pre-existing center crack with varying lengths. By implementing an optimization algorithm and automating the simulation with the help of python code, we obtain a set of parameters. This obtained data for the material can be used directly for numerical simulation in the future without carrying out additional experimental studies. After implementing the optimization algorithm is also validated, against the results that were close to the experimental response.
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Cravotta, Stefan, and Emanuele Grimolizzi. "Simulation of vehicle impact into a steel building : A parametric study on the impacted column end-connections." Thesis, KTH, Bro- och stålbyggnad, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172341.
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Understanding the true behaviour of impacted structures is the only way to assess their robustness under exceptional events such as vehicle collision. The primary objective of this master’s thesis was to perform a finite element parametric investigation on the influence that some parameters have in steel buildings subjected to vehicle impacts. The parameters chosen for the study, involved uncertainties in the material definition and in the load configuration of the bolts used in the impacted column end-connections. By using the Abaqus software, a finite element model of the structure has been created. The five storey steel building considered has been modelled in a simplified manner with the exception of the impacted area which, instead, has been defined in a more detailed fashion. During the simulations, different preload conditions have been used, comparing cases with and without the preload force. Regardless its variation, it has not been observed any increase in the structural resistance. On the other hand, the simulation provided interesting results for what concerns the material variations in the bolts. Although the changes have been small in magnitude, the effect on the structural response during the impact was remarkable. For all the cases considered, an increase of the material ductility, achieved by increasing the ultimate strain at failure, entailed higher resistance of the connections. Various failure modes have been observed when the material properties have been changed. Having clarified the influence of the assumptions made, the results provided helpful information in sight of future studies. Although the model still needs to be validated, the research clarified which of the parameters investigated are to be collected with more attention. Keywords: Vehicle collision, steel building, FE model, Abaqus/Explicit, parametric investigation, bolt preload, bolt material.
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Xu, Shengmin, and Peiwei Tan. "Glued timber connections : Experimental and numerical study of tension behavior under various influencing parameters." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-45371.
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Glued connections are relatively new in structural timber engineering. They are expected to show high connection stiffness as well as a high connection strength compared to mechanical connections e.g. dowel‐type connections.The main aim of this thesis is to characterize the behavior of glued timber connections under pure tension by conducting experiments as well as numerical simulations. Hereby the influence of different parameters is studied such as the geometry (bond-line length and thickness) and the material properties (e.g. adhesives of highly diverse stiffness). Additionally, reference tests on a dowel-type connection are made. The purpose is to see the differences between dowelled and glued connections and to see if there are some advantages in using glued timber connections (the base geometry was chosen acc. to Eurocode 5).Finite element models were created in the software ABAQUS. The models were used to predict the connection stiffness and compare this to the experimental results. In addition, parametric studies were performed on e.g. overlapping lengths. The comparison between experiments and simulations showed good agreement.It was found that glued connections with the adhesives SikaPower-4720 and SikaFast-5215 NT (an epoxy and an acrylate, respectively) had higher stiffness than the dowel connections, whereas connections with the silicone adhesive SikaSil SG-500 had a lower stiffness. A general conclusion drawn from this work is that the glued timber connections simulated in this project should also be suitable for application to complex connections and situations involving other loading situations than pure tension.
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Gopallawa, Praveen. "Fatigue Failure Model for Local Roads in Ohio that Use Road User Maintenance Agreements Due to the Increase in Truck Traffic." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1566389151107255.
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Özdemir, Hulya, and Azad Abbas. "Analyzing an Equivalent Single Layer Shim Model to be used for Brake Squeal Reduction." Thesis, Linnéuniversitetet, Institutionen för teknik, TEK, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-22386.
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The goal in this thesis was to reduce a multilayer shim model, which was modeled from steel and polymer (isotropic materials), into an equivalent single layer shim model. The procedure was to use mathematical formulations to convert a multilayer shim into an ESL (equivalent single layer) shim. Here, a transverse isotropic model is used to prepare for future orthotropic layers. The results show that the ESL model behaves isotropically. In the 2 layer model there was no squeal noise whereas in the ESL models there is.
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Nowacki, Brenna M. "Verification and Calibration of State-of-the-Art CMC Mechanistic Damage Model." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1461761780.
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Das, Satyajit. "Mechanics of 3D composites." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271189.
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This thesis contributes towards understanding of mechanical response of 3D composites and ceramics. Composite materials have widespread applications ranging from aerospace, civil sectors to sports and drones. One important application is in composite armours where composites and ceramic layers are used together. Therefore, it is important to study the mechanical response of these components to develop better armour systems. The first part of this thesis concerns with dynamic penetration response of confined ceramic targets. In the second part, mechanics of a novel 3D composite consisting of orthogonal carbon fibre tows is studied. The dynamic penetration of ceramic target by a long-rod projectile is studied using a mechanism based ceramic constitutive model. This is to capture and explain the essential physics observed during penetration of a ceramic target such as dwell and structural size effect. Dwell is captured using the constitutive model and the related physics is studied along with identification of causes of dwell. Origins of structural size effect in ceramics are identified and their influences are studied. In the second part of the thesis a novel 3D composite consisting of three mutually perpendicular orthogonal tows is studied under compression, indentation and three-point bending. Under compression along low fibre volume fraction direction (Z), the 3D composite forms stable and multiple kinks in the Z tows resulting in 10% ductility. This contrasts with traditional UD or 2D composites which fail catastrophically at 2% strain. The stability in the case of the 3D composite is due to the constraint imposed by the surrounding material. Under indentation, the 3D composite has a near isotropic and ductile response. In contrast, traditional cross-ply composites show highly anisotropic response where indentation results in brittle failure along in-plane direction. Under three-point bending, the response was ductile in Z-direction and brittle in other two directions. Overall, the 3D composite studied in this thesis shows improvement over traditional CFRPs in ductility and energy absorption capability. The 3D composite has been demonstrated to have smooth load-displacement curves reminiscent to indentation of metal in all three directions achieved at densities significantly lower than structural metals that display equivalent ductility. Thus, these 3D composites are strong candidates for applications where loading direction is unknown a-priori, and where high energy absorption is required along with reusability of the material.
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Jin, Hui, and Hao Wu. "Finite Element Modelling of Fracture in dowel-type timber connections." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-34783.
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Dowel-type steel to timber connections are commonly used in timber structure. The load carrying capacity and the stress distribution within the connection area are complicated and the failure behavior of a connection depends on many parameters. The main purpose of this thesis was to verify, using the data obtained from previous experiments, the conventional design method of European Code 5(EC5) (hand calculation) for dowel type joints subjected to pure bending moment and other alternative design methods based on the finite element method (FEM) including the use of the mean stress approach and the extended finite element method (XFEM). Finite element models were created in the software ABAQUS. The models were then used to predict the load bearing capacity and compare this to the experimental results. In addition parametric studies were performed with modifications of material properties and other parameters. The closest prediction in relation to the test results was obtained using XFEM where the predicted capacity was 3.82% larger than the experimental result. An extension of the mean stress method going from a 2D-formulation to a 3D-formulation was verified as well. A general conclusion drawn from this work is that the numerical modelling approaches used should also be suitable for application to complex connections and situations involving other loading situations than pure tension.
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Crudo, Cinzia. "Investigation on laser shock peening capability by FE simulation." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5534/.
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Laser shock peening is a technique similar to shot peening that imparts compressive residual stresses in materials for improving fatigue resistance.
The ability to use a high energy laser pulse to generate shock waves, inducing a compressive residual stress field in metallic materials, has applications in multiple fields such as turbo-machinery, airframe structures, and medical appliances.
The transient nature of the LSP phenomenon and the high rate of the laser's dynamic make real time in-situ measurement of laser/material interaction very challenging.
For this reason and for the high cost of the experimental tests, reliable analytical methods for predicting detailed effects of LSP are needed to understand the potential of the process.
Aim of this work has been the prediction of residual stress field after Laser Peening process by means of Finite Element Modeling.
The work has been carried out in the Stress Methods department of Airbus Operations GmbH (Hamburg) and it includes investigation on compressive residual stresses induced by Laser Shock Peening, study on mesh sensitivity, optimization and tuning of the model by using physical and numerical parameters, validation of the model by comparing it with experimental results.
The model has been realized with Abaqus/Explicit commercial software starting from considerations done on previous works.
FE analyses are “Mesh Sensitive”: by increasing the number of elements and by decreasing their size, the software is able to probe even the details of the real phenomenon. However, these details, could be only an amplification of real phenomenon. For this reason it was necessary to optimize the mesh elements' size and number.
A new model has been created with a more fine mesh in the trough thickness direction because it is the most involved in the process deformations.
This increment of the global number of elements has been paid with an "in plane" size reduction of the elements far from the peened area in order to avoid too high computational costs.
Efficiency and stability of the analyses has been improved by using bulk viscosity coefficients, a merely numerical parameter available in Abaqus/Explicit.
A plastic rate sensitivity study has been also carried out and a new set of Johnson Cook's model coefficient has been chosen.
These investigations led to a more controllable and reliable model, valid even for more complex geometries.
Moreover the study about the material properties highlighted a gap of the model about the simulation of the surface conditions.
Modeling of the ablative layer employed during the real process has been used to fill this gap.
In the real process ablative layer is a super thin sheet of pure aluminum stuck on the masterpiece.
In the simulation it has been simply reproduced as a 100µm layer made by a material with a yield point of 10MPa.
All those new settings has been applied to a set of analyses made with different geometry models to verify the robustness of the model.
The calibration of the model with the experimental results was based on stress and displacement measurements carried out on the surface and in depth as well.
The good correlation between the simulation and experimental tests results proved this model to be reliable.
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Al, Karkour Khaleel. "Unreinforced masonry walls and flange effect: a parametric study through block-based modeling." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
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This study reported in this thesis shows the flange effect in unreinforced masonry walls subjected to in-plane loading. Previous studies showed the importance of capturing the in-plane behaviour of flanged masonry walls for seismic studies. A generative tool was developed using Dynamo and Abaqus Scripting Interface (ASI) to make a parametric model covering most cases of constructing the flange wall. The analysis was held using Finite Element Method through ABAQUS software and masonry wall was modelled through block-based modelling strategy. Large parametric study was carried out to investigate the effects of several parameters on the collapse load and failure type. The effect of aspect ratio, length of flange part, location of the main part, vertical applied load and the applied boundary condition are represented in this thesis.
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Oktay, Emre Hasan. "Finite Element Analysis Of Laboratory Model Experiments On Behavior Of Shallow Foundations Under General Loading." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614210/index.pdf.
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In this study, a series of laboratory model experiments carried on shallow foundations is intended to be simulated through numerical modeling. The laboratory model tests were conducted by Fukui et al. (2005), over square shaped, shallow surfacial foundations located over air-dried Toyoura sand. Tests included centered vertical and combined loading cases on sand with 60% and 80% relative densities. Plastic limit loads obtained from numerical analyses and available analytical solutions in literature are compared to the laboratory test results and the differences are discussed.
Employment of Mohr - Coulomb yield criterion and linear elasticity, resulting in linear elastic perfectly plastic constitutive law, is one of the most common practices in modeling geotechnical problems. Accuracy of this approach for the modeled experiments is judged by comparison of analyses results with experimental findings and solutions in literature. Finite element method is utilized for modeling purposes, with Mohr-Coulomb yield criterion and linear elastic behavior. Abaqus 6-10.2 is selected as the analysis software, and two and three dimensional models are used in the analyses. Analyses, the results of which are compared with experimental findings, aim employment of associated flow rule. Additional analyses are conducted with varying dilation angles in order to examine the influence of unassociated flow rule on eccentric and concentric loading results.
Differences between the results of numerical analyses and experimental observations varied between 2% and 34%. Main reason of the difference is attributed to employed soil behavior modeling approach in analyses and the eccentric placement of model weight in monotonic horizontal loading experiments. In the case when this eccentric placement is accounted for in numerical models, it is seen that the difference diminished to vary between 8% and 18%, and order of the difference was similar for similar experiment cases. Therefore, based on this condition, it is seen that results of the modeled experiments are consistent, while in general they are somewhat higher than the results obtained from analyses and solutions in literature. Difference between the results of analyses and average of selected solutions in literature in both cases is at most 9%.
Finite element method employing Mohr-Coulomb failure criterion could provide results in close agreement with solutions in literature that inherently assume Mohr-Coulomb failure criterion as well. However, the same accuracy could not be obtained for experiments due to uncertainties involved in the material properties as well as the insufficiencies of the model to represent the behavior precisely. Finite element method has the potential to consider more advanced material models. Nonetheless, employment of Mohr-Coulomb failure criterion provides results with sufficient accuracy for most cases.
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Leidermark, Daniel. "Mechanical Behaviour of Single-Crystal Nickel-Based Superalloys." Thesis, Linköping University, Department of Management and Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-10722.
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In this paper the mechanical behaviour, both elastic and plastic, of single-crystal nickel-based superalloys has been investigated. A theoretic base has been established in crystal plasticity, with concern taken to the shearing rate on the slip systems. A model of the mechanical behaviour has been implemented, by using FORTRAN, as a user defined material model in three major FEM-programmes. To evaluate the model a simulated pole figure has been compared to an experimental one. These pole figures match each other very well. Yielding a realistic behaviour of the model.
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Abdullah, Ahmad Sufian. "Crash simulation of fibre metal laminate fuselage." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/crash-simulation-of-fibre-metal-laminate-fuselage(fd254489-243f-4071-8dea-ca9e2dd9d3bc).html.
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A finite element model of fibre metal laminate (FML) fuselage was developed in order to evaluate its impact response under survivable crash event. To create a reliable crash finite element (FE) model of FML fuselage, a ‘building block approach’ is adapted. It involves a series of validation and verification tasks in order to establish reliable material and damage models, verified impact model with structural instability and large displacement and verified individual fuselage structure under crash event. This novel development methodology successfully produced an FE model to simulate crash of both aluminium alloy and FML fuselage under survivable crash event using ABAQUS/Explicit. On the other hand, this allows the author to have privilege to evaluate crashworthiness of fuselage that implements FML fuselage skin for the whole fuselage section for the first time in aircraft research field and industry. The FE models consist of a two station fuselage section with one meter longitudinal length which is based on commercial Boeing 737 aircraft. For FML fuselage, the classical aluminium alloy skin was replaced by GLARE grade 5-2/1. The impact response of both fuselages was compared to each other and the results were discussed in terms of energy dissipation, crushing distance, failure modes, failure mechanisms and acceleration response at floor-level. Overall, it was observed that FML fuselage responded similarly to aluminium alloy fuselage with some minor differences which conclusively gives great confidence to aircraft designer to use FML as fuselage skin for the whole fuselage section. In terms of crushing distance, FML fuselage skin contributed to the failure mechanisms of the fuselage section that lead to higher crushing distance than in aluminium alloy fuselage. The existence of various failure modes within FML caused slight differences from the aluminium fuselage in terms of deformation process and energy dissipation. These complex failure modes could potentially be manipulated to produce future aircraft structure with better crashworthiness performance.
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Brennen, Peter Alexander. "SIMULATION OF AN OXIDIZER-COOLED HYBRID ROCKET THROAT: METHODOLOGY VALIDATION FOR DESIGN OF A COOLED AEROSPIKE NOZZLE." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/166.
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A study was undertaken to create a finite element model of a cooled throat converging/diverging rocket nozzle to be used as a tool in designing a cooled aerospike nozzle. Using ABAQUS, a simplified 2D axisymmetric model was created featuring only the copper throat and stainless steel support ring, which were brazed together for the experimental test firings. This analysis was a sequentially coupled thermal/mechanical model. The steady state thermal data matched closely to experimental data. The subsequent mechanical model predicted a life of over 300 cycles using the Manson-Halford fatigue life criteria. A mesh convergence study was performed to establish solution mesh independence.
This model was expanded by adding the remainder of the parts of the nozzle aft of the rocket motor so as to attempt to match the transient nature of the experimental data. This model included variable hot gas side coefficients in the nozzle calculated using the Bartz coefficients and mapped onto the surface of the model using a FORTRAN subroutine. Additionally, contact resistances were accounted for between the additional parts. The results from the preliminary run suggested the need for a parameter re-evaluation for cold side gas conditions. Parametric studies were performed on contact resistance and cold side film coefficient. This data led to the final thermal contact conductance of k=0.005 BTU/s•in.•°R for contact between metals, k=0.001 BTU/s•in.•°R for contact between graphite and metal, and h=0.03235 BTU/s2•in.•°R for the cold side film coefficient. The transient curves matched closely and the results were judged acceptable.
Finally, a 3D sector model was created using identical parameters as the 2D model except that a variable cold side film condition was added. Instead of modeling a symmetric one or two inlet/one or two outlet cooling channel, this modeled a one inlet/one outlet nozzle in which the coolant traveled almost the full 360° around the cooling annulus. To simplify the initial simulation, the model was cut at the barrier between inlet and outlet to form one large sector, rather than account for thermal gradients across this barrier. This simplified nozzle produced expected data, and a 3D full nozzle model was created. The cold side film coefficients were calculated from previous experimental data using a simplified 2D finite difference approach. The full nozzle model was created in the same manner as the 2D full nozzle model. A mesh convergence study was performed to establish solution mesh independence. The 3D model results matched well to experimental data, and the model was considered a useful tool for the design of an oxidizer cooled aerospike nozzle.
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Rajamanickam, Rajkumar. "Study of delamination of composite hat skin stringer interface failure." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-18837.
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The use of composite materials brought a tremendous breakthrough in the scientific world of aerospace engineering. The lack of understanding of the failure of composite materials can be disastrous. Composite laminated structures need to be thoroughly studied and investigated in the design stage. In this thesis, formed-hat skin stringer made of composite laminates is investigated. Delamination is the most common failure of laminated composites, which has two stages delamination onset and delamination propagation. In the preliminary design phase, firstly the structures need to be investigated for low-velocity impact to check the formation of damage onset due to the impact that may arise during manufacturing. In the detailed design phase, the structure is investigated to study the evolution of delamination growth under loading conditions. The structure is modeled using 3 D elements because of the presence of Interlaminar stresses in the width and thickness direction and anisotropic nature. In this thesis, more emphasis is given on the interface between the skin and the stringer. The debonding effect of the interface is studied using cohesive zone model(CZM).
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Birnie, Hernández Johan. "Simulation of crack growth in adhesively bonded joints via cohesive zone models." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25500/.
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Adhesively bonded joints have shown great advantages in the aerospace industry when compared with traditional mechanical fastening methods. These type of joints allow to reduce the overall structural weight, improve the fatigue life characteristics due to reduction of stress concentrations (uniform stress distribution), smooth external finish, sealed surfaces, and many others. One of the main concerns with these joints is their characterization under fatigue loading, i.e. a comprehensive study of crack growth which will allow the development of standardized tests and certification in the aerospace sector. Thus, the aim of this thesis is the development of user-defined subroutines implemented in finite element analysis commercial software, i.e. Abaqus, via Cohesive Zone Models for the study of crack growth in adhesively bonded joints under quasi-static and fatigue loading. Hence, a material user-defined subroutine (UMAT) was developed using cohesive zone models taken from literature and implemented in Abaqus to study disbonding under quasi-static and fatigue loading in 2D specimens. The studied specimens were a double cantilever beam (DCB), for pure mode I opening; and a crack shear lap (CLS), for mixed mode opening. Results of the simulations were compared with experimental data from work done previously by different authors. The data from the simulations showed the same behavior as the experimental data, thus validating the developed user-defined subroutines. For future work, it is recommended to implement the user-defined subroutine into 3D models, and again compare it with experimental data to validate it.
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Rashid, Shahbaz. "Parametric study of bridge response to high speed trains, ballasted track on concrete bridges." Thesis, KTH, Bro- och stålbyggnad, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-99385.
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When a train enters a bridge, passenger sitting inside will feel a sudden bump in the track, which not only affect the riding comfort of the passengers but also put a dynamic impact on the bridge structure. Due to this impact force, we have very serious maintenance problems in the track close to the bridge structure. This sudden bump is produced when train travelling on the track suddenly hit by a very stiff medium like bridge structure. In order to reduce this effect, transition zones are introduced before the bridge so that the change in stiffness will occur gradually without producing any bump. This master thesis examine the effect of track stiffness on the bridge dynamic response under different train speeds from 150 to 350 km/h with interval 5 km/h and also estimate the minimum length of transition zones require to reduce the effect of change in stiffness on the bridge. Study also gives us some guidelines about the choice of loading model of the train, location of maximum vertical acceleration, effect of ballast model on the results and minimum length of transition zone needs to include in the bridge-track FE-model, for dynamic analysis of the concrete bridges. To carry out this research MATLAB is used to produce an input file for the ABAQUS FEM program. ABAQUS will first read this file, model the bridge and then analysis the bridge. MATLAB will again read the result file, process the result data and plot the necessary graphs. The Swedish X2000 train is used for this study, which has been modeled with two different methods: moving load model and sprung mass model, in order to see the difference in results. For verification of the MATLAB-ABAQUS model, a 42m long bridge is analysed and results are compared with known results. In this study, concrete simply supported bridges with spans of 5, 10, 15, 20, 25 m have been analysed.
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Parris, Kadri. "Extension Of Stress-Based Finite Element Model Using Resilient Modulus Material Characterization To Develop A Theoretical Framework for Realistic Response Modeling of Flexible Pavements on Cohesive Subgrades." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437623013.
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Ouakka, Slimane. "On the static strength of reinforced joints." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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The title, On the Static Strength of Reinforced Joints, shows the main subject of this research. The main aim of this study is to analyze the static strength of joints when geometrical and/or mechanical parameters change, by the use of Finite Element (FE) Model.
In the current study a FE Model with the use of shell element was modelled as requested from the codes, that for a new configuration of Joints suggest using FE Models, and since this type of strategy are mesh dependent especially for cases where the concentration of stress is sharp it needs to be calibrated by using physical experiments.
Even if a three-dimensional is already present in the literature, through the shell model that requires much less computational effort, a great result was achieved. The results of this research and the references reveal a very good correlation in terms of load-ovalization curves and also in terms of deformed shape. Reflecting not only the shapes of curve and deformation but also even more relevant the different values of enhancement of the strength when the parameters varying as obtained in the Experimental Investigation.
The research is subdivided in four chapter, starting from the first chapter where the importance of this type of element is highlighted and the advantage in using this type of elements in the structures such as jackets of offshore platforms. This first followed by the explanation of the key points of the two previous reference. Then in the third chapter, the finite element strategy was explained and the results are shown. Finally, in the fourth chapter given the results of the previous chapters, some conclusions and considerations can be made.
In conclusion, this results can be used as a base of other typology of elementary joints as Y-joint, K-joint and X-joint, or a combination elementary joints.
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Furlanis, Silvia. "Towards a design approach for Wire-and-Arc Additively Manufactured stainless-steel elements." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24627/.
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Additive Manufacturing has become more and more relevant in the recent years in the construction industry, while still being at its initial stage. In particular, Wire-and-Arc Additively Manufactured (WAAM) stainless-steel elements have yet to be properly analyzed from a structural response point-of-view, though many experimental campaigns and studies are being carried out to this day.
This study is focused on the analysis of the results of tests conducted on WAAM-produced 308LSi stainless-steel specimens, in order to characterize the mechanical and geometrical properties of the printed material and calibrate design values by means of Annex D of Eurocode 0, which outlines procedures to carry out the safety analysis of the resistance function, hence the definition of partial safety factors, aiming at a semi-probabilistic design approach.
Moreover, by means of available Digital Twins of produced and tested specimens, different approaches are followed for the understanding of the influence of geometrical irregularities on the behavior of the material, in terms of stress-strain relationship. Regarding this, a series of calibrations are performed in order to quantify said influence, with a particular focus on the elastic behavior.
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Donnini, Lorenzo. "Numerical modelling of axially loaded piled foundations with physical tests validation." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
Find full textAbstract:
L'oggetto della tesi è la modellazione numerica di pali di fondazione per turbine eoliche in ambiente offshore.
Il metodo di modellazione comprende l'interpretazione di prove CPT per l'estrapolazione dei parametri geotecnici del terreno, la creazione di un modello dell'interazione tra struttura e terreno tramite il software agli elementi finiti Abaqus, la sua verifica, l'ottimizzazione dell'estensione del modello del terreno e della mesh e la simulazione numerica del comportamento di pali caricati assialmente in compressione.
Grazie al confronto con i risultati di test su modelli fisici, eseguiti nel laboratorio dell'istituto Fraunhofer IWES di Hannover, di tre pali aventi la stessa geometria ma installati in punti con diverse condizioni di compattazione della sabbia, è stata possibile la messa a punto di una strategia di simulazione più accurata possibile e la sua validazione.
A conclusione del lavoro è stato eseguito un esempio di design di una fondazione jacket per una turbina eolica offshore.
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Wills, Andrew Johan. "Abacus-Tournament Models of Hall-Littlewood Polynomials." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/64427.
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In this dissertation, we introduce combinatorial interpretations for three types of HallLittlewood polynomials (denoted Rλ, Pλ, and Qλ) by using weighted combinatorial objects called abacus-tournaments. We then apply these models to give combinatorial proofs of properties of Hall-Littlewood polynomials. For example, we show why various specializations of Hall-Littlewood polynomials produce the Schur symmetric polynomials, the elementary symmetric polynomials, or the t-analogue of factorials. With the abacus-tournament model, we give a bijective proof of a Pieri rule for Hall-Littlewood polynomials that gives the Pλ-expansion of the product of a Hall-Littlewood polynomial Pµ with an elementary symmetric polynomial ek. We also give a bijective proof of certain cases of a second Pieri rule that gives the Pλ-expansion of the product of a Hall-Littlewood polynomial Pµ with another Hall-Littlewood polynomial Q(r) . In general, proofs using abacus-tournaments focus on canceling abacus-tournaments and then finding weight-preserving bijections between the sets of uncanceled abacus-tournaments.Ph. D.
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Barrows, Richard James. "Two Dimensional Finite Element Modeling of Swift Delta Soil Nail Wall by "ABAQUS"." PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/4741.
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Soil nail walls are a form of mechanical earth stabilization for cut situations. They consist of the introduction of passive inclusions (nails) into soil cut lifts. These nailed lifts are then tied together with a structural facing (usually shotcrete) . The wall lifts are constructed incrementally from the top of cut down. Soil nail walls are being recognized as having potential for large cost savings over other alternatives. The increasing need to provide high capacity roadways in restricted rights of way under structures such as bridges will require increasing use of techniques such as combined soil nail and piling walls. The Swift Delta Soil Nail wall required installing nails between some of the existing pipe piling on the Oregon Slough Bridge. This raised questions of whether the piling would undergo internal stress changes due to the nail wall construction. Thus, it was considered necessary to understand the soil nail wall structure interaction in relation to the existing pile supported abutment. The purpose of this study was to investigate the Swift Delta Wall using finite element (FE) modeling techniques. Valuable data were available from the instrumentation of the swift Delta Wall. These data were compared with the results of the FE modeling. This study attempts to answer the following two questions: 1. Is there potential for the introduction of new bending stresses to the existing piling? 2. Is the soil nail wall system influenced by the presence of the piling? A general purpose FE code called ABAQUS was used to perform both linear and non-linear analyses. The analyses showed that the piling definitely underwent some stress changes. In addition they also indicated that piling influence resulted in lower nail stresses. Comparison of measured data to predicted behavior showed good agreement in wall face deflection but inconsistent agreement in nail stresses. This demonstrated the difficulty of modeling a soil nail due to the many variables resulting from nail installation.
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Courard, Amaury. "PGD-Abaques virtuels pour l'optimisation géométrique des structures." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLN010/document.
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Lors de l'optimisation géométrique de structures, un grand nombre d'évaluations de champs est nécessaire. L'idée, développée dans cette thèse, est la construction efficace et rapide d'approximations de ces champs à travers la Proper Generalized Decomposition (PGD), une méthode de réduction de modèle. Les résultats, calculés une fois pour toutes, sont stockés dans des abaques virtuels pour une utilisation ultérieure dans un processus d'optimisation. Le problème considéré est paramétrique et les paramètres définissent la géométrie. Ce type de problème est particulièrement adapté à la PGD. En effet, de nombreux travaux ont traité de la résolution de problèmes paramétriques et des premières études ont porté, en particulier, sur la prise en compte de paramètres géométriques. Toutefois, ce qui caractérise nos travaux est d'aller vers des outils aptes à traiter des situations significatives de la complexité des problèmes rencontrés au niveau industriel. En particulier, l'exploitation de codes éléments finis commerciaux est une contrainte majeure. Il a été décidé de développer des méthodes permettant de traiter des problèmes à paramètres géométriques par la PGD, et, en partenariat avec AIRBUS Defence & Space, d'appliquer ces techniques à un démonstrateur industriel présentant une géométrie complexe (type splines) et de fortes non-linéarités (géométriques, matériaux). Notre démarche a été implémentée dans un process industriel utilisant des codes éléments finis commerciaux. On propose aussi une nouvelle extension de la PGD aux paramètres discrets autorisant la prise en considération, dans une même résolution, de configurations de structures complètement différentes (cas de chargement, matériaux, etc.)During shape optimisation of structures, numerous evaluations of fiels are necessary. The idea, developed in this PhD thesis, is the efficient construction of approximations of these fiels through the Proper Generalized Decomposition (PGD), a model reduction technique. The results, computed once and for all, are stored in virtual charts for a subsequent use into an optimisation process. Geometry variations correspond to a parametric problem, where the parameters is the geometry. This kind of problem is well suited for PGD. Many studies dealt with the resolution of parametric problems and recent works treated, particularly, the introduction of geometric parameters. However, our approach is to deal with configurations of the complexity of industrial problems. The use of commercial finite elements software is a crucial issue. It was decided, in partnership with AIRBUS Defence & Space, to develop techniques allowing the resolution of geometrically parametrised problems thanks to PGD and to apply them to an industrial demonstrator. The geometry considered is defined by splines and the behaviour of the structure is highly non-linear (geometric and material non-linearities). The approach was implemented into a genuine industrial design process using commercial finite elements software. The thesis proposed, also, a new extension of PGD to discrete parameters. It allows to take into account completely different configurations (loadings, materials, etc.) in the same resolution
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Amini, Khoiy Keyvan. "Biomechanical Characterization and Simulation of the Tricuspid Valve." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1542651986497595.
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Bonorchis, Dean. "Implementation of material models for high strain rate applications as user-subroutines in abaqus/explicit." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/17954.
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Includes bibliographical references.The general purpose finite element program, Abaqus, has the facility to allow users to supplement its existing material model library with user-defined material models (VUMATs). This thesis involves the implementation and verification of the Johnson-Cook and Zerilli-Armstrong material models as VUMATs. The same version of the Johnson-Cook material model is contained in Abaqus and was therefore used as a benchmark. These material models are suitable for high strain, high strain rate and high temperature applications. The implementation of the material models was verified by comparing simulation results obtained using the Abaqus version of the Johnson-Cook material model with the simulation results obtained using the VUMATs of the Johnson-Cook and Zerilli-Armstrong material models. Firstly, this verification process was followed using single and multiple element tests with varying prescribed loading conditions. The verification process was then extended by performing a more "realistic" set of Taylor test simulations. The Taylor test simulation results were also compared with published experimental results for validation purposes.
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Jakel, Roland. "Lineare und nichtlineare Analyse hochdynamischer Einschlagvorgänge mit Creo Simulate und Abaqus/Explicit." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-171812.
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Der Vortrag beschreibt wie sich mittels der unterschiedlichen Berechnungsverfahren zur Lösung dynamischer Strukturpobleme der Einschlag eines idealisierten Bruchstücks in eine Schutzwand berechnen lässt. Dies wird mittels zweier kommerzieller FEM-Programme beschrieben: a.) Creo Simulate nutzt zur Lösung die Methode der modalen Superposition, d.h., es können nur lineare dynamische Systeme mit rein modaler Dämpfung berechnet werden. Kontakt zwischen zwei Bauteilen lässt sich damit nicht erfassen. Die unbekannte Kraft-Zeit-Funktion des Einschlagvorganges muss also geeignet abgeschätzt und als äußere Last auf die Schutzwand aufgebracht werden. Je dynamischer der Einschlagvorgang, desto eher wird der Gültigkeitsbereich des zugrunde liegenden linearen Modells verlassen. b.) Abaqus/Explicit nutzt ein direktes Zeitintegrationsverfahren zur schrittweisen Lösung der zugrunde liegenden Differentialgleichung, die keine tangentiale Steifigkeitsmatrix benötigt. Damit können sowohl Materialnichtlinearitäten als auch Kontakt geeignet erfasst und damit die Kraft-Zeit-Funktion des Einschlages ermittelt werden. Auch bei extrem hochdynamischen Vorgängen liefert diese Methode ein gutes Ergebnis. Es müssen dafür jedoch weit mehr Werkstoffdaten bekannt sein, um das nichtlineare elasto-plastische Materialverhalten mit Schädigungseffekten korrekt zu beschreiben. Die Schwierigkeiten der Werkstoffdatenbestimmung werden in den Grundlagen erläutertThe presentation describes how to analyze the impact of an idealized fragment into a stell protective panel with different dynamic analysis methods. Two different commercial Finite Element codes are used for this: a.) Creo Simulate: This code uses the method of modal superposition for analyzing the dynamic response of linear dynamic systems. Therefore, only modal damping and no contact can be used. The unknown force-vs.-time curve of the impact event cannot be computed, but must be assumed and applied as external force to the steel protective panel. As more dynamic the impact, as sooner the range of validity of the underlying linear model is left. b.) Abaqus/Explicit: This code uses a direct integration method for an incremental (step by step) solution of the underlying differential equation, which does not need a tangential stiffness matrix. In this way, matieral nonlinearities as well as contact can be obtained as one result of the FEM analysis. Even for extremely high-dynamic impacts, good results can be obtained. But, the nonlinear elasto-plastic material behavior with damage initiation and damage evolution must be characterized with a lot of effort. The principal difficulties of the material characterization are described
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Montero, Pich Òscar. "Normativització a la presó model de Barcelona abans de 1936." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/283889.
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El present estudi analitza el procés de normativització entès com una sèrie d’activitats que cercaven sondejar l’interior del presoner amb la finalitat de corregir el pensament i el comportament del reclús. Aquesta investigació s’ha circumscrit a la Presó Model de Barcelona abans de 1936.
Un dels propòsits de la investigació s’ha centrat en l’observació d’unes activitats i d’uns plantejaments teòrics per part d’uns agents amb la intenció de desenvolupar un procés normativitzador. Així, la identificació dels agents correctors ha posat en relleu el paper dels patronats de presos, del metge antropòmetre de la presó Model, Joan Soler i Roig, i del psicòleg català Joaquim Fuster (1901-1985). Tots tres agents intentaren explorar, per diferents vies, la moral del delinqüent.
D’altres agents, promotors de la construcció de la Model com Pere Armengol (1837-1896) o Ramon Albó (1872-1955), han permès entendre i estudiar la planificació de la presó Model des del correccionalisme. Des de la seva anàlisi s’han pogut examinar els orígens de la presó Model, la seva planificació arquitectònica, el sistema penitenciari i la seva regulació a través de la gestió quotidiana del presoner, encaminat tot plegat a reduir la reincidència.
L’estratègia d’intervenció cap als presoners per part dels agents ha servit, a més, per provar l’existència d’una tecnologia psicològica que anava dirigida a explorar el pensament del reu. És doncs a partir de la revisió d’aquesta tecnologia psicològica que hem pogut analitzar els tests psicològics realitzats per Fuster que mesuraven la moral delictual, o les entrevistes dels patronats de presos que cercaven modificar o guiar el comportament dels presoners.
D’altra banda, la presència a la Model d’anarquistes, comunistes i transsexuals fomentà una sèrie de registres documentals que hem recollit dins de l’àmbit de la normativització sexual i política. Aquests registres han permès constatar la visió que tenien alguns dels presoners, desenvolupant discursos propis en alguns àmbits, i la resistència que oposaren a la normativització a través de l’exercici del nudisme, de crítiques contra la gestió penitenciària als diaris o fomentant motins dins de la presó.This study examines the standardization process understood as a series of activities that sought to explore the mind of the prisoner in order to correct his thinking and behavior. The research has been confined to the prison “Model” of Barcelona, studied in the period before 1936. One aim of the research was to observe the series of activities pursued by some agents with influence on the standardizing process. In identifying the actors, the study highlights the role of the prison boards, the physician and prison anthropometrist Joan Soler I Roig, and the Catalan psychologist Joaquim Fuster (1901-1985). All three explore the morality of the delinquent, albeit from different points of view. Other professionals and promoters of the prison, such as Pere Armengol (1837-1896) or Ramon Albó (1872-1955) turned out to be instrumental in the study of the prison’s planning and design from a correctionalist perspective. Both, its origins and its architecture have been linked to the management of the prisoners, the daily life and the prison system itself, aimed at reducing the cases of repeat defence. The intervention strategy used by the agents towards prisoners revealed the existence of a psychological technology, developed to empower the first of exploring the thinking of the latter. By examining this psychological technology we were able to analyze the interviews done by the trustees who sought to modify or guide the prisoner’s behavior and the psychological tests carried out by Fuster, which measured the delinquent morality. Moreover, the presence of anarchists, communists and transsexuals in the “Model” prison led to the production of a series of documentary records, which have been included when dealing with standardization in the field of sexuality and politics. These documents allowed us to show the vision that some prisoners had, developing their own thinking in some areas, and the resistance they exerted towards standardization by practicing nudism, criticism against prison management in newspapers and by encouraging riots inside the prison.
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Bressan, Caroline Zanini. "Estudo numérico dos ensaios de tração simples e flexão de três pontos do aço livre de interstícios (IF) utilizando o modelo de Gurson modificado." Universidade do Estado de Santa Catarina, 2015. http://tede.udesc.br/handle/handle/2066.
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Numerical methods have received a substantial attention from Engineering Professionals especially due their capacity to provide solutions for a wide range of problems in many areas. In the last years, numerical simulation has become increasingly common and has turned into a key factor for solving numerous engineering problems in the industry as well in academia. This, however, requires the development of suitable methodological strategies to determinate constitutive law able to best describe the material behavior in the simulation. The present work is inserted within the context of metal forming, aiming to simulate 2D and 3D geometrical models of the simple tensile test and three-point bending test of a notched plate, both using the material properties of an Interstitial Free Steel, IF. For both cases, it was used a modified Gurson model available in the ABAQUS ® software, which is based on the finite elements method. Numerical modelling of the elasto-plastic process used to simulate the three-point bending and simple tensile test was discretised using structured meshes with an appropriate refinement. The experimental results for tensile tests used smooth cylindrical specimens with dimensions defined according to ASTM E 8M-01. The three point bending test was qualitatively compared with the results reported by Mashayeshi, et al (MASHAYEKHI, ZIAEI-RAD, et al., 2005). The strain hardening law used in this work was the Holomon or modified Swift law coupled with the damage evolution of the Gurson s model. The geometrical models for the tensile specimens account for axisymmetry, so that only one-quarter part of the 2D and 3D specimens was modelled. An appropriate mesh refinement in the necking region was also adopted. The numerical simulation was able to predict with success the stress-strain curve behaviour of the IF steel comparing with the experimental results. Both 2D and 3D simulation results of the simple tensile test were very similar. The prediction of porosity evolution with the applied displacement was analysed and the results indicated that the necking region in the central zone of the specimen presented the largest micro-void concentration, as expected. For the three-point bending test of a notched plate, the simulation provided a good qualitative agreement with the Mashayekhi´s numerical results, which have shown that the largest concentration of micro-voids was in the central region of the notch where the crack initiation occurs.
Métodos numéricos tem recebido uma grande atenção dos profissionais da área da engenharia em especial principalmente pelo seu caráter facilitador na solução de problemas em diversas áreas. Nos últimos tempos, a simulação numérica está se tornando cada vez mais comum e se transformando em uma peça chave para a resolução de inúmeros problemas de engenharia encontrados tanto nas indústrias quanto nas linhas de pesquisa científica das universidades. Isso, porém, exige desenvolvimento de estratégias de metodologias científicas adequadas o suficiente para determinar as leis que descrevam melhor o comportamento dos materiais a serem simulados. O presente trabalho está inserido no contexto da conformação de metais, tendo por objetivo simular, com malhas tipo 2D e 3D, os ensaios de tração simples e de flexão de três pontos de uma placa com entalhe de um aço livre de interstícios, aço IF (interstitial free steel), utilizando o modelo de Gurson modificado no programa ABAQUS ®, que utiliza o Método dos Elementos Finitos. Para o modelamento numérico do processo de deformação elasto-plástica dos ensaios de tração simples e flexão foi utilizada a lei de Gurson modificado de materiais porosos e uma malha com refinamento adequado. Os corpos de prova ensaiados experimentalmente em tração simples foram de aço IF cilíndricos preparados de acordo com a norma ASTM E 8M-01. Já o ensaio de flexão de três pontos foi simulado com o intuito de fazer uma comparação qualitativa com o resultado apresentado por Mashayekhi, Ziaei-Rad, et al. (MASHAYEKHI, ZIAEI-RAD, et al., 2005). A lei de encruamento plástico utilizada neste trabalho foi a Lei de Holomon ou Swift modificado acoplado com o modelo de evolução do dano de Gurson modificado. Após a escolha da geometria de somente quarta parte do corpo de prova, devido à simetria axissimétrica e do refinamento adequado da malha na região da estricção local, a simulação numérica foi capaz de prever com sucesso o comportamento da curva de tensãodeformação do aço IF comparando-se com os resultados experimentais. Os resultados da simulação 2D e 3D do ensaio de tração simples foram iguais. Portanto, a simulação 2D do ensaio de tração simples é mais conveniente pois é mais rápida e igualmente precisa que a simulação 3D para o presente caso de material dúctil e isotrópico. A previsão da evolução da porosidade com a deformação e a região de maior concentração de vazios foi analisada: ocorreu na região da estricção local e na zona central do corpo de prova como esperado. No caso do ensaio de flexão da placa com entalhe central, os resultados da simulação numérica mostraram uma boa concordância com os resultados de Mashayekhi, Ziaei-Rad et al. (2005), que apresentaram a maior concentração de vazios na região central do entalhe onde ocorrerá o aparecimento de trincas.
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Hahnel, Christopher. "Analysis of Bolted Top and Seat Angle Connection Failure Modes & Fracture Prediction." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447688781.
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Oliveira, Evelyn Aparecida de. "Modelos computacionais para análise da influência de parâmetros estatísticos de textura superficial no contato dentário humano." Universidade Federal de Juiz de Fora (UFJF), 2016. https://repositorio.ufjf.br/jspui/handle/ufjf/3297.
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O desgaste do dente, que se manifesta com uma grande variedade de graus ou níveis, é uma das anomalias dentárias comumente encontradas em diversas populações. A modelagem computacional do problema de contato oclusal pode ajudar na compreensão das interações entre os dentes, que gera concentrações de tensões. A abordagem utilizada para simular o contato entre as superfícies ásperas, dadas as funções de densidade de probabilidade das alturas das asperezas, consiste em discretizá-las em vários intervalos, de modo que cada um deles represente uma aspereza principal. As deformações das asperezas principais são analisadas e, utilizando técnicas de homogeneização, é possível estabelecer a relação entre as respostas que ocorrem em microescala e as respostas esperadas na macroescala. Neste trabalho, foi criada uma rotina para geração numérica de superfícies, um script acoplado ao programa de elementos finitos, Abaqus, para análise dos microcontatos, e, finalmente, um código para o procedimento de homogeneização e análise paramétrica das medidas de rugosidade. Na estimativa da dureza superficial, verificou-se que a curvatura média das asperezas exerce maior influência. Os parâmetros que mais influenciam nas forças e áreas de contato são o coeficiente de achatamento (kurtosis), cujo aumento leva ao decaimento dessas grandezas, seguido da rugosidade média quadrática, que, por sua vez, tem uma relação diretamente proporcional com a carga e consequentemente com a área de contato.
Tooth wear, which manifests with a great variety of degrees or levels, is one of the dental abnormalities commonly found in different populations. The computational modelling of the occlusal contact problem can help the comprehension of any interaction between teeth generating stress concentration. The approach used in this work to simulate contact between rough surfaces, given the probability density functions of asperities, consists in discretizing them in several intervals, so that each one represents a main asperity. The deformations of the main asperities are analyzed and, using homogenization techniques, it is possible to developed the relationship among the responses occurred in micro-scale and the predicted responses in macro-scale. In this work a routine has been established for numerical generation of surfaces, a script as well as has been coupled to the finite element program Abaqus, for analysis of the micro-contacts, and, finally, a code for homogenization and parametric analysis of the roughness measure. In the estimate of the surface hardness it was found that the mean curvature of the asperities exerts the largest influence. The parameters that influence the forces and contact areas are the flattening coefficient (kurtosis), which when increases leads to decay of these greatness, followed by the mean square roughness, which, in turn, has a direct proportional relationship with the strength and consequently with the contact area.
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Parimi, Venkata Naga Sai Krishna Janardhan, and Vamsi Eluri. "Stress Analysis of Different Shaped Holes on a Packaging Material." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13613.
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In packaging industries, the demand for usage of Low Density Poly Ethylene foil is of profound interest. In the past, research was carried out on finite and infinite plates with varying crack lengths but having constant crack width. In this thesis, a detailed analysis on crack initiation is carried out on finite plates by varying width of the hole. The hole shapes for stress analysis include circle, ellipse and rectangular notch. Initially, maximum stress is found out using Linear Elastic Fracture Mechanics (LEFM) theory and compared with Finite element method (FEM) results. Secondly using Elastic Plastic Fracture Mechanics theory (EPFM), critical stress and geometric function are evaluated theoretically by Modified Strip Yield Model (MSYM) and numerically by ABAQUS. Finally, a tensile test is conducted to validate the theoretical and numerical results. By varying the width of the hole, a study on the parameters like critical stress, geometric function is presented. A conclusion is drawn that the effect of hole width should be considered when calculating fracture parameters.
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Chen, Yifu. "L'étude des différents modes de déplacement des boules du boulier et de l'invention de la méthode de multiplication Kongpan Qianchengfa et son lien avec le calcul mental." Paris 7, 2013. http://www.theses.fr/2013PA070061.
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L'objet de ce travail est, d'une part, de mettre en évidence les différents modes de déplacement des boules du boulier dans les documents publiés en Chine sous les Ming et les Qing, et au Japon à l'époque d'Edo. Il est, d'autre part, de rechercher l'origine possible de l'idée qui a permis l'invention de la méthode de multiplication Kongpan qiancheng, effectuée à l'aide du boulier. Concernant l'étude des modes de déplacement des boules du boulier, nous avons établi une méthode insistant sur le contexte du déplacement des boules du boulier dans les opérations, ce qui nous a amené à procéder l'étude systématique des différents modes de déplacement des boules. Nous avons pu ainsi constater qu'il existait, pour l'exécution des opérations d'addition, quatre différents modes de déplacement des boules, et deux modes différents pour celle des opérations de soustraction. Nous avons pu distinguer également deux styles de déplacement des boules : l'un consistant à privilégier l'habileté et la commodité dans le déplacement des boules ; et l'autre une certaine uniformité du mode opératoire. Dans la recherche de l'origine des conditions d'invention de la méthode de multiplication Kongpan qiancheng, nous avons pu démontrer, en nous appuyant sur la comparaison des méthodes et technique utilisées dans l'usage du boulier et celles relatives au calcul mental, que les deux particularités capitales, propres à la méthode Kongpan qiancheng, se retrouvaient dans la méthode du calcul mental. Nous avons été conduit, de ce fait, à avancer l'hypothèse que l'invention de la méthode Kongpan qiancheng avait pu être inspirée de celle du calcul mental. Au terme de cette investigation, un éclairage inédit est donc apparu sur les relations qui existent entre les méthodes employées dans la pratique du boulier et celles utilisées pour calcul mental : ainsi, l'invention d'une nouvelle procédure pourrait-elle naître dans le domaine du calcul mental, puis s'être appliquée à la pratique du calcul à l'aide du boulier. Nous avons pu montrer, en outre, que la technique du calcul mental appliquée à la méthode Kongpan qiancheng, était liée à la combinaison de deux systèmes - le boulier et les chiffres arabes, et au mode d'expression mathématique occidentale dans l'organisation du travail pour les opérations de calcul. Il semble donc que ces deux facteurs aient pu jouer un rôle important dans l'invention de la technique préconisée dans la méthode Kongpan qiancheng, cette dernière ayant été, en cela, le fruit de la rencontre de deux cultures distinctesThe purpose of this dissertation is to study, on the one hand, the different modes of moving the beads of abacus employed in the works published in the Ming and Qing dynasty in China and those in the Edo period in Japan. It is, on the other hand, to research the possible origin of invention of the method of multiplication Kongpan qiancheng performed with the abacus. On the subject of the study of different modes of moving the beads of abacus, we propose a method, based on the analysis of the context of movement of the beads in the execution of operations, for recognition of different modes. We show that four different modes of moving the beads of abacus existed in the operations of addition and two different modes in those of subtraction. Two styles of moving the beads of abacus can be thus recognized : one addressing the dexterity and the convenience for moving the beads, the other the consistency in the movement of the beads. In the investigation of the possible origin of invention of the method of multiplication Kongpan qiancheng, a comparative approach that examines the methods and techniques employed in the computation performed with the abacus and those in the mental computation is conducted. We show that two crucial characteristics of the method Kongpan qiancheng can be found in a method of mental computation existed earlier. This result helps us to draw a hypothesis that the method of mental computation could be the possible origin of invention of the method Kongpan qiancheng. It sheds then some light on an overlooked relationship between the methods of the computation performed with the abacus and those in the mental computation : a new method could be invented for the mental computation, then applied to the computation performed with the abacus. We also show that the technique of the mental computation applied to the method Kongpan qiancheng is related to the combined use of modern Western numerical notation and expression and the methods of operation with the abacus. The method Kongpan qiancheng could be therefore the product of the interaction of two distinct cultures
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Rolseth, Anton, and Anton Gustafsson. "Implementation of thermomechanical laser welding simulation : Predicting displacements of fusing A AISI304 T-JOINT." Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-19946.
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Laser welding is an advanced joining technique with the capability to form deep, narrow, and precise welds. Numerical models are used to simulate the process in attempts of predicting distortions and stresses in the material. This is done to reduce physical testing, optimize processes and enable integrated product- and process development. The Virtual Manufacturing Process research group at University of Skövde wishes to increase their knowledge on modeling options of thermomechanical simulations to grant local industries these benefits. A numerical model for the laser welding process was developed in ABAQUS. This was done by examining the macrograph structure of a simple weld and applied to a stainless-steel T-joint welding application. The macrograph data was used to calibrate a mathematical heat source model. User subroutine DFLUX was used to enable movement of the heat source and element activation was used to simulate the fusion of the two parts. A T-joint welding experiment was carried out to measure deflection and the result was compared to numerical simulations. Different combinations of heat source models, coupling type and element activation was compared in relation to predicting the deflection. Computational time and modeling complexity for the techniques was also considered.The results showed that a 3D Gaussian heat source model will imitate the keyhole weld achieved superior to the compared 2D model. The 3D model provides greater flexibility since it enables combinations of any geometrical bodies. It was shown that element activation has a significant contribution on part stiffness and thus resulting distortions. To implement element activation a fully coupled analysis is required. The deflection of the fully coupled 3D simulation with element activation showed a 9% deviance in deflection compared with experiments.
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Scalone, Santiago Andres. "A numerical evaluation of mode I & II damage propagation in composite materials." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15914/.
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A full numerical evaluation using Abaqus has been done for 2D and 3D Mode I and II delamination propagation (in composite materials). First the theory to explain all the mechanisms that are involved in delamination growth were developed, also the theory that Abaqus uses to solve the delamination process was explained. Furthermore, all the values that have been used were explained in detail, these values are difficult to find. Then, the results were obtained combining the delamination theory with Matlab. The parameters that have been analyzed are: critical strain energy release rate, the most relevant stresses around the delamination and the shape of the delamination tip. The numerical results are in accordance with the experimental results, thus, the simulations are able to predict the delamination growth.
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Seon, Guillaume. "Finite element-based failure models for carbon/epoxy tape composites." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28117.
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Lu, Ye. "Construction d’abaques numériques dédiés aux études paramétriques du procédé de soudage par des méthodes de réduction de modèles espace-temps." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI103/document.
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Le recours à des simulations numériques pour l’étude de l’influence des paramètres d’entrée (matériaux, chargements, conditions aux limites, géométrie, etc.) sur les différentes quantités d’intérêt en soudage (contraintes résiduelles, distorsion, etc.) s’avère trop long et coûteux vu l’aspect multi-paramétrique de ces simulations. Pour explorer des espaces paramétriques de grandes dimensions, avec des calculs moins coûteux, il parait opportun d’utiliser des approches de réduction de modèle. Dans ce travail, d’une façon a posteriori, une stratégie non-intrusive est développée pour construire les abaques dédiées aux études paramétriques du soudage. Dans une phase offline, une base de données (‘snapshots’) a été pré-calculée avec un choix optimal des paramètres d'entrée donnés par une approche multi-grille (dans l’espace des paramètres). Pour explorer d’autres valeurs de paramètres, une méthode d’interpolation basée sur la variété Grassmannienne est alors proposée pour adapter les bases réduites espace-temps issues de la méthode SVD. Cette méthode a été constatée plus performante que les méthodes d’interpolation standards, notamment en non-linéaire. Afin d’explorer des espaces paramétriques de grandes dimensions, une méthode de type décomposition tensorielle (i.e. HOPGD) a été également étudiée. Pour l’aspect d’optimalité de l’abaque, nous proposons une technique d’accélération de convergence pour la HOPGD et une approche ‘sparse grids’ qui permet d’échantillonner efficacement l’espace des paramètres. Finalement, les abaques optimaux de dimension jusqu’à 10 à précision contrôlée ont été construits pour différents types de paramètres (matériaux, chargements, géométrie) du procédé de soudageThe use of standard numerical simulations for studies of the influence of input parameters (materials, loading, boundary conditions, geometry, etc.) on the quantities of interest in welding (residual stresses, distortion, etc.) proves to be too long and costly due to the multiparametric aspect of welding. In order to explore high-dimensional parametric spaces, with cheaper calculations, it seems to be appropriate to use model reduction approaches. In this work, in an a posteriori way, a non-intrusive strategy is developed to construct computational vademecum dedicated to parametric studies of welding. In an offline phase, a snapshots database is pre-computed with an optimal choice of input parameters given by a “multi-grids” approach (in parameter space). To explore other parameter values, an interpolation method based on Grassmann manifolds is proposed to adapt both the space and time reduced bases derived from the SVD. This method seems more efficient than standard interpolation methods, especially in non-linear cases. In order to explore highdimensional parametric spaces, a tensor decomposition method (i.e. HOPGD) has also been studied. For the optimality aspect of the computational vademecum, we propose a convergence acceleration technique for HOPGD and a “sparse grids” approach which allows efficient sampling of the parameter space. Finally, computational vademecums of dimension up to 10 with controlled accuracy have been constructed for different types of welding parameters (materials, loading, geometry)
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Plaza, Floren. "Measuring, modelling and understanding the mechanical behavior of bagasse." Thesis, University of Southern Queensland, 2003. https://eprints.qut.edu.au/74742/1/Thesis_bagasse_mechanical_behaviour.pdf.
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In the Australian sugar industry, sugar cane is smashed into a straw like material by hammers before being squeezed between large rollers to extract the sugar juice.
The straw like material is initially called prepared cane and then bagasse as it passes through successive roller milling units. The sugar cane materials are highly
compressible, have high moisture content, are fibrous, and they resemble some peat soils in both appearance and mechanical behaviour. A promising avenue to improve the performance of milling units for increased throughput and juice extraction, and to reduce costs is by modelling of the crushing process. To achieve this, it is believed necessary that milling models should be able to reproduce measured bagasse behaviour. This investigation sought to measure the mechanical (compression, shear, and volume) behaviour of prepared cane and bagasse, to identify limitations in currently used material models, and to progress towards a material model that can predict
bagasse behaviour adequately. Tests were carried out using a modified direct shear test equipment and procedure at
most of the large range of pressures occurring in the crushing process. The investigation included an assessment of the performance of the direct shear test for measuring bagasse behaviour. The assessment was carried out using finite element modelling. It was shown that prepared cane and bagasse exhibited critical state behavior similar to that of soils and the magnitudes of material parameters were determined. The measurements were used to identify desirable features for a bagasse material model. It was shown that currently used material models had major limitations for reproducing bagasse behaviour. A model from the soil mechanics literature was modified and shown to achieve improved reproduction while using magnitudes of
material parameters that better reflected the measured values. Finally, a typical three roller mill pressure feeder configuration was modelled. The predictions and
limitations were assessed by comparison to measured data from a sugar factory.
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Kesawan, Sivakumar. "Fire performance and design of light gauge steel frame wall systems made of hollow flange sections." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/120153/1/Kesawan_Sivakumar_Thesis.pdf.
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Load bearing Light Gauge Steel Frame (LSF) wall system is a cold-formed steel structure made of cold-formed steel studs and lined on both sides by gypsum plasterboards. In recent times its use and demand in the building industry has significantly increased due to their advantages such as light weight, acoustic performance, aesthetic quality of finished wall, ease of fabrication and rapid constructability. Fire Resistant Rating (FRR) of these walls is given more attention due to the increasing number and severity of fire related accidents in residential buildings that have caused significant loss of lives and properties.
LSF walls are commonly made of conventional lipped channel section studs lined with fire resistant gypsum plasterboards on both sides. Recently, greater attention has been given to innovative cold-formed steel sections such as hollow flange sections due to their improved structural efficiency. The reliance on expensive and time consuming full scale fire tests, and the complexity involved in predicting the fire performance of LSF wall studs due to their thin-walled nature and their exposure to non-uniform temperature distributions in fire on one side, have been the main barriers in using different cold-formed steel stud sections in LSF wall systems. This research overcomes this and proposes the new hollow flange section studs as vertical load bearing elements in LSF wall systems based on a thorough investigation into their fire (structural and thermal) performance using full scale fire tests and extensive numerical studies.
Test wall frames made of hollow flange section studs were lined with fire resistant gypsum plasterboards on both sides, and were subjected to increasing temperatures as given by the standard fire curve in AS 1530.4 (SA, 2005) on one side. Both uninsulated and cavity insulated walls were tested with varying load ratios from 0.2 to 0.6. LiteSteel Beam (LSB), a welded hollow flange section, which was available in the industry was used to fabricate the test wall panels. Axial deformations and lateral displacements along with the time-temperature profiles of the steel stud and plasterboard surfaces were measured. Five full scale tests were performed, and the test results were compared with those of LSF walls made of lipped channel section studs, which proved the superior fire performance of LSF walls made of hollow flange section studs. The reasons for the superior fire performance are presented in this thesis. The effects of load ratio and plasterboard joint on the fire performance of LSF walls and temperature distribution across the stud cross-sections were identified.
Improved plasterboard joints were also proposed.
The elevated temperature mechanical properties of cold-formed steels appear to vary significantly as shown by past research. LSBs were manufactured using a combined cold-forming and electric resistance welding process. Elevated temperature mechanical properties of LSB plate elements are unknown. Therefore an experimental study was undertaken to determine the elevated temperature mechanical properties of LSB plate elements. Based on the test results and previous researchers' proposed values, suitable predictive equations were proposed for the elastic modulus and yield strength reduction factors and stress-strain models of LSB web and flange elements.
Uninsulated and insulated 2D finite element models of LSF walls were developed in SAFIR using GiD as a pre- and post processor to predict the thermal performance under fire conditions. A new set of apparent thermal conductivity values was proposed for gypsum plasterboards for this purpose. These models were then validated by comparing the time-temperature profiles of stud and plasterboard surfaces with corresponding experimental results. The developed models were then used to conduct an extensive parametric study. Uninsulated and insulated LSF walls with superior fire performances were also proposed.
Finite element models of tested walls were also developed and analysed under both transient and steady state conditions to predict the structural performance under fire conditions using ABAQUS. In these analyses, the measured elevated temperature properties of LSB plate elements were used to improve their accuracy. Finite element analysis results were compared with fire test results to validate the developed models. Following this, a detailed finite element analysis based study was conducted to investigate the effects of stud dimensions such as web depths and thicknesses, elevated temperature mechanical properties, types of wall configurations, stud section profiles, plasterboards to stud connections and realistic design fire curves on the fire performance of LSF walls. It was also shown that the commonly used critical temperature method is not appropriate in determining the FRR of LSF walls.
Gunalan and Mahendran's (2013) design rules based on AS/NZS 4600 (SA, 2005), and Eurocode 3 Part 1.3 (ECS, 2006) were further improved to predict the structural capacity of hollow flange section studs subjected to non-uniform temperature distributions caused by fire on one side. Two improved methods were proposed and they predicted the FRRs with a reasonable accuracy. Direct Strength Method (DSM) based design rules were then established and they also predicted the FRR of LSF walls made of hollow flange section studs accurately. Finally, spread sheet based design tools were developed based on the proposed design rules.
Overall, this research has developed comprehensive fire performance data of LSF walls made of hollow flange section studs, accurate design rules to predict their fire rating and associated design tools. Thus it has enabled the use of innovative hollow flange sections as studs in LSF wall systems. Structural and fire engineers can now use these tools to undertake complex calculations of determining the structural capacities and fire rating of hollow flange section studs subjected to non-uniform temperature distributions, and successfully design them for safe and efficient use in LSF walls of residential and office buildings.
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Fardmoshiri, Mohamad. "Advances in Hopkinson bar tests: calibration of constitutive models at high strain rate using finite element method updating and image processing." Doctoral thesis, Università Politecnica delle Marche, 2016. http://hdl.handle.net/11566/243086.
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Questa tesi concerne lo sviluppo di un sistema di processamento di dati fisici e sperimentali per test ad elevata velocità di deformazione tramite la barra di Hopkinson. La barra di Hopkison è la tipologia di test più utilizzata comunemente per svolgere test dinamici, determinando le proprietà dei materiali caratterizzandone la risposta dinamica ad elevate velocità di deformazione. Utilizzando una barra di Hopkinson progettata e realizzata recentemente dal gruppo di costruzione di macchine della Università Politecnica delle Marche, dati sperimentali accurati e precisi cosi come immagini catturate ad alta velocità di provini in alluminio AA6061-T6 possono essere ottenuti in test svolti ad elevate velocità di deformazione. Provini di dimensioni diverse sia di trazione che di compressione dello stesso materiale sono stati utilizzati e i risultati analizzati col fine di calibrare le proprietà del materiale utilizzando il modello plastico constitutivo di Johnson-Cook. I coefficienti dei materiali secondo Johnson-Cook sono stati caratterizzati utilizzando approcci differenti.
Un primo approccio coinvolge il cosiddetto metodo FEMU (Finite Element Method Updating) dove simulazioni numeriche sono ripetute cambiando di volta in volta i parametri del materiale sino a che la deviazione sperimentale e numerica non scenda sotto una soglia ritenuta accettabile.
Il secondo metodo, denominato FastCAM, si basa sulla analisi digitale delle immagini ottenute grazie ad una camera con alto rateo di acquisizione immagini ottenute durante il test e calibrando il modello di Johnson-Cook con minimizzazioni analitiche senza la necessità di simulazioni ad elementi finiti.
Inoltre, una terza tecnica inversa è stata implementata, la quale consiste nell'applicare il FEMU ma utilizzando una funzione di costo dove anche una differenza tra i profili dei provini numerici
e quelli ottenuti sperimentalmente è considerata e minimizzata.
In aggiunta, due provini in acciaio con una ben definita composizione (ottenuta da un centro di ricerca) sono stati testati. Per concludere, i vantaggi e svantaggi delle diverse tecniche sono stati valutati e confrontati tra loro.This thesis work reports on a mainly accurate and precise physical and experimental data capture as well as data processing system for high strain rate tests using the split Hopkinson bar. The split Hopkinson bar is the most commonly used method of employing dynamic tests, determining material properties and characterize the dynamic response of materials at high strain rate. Using a recent well equipped split Hopkinson bar developed by mechanical engineering design department of Ancona University, accurate and precise experimental data as well as high-speed image capturing of aluminum alloy AA6061-T6 samples are obtained for high strain rate testing. Different sizes of tensile and compression samples of same material were used and data were studied in order to calibrate material properties using Johnson-Cook constitutive plasticity model. Johnson-Cook material coefficients have been characterized using different approaches. The first approach involves classical Finite Element Method Updating (FEMU) where numerical simulations are repeated with different material parameters until the deviation of experimental, as well as numerical data, falls below an acceptable threshold. The second method, commonly known as FastCAM, is based on the analysis of the digital images attained by a fast camera during the tests and calibrates the Johnson-Cook model by an analytical minimization procedure in the absent of FE simulation. Furthermore, the third inverse technique was also implemented, consisting of applying the FE model updating but using an enriched cost function, where also the mismatch between the numerical and acquired specimen shape profiles is included and minimized. Furthermore, two additional steel based materials with confidential alloy composition (cast by a research center) are tested. To finalized, the advantages and drawbacks of the different techniques are assessed and compared.
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Susila, Gede Adi. "Experimental and numerical studies of masonry wall panels and timber frames of low-rise structures under seismic loadings in Indonesia." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/experimental-and-numerical-studies-of-masonry-wall-panels-and-timber-frames-of-lowrise-structures-under-seismic-loadings-in-indonesia(3ceb094b-4e6e-432a-b3de-3d4c306b0551).html.
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Indonesia is a developing country that suffers from earthquakes and windstorms and where at least 60% of houses are non-engineered structures, built by unskilled workers using masonry and timber. The non-engineered housing units developed in urban region are also vulnerable to seismic hazard due to the use of low quality of material and constructions method. Those structures are not resistant to extreme lateral loads or ground movement and their failure during an earthquake or storm can lead to significant loss of life. This thesis is concerned with the structural performance of Indonesian low-rise buildings made of masonry and timber under lateral seismic load. The research presented includes a survey of forms of building structure and experimental, analytical and numerical work to predict the behaviour of masonry wall and traditional timber frame buildings. Experimental testing of both masonry and timber have been carried out in Indonesia to establish the quality of materials and to provide material properties for numerical simulations. The experimental study found that the strength of Indonesia-Bali clay brick masonry are below the minimum standard required for masonry structures built in seismic regions, being at least 50% lower than the requirement specified in British Standard and Eurocode-6 (BS EN 1996-1-1:2005). In contrast, Indonesian timber materials meet the strength classes specified in British Standard/Eurocode- 5 (BS EN 338:2009) in the range of strength grade D35-40 and C35).Structural tests under monotonic and cyclic loading have been conducted on building components in Indonesia, to determine the load-displacement capacity of local hand-made masonry wall panels and timber frames in order to: (1) evaluate the performance of masonry and timber frame structure, (2) investigate the dynamic behaviour of both structures, (3) observe the effect of in-plane stiffness and ductility level, and (4) examine the anchoring joint at the base of timber frame that resists the overturning moment. From these tests, the structural ductility was found to be less than two which is below the requirement of the relevant guidelines from the Federal Emergency Management Agency, USA (FEMA-306). It was also observed that the lateral stiffness of masonry wall is much higher than the equivalent timber frame of the same height and length. The experimental value of stiffness of the masonry wall panel was found to be one-twelfth of the recommended values given in FEMA-356 and the Canadian Building code. The masonry wall provides relatively low displacement compared to the large displacement of the timber frame at the full capacity level of lateral load, with structural framing members of the latter remaining intact. The weak point of the timber frame is the mechanical joint and the capacity of slip joint governs the lateral load capacity of the whole frame. Detailed numerical models of the experimental specimens were setup in Abaqus using three-dimensional solid elements. Cohesive elements were used to simulate the mortar behaviour, exhibiting cracking and the associated physical separation of the elements. Appropriate contact definitions were used where relevant, especially for the timber frame joints. A range of available material plasticity models were reviewed: Drucker-Prager, Crystalline Plasticity, and Cohesive Damage model. It was found that the combination of Crystalline Plasticity model for the brick unit and timber, and the Cohesive Damage model for the mortar is capable of simulating the experimental load-displacement behaviour fairly accurately. The validated numerical models have been used to (1) predict the lateral load capacity, (2) determine the cracking load and patterns, (3) carry out a detailed parametric study by changing the geometric and material properties different to the experimental specimens. The numerical models were used to assess different strengthening measures such as using bamboo as reinforcement in the masonry walls for a complete single storey, and a two-storey houses including openings for doors and windows. The traditional footing of the timber structures was analysed using Abaqus and was found to be an excellent base isolation system which partly explains the survival of those structures in the past earthquakes. The experimental and numerical results have finally been used to develop a design guideline for new construction as well as recommendations for retrofitting of existing structures for improved performance under seismic lateral load.
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Canales, Aguilera Diego. "Stratégies numériques avancées pour la simulation efficace de procédés de soudage conventionnels et non conventionnels : Une approche de réduction de modèles." Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0012/document.
Full textAbstract:
Les simulations numériques représentent un outil fondamental pour la conception et l'optimisation de procédés industriels de fabrication tels que le soudage. Malgré le développement impressionnant des méthodes numériques et des moyens de calcul utilisables, la complexité des procédés de fabrication et les nouvelles exigences des industries les plus avancées obligent à repenser les méthodes, les stratégies et les algorithmes de simulation disponibles. Dans cette thèse, de nouvelles méthodes numériques avec une approche de Réduction des Modèles sont proposées, une discipline consolidée qui a fourni des solutions étonnantes dans différentes applications, comme les procédés de fabrication avancés. Tout d'abord, différentes stratégies sont proposées pour la simulation efficace des procédés de soudage conventionnel, à cet effet, l'utilisation de Computational Vademecums est introduite. L’introduction de ces abaques numériques améliorent des méthodes telles que : les Éléments Finis Généralisés pour le calcul thermique, l'approche local-global pour le calcul mécanique et enfin, la construction directe des abaques numériques utiles pour la phase de pré-design. En second lieu, un solveur PGD efficace est présenté pour les simulations thermo-mécaniques de soudage par friction-malaxage. Cette thèse montre comment la réduction des modèles,en plus d'être une fin en soi, peut être un excellent ingrédient pour améliorer l'efficacité des méthodes numériques traditionnelles. Cela représente un grand intérêt pour l'industrieNumerical simulations represent a fundamental tool for the design and optimization of industrial manufacturing processes such as welding. Despite the impressive development of the numerical methods and the means of calculation, the complexity of these processes and the new demands of the more advanced industries make it necessary to rethink the available methods, strategies and simulation algorithms. In this thesis, we propose new numerical methods with a Model Order Reduction approach, a consolidated discipline that has provided surprising solutions indifferent applications, such as advanced manufacturing processes. First, different strategies for the efficient simulation of conventional welding processes are proposed. To this end, the use of Computational Vademecums is introduced for the improvement of methods such as the Generalized Finite Element for thermal calculation, the local-global approach for the mechanical calculation or the direct construction of vademecums useful for predesign phases. Then, an efficient PGD solver for thermomechanical simulations for friction stir welding is presented. This thesis shows how Model Reduction, besides being an end, it can be an excellent ingredient to improve the efficiency of traditional numerical methods, with great interest for the industry
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Nogueira, Filho Ricardo. "Análise e controlo da rigidez de estruturas de prensas com tirantes pré-tensionados." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/18368.
Full textAbstract:
Mestrado em Engenharia MecânicaAs prensas são máquinas de conformação de chapa metálica capazes de elevada produtividade e qualidade de itens fabricados. Dado a intensidade de força exigida à estrutura resistente, o seu projeto deve observar o melhor equilíbrio de rigidez e massa investida, dado que a diminuição desta última pode levar a menor robustez do corpo da prensa. Há exigentes especificações referentes ao nível de deslocamentos e rotações decorrentes do esforço em trabalho. O uso de módulos ligados por tirantes permite não só menos complexidade no projeto dos elementos estruturais integrando o corpo principal, como também menor custo de transporte e instalação. Variando o pré-esforço assim como a flexibilidade tanto dos tirantes como das estruturas a ligar, é possível melhorar as características de resistência estrutural da prensa. Neste trabalho os principais objetivos são simular diferentes componentes de uma prensa, de forma a se obter conclusões relacionadas com o desenvolvimento de algumas das componentes constituintes, a distribuição de tensões nessas componentes, os deslocamentos máximos, as zonas criticas de cada componente, a rigidez de cada componente, número de ciclos até ocorrer fadiga de cada componente, e a análise dinâmica para a estrutura superior da prensa. Para se efetuar o trabalho utilizou-se softwares de simulação numérica CATIA e Abaqus. Utilizou-se modelos 3D apróximados a componentes reais, e modelos de malha o tanto mais refinada quanto possivel pelas versões dos softwares disponiveis (de forma a se obter resultados mais precisos). Teve-se em conta um tempo máximo para cada tentativa de simulação de 40 minutos, pois algumas simulações, mesmo aproveitando as simetrias do problema, tornavam-se demasiado exigentes para o hardware disponivel. Posto isto, utilizou-se modelos de malha refinada em função dessa margem temporal especificada. Os resultados representados nas figuras ao longo desta dissertação são somente aqueles que apresentaram valores lógicos, isto é, todas as tentativas falhadas (com erros) de simulação que eventualmente levaram à simulação correta com os resultados corretos não foram representadas neste documento.
Presses are sheet metal forming machines capable of manufacturing high quality products in high volumes rates. Taking in to account the stress level the press structure is subjected, its design should combine the best stiffness/mass balance invested, because the mass decrease can lead to lower the strength of the press frame and reduce its capacity to absorb and dissipate vibrations from impact loads. There are restrictive requirements, caused by the forces originated while the press is operating, regarding the level of displacements and rotations. The use of modules joined by tie rods allows not only for less complexity in the design of the structural elements integrating the main body, but also the lower cost of transportation and installation. By varying the prestressing as well as the flexibility of the rods and the connecting structures, it is possible to improve the structural strength characteristics of the press. With this work, the main objectives are to simulate different components of a press in order to draw conclusions related to the development of some of the constituent components the distribution of stresses in these components, the maximum displacement, each component’s critical zones, stiffness, number of cycles necessary to occur fatigue and a dynamic analysis for the upper press frame. In the development of this work, numerical simulation software CATIA and Abaqus-Simulia® were used. For better accuracy and precision, 3D models where considered in the structure spatial simulation with the two available software versions. Some simulations, even taking advantage of the symmetry conditions inherent to the problem, they represented a hard computational task to the available hardware. It was taken into account a maximum 40 minute time interval for each trial simulation. Refined mesh models were used. The results shown in the figures throughout this dissertation are only those with physically acceptable values.