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Dissertations / Theses on the topic 'Sheet metal forming'

Author: Grafiati
Published: 4 June 2021
Last updated: 8 June 2024

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1

Ali, Ahmed. "Incremental sheet metal forming." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0020/MQ54441.pdf.

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2

Gåård, Anders. "Wear in sheet metal forming." Licentiate thesis, Karlstad University, Faculty of Technology and Science, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1592.

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The general trend in the car body manufacturing industry is towards low-series production and reduction of press lubricants and car weight. The limited use of press lubricants, in combination with the introduction of high and ultra-high strength sheet materials, continuously increases the demands of the forming tools. To provide the means of forming new generations of sheet material, development of new tool materials with improved galling resistance is required, which may include tailored microstructures, introducing of specific(MC, M(C,N))carbides and nitrides, coatings and improved surface finish. In the present work, the wear mechanisms in real forming operations have been studied and emulated on a laboratory scale by developing a test equipment. The wear mechanisms identified in the real forming process, were distinguished into a sequence of events consisting of initial local adhesive wear of the sheets resulting in transfer of sheet material to the tool surfaces. Successive forming operations led to growth of the transfer layer and initiation of scratching of the sheets. Finally, scratching changed into severe adhesive wear, associated with gross macroscopic damage. The wear process was repeated in the laboratory test-equipment in sliding between several tool materials, ranging from cast iron to conventional ingot cast tool steels to advanced powder metallurgy tool steel, against dual-phase carbon steel sheets. By use of the test-equipment, selected tool materials were ranked regarding wear resistance in sliding against ferritic-martensitic steel sheets at different contact pressures.

Wear in sheet metal forming is mainly determined by adhesion; initially between the tool and sheet surface interaction and subsequently, after initiation of material transfer, between a sheet to sheet contact. Atomic force microscopy force curves showed that adhesion is sensitive to both chemical composition and temperature. By alloying of iron with 18wt.% Cr and 8wt.% Ni, alloying in itself, or changes in crystal structure, led to an increase of 3 times in adhesion at room temperature. Hence, alloying may be assumed a promising way for control of adhesive properties. Additionally, frictional heating should be controlled to avoid high adhesion as, generally, adhesion was found to increase with increasing temperature for all investigated materials.

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3

Gåård, Anders. "Wear in sheet metal forming /." Karlstad : Faculty of Technology and Science, Materials Engineering, Karlstad University, 2008. http://www.diva-portal.org/kau/abstract.xsql?dbid=1592.

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4

Carlsson, Per. "Surface Engineering in Sheet Metal Forming." Doctoral thesis, Uppsala University, Department of Materials Science, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4764.

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In recent years, surface engineering techniques have been developed in order to improve the tribological performance in many industrial applications. In sheet metal forming processes, the usage of liquid lubricants can be decreased by using self lubricated tribo surfaces which will result in more environmentally friendly workshops. In the present work two different concepts, i.e. the deposition of thin organic coatings on the steel sheet and PVD coatings on the tool, have been evaluated. The sheet materials investigated include Zn and 55%Al-Zn metal coated steel sheet, which in general are difficult materials to form under dry conditions since they are sticky and thus have a high tendency to adhere to the tool surface. The PVD coatings include CrN, TiN and various DLC coatings. The work comprises tribo testing and post test characterisation using surface analytical techniques in order to evaluate the tribological properties of the tribo surfaces. The tribological tests of different tribo couples were conducted by using modified scratch testing and ball-on-disc testing. From these test results different friction and wear mechanisms have been identified.

The deposition of thin organic coatings on the steel sheet metal has been found to be promising in order to control the friction and to avoid metal-metal contact resulting in galling. However, it has been found that the tribological characteristics of organic coated steel sheet are strongly influenced by coating chemical composition, the substrate surface topography and the coating thickness distribution.

The performance of the PVD coatings depends mainly on the chemical composition and topography of the coated surface. By choosing PVD coatings such as diamond like carbon (DLC) low and stable friction coefficients can be obtained in sliding contact against Zn. Surface irregularities such as droplet-like asperities may cause an initial high friction coefficient. However, after a running in process or by polishing the PVD coating low friction coefficients can be obtained resulting in a stable sliding contact.

The combination of imaging (optical profilometry, LOM, SEM) and chemical analytical techniques (EDS, AES, ToF-SIMS) gave valuable information concerning the friction and wear properties of the tribo surfaces investigated.

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5

Lindberg, Filip. "Sheet Metal Forming Simulations with FEM." Thesis, Umeå universitet, Institutionen för fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-51527.

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The design of new forming tools get more problemtic as the geometries get more complicated and the materials less formable. The idea with this project is to evaluate if an implementation of a simulation software in the designing process, to simulate the forming process before actually building the tools, could help Duroc Tooling avoid expensive mistakes. To evaluate this, the commercial FEM simulation software LS-DYNA was used in a complicated project, where the design of the forming tools for forming a girder was considered. The main objective was to avoid cracking and severe wrinkling which may result in the forming process. With help of simulations a stable forming process which did not yield cracks or severe wrinkling, was eventually found. The girder was almost impossible to form without cracking, but the breakthrough came when we tried to simulate a preforming step which solved the problem. Without a simulation software this would never have been tested since it would be to risky and expensive to try an idea which could turn out to be of no use. The simulations also showed that the springback - shape deformation occuring after pressing - was large and hard to predict without simulations. Therefore, the tools were also finally springback compensated. We concluded that simulations are very effective to quickly test new ideas which may be necessary when designing the tools for forming complicated parts. Simulation also provided detailed quantitative information about the expected cracks, wrinkles, and weaknesses of the resulting pieces. Even though there is cost associated with simulations, it is obvious from this project that a simulation software is a must if Duroc Tooling wants to be a leading company in sheet metal forming tools, and stand ready for the higher demands on the products in the future.
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6

Lanzon, Joseph, and kimg@deakin edu au. "EVALUATING LUBRICANTS IN SHEET METAL FORMING." Deakin University. Department of Science and Engineering, 1999. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20040428.095238.

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The sheet metal forming process basically involves the shaping of sheet metal of various thickness and material properties into the desired contours. This metal forming process has been extensively used by the automotive industry to manufacture both car panels and parts. Over the years numerous investigations have been conducted on various aspects of the manufacturing process with varied success. In recent years the requirements on the sheet metal forming industry have headed towards improved stability in the forming process while lowering environmental burdens. Therefore the overall aim of this research was to identify a technique for developing lubricant formulations that are insensitive to the sheet metal forming process. Due to the expense of running experiments on production presses and to improve time efficiency of the process the evaluation procedure was required to be performed in a laboratory. Preliminary investigations in the friction/lubricant system identified several laboratory tests capable of measuring lubricant performance and their interaction with process variables. However, little was found on the correlation between laboratory tests and production performance of lubricants. Therefore the focus of the research switched to identifying links between the performance of lubricants in a production environment and laboratory tests. To reduce the influence of external parameters all significant process variables were identified and included in the correlation study to ensure that lubricant formulations could be desensitised to all significant variables. The significant process variables were found to be sensitive to die position, for instance: contact pressure, blank coating of the strips and surface roughness of the dies were found significant for the flat areas of the die while no variables affected friction when polished drawbeads were used. The next phase was to identify the interaction between the significant variables and the main lubricant ingredient groups. Only the fatty material ingredient group (responsible for the formation of boundary lubricant regimes) was found to significantly influence friction with no interaction between the ingredient groups. The influence of varying this ingredient group was then investigated in a production part and compared to laboratory results. The correlation between production performance and laboratory tests was found to be test dependant. With both the Flat Face Friction test and the Drawbead Simulator unaffected by changes in the lubricant formulation, while the Flat Bottom Cup test showing similar results as the production trial. It is believed that the lack of correlation between the friction tests and the production performance of the lubricant is due to the absence of bulk plastic deformation of the strip. For this reason the Ohio State University (OSU) friction test was incorporated in the lubricant evaluation procedure along with a Flat Bottom Cup test. Finally, it is strongly believed that if the lubricant evaluation procedure highlighted in this research is followed then lubricant formulations can be developed confidently in the laboratory.
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7

Jansson, Tomas. "Optimization of sheet metal forming processes /." Linköping : Univ, 2005. http://www.bibl.liu.se/liupubl/disp/disp2005/tek936s.pdf.

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8

Shouler, Daniel Reginald. "Expanded forming limit testing for sheet forming processes." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609473.

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9

Park, Young-Bin. "Sheet metal forming using rapid prototyped tooling." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/18361.

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10

Powell, Nicholas Newton. "Incremental forming of flanged sheet metal components." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357609.

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11

Shang, Jianhui. "Electromagnetically assisted sheet metal stamping." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1158682908.

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12

Sanay, Berkay. "Prediction Of Plastic Instability And Forming Limits In Sheet Metal Forming." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612486/index.pdf.

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The Forming Limit Diagram (FLD) is a widely used concept to represent the formability of thin metallic sheets. In sheet metal forming processes, plastic instability may occur, leading to defective products. In order to manufacture defect free products, the prediction of the forming limits of sheet metals is a very important issue. FLD&rsquo
s can be obtained by several experimental, empirical and theoretical methods. However, the suitability and the accuracy of these methods for a given material may vary. In this study, FLD&rsquo
s are predicted by simulating Nakazima test using finite element software Pam-Stamp 2G. Strain propagation phenomenon is used to evaluate the limit strains from the finite element simulations. Two different anisotropic materials, AA2024-O and SAE 1006, are considered throughout the study and for each material, 7 different specimen geometries are analyzed. Furthermore, FLD&rsquo
s are predicted by theoretical approaches namely
Keeler&rsquo
s model, maximum load criteria, Swift-Hill model and Storen-Rice model. At the end of the study, the obtained FLD&rsquo
s are compared with the experimental results. It has been found that strain propagation phenomenon results for SAE 1006 are in a good agreement with the experimental results
however it is not for AA2024-O. In addition, theoretical models show some variations depending on the material considered. It has been observed that forming limit prediction using strain propagation phenomena with FE method can substantially reduce the time and cost for experimental work and trial and error process.
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13

Imbert, Boyd Jose. "Increased Formability and the Effects of the Tool/Sheet Interaction in Electromagnetic Forming of Aluminum Alloy Sheet." Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/857.

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This thesis presents the results of experimental and numerical work carried out to determine if electromagnetic forming (EMF) increases the formability of aluminum alloy sheet and, if so, to determine the mechanisms that play a role in the increased formability. To this end, free form (open cavity) and conical in-die samples were produced to isolate high strain rate constitutive and inertial effects from the effects of the interaction between the die and the sheet. Aluminum alloys AA5754 and AA6111 in the form of 1mm sheet were chosen since they are currently used in automotive production and are candidates for lightweight body panels. The experiments showed significant increases in formability in the conical die samples in areas where significant contact with the tool occurred, with no significant increase recorded for the free-formed samples. This indicates that the tool/sheet interaction is playing the dominant role in the increase in formability observed. Metallographic and fractographic analysis performed on the samples showed evidence of microvoid damage suppression, which may be a contributing factor to the increase in formability. Numerical modeling was undertaken to analyse the details of the forming operation and to determine the mechanisms behind the increased formability. The numerical calculations were performed with an explicit dynamic finite element structural code, using an analytical electromagnetic pressure distribution. Microvoid damage evolution was predicted using a microvoid damage subroutine based on the Gurson-Tvergaard-Needleman constitutive model. From the models it has been determined that the free forming process is essentially a plane-stress process. In contrast, the tool/sheet interaction produced in cone forming makes the process unique. When the sheet makes contact with the tool, it is subject to forces generated due to the impact, and very rapid bending and straightening. These combine to produce complex non-linear stress and strain histories, which render the process non-plane stress and thus make it significantly different from conventional sheet forming processes. Another characteristic of the process is that the majority of the plastic deformation occurs at impact, leading to strain rates on the order of 10,000 s-1. It is concluded that the rapid impact, bending and straightening that results from the tool/sheet interaction is the main cause of the increased formability observed in EM forming.
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14

Zhang, Wenfeng. "Design for uncertainties of sheet metal forming process." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180473874.

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15

Ucan, Meric. "Effect Of Constitutive Modeling In Sheet Metal Forming." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613447/index.pdf.

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This study focuses on the effects of different constitutive models in sheet metal forming operations by considering the cylindrical and square cup drawing and V-bending simulations. Simulations are performed using eight different constitutive models
elastic plastic constitutive model with isotropic hardening, elastic plastic constitutive model with kinematic hardening, elastic plastic constitutive model with combined hardening, power law isotropic plasticity, piecewise linear isotropic plasticity, Barlatthree-parameter, cyclic elastoplastic and Hill&rsquo
48 model.The numerical analyses are accomplished by using three different 1 mm thick sheet materials
St12 steel, Al-5182 aluminum and stainless steel 409 Ni. An explicit finite element code is used in the simulations. For square cup drawing, three different blank holder forces
2 kN, 4 kN and 5 kN are considered for St12 steel, whereas only 5 kN blank holder force is applied for stainless steel 409 Ni and Al-5182 aluminum. A number of experiments are carried out and analytical calculations are utilized to evaluate the results of simulations. In cylindrical cup drawing, simulation results of different constitutive models show good agreement with analytical calculations for thickness strain and effective stress distributions. In square cup drawing, simulation results of all the models displayed good agreement with the experimental results for edge contour comparisons, although the distributions of effective stress vary for different models within the cup. The numerically and experimentally obtained springback amounts are also in good agreement. The simulation results obtained for piecewise linear isotropic plasticity and power law isotropic plasticity models show better agreement with the analytical solutions and experiments.
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16

Yue, Zhenming. "Ductile damage prediction in sheet metal forming processes." Thesis, Troyes, 2014. http://www.theses.fr/2014TROY0025/document.

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L'objectif de ce travail est de proposer un modèle de comportement avec endommagement ductile pour la simulation des procédés de mise en forme de tôles minces qui peut bien représenter le comportement des matériaux sous des trajets de chargement complexes en grandes déformations plastiques. Basé sur la thermodynamique des processus irréversibles, les équations de comportement couplé à l’endommagement tiennent compte des anisotropies initiales et induites, de l’écrouissage isotrope et cinématique et de l’endommagement isotrope ductile. Les effets de fermeture des microfissures, de triaxialité des contraintes et de l’angle de Lode sont introduits pour influencer l’évolution de l’endommagement sous une large gamme de triaxialité des contraintes. La distorsion de la surface de charge est introduite via un tenseur déviateur qui gouverne la distorsion de la surface de charge. A des fins de comparaison, les courbes limites de formage sont tracées basées sur l’approche M-K.Des essais sont conduits sur trois matériaux pour les besoins d’identification et de validation des modèles proposés. L’identification utilise un couplage entre le code ABAQUS et un programme MATLAB via un script en langage Python. Après l’implémentation numérique du modèle dans ABAQUS/Explicite et une étude paramétrique systématique, plusieurs procédés de mise en forme de structures minces sont simulés. Des comparaisons expériences-calculs montrent les performances prédictives de la modélisation proposée
The objective of this work is to propose a “highly” predictive material model for sheet metal forming simulation which can well represent the sheet material behavior under complex loading paths and large plastic strains. Based on the thermodynamics of irreversible processes framework, the advanced fully coupled constitutive equations are proposed taking into account the initial and induced anisotropies, isotropic and kinematic hardening as well as the isotropic ductile damage. The microcracks closure, the stress triaxiality and the Lode angle effects are introduced to influence the damage rate under a wide range of triaxiality ratios. The distortion of the yield surface is described by replacing the usual stress deviator tensor by a ‘distorted stress’ deviator tensor, which governs the distortion of the yield surfaces. For comparisons, the FLD and FLSD models based on M-K approach are developed.A series of experiments for three materials are conducted for the identification and validation of the proposed models. For the parameters identification of the fully coupled CDM model, an inverse methodology combining MATLAB-based minimization software with ABAQUS FE code through the Python script is used. After the implementation of the model in ABAQUS/Explicit and a systematic parametric study, various sheet metal forming processes have been numerically simulated. At last, through the comparisons between experimental and numerical results including the ductile damage initiation and propagation, the high capability of the fully coupled CDM model is proved
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17

Lind, Markus, and Viktor Sjöblom. "Industrial Sheet Metal Forming Simulation with Elastic Dies." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-16782.

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As part of the development process for new stamping dies, in the automotive sheet metal forming (SMF) industry, the majority of all forming operations are simulated with the Finite Element Method (FEM) before the dies are manufactured. Today, these simulations are conducted with rigid tools under the assumption that there are no tool deformations. However, research shows that tool deformations have an influence on the finished product. In real production these deformations are compensated by manual rework during the try-out. Additional reason for simulating with rigid dies is that there are non-existing simulation methods elaborated for elastic stamping dies. Also, simulation of elastic tools requires high computational power.     Since simulations today are performed with rigid stamping dies the purpose of this work is to investigate the conditions of how to conduct SMF-simulations with elastic stamping dies. The object that will be studied is a stamping die for a Volvo XC90 inner door used in a single-action press. This work is part of the development to minimize the manual rework, with the goal to compensate for tool deformations in a virtual environment.    Results for rigid stamping dies in LS-Dyna was compared to currently used AutoForm as a pre-study. A simple model was then created to find a suitable method while using elastic stamping dies. The developed method was used for an industrial size stamping die.     Since there are little amount of research performed on simulations using elastic stamping dies, elasticity and complexity were gradually introduced into the FE-model. As a first step, only the punch was included as an elastic solid. Secondly, the die was added. Finally, the entire die was simulated as elastic together with the hydraulic cushion of the press. When the FE-model worked as expected a suitable method for minimizing the simulation time with acceptable results was studied.     Comparisons of measured- and simulation results show a high correlation. To improve the results from the FE-model factors such as press deformations, advanced friction models, etc. should be included.    Conclusions from this work shows that it is possible to perform SMF-simulations with elastic stamping dies. As the computational time normally is high this work also presents a method first step to reduce the computational time with acceptable results. Comparisons between simulations with rigid and elastic stamping dies proves that there are significant differences in the outcome of the two methods.
Reduced Lead Time through Advanced Die Structure Analysis - Vinnova
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18

Esche, Sven Karsten. "Developments for two-dimensional sheet metal forming analysis /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487946103566303.

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19

Eriksson, Anton. "Non-Linear strain paths in Sheet Metal Forming." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-21906.

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Today's automotive requirements have resulted in complex Sheet Metal Forming (SMF) processes of Sheet Metal (SM) with reduced formability, and thus it is crucial to be able to predict formability accurately to prevent material failure during SMF. Formability predictions today utilize Forming Limit Curves (FLC)s in Finite Element Analysis (FEA), but  FLCs are not valid for the Non-Linear Strain Paths (NLSP)s generated during SMF. One purpose of this thesis is thus to increase the knowledge on FP handling NLSP,  which was obtained through providing suggestions of failure models for handling NLSP effects, based upon literature on the subject. Generating NLSP experimentally is both time and material costly with the conventional method, thus the second purpose of this thesis was to increase the knowledge on test procedures for generating NLSP in SM. Based upon the findings of Chandramohan \cite{chandramohan_study_2021} five test procedures for generating NLSP were put forward, and the Nakajima test with modified punch geometry was chosen for further study.   In this thesis, the NLSP characteristics of two modified punch geometries were evaluated by FEA performed using LS-DYNA. For the FEA three specimens with blank width of 50, 100 and 200 mm was used, and the anisotropic Barlat yld2000  was used as the material model. This material model was calibrated to material data of Mild steel CR4, Aluminium alloy AA6016, and Dual-phase steel DP800. The results for all materials showcased similar reacquiring general NLSP characteristics at the corners of the punch features, which are unfavorable positions when failure by necking is evaluated, and thus it was concluded that the tested punch geometries are not favorable and more development of the punch geometry is needed.
Dagens fordonskrav, har lett till komplexa plåtformnings processer av plåtmaterial med reducerad formbarhet, och det är därför väsenligt att kunna förutsäga formbarhet noggrant för att förhindra materialbrott under plåtformning. Försträckning och brott förutses idag genom Formgränskurvor (FGK) i finita element analyser (FEA), men dessa gäller inte för icke-linjära töjningsvägar som uppkommer under plåtformning. Ett syfte av denna avhandling är därför att öka kunskapen kring modeller för att förutsäga formbarhet under icke-linjära töjningsbanors effekter, vilket uppnådes genom att  presenteras  förslag på brott modeller för att hantera de icke-linjära töjningsvägar baserade på  literatur inom området. Att generera icke-linjära töjningsvägar experimentellt är både tids och materialkrävande med den konventionella metoden, således är det andra syftet av denna avhandling att öka kunskapen kring test metoder för att generera icke-linjär töjningsbvägar i plåt. Baserat på Chandramohans \cite{chandramohan_study_2021} resultat diskuteras fem test procedurer för att generera icke-linjära töjningsvägar, och Nakajima test med modifierad stämpelgeometri valdes för vidare studie.  I denna avhandling studerades töjningsignaturen av två stämpelgeometrier med FEA i LS-DYNA. Till FEA:n användes tre ämnen med bredd av 50, 100 och 200mm, och anisotropiska Barlat yld2000 användes som materialmodell. Denna materialmodell kalibrerades mot experimentella mätvärden för mjukt stål CR4, Aluminiumlegering AA6016 och Stål DP800. Resultaten visade för alla material återkommande generella icke-linjära töjningsbanor enbart för hörnorna på stansgeometrierna, vilket är icke önskvärda positioner då brott pga. midjebildning utvärderas, och således drogs slutsatsen att nuvarande stansgeometri inte är gynnsam och ytterligare utveckling behövs.
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20

Raithatha, Ankor Mahendra. "Incremental sheet forming : modelling and path optimisation." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:89b0ac1e-cab4-4d80-b352-4f48566c7668.

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Incremental sheet forming (ISF) is a novel metal shaping technology that is economically viable for low-volume manufacturing, customisation and rapid-prototyping. It uses a small tool that is controlled by a computer-numerically controlled sequence and the path taken by this tool over the sheet defines the product geometry. Little is currently known about how to design the tool-path to minimise geometric errors in the formed part. The work here addresses this problem by developing a model based tool-path optimisation scheme for ISF. The key issue is how to generate an efficient model for ISF to use within a path optimisation routine, since current simulation methods are too slow. A proportion of this thesis is dedicated to evaluating the applicability of the rigid plastic assumption for this purpose. Three numerical models have been produced: one based on small strain deformation, one based on limit analysis theory and another that approximates the sheet to a network of rods. All three models are formulated and solved as second-order cone programs (SOCP) and the limit analysis based model is the first demonstration of an upper-bound shell finite element (FE) problem solved as an SOCP. The models are significantly faster than commercially available FE software and simulations are compared with experimental and numerical data, from which it is shown the rigid plastic assumption is suitable for modelling deformation in ISF. The numerical models are still too slow for the path optimisation scheme, so a novel linearised model based on the concept of spatial impulse responses is also formulated and used in an optimal control based tool-path optimisation scheme for producing axisymmetric products with ISF. Off-line and on-line versions of the scheme are implemented on an ISF machine and it is shown that geometric errors are significantly reduced when using the proposed method. This work provides a new structured framework for tool-path design in ISF and it is also a novel use of feedback to compensate for geometrical errors in ISF.
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21

Woodward, Steven T. "Springback Calibration of Sheet Metal Components Using Impulse Forming Methods." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306683543.

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22

Yang, Xi. "Investigation of Formability and Fracture in Advanced Metal Forming Process- Bulk Forging and Sheet Metal Forming." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1403889605.

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23

Odenberger, Eva-Lis. "Concepts for hot sheet metal forming of titanium alloys /." Luleå : Department of Applied Physics and Mechanical Engineering, Division of Solid Mechanics, Luleå University of Technology, 2009. http://www.avhandlingar.se/avhandling/167c433b06/.

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24

Onder, Erkan Ismail. "Assessment Of Sheet Metal Forming Processes By Numerical Experiments." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606159/index.pdf.

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iv Sheet metal forming technologies are challenged especially by the improvements in the automotive industry in the last decades. To fulfill the customer expectations, safety requirements and market competitions, new production technologies have been implemented. This study focuses on the assessment of conventional and new sheet metal forming technologies by performing a systematic analysis. A geometry spectrum consisting of six different circular, elliptic, quad cross-sections are selected for the assessment of conventional deep drawing, hydro-mechanical deep drawing and high-pressure sheet metal forming. Within each cross-section, three different equivalent drawing ratios are used as a variant. More than 200 numerical experiments are performed to predict the forming limits of three competing processes. St14 stainless steel is used as the material throughout the assessment study. The deformation behavior is described by an elasto-plastic material model and all numerical simulations are carried out by using dynamic-explicit commercial The process validation is done by interpreting the strain results of numerical experiment. Therefore, the reliability of predictions in the assessment study highly depends on the quality of simulations. The precision of numerical experiments are verified by comparing to NUMISHEET benchmarks, analytical formulation, and experiments to increase the assets of the assessment study. The analyses revealed that depending on the workpiece geometry and dimensional properties certain processes are more preferable for obtaining satisfactory products. The process limits for each process are established based on the analyzed crosssections of the spectrum. This data is expected to be useful for predicting the formability limits and for selecting the appropriate production process according to a given workpiece geometry.Dynamic-explicit FEM, Deep drawing, Hydroforming, Forming limits, Process evaluation
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25

Sefton, Harvey. "A friction sensor for a sheet metal forming simulator." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0020/MQ54039.pdf.

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26

Odenberger, Eva-Lis. "Material characterisation for analyses of titanium sheet metal forming." Licentiate thesis, Luleå : Luleå tekniska universitet, 2005. http://epubl.ltu.se/1402-1757/2005/63/.

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27

Ledentsov, Dmitry [Verfasser]. "Model adaptivity in sheet metal forming simulation / Dmitry Ledentsov." Aachen : Shaker, 2010. http://d-nb.info/1122546106/34.

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28

Bentsrud, Herman. "Friction and material modelling in Sheet Metal Forming Simulations." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-19686.

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In today’s car manufacturing industry, sheet metal forming is a important process that takes preparation, which is time consuming and complex when new processes are made. When new metal grades and alloys are provided to the industry, tests are conducted to determine it’s behaviour and strengths. This gives the data for complex material models that can approximate the metal behaviour in an accurate way in a simulation environment. One of the unknown factors from tests is the friction coefficient on the sheet metal. The software Triboform is able to provide an adaptable friction coefficient model that depends on multiple simulation and user input conditions. The problems that occur when acquiring data for the material model is that testing is time consuming and the friction model has to be adjusted to give accurate results. At Volvo Cars there are two material models used with their different advantages, BBC 2005 and Vegter 2017.The purpose with this work is to compare the two material models using the Triboform friction models implemented to see if any combination provides accurate simulation results and then create recommendations for which model is best suited for different cases. Some side studies is also done with an older Vegter model, a strain rate sensitive BBC 2005 model and a Triboform model on all simulation parts.The purpose is achieved by implementing the Triboform model in Autoform and run a simulation of a Limiting Dome Height (LDH) test with both material models and compare the results with experimental data for several different materials. The data that is directly compared from the LDH test is the major and minor strain from two perpendicular sections at four different stages and also the force from the punch tool. The material models will be evaluated by how it manages to mimic the strain behaviour of the metals and how it estimates the punch force.The results point towards an improvement of the accuracy for most of the metals tested and BBC 2005 is the better model if there’s available biaxial data from tests, Vegter 2017 is decent if there’s not. However Vegter 2017 is not a good option for aluminum alloys simulations when the punch force is compared. Side study also shows that Vegter 2017 is bit of a downgrade when it comes to strain values, compared to the old Vegter.The work, in summary shows a dynamic friction model can improve the accuracy for strain predictions in the simulation process. If there’s biaxial yield data available for the metal or if it’s an aluminum alloy, BBC 2005 is the superior choice, but if only tensile tests are available for metals, Vegter 2017 is a decent choice for some cases.
I dagens bilindustri är plåtmetalformning en viktig process som kräver förberedelser som är tidskonsumerande och komplex när nya processer tillkommer. När nya metallslag kommer in till industrin, så utförs tester för att avgöra dess egenskaper och styrka. Denna testdata används till materialmodeller som kan approximera metallens beteende på ett noggrant sätt i en simuleringsmiljö. Den okända faktorn från dessa test är friktionskoefficienten på plåten. Programvaran Triboform är kapabel att göra en dynamisk friktionsmodel som beror på användar- och simuleringsdata. Problemen som uppstår vid framtagning av data är att det är tidskonsumerande och flera simuleringar måste göras för att bestämma friktionen. Volvo Cars använder sig av två modeller med olika fördelar, BBC 2005 och Vegter 2017.Syftet med detta arbete är att jämföra de två materialmodellerna med Triboform modeller implementerat för att se om de påverkar noggrannheten i simuleringar och sedan förse rekommendationer för vilken modell passar bäst för olika fall. Några sidojobb i studien som görs är en jämförelse med gamla Vegter modellen, ett test med en modell som är känslig för töjningshastighet och test med att implementera Triboform modellen på alla pressverktyg.Detta utförs med att implementera Triboform modellerna i Autoform och köra en simulering på ett LDH-test med båda materialmodeller och jämföra resultaten med experimentell data för flera olika metaller. Data som skall jämföras från LDH-testet är första och andra huvudtöjningen i två vinkelräta sektioner i fyra processsteg och stämpelkraften genom hela processen. Modellerna kommer evalueras genom hur de lyckas imitera töjningens beteende och hur den estimerar stämpelkraften.Resultaten pekar mot en förbättring när Triboform är implementerat i simuleringar för de flesta metaller som ingår i testen och BBC 2005 är den model som föredras om det finns tillgänglig biaxiel spänning data från tester, Vegter 2017 är en duglig modell om dessa data inte finns. Vegter 2017 är dock inte ett bra alternativ när det kommer till jämförelse av töjning och stämpelkraften för aluminium. Sidojobb med gamla Vegter visar att den nya Vegter 2017 inte är en direkt förbättring med hänsyn till noggrannheter av krafter och töjningar.Arbetet visar att en dynamisk friktionsmodel kan förbättra prediktering av töjningar i simuleringar. Om det finns biaxiel data för metallen eller om det gäller att simulera aluminium är BBC 2005 det bättre altermativet, om det endast finns dragprovsdata för metallen så är Vegter 2017 duglig för vissa fall.
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29

Fallahiarezoodar, Ali fallahiarezoodar. "PREDICTION AND REDUCTION OF DEFECTS IN SHEET METAL FORMING." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523879307901727.

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30

Vladimirov, Ivaylo N. "Anisotropic material modelling with application to sheet metal forming." Aachen Shaker, 2009. http://d-nb.info/999285513/04.

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31

Alghtani, Abdulaziz Hosain. "Analysis and optimization of springback in sheet metal forming." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/10523/.

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Sheet metal forming processes are widely used in the automotive industry to fabricate many components such as body panels, the structural members of the chassis and so on. The forming process involves many stages. There are many defects that might occur on a work piece during or after each set of processes and one of the most challenging of these is associated with the phenomenon of springback; that is, the distortion in specimen geometry due to the elastic recovery and other effects. The integration of springback into the design of the forming process represents a significant challenge due to difficulties associated with its prediction. There are several factors that control the magnitude and direction of component distortion causing by springback. The primary aim of the present study is to evaluate the influence exerted on springback by the main parameters that affect the forming process. This will provide guide lines to create new CAE methods that can be used to predict the amount of springback within sheet metal forming processes. Two common forming processes will be investigated within this work, the so called L-bending and U-drawing processes, since these underpin many of the more complex forming operations. A forming test rig has been designed and manufactured that replicates each of these processes under controlled and repeatable conditions. Process parameters that can be controlled are the die and punch profile radii and clearance between the punch and die, and the normal clamp load applied on the work piece by the blank holder. In parallel, finite element models capable of simulating the L-bending and U-drawing bending processes were developed and validated for four different blanks materials: high and low strength steel, and high and low strength aluminium alloy. Material characterization for four different blanks was conducted to derive required parameters for the simulation analysis. Also, friction coefficients were measured between each blank material and the forming tools using a pendulum tribometer. Mesh sensitivity studies were firstly conducted to provide a mesh that represents an appropriate compromise between accuracy and consuming time. Results from the numerical analysis were compared to those from the experiments and good agreement was generally found, except for the high strength steel where the galvanised coating (not modelled in the analysis) affected the results. The model was then used to conduct parametric studies on the effect of certain parameters on the amount of the springback i.e. the blank holder load, die and punch radii and the radial clearance. Finally, an optimisation scheme was developed to derive the optimum combination of parameters to minimise springback. These results and the general methodology could form the basis of a reliable CAE system to control springback in common metal forming operations.
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32

Liu, Weijie. "Advanced modelling for sheet metal forming under high temperature." Thesis, Troyes, 2017. http://www.theses.fr/2017TROY0019/document.

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L’objectif de cette thèse est de proposer deux approches complémentaires de modélisation et de simulation numériques des procédés de mise en forme de structures minces. La première est une approche inverse multi-pas, délibérément simplifiée, pour simuler et "optimiser" rapidement et à moindre coût des procédés d’emboutissage de tôles minces, tout en maintenant une bonne précision dans le calcul des contraintes. Un solveur statique implicite est développé en introduisant plusieurs configurations intermédiaires construites efficacement en utilisant une technique de programmation quadratique avec projection. La deuxième approche, de nature incrémentale, repose sur (i) une formulation d’équations de bilan et d’équations de comportement multi-physiques fortement couplés formulées dans le cadre des milieux micromorphes ; (ii) une discrétisation spatiale par EF et temporelle par DF avec un solveur global dynamique explicite et une intégration locale itérative implicite. Une attention particulière est accordée aux aspects thermiques avec l’introduction d’une microtempérature et ses premiers gradients conduisant à l’obtention de deux équations thermiques fortement couplées généralisant de nombreux modèles non locaux proposés dans la littérature. L'approche inverse multi-pas a été implémentée dans le code maison KMAS et l’approche incrémentale non locale a été implémentée dans ABAQUS/Explicit. Des études paramétriques sont menées et des validations sur des exemples simples et sur des procédés d’emboutissage sont réalisées
The aim of this thesis is to propose two complementary approaches for modeling and numerical simulations of thin sheet metal forming processes. The first one is a deliberately simplified multi-step inverse approach to simulate and "optimize" rapidly and inexpensively thin-sheet stamping processes while maintaining good accuracy in the stress calculation. An implicit static solver is developed by introducing several efficiently constructed intermediate configurations using a quadratic programming technique with projection. The second approach, which is of an incremental nature, is based on (i) a formulation of equilibrium equations and strongly coupled multiphysical behavior equations formulated in the context of micromorphic continua; (ii) spatial discretization by FEM and time discretization by FD with an explicit dynamic global solver and implicit iterative local integration scheme. Particular attention is paid to the nonlocal thermal aspects with the introduction of a micro-temperature and its first gradients leading to two strongly coupled thermal equations generalizing several thermal nonlocal models proposed in the literature. The multi-step inverse approach was implemented in the KMAS in house code while the nonlocal incremental approach was implemented in ABAQUS/Explicit. Parametric studies are performed and validations are carried out on simple examples and on deep drawing processes
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33

Jackson, Kathryn Pamela. "The mechanics of incremental sheet forming." Thesis, University of Cambridge, 2008. https://www.repository.cam.ac.uk/handle/1810/267843.

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Incremental sheet forming (ISF) is a flexible process where an indenter moves over the surface of a sheet of metal to form a 3D shell incrementally by a progression of localised deformation. Despite extensive research into the process, the deformation mechanics is not fully understood. This thesis presents new insights into the mechanics of ISF applied to two groups of materials: sheet metals and sandwich panels. A new system for measuring tool forces in ISF is commissioned. The system uses six loadcells to measure reaction forces on the workpiece frame. Each force signal has an uncertainty of ±15 N. This is likely to be small in comparison to tool forces measured in ISF. The mechanics of ISF of sheet metals is researched. Through-thickness deformation and strains of copper plates are measured for single-point incremental forming (SPIF) and two-point incremental forming (TPIF). It is shown that the deformation mechanisms of SPIF and TPIF are shear parallel to the tool direction, with both shear and stretching perpendicular to the tool direction. Tool forces are measured and compared throughout the two processes. Tool forces follow similar trends to strains, suggesting that shear parallel to the tool direction is a result of friction between the tool and workpiece. The mechanics of ISF of sandwich panels is investigated. The mechanical viability of applying ISF to various sandwich panel designs is evaluated by observing failure modes and damage under two simple tool paths. ISF is applicable to metal/polymer/metal sandwich panels. This is because the cores and faceplates are ductile and largely incompressible, and therefore survive local indentation during ISF without collapse. Through-thickness deformation, tool forces and applicability of the sine law for prediction of wall thickness are measured and compared for a metal/polymer/metal sandwich panel and a monolithic sheet metal. The mechanical results for ISF of sheet metals transfer closely to sandwich panels. Hence, established knowledge and process implementation procedures derived for ISF of monolithic sheet metals may be used in the future for ISF of sandwich panels.
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34

Cao, Jian Ph D. Massachusetts Institute of Technology. "Design and control of forming parameters for sheet metal forming using finite element analysis." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11776.

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35

Goel, Amit. "Blank optimization in sheet metal forming using finite element simulation." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/3120.

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The present study aims to determine the optimum blank shape design for the deep drawing of arbitrary shaped cups with a uniform trimming allowance at the flange i.e. cups without ears. This earing defect is caused by planar anisotropy in the sheet and the friction between the blank and punch/die. In this research, a new method for optimum blank shape design using finite element analysis has been proposed. Explicit non-linear finite element (FE) code LSDYNA is used to simulate the deep drawing process. FE models are constructed incorporating the exact physical conditions of the process such as tooling design like die profile radius, punch corner radius, etc., material used, coefficient of friction, punch speed and blank holder force. The material used for the analysis is mild steel. A quantitative error metric called shape error is defined to measure the amount of earing and to compare the deformed shape and target shape set for each stage of the analysis. This error metric is then used to decide whether the blank needs to be modified or not. The cycle is repeated until the converged results are achieved. This iterative design process leads to optimal blank shape. In order to verify the proposed method, examples of square cup and cylindrical cup have been investigated. In every case converged results are achieved after a few iterations. So through the investigation the proposed systematic method of optimal blank design is found to be very effective in the deep drawing process and can be further applied to other stamping applications.
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36

Pilthammar, Johan. "Elastic Press and Die Deformations in Sheet Metal Forming Simulations." Licentiate thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-15481.

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Never before has the car industry been as challenging, interesting, and demanding as it is today. New and advanced techniques are being continuously introduced, which has led to increasing competition in an almost ever-expanding car market. As the pace and complexity heightens in the car market, manufacturing processes must advance at an equal speed. An important manufacturing process within the automotive industry, and the focus of this thesis, is sheet metal forming (SMF). Sheet metal forming is used to create door panels, structural beams, and trunk lids, among other parts, by forming sheets of metal in press lines with stamping dies. The SMF process has been simulated for the past couple of decades with finite element (FE) simulations, whereby one can predict factors such as shape, strains, thickness, springback, risk of failure, and wrinkles. A factor that most SMF simulations do not currently include is the die and press elasticity. This factor is handled manually during the die tryout phase, which is often long and expensive. The importance of accurately representing press and die elasticity in SMF simulations is the focus of this research project. The research objective is to achieve virtual tryout and improved production support through SMF simulations that consider elastic die and press deformations. Loading a die with production forces and including the deformations in SMF simulations achieves a reliable result. It is impossible to achieve accurate simulation results without including the die deformations. This thesis also describes numerical methods for optimizing and compensating tool surfaces against press and die deformations. In order for these compensations to be valid, it is imperative to accurately represent dies and presses. A method of measuring and inverse modeling the elasticity of a press table has been developed and is based on digital image correlation (DIC) measurements and structural optimization with FE software. Optimization, structural analysis, and SMF simulations together with experimental measurements have immense potential to improve simulation results and significantly reduce the lead time of stamping dies. Last but not least, improved production support and die design are other areas that can benefit from these tools.
Aldrig tidigare har bilindustrin varit så utmanande, intressant och spännande som idag. Ny och avancerad teknik introduceras i en allt snabbare takt vilket leder till ständigt ökande konkurrens på en, nästan ständigt, ökande bilmarknad. Den ständigt ökande komplexiteten ställer även krav på tillverkningsprocesserna. En viktig process, som denna licentiatuppsats fokuserar på, är pressning av plåt. Tillverkningstekniken används för att forma plåtar till dörrpaneler, strukturbalkar, motorhuvar, etc. Plåtar formas med hjälp av pressverktyg monterade i plåtformningspressar. Plåtformningsprocessen simuleras sedan ett par decennium tillbaka med Finita Element (FE) simuleringar. Man kan på så sätt prediktera form, töjningar, tjocklek, återfjädring, rynkor, risk för försträckning och sprickor m.m. En faktor som för tillfället inte inkluderas i näst intill alla plåtformningssimuleringar är elastiska press- och verktygsdeformationer. Detta hanteras istället manuellt under, den oftast långa och dyra, inprovningsfasen. Detta projekt har visat på vikten av att representera press och verktygsdeformationer i plåtformningssimuleringar. Detta demonstreras genom en analys av ett verkligt pressverktyg som belastas med produktionskrafter. Det är inte möjligt att uppnå bra simuleringsresultat utan att inkludera verktygsdeformationer i simuleringsmodellen. Uppsatsen beskriver även numeriska metoder för att optimera och kompensera verktygsytor mot press och verktygsdeformationer. För att dessa kompenseringar ska stämma är det viktigt att man representerar både verktyg och press på ett korrekt sätt. Förslag på en metod för att mäta och inversmodellera pressdeformationer har utvecklats, metoden är baserad på mätningar med DIC-systemet ARAMIS och optimering i FE-mjukvaror. Optimering, strukturanalys, och plåtformningsanalys tillsammans med experimentella mätningar har en stor potential att förbättra plåtformningssimuleringar samt reducera ledtiden för pressverktyg. Sist men inte minst, andra positiva effekter är en enklare och smidigare konstruktionsprocess och förbättrad produktionssupport.
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37

Moshfegh, Ramin. "Aspects on finite element simulation of sheet metal forming processes /." Linköping : Department of Solid Mechanics, Department of Mechanical Engineering, Linköping University, 2006. http://www.bibl.liu.se/liupubl/disp/disp2006/tek1042s.pdf.

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38

Arwidson, Claes. "Numerical simulation of sheet metal forming for high strength steels." Licentiate thesis, Luleå, 2005. http://epubl.luth.se/1402-1757/2005/08.

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39

Rozgic, Marco [Verfasser]. "Mathematical Optimization of Industrial Sheet Metal Forming Processes / Marco Rozgic." Hamburg : Helmut-Schmidt-Universität, Bibliothek, 2018. http://d-nb.info/1165340658/34.

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40

Webb, Richard Davis 1957. "Spatial frequency based closed-loop control of sheet metal forming." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14827.

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41

Vaughan, Chester Dewey. "Cycle-to-cycle control of reconfigurable die sheet metal forming." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/17953.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references (leaves 85-86).
This research addresses cycle to cycle control as applied to a sheet metal stretch forming process. More specifically, it attempts to validate the use of cycle to cycle (CtC) control for a multiple input-multiple output process. The work presented in this thesis attempts to answer some basic manufacturing questions. The first is, "Can a multivariable discrete system control theory be used to model a sheet metal shape control process?" The second question is, "Does such a "cycle to cycle control system provide a significant improvement over the present industry standard control methods". To address these questions, CtC control methods are applied to a reconfigurable die stretch forming process. The theoretical foundation of the stretch forming process is presented. Several open and closed loop control methods are discussed. A methodology for evaluating the part quality is defined in terms of the process mean shift and variance. The system dynamics are presented in terms of unwanted process disturbances. In-depth experiments are then performed to quantify the process performance under CtC control. The CtC process yield is compared the process yield of an identical process under open loop control using the Expected Quality Loss Function. It is shown that implementation of the reconfigurable die under CtC control eliminates the process mean shift but increases the part variation. It is also shown that CtC control produces the highest yield of acceptable parts.
by Chester Dewey Vaughan, IV.
S.M.
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42

Knapke, Joseph A. (Joseph Anthony). "Evaluation of a variable-configuration-die sheet metal forming machine." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14607.

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43

Rozgi`c, Marco [Verfasser]. "Mathematical Optimization of Industrial Sheet Metal Forming Processes / Marco Rozgic." Hamburg : Helmut-Schmidt-Universität, Bibliothek, 2018. http://d-nb.info/1165340658/34.

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44

Boyd, Malcolm Russell. "An investigation of the friction and lubrication effects in deep drawing process through simulative and empirical testing." Thesis, University of Ulster, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243620.

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45

Hussain, Muhammad Masood [Verfasser]. "Polymer Injection Sheet Metal Forming – Experiments and Modeling / Muhammad Masood Hussain." Aachen : Shaker, 2013. http://d-nb.info/1051570921/34.

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46

Abd, El All Fahd Fathi. "Finite element and experimental studies of springback in sheet metal forming." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0017/MQ54100.pdf.

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47

Shankar, Ravi. "Surface reconstruction and tool path strategies for incremental sheet metal forming /." Aachen : Shaker, 2008. http://d-nb.info/989220230/04.

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48

Vladimirov, Ivaylo [Verfasser]. "Anisotropic material modelling with application to sheet metal forming / Ivaylo Vladimirov." Aachen : Shaker, 2009. http://d-nb.info/1161300031/34.

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49

Boas, Ryan C. "Sequential setup mechanism design for a reconfiguarable sheet metal forming die." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42700.

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50

Vladimirov, Ivaylo N. [Verfasser]. "Anisotropic material modelling with application to sheet metal forming / Ivaylo Vladimirov." Aachen : Shaker, 2009. http://nbn-resolving.de/urn:nbn:de:101:1-2018061705410905698643.

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