Articles de revues : « Geometrical deviation model »

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Tabar, Roham Sadeghi, Kristina Wärmefjord et Rikard Söderberg. « A new surrogate model–based method for individualized spot welding sequence optimization with respect to geometrical quality ». International Journal of Advanced Manufacturing Technology 106, n^o 5-6 (19 décembre 2019) : 2333–46. http://dx.doi.org/10.1007/s00170-019-04706-x.

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AbstractIn an individualized shee metal assembly line, form and dimensional variation of the in-going parts and different disturbances from the assembly process result in the final geometrical deviations. Securing the final geometrical requirements in the sheet metal assemblies is of importance for achieving aesthetic and functional quality. Spot welding sequence is one of the influential contributors to the final geometrical deviation. Evaluating spot welding sequences to retrieve lower geometrical deviations is computationally expensive. In a geometry assurance digital twin, where assembly parameters are set to reach an optimal geometrical outcome, a limited time is available for performing this computation. Building a surrogate model based on the physical experiment data for each assembly is time-consuming. Performing heuristic search algorithms, together with the FEM simulation, requires extensive evaluations times. In this paper, a neural network approach is introduced for building surrogate models of the individual assemblies. The surrogate model builds the relationship between the spot welding sequence and geometrical deviation. The approach results in a drastic reduction in evaluation time, up to 90%, compared to the genetic algorithm, while reaching a geometrical deviation with marginal error from the global optimum after welding in a sequence.

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Huang, Zhicheng, Jean-Yves Dantan, Alain Etienne, Mickaël Rivette et Nicolas Bonnet. « Geometrical deviation identification and prediction method for additive manufacturing ». Rapid Prototyping Journal 24, n^o 9 (12 novembre 2018) : 1524–38. http://dx.doi.org/10.1108/rpj-07-2017-0137.

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Purpose One major problem preventing further application and benefits from additive manufacturing (AM) nowadays is that AM build parts always end up with poor geometrical quality. To help improving geometrical quality for AM, this study aims to propose geometrical deviation identification and prediction method for AM, which could be used for identifying the factors, forms and values of geometrical deviation of AM parts. Design/methodology/approach This paper applied the skin model-based modal decomposition approach to describe the geometrical deviations of AM and decompose them into different defect modes. On that basis, the approach to propose and extend defect modes was developed. Identification and prediction of the geometrical deviations were then carried out with this method. Finally, a case study with cylinders manufactured by fused deposition modeling was introduced. Two coordinate measuring machine (CMM) machines with different measure methods were used to verify the effectiveness of the methods and modes proposed. Findings The case study results with two different CMM machines are very close, which shows that the method and modes proposed by this paper are very effective. Also, the results indicate that the main geometrical defects are caused by the shrinkage and machine inaccuracy-induced errors which have not been studied enough. Originality/value This work could be used for identifying and predicting the forms and values of AM geometrical deviation, which could help realize the improvement of AM part geometrical quality in design phase more purposefully.

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Nguyen, Dinh Son, Frederic Vignat et Daniel Brissaud. « Geometrical Deviation Model of product throughout its life cycle ». International Journal of Manufacturing Research 6, n^o 3 (2011) : 236. http://dx.doi.org/10.1504/ijmr.2011.041128.

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Polini, Wilma, et Andrea Corrado. « A Unique Model to Estimate Geometric Deviations in Drilling and Milling Due to Two Uncertainty Sources ». Applied Sciences 11, n^o 5 (24 février 2021) : 1996. http://dx.doi.org/10.3390/app11051996.

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Industry 4.0 involves the use of information and communication technologies to transform industry by intelligent networking machines and processes. The availability of big data sets from manufacturing and inspection allow for developing new and more accurate simulation models. This involves the development of new machining simulation models to consider the geometrical deviations of the workpiece due to the machine tool, the part datum surfaces and the fixturing equipment. This work presents a model that kinematically correlates the locator uncertainty, the form deviation on the part datum surface in contact with the locators and the volumetric uncertainty of the machine tool, with the geometric deviations of a surface due to a drilling or milling process. An analytical model was developed in a Matlab® file to simulate the surface geometrical deviations from nominal during drilling or milling. It is new as regards the state of the art because it takes into account two sources of uncertainty. This numerical approach allows for avoiding experimental tests, with a resultant saving of time, energy and material. It was applied to drilling, face milling and contouring processes. It was proved that machine tool volumetric uncertainty influences the form deviation of the machined surface, while the locator configuration and the datum form deviation affect the orientation of the machined surface, as should be in reality. The proposed model allows us to take into account geometrical deviations of the part datum surfaces of 0.001 mm, location deviations in the locators of ± 0.03 mm and machine tool positional and rotational uncertainties of 0.01 mm and σd=0.01∗π180 mm, respectively.

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Sánchez-Sola, José Miguel, Moisés Batista, Jorge Salguero, Alvaro Gómez et Mariano Marcos Bárcena. « Cutting Speed-Feed Based Parametric Model for Macro-Geometrical Deviations in the Dry Turning of UNS A92024 Al-Cu Alloys ». Key Engineering Materials 504-506 (février 2012) : 1311–16. http://dx.doi.org/10.4028/www.scientific.net/kem.504-506.1311.

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This work reports on the results of a study of different macro-geometrical deviation parameters, such as Straightness (SD), Parallelism (PD) and Circularity (CD) as a function of cutting speed (v) and feed (f) of dry turned UNS A92024 (Al-Cu) cylindrical bars. The results obtained have allowed establishing exponentials parametric model for predicting these deviations as a function of those cutting parameters. As a consequence of that, geometrical surfaces SD(f,v), PD(f,v) and CD(f,v) have been developed for this alloy. These surfaces allows determining marginal curves for specific v and f values, respectively, out the parameter ranges employed. So, macro-geometrical deviations can be predicted through this model for v and f values out of those considered in the study for each alloys.

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Dash, Satabdee, et Axel Nordin. « TOWARDS REALISTIC NUMERICAL MODELLING OF THIN STRUT-BASED 3D-PRINTED STRUCTURES ». Proceedings of the Design Society 3 (19 juin 2023) : 3591–600. http://dx.doi.org/10.1017/pds.2023.360.

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AbstractThe as-built geometry and material properties of parts manufactured using Additive Manufacturing (AM) can differ significantly from the as-designed model and base material properties. These differences can be more pronounced in thin strut-like features (e.g., in a lattice structure), making it essential to incorporate them when designing for AM and predicting their structural behaviour. Therefore, the aim of this study is to develop a numerical model with realistic characteristics based on a thin strut-based test artefact and to use it accurately for estimating its compressive strength. Experiments on test samples produced by selective laser sintering in PA 1101, are used to calculate geometrical deviations, Young's modulus, and yield strength, which are used to calibrate the numerical model. The experimental and numerical results show that the numerical model incorporating geometrical and material deviations can accurately predict the peak load and the force-displacement behaviour. The main contributions of this paper include the design of the test artefact, the average geometrical deviation of the struts, the measured material data, and the developed numerical model.

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Zhao, Binbin, Yunlong Wang, Qingchao Sun, Yuanliang Zhang, Xiao Liang et Xuewei Liu. « Monomer model : an integrated characterization method of geometrical deviations for assembly accuracy analysis ». Assembly Automation 41, n^o 4 (26 juin 2021) : 514–23. http://dx.doi.org/10.1108/aa-11-2020-0165.

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Purpose Assembly accuracy is the guarantee of mechanical product performance, and the characterization of the part with geometrical deviations is the basis of assembly accuracy analysis. Design/methodology/approach The existed small displacement torsors (SDT) model cannot fully describe the part with multiple mating surfaces, which increases the difficulty of accuracy analysis. This paper proposed an integrated characterization method for accuracy analysis. By analyzing the internal coupling relationship of the different geometrical deviations in a single part, the Monomer Model was established. Findings The effectiveness of the Monomer Model is verified through an analysis of a simulated rotor assembly analysis, and the corresponding accuracy analysis method based on the model reasonably predicts the assembly deviation of the rotor. Originality/value The Monomer Model realizes the reverse calculation of assembly deformation for the first time, which can be used to identify the weak links that affect the assembly accuracy, thus support the accuracy improvement in the re-assembly stage.

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Liu, Xueshu, Yuxing Yang, Li Huang, Ping Zhang et Hang Gao. « Numerical Analysis of the Influences of Geometrical Deviation on Delamination in Composite Laminates around the Countersunk Hole ». International Journal of Aerospace Engineering 2018 (2018) : 1–11. http://dx.doi.org/10.1155/2018/5061948.

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During countersunk hole machining, defects like geometrical deviation of the chamfer angle and delamination are easily introduced into the structure. To investigate the influences of geometrical deviation on delamination propagation around the countersunk hole during assembly, a progressive damage model (PDM) combining cohesive element was proposed and validated. Numerical analyses were then carried out to study delamination propagation behavior under the influences of geometrical parameters including delamination factor, chamfer angle, and location of delamination. The results show that when delamination appears at the transition area of the countersunk hole, the load causing the delamination evolution is much smaller than other cases.

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Kwintarini, Widyanti, Agung Wibowo et Yatna Yuwana Martawirya. « Mathematical Approach for Geometric Error Modeling of Three Axis CNC Vertical Milling Machine ». Applied Mechanics and Materials 842 (juin 2016) : 303–10. http://dx.doi.org/10.4028/www.scientific.net/amm.842.303.

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The aim of this paper overviews about to find out the errors that come from three axis CNC vertical milling machine. The errors come from, the CNC milling machine can be modelled into mathematical models and later on these error models will be used to analyse the errors in the measured data. Many errors from CNC machine tools have given significant effects toward the accuracy and repeatability of manufacturing process. There are two error sources come from CNC machine tools such as tool deflection and thermal distortions of machine tool structure. These errors later on will contribute to result in the geometrical deviations of moving axis in CNC vertical milling machine. Geometrical deviations of moving axis such as linear positioning errors, roll, pitch and yaw can be designated as volumetric errors in three axis machine tool. Geometrical deviations of moving axises happen at every axis in three axis CNC vertical milling machine. Geometrical deviations of moving axises in linear and angular movement has the amount of errors up to twenty one errors. Moreover, this geometrical errors play the major role in the total amount of errors and for that particular reason extra attention towards the geometrical deviation errors will be needed along machining process. Each of geometrical error of three axes vertical machining center is modeled using a homogeneous transformation matrix (HTM). The developed mathematical model is used to calculate geometrical errors at each axis and to predict the resultant error vector at the interface of machine tool and workpiece for error compensation.

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Dionisius, Felix, Sugiri ,, Tito Endramawan et Emin Haris. « Geometrical Study of Channel Profile under Incremental Forming Process : Numerical Simulation ». Journal of Mechanical Engineering 16, n^o 2 (1 août 2019) : 1–10. http://dx.doi.org/10.24191/jmeche.v16i2.15322.

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Incremental forming is one of the innovative manufacturing technologies in plate sheet forming techniques. With the incremental forming process, plate formation can be as desired and also easily applied to the manufacturing with a limited number of products. This paper is conducted to find out the smallest geometry of deviation between the design with the results of the process and the best step-down selection using a single point incremental forming (SPIF). The variable variations used in this research was 2-6 (mm) of step-down where this process uses a punch tool in the form of a hemispherical / half ball and with 2 clamps. Numerical simulation method with explicit finite element model was used as a virtual experiment with the helical shaped tool movement. The tool moves to form a blank with a size of 12x160x200 mm into a channel profile with a speed of 8 mm/s. The result showed that the deviation between the product and the design has increased from step down 2-6 mm. The smallest deviations were 3.63 mm for x axis and 12,549 mm of total depth or 4.57% for y axis with 2 mm step down parameter. Whereas for step down 4 mm had the deviation of 3.9 mm and 13.853 of total depth. But for step down 6 mm had failed / damaged.

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Xu, Bin, So Ito, Yuki Shimizu et Wei Gao. « Eccentric Error Compensation for Pitch Deviation Measurement of Gears ». Key Engineering Materials 523-524 (novembre 2012) : 853–58. http://dx.doi.org/10.4028/www.scientific.net/kem.523-524.853.

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An eccentric error compensation method is presented for the pitch deviation measurement of gears. The eccentric error compensation method mainly consists of the evaluation of the assembly accuracy, the reconstruction of the reference curve and the coordinate compensation of intersection points. The geometrical model of the measurement system was analyzed and the corresponding mathematical model was proposed. A gear with small modulus was adopted as the specimen for the pitch deviation measurement. Experimental results reveal that the values of eccentricity can be extracted from the measured profile successfully and the eccentric error compensation is effective for the pitch deviation measurement of gears.

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Strauss, Yosef, Lawrence P. Horwitz, Jacob Levitan et Asher Yahalom. « Canonical Transformation of Potential Model Hamiltonian Mechanics to Geometrical Form I ». Symmetry 12, n^o 6 (14 juin 2020) : 1009. http://dx.doi.org/10.3390/sym12061009.

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Using the methods of symplectic geometry, we establish the existence of a canonical transformation from potential model Hamiltonians of standard form in a Euclidean space to an equivalent geometrical form on a manifold, where the corresponding motions are along geodesic curves. The advantage of this representation is that it admits the computation of geodesic deviation as a test for local stability, shown in recent previous studies to be a very effective criterion for the stability of the orbits generated by the potential model Hamiltonian. We describe here an algorithm for finding the generating function for the canonical transformation and describe some of the properties of this mapping under local diffeomorphisms. We give a convergence proof for this algorithm for the one-dimensional case, and provide a precise geometric formulation of geodesic deviation which relates the stability of the motion in the geometric form to that of the Hamiltonian standard form. We apply our methods to a simple one-dimensional harmonic oscillator and conclude with a discussion of the relation of bounded domains in the two representations for which Morse theory would be applicable.

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Podshivalov, I. I. « Stress-strain state model of building metal frame made of tube trusses and bar joists with regard to geometrical imperfections ». Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture 26, n^o 1 (23 février 2024) : 118–26. http://dx.doi.org/10.31675/1607-1859-2024-26-1-118-126.

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The paper studies the metal frame industrial building during the reconstruction of its bar joists having imperfections in the form of non-uniform geometric deviations from the vertical position.Purpose: The aim of this work is to calculate the allowable value of horizontal deviation of bar joists from the vertical position.Methodology: The computational justification of using roof bar joists with regard to geometric imperfections in the reconstruction of the industrial building, is provided by modeling the stress-strain state of the metal frame in Ing + 2021, MicroFe software using the finite element model.Research findings: The limiting value of the geometric deviation from the bar joist plane, at which their vertical position or replacement is not required, is justified by calculation.

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Frumuşanu, Gabriel, et Alexandru Epureanu. « Part Accuracy Management by Topological Mapping of Deviations ». Applied Mechanics and Materials 859 (décembre 2016) : 210–16. http://dx.doi.org/10.4028/www.scientific.net/amm.859.210.

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Despite modern manufacturing processes are characterized by a continuously increasing accuracy, geometric deviations inherently appear on every manufactured part so, for quality-aware companies, it is essential to control and to manage them. This paper introduces a new type of part geometrical model, namely the part topological map, in connection with a new approach in part accuracy management. The part topological map enables a global analytical & synthetic approach of the problems related to tolerancing domain and a generalization of the “part accuracy” concept. The part geometry is seen as a stand-alone ensemble of surfaces dimensionally related, unitary and with its own shape, dimensions and position. The real geometry has also a global, unitary deviation, characterized through deviation features. Each component surface is represented in a particular manner, unrolled, while its deviation features are assessed by using series expansion of the deviations corresponding to a cloud of measured points. A method for effectively realizing the topological map of a part deviation and a numerical exercise to illustrate the method application in a concrete case are also included.

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Xu, Xun, Haidong Yu, Yunyong Li et Xinmin Lai. « Compliant assembly deviation analysis of large-scale thin-walled structures in different clamping schemes via ANCF ». Assembly Automation 40, n^o 2 (3 novembre 2019) : 305–17. http://dx.doi.org/10.1108/aa-01-2019-0018.

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Purpose The structure stiffness is greatly affected by the fixture constraints during assembly due to the flexibility of large-scale thin-walled structures. The compliant deformation of structures is usually not consistent for the non-uniform stiffness in various clamping schemes. The purpose of this paper is to investigate the correlation between the assembly quality and the clamping schemes of structures with various initial deviations and geometrical parameters, which is based on the proposed irregular quadrilateral plate element via absolute nodal coordinate formulation (ANCF). Design/methodology/approach Two typical clamping schemes are specified for the large-scale thin-walled structures. Two typical deviation modes are defined in both free and clamping states in the corresponding clamping schemes. The new irregular quadrilateral plate element via ANCF is validated to analyze the compliant deformation of assembled structures. The quasi-static force equilibrium equations are extended considering the factors of clamping constraints and geometric deviations. Findings The initial deviations and geometrical parameters strongly affect the assembly deviations of structures in two clamping schemes. The variation tendencies of assembly deviations are demonstrated in details with the circumferential clamping position and axial clamping position in two clamping schemes, providing guidance to optimize the fixture configuration. The assembly quality of structures with deviations can be improved by configuration synthesis of the clamping schemes. Originality/value Typical over-constraint clamping schemes and deviation modes in clamping states are defined for large-scale thin-walled structures. The plate element via ANCF is extended to analyze the assembly deviations of thin-walled structures in various clamping schemes. Based on the proposed theoretical model, the effects of clamping schemes and initial deviations on the deformation and assembly deviation propagation of structures are investigated.

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Jalid, Abdelilah, Said Hariri et Jean Paul Senelaer. « Estimation of form deviation and the associated uncertainty in coordinate metrology ». International Journal of Quality & ; Reliability Management 32, n^o 5 (5 mai 2015) : 456–71. http://dx.doi.org/10.1108/ijqrm-06-2012-0087.

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Purpose – The uncertainty evaluation for coordinate measuring machine metrology is problematic due to the diversity of the parameters that can influence the measurement result. From discrete coordinate data taken on curve (or surface) the software of these machines proceeds to an identification of the measured feature, the parameters of the substitute feature serve in the phase of calculation to estimate the form error of form, and the decisions made based on the result measurement may be outliers when the uncertainty associated to the measurement result is not taken into account. The paper aims to discuss these issues. Design/methodology/approach – The authors relied on the orthogonal distance regression (ODR) algorithm to estimate the parameters of the substitute geometrical elements and their uncertainties. The solution of the problem is resolved by an iterative calculation according to the Levenberg Marquard optimization method. The authors have also presented in this paper the propagation model of uncertainties to the circularity error. This model is based on the law of propagation of the uncertainties defined in the GUM. Findings – This work proposes a model based on ODR to estimates parameters of the substitute geometrical elements and their uncertainties. This contribution allows us to estimate the uncertaintof the form error by applying the law of propagation of uncertainties. An example of calculating the circularity error and the associated uncertainty is explained. This method can be applied to others geometry type: line, plan, sphere, cylinder and cone. Practical implications – This work interested manufacturing firms by allowing them: to meet the normative, which requires that each measurement must be accompanied by its uncertainty-in conformity assessment, the decision-making must take account of this uncertainty to avoid the aberrant decisions. Informing the operators on the capability of their measurement process Originality/value – This work proposes a model based on ODR to estimates parameters of the substitute geometrical elements and its uncertainties. without the hypothesis of small displacements torsor, this method integrates the uncertainty on the coordinates of points and can be applied in any reference placemark. This contribution allows us also to estimate the uncertainty of the form error by applying the law of propagation of uncertainties.

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Dey, Indira, Sergei Egorov, Fabian Soffel et Konrad Wegener. « Model-Based Heat Input Control Validated on Martensitic Steel 1.4313 ». Key Engineering Materials 969 (12 décembre 2023) : 49–56. http://dx.doi.org/10.4028/p-vbabf9.

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The ability of direct metal deposition (DMD) to fabricate complex geometries is still limited. Especially in thin-walled structures heat accumulation can lead to intolerable geometric deviation and which has to be avoided. Combining thin walls and massive sections in one layer requires parameter adapting for each section within a layer. An existing semi-empirical model predicts the optimal process parameters for the austenitic steel 1.4404. This study demonstrates the validity of the model for martensitic steel 1.4313 by an experimental campaign. The demonstrators are characterized by a massive inner part attached to a thin-walled rib. They were fabricated by DMD using constant and adapted heat input and were qualified by visual inspection, geometrical accuracy, Vickers hardness, and microstructure analysis. The demonstrators built with the adapted laser power showed enhanced geometrical accuracy which is essential for post-processing. The hardness along the symmetry plane was significantly increased, especially in the thin wall section. The study confirms the applicability of the model for martensitic steel in terms of geometrical accuracy but identifies perspectives to integrate microstructural aspects into the model.

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Stark, Sibylle, Martin Beutner, Falk Lorenz, Thomas Lampke, Bernhard Karpuschewski et Thorsten Halle. « Experimental and Numerical Determination of Cutting Forces and Temperatures in Gear Hobbing ». Key Engineering Materials 504-506 (février 2012) : 1275–80. http://dx.doi.org/10.4028/www.scientific.net/kem.504-506.1275.

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Hobbing is one of the most productive methods for manufacturing external gears. According to the requirements of green manufacturing, the lubrication in gear hobbing has to be reduced with the final aim of dry machining. Influences due to thermal aspects during machining have to be considered, especially in hobbing of large modules or ring gears, because in this case, hobbing could be the last step in the process chain. Within the priority program (SPP) “Modeling, Simulation and Compensation of Thermal Effects for Complex Machining Processes”, founded by the DFG, special emphasis is laid on the thermally caused geometrical deviation in dry cutting. To predict the heat flux, which leads to thermal expansions and geometrical deviations of the gear, a validated model for forces and temperatures is necessary. The validation of single generation positions and chips is focused in this paper.

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Mühlstädt, Mike, Wolfgang Seifert, Matthias ML Arras, Stefan Maenz, Klaus D. Jandt et Jörg Bossert. « An advanced geometrical model for laminated woven fabrics using Lamé exponents with enhanced accuracy ». Journal of Composite Materials 52, n^o 11 (23 août 2017) : 1443–55. http://dx.doi.org/10.1177/0021998317725570.

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Three-dimensional stiffness tensors of laminated woven fabrics used in high-performance composites need precise prediction. To enhance the accuracy in three-dimensional stiffness tensor prediction, the fabric’s architecture must be precisely modeled. We tested the hypotheses that: (i) an advanced geometrical model describes the meso-level structure of different fabrics with a precision higher than established models, (ii) the deviation between predicted and experimentally determined mean fiber-volume fraction ( cf) of laminates is below 5%. Laminates of different cf and fabrics were manufactured by resin transfer molding. The laminates’ meso-level structure was determined by analyzing scanning electron microscopy images. The prediction of the laminates’ cf was improved by up to 5.1 vol% ([Formula: see text]%) compared to established models. The effect of the advanced geometrical model on the prediction of the laminate’s in-plane stiffness was shown by applying a simple mechanical model. Applying an advanced geometrical model may lead to more accurate simulations of parts for example in automotive and aircraft.

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Cheng, Yun Yong, Zhen Zhen Zhu et Ding Hua Zhang. « Geometrical Shape Analysis for Investment Casting Turbine Blade Based on Optical Measurement ». Applied Mechanics and Materials 365-366 (août 2013) : 716–19. http://dx.doi.org/10.4028/www.scientific.net/amm.365-366.716.

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Turbine blade is one of the key components of the aero engine. It needs to be inspected comprehensively and carefully during its production stage. The methods for investment turbine blade geometrical shape analysis based on optical scanning measurement were presented, including optical measurement data collection, blade model reliable alignment and geometrical shape deviation fast calculation and visualization. Real measurement data from a structure light measurement device for a turbine blade was used to validate the discussed methods.

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Tarraf, Walid, Diogo Queiros-Condé, Patrick Ribeiro et Rafik Absi. « Fractal Geometric Model for Statistical Intermittency Phenomenon ». Entropy 25, n^o 5 (3 mai 2023) : 749. http://dx.doi.org/10.3390/e25050749.

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The phenomenon of intermittency has remained a theoretical concept without any attempts to approach it geometrically with the use of a simple visualization. In this paper, a particular geometric model of point clustering approaching the Cantor shape in 2D, with a symmetry scale θ being an intermittency parameter, is proposed. To verify its ability to describe intermittency, to this model, we applied the entropic skin theory concept. This allowed us to obtain a conceptual validation. We observed that the intermittency phenomenon in our model was adequately described with the multiscale dynamics proposed by the entropic skin theory, coupling the fluctuation levels that extended between two extremes: the bulk and the crest. We calculated the reversibility efficiency γ with two different methods: statistical and geometrical analyses. Both efficiency values, γstat and γgeo, showed equality with a low relative error margin, which actually validated our suggested fractal model for intermittency. In addition, we applied the extended self-similarity (E.S.S.) to the model. This highlighted the intermittency phenomenon as a deviation from the homogeneity assumed by Kolmogorov in turbulence.

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Zhi, Junnan, Yanlong Cao, Tukun Li, Anwer Nabil, Fan Liu, Xiangqian Jiang et Jiangxin Yang. « A digital twin-based analysis method to assess geometric variations for parts in batch production ». Digital Twin 3 (24 août 2023) : 7. http://dx.doi.org/10.12688/digitaltwin.17863.1.

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Background: In mass production, engineers are more concerned with the statistical distribution accuracy of parts in mass production rather than just the qualification of individual parts. However, currently, the statistical analysis methods designed for product accuracy are relatively scattered, and most of them focus on nominal part models. Therefore, there is a need to design a statistical analysis method for parts in mass production based on the Digital Twin model. Methods: This paper presents a novel method to analyse the geometric variations of parts in batch production in the production line, which is based on digital twins to model and evaluate deviations contributed by the geometrical condition, assembly condition and material condition. Firstly, the statistical descriptions of the parts, particularly the features of a digital twin for parts in batch production related to the geometry and position, are classified into various hierarchies. Secondly, a covariance method is employed to analyse the law of their shape from the descriptions. Thirdly, the parts' shape feature similarity for different terms is derived, including the linear features of pose constraint, rotation deviation, and geometric deviation and the curve features like a geometric deviation. Finally, the probability distribution of discrete points on the manufacturing error caused by different reasons is calculated. Results: Two case studies of reducer and rail highlight the applicability of the proposed approach. The standard deviation of the points has similar trend with sample cases according to normal distribution. Conclusions: This paper categorizes the deviations of batch parts into the linear features of pose constraint, rotation deviation, and geometric deviation. When batch parts exhibit any of these deviation types, the eigenvalues and eigenvectors of their covariance matrix show certain patterns, enabling the identification of the deviation type and calculation of the statistical deviation probability distribution for the corresponding features.

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Zhi, Junnan, Yanlong Cao, Tukun Li, Anwer Nabil, Fan Liu, Xiangqian Jiang et Jiangxin Yang. « A digital twin-based analysis method to assess geometric variations for parts in batch production ». Digital Twin 3 (19 décembre 2023) : 7. http://dx.doi.org/10.12688/digitaltwin.17863.2.

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Background In mass production, engineers are more concerned with the statistical distribution accuracy of parts in mass production rather than just the qualification of individual parts. However, currently, the statistical analysis methods designed for product accuracy are relatively scattered, and most of them focus on nominal part models. Therefore, there is a need to design a statistical analysis method for parts in mass production based on the Digital Twin model. >Methods This paper presents a novel method to analyse the geometric variations of parts in batch production in the production line, which is based on digital twins to model and evaluate deviations contributed by the geometrical condition, assembly condition and material condition. Firstly, the statistical descriptions of the parts, particularly the features of a digital twin for parts in batch production related to the geometry and position, are classified into various hierarchies. Secondly, a covariance method is employed to analyse the law of their shape from the descriptions. Thirdly, the parts' shape feature similarity for different terms is derived, including the linear features of pose constraint, rotation deviation, and geometric deviation and the curve features like a geometric deviation. Finally, the probability distribution of discrete points on the manufacturing error caused by different reasons is calculated. Results Two case studies of reducer and rail highlight the applicability of the proposed approach. The standard deviation of the points has similar trend with sample cases according to normal distribution. Conclusions This paper categorizes the deviations of batch parts into the linear features of pose constraint, rotation deviation, and geometric deviation. When batch parts exhibit any of these deviation types, the eigenvalues and eigenvectors of their covariance matrix show certain patterns, enabling the identification of the deviation type and calculation of the statistical deviation probability distribution for the corresponding features.

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Lopato, Przemyslaw, Michal Herbko, Paulina Gora, Ulrich Mescheder, Andras Kovacs et Alexander Filbert. « Numerical Analysis of the Influence of Fabrication Process Uncertainty on Terahertz Metasurface Quality ». Electronics 12, n^o 10 (12 mai 2023) : 2198. http://dx.doi.org/10.3390/electronics12102198.

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The purpose of this paper was to investigate the influence of fabrication process uncertainty on terahertz metasurface quality. The focus was on the effect of metasurface fabrication inaccuracy on resonances. To the best of our knowledge, this is the first paper to study the effect of the metasurface fabrication process on its resonant frequency. The terahertz split ring resonator-based metasurface is under consideration. Using a numerical model, the influence of the uncertainty of various geometrical parameters obtained during the fabrication process (mainly layer deposition, photolithography, and etching processes) is analyzed according to the resonance of the designed metasurface. The influence of the following parameters causes a shift of resonant frequencies of the considered metasurface: etching deviation e, metallization thickness tAl and SiO2 layer thickness tSiO2. The quality of the metasurface affected by the variations of obtained geometrical parameters was determined by the deviation of resonant frequency Δfr. The developed numerical model was verified by THz-TDS (terahertz time-domain spectroscopy) measurements of the fabricated structure.

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Sánchez, J. M., M. A. Sebastián, E. Rubio, Manuel Sánchez-Carrilero, L. Sevilla et Mariano Marcos Bárcena. « A Parametric Model for the Straightness Deviation in the Cutting Processes of Aluminum Alloys ». Materials Science Forum 526 (octobre 2006) : 31–36. http://dx.doi.org/10.4028/www.scientific.net/msf.526.31.

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Light alloys are increasingly applied in different industrial sectors, mainly aerospace. Because of this, it is needed to analyze their behavior in the different processing procedures and, specially, machining. On the other hand, up to a few years, cutting fluids were successfully employed in these processes since their coolant and lubricant properties. Notwithstanding, environmental necessities have promoted researches focused on the development of cleaner processes avoiding cutting fluids, in particular, dry machining. However, this process can change tool geometry and affect to the material giving rise to changes in the design specifications. In this work, geometrical deviations, particularly straightness deviations, in the dry turning of UNS A92024 (Al-Cu) alloy are studied as a function of feed and cutting speed through a parametric model.

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Zhao, Cai Qi, Jun Ma et De Lin Li. « Stability Analysis of Nantong Sports and Exhibition Center Based on Measured Geometrical Imperfections ». Advanced Materials Research 163-167 (décembre 2010) : 426–32. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.426.

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Position deviation of joints is a primary initial geometrical imperfection that affects the stability of long-span spatial structures. It makes field measurement of joint coordinate for the shell and roof initial shape of Nantong Sports Exhibition Center upon its completion. This paper researches the stochastic distribution feature and statistical parameter of geometrical imperfections for the data sources of above position deviation of joints by “abnormal data test method”. The results indicate that the distribution of abnormal data is concentrated, which is related to the difficulty of construction and condition of measurement; the distribution of joint position deviation can be assumed by normal distribution, and its mean μ=0 and mean square deviation σ=R/2 of statistical parameter are tenable. Meanwhile, It also puts forward a stochastic imperfection method based on measured imperfections and ANSYS－PDS platform, establishes a measured model to make nonlinear stability analysis, and respectively compares this critical load with that obtained by the perfect structure of ideal shape and the consistent imperfection method, so as to evaluate the stability and reliability of practical project in an objective manner, and provide reference for project design.

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Josnin, Jean-Yves, Hervé Jourde, Pascal Fénart et Pascal Bidaux. « A three-dimensional model to simulate joint networks in layered rocks ». Canadian Journal of Earth Sciences 39, n^o 10 (1 octobre 2002) : 1443–55. http://dx.doi.org/10.1139/e02-043.

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Modelling the discontinuity network of fractured reservoirs may be addressed (1) by purely stochastic means, (2) with a fractal approach, or (3) using mechanical parameters describing the spatial organisation of fracture systems. Our paper presents an approach where the geometrical properties of the fracture networks are incorporated in the form of both statistical and mechanical rules. This type of approach is particularly suitable to model stratified fractured rock masses comprising two orthogonal families of joints and a family of sedimentary discontinuities. Their geometrical arrangement is governed by two kinds of rules based on (1) statistical parameters such as the mean, standard deviation of joint length and of bed thickness, both determined by field observations, and (2) geometrical parameters that result from genetic processes inferred from field observations and analogue experiments on the nucleation and propagation mechanisms of joints. Using these parameters, we generate realistic networks in terms of the relative position of joints that control the overall network connectivity: the model enables all combinations of joint spacing and vertical persistence for orthogonal patterns ranging from ladder type to grid type patterns. It also integrates the concept of mechanical "saturation" of a bed, thereby permitting the generation of both "saturated" and "unsaturated" networks.

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Ben-Haim, Y. « Convex Models of Uncertainty in Radial Pulse Buckling of Shells ». Journal of Applied Mechanics 60, n^o 3 (1 septembre 1993) : 683–88. http://dx.doi.org/10.1115/1.2900858.

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The buckling of shells subject to radial impulse loading has been studied by many investigators, and it is well known that the severity of the buckling response is greatly amplified by initial geometrical imperfections in the shell shape. Traditionally, these imperfections have been modeled stochastically. In this study convex models provide a convenient alternative to probabilistic representation of uncertainty. Convex models are well suited to the limitations of the available information on the nature of the geometrical uncertainties. A n ellipsoidal convex model is employed and the maximum pulse response is evaluated. The ellipsoidal convex model is based on three types of information concerning the initial geometrical uncertainty of the shell: (1) which mode shapes contribute to the imperfections, (2) bounds on the relative amplitudes of these modes, and (3) the magnitude of the maximum initial deviation of the shell from its nominal shape. The convex model analysis yields reasonable results in comparison with a probabilistic analysis due to Lindberg (1992a,b). We also consider localized imperfections of the shell. Results with a localized envelope-bound convex model indicate that very small regions of localized geometrical imperfections result in buckling damage which is a substantial fraction of the damage resulting from full circumferential initial imperfection.

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Turnic, Dragana, Srdjan Zivkovic, Marija Spasojevic-Surdilovic, Marko Milosevic et Aleksandra Igic. « Influence of geometrical and structural imperfections on the behavior of steel plate girders ». Facta universitatis - series : Architecture and Civil Engineering 19, n^o 2 (2021) : 171–82. http://dx.doi.org/10.2298/fuace211130013t.

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The girders or parts of the girders are not ideally flat in terms of their geometry. The deviations that occur are defined as geometric imperfections. Also, in the material from which the girder is made, a certain deviation may occur during factory production or for some other reason, which is known as structural imperfection. This paper presents the analysis of the behavior of plate girders (welded steel I girders), with and without material stiffening and loaded with patch loading. The results were obtained by numerical simulation in the ANSYS for models with included geometric imperfections. The model was performed in accordance with the recommendations for different behavior curves of materials from Eurocode 3. The limit load obtained by numerical simulation corresponded to the experimental results from the literature. Stress values for girders with and without geometric imperfections for the same load value were compared.

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Liu, Feng Lin, Quan Kang et Bing He. « Permissible Deviation of Rotation Center Based on Fan-Beam Projection ICT System ». Advanced Materials Research 452-453 (janvier 2012) : 21–30. http://dx.doi.org/10.4028/www.scientific.net/amr.452-453.21.

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For ICT wide fan-beam scanning, there is a geometrical supposition that the object rotation center and the radiation source center intersect the image reconstruction center. In practice, the existing intersection deviation has influence on the image reconstruction precision. The image reconstruction mathematical model for shifted rotation center was established, and the relationship between the deviation error and reconstructed image precision was studied by simulation. As a result, for 512×512 CT reconstructed image, there is no distinctive difference between the reference image and the reconstructed image with eccentricity 0.1 pixels; however, with 0.2 pixels or more, the difference is obvious. So, for 512×512 CT image, the maximum permissible deviation of the rotation center is within 0.1 pixel dimension.

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Vale, Cecília, et Isabel M. Ribeiro. « RAILWAY CONDITION-BASED MAINTENANCE MODEL WITH STOCHASTIC DETERIORATION ». JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 20, n^o 5 (10 octobre 2014) : 686–92. http://dx.doi.org/10.3846/13923730.2013.802711.

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The application of mathematical programming for scheduling preventive maintenance in railways is relatively new. This paper presents a stochastic mathematical model designed to optimize and to predict tamping operations in ballasted tracks as preventive condition-based maintenance. The model is formulated as a mixed 0–1 nonlinear program that considers real technical aspects as constraints: the reduction of the geometrical track quality over time is characterized by the deterioration rate of the standard deviation of the longitudinal level; the track layout; the dependency of the track recovery on its quality at the moment of the maintenance operation; the limits for preventive maintenance that depend on the maximum permissible train speed. In the model application, a railway stretch with 51.2 km of length is analysed for a time period of five years. The deterioration model is stochastic and represents the reduction of the standard deviation of the longitudinal level over time. The deterioration rate of the standard deviation of the longitudinal level is simulated by Monte Carlo techniques, considering the three parameters Dagum probabilistic distribution fitted with real data (Vale, Simões 2012). Two simulations are performed and compared: stochastic simulation in space; stochastic simulation in space and time. The proposed condition-based maintenance model is able to produce optimal schedules within appropriate computational times.

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Chen, Fei, Ming Li et Peng Zhang. « Distribution of Energy Density and Optimization on the Surface of the Receiver for Parabolic Trough Solar Concentrator ». International Journal of Photoenergy 2015 (2015) : 1–10. http://dx.doi.org/10.1155/2015/120917.

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The geometrical optics model about the offset effect of solar rays by the thickness of concentrating mirror and the diametric solar model were established. The radiant flux density on the surface of the receiver for parabolic trough solar concentrator was obtained by numerical calculation with the established models. Charge-coupled device (CCD) was used for testing gray image on the surface of the receiver for parabolic trough solar concentrator. The image was analyzed by Matlab and the radiant flux density on the surface of the receiver for parabolic trough solar concentrator was achieved. It was found that the result of the theory is consistent with that of the experiment, and the relative deviation on the focal length width was 8.7%. The geometrical structure of receiver based on parabolic trough solar concentrator was optimized, a new parabolic receiver has been proposed, and it has been shown that the optimized geometrical structure of receiver was beneficial to improve the working performance of the entire system.

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Chuang, Xihong, Sanqi Li, Yingtao Hu et Xin Zhou. « Impact of Geometrical Features on Solute Transport Behavior through Rough-Walled Rock Fractures ». Water 15, n^o 1 (29 décembre 2022) : 124. http://dx.doi.org/10.3390/w15010124.

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The solute transport in the fractured rock is dominated by a single fracture. The geometric characteristics of single rough-walled fractures considerably influence their solute transport behavior. According to the self-affinity of the rough fractures, the fractal model of single fractures is established based on the fractional Brownian motion and the successive random accumulation method. The Navier–Stokes equation and solute transport convective-dispersion equation are employed to analyze the effect of fractal dimension and standard deviation of aperture on the solute transport characteristics. The results show that the concentration front and streamline distribution are inhomogeneous, and the residence time distribution (RTD) curves have obvious tailing. For the larger fractal dimension and the standard deviation of aperture, the fracture surface becomes rougher, aperture distribution becomes more scattered, and the average flow velocity becomes slower. As a result, the average time of solute transport is a power function of the fractal dimension, while the time variance and the time skewness present a negative linear correlation with the fractal dimension. For the standard deviation of aperture, the average time exhibits a linearly decreasing trend, the time variance is increased by a power function, and the skewness is increased logarithmically.

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Rahman, M. A., A. B. Baharudin, S. Adi, Nur Izan Syahriah Hussein, H. Isa, R. I. F. Elfi et M. N. Azureen. « Dimensional Deviation Affected by Cutting Parameters and Machine Tool Rigidity in Dry Turning of S45C Steel ». Applied Mechanics and Materials 315 (avril 2013) : 749–54. http://dx.doi.org/10.4028/www.scientific.net/amm.315.749.

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Performance of machining processes is assessed by dimensional and geometrical accuracy which is mentioned in this paper as dimensional deviation. A part quality does not depend solely on the depth of cut, feed rate and cutting speed. Other variable such as excessive machine tool vibration due to insufficient dynamic rigidity can be deleterious to the desired results. The focus of the present study is to find a correlation between dimensional deviation against cutting parameters and machine tool vibration in dry turning. Hence cutting parameters and vibration-based regression model can be established for predicting the part dimensional deviation. Experiments are conducted using a Computerized Numerical Control (CNC) lathe with carbide insert cutting tool. Vibration data are collected through a data acquisition system, then tested and analyzed through statistical analysis. The analysis revealed that machine tool vibration has significant effect on dimensional deviation where statistical analysis of individual regression coefficients showed p<0.05. The developed regression model has been validated through experimental tests and found to be reliable to predict dimensional deviation.

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Wang, Hao, Hamzeh A. Al Shraida et Jin Yu. « Predictive Modeling of Out-of-Plane Deviation for the Quality Improvement of Additive Manufacturing ». Materials Science Forum 1086 (27 avril 2023) : 79–83. http://dx.doi.org/10.4028/p-12034b.

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Additive manufacturing (AM) is a new technology for fabricating products straight from a 3D digital model, which can lower costs, minimize waste, and increase building speed while maintaining acceptable quality. However, it still suffers from low dimensional accuracy and a lack of geometrical quality standards. Moreover, there is a need for a robust AM configuration to perform in-situ inspections during the fabrication. This work established a 3D printing-scanning setup to collect 3D point cloud data of printed parts and then compare them with nominal 3D point cloud data to quantify the deviation in all X, Y, and Z directions. Specifically, this work aims at predicting the anticipated deviation along the Z direction by applying a deep learning-based prediction model. An experiment with regard to a human “Knee” prototype fabricated by Fused Deposition Modeling (FDM) is conducted to show the effectiveness of the proposed methods.

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Campi, Federico, Marco Mandolini, Claudio Favi, Emanuele Checcacci et Michele Germani. « An analytical cost estimation model for the design of axisymmetric components with open-die forging technology ». International Journal of Advanced Manufacturing Technology 110, n^o 7-8 (29 août 2020) : 1869–92. http://dx.doi.org/10.1007/s00170-020-05948-w.

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Abstract Open-die forging is a manufacturing process commonly used for realising simple shaped components with high mechanical performances and limited capability in terms of production volume. To date, an analytical model for estimating the costs of components manufactured with this technology is still an open issue. The paper aims to define an analytical model for cost estimation of axisymmetric components manufactured by open-die forging technology. The model is grounded on the analysis of geometrical features available at the design stage providing a detailed cost breakdown in relation to all the process phases and the raw material. The model allows predicting product cost, linking geometrical features and cost items, to carry out design-to-cost actions oriented to the reduction of manufacturing cost. The model is mainly conceived for design engineers, cost engineers and buyers, respectively, for improving the product design, the manufacturing process and the supply chain. Cost model and related schemas for collecting equations and data are presented, including the approach for sizing the raw material and a set of rules for modelling the related cost. Finally, analytic equations for modelling the cost of the whole forging process (i.e. billet cutting, heating, pre-smoothing, smoothing, upsetting, max-shoulder cogging, necking and shoulders cogging) are reported. The cost model has been tested on eight cylindrical parts such as discs and shafts with different shapes, dimensions and materials. Two forge masters have been involved in the testing phase. The absolute average deviation between the actual and estimated costs is approximately 4% for raw material and 21% for the process. The absolute average deviation on the total cost (raw material and manufacturing process) is approximately 5%.

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Bolotov, Mikhail, Iliya Grachev et Evgeny Kudashov. « Investigation of parts assembly error, taking into account the deviation of the shape of their surfaces ». MATEC Web of Conferences 224 (2018) : 01098. http://dx.doi.org/10.1051/matecconf/201822401098.

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In this article, we study the errors in the assembly of parts, taking into account the deviation of the shape of their surfaces. The developed computer model of the assembly of the engine low-pressure turbine rotor is designed to predict the values of the assembly parameters, such as radial and face run-out. The forecasting of the above assembly parameters is carried out based on the data of actual dimensions and shape of the surfaces of parts assembled as an assembly unit. The analysis of study results made it possible to obtain a conclusion about the qualitative influence of geometrical errors of the assembled parts on the error of the assembly parameters.

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Benavent-Nácher, Sergio, Pedro Rosado Castellano et Fernando Romero Subirón. « SysML4GDPSim : A SysML Profile for Modeling Geometric Deviation Propagation in Multistage Manufacturing Systems Simulation ». Applied Sciences 14, n^o 5 (23 février 2024) : 1830. http://dx.doi.org/10.3390/app14051830.

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In recent years, paradigms like production quality or zero-defect manufacturing have emerged, highlighting the need to improve quality and reduce waste in manufacturing systems. Although quality can be analyzed from various points of view during different stages of a manufacturing system’s lifecycle, this research focuses on a multidomain simulation model definition oriented toward the analysis of productivity and geometric quality during early design stages. To avoid inconsistencies, the authors explored the definition of descriptive models using system modeling language (SysML) profiles that capture domain-specific semantics defining object constraint language (OCL) rules, facilitating the assurance of model completeness and consistency regarding this specific knowledge. This paper presents a SysML profile for the simulation of geometric deviation propagation in multistage manufacturing systems (SysML4GDPSim), containing the concepts for the analysis of two data flows: (a) coupled discrete behavior simulation characteristic of manufacturing systems defined using discrete events simulation (DEVS) formalism; and (b) geometric deviation propagation through the system based on the geometrical modeling of artifacts using concepts from the topologically and technologically related surfaces (TTRS) theory. Consistency checking for this type of multidomain simulation model and the adoption of TTRS for the mathematical analysis of geometric deviations are the main contributions of this work, oriented towards facilitating the collaboration between design and analysis experts in the manufacturing domain. Finally, a case study shows the application of the proposed profile for the simulation model of an assembling line, including the model’s transformation to Modelica and some experimental results of this type of analysis.

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Thuan, Vo Van. « Klein-Gordon-Fock equation from Einstein general relativity ». Communications in Physics 26, n^o 2 (27 septembre 2016) : 181. http://dx.doi.org/10.15625/0868-3166/26/2/7866.

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A time-space symmetry based cylindrical model of geometrical dynamics was proposed. Accordingly, the solution of Einstein gravitational equation in vacuum has a duality: an exponential solution and a wave-like one. The former leads to a "microscopic" cosmological model with Hubble expansion. Due to interaction of a Higgs-like cosmological potential, the original time-space symmetry is spontaneously broken, inducing a strong time-like curvature and a weak space-like deviation curve. In the result, the wave-like solution leads to Klein-Gordon-Fock equation which would serve an explicit approach to the problem of consistency between quantum mechanics and general relativity.

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Kang, Hehe, et Zhi-Min Li. « Assembly research of aero-engine casing involving bolted connection based on rigid-compliant coupling assembly deviation modeling ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 234, n^o 14 (4 mars 2020) : 2803–20. http://dx.doi.org/10.1177/0954406220910455.

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Assembly analysis is necessary for mechanical product to optimize design and improve the product quality since assembly deviation is the key factor affecting the assembly quality. In this paper, the rigid-compliant assembly of thin-walled aero-engine casing is studied to evaluate the assembly quality at the design stage. First, the Jacobian–Torsor model is proposed to construct multistage casing assembly owing to its effectiveness to express assembly deviation. The torsor expression is modified and expanded to present the rigid-compliant coupling tolerance. Then, the partial parallel chain is addressed via combination operation. By using extremum and statistical method, the tolerance zone and the distribution of the objective deviation are obtained. Furthermore, to study the effect of specified compliant deviation on statistical distribution, the bolt looseness and positional deformation are investigated to provide an effective means for geometric deviation and connecting joints of aero-engine casing components of precision assembly. The presented method can address compliant deformation tolerance and geometrical manufacturing tolerance together, and is reliable for casing assembly to predict assembly quality at the design stage. In addition, it also has a great significance to guide tolerance design and product optimization.

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Mesri, Yaser, Hamid Niazmand, Amin Deyranlou et Mahmood Reza Sadeghi. « Fluid-structure interaction in abdominal aortic aneurysms : Structural and geometrical considerations ». International Journal of Modern Physics C 26, n^o 04 (25 février 2015) : 1550038. http://dx.doi.org/10.1142/s0129183115500382.

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Rupture of the abdominal aortic aneurysm (AAA) is the result of the relatively complex interaction of blood hemodynamics and material behavior of arterial walls. In the present study, the cumulative effects of physiological parameters such as the directional growth, arterial wall properties (isotropy and anisotropy), iliac bifurcation and arterial wall thickness on prediction of wall stress in fully coupled fluid-structure interaction (FSI) analysis of five idealized AAA models have been investigated. In particular, the numerical model considers the heterogeneity of arterial wall and the iliac bifurcation, which allows the study of the geometric asymmetry due to the growth of the aneurysm into different directions. Results demonstrate that the blood pulsatile nature is responsible for emerging a time-dependent recirculation zone inside the aneurysm, which directly affects the stress distribution in aneurismal wall. Therefore, aneurysm deviation from the arterial axis, especially, in the lateral direction increases the wall stress in a relatively nonlinear fashion. Among the models analyzed in this investigation, the anisotropic material model that considers the wall thickness variations, greatly affects the wall stress values, while the stress distributions are less affected as compared to the uniform wall thickness models. In this regard, it is confirmed that wall stress predictions are more influenced by the appropriate structural model than the geometrical considerations such as the level of asymmetry and its curvature, growth direction and its extent.

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Gehring, Tim, Santiago Eizaguirre, Qihao Jin, Jan Dycke, Manuel Renschler et Rainer Kling. « On the Temperature and Plasma Distribution of an Inductively Driven Xe-I2-Discharge ». Plasma 4, n^o 4 (16 novembre 2021) : 745–54. http://dx.doi.org/10.3390/plasma4040037.

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Inductively Coupled Plasma (ICP) discharges are part of intense research. Predicting different plasma parameters, like the distribution and temperature of the present species, is of great interest for many applications. Iodine- or halide-containing plasmas in particular have an important function, for example, in the development of mercury-free UV radiation sources. Therefore, a 2D simulation model of a xenon- and iodine-containing ICP was created by using the Finite Element Method (FEM) software COMSOL Multiphysics®. The included species and the used reactions are presented in this paper. To verify the simulation in relation to the plasma distribution, the results were compared with measurements from literature. The temperature of the lamp vessel was measured in relation to the temperature distribution and also compared with the results of the simulation. It could be shown that the simulation reproduces the plasma distribution with a maximal deviation of ≈6.5% to the measured values and that the temperature distribution in the examined area can be predicted with deviations of up to ≈24% for long vessel dimensions and ≈3% for shorter dimensions. However, despite the deviating absolute values, the general plasma behaviour is reproduced by the simulation. The simulation thus offers a fast and cost-effective method to estimate an effective geometrical range of iodine-containing ICPs.

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Budzik, Grzegorz, Paweł Turek, Tomasz Dziubek et Michał Gdula. « Elaboration of the measuring procedure facilitating precision assessment of the geometry of mandible anatomical model manufactured using additive methods ». Measurement and Control 53, n^o 1-2 (2 décembre 2019) : 181–91. http://dx.doi.org/10.1177/0020294019881708.

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This article presents a procedure for minimizing ATOS II Triple Scan system measurement errors during the verification of geometrical accuracy of the final lateral-mandibular condyle model. The process of manufacturing a template geometrically similar to that of lateral-mandibular condyle was performed on the five-axis machining centre 100 DMU MonoBlock. The next stage of the research was related to the implementation of the measurement system procedure on the template model, and the 12 anatomical models of the mandibular body-condyle were manufactured using five different additive methods. As a result of the comparison of anatomical models of the mandibular body-condyle designed in reverse engineering/computer-aided design systems and manufactured using additive methods, the average results of histograms and parameters determining the accuracy of geometry of 12 models were obtained. In the case of models manufactured using fused deposition modelling, PolyJet and selective laser sintering techniques, a unimodal distribution was observed in the same way as in the template model. The best results were obtained in the case of models manufactured using selective laser sintering techniques (standard deviation = 0.06 mm). In the case of fused deposition modelling and PolyJet, a similar value of standard deviation (about 0.07 mm) was observed, despite the fact that the layer thickness for PolyJet technology was 0.016 mm. In the case of melted and extruded modelling and ColorJet Printing technologies, there was a bimodal distribution. Through the implementation of own template and measurement method, it will be easier to estimate errors in the manufacturing of anatomical models of lateral-mandibular condyle part. As a result, medical models, surgical templates and implants will be manufactured more accurately and precisely, which will significantly reduce intraoperative complications during the surgical procedure in this area.

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Shu, Q., L. Wang et K. C. Chou. « Estimation of viscosity for some silicate ternary slags ». Journal of Mining and Metallurgy, Section B : Metallurgy 50, n^o 2 (2014) : 139–44. http://dx.doi.org/10.2298/jmmb130218014s.

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A new method, combining KTH model with geometrical model (General solution model by Chou) to estimate viscosity of some ternary silicate slags, was proposed in this work. According to modified KTH model, viscous Gibbs free energy for mixing of ternary slags was estimated by employing general solution model. It was found that viscous Gibbs energy for mixing of ternary system could be calculated using solely viscous Gibbs energy for mixing of sub-binary systems. The viscosities of five ternary slags CaO-MnO-SiO2, CaO-FeO-SiO2, FeO-MnO-SiO2, CaO-MgO-SiO2 and FeO-MgO-SiO2 were estimated in the present work. A good agreement with available experimental data, with mean deviation less than 20%, was achieved. The modified KTH model has advantages with less model parameters and improved estimation ability by comparison to original KTH model.

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Xiao, Zhaofei, Xiaoling Liu, Lee T. Harper, Andreas Endruweit et Nicholas A. Warrior. « Modelling the permeability of random discontinuous carbon fibre preforms ». Journal of Composite Materials 54, n^o 20 (28 janvier 2020) : 2739–51. http://dx.doi.org/10.1177/0021998320902506.

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A force-directed algorithm was developed to create representative geometrical models of fibre distributions in directed carbon fibre preforms. Local permeability values were calculated for the preform models depending on the local fibre orientation, distribution and volume fraction. The effect of binder content was incorporated by adjusting the principal permeability values of the meso-scale discontinuous fibre bundles, using corresponding experimental data obtained for unidirectional non-crimp fabrics. The model provides an upper boundary for the permeability of directed carbon fibre preform architectures, where predictions are within one standard deviation of the experimental mean for all architectures studied.

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Chen, Jian, Xiao Zhang, Cong Li, Xinyuan Zhang, Yanjie Ren, Jianjun He et Jianlin Chen. « Calculation Method of Specific Surface Area of Foam Metal Based on an Ideal Tetradecahedron Model for Lithium Ion Battery ». International Journal of Photoenergy 2020 (28 janvier 2020) : 1–7. http://dx.doi.org/10.1155/2020/2478579.

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A novel calculation method of specific surface area of tetrahedral foam metal is established. The expressions of the two basic parameters of the foam metal with respect to porosity and pore size are derived by using the geometrical relationship of this model; consequently, the specific surface area of the metal foam is easily calculated. The theoretical calculation data are compared with the experimental results; it shows that the specific surface area of various porous metals, such as nickel foam and copper foam prepared by electrodeposition and aluminum foam produced by high-pressure infiltration casting, can be well calculated by the formula proposed in this paper. Compared with other similar equations, the calculation results of this method possess lower deviation and greater practicability.

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Pucci, Micol, Stefania Zanforlin, Debora Bellafiore, Stefano Deluca et Georg Umgiesser. « A Double Multiple Stream Tube (DMST) routine for site assessment to select efficient turbine aspect ratios and solidities in real marine environments ». E3S Web of Conferences 312 (2021) : 08001. http://dx.doi.org/10.1051/e3sconf/202131208001.

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A MATLAB routine, based on a Double Multiple Stream Tube model, developed to quickly predict the performance of cross-flow hydrokinetic turbine, here is presented. The routine evaluate flow data obtained with the open-source marine circulation code SHYFEM. The tool can establish the best locations to place tidal devices taking into account bathymetric constraints and the hydrokinetic potential. Hence, it can be used to decide the best set of geometrical parameters. The geometrical variables of our analysis are turbine frontal area, aspect ratio and solidity. Several sub-models, validated with 3D and 2D CFD simulations, reproduce phenomena such as dynamic stall, fluid dynamic tips losses and the lateral deviation of streamlines approaching the turbine. As a case study, the tool is applied to an area of the northern Adriatic Sea. After having identified some suitable sites to exploit the energy resource, we have compared behaviours of different turbines. The set of geometrical parameters that gives the best performance in terms of power coefficient can vary considering several locations. Conversely, the power production is always greater for turbine with low aspect ratio (for a fixed solidity and area). Indeed, shorter devices benefit from higher hydrokinetic potentials at the top of the water column.

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Jumelet, J., S. Bekki, C. David et P. Keckhut. « Statistical estimation of stratospheric particle size distribution by combining optical modelling and lidar scattering measurements ». Atmospheric Chemistry and Physics 8, n^o 17 (10 septembre 2008) : 5435–48. http://dx.doi.org/10.5194/acp-8-5435-2008.

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Abstract. A method for estimating the stratospheric particle size distribution from multiwavelength lidar measurements is presented. It is based on matching measured and model-simulated backscatter coefficients. The lidar backscatter coefficients measured at the three commonly used wavelengths 355, 532 and 1064 nm are compared to a precomputed look-up table of model-calculated values. The optical model assumes that particles are spherical and that their size distribution is unimodal. This inverse problem is not trivial because the optical model is highly non-linear with a strong sensitivity to the size distribution parameters in some cases. The errors in the lidar backscatter coefficients are explicitly taken into account in the estimation. The method takes advantage of the statistical properties of the possible solution cluster to identify the most probable size distribution parameters. In order to discard model-simulated outliers resulting from the strong non-linearity of the model, solutions farther than one standard deviation of the median values of the solution cluster are filtered out, because the most probable solution is expected to be in the densest part of the cluster. Within the filtered solution cluster, the estimation algorithm minimizes a cost function of the misfit between measurements and model simulations. Two validation cases are presented on Polar Stratospheric Cloud (PSC) events detected above the ALOMAR observatory (69° N – Norway). A first validation is performed against optical particle counter measurements carried out in January 1996. In non-depolarizing regions of the cloud (i.e. spherical particles), the parameters of an unimodal size distribution and those of the optically dominant mode of a bimodal size distribution are quite successfully retrieved, especially for the median radius and the geometrical standard deviation. As expected, the algorithm performs poorly when solid particles drive the backscatter coefficient. A small bias is identified in modelling the refractive index when compared to previous works that inferred PSC type Ib refractive indices. The accuracy of the size distribution retrieval is improved when the refractive index is set to the value inferred in the reference paper. Our results are then compared to values retrieved with another similar method that does not account for the effect of the measurements errors and the non-linearity of the optical model on the likelihood of the solution. The case considered is a liquid PSC observed over northern Scandinavia on January 2005. An excellent agreement is found between the two methods when our algorithm is applied without any statistical filtering of the solution cluster. However, the solution for the geometrical standard deviation appears to be rather unlikely with a value close to unity (σ≈1.04). When our algorithm is applied with solution filtering, a more realistic value of the standard deviation (σ≈1.27) is found. This highlights the importance of taking into account the non linearity of the model together with the lidar errors, when estimating particle size distribution parameters from lidar measurements.

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Chlost, Michał, et Michał Gdula. « A New Method of the Positioning and Analysis of the Roughness Deviation in Five-Axis Milling of External Cylindrical Gear ». Acta Mechanica et Automatica 16, n^o 3 (15 juin 2022) : 207–14. http://dx.doi.org/10.2478/ama-2022-0025.

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Abstract Five-axis milling is a modern, flexible and constantly developing manufacturing process, which can be used for the machining of external cylindrical gears by means of cylindrical end mills and special disc mills on universal multi-axis machining centres. The article presents a new method of positioning the tip and the axis of the end mill and the disc cutter in order to ensure a constant value of deviation of the theoretical roughness Rth along the entire length of the tooth profile. The first part presents a mathematical model of the five-axis milling process of the cylindrical gear and an algorithm for calculating the Rth deviation values. The next section describes the positioning of the end mill and the disc cutter. Then, a new method for the empirical determination of the distribution of the involute root angle Δui and the data description by means of the interpolation function are presented and described. In the conducted numerical tests, the influence of the geometrical parameters of the cylindrical gear on the deviation Rth is determined, assuming a constant Rth value in the five-axis milling process.

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Brestovič, Tomáš, Mária Čarnogurská, Miroslav Příhoda, Marián Lázár, René Pyszko et Natália Jasminská. « A Similarity Model of the Cooling Process of Fluids during Transportation ». Processes 9, n^o 5 (3 mai 2021) : 802. http://dx.doi.org/10.3390/pr9050802.

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This article presents a description of a novel method for the identification of a decrease in the temperature of a liquid medium transported by railroad tank cars. No exact analytical solution exists for this phenomenon; therefore, the authors of this article have prepared a mathematical expression for the cooling process of the transported fluid by applying a dimensional analysis, which facilitated the identification of the dimensionless criteria using the relevant dimensional parameters. A functional dependence between the criteria can be identified through a physical or numerical experiment. In this case, a database of the results from a detailed numerical model was used; however, its disadvantage is that the calculation takes much longer than in a simpler similarity model. The output of the similarity model was a function of the average temperature of the fluid at a time applicable to various alternatives in the geometrical, physical, and boundary conditions. The standard deviation of the difference between the temperatures predicted by the similarity model and those calculated by the numerical simulation Tmod − Tsim represented 4.8% relative to the simulated fluid temperature.

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