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Öğe A novel combined hardening rule for the brass cartridge case using crimping simulation and optimization(Sage Publications Ltd, 2025) Kacar, Ilyas; Yildirim, SefaA cartridge shell case, a critical component in the defence industry, undergoes a crimping process to form one end for the insertion of a bullet. The shell case is primarily composed of brass. The crimping process is simulated using a novel plasticity model that combines a hardening rule with the Hill48 yield criterion and the associated flow rule. This study focuses primarily on the hardening rule, where a bilinear isotropic hardening (BISO) and Chaboche's nonlinear kinematic hardening (CHAB) rules are combined to develop a novel hardening model. The raw parameters of the models are calculated by regression performed on the data from monotonic tensile test and low-cycle fatigue (LCF) test. A multi-objective genetic algorithm is used to calibrate the raw parameters by the inverse analysis. The performance of the models is evaluated on the diameter of the shell considering the work-hardening. The novelty of this study lies in the acquisition of calibrated hardening rule parameters for the crimping process, which involves a multi-axial deformation pattern, using only data from uniaxial tensile and LCF tests, which are simpler to conduct. The force-moment requirements, springback, and material flow path are also calculated. The results provide a valuable insight into the combined hardening model, its parameters, and their sensitivity for the crimping process. The calibration process results in significant improvements in material properties, particularly yield strength (YS) and tangent modulus (TM). For the crimping, YS is observed to increase by 37.82% and TM is observed to decrease by 13.84% while parameters { C 1 , gamma 1 , C 2 , gamma 2 , C 3 , gamma 3 } increase approximately 9% where Cm is hardening modulus, and gamma m is decrease rate. The model achives an absolute percent relative error (APE) of 0.18%.Öğe Calibrating the combined hardening rule parameters for burr-free forging simulation of the torque rod joint(Sage Publications Ltd, 2025) Kacar, Ilyas; Yildirim, SefaJoints used in the automotive industry are widely manufactured by forging. A cold upsetting process can provide burr-free forging which reduces economic loss by preventing material waste. In this study, finite element simulations for the upsetting of a torque rod joint made of 41Cr4 steel are performed. The novelty of the present study lies in the fact that the upsetting performance is investigated through simulation having hardening model in order to replace the existing forging process. The performance of hardening models is studied for an accurate simulation and optimum parameters are determined. A combination of the bilinear isotropic hardening rule and Chaboche's nonlinear kinematic hardening rule is employed with the associated flow rule and Hill48 yield criterion to set up a plasticity model of the upsetting process for the first time. The parameters of the bilinear isotropic hardening rule are determined from monotonic tensile tests. The Chaboche's parameters are determined by using hysteresis loops obtained from strain-controlled low-cycle fatigue tests. The parameters of both rules are combined. Furthermore, they are calibrated using inverse analysis based on the optimization method. Genetic algorithm is used for optimization. The experimental diameter and height measurements of the joint are compared with those obtained from the optimized model. The results show that the application of the combined hardening rule provides better prediction performance of the upset dimensions with minimum dimensional tolerance. The calibrated parameters are presented for the upsetting process. The calibrated parameters of the combined hardening model for the upsetting are YS = 446.64 MPa, TM = 3363.05 MPa, C-1 = 452.31 MPa, gamma(1) = 55.165, C-2 = 212.13 MPa, gamma(2) = 12.24, C-3 = 194.191 MPa, gamma(3) = 10.00 where YS, TM, C-1,C- gamma 1,C- C-2,C- gamma 2,C- C-3,C- gamma 3 are hardening models' parameters. Absolute percent true error (APE) is 0.19%. The parameters are YS = 1.93 MPa, TM = 6.98 MPa, C-1 = 580.79 MPa, gamma(1) = 1.08, C-2 = 597.23 MPa, gamma(2) = 0.98, C-3 = 565.05 MPa, gamma(3) = 2.87 in the case of cyclic load. APE is 1.66%. Also upsetting force requirement and material flow path are presented. The forging process can be replaced by the burr-free upsetting process with necessary changes in the die and press bench design. This replacement will save the 128-gr material per each one of the torque rod joint part.Öğe Multipart Die Design for Bladeless Fan Housing Using the Tube Deforming Simulation(Springer Heidelberg, 2025) Karacan, Kivanc; Kacar, Ilyas; Yildirim, SefaTube deforming is a sheet metal manufacturing process that requires significant plastic deformations. It offers a potential to produce fast and burr-free tube deformation for bladeless fan housing. In this study, a multipart die and punch have been designed to facilitate this process. Finite element method-based simulations are performed to analyze the tube deformation of AA7075-T6. To enhance the accuracy of the simulation, two hardening models are combined. The combined rule involves a bilinear isotropic hardening model, characterized by its linear nature, and Chaboche's kinematic hardening model, which exibits a nonlinear nature. The raw parameters are determined using regression on the uniaxial tensile test data and low cycle fatigue data. The raw parameters are calibrated using inverse analysis and multi-objective genetic algorithm to specialize them in the tube deformation process where the deformation path is cyclic. The plasticity model is constituted of Hill48 yield criterion, the combined hardening rule, and associated flow rule. The novelty of this study is that the model parameters for the tube deformation process, which has a more complex deformation pattern, are acquired using only the data obtained from tensile and low cycle fatigue tests which are simpler to conduct. Additionally, linear and nonlinear models are combined for more accuracy and the calibrated parameters are established. The force-moment requirement and material flow path are also presented.Öğe Parameter Calibration of a Novel Combined Hardening Model for a Wire Drawing Simulation of AA7075-T6(Springer, 2025) Kacar, Ilyas; Yildirim, SefaA novel combined hardening model integrating bilinear isotropic and nonlinear kinematic hardening rules is proposed to simulate the cold wire drawing process of AA7075-T6. The plasticity model is formulated using Hill48 yield criterion, the proposed hardening rule, and the associative flow rule. Firstly, the experiments of monotonic tensile and low cycle fatigue tests are carried out and true stress-true plastic strain data are obtained. The parameters of the hardening rules and anisotropy coefficients for yield criterion are determined using the obtained test data. An inverse analysis is performed to calibrate the parameters using optimization and the finite element-based wire drawing simulation. The hardening curves of a combined model, bilinear isotropic hardening rule, and Chaboche's nonlinear kinematic hardening rule are compared as their performance metric. Validation is achieved through experimental results, and the optimum and calibrated parameters for wire drawing of AA7075-T6 are proposed. The results offer an insight into the hardening model, its parameters, and their sensitivity for the wire drawing simulation. It is concluded that the prediction of the combined model is more accurate than those of bilinear isotropic and Chaboche's nonlinear kinematic hardening rules. The drawing force requirement and material flow path are also determined.
