Articles
International Journal of Damage Mechanics (10567895)(1)
Damage measurement of materials is a crucial challenge for researchers and engineers in manufacturing industries. In this study, based on the image processing technique, a developed approach for determining the Lemaitre’s ductile damage parameter by the direct measurement method is proposed. For this purpose, first, the micrographs pictures are provided by a scanning electron microscope to attain the damage evolution behavior of St37 steel. Then, prediction results of the suggested method and the Lemaitre’s direct approach as well as the microhardness technique and also a lately published numerical method in damage propagation, crack initiation, and ductile fracture of a few tensile samples are compared with the corresponding experimental tests. The comparison reveals the higher efficiency and accuracy of the current approach. Therefore, it is concluded that the new presented method is a reliable approach to achieve the Lemaitre’s ductile damage parameter and predict the damage evolution behavior of ductile materials. © The Author(s) 2024.
Archive of Applied Mechanics (09391533)(1)
Damage growth phenomenon in sheet metal forming processes is one of the most important issues in the manufacturing industries. Predicting the onset and location of crack can help engineers to postpone the failure as well as to produce safe parts. In this research, first, six different calibration methods are employed for the Bao-Wierzbicki damage criterion. Then, to evaluate the accuracy of the calibration approaches, a few conventional sheet metal forming processes with the positive stress triaxiality are numerically simulated. Finally, the numerical predicted results are compared with the empirical tests. The comparisons reveal that the hyperbolic quadratic hyperbolic 3 (HQH3) method is the best calibration approach, due to its accuracy and the fewer number of required experimental tests for the calibration. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.
Journal of Constructional Steel Research (0143974X)
To improve the accuracy of the original Lemaitre's ductile damage model under various loading conditions, this study proposes an enhanced version of the model for sheet metal forming processes under plane stress assumptions by incorporating a functional material-dependent damage parameter. For this aim, the theoretical framework, constitutive equations, and a robust numerical explicit algorithm for the new model are first derived. Subsequently, a comprehensive calibration process is widely performed using a varying number of calibration points to optimize the functional ductile damage parameter. In the following, a user-defined subroutine is developed to numerically simulate the damage behavior of several SS304 stainless steel specimens subjected to different loading conditions, including the Erichsen's forming test. The accuracy of the novel criterion is thoroughly investigated and fully validated by the corresponding empirical observations. Finally, the numerically predicted fracture locus and forming limit diagram of the material are compared with the relevant practical data. The comparison strongly highlights the improved predictive capability and reliability of the enhanced model. © 2025
Engineering Failure Analysis (13506307)
Accurate prediction of ductile damage is a critical challenge for the safe design of sheet metal structures. The Lemaitre's ductile damage model has been widely used for prediction of ductile damage, however its accuracy fully depends on loading conditions and calibration range. This paper eliminates this limitation by proposing a 2D Lode improved model (LIM) of the original Lemaitre (OL) for sheet metals. The modification incorporates the Lode parameter, a crucial, often-neglected factor influencing damage evolution. First, the LIM's theoretical framework and constitutive equations for the plane stress conditions in sheet metals including the Lode parameter is completely presented. Then, numerical approaches such as counting search and Taguchi methods are employed and validated for identification of the model parameters. Finally, to evaluate the LIM's performance, a user-defined VUMAT subroutine is developed for numerically simulation of numerous specimens under diverse loading conditions as well as to assess the model's effectiveness and reliability. The numerical simulation results are compared with experimental data and the comparison demonstrates a significant improvement in accuracy of the LIM rather than the OL ductile damage model. © 2024 Elsevier Ltd
International Journal of Precision Engineering and Manufacturing (22347593)(1)
In the machining processes, chip removal can be performed by the applied forces. Therefore, predicting the required forces and energy is an essential challenge to reach the efficient processes. In this research, employing various ductile damage models of the continuum damage mechanics (CDM), a few machining processes such as 3D plane machining, 3D drilling, and turning are numerically simulated. Using the numerical simulations of finite element method (FEM), variations of the applied forces on the workpiece and the maximum force as well as the mechanism of chip formation during the machining processes are estimated. Besides, to assess the ductile damage models, the numerical simulation results are compared with the experimental results. The comparison reveals that the Ayada, Ayada negative, and Johnson–Cook damage criteria can accurately predict the required forces and respectively are the reliable models for numerical simulations of chip removal in the machining processes. © 2023, The Author(s), under exclusive licence to Korean Society for Precision Engineering.
