Ehssen Betaieb PhD

Identification of material parameters using single point incremental forming

Cosupervisor: Laurent Duchêne

Abstract

This thesis aims to use the single point incremental forming (SPIF) process to identify the mechanical material parameters to feed behaviour models. Typically, the characterization of a sheet metal passes through several testing machines to determine the material behaviour occurring in a forming process. Traditional identification methods require specific equipment that are not always available in industries. This study is conducted by performing different in-plane tests (tensile, shear and reverse shear), as well as different geometries made by the SPIF process (conical shape, pyramidal shape, line, Z-shape, two-wing star and four-wing star). The finite element (FE) simulations of the different tests are computed by the Lagamine FE code developed by the MSM team since the eighties. Levenberg-Marquardt algorithm is used to calibrate the material parameters by inverse modelling based on the FE simulations. In this work, the material studied is the CuZn37 brass.

This PhD study aims to simplify the identification of the kinematic hardening, it provides an alternative to the use of specific equipment for the reverse shear test or experimental device to perform tension-compression tests. The SPIF line test is used to calibrate kinematic hardening and the identified set of parameters is validated by the Z-shape SPIF test and three reverse shear tests with different pre-strains. The numerical results show the accuracy of this new methodology to predict the Bauschinger effect.

Moreover, as the mechanical behaviour in large deformation field is poorly characterized by the tensile test, the use of the SPIF process reaching high strains to identify the hardening parameters is a good lead. Two identification procedures called “Direct Method (DM)” based on tensile and reverse shear tests and “SPIF Inverse (SI)” relying on a cone SPIF test and a tensile test are developed to identify material parameters able to model the hardening behaviour in large strain field. The two approaches are compared and validated by simulations of the different experiments: in-plane tests (shear and reverse shear tests) and SPIF geometries (pyramid, line and Z-shape). The FE simulations performed with the SI dataset are highly accurate in predicting the forming force in the SPIF tests and very efficient in terms of CPU time, but fail in modelling the reverse shear tests. The simulations with the DM dataset satisfy all the validation tests, but they have a high cost as they require mesh refinement and strict contact modelling for the cone and pyramid SPIF tests.

Finally, the conventional forming limit diagram (FLD) underestimates the failure in the SPIF process. Therefore, providing an evaluation of the formability during this process thanks to a procedure to determine the SPIF-FLD is a valuable contribution. The SPIF-FLD is determined by a mixed approach based on three SPIF geometries (70-degree pyramid, two-wing star and four-wing star) and validated by a safe cone test.

Publications

Betaieb, E., Yuan, S., Guzman, C. F., Duchêne, L., & Habraken, A. M. (2019). Prediction of cracks within cones processed by single point incremental forming. Procedia Manufacturing, 29, 96-104. https://doi.org/10.1016/j.promfg.2019.02.111

Yuan, S., Duchêne, L., Keller, C., Hug, E., Folton, C., Betaieb, E., Milis, O., & Habraken, A.M. (2021). Mechanical response of nickel multicrystals for shear and tensile conditions at room temperature and 573 K. Materials Science and Engineering: A: Structural Materials: Properties, Microstructures and Processing, 809, 140987. https://doi.org/10.1016/j.msea.2021.140987

Habraken, A. M., Aksen, T. A., Alves, J. L., Amaral, R. L., Betaieb, E, et al. (2022). Analysis of ESAFORM 2021 cup drawing benchmark of an Al alloy, critical factors for accuracy and efficiency of FE simulations. International Journal of Material Forming, 15 (5), 61. https://doi.org/10.1007/s12289-022-01672-w

Betaieb, E., Duchêne, L., & Habraken, A. M. (2022). Identification and validation of Brass material parameters using single point incremental forming. In TMS Proceedings. Numisheet 2022, 873-883. https://doi.org/10.1007/978-3-031-06212-4_79

Betaieb, E., Duchêne, L., & Habraken, A. M. (2022). Calibration of kinematic hardening parameters on sheet metal with a Computer Numerical Control machine. International Journal of Material Forming 15, (69). https://doi.org/10.1007/s12289-022-01714-3