Browsing by Author "Habibi, Niloufar"
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
- Effects of Damage Evolution on Edge Crack Sensitivity in Dual-Phase Steels
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2024-10) Habibi, Niloufar; Beier, Thorsten; Lian, Junhe; Tekkaya, Berk; Koenemann, Markus; Muenstermann, SebastianThe present study aims to thoroughly investigate the edge-cracking phenomenon in high-strength sheets. Hence, the edge crack sensitivity of three dual-phase steels is studied in various combinations of edge manufacturing and forming processes. Finite element simulations are performed to elaborate the study. In this regard, the Yoshida–Uemori kinematic hardening model is employed to describe the plasticity behavior of the materials under multistep processes. A stress-state fracture model is coupled with this plasticity model to illustrate the distinguished local fracture strains of each material. Moreover, the effects of strain rate and the consequent temperature rise on hardening and damage are taken into account, which play significant roles during shear-cutting. The results show that although the shear-cutting processes are applied at very low speed, the strain rate and induced temperature are still high at the cutting area. The hole expansion results show different fracture behaviors for different cases. In brief, cracking is initiated at a location, which shows the highest damage accumulation during edge manufacturing plus the subsequent forming process. Such a complicated situation can only be successfully predicted by using a computer-aided approach along with proper material modeling, like the applied model in this study. - A rate-dependent damage mechanics model for predicting plasticity and ductile fracture behavior of sheet metals at high strain rates
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2024-08-05) Zeng, Chongyang; Fang, Xiangfan; Habibi, Niloufar; Münstermann, Sebastian; Lian, JunheUniaxial tensile tests were performed on H340 steel sheets at different strain rates (10-4 to 103 s-1) and temperatures (–30 °C and 280 °C). Oscillation-free forces were measured during high-speed tests at strain rates of up to 1000 s-1 using specimens with different stress states. Material hardening curve, strain rate sensitivity, temperature effects, and Taylor-Quinney coefficient for adiabatic temperature calculations were determined in experiments. Digital image correlation (DIC) technique was employed to measure displacement, deformation, and local strain fields. Meanwhile, the temperature fields of specimen gauge section were measured with a high–speed thermal camera in the uniaxial tensile tests at various strain rates. Damage and fracture-related parameters were calibrated and validated using porosity measurements on SEM micrographs and in combination with finite element (FE) simulations. A rate– and temperature–dependent plasticity and damage mechanics model (e2MBW) was proposed and calibrated to predict the plasticity and fracture behavior of H340 under different loading speeds. The study demonstrated good agreement in the overall experimental and simulated force–displacement responses and local strain evolution across all fracture specimens at loading speeds from 0.005 mm/s to 10000 mm/s.