Computer Methods in Materials Science
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ISSN 2720-4081
e-ISSN: 2720-3948
Issue Date
2022
Volume
Vol. 22
Number
No 1
Description
Journal Volume
Computer Methods in Materials Science
Vol. 22 (2022)
Projects
Pages
Articles
Finite element analysis of bipolar plate stamping based on a Yld2000 yield model
(Wydawnictwa AGH, 2022) Wang, Wenyao; Xiao, Yao; Guo, Nan; Min, Junying
Finite element analysis is an essential means for bipolar plate design and the optimization of the manufacturing process. However, the accuracy of the finite element simulation is significantly affected by the constitutive model, especially the yield model. In this paper, uniaxial and biaxial tensile tests were conducted to obtain the yield loci of an ultra-thin austenite stainless steel. The Yld2000 yield model was calibrated using the yield loci under different equivalent plastic strains. The microchannel stamping experiment and its finite element simulations were conducted to study the effect of yield model parameters on the finite element simulation of bipolar plate stamping. The results show that the simulation with Yld2000 calibrated by 0.004 and 0.05 equivalent plastic strain has the best prediction accuracy for the microchannel springback and thickness distribution, respectively.
Modeling of temperature-dependent cyclic performance of superelastic NiTi shape memory alloy
(Wydawnictwa AGH, 2022) Xiao, Yao; Ju, Shuangyan; Lin, Jianping
In this paper, a three-dimensional micromechanical-based constitutive model is proposed to describe the temperature-dependent performance of a cyclic deformed superelastic NiTi shape memory alloy. The dominant texture of the specimen is prescribed as <111> direction along the longitudinal direction. Apart from martensitic transformation, various mechanisms regarding superelastic degradation are taken into consideration. In order to be extended from the single-crystal scale to the polycrystalline version, the constitutive model is implemented into finite element software. It is verified that the measured cyclic response of a superelastic NiTi is well reproduced by the presented approach. Furthermore, the predicting capability of the proposed model is verified by simulating the mechanical behavior of NiTi tube subjected to cyclic bending.
A finite-strain model for a superelastic NiTi shape memory alloy
(Wydawnictwa AGH, 2022) Jiang, Dongjie; Xiao, Yao
A finite-strain constitutive model of a superelastic NiTi shape memory alloy is proposed in this paper. Via backward Euler implicit integration scheme and the incorporation of material softening, the model is implemented into finite element code to reproduce a Lüders like deformation of a superelastic NiTi. The simulation results are in agreement with the experimental results, indicating that the constitutive model can reasonably predict the mechanical behavior of a superelastic NiTi. A parametric study further verifies that the magnitude of softening modulus has a significant effect on the stress-strain response and Lüders-like deformation of a superelastic NiTi.
Thermomechanical modeling on the crack initiation of NiTi shape memory alloy
(Wydawnictwa AGH, 2022) Jiang, Dongjie; Xiao, Yao
The fracture of shape memory alloys is distinct from that of conventional metals, owing to the coexistence and interaction of multiple special features such as martensitic transformation, dislocation-induced plasticity, thermomechanical coupling and others. In this paper, the impact of thermomechanical behavior upon the crack initiation of a NiTi shape memory alloy under Mode I loading is investigated numerically and verified experimentally. A constitutive model incorporating phase transformation, plasticity and thermomechanical coupling is established. Via backward Euler integration and finite-element implementation, the longitudinal strain, martensite volume fraction and temperature field in the vicinity of the crack tip are furnished. The effects of grain size and loading rate on J-integral are revealed. The grain size dependence of crack initiation is non-monotonic. For the samples with grain sizes of 1500 nm, 18 nm and 10 nm, the shielding effect takes place in front of the crack. Additionally, the anti-shielding effect is detected for samples with grain sizes of 80 nm and 42 nm. The parametric study shows that loading rate imposes limited influence on J-integral, which is attributed to a small scale transformation. The decrement of yield stress and the increment of transformation hardening modulus can alleviate the anti-shielding effect and arouse the shielding effect upon crack initiation. The presented results shed light on the design and fabrication of high toughness phase transformable materials.
Identification of the heat source and thermal material model parameters for the laser engineered net shaping
(Wydawnictwa AGH, 2022) Hajder, Lucyna; Zhang, Tao; Nguyen, Vu
The research's primary goal is to identify the heat source and thermal material model parameters for the numerical simulation of the laser engineered net shaping (LENS). Inconel 718 was selected as a case study for the current investigation. The LENS process's numerical model was developed within commercial finite element software and was used as a direct problem model during the parameter identification stage. Experimental data were obtained based on a rectangular-shaped sample with thermocouples located under the based material surface. The recorded thermal profiles were used to establish a goal function for the parameter identification stage. As a result, parameters describing the melt pool geometry during the additive manufacturing, as well as thermal coefficients describing interactions between the sample material and surrounding/base material, were determined.