13th International Conference on the Technology of Plasticity (ICTP 2021): Characterization of Plasticity and Ductile Fracture of Metals under Proportional and Non-proportional Loading III
Program Organizers: Glenn Daehn, Ohio State University; Libby Culley, The Ohio State University; Anupam Vivek, Ohio State University; Jian Cao, Northwestern University; Brad Kinsey, University of New Hampshire; Erman Tekkaya, TU Dortmund; Yoshinori Yoshida, Gifu University
Wednesday 10:20 AM
July 28, 2021
Room: Virtual: Room C
Location: Virtual
Session Chair: Jeong Whan Yoon, KAIST
In-plane Stretch-bending Test for Determination of Large-strain Workhardening and Fracture of Sheet Metals: Ryutaro Hino1; Gustavo Capilla2; Hiroshi Hamasaki1; Koudai Watanabe3; Fusahito Yoshida4; 1Hiroshima University; 2University of Guanajuato; 3Graduate School of Hiroshima University; 4CEM Inst Co.
In-plane stretch-bending tests have been conducted to determine workhardening behavior at large strain and edge fracture limit of several high-strength steel (HSS) sheets. In this test a metal strip is bent in its width direction under longitudinal tensile force, and the outer edge of the bent strip undergoes a large uniaxial stretching which is much larger than the uniform elongation in conventional tensile test. Then a stress-strain curve at large strain can be determined through an inverse approach based on the experimental result and the corresponding FE analysis. In addition, localized necking and fracture limit strain at the outer edge of the bent strips are investigated by using the digital image correlation technique to discuss edge fracture limit (stretch flangeability) of the HSS sheets. Significance of a large-strain workhardening model and an anisotropic yield function is demonstrated by FE simulation of strain-localization in in-plane stretch bending.
Microstructure Informed Deformation and Fracture Model for High-strength Steels: Junhe Lian1; Wenqi Liu2; Zinan Li1; Fuhui Shen2; Sebastian Muenstermann2; 1Aalto University; 2RWTH Aachen University
In the integrated computational materials engineering (ICME) roadmap, quantitative correlation of the material microstructure and its mechanical deformation properties by using a multiscale modeling approach is of high interest for material production and component forming industry. In this study, we present a multiscale characterization and modeling approach to incorporate the influences of the microstructural features on the mechanical properties including plasticity, damage, and ductile fracture behavior. Both micro and macro scale experiments and simulation are conducted to describe and interpret the deformation and failure behavior. The anisotropic flow behavior under various strain rates is correlated with the microstructure features and their evolution during deformation, while the macroscopic damage/fracture behavior is also interpreted by the microstructural-level mechanisms in the mesoscale simulation. After validation of the model, we show the potential of the approach for the microstructure design toward a high-strength and damage-tolerant steel development.
Grain Size Effect on the Ductile Fracture of Steel in Hot Deformation: Zhenshan Cui1; Xiaoqing Shang1; Haiming Zhang1; Yangqi Li1; 1Shanghai Jiao Tong University
Grain size undoubtedly has strong influence to the microscopic deformation inhomogeneity of steel, leading to a different fracture behavior. However, the grain size effect on the ductile fracture was not deeply investigated in the literature. Taking the 316LN stainless steel as an investigated material, this presentation will introduce our research work in the fracture behavior and criterion by considering the inhomogeneity of microscopic deformation caused by the difference of grain size and orientations. The investigation showed that the void evolution in matrix with large and small grain size has different influence to the fracture behavior of the steel. The voids growth model was established by considering the grain size effect. In hot deformation process, the dynamic recrystallization yields fine grains and releases the stress concentration resulted from dislocation pile-up. A fracture criterion was proposed to predict the ductile fracture of the steel undergoing hot deformation.
Cancelled
New Methods for Fracture Detection of Automotive Alloys in the VDA238-100 V-Bend Bend Test: Jacqueline Noder1; Cliff Butcher1; 1University of Waterloo
The VDA 238-100 tight-radius bend test has received significant attention from industry because it provides a proportional plane-strain-plane-stress state until fracture. A custom inverted V-Bend test frame has been developed to facilitate DIC strain measurement on the convex surface where fracture initiates. It will be demonstrated that the adoption of the vertical punch force as the unique metric for failure detection is fundamentally flawed. The force will reduce at large bend angles due to the mechanics of the test even in the absence of material failure. Three alternative methodologies for fracture detection are proposed based upon: the bending moment, nominal principal stress, and the strain rate for a range of representative automotive steels Finally, the VDA requirement to pre-strain high ductility materials that can form a complete fold without fracture is critically evaluated and shown to incorporate a non-linear strain path that affects the material response of each alloy differently.
An Application of Homogeneous Anisotropic Hardening Model to the Prestrained Hole-expansion Experiment: Jinjin Ha1; Yannis P. Korkolis1; 1The Ohio State University
In this work, the plastic anisotropy of AA6022-T4 in hole-expansion is investigated focusing on prestraining effect, and its numerical solution is predicted by Homogeneous Anisotropic Hardening (HAH) model combined with an anisotropic yield function. For the prestraining, the material is subjected to 8 % of uniaxial tension in the RD in advance. Then, hole-expansion is conducted in a fully-instrumented hydraulic press with a flat-headed punch. In both experiments, digital image correlation (DIC) is used, to confirm the prevalence of uniaxial loading in the prestraining step and to measure thickness strain in the hole-expansion. The results show that the plastic anisotropy is manifested as a non-axisymmetric strain distribution around the hole. The prestraining, leading to non-proportional loading, changes the location of failure from ~45o to RD. The simulation shows the current version of HAH model is limited in capturing the thickness contours and the failure location.