Multiaxial constitutive behavior of an interstitial-free steel: Measurements through X-ray and digital image correlation

Abstract

Constitutive behaviors of an interstitial-free steel sample were measured using an augmented Marciniak experiment. In these tests, multiaxial strain field data of the flat specimens were measured by the digital image correlation technique. In addition, the flow stress was measured using an X-ray diffractometer. The flat specimens in three different geometries were tested in order to achieve 1) balanced biaxial strain, and plane strain tests with zero strain in either 2) rolling direction or 3) transverse direction. The multiaxial stress and strain data were processed to obtain plastic work contours with reference to a uniaxial tension test along the rolling direction. The experimental results show that the mechanical behavior of the subjected specimen deviates significantly from isotropic behavior predicted by the von Mises yield criterion. The initial yield loci measured by a Marciniak tester is in good agreement with what is predicted by Hill's yield criterion. However, as deformation increases beyond the vonMises strain of 0.05, the shape of the work contour significantly deviates from that of Hill's yield locus. A prediction made by a viscoplastic self-consistent model is in better agreement with the experimental observation than the Hill yield locus with the isotropic work-hardening rule. However, none of the studied models matched the initial or evolving anisotropic behaviors of the interstitial-free steel measured by the augmented Marciniak experiment.

Uncertainty in flow stress measurements using X-ray diffraction for sheet metals subjected to large plastic deformations

“…In this section, an application specific to the reflection X-ray equipment used by Jeong et al (2015Jeong et al ( , 2016 is discussed. The experimental time required for in situ X-ray diffraction for flow stress measurement can be estimated by the number of diffraction vectors (N ' and N ) and the diffraction exposure research papers Uncertainty in diffraction stress based on the {211} planes estimated by the Monte Carlo experiment.…”

“…of 5 is used. Note that the multiaxial experiments conducted previously (Foecke et al, 2007;Pham et al, 2015;Jeong et al, 2015Jeong et al, , 2016) also use some angular range to measure the diffraction peaks. The experimental value varies depending on the grain size, beam spot size and depth of penetration.…”

“…The measured stress was in good agreement with an independent mechanical measurement by hydraulic bulge test. Recently, this method has been extended for plane-strain paths and compared with multiaxial predictions by various constitutive models (Jeong et al, 2016). However, the uncertainty in the measurement technique has not been clearly addressed owing to the absence of an appropriate method.…”

Crystal Plasticity Modeling for Non-ferrous Metals and its Engineering Applications

“…To the author's understanding, the predictive accuracy for bcc metals is worse than that of fcc metals and needs to be notably improved. Jeong et al 81) used a viscoplastic self-consistent crystal plasticity model to predict the anisotropic hardening of plastic contours in an interstitial-free steel sheet. However, the simulation results were not in good agreement with the experimental results.…”

Prediction and Validation of Stress Triaxiality Assisted by Elasto-Visco-Plastic Polycrystal Model

“…응력 상태가 가지는 중요 성은 성형 한계 곡선(Forming Limit Curve, 이하 FLC)의 응력 경로 무관성에서도 잘 드러난다 [8]. 최근 디지털 이 미지 상관법(digital image correlation, 이하 DIC)을 활용 한 변형률 측정 기법이 널리 보급되었으나, 응력 측정의 경우 유사한 형태의 불균일한 분포를 실험적으로 측정하기 것이 쉽지 않다 [9]. 따라서, 실험적으로 측정된 변형률을 구성 모델과 연계하여 삼축성 및 로드각을 변수로 사용한 예측 모델의 성공적 사례가 다수 보고되어 왔다 [10].…”