• Transactions of Materials Processing
• /
• v.26 no.6
• /
• pp.333-340
• /
• 2017

The cyclic hardening behavior of transformation-induced plasticity (TRIP) steels shows tension-compression asymmetry known to be attributed to transformation of retained austenite into martensite during deformation. In this work, YoshidaUemori hardening model was used to represent the asymmetric hardening behavior of TRIP1180 steel. Yoshida-Uemori hardening model parameters were obtained from three sets of data: tension-compression, compression-tension, and a combination of the two. Material models were validated for U-bending and springback.

• Transactions of Materials Processing
• /
• v.22 no.6
• /
• pp.303-309
• /
• 2013

Spring-back of MS1470 steel sheets was numerically predicted using a non-linear kinematic hardening material behavior based on the Yoshida-Uemori model. From uniaxial tension and uniaxial tension-compression-tension data as well as the uniaxial tension-unloading-tension data, the parameters of the Yoshida-Uemori model were obtained. For the numerical simulations, the Yoshida-Uemori model was implemented into the commercial finite element program, ABAQUS/Explicit and ABAQUS/Standard using the user-defined material subroutines. The model performance was validated against the measured spring-back from the benchmark problems of NUMISHEET 2008 and NUMISHEET 2011, the 2-D draw bending test and the S-rail forming test, respectively.

• Transactions of Materials Processing
• /
• v.25 no.3
• /
• pp.189-194
• /
• 2016

In the current study, spring-back of DP980 steel sheet was numerically evaluated for U-bending using a yield function with a hardening model. For spring-back prediction, two types of yield functions - Hill'48 and Yld2000-2d - were considered. Additionally, isotropic hardening and the Yoshida-Uemori model were used to investigate the spring-back behavior. The parameters for each model were obtained from uniaxial tension, uniaxial tension-compression, uniaxial tension-unloading and hydraulic bulging tests. The numerical simulations were performed using the commercial software, PAM-STAMP 2G. The results were compared with experimental data from a U-bending process.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.1
• /
• pp.101-110
• /
• 2014

Expansion agent is a very effective admixture for prevention of cracking due to autogenous/drying shrinkage and this can induce internal chemical prestress to embedded reinforcement. In this paper, tension-softening and hardening in cement mortar with steel and CSA expansion agent are experimentally evaluated. Cement mortar with steel reinforcement is prepared and tensile strength test is performed for evaluation of cracking and tensile behavior. In spite of slightly reduced strength and elasticity in CSA mortar, significantly increased tension-hardening behavior is evaluated in CSA mortar with induced chemical prestress. Furthermore previous tension softening models are compared with the test results and improvement are proposed.

• Transactions of Materials Processing
• /
• v.21 no.6
• /
• pp.372-377
• /
• 2012

In this study, the plastic flow behaviors of extra deep drawing quality (EDDQ) steel subjected to non-proportional strain paths were investigated. Two-step uniaxial tension tests, in which the first step was performed in the rolling direction (RD) and the subsequent test in different directions in $15^{\circ}$ increments from the RD, were conducted. The experiments clearly showed that stress overshooting and strain hardening stagnation were the dominant features, which were captured reasonably well using a recently proposed distortional hardening model.

• Transactions of Materials Processing
• /
• v.6 no.2
• /
• pp.118-135
• /
• 1997

In order to analyze the deformation and residual curvature of steel sheets in the strip processing lines, a program for calculating curvature and work hardening of sheet was developed. Strip deformation caused by repeated bending under tension in the process lines was analyzed on the basis of the incremental-plasticity theory with the mixed hardenting model for the purpose of predicting the strip shape and the yield stress change. The developed calculation program was applied to predict curl and gutter of sheets within a 10% difference. The yield stress increment was also predicted with the similar accuracy. Application of the model to tension legvelling process showed that gutter could be controlled by intermesh and elongation. The yield stress increment in the electro-galvanizing line calculated by the developed program was found to be dependent on the yield strength, the applied tension and the diameter of the smallest roll.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.2 s.173
• /
• pp.378-385
• /
• 2000

Fracture resistance (J-R) curves, which are used for elastic-plastic fracture mechanics analyses, decreased under tension-compression loading condition. This phenomenon was proved by several former researches, but the causes have not been clear yet. The objective of this paper is to investigate the cause of this phenomenon. On the basis of fracture resistance curve test results, strain hardening hypothesis, stress redistribution hypothesis and crack opening hypothesis were built. In this study, hardness tests, Automated Ball Indentation(ABI) tests, theoretical stress field analyses, and crack opening analyses were performed to prove the hypotheses. From this study, strain-hardening of material, generation of tensile residual stress at crack tip, and crack opening effects are proved as the causes of the decrease hypothesis.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.1
• /
• pp.41-48
• /
• 1991

A set of constitutive equations is formulated to predict elastic-plastic strain hardening response of sintered porous iron under combined tension and torsion. The proposed constitutive equations were capable of predicting characteristic behaviors of porous metals. Agreement between theoretical curves and experimental data for elastic-plastic response of sintered porous iron was very good for various initial porosities.

• Transactions of Materials Processing
• /
• v.10 no.2
• /
• pp.160-166
• /
• 2001

Uniaxial necking is studied for steel sheets with initial anisotropy. The state of anisotropy is continuously altered by subsequent tensile deformation at angles to the rolling direction. The orientations of orthotropy axes are changed before the onset of necking. A simple hardening rule which incorporates the rotations of orthtropy axes is proposed and the necking strains are predicted at angles to the rolling direction. Predicted results show good agreement with the experiments.

• Journal of the Korea Concrete Institute
• /
• v.25 no.4
• /
• pp.371-379
• /
• 2013

This paper investigates the cracking and tension-stiffening behavior of 100 MPa shrinkage-compensated strain-hardening cement composite (SHCC) and conventional concrete tie elements in monotonic and cyclic tension. Strain and surface crack formation of tension ties were monitored with two strain displacement transducers and a photo microscope with a lens of magnification 50 times. Three different cement composites such as conventional concrete, shrinkage-compensated SHCC, and normal SHCC were used in the tie specimens to investigate the influence of the cement composite type on the tension stiffening and cracking behavior. Test results indicated that initial shrinkage of the ultra high-strength cement composites is greatly reduced as the 10% replacement of cement by the shrinkage-compensating admixture based on calcium sulfo-aluminate (CSA). The test results on the SHCC tension ties showed that the first cracking load decreases proportionally to the initial shrinkage strain. Reinforced ultra high-strength SHCC ties with the initial shrinkage compensation exhibited improved tension stiffening and smaller crack spacings, i.e. the reduction in crack width. Cyclic loading did not have a significant effect on tension stiffening and cracking behavior of tension ties with normal concrete and SHCC materials.