Constitutive Equation for Stainless Steel Used in Structural Engineering
Stainless steel is characterized by nonlinear stress-strain behavior, material anisotropy and different mechanical properties in tension and compression. As a result, it is necessary to define stress-strain relations of stainless steel precisely for the researches of mechanical behavior and stability of stainless steel member. This paper reviews the researches in constitutive relations models home and abroad, after introducing, analyzing, comparing the exist models, presents the three-stage stress-strain model proposed by Quach, which is defined using the three basic Ramberg-Osgood parameters and could be used in structural design by the current codes, considering the Quach equation as the most accurate constitutive equation for stainless steel material.
Residual stresses in press-braked stainless steel sections, II: Press-braking operations
Abstract The manufacturing process of cold-formed thin-walled steel members induces cold work which can be characterized by the co-existent residual stresses and equivalent plastic strains and has a significant effect on their structural behaviour and strength. The present paper and the companion paper are concerned with the prediction of residual stresses and co-existent equivalent plastic strains in stainless steel sections formed by the press-braking method. This manufacturing process consists of the following two distinct stages: (i) coiling and uncoiling of the sheets, and (ii) press-braking operations. This paper first presents an analytical solution for the residual stresses and the co-existent equivalent plastic strains that arise from the second stage while a corresponding analytical solution for the first stage is presented in the companion paper. In both solutions, plane strain pure bending is assumed and the effect of material anisotropy is taken into account. On the basis of these two analytical solutions, an analytical model is presented to predict residual stresses and equivalent plastic strains in press-braked stainless sections. The predictions of the analytical model are shown to be in close agreement with results from a finite element-based method, demonstrating the validity and accuracy of the analytical model. The analytical model provides a much simpler method for the accurate prediction of residual stresses and equivalent plastic strains in different parts of a press-braked stainless steel section than a finite element-based method.
Residual Stresses in Cold‐Formed Steel Members
An extensive experimental investigation of the residual stresses in cold‐formed steel members is presented. The electrical discharge machining (EDM) technique is used to cut coupons for residual stress measurement. As compared to the conventional saw‐cutting method, the EDM technique greatly reduces the external disturbance during the machining of a thin‐walled section caused by heating, clamping, and vibration. The experimental results provide a further understanding of the magnitude and distribution of the residual stresses in cold‐formed steel sections, which are found to be quite different from the residual stresses in hot‐rolled steel shapes. Based on the experimental findings, an idealized distribution pattern of the residual stresses in a cold‐formed channel section is outlined. Finally, the yielding propagation in an axially compressed cold‐formed steel section is described, and an equation for predicting the extent of yielding is derived.