Gab-Chul Jang

Analysis of residual stress in stainless steel pipe weld subject to mechanical axial tension loading

This paper presents the characteristics of welding residual stresses in circumferentially butt-welded stainless steel pipe by utilizing three-dimensional (3-D) uncoupled thermo-mechanical finite element (FE) analysis method. Moreover, stress variations in welded joints of the pipe under superimposed mechanical axial tension loading are further investigated employing the welding residual stresses and plastic strains obtained from the thermo-mechanical FE analysis as an initial condition. Results show that spatial variations of the welding residual stresses are present along the circumference and a rapid change of the residual stresses exists at the welding start/stop position, hence 3-D FE analysis is essential to accurately simulate circumferential welding of a pipe component. When mechanical axial tension loading is applied to the circumferentially butt-welded stainless steel pipe, bending moment is generated at the welded joints caused by the circumferential shrinkage of the weld region during welding; thus affecting the axial and hoop stress evolutions in the course of the superimposed mechanical loading.

A STUDY ON HYSTERETIC MODEL FOR WELD METAL AND ITS EFFECT ON BEHAVIOR OF STEEL PIPES WITH A WELDED JOINT

The weld metals used in welding process influences on behavior of steel structures under monotonic and cyclic loading. Because weld metals have different characteristics than structional steels for stress-strain relationship and mechanical properties. Therefore, to predict behavior of steel structure manufactured by welding process, a hysteretic model for weld metal is necessary. In this paper, to formulate the hysteretic model for E71T-1 weld metal, tensile tests and low cycle fatigue tests were carried out. A formulated hysteretic model applied to 3-dimensional elastic-plastic finite element analysis was proposed by the authors. To investigate the effect of weld metal on behavior of steel pipe members, numerical analyses of steel pipe with a welded joint were carried out under monotonic and cyclic loading. The effect of weld metal was clarified by comparing analytical results both steel pipe with consideration of weld metal and without consideration of weld metal.

An Analytical Study on Moment Response of Welded Steel Pipe for Loading Rate

This article aims to analytically research for influence of residual stresses on bending moment responses against welded steel pipes subjected to quasi -static or dynamic loadings. The residual stresses of the welded steel pipe are computed by three-dimensional welding simulation. The bending moment responses of the welded and seamless steel pipes are determined by using three-dimensional dynamic elastoplastic FE analysis as a function of loading rate. It is seen from analytical results that the welded steel pipe shows lower moment response comparing to the seamless steel pipe, and moment difference between seamless and welded steel pipes tends to decrease as loading rate increases.

EFFECT OF THE DEGREE OF RESTRAINT AGAINST THERMAL EXPANSION AND CONTRACTION ON WELDING RESIDUAL STRESS

Steel bridges increased considerably since 1960s in Japan. That is due to the lightness and long trend in bridge construction. Bridges, which are damaged by an increase in vehicle load, corrosion, earthquake, and so on, need repairing or strengthening. Repair procedures of steel bridge generally include cutting, bolting and welding procedures. These procedures, cutting, bolting and welding, occasionally bring about a stress concentration within the limit range. So, a chain of confirmation against the safety of structure is necessary. A safety evaluation method, which has regard to heat effect, is necessary to repair damaged structure with welding. Generalized welding residual stress is useful employ, to estimate the safety of structure during the repair work with welding. This research investigates the features of thermal stress generated by welding. The pattern of welding residual stress distribution was classified according to the ratio between length and width of plate. With those results, the features of residual stress generated by welding were generalized.

A Study on Seismic Performance of High-Strength Steel(POSTEN60, POSTEN80) Pipe-Section Piers using 3-Dimensional Elastic-Plastic Finite Deformation Analysis

Recently, as steel structures become higher and more long-spanned, application of high-strength steels is increasing gradually. For seismic design of steel structures using high-strength steels(POSTEN60, POSTEN80), analytical method, can describe the large deformation and inelastic cyclic behavior generated by non-proportional cyclic loading, are required. In this paper, cyclic plasticity model was proposed by results of monotonic loading tests ant cyclic loading tests. Three-dimensional finite element analysis is developed by using proposed model and finite deformation theory and verified as compare with experiment result. Using 3-dimensional elastic-plastic finite deformation analysis, seismic analysis of high-strength steel pipe-section piers are carried out. Also, seismic performance of high-strength steel pipe-section piers in parameter of diameter-thickness ratio was clarified. 缀Ѐ㘰〻ሀ䝥湥牡氠瑥捨湯汯杹