Comparison of residual stress in relaxed and non-relaxed weldments of steel plates

In this study, two methods, X-ray diffraction (nondestructive) and hole-drilling (destructive) are applied to measure the residual stress of gas metal arc welded steel plate. Both non-relaxed and relaxed (local heating, furnace annealing and bead blasting) weldments are examined to understand the residual stress distributions before and after elimination of residual stresses. Results show that the heat affected zone of gas metal arc welding method is about 10 mm from the weld centerline. The local heating method is very effective in reducing the residual stress caused by the cold work of the original steel plate. The furnace annealing method reduces the residual stress to compressive but not uniformly distributed. The detrimental fluctuation of residual stress is successfully reduced and uniformly relaxed to be beneficially compressive in the bead blasting. Most importantly, X-ray diffraction shows more precise and better handling than hole-drilling method in terms of data error.     

Ultimate strength of dented steel plates under edge shear loads

The aims of this paper are to investigate the ultimate shear strength reduction characteristics of steel plates due to local impacts, and also to develop the ultimate shear strength design formulae of dented steel plates. The ANSYS nonlinear finite element code is used to investigate the effects of shape, size (depth, diameter), and location of the denting on the ultimate strength behavior of simply supported steel plates under edge shear loads. A closed-form expression for predicting the ultimate shear strength of dented steel plates is derived by the regression analysis based on the computed results. The results and insights developed from the present study will be very useful for damage tolerant design of steel plated structures with local denting.     

Influence of friction stir welding residual stresses on the compressive strength of aluminium alloy plates

The mechanical behaviour of welded structures can be significantly affected by the effects of the employed joining process. The main goal of this work is to assess the influence of the longitudinal residual stresses on the overall compressive performance of aluminium friction stir welded plates. Longitudinal residual stress distribution was measured by means of the contour method and introduced as initial condition into a finite element model of the compressed assembly. Also, the sensitivity of the plates to the magnitude of the initial geometrical imperfections was analysed. It can be inferred that both factors influence the plate's mechanical behaviour.     

Effects of welding residual stress on compressive behavior and ultimate strength of corroded plate

This study examined the effects of welding residual stress on the compressive behavior and the ultimate strength of the corroded plate. First, welding residual stress was obtained by the thermal elastic-plastic analysis. Then, the change of welding residual stress and the deflection due to the volume loss was investigated by using a newly developed program based on FEM. Finally, the effects of welding residual stress on the compressive behavior and the ultimate strength of the corroded plate were investigated by the elastic-plastic large deformation analysis. As results, the beginning point of the reduction of the initial stiffness with welding residual stress was earlier than that without welding residual stress. Such effect was observed significantly in the case that the volume was lost in the region which has compressive residual stress. Furthermore, the ultimate strength of the corroded plate was reduced by welding residual stress regardless of the plate length, the corroded regions and the reduction of the thickness. The effect of welding residual stress on the ultimate strength became small with the decrease of the thickness.     

论钢结构焊接残余应力控制与消残方法

结合施工实践，分析了钢结构焊接残余应力的成因及危害，鉴于此提出了焊接残余应力的控制目标和措施，并总结了消除构件残余应力的方法，从而提高钢结构的整体承载力、增强结构的安全性。     

Identification of factor determining strength under compressive loads of steel members corrected by heating/pressing

By using cruciform columns, factors dominating behavior under compressive loads of steel structural members, whose locally buckled part was corrected by heating/pressing, have been elucidated. They were geometric residual imperfection resulted from incomplete correction and increase of yield stress due to large plastic deformation caused by local buckling and its correction process. For soundness diagnosis of the corrected member, the importance of these factors was investigated based on the results of the numerical simulation. Although the increase of yield stress did not affect the ultimate strength, that changed the deformation mode of the member after the ultimate situation. As the result, it was elucidated that the increase of yield stress was not important in the soundness diagnosis. The residual imperfection affected the buckling and ultimate strength of the corrected member. Rather the size of the region than the absolute value in the out-of-plane direction of the residual imperfection should be controlled as small as possible for ensuring the soundness of the corrected member.     

T型钢节点焊接残余应力及变形研究

运用有限元方法分析研究了T型节点焊接的残余应力与变形,重点阐述了该T型焊接变形的类型、残余应力分布规律及控制焊接变形的措施,供类似工程参考。     

拉压性能不同钢箱梁的纯弯曲弹塑性分析

将材料本构关系简化成拉压屈服极限不同的理想弹塑性模型,对纯弯曲作用下的钢箱梁弹塑性全过程进行了分析,得到了依赖于拉压比γ的弹性、塑性极限弯矩以及弯矩与曲率之间的关系,所得到的公式经过一定的几何参数变化,同样适用于形、槽形、矩形等钢梁的弹塑性分析,当γ=1时所得结果退化为拉压性能相同的弹性极限弯矩与塑性极限弯矩。     

A semi-analytical method for the elastic-plastic large deflection analysis of welded steel or aluminum plating under combined in-plane and lateral pressure loads

The aim of the present paper is to develop a semi-analytical method which can quickly and accurately compute the elastic–plastic large deflection response of welded steel or aluminum plating under a combination of biaxial compression/tension, biaxial in-plane bending, edge shear and lateral pressure loads, until the ultimate limit state is reached. The post-weld initial imperfections (i.e. initial deflection and residual stresses) are included in the method as parameters of influence. It is assumed that the plating is simply supported at all (four) edges which are kept straight. A unique feature of the developed method is that geometric nonlinearity associated with large deflection response of plating under combined loads is treated by analytically solving the nonlinear governing differential equations of the elastic large deflection plate theory, while material nonlinearity due to plasticity is dealt with implicitly by a numerical procedure. This approach reduces the magnitude of numerical computations, resulting in a saving of modeling effort and computing time. As another contribution, this paper investigates and discusses the ultimate strength characteristics of plating, by varying the plate properties and load combinations, based on elastic–plastic large deflection analysis using the developed method.     

H型钢焊接残余应力的三维有限元分析

采用通用有限元软件ABAQUS对普通H型钢的焊接残余应力场、变形场进行了数值模拟,并和现有公认结果进行了对比。结果表明,数值模拟方法真实可靠,纵向残余应力影响较大,应引起足够的重视。     

钢结构焊接变形的预防和处理方法探讨

介绍了钢结构构件由于焊接产生的变形问题，结合长期施工经验，从立柱底板、H型钢焊制等方面提出一些钢结构焊接变形的预防和矫正措施，以提高钢结构构件的加工质量。     

焊接钢梁残余应力有限元分析

采用通用有限元软件ANSYS模拟分析焊接工字梁的焊接过程,对焊接残余应力场进行数值模拟并进行有限元分析,从而得到焊接钢梁残余应力的大小及分布规律,以便设计人员在进行相关焊缝设计时对残余应力的大小进行估算,为工程实践应用提供一定的指导。     

Ultimate strength of perforated steel plates under combined biaxial compression and edge shear loads

The present paper is a sequel to the author's papers [Paik JK, Ultimate strength of perforated steel plates under edge shear loading. Thin-Walled Structures 2007; 45: 301–6, Paik JK Ultimate strength of perforated steel plates under axial compressive loading along short edges. Ships Offshore Struct, 2007; 2(3): (in press)]. In contrast to the previous papers with the focus on edge shear or uniaxial compressive loads, the aim of the present study is to investigate the ultimate strength characteristics of perforated steel plates under combined biaxial compression and edge shear loads, which is a typical action pattern of steel plates arising from cargo weight and water pressure together with hull girder motions in ships and ship-shaped offshore structures. The plates are considered to be simply supported along all (four) edges, keeping them straight. The cutout is circular and located at the center of the plate. A series of ANSYS nonlinear finite element analyses (FEA) are undertaken with varying the plate dimension (thickness). Based on the FEA results obtained, closed-form empirical formulae of the ultimate strength interaction relationships of perforated plates between combined loads, which can be useful for first-cut estimations of the ultimate strength in reliability analyses or code calibrations, are derived.     

扁平钢箱梁U肋焊接残余应力数值模拟分析

已建成的扁平钢箱梁桥在运营过程中发现一些与结构、构造和制造相关的病害,并且随着服役时间的增长越来越突出。其原因是扁平钢箱梁结构采用薄板组焊而成,因此,扁平钢箱梁在未受力之前,便已存在着由于焊接所产生的应力场和变形场,导致扁平钢箱梁普遍出现裂纹等病害。运用热结构耦合法对扁平钢箱梁U肋与桥面板交接处焊接的温度场和应力场进行数值模拟计算分析,并得到焊接残余应力的分布规律,为进一步分析结构病害与加固设计提供依据。     

Buckling analysis of stiffened plates subjected to non-uniform biaxial compressive loads using conventional and super finite elements

This paper presents the buckling analysis of stiffened plates, using both conventional and super finite element methods. Mindlin plate and Timoshenko beam theories are utilized so as to formulate the plate and stiffeners, respectively. The arbitrary oriented stiffeners can be positioned anywhere within the plate element and are not limited to be placed on nodal lines. Therefore, any configuration of plate and stiffeners can be modeled. Furthermore, extensive boundary conditions as well as general in-plane loading conditions can be considered using the proposed method. As the applied in-plane loads are not uniform, the buckling load is evaluated in two steps. First, the elasticity problem is solved to determine the stress distribution in prebuckling stage. Applying the principle of minimum potential energy, based on derived stress distribution, yields to the buckling equation of stiffened plates. Numerical examples are proposed to study the accuracy and efficiency of the developed super elements. Effects of various combinations of biaxial loads along with different boundary conditions on buckling characteristics of stiffened panels are also investigated.     

焊接残余应力对网架负荷加固的影响分析

负荷条件下对网架结构进行加固时,焊接残余应力对网架结构的内力、变形有较大影响。本文结合某网架负荷加固工程,通过运用ANSYS有限元软件对焊接杆件施加等效温度荷载的方式,模拟网架负荷加固杆件焊接时的热胀冷缩。通过相应的应力、变形分析,得出焊接残余应力对网架结构负荷加固的影响。     

非均匀竖向压应力作用下钢板剪力墙的剪切屈曲

采用有限元软件ABAQUS 6.10对非均匀压应力、剪应力共同作用时非加劲和竖向加劲钢板剪力墙进行屈曲分析,研究了非均匀竖向压应力对非加劲钢板剪力墙临界屈曲剪应力的影响,得到了竖向加劲钢板剪力墙临界屈曲剪应力随加劲肋加劲系数的变化曲线及阈值刚度。结果表明,非加劲钢板剪力墙临界屈曲剪应力随着钢板剪力墙宽高比、高厚比和非均匀压应力剪应力比的增大而减小,随着竖向压应力非均匀系数的增大而增加|加劲肋阈值刚度随着竖向压应力非均匀系数、小区格宽高比、加劲肋数目和加劲肋抗扭抗弯刚度比的增大而减小。     

考虑变围压因素的饱和软黏土循环纯压动力特性

饱和土体的动力特性表现出对应力路径的依赖性。越来越多基于变围压动三轴的试验结果表明：循环围压应力路径对砂土等颗粒材料的变形和回弹特性存在较大的影响。基于变围压动三轴试验,通过循环偏应力与循环围压的耦合模拟真实交通荷载下竖向循环正应力与水平循环正应力的耦合,研究了循环围压对饱和软黏土孔压、永久和回弹变形的影响。试验结果表明：在不排水条件下,与常规恒定围压动三轴试验结果相比,循环围压的存在较大程度地改变了孔压的发展规律,减少了永久变形的累积速度,同时增加了回弹变形（即减少了回弹模量）;循环围压幅值与循环偏应力幅值的比值（RPD）越大,永久应变的减少值与回弹应变的增加值越大;并进一步建立了考虑循环围压因素的饱和软黏土永久沉降和回弹模量预测模型。     

焊接残余应力的产生及其消除方法

在分析残余应力产生原理的基础上,介绍了焊接残余应力的概念,并探讨了焊接残余应力产生的原因及其影响因素,提出了消除焊接残余应力的方法,指出研究和测量构件中残余应力对生产和科学试验具有重要意义。     

钢板混凝土组合墙体局部稳定性轴压试验研究

进行了4个应用于核电工程的钢板混凝土组合墙轴压试验,试验设计中主要考虑距厚比参数的不同。分析了构件的破坏机理、荷载-位移曲线、钢板的荷载-屈曲曲线。分析结果表明：钢板的屈曲对试件整体刚度影响不明显,栓钉能有效地保证钢板和混凝土协同工作;随着距厚比变小,试件极限承载力有所提高,钢板的屈曲应变变大。在试验分析基础上,给出了组合墙体的初始刚度和极限承载力的经验公式,导出了适合钢板弹性屈曲应变的理论公式。