基于固有应变的海洋平台典型结构 焊接变形预测研究

针对半潜式起重拆解平台,运用热弹塑性有限元分析和弹性有限元法,对平台中连接平台和浮体的典型结构,进行焊接变形的预测。通过对焊接接头的预测分析,得到其固有变形,再将计算得到的固有变形,以载荷的形式加载到整个结构中,得到整个结构的焊接变形。通过对三种焊接顺序的比较,得到焊接变形最小的方案。在此基础上,考虑开口对结构焊接变形的影响。研究结果将对半潜式起重拆解平台特殊结构的焊接工艺优化提供理论支撑和数据支持。     

大型核电厚壁结构X射线衍射法残余应力测试

采用X射线衍射法（ XRD）对大型核电厚壁结构堆芯板端面、堆芯板与吊篮筒体环焊缝焊前焊后残余应力进行无损测量。研究堆芯板端面、环焊缝焊前焊后残余应力的分布情况及变化规律。结果表明：堆芯板焊前残余应力主要是机加工应力,且焊接过程对其残余应力影响不大;1＃和2＃堆芯板环焊缝轴向残余应力分布趋势明显,呈现焊缝为压应力,母材为拉应力;测试的环向应力在各区域分布不一致;焊接对远离焊缝区域的应力没有影响,远离焊缝区域呈现较大的加工应力。     

焊接转子残余应力热处理过程中应力释放行为数值研究

基于ABAQUS有限元分析软件,编写DFLUX、FILM和UEXPAN子程序,建立焊接转子模拟件(M-1)和全尺寸焊接转子(M-2)轴对称有限元模型,实现了采用双椭球移动热源模型和考虑固态相变的转子焊接仿真过程。纳入Norton-Bailey蠕变本构方程研究了热处理过程中残余应力在不同热处理参数下的应力松弛行为。结果表明：焊接转子模拟件能够较为准确地反映全尺寸焊接转子焊接残余应力分布状态;考虑固态相变的焊接仿真结果更接近于实验测量值;热处理参数对残余应力释放行为影响不尽相同,其中热处理温度是决定热处理效果的关键因素。     

基于固有应变理论的船体焊接变形仿真研究

大型船舶构件尺寸大、焊缝分布广,传统的有限元焊接仿真方法难以满足其大尺寸结构计算的要求。基于热弹塑性有限元法对T型局部接头进行焊接变形计算,获取焊缝处平均固有应变值,然后将其作为初始载荷施加在全尺寸壳单元分段模型上进行弹性计算,最终得到大型分段的整体焊接变形。仿真结果表明,结合小模型的热弹塑性法和大结构固有应变法,能准确高效的预测大型结构的焊接变形。     

基于盲孔法的水下承压结构残余应力测试研究

对盲孔法测残余应力中的等轴三角应变花应变释放系数进行有限元标定和塑性修正,得到了塑性修正后的应变释放系数;采用盲孔法对高强度钢水下承压结构典型部位的焊接残余应力进行测量,根据测试得到各测点的释放应变值,结合修正后的应变释放系数计算得到了水下承压结构典型测点的残余应力值。结果表明,水下承压结构焊缝附近纵向残余应力可达0.5倍屈服极限,周向残余应力可达0.4倍屈服极限。     

盲孔法测量921A钢焊接残余应力的应变释放系数研究

根据盲孔法测量残余应力的基本原理和孔边塑性变形修正方法,分别对盲孔法测量921A钢焊接残余应力时的应变释放系数A、B进行实验标定,通过试验得出了921A钢盲孔孔边塑性变形对测量精度的影响和盲孔法测量921A钢焊接残余应力的塑性修正公式;并对实验标定应变释放系数与通孔应变释放系数理论解进行比较,表明试验结果与通孔应变释放系数理论值有较好的一致性,测量结果经塑性修正,最大误差减小到2．5％以下,试验结果可以直接在盲孔法测量921A钢焊接残余应力工程实际中应用。     

An efficient FE computation for predicting welding induced buckling in production of ship panel structure

In a Thermal-Elastic-Plastic (TEP) FE analysis to investigate welding induced buckling of large thin plate welded structure such as ship panel, it will be extremely difficult to converge computation and obtain the results when the material and geometrical non-linear behaviors are both considered. In this study, an efficient FE computation which is an elastic FE analysis based on inherent deformation method, is proposed to predict welding induced buckling with employing large deformation theory, and an application in ship panel production is carried out. The proposed FE computation is implemented with two steps:(1) The typical weld joint (fillet weld) existing in considered ship panel structure is conducted with sequential welding using actual welding condition, and welding angular distortion after completely cooling down is measured. A TEP FE analysis with solid elements model is carried out to predict the welding angular distortion, which is validated by comparing with experimental results. Then, inherent deformations in this examined fillet welded joint are evaluated as a loading for the subsequent elastic FE analysis. Also, the simultaneous welding to assemble this fillet welded joint is numerically considered and its inherent deformations are evaluated.(2) To predict the welding induced buckling in the production of ship panel structure, a shell element model of considered ship panel is then employed for elastic FE analysis, in which inherent deformation evaluated beforehand is applied and large deformation is considered. The computed results obviously show welding induced buckling in the considered ship panel structure after welding. With its instability and difficulty for straightening, welding induced buckling prefers to be avoided whenever it is possible.     

焊接速度对AH36船用高强钢焊接残余应力及其释放的影响

焊接件由于焊接速度不同,焊接残余应力分布存在很大差异,焊接残余应力在循环载荷作用下会产生释放现象,焊接残余应力存在对于结构安全性和稳定性有很大影响,有必要开展焊接速度对于焊接残余应力及其释放影响研究。基于ABAQUS软件二次开发建立平板对接焊试件焊接残余应力以及释放有限元模型,利用顺序耦合热力学数值仿真计算三种焊接速度下的焊接残余应力分布,并开展三种焊接速度下初始焊接残余应力在三种拉伸循环载荷作用下的释放情况研究。     

船用高强度钢焊接残余应力测量技术研究

本文研究采用纯弯曲梁法对高强度钢X射线弹性常数(XECs)进行了试验测定;研究分析了试件表面电解腐蚀前后以及不同的电解腐蚀深度对残余应力测量结果的影响,分析得到对钢结构表面预处理的操作方法。最后进行了高强度钢平板焊接试板残余应力测量验证试验,并与数据仿真结果进行了比较,试验结果表明：试板焊接残余应力分布与数值仿真结果基本一致;其中有2/3的比对测点的残余应力测量偏差小于±25MPa。     

Prediction of steel plate deformation due to triangle heating using the inherent strain method

In a shipyard, line heating and triangle heating are two major processes carried out by skilled workers to form curved plates in various shapes under various heating conditions. There have been many studies on line heating, but triangle heating has rarely been studied owing to its complicated heating process with irregular multiheating paths and highly concentrated heat input. Triangle heating is the most labor-intensive job. Hence, it is essential for most shipyards to study the automation, as well as the improvement, of the triangle heating process in order to increase hull-forming productivity. In this study, a pioneering attempt to simulate triangle heating was made. A circular disk-spring model is proposed as an analysis model for the elastoplastic procedure of triangle heating, and the inherent strain method is also used to analyze the deformation of plates. The results of the simulation were compared with those of experiments and showed good agreement. It is shown that the present approach and the model used in this study are effective and efficient for simulating triangle heating for the steel plate forming process in shipbuilding.     

20000TEU集装箱船水密横舱壁结构精度建造的预控

水密横舱壁作为20000TEU集装箱船的关键结构,对尺寸精度的要求十分严苛,尤其是焊接变形严重影响其建造精度。针对这一问题,采用基于固有变形理论的弹性有限元分析,来预测水密横舱壁结构的面外焊接变形。同时,比较了计算固有变形的两种方法的准确度,并且总结了热输入与固有变形各分量的经验公式,还提出了减小面外焊接变形的措施。结果表明,通过与实测数据对比验证了弹性有限元分析可快速、准确地预测水密横舱壁结构的面外焊接变形;对于对接接头,变形反演法比应变积分法得到的横向固有弯曲更准确;热输入与固有变形各分量呈线性递增关系;将整个水密横舱壁结构由原来的3段分成5段,并采用对称焊接顺序,面外焊接变形最小,同时会降低对船厂吊装能力的要求。     

钻孔法检测残余应力技术中有关参数的数值计算分析

通过建立有限元数值模型,分别模拟了钻孔前后两种不同状态下应力应变分布情况。经比较计算出钻孔后的梁底混凝土表面轴线上各节点的轴向应变,并结合相关理论,计算出钻孔前梁底中心节点应力的理论值,从而找出与梁底中心节点实际施加应力的吻合点。根据节点理论值与实际施加应力的吻合情况,结合应变测量机理,最终确定最佳孔径、孔深和最佳粘贴应变片位置等参数。     

残余应力的筛降效应及其对矩形板强度的影响

分析了船体板中残余应力的筛降,得到了在受拉和受压情况下的筛降水平的计算公式,并用有限元程序模拟了残余应力的筛降过程,验证了公式的有效性.分析了残余应力的筛降对板的平均应力-平均应变曲线的影响,采用两种方法分别得到了考虑筛降效应的板的平均应力-平均应变曲线的表达式,用有限元法进行了模拟计算,结果表明,分别计算受残余拉应力和残余压应力区的应力得到的平均应力-平均应变曲线和有限元计算结果符合得更好.     

Elastic local buckling strength of stiffened plate considering plate/stiffener interaction and welding residual stress

An analytical formula for estimating elastic local buckling strength of a continuous stiffened plate subjected to biaxial thrust is derived considering the influence of plate/stiffener interaction and welding residual stresses. Through a comparison of calculated results with those by FEM eigenvalue analysis, high accuracy of the proposed formula is demonstrated. A series of buckling strength analyses is performed on the deck and bottom plating of actual ships. It has been found that:

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焊接结构变形分析系统(Weld_Sta)的开发及其应用

为使现场工程人员方便进行焊接结构变形分析,开发了一个能简单地对焊接变形有限元分析所需的数据进行前处理,对焊接变形进行计算机分析并对仿真结果进行后期处理的软件-焊接结构变形分析系统。该软件操作简便,具有自动寻找焊缝,通过固有变形数据库自动导入焊接参数,自动施加约束条件,计算模块兼容性强等多项实用功能,从而满足现场工程人员要求。并以某大型船体分段焊接变形预测为例,验证了本软件系统的实用性和可靠性。     

钻孔法检测残余预应力的有限元计算

用有限元法计算平板构件和预应力混凝土梁在钻孔前后的应力应变分布。结果表明,钻孔法检测预应力混凝土梁的残余预应力时,应变片的位置选择很重要;建议合理的贴片位置,并给出检测残余预应力时的修正系数。这一研究成果是钻孔法检测预应力混凝土梁残余预应力的基础,可以为该方法的工程应用提供参考。     

船用5083铝合金随焊滚压工艺的有限元计算

船用5083铝合金在焊接过程中较易出现热裂纹,主要原因是在脆性温度区间存在较大的收缩内应力。为此,对随焊滚压工艺进行研究,采用有限元分析软件MSC.Marc进行焊接工艺模拟,综合考虑焊接热源模型、材料性能和滚压等边界条件,建立船用5083铝合金工件的随焊滚压有限元模型,对比船用5083铝合金薄板在普通焊接工艺及随焊滚压工艺下的焊后残余应力。计算结果表明,在随焊滚压工艺下选择合适的轮枪距及压下量可有效降低焊后残余应力。