预测角焊缝角变形的剪切固有应变法

基于一系列有限元数值实验,提出了角焊缝剪切固有应变分量的抛物面分布模型,并总结出模型表达式中各待定参数以及整体修正系数的经验公式.在此基础上,进一步提出了一种用于预测角焊缝角变形的线弹性简化方法,即剪切固有应变法.对T形接头和加筋板的角焊焊接实验证实了该方法对角焊缝角变形的预测结果具有一定的工程价值.     

EH36船用钢焊接角变形有限元分析

采用有限元分析方法,根据实际焊接工艺过程,对船舶常用低温高强钢EH36中厚板的二道焊缝焊接温度场及焊接角变形进行了分析.中厚板焊接常为二道的埋弧焊接,在有限元分析中采用生死单元技术进行处理.有限元分析结果显示焊接温度场关于热源中心对称,同一厚度截面方向的节点处的焊接变形相同,而在横向由于焊缝在厚度方向收缩的不均匀性,处于焊缝间隙大的截面的节点焊接变形要大于处于小间隙截面的节点.实验结果证明了有限元分析的准确性.     

T型焊接结构的角变形控制

T型焊接在船舶结构中的应用是非常广泛的.T型接头附近局部的加热及冷却使被焊结构产生残余应力及角变形.目前在船厂精度控制中,通常采用构件焊接后对某些部位进行火工校正的方法来控制残余角变形.论文提供了另外一种有效控制结构残余角变形的方法:对结构焊前施加弹性的反向角变形.文中首先利用热弹塑性有限元来模拟未施加反变形的结构的焊接过程,以估算残余角变形;然后模拟施加了弹性反变形的结构的焊接过程,并计算此时结构的残余角变形,以最终确定构件所需要的弹性反向角变形值.施加了弹性反向角变形的构件在焊接后无需进行火工校正.     

固有变形计算方法及其在船舶焊接结构变形中的应用

采用基于固有应变法的弹性有限元分析预测大型复杂结构的焊接变形的前提是必须已知焊缝附近的固有变形。结构的焊接残余应力与焊接变形取决于其接头的固有变形大小及分布,因此开发精确计算接头固有变形的方法,并依此建立一个完善的固有变形数据库对于大型复杂结构焊接变形的预测有重要意义。文中提出了几种计算固有变形的方法包括公式法、热弹塑性有限元法、实测法,并分别采用这几种方法对典型T型接头的横向固有收缩与纵向固有收缩进行计算,三种方法得到的结果比较一致。在此基础上,进一步以典型船体结构为研究对象,采用依照这三种方法建立的固有变形数据库对其焊接变形进行预测,并与实测数据进行比较,验证了该数据库的有效性。     

固有变形计算方法及其在船舶焊接结构变形中的应用（英文）

采用基于固有应变法的弹性有限元分析预测大型复杂结构的焊接变形的前提是必须已知焊缝附近的固有变形。结构的焊接残余应力与焊接变形取决于其接头的固有变形大小及分布,因此开发精确计算接头固有变形的方法,并依此建立一个完善的固有变形数据库对于大型复杂结构焊接变形的预测有重要意义。文中提出了几种计算固有变形的方法包括公式法、热弹塑性有限元法、实测法,并分别采用这几种方法对典型T型接头的横向固有收缩与纵向固有收缩进行计算,三种方法得到的结果比较一致。在此基础上,进一步以典型船体结构为研究对象,采用依照这三种方法建立的固有变形数据库对其焊接变形进行预测,并与实测数据进行比较,验证了该数据库的有效性。     

关于角焊缝的效率和效益

本文提出以控制角焊缝的焊脚尺寸的途径和使用下行焊等提高角焊缝效率的焊接方法，来节约焊接材料，减少焊接变形，达到缩短造船周期，降低造船成本的目的。     

T型接头全焊透角焊缝自动焊接工艺研究及应用

在船舶设计制造过程中,底边舱、内底板、槽型舱壁等连接位置,涉及许多T型和斜T型焊接接头.特别是木屑船制造过程中,槽型舱壁制作采用T型接头全焊透角焊缝型式.由于传统CO2手工焊接效率低下、焊接质量不稳定、工人劳动强度大,为了使T型接头全焊透角焊缝焊接效率及质量有明显提升,同时降低工人劳动强度,文章进行T型接头全焊透角焊缝...     

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。     

典型焊接接头固有应变的影响因素研究

基于热弹塑性有限元法采用多线性各向同性强化原则对船级钢T型接头的焊接过程进行了数值模拟,重点研究分析热输入量、焊接速度及焊脚长对固有变形的影响.从T型接头的固有应变数值分析与实验结果对比可以得到:当热输入量一致,数值计算的温度场和角变形与试验结果基本一致;角变形随着焊接速度和焊脚长增大,先增大后减小;横向收缩与纵向收缩率则有着不同的比例关系。     

船用大型焊接结构的焊接变形预测实例

对船体结构中常见的焊接接头在焊接过程中的力学行为进行了热弹塑性有限元分析,确定其固有应变与热输入的关系。在掌握固有应变规律的基础上,应用固有应变焊接变形分析软件,对低温储罐结构的焊接变形进行了预测。表明采用基于固有应变的弹性板单元有限元法,能够对大型船体结构进行焊接变形预测。     

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.     

确定焊接反变形的数值模拟及规律分析

焊接接头附近局部的加热及冷却使被焊结构产生残余应力及角变形.目前在船厂精度控制中,通常采用构件焊接后对某些部位进行火工校正的方法来控制残余角变形.文章提供了另外一种有效控制结构残余角变形的方法:对结构焊前施加弹性的反向变形.利用热弹塑性有限元法来模拟结构的焊接过程,并对不同板厚、不同热源的结构分别进行数值模拟,最终确定焊接结构的弹性反变形规律:焊接前施加弹性反变形的结构在焊接后角变形趋于零.     

定位焊顺序对单面埋弧焊接头残余应力和变形的影响（英文）

Submerged arc welding(SAW) is advantageous for joining high thickness materials in large structure due to high material deposition rate. The non-uniform heating and cooling generates the thermal stresses and subsequently the residual stresses and distortion. The longitudinal and transverse residual stresses and angular distortion are generally measured in large panel structure of submerged arc welded fillet joints. Hence, the objective of this present work is to quantify the amount of residual stress and distortion in and around the weld joint due to positioning of stiffeners tack. The tacking sequence influences the level of residual stress and proper controlling of tacking sequences is required to minimize the stress. In present study, an elasto-plastic material behavior is considered to develop the thermo mechanical model which predicts the residual stress and angular distortion with varying tacking sequences. The simulated result reveals that the tacking sequence heavily influences the residual stress and deformation pattern of the single sided fillet joint. The finite element based numerical model is calibrated by comparing the experimental data from published literature. Henceforth, the angular distortions are measured from an in-house developed experimental set-up. A fair agreement between the predicted and experimental results indicates the robustness of the developed numerical model. However, the most significant conclusion from present study states that tack weld position should be placed opposite to the fillet weld side to minimize the residual stress.     

Influence of tacking sequence on residual stress and distortion of single sided fillet submerged arc welded joint

Submerged arc welding (SAW) is advantageous for joining high thickness materials in large structure due to high material deposition rate. The non-uniform heating and cooling generates the thermal stresses and subsequently the residual stresses and distortion. The longitudinal and transverse residual stresses and angular distortion are generally measured in large panel structure of submerged arc welded fillet joints. Hence, the objective of this present work is to quantify the amount of residual stress and distortion in and around the weld joint due to positioning of stiffeners tack. The tacking sequence influences the level of residual stress and proper controlling of tacking sequences is required to minimize the stress. In present study, an elasto-plastic material behavior is considered to develop the thermo mechanical model which predicts the residual stress and angular distortion with varying tacking sequences. The simulated result reveals that the tacking sequence heavily influences the residual stress and deformation pattern of the single sided fillet joint. The finite element based numerical model is calibrated by comparing the experimental data from published literature. Henceforth, the angular distortions are measured from an in-house developed experimental set-up. A fair agreement between the predicted and experimental results indicates the robustness of the developed numerical model. However, the most significant conclusion from present study states that tack weld position should be placed opposite to the fillet weld side to minimize the residual stress.     

船底结构的焊接系数研究

采用钢结构焊接强度计算方法,给出船底结构角焊缝应力的计算模型和船舶结构角焊缝焊接系数的计算公式。以一艘31 000 dwt散货船船底结构为例,计算不同工况荷载作用下船底、内底纵骨、船底纵桁以及肋板的焊缝剪应力,并与舱段有限元的剪应力计算结果作比较,验证了当前规范角焊缝焊接系数。     

Numerical prediction and mitigation of out-of-plane welding distortion in ship panel structure by elastic FE analysis

As an application to predict and mitigate the out-of-plane welding distortion by elastic FE analysis based on the inherent deformation theory, a panel structure of a pure car carrier ship is considered. The inherent deformations of different types of welded joints included in this ship panel structure are evaluated beforehand using thermal elastic plastic FE analysis. Applying idealized boundary condition to focus on the local deformation, elastic FE analysis shows that the considered ship panel structure will buckle near the edge and only bending distortion is dominant in the internal region. In order to mitigate out-of-plane welding distortion such as buckling and bending, straightening using line heating is employed. In the internal region, only inherent bending with the same magnitude as welding induced inherent bending is applied on the opposite side of welded joints (fast moving torch). On the other hand, only in-plane inherent strain produced by line heating is introduced to the edge region to correct buckling distortion (slow moving torch). The magnitude of out-of-plane welding distortion in this ship panel structure can be minimized to an accepted level.