搅拌摩擦焊和钨极氩弧焊焊接接头的残余应力

利用X射线衍射法测量了铝合金搅拌摩擦焊和钨极氩弧焊(TIG)焊接接头表面的残余应力分布.结果表明:两种接头在焊缝区及其周围的残余应力存在着明显的变化,在平行于焊缝方向,应力呈"W"型的分布,焊缝外残余应力值迅速下降;钨极氩弧焊焊接接头残余应力的最大值位于热影响区;在热影响区,搅拌摩擦焊接接头残余应力平均值比TIG焊接接头的约低15%～25%.     

用小孔释放法测量焊接高残余应力时孔边塑性变形对测量精度的影响及修正方法

研究了用小孔释放法测量焊接残余应力时孔边的塑性变形对测量精度的影响。根据弹塑性理论分析了孔边屈服的条件，并据此得到了孔边屈服后应变释放系数的修正公式，使小孔释放法测量焊接残余应力的精度得到提高，并且扩大了应力值的测量范围。对平板对接埋弧焊焊接接头残余应力的实测表明，修正后的残余应力分布更趋于合理。     

基于相位-频率测量的材料残余应力超声表征方法*

针对材料中残余应力无损检测的问题,提出一种基于相位-频率关系测量超声信号传播时间的方法,并以声弹性理论为基础,采用纵波和横波相结合的测量模式,建立残余应力的超声测量方法。该超声测量方法应用于焊接接头的残余应力测量,不仅能够表征两轴方向上的残余应力,而且还适用于短距离声时的精确测量,测量精度达到9 mm试样距离上0.3 ns的分辨率(加载应力为20 MPa)。制作16Mn钢材料的焊接接头,并采用所提出的超声测量方法对焊接接头的残余应力分布进行测量。同时,采用理论计算、X射线衍射技术等分别对16Mn钢材料的声弹性参数及焊接接头残余应力分布进行验证测量。研究结果表明基于相位-频率精确测量声时的残余应力超声测量方法具有较高的应力分辨率和较好的测量稳定性,可适用于焊接接头两轴方向上的残余应力表征。     

焊后热处理对20G钢焊接接头残余应力的影响

采用X射线应力分析仪和电子背散射衍射仪(EBSD)等分别研究了热处理前后20G钢焊接接头的表面残余应力和微区残余应力。结果表明:热处理前后焊接接头的表面残余应力均以焊缝为中心呈对称分布,且随距焊缝中心距离的增大而下降,热处理后的平均残余应力比热处理前的降低了7.21%;热处理后焊接接头焊缝区、热影响区和母材区的晶粒发生再结晶转变,晶粒得到细化;再结晶导致局域取向错配角的平均值减小,微观残余应力得到释放,且分布更为均匀,但焊缝区的微观残余应力依然较高。     

用小孔释放法测量焊接高残余应力时孔边塑性变形对测量精度的影响及修...

研究了用小孔释放法测量焊接残余应力时孔边的塑性变形对测量精度的影响。根据弹塑性理论分析了孔边屈服的条件，并据此得到了孔边屈服后应变释放系数的修正公式，使小孔释放法测量焊接残余力的精度得到提高，并且扩大了应力值的测量范围。对平板对接埋弧焊焊接接头残余应力的实测表明，修正后的残余应力分布更趋于合理。     

基于电磁超声的焊接残余应力测量研究

基于超声波声弹性理论,针对钢板对接焊接残余应力无损测量问题,提出了采用电磁超声法开展焊接残余应力实测研究。通过拉伸标定试验测得焊接接头不同区域的声弹性系数与各向异性参数,并结合钢板实测声速值获得了不同部位的焊接残余应力;其结果与基于塑性修正的盲孔法实测值进行了验证比较。结果表明,电磁超声法可以有效地测量钢板焊接接头残余应力的分布状态。     

焊接接头残余应力分析

利用光弹性模拟试验技术，对常用的几种焊接接头的残余应力分布规律进行了研究，为进一步分析焊接结构的残余应力分布规律打下了基础。     

焊接顺序对X80钢管道B型套筒熔化极活性气体保护电弧焊接残余应力的影响

基于X80钢大尺寸管道与B型套筒间熔化极活性气体保护电弧焊环焊缝的热源与本构方程,建立焊接接头的有限元模型,模拟了左右两端同时焊接、左右两端交替焊接以及左右两端先后焊接3种焊接顺序下焊接接头的残余应力分布,并通过盲孔法验证模拟结果的准确性,讨论了焊接顺序对焊接残余应力的影响规律。结果表明：焊接接头的最大残余应力均位于外壁面距盖面焊道1.8～3 mm内,不同焊接顺序下管道和套筒左右两端残余应力分布规律相近;左右两端同时焊接顺序下管道和套筒的峰值残余应力最大,均位于外壁起焊点附近;有限元模拟结果与试验结果的相对误差小于9.15%,模拟结果较准确;左右两端先后焊接顺序对最大焊接残余应力的影响程度最小。     

低碳钢焊缝金属强度组配对焊接残余应力分布的影响规律

采用热弹塑性有限元方法,对平板对接接头中焊缝金属强度组配对焊接残余应力分布的影响进行了研究。结果表明,对于高组配接头,纵向残余应力的峰值接近焊缝金属的屈服极限,出现在焊缝中心。对于低组配接头,纵向残余应力的峰值接近母材的屈服极限,并发生在焊缝附近。随着对含有残余应力的接头施加外载,焊缝金属强度组配对纵向应力分布的影响依然存在,但残余应力的影响在减小。对承受外载的焊接接头,逐步卸除外载后,焊缝横截面     

合并焊道法对SUS304不锈钢平板对接接头焊接残余应力计算精度和效率的影响

厚大不锈钢焊接接头广泛应用于核电、火电和化工等行业中,焊接残余应力一直是一个被关注的焦点问题。随着计算焊接力学理论的日臻成熟,采用有限元方法来模拟焊接残余应力已经成为了可能。但是由于计算机硬件条件的限制,目前的计算效率还难以满足实际工程的需求。基于ABAQUS有限元软件平台开发高效的瞬间热源模型来模拟板厚为25 mm的对接接头的热输入,并与移动热源模型的计算结果进行比较。为了进一步提高计算效率,基于奥氏体不锈钢母材和相应填充材料的性能特点,尝试采用不同的焊道合并方式来缩短焊接温度场和应力场的计算时间。同时,还采用应力释放法测量板厚25mm、焊道数为17道的平板对接接头的残余应力分布,并将数值模拟结果与实验结果进行比较。结果表明,采用瞬间热源模型可较精确地模拟焊接残余应力的分布和大小,计算时间与移动热源模型相比可以大幅缩短。此外,采用数值模拟方法研究合并焊道法对板厚为75mm的对接接头残余应力计算结果的影响。数值模拟结果表明,焊道合并方式对纵向残余应力的计算结果影响较小。对横向残余应力而言,焊道合并方式对计算精度有较显著的影响,表层焊道合并方式严重低估了表面横向残余应力,而内部焊道整体合并方式虽然略微低估了表面横向残余应力,但能较好地预测接头上、下表面的横向残余应力分布与大小。采用瞬间热源模型再结合焊道合并方式是一种解决厚大焊接接头残余应力计算的有效手段。     

压弯组合应力下高强钢焊接板表面裂纹疲劳寿命计算

潜艇上浮下潜运动使得其耐压壳承受交变的外压载荷。潜艇耐压壳的疲劳热点为锥一柱过渡结构连接焊缝焊趾处，该处所受的应力特征为压弯组合应力。压弯组合应力下表面裂纹应力强度因子及其疲劳寿命的计算尚无报道。弄清楚压弯组合应力作用下带表面裂纹焊接板试件的疲劳特性对潜艇等结构的疲劳研究是必要的。文中提出用成一定角度的对接焊板试件和轴向加载获得压弯组合应力来模拟潜艇耐压壳锥一柱焊接结合区的应力特征的实验方法。用980高强钢作试件，研究焊趾处预制表面裂缝，并在压弯组合应力为特征的疲劳载荷作用下表面裂纹的疲劳行为。给出高强钢焊趾表面裂纹在压弯组合应力下应力强度因子及其疲劳寿命计算式。该结果可供海洋平台、压力容器及管道的某些受力特征为压弯组合应力的重要结构的疲劳设计时参考。     

Multi sensor data fusion for improving performance and reliability of fully automatic welding system

This paper presents a new generation of system for pressure vessel and shipbuilding. Typical pressure vessel and ship building weld joint preparations are either traditional V, butt, fillet grooves or have narrow or semi narrow gap profiles. The fillet and U groove are prevalently used in heavy industries and shipbuilding to melt and join the parts. Since the wall thickness can be up to 6 in. or greater, welds must be made in many layers, each layer containing several passes. However, the welding time for the conventional processes such as submerged arc welding (SAW) and flux cored arc welding (FCAW) can be many hours. Although SAW and FCAW are normally mechanized processes, pressure vessel and ship structures welding up to now have usually been controlled by a full time operator. The operator has typically been responsible for positioning each individual weld run, for setting weld process parameters, for maintaining flux and wire levels, for removing slag and so on. The aim of the system is to develop a high speed welding system with multi-torch for increasing the production speed on the line and to remove the need for the operator so that the system can run automatically for the complete multi-torch multi-layer weld. To achieve this, a laser vision sensor and a special image processing algorithm have been made. Also, the multi-torch welding system can be applicable for fine grained steel because of the high welding speed and lower heat input compared to a conventional welding process.     

Pressure vessel for tensile testing in high-pressure gases at elevated temperatures

A pressure vessel for tensile testing has been developed to measure tensile stress in high-pressure up to 50.5 MPa at elevated temperatures up to 773 K. The vessel is designed to facilitate the measurement of the actual tensile load on the specimen by an external load cell without the influence of axial stress due to high pressure in the vessel and the effect of friction at sliding seals where the load rod enters the vessel. Application of the vessel to tensile testing of a steel in hydrogen atmosphere is briefly described.     

多层包扎式筒体焊接缺陷区的裂纹分析

针对多层包扎式合成塔筒体环焊缝两侧的筒节层板贴合不良,出现结构不连续,引用壳体理论对缺陷区的变形和应力进行了计算,经分析论证推断出于高度应力集中的焊接缺陷处将萌生出疲劳微裂纹.因而必须采取严格的焊接工艺,以防止产生焊接缺陷.     

HAZ hydrogen cracking of 9Cr-0.5 Mo-1.7W steels

Advanced creep-resistant steels have been developed to meet the demanding requirements of fossil power plants that strive to improve the generation efficiency by enhancing the steam temperature and pressure. These are ferritic steels with nominal chromium content ranging from 2% to 12% with significant addition of tungsten besides Nb, V, and N in small level. One of the candidate materials is 9Cr-0.5Mo-1.7W steel, developed for steam circuit components of tubes, and pipes of power plants for an operating temperature of 600°C. Hydrogen cracking is a major issue in welding of this steel, due to solid-state metallurgical transformations that lead to untempered martensite in the HAZ of weld joint. The hydrogen cracking does not occur below a threshold stress level called critical cracking stress. The critical stress for cracking in this steel was determined by carrying out implant weldability tests using shielded metal arc welding process for various levels of diffusible hydrogen in the weld metal and an empirical model relating levels of diffusible hydrogen and time taken for cooling from 800°C to 500°C to the critical stress has been developed. Results of current study also showed that residual diffusible hydrogen plays a major role in deciding hydrogen cracking than the initial diffusible hydrogen in the weld metal.     

油气分离器罐低温环境下应力分析

目前市场上的大部分油气分离器罐设计温度范围是-20～150℃,有少部分油气分离器罐在寒冷地区使用,其环境温度已经低于设计温度.利用ANSYS有限元分析软件进行模拟实际工况,系统的论证分析常规油气分离器罐不必按照低温压力容器去选型设计.当壳体或受压元件使用在“低温低应力工况”下,若其设计温度加50℃后高于-20℃时,不必遵循低温压力容器规定.这样可以大大降低压力容器的使用环境温度,提高整个空压机产品的使用范围.     

薄壁筒焊缝残余应力研究

介绍了薄壁筒焊缝残余应力的实验研究。研究结果表明 ,薄壁筒环焊缝存在残余压应力 ,且垂直于焊缝纵向呈压应力分布 ,同时通过电测实验 ,对电测法测定压力容器残余应力的可靠性及测试精度进行了探讨和评价。     

Elastic-plastic stress analysis and fatigue lifetime prediction of cross-bores in autofrettaged pressure vessels

Elastic-plastic stress analysis has been performed to evaluate the fatigue life of an autofrettaged pressure vessel containing cross-bores subjected to pulsating internal pressure of 200 MPa. Finite element analyses were used to calculate the residual and operating stress distributions of the pressure vessel due to the autofrettage process and pulsating internal pressure, respectively. Theoretical stress concentration factors of 3.06, 2.58, and 2.64 were obtained at the cross-bore of the pressure vessel due to internal pressure, 50%, and 100% autofrettage loadings, respectively. Local stresses and local strains determined from the elastic-plastic finite element analysis were employed to calculate the failure location and fatigue life of the pressure vessel with radial cross-bores, incorporating the low-cycle fatigue properties of the pressure vessel steel and fatigue damage parameters. Increase in the amount of overstrain by autofrettage process moved the crack initiation location from the inner radius toward a mid-wall, and extended the crack initiation life, Predicted fatigue life of the fully autofrettaged pressure vessel with cross-bores increased about 50%, compared to the unautofrettaged pressure vessel. At the autofrettage level higher than 50%, the failure location and fatigue life of the pressure vessel were not significantly influenced by the autofrettage level.     

薄板奥氏体不锈钢对接焊缝超声波探伤方法研究

通过对超声波应用于薄板奥氏体不锈钢对接焊接接头的研究和试验,开发了薄板奥氏体不锈钢对接焊接接头超声检测和质量分级方法。试块探伤试验和现场实物检测试验表明,对板厚为3～10 mm的在用压力容器奥氏体不锈钢对接焊缝及母材,辅以超声波探伤,可以及时发现奥氏体不锈钢容器在对接焊缝、封头扳边处、支座角焊缝母材等处存在的各种形式的裂纹或缺陷,有效避免出现容器的失效事故。     

扁平绕带式压力容器筒壁应力可控性设计分析

通过对扁平绕带式压力容器结构分析,提出通过合理控制扁平绕带式压力容器钢带预应力,控制容器筒体的应力分布。