超声冲击消除焊接接头残余应力的试验研究

采用超声冲击方法对Q345B板材对接焊接接头进行超声冲击试验,采用不同冲击电流和时间,研究超声冲击消除焊接接头残余应力的效果。研究表明,当超声冲击时间一定时,提高冲击电流值可以提高残余应力消减率,但当冲击电流值一定时,延长冲击时间对消减率并没有明显影响。超声冲击处理可以消除Q345B焊接接头残余应力,消除率达到86.1%～122.5%,并且可以将Q345B对接接头热影响区残余拉应力转变为压应力,该方法消除焊接残余应力效果良好。     

超声冲击处理对TA15钛合金焊接接头组织和性能的影响

采用光纤激光焊对TA15钛合金进行无间隙对接焊,选取6组不同的超声冲击处理时间对焊接接头显微组织、力学性能、晶粒尺寸、应力分布和粗糙度进行研究,确定较优的超声冲击处理时间。结果表明,当冲击电流为1. 2 A、振动频率为20 k Hz、超声冲击处理时间为75 min时,可获得50μm厚的致密强化层,103. 4 nm的晶粒尺寸,其粗糙度为34. 13μm。经过超声冲击处理后,减少了气孔、缩松等缺陷,使得拉应力转变为压应力,接头的应力集中得到极大地改善,对钛合金材料组织和性能的提高有积极的促进作用。     

焊接残余应力对激光冲击应力场影响的数值分析

本文通过有限元方法分析了焊接残余应力场对激光冲击处理后形成的残余应力场的影响。以法国电力公司核反应堆冷却系统的镍合金600对接焊圆管为原型,建立了激光冲击处理的非线性弹塑性有限元模型,并引入焊接残余应力场作为数值模拟的初始条件。有限元结果表明,在有初始焊接残余应力场的情况下,一次冲击后仍能使镍合金600对接焊圆管形成残余压应力表层,但是最大压力值和压应力化深度减小;多次冲击后压应力化程度增大,且7次冲击后趋于饱和,初始焊接应力场对冲击残余应力场的影响变小,可忽略不计。     

外加电位对X80钢在满洲里土壤应力腐蚀的影响

针对埋地管道应力腐蚀开裂(SCC)问题,开展了X80管线钢(X80钢)在满洲里土壤模拟溶液中的SCC研究,以期对X80钢的SCC防护提供数据支撑。采用交流阻抗技术、动电位极化技术和慢应变速率拉伸实验研究了X80钢在不同外加电位下满洲里土壤模拟溶液中的SCC行为,并用扫描电镜观察了断口表面微观形貌。结果表明:自腐蚀电位下,X80钢裂纹萌生于点蚀坑处,SCC机制为阳极溶解(AD);在外加电位为-850 mV和-930 mV时,X80钢的应力腐蚀受到抑制作用,SCC敏感性较低,-850 mV为最佳阴极保护电位。这两个电位下X80钢SCC机制为AD和氢致开裂(HIC)混合机制,其中-930 mV下SCC机制由HIC占主导地位;在外加电位为-1 000 mV和-1 200 mV时,X80钢表现出较高的SCC敏感性,SCC机制为氢和应力协同作用下的HIC。     

海工用X100管线钢管的焊接工艺及接头质量分析

采用海洋平台建造中符合AWS D1. 1标准的6GR位置特定坡口形式,利用焊条电弧焊(SMAW)单面焊双面成形工艺焊接某国产X100管线钢管。通过拉伸、冲击、弯曲试验检测接头的力学性能,通过光学显微镜对比分析X100管线钢焊接接头坡口两侧熔合线显微组织。结果表明,该公司生产上所用的X100管线钢管在6GR位置通过合适的预热及焊接热输入可以得到满足结构使用性能要求的焊接接头,但接头未开坡口侧在-40℃冲击时,冲击吸收能量相对较低,原因是未开坡口侧(直边)熔合线晶粒粗化严重,大晶粒晶界有相互连接趋势。     

豪克能消除焊接应力设备的研究与应用

豪克能消除应力设备是国外较为广泛使用的提高焊接接头疲劳寿命、消除焊接残余应力和进行局部强化处理的焊后处理设备。它的基本工作原理是向被处理的金属部位输入大能量的豪克能并使工具头以每秒几万次的频率冲击金属表面,从而达到消除残余应力提高疲劳寿命的目的。通过对120t的炼钢转炉壳体和对大亚湾核电站中微电子设备进行消除焊接应力试验及对低碳钢Q235-B与0345板材的对接接头和十字接头形式标准焊接试件进行疲劳性能试验证明：豪克能焊接应力消除设备对焊接应力的消除率可达90％以上、疲劳寿命可提高30倍以上。     

盾构隧道复合管片接头板焊接的数值模拟研究

焊接变形及残余应力的存在会对焊接构件的应用产生不利影响,进行结构构件焊接变形的高精度预测和残余应力的分布预测具有重要的工程意义。本文针对复合管片接头板构件,利用ABAQUS有限元软件建立复合管片面板及接头板的三维实体模型,同时考虑材料非线性、几何非线性和边界非线性,并基于热-弹-塑性有限元法对接头板四周的焊接进行了模拟,分析了不同焊接顺序、环境温度及拘束状态对接头板焊接变形和残余应力的影响。结果表明:焊接顺序对复合管片接头板的变形有明显影响,采用平行对称焊接,先焊接长焊缝,后焊接短焊缝的顺序可有效降低Z方向的变形量;环境温度会改变构件残余应力的分布,随着环境温度的升高,纵向残余拉应力逐渐较小,距接头板上边缘约140～280 mm范围内的压应力也减小,而其他范围内的压应力呈增大趋势;拘束状态对纵向残余拉应力的影响较小,对纵向残余压应力的分布影响较大,在相距600～840 mm范围内设置两个对称拘束可对焊接变形起到控制作用。     

输气管道壁面凹坑的应力应变分析

研究管道壁面凹坑对输气管道运行的影响。以X60管线钢输气管段为例,对残余应力测试及分析和内压-应变测试及分析进行探讨。结果表明,凹坑深度对残余应力的影响很大,当凹坑深度超过6%时,实测残余应力已经超过管道的屈服极限,此时管道必须进行维护处理。对管道凹坑进行内压-应变同步分析,提出了输气管道表面凹坑内压-应变测试方法,以确定凹坑的风险。     

冷凝罐接管与筒节焊接应力的有限元分析

通过ANSYS有限元软件,对冷凝罐接管与筒节多层焊的焊接过程进行了数值模拟。针对接头的马鞍形空间轨迹特点,编写了沿焊道移动的热源方程,并采用逐层激活与逐步激活的生死单元技术实现了接头的熔敷过程模拟,使模拟与实际施焊过程相符。通过模拟研究了焊接过程动态温度场、应力场和焊接残余应力的分布状况。结果表明:焊接残余应力主要集中在接头的焊缝区和热影响区,周向应力与径向应力均在内层焊道中较高。在焊缝外表面沿接管周向应力为拉伸应力,其余为压应力,内表面三向均为拉伸应力。筒节一侧的焊趾与焊根部位应力较高,且为三向拉伸应力,是裂纹易发部位。文中所建立的沿马鞍形轨迹移动的热源方程可用于该类接头的焊接过程研究。     

铁素体不锈钢焊接的研究和发展现状

主要综述了国内外铁素体不锈钢焊接的研究和发展现状,焊接热过程会导致铁素体不锈钢接头焊缝和HAZ晶粒严重长大,从而造成接头塑韧性和耐蚀性能下降。激光焊、复合热源焊接、脉冲电弧焊、搅拌摩擦焊等新型焊接方法被用来焊接铁素体不锈钢以获得性能更好的接头。并且可以通过控制热输入、提高冷却速度、添加稳定元素、电磁搅拌或超声振动来细化晶粒,提高接头性能。近年来,模拟计算也被用到铁素体不锈钢焊接的研究当中。     

Numerische Analyse geschweißter Verbindungen von Duplexstahl und Quarzglas

Numerical analysis of welded joints between duplex steel and quartz glass. Welded joints are a vital element in structural engineering. Originating from conventional carbon steel welding in construction, recent advancements in welding technology now allow the joint of modern high‐strength steel and glass materials. With today's methods, an analysis of the welded joints' structural behaviour can be conducted by experiment, as well as by numerical analysis. Particularly for the numeric analysis, capturing the non‐linear thermal and mechanical properties of the materials is important, in order to allow a realistic determination of temperature, microstructure and residual stresses for different types of joints. Simulations of multi‐layered weld joint on duplex steel show, that a targeted heat treatment during MAG‐welding by variation of the welding parameters achieves a beneficial ratio between ferrite and austenite which, for example, ensures a high resistance of the weld to corrosion. The material quartz glass can generally be welded as butt‐weld with a CO₂‐laser. The simulations of a welded joint of a plate and a pipe show, that an optimization of the welding technology of preheat laser beam and welding laser beam is necessary, in order to reduce the thermal impact during the welding process, as well as residual stress in the joint. At the Department of Steel Structures at the Bauhaus‐Universität Weimar, numerical simulations of welded joints between steel and glass materials are a current and topical research focus.     

Fatigue Resistance Improvement of Welded Joints by Bristle Roll-Brush Grinding

In the periodic repainting of steel bridges, often the steel surface has to be prepared by using power tools to remove surface contaminants, such as deteriorated paint film and rust, and to increase the adhesive strengths of the paint films to be applied newly. Surface preparation by bristle roll-brush grinding, which is a type of power tool, may additionally introduce compressive residual stress and increase the fatigue resistance of welded joints owing to the impact of rotating bristle tips. In this study, fatigue tests were conducted for longitudinally out-of-plane gusset fillet welded joints and transversely butt-welded joints to evaluate the effect of bristle roll-brush grinding prior to repainting on the fatigue resistance of the welded joints. The test results showed that bristle roll-brush grinding introduced compressive residual stress and significantly increased fatigue limits by over 50%.     

定向钻技术对管线钢应力腐蚀开裂的影响

结合工程实际情况,分析计算了定向钻施工造成的管道应力分布和应力集中的值。利用电化学测试技术和慢应变速率拉伸试验(Slow Strain Rate Tests,SSRT),研究了X70钢在定向钻泥浆中的电化学行为和应力腐蚀开裂(Stress Corrosion Cracking,SCC)行为。X70钢和定向钻泥浆体系为电化学活化体系,自然腐蚀速率较低;X70钢在无添加剂的定向钻泥浆中,不具备发生SCC的条件;当定向钻泥浆含有一定量Na2CO3和NaHCO3后,X70钢具有一定的高pH值环境SCC敏感性。     

管线钢在近中性pH环境中的应力腐蚀破裂特性

文章研究了管线钢X60和SS400在上海周边相关土壤环境中的应力腐蚀破裂（SCC）特性。根据上海周围土壤类型分布和管网分布采样,管材取自实际使用的管线,实验方法主要是在各种电极电位下的慢应变速率拉伸。结果表明土壤类型和电极电位对两种钢的应力腐蚀破裂敏感性都有显著影响。讨论了SCC特性的内在机理和工程意义。     

Effect of compression overload on fatigue strength improved by ICR treatment

ICR (Impact Crack-closure Retrofit) treatment was developed for extending fatigue life of cracked steel structures by closing the fatigue crack opening. By applying the ICR treatment to as-welded condition, compressive stress remains at weld toe. Therefore, ICR treatment can be used for the improvement of fatigue strength of welded joint at the same level of the other fatigue strength improved techniques. If a compression overload is subjected after ICR treatment, however, the residual compressive stress at weld toe will shift the tensile stress region. Accordingly, improved fatigue strength of welded joints by ICR treatment will be reduced after the compression overloaded. In order to investigate the effect of the compression overload on fatigue strength improved by ICR treatment, fatigue tests of out-of-plane gusset specimens were carried out. As the results, fatigue strength improved by ICR treatment was hardly reduced under the compression overload condition of nominal stress of ?190 MPa.     

由裂纹尖端张开位移设计曲线确定X70钢裂纹长度临界值

裂纹长度临界值一直是结构安全性评估的重要指标,确定裂纹长度临界值的传统方法限于线弹性阶段且不适用于力学性能不均匀的焊接接头。在考虑焊接残余应力的情况下,使用有限元软件ANSYS计算出焊接残余应力的数值,依据英国BS 7448规范对X70钢断裂韧度裂纹尖端张开位移(CTOD)值进行测试,进而根据英国PD6493规范导出的CTOD设计曲线,对X70钢在ASME规范的设计应力下贯穿裂纹长度临界值进行确定。这种方法适用于弹塑性情况及力学性能不均匀的焊接接头。CTOD设计曲线在X70钢贯穿裂纹长度临界值中的应用科学严谨,兼顾了安全性与经济性,可供压力容器、管道生产和结构安全性评估时借鉴。     

Effect of stress ratio on the enhancement of fatigue strength in high performance steel welded joints by ultrasonic impact treatment

In this study, we conducted fatigue tests under various stress ratios using cruciform welded joints to confirm the benefit of Ultrasonic Impact Treatment (UIT) for the fatigue strength of welded joints. The material used in the experiment is the JIS SBHS500 high performance steel for bridges. The fatigue life of the peened weld joint by UIT is significantly longer than that of as-welded joints, especially at a low stress ratio. We also estimated the fatigue life of these cruciform joints by crack growth analysis based on the crack opening and closure simulation using the modified strip-yielding model, accounting for the residual stress distribution created by welding or UIT. These estimation results demonstrate good agreement with experimental results obtained at various stress ratios.     

埋地钢质管道应力腐蚀开裂及其预防

阐述了埋地钢质管道应力腐蚀开裂的影响因素和类型,总结了国内外典型的管道应力腐蚀开裂事故和研究状况,提出了预防措施。     

Investigation on compressive behavior of grout-filled GFRP tube repairing corroded CHS T-joint

为研究GFRP管夹层灌浆修复锈蚀钢管节点的受压性能，改变支主管直径比、锈蚀率及修复构造，完成8个T形圆钢管节点的支管轴向受压静力加载试验。通过对主管加速锈蚀及GFRP管夹层进行灌浆修复，实测各钢管节点的破坏模式、荷载 变形曲线和荷载 应变曲线，分析节点受压承载力和初始刚度。结果表明：质量损失10%的主管锈蚀会使T形圆钢管节点受压承载力下降近20%，但未改变节点的失效模式；主管GFRP管夹层灌浆修复使锈蚀T形圆钢管节点的受压承载力提高100%左右，且较未锈蚀对比T形圆钢管节点可提高约70%；GFRP外管的约束作用是提升节点受压性能的关键，采用无约束作用的PVC外管会使灌浆层过早开裂并剥离，修复效果一般；主管焊接连接键可以增强钢管与灌浆夹层之间的锚固，其对PVC管夹层灌浆修复锈蚀节点的提升作用更明显，但对有GFRP约束修复T形圆钢管节点的贡献很小。建立并验证了各类T形圆钢管节点的有限元模型，揭示未修复节点主管塑性化变形失效机制，以及GFRP管夹层灌浆的约束作用对于锈蚀节点受压性能的提升机理。