激光冲击对X80管线钢焊接接头应力腐蚀的影响

利用激光冲击波对X80管线钢焊接接头进行了表面改性处理,通过慢拉伸试验分析了X80管线钢焊接接头在NACE溶液(不含H2S和含饱和H2S)的H2S应力腐蚀开裂(SCC)行为,研究了经激光冲击处理后焊接接头表面细化的晶粒和残余应力对H2S应力腐蚀的影响机理.结果表明:激光冲击处理可改善焊接接头的表面质量,形成强化层,产生晶粒细化和残余压应力,获得细小均匀的针状铁素体组织,因大量晶粒承受氢压,可显著提高材料的临界应力值.应力腐蚀敏感指数ISCC比原始状态下降了5.84％,提高了X80管线钢焊接接头抗SCC的性能.激光冲击处理使X80管线钢焊接接头表面粗糙度有所上升,在一定程度上又降低了X80管线钢焊接接头SCC抗力.     

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.     

正交异性钢桥面板结构体系的疲劳破坏模式和抗力评估

正交异性钢桥面板的疲劳问题属于包含多疲劳破坏模式的结构体系疲劳问题。基于这一本质特性,以典型的正交异性钢桥面板结构体系为研究对象,由结构体系的主导疲劳破坏模式出发,提出正交异性钢桥面板结构体系疲劳抗力评估的新方法。以纵肋与顶板焊接细节和纵肋与横隔板交叉构造细节为主要研究对象,设计8个足尺节段模型,主要包括传统纵肋与顶板焊接细节、新型镦边纵肋与顶板焊接细节和纵肋与横隔板交叉构造细节,通过模型试验研究了两类重要构造细节的主导疲劳破坏模式和实际疲劳抗力,在此基础上结合切口应力评估方法探讨正交异性钢桥面板构造细节切口应力S-N曲线方程、结构体系的主导疲劳破坏模式等关键问题。研究结果表明：传统纵肋与顶板焊接细节和新型镦边纵肋与顶板焊接细节的主导疲劳破坏模式均为疲劳裂纹萌生于焊根并沿顶板厚度方向扩展,二者的实际疲劳抗力基本相同;纵肋与横隔板交叉构造细节的疲劳破坏模式为焊趾开裂沿纵肋腹板方向扩展;对于研究对象而言,萌生于纵肋与顶板焊接细节焊根并沿顶板厚度方向扩展的疲劳破坏模式为控制结构体系疲劳抗力的主导疲劳破坏模式。     

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.     

焊接管节点疲劳研究综述

为加深对焊接管节点疲劳问题的认识,对焊接管节点名义应力法、热点应力法、切口应力法和断裂力学法4种常用疲劳评估方法应用现状和存在问题进行介绍,从疲劳效应（热点应力集中系数）和抗力（热点应力幅S N曲线）2个方面对首推的热点应力法研究现状进行总结,探讨了管节点结构形式的发展趋势。结果表明:焊接管节点常用四大疲劳评估方法中名义应力法应用最广,但过于保守,热点应力法最被推崇,但仍有待进一步完善,切口应力法实施难度大,尚未在规范中使用,断裂力学法则适用于剩余疲劳寿命评估;对于传统的圆形和矩形钢管节点,已形成了较为系统的热点应力评估方法,对热点应力集中系数最大值可能发生位置、外推区域、热点应力集中系数计算公式、壁厚效应修正系数等方面进行了明确的规定;在传统的圆钢管和矩形钢管节点基础上,创新节点形式,提出了钢管混凝土节点、PBL加劲型钢管混凝土节点、圆管 方管节点和鸟嘴式节点,对比传统钢管节点,钢管混凝土节点热点应力集中系数降幅在25%以上,PBL加劲型矩形钢管混凝土节点降幅在50%以上,圆管 方管节点和鸟嘴式节点降幅则介于圆形钢管和矩形钢管节点之间。     

Fatigue strength evaluation of welded structural details in corrugated steel web girders

Fatigue strength evaluation of welded structural details is of practical significance in the design of corrugated steel web girders in highway bridges and industrial structures. In this paper, the fatigue strengths of corrugated steel web girders with several welded structural details and welding methods are analytically examined by fatigue tests of corrugated web beams and small-size welded joints. The stress concentration & distribution characteristics of corrugated web beams were analysed using finite element analysis. The beam test results showed that the structure with scallops or notches in the flange has lower fatigue strength and that with butt joints is prone to suffer from shear crack on the corrugated web. Within the inside range of the scallop, the stress concentration becomes greater with the increase of scallop radius and the tension flange contributes significantly to the bending capacity of corrugated steel web beams. The tests for small-size welded joints indicated their applicability in the analysis and prediction of S-N relationship of the test corrugated steel web beams. Finally, the fatigue crack propagation lives of weld joints were compared with those of test corrugated steel web beams with respect to related design Categories of the AASHTO LRFD Bridge Design Specifications.     

Fatigue strength improvement of welded joints by blast cleaning for subsequent painting

In the fabrication of steel bridges, prior to painting, blast cleaning is performed to clean the surfaces and to increase the adhesive properties of the surfaces for the subsequent painting. In addition to these objectives, blast cleaning can improve the fatigue strength of welded joints, as a result of the impact of forcibly propelled abrasive materials on the welded joints. A series of fatigue tests were carried out on the five different types of welded joints: one-side out-of-plane gusset fillet welded joints, both-side out-of-plane gusset fillet welded joints, non-load-carrying rib fillet welded cruciform joints, butt welded joints, and a large-scale model beam with out-of-plane gusset welded joints, and under the three different types of load conditions: uniaxial tension, out-of-plane bending, or in-plane bending stress cycles. Drawing on previous fatigue test results that include unpublished data, this paper presents the beneficial effects of blast cleaning for the subsequent painting applications on the fatigue strength improvement of welded joints and also presents a simple quality control method for the blast cleaning process that improves the fatigue strength.     

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。     

基于等效结构应力的钢框架焊接梁柱节点低周疲劳评估

在地震作用下钢框架梁柱焊接节点会发生低周疲劳现象,进而导致结构发生破坏。本文基于等效结构应力法提出一种高层钢框架梁柱焊接节点低周疲劳评估方法。首先,结合有限元多尺度模拟方法,建立包含翼缘及腹板焊缝细节的钢框架梁柱焊接节点多尺度模型。其次,利用不同单元尺寸多尺度模型,验证结构应力的网格不敏感特性,进而通过等效结构应力法评估钢框架梁柱焊接节点的疲劳寿命。结果表明,采用等效结构应力法可消除网格的敏感性,在往复荷载作用下,靠近工艺孔焊缝应力水平高于远离工艺孔焊缝,翼缘中心焊缝寿命最低,裂纹最先产生于翼缘焊缝中心处,评估方法为实际工程提供技术支持。     

高性能桥梁钢典型焊接接头疲劳性能试验研究

针对Q500qE高性能钢两种典型焊接接头,包括对接焊缝和横向角接焊缝,设计疲劳试件。其中对接焊试件包括两种形式,分别为板厚56mm和8mm的对 接焊试件;横向角接焊缝试件的主板厚56mm、附连件厚20mm。对三组试件进行了有限元分析,掌握了试件的应力分布状况及薄弱环节,验证了试件设计的合 理性。随后针对三组试件展开了疲劳试验,掌握了不同类型焊接接头的破坏位置及破坏形式。根据试验结果拟合出了三组试件的S-N曲线,并与普通钢的疲 劳性能进行比较,表明Q500qE高性能钢的这两种典型焊接接头的疲劳强度略高于普通钢。采用目前规范规定的疲劳强度容许值进行抗疲劳设计是合理可行的,并且具有足够的安全余量。     

基于盲孔法的高强焊接圆钢管表面残余应力试验研究

为研究高强焊接圆钢管残余应力分布模式,基于盲孔法对21个高强焊接圆钢管的5个外表面、1个端部内表面纵向残余应力分布进行测量;对盲孔法应变释放系数A、B进行平面试验及平面有限元标定,验证有限元标定的可靠性;进行柱面有限元标定并依据形状改变比能修正法对试验测量结果进行塑性修正,提出埋弧焊接、高频焊接圆钢管外表面纵向残余应力分布模型。研究结果表明：柱面有限元模型可弥补应变计弧面形状造成的误差,与平面试验标定结果相比,对于截面规格为■325×8的埋弧焊接圆钢管标定系数A误差可达6.1%,对于截面规格为■356×10的埋弧焊接圆钢管,标定系数B误差可达5.0%;与平面有限元模型标定结果相比,由柱面标定得到的应变释放系数A随直径增大而减小、系数B随直径增大而增大,并逐步趋近于平面标定结果。沿着焊接方向1/4、1/2、3/4柱高截面最大纵向残余应力数值相近,最大残余拉、压应力分别为0.96■、-0.27■。高频焊接圆钢管端部内表面与外表面残余应力分布模式不同,外表面以残余拉应力为主且最大为0.46■,内表面以残余压应力为主且最大为-0.37■。提出的纵向残余应力分布模型与实测数据吻合较好。     

Experimental research on surface residual stress of high strength welded circular steel tube based on hole-drilling strain-gage method

为研究高强焊接圆钢管残余应力分布模式，基于盲孔法对21个高强焊接圆钢管的5个外表面、1个端部内表面纵向残余应力分布进行测量；对盲孔法应变释放系数A、B进行平面试验及平面有限元标定，验证有限元标定的可靠性；进行柱面有限元标定并依据形状改变比能修正法对试验测量结果进行塑性修正，提出埋弧焊接、高频焊接圆钢管外表面纵向残余应力分布模型。研究结果表明：柱面有限元模型可弥补应变计弧面形状造成的误差，与平面试验标定结果相比，对于截面规格为φ325×8的埋弧焊接圆钢管标定系数A误差可达6.1%，对于截面规格为φ356×10的埋弧焊接圆钢管，标定系数B误差可达5.0%；与平面有限元模型标定结果相比，由柱面标定得到的应变释放系数A随直径增大而减小、系数B随直径增大而增大，并逐步趋近于平面标定结果。沿着焊接方向1/4、1/2、3/4柱高截面最大纵向残余应力数值相近，最大残余拉、压应力分别为0.96fy、-0.27fy。高频焊接圆钢管端部内表面与外表面残余应力分布模式不同，外表面以残余拉应力为主且最大为0.46fy，内表面以残余压应力为主且最大为-0.37fy。提出的纵向残余应力分布模型与实测数据吻合较好。     

Fatigue performance of tubular X-joints with PJP+ welds: I — Experimental study

This study examines the fatigue performance of tubular joints fabricated using a new type of enhanced partial joint penetration weld details under constant-amplitude brace in-plane bending actions. The experimental program includes four cyclic tests on two large-scale X-joints, each with a different surface treatment near the weld toe. The experimental results confirm the satisfactory fatigue performance of the tubular X-joints welded using enhanced partial joint penetration welds in comparison with the S-N curves developed for tubular joints with complete joint penetration welds, and demonstrate the significant improvement on the fatigue life rendered by the weld surface grinding and toe grinding. Root fatigue cracking occurs only in specimens with post-weld toe-grinding treatment which enhances the fatigue life for toe cracking.     

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 life evaluation of welded joints considering the local multiaxial stress/strain states and numerically determined residual stresses/strains

This paper puts forward a kind of calculation method of estimating fatigue crack initiation life by considering welding residual stresses as initial stresses. The numerical method could be used to quantitatively analyze the influence of residual stresses on the cumulative fatigue damage. In order to gain the distribution of weld-induced residual stresses, the FE analyses as well as measurements were carried out. Based on critical plane approach, analysis of damage parameters was performed considering both welding residual stress and biaxial loads. Subsequently, validity of the proposed numerical method is verified by analyzing fatigue test results for several typical welded joints. It is concluded that the result of the present method is closer to the experimental value than that obtained with empirical formula method in the estimation of fatigue crack initiation life of welded structures.     

铸钢节点对接焊缝有效缺口应力分析

为了研究铸钢节点对接焊缝的疲劳性能和寿命评估方法,对一种常用的铸钢热轧钢对接焊缝试件进行了疲劳试验研究,得到了刚度、位移与疲劳寿命阶段之间的关系。根据疲劳试验现象和断面的电镜扫描结果,提出了该类试件的疲劳失效机理。此外,采用有效缺口应力法预测了铸钢节点对接焊缝的疲劳寿命,并在考虑了平均应力和焊接残余应力的前提下,提出了改进的有效缺口应力法,分别将预测结果与实测疲劳寿命进行了对比。研究结果表明:铸钢节点对接焊缝的疲劳过程可分为稳定阶段和断裂阶段。稳定阶段占总寿命比例≥80%,断裂阶段≤20%。有效缺口应力法能在一定程度预测疲劳寿命的变化趋势,但结果偏危险,改进的有效缺口应力法能提供较安全的预测结果。     

网架焊接空心球节点静力及疲劳性能研究

焊接空心球节点是网架结构合理的节点型式。本文从理论和试验两方面对其静力及疲劳性能进行了试验研究。利用有限元计算和大量应变实测基本摸清了单向受拉弹性阶段球面应力分布的规律,通过理论及200多个试验数据的综合分析,提出了新的简单、合理的承载力计算公式。通过四种规格15个试件的疲劳试验,得到了S-N曲线,借助薄壳理论分析求得SCF计算公式,并将热点应力幅的概念用于研究,建立了适用于各种管球配合的剖口焊情况下疲劳验算方法。     

高温作用后高强Q690钢焊接截面残余应力试验研究

焊接中的不均匀受热和冷却使钢材内部产生残余应力,残余应力会降低钢构件的刚度、稳定承载力和疲劳性能。钢构件在高温下的强度退化、塑性和蠕变变形会引起截面残余应力改变,从而影响其火灾下及火灾后承载力。为此,采用高强Q690钢材制作了6个焊接构件,包括H形、箱形两种截面形式。利用切条法测量其在常温（20℃）下、600℃和800℃高温作用后的截面残余应力,得到不同温度作用后残余应力的大小与分布。结果表明：高温作用后,残余应力有不同程度的释放;经历600℃作用后,箱形与H形截面残余应力幅值均下降至常温下的约35%;经历800℃作用后,箱形与H形截面残余应力幅值均下降至常温下的15%以下。基于试验结果,提出Q690焊接截面残余应力分布模型及残余应力幅值随受火温度变化的折减系数。     

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.     

国际期刊导读

给出波纹钢腹板与翼缘板焊接节点的疲劳评估方法。对这种焊接节点的失效模式、应力分布和疲劳强度进行试验研究和有限元分析。由于节点处弧线焊缝的应力集中对疲劳寿命的评估十分重要,因此,对这类几何效应进行了研究,并对其应力特性进行了讨论。结果表明,由于节点处弧线焊缝疲劳关键点的应力集中,曲率半径与波纹高度之比越小,波纹和曲率角度的影响越显著,反之亦然。可将十字形节点的S-N曲线作为极限值,与不同波纹角度焊接节点的疲劳强度进行对比。所提出的方法考虑了复合应力条件,可用于波纹板焊接节点的疲劳评估。该方法也从理论上对残余应力的影响进行了讨论。