多次水下爆炸作用下钢板与焊接钢板冲击损伤特性

为了研究舰船结构在多次水下爆炸载荷作用下的抗爆抗冲击能力,基于水下爆炸鼓胀试验分别开展了5 mm、12 mm的船用A32背空钢板及焊接板的多次水下爆炸试验,得到了钢板与焊接板的塑性变形历程,测量并计算了钢板与焊接板受冲击区域沿半径各点处的挠度及厚度减薄率,分析了钢板与焊接板的塑性变形规律。结果表明:多次水下爆炸载荷作用下,焊接板与钢板的塑性变形形貌呈类球冠形,二者的厚度减薄率从中心位置到边界处呈先减小再增大的趋势,但焊接板的挠度小于钢板的挠度。A32钢板的变形模式主要为弯曲和拉伸变形,焊接板以弯曲变形为主。持续增加的水下爆炸载荷导致钢板中心位置与边界处拉伸断裂,而焊接板的焊缝及其热影响区发生脆性断裂。     

A572 Gr.50厚板对接焊缝断裂性能研究

A572 Gr.50厚板常用于锅炉钢结构大板梁的加工制作,其对接焊缝易存在焊接裂纹缺陷。为评定含缺陷的锅炉钢结构大板梁的安全性,通过焊接接头模拟制作实际大板梁下翼缘的A572 Gr.50厚板对接焊缝,分别对其母材、焊缝金属及热影响区材料进行了系列单轴静力拉伸试验、冲击韧性试验和直三点弯曲断裂韧度试验,并结合有限元分析对A572 Gr.50厚板对接焊缝存在裂纹缺陷时的断裂性能进行了研究。研究结果表明:厚板对接焊缝母材、焊缝和热影响区材料基本力学性能均能满足规范要求,均具有良好的塑性变形能力;随温度的降低,母材、热影响区及焊缝处的夏比冲击功减少,但均具有良好的冲击韧性;比较而言,母材的抗低温冷脆性能最好,焊缝最差;母材、焊缝和热影响区3个区域中焊缝的断裂韧度最差;厚板对接焊缝接头的焊缝区是大板梁焊接缺陷安全性评估的重点控制区域;基于断裂力学,可以运用有限元软件方便的对带裂缝的工作状态下工作的钢结构构件的断裂性能进行分析,保证其安全性。     

焊缝对拼焊板成形性能的影响

采用激光焊接技术对冷轧薄钢板进行拼焊,通过对拼焊板进行拉伸试验和模拟成形性能试验,研究分析了焊缝对拉伸性能参数和成形性能参数的影响,比较了拼焊板与母材性能的差异,分析了强度比和厚度比对塑性变形的影响及应变分布。     

基于材料静动态力学性能分析的SiCp/Al本构模型构建

基于SiCp/Al复合材料的静态和动态力学性能分析,构建SiCp/Al复合材料的本构模型。针对体积分数为20%的SiCp/2a14Al复合材料采用电子万能试验机进行准静态拉伸试验,研究材料的静态力学性能;采用霍普金森压杆试验进行不同温度(20～400℃)、不同应变率(500～3 000 s^-1)动态压缩试验,分析材料的动态力学性能。基于材料静态及动态下应力-应变试验数据构建SiCp/Al复合材料的Johnson-Cook(JC)本构模型,并通过遗传算法对模型进行优化。结果表明,SiCp/Al复合材料在准静态条件下表现出应变强化效应;在动态载荷条件下,材料流动应力随着应变速率的增加而增加,表现出应变率强化效应,这与碳化硅颗粒的体积分数有关;随着温度的增加,流动应力减小,表现为温度软化效应。最小二乘法拟合的JC模型与试验值的平均误差较大,经过遗传算法优化后模型误差减小,能够准确预测SiCp/2a14Al复合材料的流变行为。     

拼焊板焊接工艺及其对拼焊板塑性变形影响的试验研究

通过拼焊板试件拉伸试验对拼焊板的塑性变形性能进行了分析研究 ,讨论了拼焊板的几种实用焊接技术 ,给出了拼焊板的机械性能参数 ,比较了焊缝处于拉伸试样不同位置时拼焊板与母材的拉伸试验结果 .分析了焊缝分布对拼焊板塑性变形性能的影响 ,以及如何优化焊缝位置以提高拼焊板的整体塑性变形能力 .     

车用TRIP590钢光纤激光焊接接头组织与性能研究

为了促进先进高强钢激光焊接技术的发展,采用光纤激光器对1.5mm厚的TRIP590钢板进行焊接,对焊接接头的微观组织、硬度以及拉伸性能进行了研究,分析了焊接速度对组织、性能的影响。结果表明:焊缝组织主要为板条状马氏体,热影响区可分为完全淬火区和不完全淬火区。焊接接头硬度分布不均匀,在热影响区或焊缝处硬度最高。随着焊接速度提高,热影响区马氏体含量增多,贝氏体含量减少,热影响区和焊缝组织变得细小。焊接速度为3~5m/min时,拉伸试样均断裂在母材,断后延伸率均超过30%,随着焊接速度提高,断后延伸率也有所提高,强塑积(PSE)均在20000MPa%以上,拉伸变形过程中相变诱发效应显著,大部分残余奥氏体转变为马氏体,在提高材料塑性的同时也提高了强度,实现了高强度和高塑性的统一。     

高强度钢-普通钢拼焊板热冲压成形机理研究

目的 研究高强度钢-普通钢拼焊板热冲压成形机理.方法 对高强度22MnB5钢-Q235钢拼焊板高温力学性能及U形热弯曲件的微观组织和力学性能进行实验研究,对高温下拼焊板协调变形进行数值分析,研究拼焊板高温力学性能和热弯曲件微观组织、力学性能的影响机制及拼焊板热变形协调机制.结果 焊缝与拉伸方向平行时,800℃下拼焊板伸长率不高,两侧母材形变量相差较大;900℃和950℃下,两种母材形变量接近.焊缝与拉伸方向垂直时伸长率较低.热弯曲件"软"、"硬"区抗拉强度差为500～1000 MPa,伸长率差为5％～20％.结论 焊缝与拉伸平行时拼焊板塑性较好,温度越高焊缝两侧变形较一致,焊缝与拉伸垂直时拼焊板力学性能主要取决于"软"区母材的性能.揭示了高强度22MnB5钢-Q235钢拼焊板热冲压成形机理.     

船板钢焊接接头的断裂失效行为及GTN模型的数值分析

船舶钢结构皆采用焊接方法建造而成,在实际工况及环境载荷作用下,焊接接头的力学性能及其断裂强度,直接影响船舶整体结构的强度和寿命。该文针对常用的船板钢材料(Q345和Q690),首先对母材进行单向拉伸试验,获得其各自的应力-应变曲线,进而评估其断裂性能;基于Gurson-Tvergaard-Needleman (GTN)损伤模型,通过程序代码的调试和一系列的数值模拟分析,提出了母材本构关系的表达函数及最优GTN模型参数,且与实测的应力-应变曲线高度吻合。同时,针对满足焊接规范要求的船板钢对接焊接头,进行了单向拉伸试验获得其应力-应变曲线;考虑焊缝微观缺陷以及焊接残余应力的影响,提出修正GTN损伤模型中的初始空穴体积分数f₀和材料的幂函数塑性强化参数,预测焊接接头的断裂强度,且与试验测量数据吻合一致。     

Ti17合金电子束焊接接头的性能及组织分析

分析了Ti17合金真空电子柬焊接接头的显微组织结构及其显微硬度分布规律,并结合室温和高温拉伸试验结果分析了焊接接头的力学性能。结果表明,用电子束焊接方法焊接的Ti17合金其焊缝区和热影响区显微组织为β相基体上分布着细长针状α相,母材为典型的α＋β双相网篮组织,焊后焊缝晶粒细化,焊接接头的焊缝区硬度最高,焊缝的抗拉强度和缺口敏感性均高于母材。     

预拉伸控制铝合金焊接变形

在预拉伸应力作用下,焊接了厚度为4mm的5A05铝合金试板,通过焊接试板挠曲变形量的测定,探讨了预加拉应力对铝合金焊接变形的影响。试验结果表明,预拉伸焊接法可以有效减小铝合金薄板焊缝处的纵向挠曲变形量,在弹性应力范围内,随着预拉伸应力的增大,试板的焊接变形逐渐变小。初步分析认为,预拉伸应力扩大了高温下焊缝附近的塑性变形区,从而增强了冷却过程中该区域抗塑性拉应变的能力,减小了焊件的挠曲变形。     

Effects of mechanical heterogeneity on the tensile and fatigue behaviours in a laser-arc hybrid welded aluminium alloy joint

The effects of mechanical heterogeneity on the tensile and high cycle fatigue (10⁴–10⁷ cycles) properties were investigated for laser-arc hybrid welded aluminium alloy joints. Tensile–tensile cyclic loading with a stress ratio of 0.1 was applied in a direction perpendicular to the weld direction for up to 10⁷ cycles. The local mechanical properties in the tensile test and the accumulated plastic strain in the fatigue test throughout the weld’s different regions were characterized using a digital image correlation technique. The tensile results indicated heterogeneous tensile properties throughout the different regions of the aluminium welded joint, and the heat affected zone was the weakest region in which the strain localized. In the fatigue test, the accumulated plastic strain evolutions in different subzones of the weld were analyzed, and slip bands could be clearly observed in the heat affected zone. A transition of fatigue failure locations from the heat affected zone caused by accumulated plastic strain to the fusion zone induced by fatigue crack at pores could be observed under different cyclic stress levels. The welding porosity in the fusion zone significantly influences the high cycle fatigue behaviour.     

热成形淬火对QP1180/22MnB5激光拼焊板组织与性能的影响

目的 对QP1180和22MnB5激光拼焊板进行热成形试验,以解决超高强钢板材焊后的软化问题。方法 选择QP1180和22MnB5异种高强钢作为母材进行激光自熔焊,对焊后的激光拼焊板进行热成形试验,通过体式显微镜、扫描电子显微镜、液压拉伸试验机和维氏硬度计等手段,分析热成形前后激光拼焊板微观组织和力学性能的变化。结果 与焊态拉伸试样相比,热成形试样抗拉强度提高了135%,断后伸长率降低了55%,拉伸试样都在22MnB5母材处断裂,均为塑性断裂。在热成形后,对焊接接头进行组织分析,发现QP1180母材区马氏体含量增加,22MnB5母材区和临界热影响区组织由珠光体和铁素体转变为马氏体,焊接接头热影响区各亚区的组织均转变为大小不同的板条马氏体。硬度测试结果表明,焊态试样焊接接头的QP1180临界区存在软化现象,硬度值最低为335HV,22MnB5侧硬度值由母材处向焊缝升高,母材硬度最低为170HV;而在热成形后,QP1180临界区软化现象消失,硬度值趋于平缓,22MnB5母材处硬度比焊态试样硬度高了2倍。结论 与焊态试样相比,经热成形后激光拼焊板的焊后软化问题得到了解决。     

Tensile deformation behaviour of a dissimilar metal weldment of P91 and 347H steels

Deformation of a weldment is governed by the mechanical properties of its base metals and fusion zone. In a weldment, the base metals and fusion zone exhibit changing microstructural features with various phases present along the weldment. Specifically, the heat affected zone of a base metal exhibits a heterogeneous microstructure generated during weld thermal cycles and by post-weld heat treatment. As a result, the mechanical properties in a weldment are often non-uniformly distributed. In this study, tensile tests combined with digital image correlation were performed to obtain the non-uniform distributions of the mechanical properties of a weldment composed of P91 and 347H steels. From the experimental tensile tests, it was found that the 347H base metal had significantly distinct mechanical properties compared to the other zones of the weldment. Furthermore, the 347H base metal had the lowest yield stress but the highest strain hardening exponent. Because of its lowest yield stress, the 347H base metal had the highest plastic strain accumulation at any stage of global deformation. However, the strain hardening rate of the P91 base metal enabled it to accumulate the necessary plastic strain to activate its necking first. Therefore, the failure location of the P91-347H weldment was expected to occur at the P91 base metal. A 3D finite element simulation of the tensile deformation of P91-347H weldment also suggested the same. However, from the present experimental observations, one weldment out of three was found to fail unexpectedly at the heat affected zone of the P91 base metal. The reason for this unexpected failure was determined by microscopic analysis to be the presence of a large defect.     

不同强度级别双相不锈钢激光焊接头的组织与力学性能

目的 为了合理制定不同强度等级DP钢同种和异种接头的激光焊接工艺,研究激光焊接工艺对接头组织性能的影响。方法 采用SEM、硬度试验、拉伸试验等手段,研究不同强度等级DP钢同种和异种激光焊接接头的微观组织和力学性能。结果 对于同种DP钢激光焊接,由于接头各个区域经历的热循环不同,因此其马氏体体积分数和形态、含碳量等存在明显差异。在焊缝熔合区,由于冷却速度较高,因此马氏体体积分数较高且为细条状,硬度高于母材硬度。在热影响区,由于马氏体发生了回火分解,因此其硬度值低于母材硬度,且软化的程度和范围大小与DP钢的强度级别相关。软化的热影响区成为接头的薄弱区域,降低了接头的拉伸性能。在异种DP钢激光焊接接头中,焊缝熔合区的硬度也明显高于母材硬度。靠近高强度级别母材侧的热影响区范围更大,软化程度更明显,接头硬度分布不再对称。接头的抗拉强度与低等级DP钢母材的抗拉强度基本一致。结论 激光焊接工艺对不同强度等级DP钢同种和异种接头组织性能的影响存在较大的差异,DP钢强度级别越高,接头或接头对应侧的热影响区软化程度越明显,这在制定焊接工艺以及焊后处理工艺过程中需要予以考虑。     

汽车高强钢SG1000激光复合焊接力学性能研究

目的 针对汽车高强钢SG1000焊接接头恶化等问题,研究了SG1000激光复合焊接的力学性能。方法 选用等强匹配焊丝MG90-G对高强钢SG1000进行激光复合焊接,对焊接接头进行拉伸和低温冲击韧性试验,并结合扫描和硬度监测等手段对焊缝组织和断口形貌进行分析。结果 由于激光的预热作用,高强钢SG1000激光复合焊接成形件的焊缝美观,焊接过程稳定可靠,焊接熔池深度较大,有效改善了传统焊接的咬边、飞溅、气孔等缺陷。焊缝组织主要由板条马氏体和奥氏体晶粒组成,热影响区的过热区内部板条马氏体和奥氏体晶粒比较粗大,而焊接母材主要为细小的板条马氏体和奥氏体晶粒。焊接拉伸断口主要为细小且较浅的韧窝,且韧窝底部存在第二相粒子及夹杂物,焊接拉伸断口断裂于热影响区且微观形貌为韧性断裂;冲击微观形貌主要由准解理小平面及河流花样组成,且存在一定数量大小不一的韧窝交错分布,焊接冲击断口断裂于热影响区且微观形貌也为韧性断裂。结论 焊缝热影响区的晶粒比非热影响区的晶粒粗大,拉伸和冲击断裂均发生于热影响区;随着激光功率的增大,复合焊接接头的力学性能呈现逐渐增强的趋势;随着焊接速度的增大,复合焊接接头的力学性能呈现先增强后削弱的趋势。高强钢SG1000激光复合焊接最佳工艺参数如下:激光功率为9.5 kW,焊接速度为0.8 m/min,对应屈服强度为1 072 MPa,抗拉强度为1 175 MPa,断裂伸长率为13.5%,冲击断裂吸收的能量为30.8 J、焊缝中心显微硬度为342 HV。     

Analysis of welded tensile plates with a surface notch in the weld metal and heat affected zone

The behavior of the plates with a surface notch under tensile external loading is experimentally and numerically analyzed. The specimens were made of micro-alloyed steel NIOMOL 490 K, welded by MAG (CO₂) welding method. Surface notches were machined by the spark erosion method in the weld metal and heat affected zone. A finite element analysis of the specimens subjected to the tensile external loading is performed, with a simplified treatment of the heat affected zone mechanical properties. Obtained results are compared with the results of the experimental investigation, and a satisfactory agreement for the specimens containing the weld metal notch is observed. However, results for the specimen containing a notch in the heat affected zone require further investigation, including the analysis of the effects of micro structural heterogeneity.     

Evaluation of variation of tensile strength across 316LN stainless steel weld joint using automated ball indentation technique

Tensile strength variation across 316LN stainless steel fusion welded joint comprising of base metal, deposited weld metal and heat affected zone (HAZ) has been evaluated by Automated Ball Indentation (ABI) technique. Automated Ball Indentation tests were conducted on the various zones of the steel weld joint at 300, 523 and 923?K. The flow curves obtained from ABI results were consistent with corresponding conventional uniaxial tensile test results. The HAZ exhibited higher tensile strength than the other regions of the steel weld joint at all investigated temperatures. The ratio of ultimate tensile strength to yield stress (YS), which represents the work hardening behaviour, increased with an increase in temperature for the base metal and HAZ; whereas it remained nearly the same for the weld metal.     

Mechanical properties characterisation of welded joint of austenitic stainless steel using instrumented indentation technique

The instrumented indentation test is a promising nondestructive technique for evaluating mechanical properties of metallic materials. In this study, the localised mechanical properties of welded joint of 304 austenitic stainless steel were characterised with the instrumented indentation test. The single V-groove welded joint was produced using the electric arc welding. A series of instrumented indentation tests were carried out at different regions, including base material, weld zone and heat-affected zone (HAZ). A soft zone regarding strength properties was found in the coarse-grain HAZ. The results show that the HAZ has the lowest yield strength and tensile strength (263.6 MPa, 652.5 MPa) compared with the base material (307.4 MPa, 807.9 MPa) and the weld zone (285.6 MPa, 702.1 MPa). In addition, characterisations of microstructure, microhardness and conventional tensile tests have been performed for comparison. The results reveal that the localised mechanical properties of welded joint of austenitic stainless steel can be represented effectively with the instrumented indentation technique.     

TA2纯钛板钨极氩弧焊接接头组织与性能

本文研究了不同焊接工艺下焊缝及热影响区的微观组织特征,以分析焊接接头的力学性能。结果表明焊缝组织为锯齿状α相、板条α相及少量针状马氏体,并得到焊接最佳工艺为焊接电流85A,焊接速度0．5cm／s,主喷嘴氩气流量20L／min,拖罩氩气流量12L／min,双面焊接。此焊接工艺下得到的焊接接头抗拉强度达到母材的99．55％,延伸率达到母材的70％。文中还探讨了焊后热处理对焊接组织与性能的影响,结果表明焊后热处理可以提高焊接接头的塑性,可以调整焊接接头的综合力学性能,使其达到使用标准。