ST14钢激光拼焊板焊缝组织及成形性能分析

对1.5mm和0.8mm两种规格的ST14钢等厚激光拼焊板焊缝部位进行杯突试验,比较焊缝与母材杯突值;再对由这两种规格组合拼焊的不等厚激光拼焊板进行单向拉伸试验,检验拼焊板经拉伸后的断裂部位;分析焊缝区组织及其硬度变化,研究激光焊接参数变化对ST14钢拼焊板成形性能的影响.结果表明,焊缝深冲性能低于母材,焊缝杯突值受焊接速度影响,随焊接速度增加而增加;激光焊缝抗拉强度高于母材;对于1.5 mm拼焊板,提高焊接速度,加快焊缝冷却,有利于生成细小的针状铁素体,可提高激光拼焊板的成形性能;而0.8 mm板焊缝生成晶粒细小的粒状贝氏体组织,可使焊缝区材料成形性能接近母材;焊缝及其热影响区的硬度高于母材硬度.     

DC05同材同厚拼焊板焊缝组织与力学性能

焊缝对同材同厚拼焊板成形的影响远大于母材强度或厚度差异的拼焊板.焊缝的力学性能是评价同材同厚拼焊板成形性及有限元仿真的关键.文中在"混合法"的基础上,通过微观组织观测与微硬度测试,结合数字影像相关技术,获得了拼焊板单向拉伸实时的全场应变场,解析计算出了焊缝的真实应力-应变关系曲线.将此曲线与小尺寸试件单向拉伸试验曲线对比分析后发现,曲线在前期稳定变形阶段是吻合的,在屈服阶段和颈缩阶段的差异是由于标准试件中母材对焊缝变形的限制作用,阻止焊缝过早颈缩.结果表明,焊缝的应变路径(应变比为-0.63)已经偏离单向拉伸状态(应变比为-0.50),纯焊缝试件则无此限制作用.计算所得曲线才是包含母材焊缝的真实应力应变曲线.     

薄板铝合金的TIG拼焊及其单向拉伸成形性能

拼焊所具有的优点使其成为绿色再制造技术之一。本文首先针对汽车轻量化材料铝合金薄板制定焊接工艺、优化焊接参数,实施TIG拼焊,并对铝合金TIG拼焊板进行微观组织、显微硬度、单向拉伸成形性能测试及扫描电子显微镜断口形貌测试,同时分析了焊接接头组织及硬度分布规律、焊缝位置对铝合金拼焊板成形性能的影响。研究表明:焊缝组织是细小的等轴晶和树枝状晶,硬度较低;焊缝的位置不同,拼焊板的成形性能不会有明显差异;试样的断口形貌表明6061铝合金拼焊板的塑性低于母材。     

6061铝合金及其激光拼焊薄板杯突成形性能研究

主要研究了6061铝合金母材及其拼焊板在杯突试验中的成形性能以及焊缝对拼焊板成形性能产生影响的因素。试验结果显示,随着铝合金伸长率的增大,材料的显微硬度也不断增大;杯突试验的结果表明,焊缝降低了拼焊板成形性能,使其杯突值小于母材;采用DYNAFORM模拟软件进行模拟,由于焊缝尺寸很小,对模拟结果的影响十分有限,故可以忽略焊缝类型而只考虑其所在位置,结果表明:母材的变形连续且均匀,拼焊板的开裂往往发生在偏离焊缝中心的热影响区内。     

差厚高强钢激光拼焊板拉伸失稳行为研究

对0.7mm/1.0mm厚度组合的B170P1钢激光拼焊板试件进行半球凸模胀形试验,分析不同应变状态下拼焊板的变形、失稳特点及应变分布情况,研究其拉伸失稳规律。研究表明,拼焊板试件的变形失稳主要发生于薄侧母材,且随应变状态由单拉向平面等双拉的转变,应变分布趋于均匀,失稳位置向焊缝靠近;在变形过程中,靠近焊缝的薄侧母材在平行于焊缝方向的变形受到厚侧母材及焊接区的影响,其应变路径快速向平面应变漂移,达到成形极限状态,降低了拼焊板的成形性能。焊缝的存在导致差厚激光拼焊板各部分变形不均匀,在差厚激光拼焊板的实际应用中,应采取适当措施抑制薄侧母材的局部变形,增加厚侧母材塑性变形的比例,提高差厚拼焊板的冲压成形性。     

不等厚激光拼焊板杯突试验及模拟

针对厚1.8 mm的SAPH440和厚2.2 mm的DP600不等厚异质板材采用激光焊接技术实现拼焊,进一步研究SAPH440和DP600的不等厚激光拼焊板的焊接接头性能和成形性能。针对拼焊板的胀形性进行杯突试验,研究表明,当薄板SAPH440所占的比例较厚板DP600大时,拼焊板的杯突值低于任何一侧母材的杯突值,即拼焊板的胀形性低于母材。并利用Dynaform软件对拼焊板的成形过程进行仿真分析：结果表明两侧板材变形不均匀,焊缝向厚板侧移动。     

拼焊板成形性能的理论预测与实验研究（英文）

基于塑性本构关系和Hosfrod屈服准则,当拼焊板焊缝及热影响区金属的弹塑性力学性能已知时,提出一种获得拼焊板成形极限图的理论计算方法。建立获取拼焊板成形极限图的半球凸模胀形物理实验模型,并将物理实验结果与理论计算结果进行对比分析。研究结果表明:拼焊板及其母材成形极限图的理论计算结果与物理实验结果吻合较好;拼焊板的成形极限明显低于母材,说明拼焊板与母材相比,成形性能降低。该理论计算模型为快速准确获得拼焊板的成形极限图提供了一种方法。     

焊接理论

焊接接头的强度 拼焊板焊缝方向对其单向拉伸性能的影响研究／陈水生…／／材料科学与工艺．-2010,8（4）：480-485 为提高拼焊板成形性。用单拉实验来研究拼焊板焊缝方向对其拉伸性能的影响。采用解析、实验和有限元法研究了拼焊板焊缝方向对其综合延伸率、失效模式的影响。结果表明,当焊缝角度较小时,失效表现为焊缝开裂;随着焊缝角度增大,平均延伸率非线性减小,且变化速率逐渐减小。     

铝合金FSW拼焊板塑性变形规律研究

铝合金搅拌摩擦焊拼焊板焊缝各区力学性能的差异导致拼焊板成形时严重的不均匀性,降低了拼焊板的成形性能,极大地限制了铝合金拼焊板的应用。以2024铝合金搅拌摩擦焊拼焊板为研究对象,通过实验和有限元模拟系统研究接头力学性能失配对铝合金拼焊板塑性成形性能的影响规律和机理。对铝合金搅拌摩擦焊接头进行金相检验和硬度测试,根据接头组织及硬度分布特征,将搅拌摩擦焊接头划分为焊核区、热机影响区、热影响区以及母材区4个部分,以此建立搅拌摩擦焊接头的有限元模型,并对接头变形过程中的约束与协调变形规律进行分析。接头变形时拉伸应力在屈服应力最小的区域最低,在屈服应力较大的区域相应升高,且在接头中存在失配比交界处都会发生突变。从形变能的角度分析,这主要是由于力学性能失配而导致变形不协调及相互约束,表现在接头拉伸性能上就是屈服强度及屈服位置、抗拉强度、延伸率随接头各区失配比组合的差异。     

激光拼焊板焊缝仿真处理方式研究

目前常用的金属板料冲压成形软件,一般不考虑拼焊板焊缝性能的刚性连接处理方式,这在某些工况下会造成与实际成形结果的较大偏差。为兼顾效率与精度,通过对焊缝性能的分析,提出在仿真中使用壳单元,并对焊缝赋予特殊材料属性的焊缝处理方式。试验证明,此种方式在拼焊板两侧母材强度相当时,相对于传统刚性连接方式,与试验结果有高度的吻合性,体现出了良好的精度,具有工程应用价值。该研究在此处理方式的基础上仿真分析了同材、同厚拼焊板的成形过程,探讨了其成形能力相对于单一母材有较为明显下降的原因,认为,焊缝较低的塑性与延伸率,致使其在成形过程中应力高度集中、易于脆断,并影响周边母材的成形,从而制约了拼焊板整体变形潜力的发挥。     

Influence of weld geometry and mismatch on formability of aluminium tailor welded blanks: numerical and experimental analysis

Abstract

The forming behaviour of tailor welded blanks (TWBs) has been widely studied since its development. In the numerical simulation studies, the TWBs are modelled as blanks composed of two different materials, and often, the presence of the weld bead is neglected in its finite element discretisation. In the present work, the influence of the weld bead shape on the formability of friction stir welded TWBs, is analysed. Several finite element meshes were constructed in order to represent different weld bead geometries and numerical simulations of the cylindrical cup drawing were performed. Strong influence of the weld bead shape on the formability of the TWBs was observed when the weld was in overmatch relatively to the base material, and little influence when the weld was in undermatch condition. Comparison of the numerical results with experimental ones shows that the numerical analysis is able to preview the formability of the TWBs.     

拼焊板盒形件冲压成形失效及应变路径分析

采用自制液压机和分瓣压边圈模具,通过模拟仿真和实冲试验,变化各工艺参数,研究分析拼焊板方盒件冲压成形的应变路径、焊缝移动和成形极限,以提高其成形性能。研究表明,厚/薄侧压边力的大小和分布对破裂危险点的应变路径和成形裕度有很大的影响,合理的压边力分布可调节失效破裂的位置,减少焊缝移动和提高成形极限深度;凹模圆角半径的增大,对薄侧侧壁圆角处破裂危险点应变路径影响较大,拼焊板盒形件成形极限深度逐渐增大;厚度比较小时,破裂出现在薄侧圆角处,而厚度比较大时,焊缝移动量大,破裂易出现在薄侧焊缝处;板料毛坯形状和尺寸对失效破裂的位置和成形性能影响显著。因此,以薄侧侧壁圆角处和薄侧焊缝位置附近为破裂危险点,通过优化压边力、凹模圆角半径、板料厚度比、板料毛坯形状和尺寸等工艺参数,改变危险点的应变路径,调节失效破裂的位置,减小其焊缝移动量,可有效地提高拼焊板方盒件的冲压成形性能。     

不等厚拼焊板材的成形性实验研究

不等厚拼焊板由于焊缝的存在及其方位影响，又由于坯料强弱不均，可以引起坯料的冲压变形性能发生显著变化。本文通过焊接工艺对比，比较了激光焊、滚压电阻焊和氩弧焊工艺对拼焊板塑性变形性能的影响；对拼焊板试析进行拉伸实验，确定了焊缝方位和薄厚板比例对试件塑性变形的影响；进行了不等厚拼焊板件的半球拉深实验和方盒件拉深实验，总结了拼焊板材的冲压成形性能和不均匀变形规律。     

On formability of tailor laser welded blanks of DP/TRIP steel sheets

Abstract

This paper aims to evaluate the formability of tailor welded blanks of dual phase (DP600)/transformation induced plasticity (TRIP700) steel sheets. In this work, bead on plate butt joints of 2·5 mm DP600 and 1·2 mm TRIP700 steel sheets were performed using CO₂ laser beam welding. Microhardness measurements and transverse tensile testing were carried out to characterise the welds. The formability of base metals and welds were investigated by standard Erichsen test. In a perpendicular tensile test to the weld line, all specimens were fractured at the TRIP base metal, and the strengths were somewhat higher than those of base metal. There was a significant reduction in formability caused by welding of the DP600/TRIP700 steel sheets, and the formability increased with increasing welding speed.     

基于DIC的拼焊板焊缝性能识别方法及验证

提出一种新的拼焊板焊缝参数识别方法——分区法.根据垂直焊缝方向次应变不同,将焊缝区分为焊缝和热影响区.采用数字图像相干技术,获取焊缝失效时拼焊板表面的应变场.建立了焊缝性能参数计算模型,分别计算出焊缝的强度系数和应变硬化指数.为验证分区法的有效性,针对纵向激光拼焊板单向拉伸试验,将理论计算结果嵌入有限元分析中,获得拉伸载荷-位移曲线,与混合法及试验结果比较.结果表明,分区法比较接近试验结果,具有较高的精度.     

Finite element analysis of effects of soft zones on formability of laser welded advanced high strength steels

Abstract

Applications of advanced high strength steels in tailor welded blanks are a major focus to reduce vehicle weight and manufacturing cost, and to improve part performance. In the present work, formability of two types of laser welded steels in biaxial stretch forming has been studied. Laser welded blanks of the dual phase steel showed larger reduction of formability than those of high strength low alloy steel. This was due to formation of soft zones in the outer heat affected zone of dual phase steel where strain localisation and fracture occurred. Finite element simulations of dome testing incorporating local weld zone properties were able to accurately predict experimentally observed behaviour including deformation patterns and failure locations. In particular, the simulations have shown that under matching of the softened heat affected zone leads to reduced formability by localisation of strain; and that the fracture location changes from radial to circumferential plane when the flow curve of soft zone is evenly matched with the base metal. It was also concluded that the width of the soft zone has minor influence on formability during biaxial stretch forming.     

拼焊板单向拉伸变形非均匀性

从金属塑性理论出发,结合拼焊板成形特点,推导出同材差厚拼焊板试件单向拉伸情况下缩颈时焊缝两侧薄厚板变形量公式。并基于垂直于拉伸方向居中焊缝的拼焊板单向拉伸实验,将实验结果与公式推导结果比较,初步验证了公式的合理性。进而进行了不同焊缝位置(焊缝垂直于拉伸方向,薄厚板厚度比例不同)情况下的拼焊板试件单向拉伸有限元模拟,进一步验证了所推导公式是正确的。另外,分析了单向拉伸状态下焊缝两侧薄厚板变形的非均匀特性,利用文章所提出的公式,可以定量地预测单向拉伸状态下拼焊板试件焊缝两侧材料非均匀性变形量,从而为提高焊缝两侧材料的匹配性以减小拼焊板变形的非均匀性提供了参考依据。     

Formability Enhancement of Galvanized IF-Steel TWB by Modification of Forming Parameters

Tailor-welded blanks (TWBs) have numerous advantages over traditional blanks used in manufacturing, such as energy conservation and environment protection. Low formability and weld line movement during forming operation are main limitations of these blanks. In this research, the effects of forming parameters including thickness ratio (TR), rolling direction with respect to the weld line and direction of major stress with respect to the weld line, on formability and weld line movement of TWBs made of galvanized Interstitial-Free (IF) steel were investigated experimentally. Also the effect of application of non-uniform blankholder force on weld line movement was studied by FEM simulation. By utilization of ABAQUS software, blankholders with different geometries, namely one-piece and two-pieces were modeled and forming process was simulated. The results revealed that formability maximized when the major stress and rolling direction were along the weld line. The results showed applying different blankholder forces, by application of the two-pieces blankholder, leads to more uniform strain distribution and correspondingly less weld line movement in TWBs with TR greater than 1. It was also concluded that the effect of geometric discontinuities on reducing formability was greater than the effect of the weld region.