基于轮廓法测试惯性摩擦焊接头内部残余应力

采用轮廓法测试小尺寸镍基高温合金惯性摩擦焊接头的内部环向应力、中等尺寸惯性摩擦焊接头内部环向和轴向应力;分析惯性摩擦焊接头内部环向和轴向残余应力分布特征. 结果表明,轮廓法能测试小尺寸及窄小焊缝试件的内部残余应力,能反映出窄小焊缝内部的大梯度焊接残余应力全貌;惯性摩擦焊接头的环向应力沿轴向变化剧烈,沿环向分布均匀,沿厚度分布不均匀;焊缝中心位置外表层区域环向应力小于内表层区域环向应力;焊缝中心外表面轴向应力为压应力,而内表面轴向应力为拉应力,且轴向应力沿厚度呈线性变化.     

盲孔法测量高残余应力的可靠性与精确度

钻孔法测量残余应力的范围是应力不超过材料屈服极限的一半。但是在许多情况下,钻孔法是用于测量焊接残余应力,而该应力峰值往往接近材料的屈服极限。本文探讨了盲孔法测量高残余应力的可靠性与精确度。为了模拟工程应用中测量残余应力的实际过程,本文采用标定的方法,即在试验机保持一定载荷不变的条件下进行贴片与钻孔操作,测得释放应变值。试验结果表明,用测得释放应变值计算出的应力值与标定应力值吻合较好,最大绝对误差仅为21 MPa。     

基于轮廓法测试镍基高温合金惯性摩擦焊接头内部残余应力

采用轮廓法(contour method)测试小直径FGH96镍基高温合金惯性摩擦焊接接头的内部环向应力。详细介绍了轮廓法测试步骤,包括试样切割、切割面轮廓测试、数据处理和有限元分析;获得了FGH96镍基高温合金惯性摩擦焊接接头内部环向应力分布全貌并分析其分布特征。测试结果表明:镍基高温合金惯性摩擦焊接接头的焊缝中心位置环向应力为非常大的拉应力,峰值拉应力为1200 MPa,达到材料室温时的屈服强度;焊缝区域(距焊缝中心±5 mm区域)近内壁区域的环向应力大于外壁区域环向应力,垂直焊缝方向的环向应力变化梯度非常大;远离焊缝区域,焊缝两侧的环向应力不对称。     

屈服状态下盲孔法测量残余应力孔边应变释放系数修正

盲孔法测量残余应力计算公式是在弹性条件下推导出来的。为了测量材料屈服状态下的残余应力,必须对盲孔释放法进行修正,以消除孔边塑性变形对测量精度的影响。通过使用基于孔边形状改变比能S的A、B系数修正法,使盲孔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。与其它的修正方法相比,结合有限元数值计算的基于孔边形状改变比能S的A、B系数修正法简单易行,更适合于实际的工程应用。     

利用中子衍射法和轮廓法测定GH4169圆盘残余应力

分别采用中子衍射法和轮廓法对服役态GH4169合金圆盘工件内部残余应力分布特征进行表征。两种测试技术的机理完全不同，测量结果互相对比验证后，确定出较高可信度的残余应力测量结果。首先利用飞行时间中子衍射技术准确表征了GH4169合金圆盘完全热处理后轴向、径向和周向的应力，其量级约为-300~300 MPa，以周向和径向残余应力为主，沿轮廓呈“外压内拉”特征分布；利用轮廓法测量沿直径截面周向残余应力的二维分布图，切割截面周向残余应力呈现明显的“外拉内压”式分布特征的残余应力，残余应力量级约为-300~250 MPa量级。合金盘厚度中心截面上，中子衍射法与轮廓法的测试结果从趋势和绝对数值上基本一致，测试结果可信度高。     

利用中子衍射法和轮廓法测定GH4169圆盘残余应力

分别采用中子衍射法和轮廓法对服役态GH4169合金圆盘工件内部残余应力分布特征进行表征。两种测试技术的机理完全不同,测量结果互相对比验证后,确定出较高可信度的残余应力测量结果。首先利用飞行时间中子衍射技术准确表征了GH4169合金圆盘完全热处理后轴向、径向和周向的应力,其量级约为-300~300 MPa,以周向和径向残余应力为主,沿轮廓呈“外压内拉”特征分布;利用轮廓法测量沿直径截面周向残余应力的二维分布图,切割截面周向残余应力呈现明显的“外拉内压”式分布特征的残余应力,残余应力量级约为-300~250 MPa量级。合金盘厚度中心截面上,中子衍射法与轮廓法的测试结果从趋势和绝对数值上基本一致,测试结果可信度高。     

冲击压痕法测量残余应力中的塑性区问题

冲击压痕法作为近年来出现并已得到工程应用的一种新型残余应力测量技术,正在受到日益重视,已有试验结果表明,该方法的有效应用必须基于避开压痕周围的塑性区,利用压痕外的弹性区应变增量变化规律。但目前尚无定量的理论分析结果。本文采用有限单元法,通过数值分析研究了采用压痕法测定残余应力时压痕周围塑性区的变化规律,发现对于一般金属材料,当压痕直径为φ1.2mm、残余应力达到材料屈服强度时,从压痕中心算起的塑性区半径约为4mm。该塑性区尺寸为设计专用压痕法测量残余应力用应变花提供了重要依据。从而可以保证应力测量时将应变栅布置在塑性区外,避免塑性区的应变扰动导致压痕法测量残余应力时的线性规律发生偏离。     

基于本征应变法修正厚板轮廓法应力测试误差

基于本征应变法,以轮廓法测试的部分内部应力数据为基础构造出切割面上的整体纵向应力分布,修正轮廓法测试切割面上的表面应力误差,并研究了本征应变阶数对构造结果的影响.结果表明,本征应变法构造出的切割面上纵向应力分布与轮廓法测试结果符合较好,表层应力相比于轮廓法测试值提高了约27%;构造出的表面应力与XRD法测试结果符合较好,一定程度上能修正轮廓法表层纵向应力测试误差;沿切割面x方向和y方向本征应变基函数阶数采用16次和10次,能构造出较好的纵向应力场.     

盲孔法测量LiH残余应力

采用盲孔法对烧结、机加成形的SR40超半球和Φ60圆柱的LiH材料测试件进行残余应力测量。结果表明:SR40超半球测试件球面45°处残余应力值最大,径向σr达到-9.5670 MPa,周向σt达到2.2352 MPa;球面各点径向σr残余应力均为压应力,而周向σt残余应力均为拉应力,且径向σr大于周向σt,测试件呈压应力状态。Φ60圆柱测试件端面中心残余应力值最小,从端面中心到端面边缘,径向σr和周向σt残余应力是先增大后减小。     

提高小孔法测量焊接残余应力精度的研究

基于焊接残余应力的测量，介绍了常用的测量方法，重点阐述了小孔释放法的测量原理、推导了焊接残余应力的计算公式以及为提高测量精度而进行的释放系数的标定和塑性变形公式的修正，同时还分析了释放应力小孔间距、边距以及应力释放时间对测量结果的影响。     

Internal residual stress measurement on linear friction welding of titanium alloy plates with contour method

The internal residual stress within a TC17 titanium alloy joint welded by linear friction welding (LFW) was measured by the contour method, which is a relatively new and destructive technique to obtain a full map of internal residual stress. The specimen was first cut into two parts; the out-of-plane displacement contour formed by the release of the residual stress was then measured; finally, taking the measured contour of the cut plane as the boundary conditions, a linear elastic finite element analysis was carried out to calculate the corresponding distribution of residual stress normal to the cut plane. The internal stress distribution of the TC17 titanium alloy LFW joint was also analyzed. The results show that the tensile residual stress in the TC17 LFW weld is mainly present within a region about 12 mm from the weld centerline; the peak tensile residual stress occurs at the weld centerline and reaches 360 MPa (about one third of the yield strength of TC17 alloy); within the weld zone of the TC17 LFW weld, the through-thickness stress is not uniform, and the internal stress is larger than that near the top or bottom surface.     

Measurement of residual stresses in dissimilar friction stir-welded aluminium and copper plates using the contour method

The longitudinal residual stresses in the friction stir-welded plates of 5A06 aluminium and pure copper were determined using the contour method. The results revealed the presence of high tensile and compressive residual stresses on the aluminium and copper sides, respectively. The residual stresses were detected on the weld zone as well as the thermo-mechanically affected zone (TMAZ) of the aluminium plate. In contrast, the compressive residual stresses in the copper plate had a much narrower width along the weld line. Peak tensile stresses up to 240?MPa were found in the TMAZ of the aluminium plate.     

爆炸消除921A钢焊接残余应力试验

根据潜艇耐压壳焊接工艺制作了模拟焊接试板，并根据爆炸消除焊接残余应力基本原理和国内外实践经验，设计了爆炸消除模拟焊接试板残余应力的工艺，进行了爆炸消除921A钢焊接残余应力试验研究。结果表明，单、双面布药爆炸处理消除焊接残余应力，均能有效调整、消除焊接残余应力，使残余应力分布明显均匀化；接触爆炸处理效果优于非接触爆炸处理效果；爆炸冲击波的作用效果优于反射拉伸波作用；双面爆炸处理效果优于单面爆炸处理效果。     

超声波法曲面工件残余应力测量

开发了超声波法焊接残余应力测量系统.用该系统配合平直探头对曲面工件的焊接残余应力进行测量尝试.将超声波法获得的测量结果与激光全息小孔法的测量结果比较,超声波法测量所得的焊接残余拉压应力区间与小孔法相同,分布曲线较小孔法测量结果缓和,最大拉压应力均要小于曲面工件中实际拉压应力.根据试验结果,结合名义声弹性常数表达式分析了...     

Recent advances in the hole drilling method for residual stress measurement

The main activities in the hole drilling residual stress measurement technique recently developed at the University of Pisa are reviewed and presented. Particular attention was paid to developing tools for increasing the limits indicated by the presently applied standard procedures for residual stress evaluation. For residual stresses that were assumed to be uniform through-thickness, the effect of plasticity was numerically analyzed and results formed the basis for a procedure that allows an increase in the maximum measurable residual stress up to 0.9 of the material yield strength. For nonuniform through-thickness residual stress, accurate analytical influence functions are proposed by which arbitrary interpolation of the influence coefficients is avoided and all the experimentally obtained strains, with no regard to their number, can be used as input for residual stress evaluation.     

车轮残余应力测试的仿真分析

采用商用有限元软件MSC.Marc分析车轮残余应力测试试验的整个锯切试验过程,分析了锯切中每个测试点的应力、应变变化情况。通过比较仿真结果与工程试验测试结果,说明车轮锯切试验测试残余应力的可靠性。锯切的仿真分析为进一步研究车轮残余应力测试方法奠定了基础。