钻孔法测量残余应力过程中钻孔附加应变

本文叙述了钻孔法测量残余应力过程中的附加应变.研究应力水平对附加应变的影响是在单向应力条件下进行的,结果表明,钻孔条件、材料状态以及残余应力达到一定值时,附加应变为零.     

生物组织中的残余应变

本文综述了生物组织中残余应力和残余应变的研究历史和现状，着重分析了心血管系统的残余应变和零应力状态，讨论了残余应变对血管和心脏等器官的力学分析和组织改造的重要意义，并提出了一些有待研究的问题．     

钻孔偏心下的应变释放系数及残余应力

用钻孔应变释放法测残余应力的基本理论导出在任意钻孔偏心下应变释放系数[A],[B]的精确公式.揭示了各传统近似方法(丝栅中心应变法、纵向线积分平均应变法及有效面积上积分平均应变法)的应变释放系数随r_м/а的变化规律。并采用数值逼近法求解了钻孔偏心时的应变释放系数及残余应力.结果表明,偏心对残余应力影响很大。     

钻孔法测量残余应力过程中钻孔附加应变的研究（Ⅱ）

本文应用弹塑性理论研究了被测试样的屈服强度、应力场对钻孔法测量残余应力过程中钻孔附加应变的影响,使用简化的理论模型推导了低速旋转钻头钻孔产生附加应变的一般表达式.结果表明钻孔引入的附加应变与被测试样的原始残余应力状态有关,随应力水平增加而增大,在压应力减小到某一临界值σ时,钻孔附加应变为零。在 Ly12铝合金上的实验测量结果与理论结果一致。     

云纹干涉与钻孔法测量残余应力的实验方法与系统

应变片钻孔法是工程中应用最广的残余应力测量方法之一，由于应变片只能得到其长度范围内的平均应变，测量误差比较大，本文提出用云纹干涉法测量的位移信息代替应变片测量的应变信息来确定残余应力，用有限元建立位移与残余应力之间的关系，基于以上理论，开发了一种可以进行现场残余应力测量的便携式云纹干涉钻孔系统，并用该仪器进行了铝合金激光焊接接头的残余应力测量，得到了焊缝中心残余应力值。     

应用固有应变理论计测对接焊钢管残余应力场的实验研究

本文采用改进后的固有应变法对对接焊管接头残余应力计测进行了理论分析,确定了测量方案,研究果结表明对于可处理成轴对称问题的对接焊管残余应力问题只需不太多的测量值就能获得残余应力全场。本文就一个对接焊钢管试件进行了实验,实验计测结果同其它文献较为一致。它显示了应用改进后的固有应变理论决定对接焊钢管残余场的有效性。     

膨胀管残余应力测试

膨胀管残余应力是影响膨胀管抗外挤、内压强度的重要因素之一。确定膨胀管的残余应力，测试方法至关重要。在常用测试方法中，机械测量法中的盲孔法体现出测试的优越性。应用盲孔法测试J55、K55两种规格膨胀管的残余应力，并根据实际测试的应力水平和实验误差，采用应变释放系数分级法对试验结果进行修正，以提高测试结果的精度。实验结果表明，膨胀管膨胀后存在环向、轴向的残余应力，且外表面总是压残余应力。将实验结果与仿真结果对比，误差满足工程要求，说明盲孔法测试膨胀管残余应力方便、快捷、准确、有效。     

考虑塑性和刚度不匹配的焊接残余应力估算

现有残余应力计算方法未能考虑材料塑性变形和焊接接头刚度不匹配的影响,使得焊接残余应力计算结果和实际残余应力存在较大偏差.在2219-T87铝合金钨极氩弧焊焊接头残余应力测试基础上,提出一种基于非线性有限元和材料弹性模量分区的残余应力—释放应变曲线的残余应力计算方法,研究了材料塑性变形和接头刚度不匹配对焊接残余应力计算的影响.结果表明,焊接接头中非均质材料塑性不匹配可以引起对于残余应力计算的较大误差;材料塑性变形对残余应力的影响大于接头刚度不匹配对残余应力的影响.所提出方法修正了传统方法在焊接接头的残余应力计算中由于未考虑接头非均质材料塑性不匹配而引起的误差.     

应用云纹干涉法测量冷挤压孔周残余应力分布

本文就冷挤压加工后紧固孔周的残余应力测量问题进行了研究。文中提出了径向切割法以释放欲求剖面的周向残余应力;采用高灵敏度的云纹干涉法测量残余应力释放后引起的附加变形;用载波错位法获得高反差的应变条纹图。     

钻孔偏心对松弛应变和残余应力的影响

用盲孔释放法测残余应力的基本理论导出在任意钻孔偏心下应变释放系数 A、B 的精确公式.同时通过用偏心公式和不偏心公式计算得到的残余应力值的比较,说明钻孔偏心量对残余应力值影响很大.     

Analysis of relationships between residual magnetic field and residual stress

The impact of stress on changes in magnetisation is one of the most complex issues of magnetism. Magnetic methods make use of the impact of stress on permeability, hysteresis and magnetic Barkhausen noise, which are examined with fields with a high strength and a small frequency. The paper presents an analysis of the impact of residual stress resulting from inhomogeneous plastic deformations in the notch area of the examined samples on the changes in the strength of the residual magnetic field (RMF). The RMF on the surface of the component is the superposition of the simultaneous effect of the shape, the anisotropic magnetic properties of the material, as well as of the values of the components of a weak external magnetic field (most commonly—the magnetic field of the Earth). Distributions of the RMF components were measured on the surface of samples with a various degree of plastic strain. The finite element method was used to model residual stress in the samples. The impact of residual stress on changes in the residual magnetic field was shown. A qualitative correlation was found between places with residual stress and areas with increased values of the gradients of the RMF components. Further research is now in progress in order to develop the quantitative relationships.     

搅拌摩擦焊接残余应力及残余变形数值分析

建立了搅拌摩擦焊接顺序热力耦合有限元模型,用移动热源模拟搅拌头的作用,对搅拌摩擦焊接进行数值模拟.瞬态温度场及残余应力场与试验结果吻合良好,从而验证了该模型的正确性.本文研究了焊接过程中应力变化过程,指出应力场的不均匀分布引起板的弯曲变形.建立了不同尺寸有限元模型,研究板的尺寸对残余变形的影响.板的宽度对纵向残余变形曲率影响较大,长度对变形曲率影响较小.当焊接长度足够长,模型宽度相同时,不同模型远离端部区域纵向弯曲曲率相同.板的横向残余变形主要由焊缝区域变形引起,远离焊缝区域几乎没有弯曲变形发生,且板的尺寸对变形曲率影响很小.     

无损残余应力测量及其新技术

简述及比较了主要的残余应力无损测量技术，重点为磁力法，并介绍一台新的磁力仪MAPS，且对MAPS及传统磁力仪作了比较，同时以X射线及中子衍射得到的结果验证了MAPS的可靠性，也介绍了文献上较少见的火车钢轨残余应力分布图。     

Measurement of residual stress by the hole-drilling method: On the direction of maximum residual stress

A rigorous and analytical criterion for determining the direction of maximum residual stress is presented. Based on this criterion, a simple intuitive method which is independent—not only of the reference coordinate, but also of the order of gage numbers—is also presented to determine the direction of maximum residual stress.     

Experimental determination of residual stresses in paperboard

A method for the experimental determination of the through-thickness residual stress distribution in paperboard is presented. The successive removal of thin layers from strips of board through surface grinding changes the stress-state and the bending stiffness resulting in a changed curvature, which is measurable. From tests of strips in both in-plane directions, stress distributions can then be evaluated using the Treuting-Read method. Geometrically nonlinear effects at the large deformations taking place are avoided through a proper choice of strip dimensions. Typical results are presented and factors influencing the accuracy of the determination are thoroughly discussed.     

Evaluation of residual stresses in stainless-steel claddings

The residual-stress in-depth profiles have been evaluated in AISI 308L and 309L stainless-steel claddings using three different techniques: the X-ray diffraction, the neutron diffraction and the step-by-step hole-drilling method. These claddings are strongly textured and contain up to 10-percent ferritic phase. For this reason, the elastic characteristics of the material have been calculated from the single crystal compliances through a self consistent micromechanical approach. The results obtained with the three different experimental techniques are compared and discussed. The effect of a stress-relief heat treatment is also studied. Paper was presented at the 1994 SEM Spring Conference on Experimental Mechanics held in Baltimore, MD on June 9.     

Measurement of favorable residual stresses in polycarbonate

Research in this laboratory has been directed toward the production and effects of beneficial residual stresses in plastics. Such stresses have been shown to have a dramatic effect on the impact strength and fatigue life of polycarbonate samples. For example, thermal quenching, in water or liquid nitrogen, of samples heated above their glass-transition temperature, resulted in an increase in the mean fatigue life of the material by as much as 20 times over that of annealed material. This increase is attributed in large part to the introduction of compressive stresses on the surfaces of the samples. This paper concentrates on methods used to measure residual stresses in the surface of the material and on the variation of these stresses with time after treatment. Three measurement techniques are described: (1) material slicing, (2) photoelastic fringe displacement and (3) the ASTM hole-drilling method. The advantages, limitations and comparative results of these three methods are described and analyzed. Paper was presented at the 1986 SEM Spring Conference on Experimental Mechanics held in New Orleans, LA on June 8–13.     

Blind-hole residual stress determination using optical interferometry

The in-plane method and the out-of-plane method are used to analyze blind-hole residual stress as measured by optical interferometry. The in-plane method, which constructs a relation between the in-plane displacement field and the residual stress released from blind-hole drilling, is applicable when the sensitivity vector of the interferometer used in the measuring system is parallel to the object surface. Three in-plane displacements obtained from one interference pattern are sufficient to determine the residual stress. The out-of-plane method, which establishes a new relation between the out-of-plane displacement field and the released residual stress, is suggested when the sensitivity vector is perpendicular to the object surface. Two relative out-of-plane displacements extracted from one interference pattern are sufficient to determine the residual stress. With the adoption of these two methods, interpolating calculation is not needed to determine the fringe order of each data point, since the selections of the required data points are flexible using these two methods. Two experiments, one for the in-plane method and the other for the out-of-plane method, were carried out to illustrate the applicability and usefulness of these two methods.     

Hole-drilling strain-gage method of measuring residual stresses

The hole-drilling strain-gage method of measuring residual stresses in elastic materials can be termed semidestructive if holes of very small diameters are used. The method permits the magnitudes and principal directions of residual stresses at the hole location to be determined. This is accomplished by means of an emirpically determined relation between the magnitudes and directions of the principal stresses and the strain relaxation about the hole as the hole is drilled. This relation was obtained for a nondimensional model of the hole-gage assembly in order to make the results independent of hole size. A generalization was postulated to extend the use of this calibrated solution to the measurement of residual stresses in all elastic, isotropic materials.I. Vigness was HeadPaper was presented at 1966 SESA Spring Meeting held in Detroit, Mich. on May 4–6.