铜及铜合金板带材分条变形测量方法探讨

针对铜及铜合金板带材经加工和分切后会不同程度地产生残余应力，引起加工制品的形状及尺寸变化，而测量板带材残余应力的方法如X-ray法和钻孔法等，因有各自的局限性而难以在普通企业实现，介绍了SEMI和JBMA推荐的分条变形测量方法，并对刻蚀程序、测量过程以及存在的有关问题进行了研究，给出一组实测数据。     

基于全场位移测量的鼓膜法表征铝箔力学性能

铝箔的力学性能通常是采用拉伸法来测量,且测量其弹性模量和残余应力的报道也很少见。本文通过利用鼓膜法结合数字散斑相关法(DSCM)对铝箔变形进行了高精度的全场位移测量,根据测得的薄膜压力与中心挠度关系再结合方形膜鼓膜理论模型,测量了厚度为6μm的铝箔的弹性模量和残余应力。实验测得的铝箔的平均弹性模量为65GPa,由粘接过程中引入的残余应力在12~50MPa之间变化。最后根据实验结果对鼓膜实验进行有限元反分析,结果表明,实验结果与有限元模拟结果基本一致。     

钛合金平板电子束焊接残余应力的小孔法测量

采用小孔法对TC11平板真空电子束焊接接头的残余应力进行了测量,结果发现,其残余应力为以纵向残余应力为主的单向拉伸应力状态,横向残余应力数值较小,同时还将测量结果与有限元结果进行对比分析,证明了有限元模型的合理性和可靠性。     

钢丝绳成形力学行为的非线性有限元分析

钢丝绳捻制成形过程属于三维梁大转动弹塑性变形问题。钢丝绳的加工应力不仅影响成形性，而且由其引起的残余应力对钢丝绳结构强度有很大影响。为保证钢丝绳成形模拟计算精度和效率，从而为钢丝绳成形工艺与结构强度的合理设计提供依据，本研究建立了考虑大转动几何非线性和材料非线性的共转坐标系弹塑性有限元计算基本方程，在此基础上编制了钢丝绳成形过程模拟计算程序。通过数值模拟计算分析钢丝绳捻制成形过程的反扭转系数对加工应力应变分布和残余应力的影响，计算结果表明：反扭转系数对捻制成形过程中应力应变和残余应力及形状冻结性有显著影响，合理的反扭转系数应取略大于1.0的值。实验结果证实了本文提出的捻线成形过程数值模拟几何模型和有限元计算模型的有效性。     

半刚接钢框架内填RC 墙结构简化分析模型

该文提出了一种用于分析半刚接钢框架内填RC 墙结构(简称PSRCW)滞回性能的简化分析模型(即斜向板带模型),基于混凝土应力-应变关系给出了斜向板带的轴力-位移关系曲线,采用Pivot 塑性滞回模型模拟斜向板带的力学行为。采用有限元方法分析了板带恢复力模型、板带数量及倾角对PSRCW 结构斜向板带模型的影响,结果表明Pivot 塑性滞回模型可较好地模拟斜向板带的滞回性能,可采用7 条以上板带及40°~50°之间板带倾角描述PSRCW 结构的整体性能。应用该简化模型对有关试件进行了滞回性能模拟,并与试验结果比较,两者吻合良好。     

基于热-力耦合模型的纤维丝束带铺放残余应力的模拟及实验研究

采用有限元分析计算和实验测试2种方法,在热-力耦合载荷作用下,对纤维丝束带铺放成型时的残余应力进行了研究。首先,建立纤维丝束带铺放的热-力耦合模型,利用有限元分析研究了不同温度和压力参数条件下纤维丝束带铺放残余应力的模拟结果。其次,对结果进行分析比较得到各个因素对纤维丝束带铺放残余应力的基本影响规律;最后进行不同温度和压力等铺放参数对纤维丝束带铺放成型时残余应力影响的实验测试研究,以验证热-力耦合有限元模型计算结果的正确性。结果表明:2种方法得到的残余应力分布基本一致,只是残余应力的最大值之间存在着差别。      

等离子喷涂热障涂层残余应力的实验与模拟研究

分别采用真空和大气等离子体喷涂工艺在GH3128镍基高温合金基材表面制备CoNiCrAlY结合层和氧化钇部分稳定的氧化锆陶瓷层组成热障涂层。采用有限元模拟计算了涂层的残余应力, 研究了基材预热对打底层与陶瓷层界面应力分布的影响规律。结果表明, 预热基材可以显著地降低陶瓷顶层内部产生的残余拉应力。采用钻孔法测量了涂层中的残余应力并与模拟结果作定量比较, 结果表明: 有限元模拟计算结果与实验测量结果能较好吻合。     

基于ANSYS的焊接残余应力的有限元分析

焊接残余应力的降低了焊接件的刚度和稳定性,采用有限元分析软件ANSYS的热一结构耦合和单元生死分析功能对钢板焊接过程进行模拟仿真,分析焊接残余应力分布的规律,为复杂焊接结构的温度分析和应力分析提供一定的依据。     

考虑冲压残余应力和厚度变化的车身结构模态分析与优化

车身零件冲压成形过程中产生的残余应力和厚度变化对其结构模态和固有频率具有重要的影响,而目前常用的有限元模态分析方法中,常常忽略了成形因素所带来的影响,导致分析结果与实际情况不相符。采用有限元网格映射算法,在车身结构模态分析中引入成形信息,并将成形残余应力作为预应力施加,研究成形因素对车身结构模态和固有频率的影响。研究结果表明,考虑成形比未考虑成形影响的模态分析结果更接近实验结果。最后,进行了基于成形因素的车身结构灵敏度分析与优化。     

钻环法测量水泥路面表面残余应力的初步研究

水泥混凝土在强度形成过程中,温度、湿度变化以及水化反应等因素将引起水泥砂浆体积变化,当体积变化受到约束时,水泥混凝土内将产生残余应力,导致水泥混凝土内部出现微裂缝。国内外进行了大量收缩变形等因素引起的水泥混凝土内部应力变化的研究,但尚需要验证。该文将从"反"方向对水泥混凝土内的残余应力进行研究,即如何测量得到水泥混凝土表面的残余应力。根据金属工程中应用较为广泛的钻孔法测量表面残余应力技术,考虑水泥混凝土主要由水泥石和石料组成,尺寸差别较大,提出利用钻环法对水泥混凝土表面残余应力进行测量的可行性。2007年美国联邦航空管理局(FAA)的机场道面实验室,进行了钻环法测量水泥混凝土表面残余应力的初步试验,该文将建立有限元模型,对存在初始应力的板进行钻环模拟,通过与封闭解的对比,验证有限元模型的准确性,通过与FAA的试验结果进行对比分析,验证了钻环法测量水泥混凝土表面残余应力的可行性。     

钻环测量水泥混凝土板表面残余应力的试验研究

水泥混凝土在强度形成过程中,水泥砂浆体积变形受到约束后将导致水泥混凝土内产生残余应力。对水泥混凝土路面板而言,板表层水泥砂浆的体积变形受外部环境影响更严重,因此板表面存在较大的残余应力,超过其抗弯拉强度时将导致微观裂缝的出现。目前,根据金属工程中测量表面残余应力的钻孔法,相关学者提出了钻环测量水泥混凝土表面残余应力的方法,并对其可行性进行了分析。该文将在该方法可行性分析的基础上,建立有限元模型对钻环过程进行模拟,确定室内试验时钻环法的相关技术参数,然后浇注水泥混凝土板,考虑加载和不加载两种工况进行室内试验,试验结果表明:钻环能够释放板表面的残余应力,该方法可以用于水泥混凝土表面残余应力测量。     

冲击压痕法在残余应力测定中的应用

通过在工件表面采用冲击加载的方法形成一定尺寸的球冠形压痕造成外加应力场,根据外加应力场和工件的残余应力场叠加引起的应变增量计算残余应力,此方法基本上不损伤被测工件,有一定的工程实用性。适合硬度在50HRC以下的焊接件焊缝且有无损要求的工件的残余应力的测定。     

Evaluation of Residual Stress in Flip Chip Using 3-D Optical Interferometry/FEM Hybrid Technique

Abstract:  The residual stress in flip chips was investigated by a hybrid technique of 3-D finite element method (FEM) and 3-D optical interferometry. The residual stress consists of two parts: the chemical shrinkage stress caused by underfill curing and the thermal stress caused by coefficient of thermal expansion (CTE) mismatch and cooling. Warpage and in-plane deformation of the flip chip during the underfill curing and cooling procedure was real-time characterised with an integrated 3-D optical interferometry system. The measurement results were used to evaluate the chemical shrinkage stress and to verify/modify the FEM model for the analysis of thermal stress. It was found that the chemical shrinkage stress under isothermal curing condition is very small in average and negligible. As the difference between the simulated and measured thermal deformation falls within a limited scope, the accuracy of the simulated thermal stress can be guaranteed.     

Measuring residual stress and the resulting stress intensity factor in compact tension specimens

The measurement of residual stress through the remaining ligament of a compact tension specimen was studied. In the crack compliance method, a slot or notch is successively extended through the part, and the resulting strain is measured at an appropriate location. By using a finite element simulation of a specimen preloaded beyond yield, three techniques for determining the original residual stress from the measured strains were compared for accuracy and sensitivity to measurement errors. A common beam-bending approximation was substantially inaccurate. The series expansion method proved to be very versatile and accurate. The fracture mechanics approach could determine the stress intensity factor caused by the residual stresses with a very simple calculation. This approach offers the exciting possibility of determining the stress intensity factor prior to a fatigue or fracture test by measuring strains during the specimen preparation.     

基于比容测量对材料三维残余应力及其分布的测试分析

目的 判断比容差法是否可应用于材料内部残余应力分布状态的定量研究,旨在提供一种新的残余应力的测试方法。方法 通过对材料非切应变时的弹性力学进行讨论,推导体积应变,得出残余应力的计算公式。应用比容差法对一种工业纯铝的残余应力状态进行定量测量与表征,并进行钻孔法的定量验证。在此基础上,应用比容差法对纯铝镦粗变形后的三维平均残余应力的分布进行了测量研究。结果 比容差法对纯铝镦粗变形后的体积变化测量,可精确、定量表征材料的残余应力状态,与钻孔法实验结果相比,两者的误差在20%以内;镦粗变形后,残余压应力在坯料中心处取得最大值,且对称于中心沿高度方向逐渐减小,呈对称递减分布。结论 比容差法可用于材料三维残余应力分布的研究,为残余应力分布规律,提供了一种新的有效且精确的测试方法,具有实际应用的价值。     

平整加工对高强钢抗畸变能力的影响及优化

为解决高强带钢在生产加工过程中产生的板形缺陷和畸变,本文采用裂纹柔度法测量单下辊传动平整加工前后620JJ带钢内部残余应力,并依据残余应力在厚度或板宽方向分布不均将导致带钢发生畸变,定义带钢应力不平衡度为畸变评价指标,分析了平整工艺对带钢内部残余应力分布和畸变的影响,并利用ABAQUS有限元模拟探究了工艺优化方案。结果表明:裂纹柔度法能够准确表征带钢内部残余应力;应力不平衡度可以直观地表征带钢产生畸变的可能性;平整加工对带钢的主要影响是应力的均衡化和降低整体残余应力水平,平整前后各测点弹性应变能极值与平均值差值从169.25 MPa·mm降至141.86 MPa·mm,带钢内部残余应力的最大值由463.26 MPa降至363.6 MPa;将平整工艺改为双辊传动、增加摩擦力、增加张力、增加轧制力等方式均可有效改善应力不平衡度。     

Using FEM to determine the thermo-mechanical stress in tube to tube–sheet joint for the SCC failure analysis

The stress corrosion cracking in a weld of the tube to tube–sheet region of heat exchangers is a common problem. Thermo-mechanical stress in tube to tube–sheet joints including welding effect should be determined in this situation for failure analysis. In this paper, the Finite Element Method (FEM) is used to predict the thermo-mechanical stresses including welding residual stress in a tube to tube–sheet weld. Both the thermo-mechanical stress distribution with and without the welding residual stress have also been investigated by numerical simulation. The welding, operating temperature, and operating pressure have effect on total stresses. Especially, the welding residual stresses play an important role in total stress state in tube to tube–sheet joints. Geometric discontinuities of the vicinity of gap cause the welding joint to experience a local stress concentration. A high tensile stress in the tube to tube–sheet region has been demonstrated by FEM, which is the stress aspect for the SCC phenomenon of austenitic stainless steel in chloride environment.     

The three-prong method: a novel assessment of residual stress in laser powder bed fusion

ABSTRACT

Residual stress is a major problem for most metal-based laser powder bed fusion (L-PBF) components. Residual stress can be reduced by appropriate build planning and post-process heat treatments; however, it is not always avoidable and can lead to build failures due to distortion and cracking. Accurate measurement of residual stress levels can be difficult due to high equipment set-up costs and long processing times. This paper introduces a simple but novel method of measuring residual stresses via a three-pronged cantilever component, the three-prong method (TPM). The method allows for a quick and easy characterisation of residual stress for a wide range of machine parameters, build strategies and materials. Many different cantilever designs have been used to indicate residual stress within additive manufacturing techniques. All of which share the same shortcoming that they indicate stress in one direction. If the principal component of stress is not aligned with the beam geometry, it will underestimate peak stress values. A novel three-prong design is proposed which covers two dimensions by utilising three adjoined cantilever beams, a configuration which echoes that of hole-drilling where three measurements are used to calculate the stress field around a drilled hole. Each arm of the component resembles a curved bridge-like structure; one end of each bridge is cut away from the base plate leaving the centre intact. Deformation of the beams is then measured using a co-ordinate measurement machine. Stress profiles are then estimated using finite element analysis by meshing the deflected structure and forcing it back to its original shape. In this paper, the new TPM is used to compare the residual stress levels of components built in Ti–6Al–4V with different hatch patterns, powers and exposure times.     

Disposable electrochemical immunosensor diagnosis device based on nanoparticle probe and immunochromatographic strip

We describe a disposable electrochemical immunosensor diagnosis device that integrates the immunochromatographic strip technique with an electrochemical immunoassay and exploits quantum dot (QD, CdS@ZnS) as labels for amplifying signal output. The device takes advantage of the speed and low cost of the conventional immunochromatographic strip test and the high sensitivity of the nanoparticle-based electrochemical immunoassay. A sandwich immunoreaction was performed on the immunochromatographic strip, and the captured QD labels in the test zone were determined by highly sensitive stripping voltammetric measurement of the dissolved metallic component (cadmium) with a disposable screen-printed electrode, which is embedded underneath the membrane on the test zone. The new device coupled with a portable electrochemical analyzer shows great promise for in-field and point-of-care quantitative testing of disease-related protein biomarkers. The parameters (e.g., voltammetric measurement of QD labels, antibody immobilization, the loading amount of QD-antibody, and the immunoreaction time) that govern the sensitivity and reproducibility of the device were optimized with IgG model analyte. The voltammetric response of the optimized device is highly linear over the range of 0.1-10 ng mL(-1) IgG, and the limit of detection is estimated to be 30 pg mL(-1) in association with a 7-min immunoreaction time. The detection limit was improved to 10 pg mL(-1) using a 20-min immunoreaction time. The device has been successfully applied for the detection of prostate-specific antigen (PSA) in human serum sample with a detection limit of 20 pg mL(-1). The results were validated by using the commercial PSA enzyme-linked immunosorbent assay kit and showed high consistency. The new disposable electrochemical diagnosis device thus provides a rapid, clinically accurate, and quantitative tool for protein biomarker detection.     

铍环形焊件残余应力的有限元分析与测试

采用有限无限元分析法和Ｘ射线应力测试法对铍环形焊件的残余应力分布规律进行了研究。对有限元计算值采用一定加权平均处理后与Ｘ射线实测值进行了对比，结果表明，两者基本吻合，所反映出的应力变化趋势基本一致。