轧制铝合金的X-射线法残余应力测试

在轧制铝合金的X射线残余应力测试中,由于存在择优取向,在不同Ψ角位置参与衍射的晶面数目不同,造成不同Ψ角位置的衍射强度出现差异,影响衍射峰的θ-2θ位置的判断,进而2θ-sin2Ψ和I_p-sin2Ψ出现不同程度的震荡,造成测试结果准确度下降.文中采用“多晶面衍射法”从衍射峰形和强度分布出发,分析了轧制铝合金测试过程中不同衍射晶面随Ψ角位置衍射强度的变化,然后选择合适的峰形进行拟合.结果表明,采用“多晶面法衍射”可以保证衍射峰型和强度比,进而得到的测试结果和理论值吻合度较好,满足对轧制铝合金测试结果的要求.     

钛及钛合金X射线应力测试参数的选择

针对钛及钛合金X射线应力测试中衍射峰强度低、峰形差、测试结果波动范围大和准确度低等问题,通过对标准零应力试样和标准应力试样的X射线应力测试,研究了钛及钛合金X射线应力测试中准直器直径、计数时间和计数次数变化对衍射峰强度、净峰强度、半高宽、应力测试结果的影响规律,在此基础上确定了钛及钛合金X射线应力测试参数的选择方法,并对钛合金电子束焊接头的残余应力进行了测试.结果表明,随着准直器直径增大和计数时间增长,衍射峰强度增大,衍射峰形改善,测试结果准确性提高;随着计数次数增加,衍射峰形改善,测试结果准确性提高;所确定的测试参数对钛合金电子束焊接头残余应力测试的结果满足相关标准要求.     

High-precision determination of residual stress of polycrystalline coatings using optimised XRD-sinψ technique

The aim of the research is to optimise the XRD-sin²ψ technique in order to perform high precision measurement of surface residual stress. Residual stresses existing in most hard coatings have significant influence on the adhesion, mechanical properties and tribological performance. In the XRD-sin²ψ stress measurement, the residual stress value is determined through a linear regression between two parameters derived from experimentally measured diffraction angle (2θ). Thus, the precision coefficient (R²) of the linear regression reflects the accuracy of the stress measurement, which depends strongly on how precise the 2θ values are measured out of a group of very broad diffraction peaks. In this research, XRD experiments were conducted on a number of samples, including an electron beam evaporated ZrO₂ based thermal barrier coating, several magnetron sputtered transition metal nitride coatings, and shot-peened superalloy components. In each case, the diffraction peak position was determined using different methods, namely, the maximum intensity (I_max) method, the middle point of half maximum (MPHM) intensity method, the gravity centre method, and the parabolic approaching method. The results reveal that the R² values varied between 0.25 and 0.99, depending on both the tested materials and the method of the 2θ value determination. The parabolic approaching method showed the best linear regression with R² = 0.93 ± 0.07, leading to high precision of the determined residual stress value in all cases; both the MPHM (R² = 0.86 ± 0.16) and gravity centre (R² = 0.91 ± 0.11) methods also gave good results in most cases; and the I_max method (R² = 0.71 ± 0.27) exhibited substantial uncertainty depending on the nature of individual XRD scans.     

压痕应变法测量焊缝应力时的近似修正方法

压痕应变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.目前通过应变增量计算残余应力的方法仍然是通过事先试验标定,测量超强或低强匹配焊缝中的残余应力时采用的仍然是母材的标定系数,因而会带来严重误差.首先对压痕周围物理变形场进行了相应分析,继而提出一种计算焊缝残余应力的近似修正方法,从而使焊缝应力的测量精度大大提高.     

轮廓法测量残余应力研究进展

轮廓法是一种基于截面解剖法的残余应力测量方法,可以获得目标平面法向的残余应力二维分布云图。经过20多年的发展与完善,轮廓法已经被广泛应用在航空航天、核电、高端装备制造等许多重要领域,尤其适用于焊接件、金属连接件和异型工件的残余应力测量。文中详细介绍了轮廓法测量的优势,分析了轮廓法测量的理论依据、测量步骤、误差修正、拓展应用、试验验证及研究热点,深入探究在一次切割轮廓法测量基础上发展起来的多次切割轮廓法、断裂轮廓法和X射线衍射法的叠加测量、近表面残余应力轮廓法测量等方法,这些方法克服了常规轮廓法测量断面应力、近表面应力方面的技术限制,可获得工程结构件的三维残余应力分布,针对不同的工程应用需求调整切割方法及测量方案以提供技术支持,拓展了轮廓法测量的应用范围。该文旨在为国内的同行提供参考,助力轮廓法在国内科学研究和工程应用方面的推广应用。 创新点： (1)对比常用的工程残余应力测量方法,明晰轮廓法测量的技术优势及其适用范围。(2)分析轮廓法测量过程中可能引入的试验误差,提出相对应的解决方法。(3)拓展轮廓法的应用范围以满足三维应力测量需求。     

CVD掺硅金刚石残余应力的X射线衍射和拉曼光谱分析(英文)

采用X射线衍射(XRD)和拉曼光谱2种方法测量了不同硅碳比的CVD掺硅金刚石薄膜的残余应力。采用偏压增强热丝化学气相沉积装置在硬质合金基底上制备了掺硅金刚石薄膜,将正硅酸乙酯以不同的体积比溶解在丙酮中以使得反应气体中的硅碳比从0.1%变化到1.4%,从而控制掺硅金刚石薄膜的掺杂浓度。SEM和XRD的表征结果显示,随着硅掺杂浓度的增加,金刚石薄膜的晶粒尺寸减小,而金刚石(110)的晶面则逐渐占优。XRD法是测量入射角从0°到45°变化时对应的金刚石(220)面XRD衍射峰,并采用sin2ψ方法计算掺硅金刚石薄膜的残余应力。拉曼谱法则是通过检测金刚石特征峰偏移1332cm1位置的偏移量来测量残余应力。2种方法测得的残余应力随着硅掺杂含量的升高显示出良好的一致性,所有的硅掺杂金刚石的残余应力均为压应力,Si/C摩尔比为0.1%的薄膜具有最高的残余应力,为~1.75GPa(拉曼谱法)或~2.3GPa(XRD法)。随着硅掺杂浓度的进一步升高,薄膜的残余应力则稳定在~1.3GPa左右。     

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。     

利用半高宽分析铝合金X射线法应力测试工艺

文中采用X射线法测试6061-T6铝合金焊接接头残余应力，为探究合理的应力测试工艺方案，对预置应力的等强梁进行X射线应力测试，测试过程中先后增加准直器直径和摇摆角，以衍射曲线半高宽表征衍射晶粒群微观应变，研究在准直器直径和摇摆角增加时衍射晶粒群微观应变均匀性的变化，对材料进行取向成像分析，并对比在晶粒择优取向强弱不同的两个区间内应力测试的结果. 结果表明，应力测试精度与晶粒择优取向的强弱相关，在晶粒择优取向较强的空间范围内，采用大于1°的摇摆角时，小角度晶界附近的相邻亚晶都能够参与衍射，从而使衍射晶粒群微观应变趋于均匀，因此X射线应力测试精度较高，在d = 2 ~ 4 mm范围内，增加准直器直径d可增加衍射晶粒数目，但对衍射晶粒群微观应变均匀性及应力测试精度的影响不大.     

聚晶金刚石复合片(PDC)残余应力的检测方法

本文介绍了三种近期国外检测PDC残余应力的方法：应变片测试法、中子衍射法和带高能同步加速器X射线衍射法。三种方法均能有效检测出PDC的残余应力且各有其特点。应变片测试法比较直观、简单，不过这种方法是破坏性的，而且在材料去除过程中容易引入误差；中子衍射具有较深穿透力，然而较弱的散射使其取样体积不能小于1mm^3；高能同步加速器产生的散射X射线能穿透直径19mm的PDC样品，空间分辨率高，测量体积可精确至0．014mm^3，能详细地呈现出金刚石层、D／WC界面以及WC基体外径部分的二维应变分布情况，但测试易受Co峰的干扰。     

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。     

Assessment of residual stress of welded structural steel plates with or without post weld rolling using the contour method and neutron diffraction

The post-welding rolling technique was used to modify the welding residual stress profile of butt joints of S355 structural steel. Two different residual stress measurement techniques were used: contour method and neutron diffraction. A good agreement between the results of both measurement techniques was found, illustrating the capability of the contour method to provide data otherwise available only using costly neutron and synchrotron radiation. The effect of post-weld roller tensioning on residual stress consisted in a substantial change in residual stress profile, with the large tensile stresses along the weld seam becoming compressive     

残余应力测量研究现状综述

针对残余应力测量的重要性,对其测量方法进行综述和展望。阐述传统的残余应力测量方法的原理及应用情况,包括传统机械释放法和非破坏性无损伤测量法;主要介绍几种新型的残余应力测量方法及其原理;并指出残余应力的测量技术正朝着无损、在线测量、绿色等方向发展。     

TC18超高强度钛合金喷丸残余压应力场的研究

采用X射线衍射及相应交相关定峰法，通过电解抛光逐层测定了TC18超高强度钛合金喷丸的残余压应力，并分析了残余压应力场的特征及规律，同时研究了在交变应力和温度下残余压应力的松弛，结果表明，残余压应力场中的最大值为材料的本征参数，它与喷丸强化工艺无关，这对超高强度钛合金喷丸工艺的制定和应用具有重要意义。     

利用公用背底法提高X射线应力分析效率

为了提高X射线应力分析的效率，提出了公用背底法对衍射线进行背底扣除。并利用模拟衍射线考察了对于不同峰形的衍射线、公用背底法对残余应力值的影响以及合理的背底取值范围。结果表明，对于峰背比较大的衍射线，公用背底法扣除背底对应力值没有影响，可用来进行应力测定；而对于峰背比较小的衍射线，不适合采用公用背底法扣除背底。利用公用背底法进行应力测定，可以大幅度缩减扫描范围，提高测定效率。     

CALCULATION OF RESIDUAL STRESS FIELD IN LASER TRANSFORMATION HARDENED MoCu NODULAR IRON

1.IntroductionInthepasttwodecades,highpowerCOZandNd:YAGlasershavebeenusedinthefieldofsurfaceengineering,suchassurfacetransformationhardening,surfacealloyingandsurfaCecladding.Despitetheadvantageoflasertreatment(improvedwearandcorrosionresistance,smallcellsize,homogenousdistributionofimpurities,contactlessinteractionetc.)thereexistsalsoadisadvantage,i.e.thereishighresidualstressstate,bothintensionandcompression,inlasertreated..t..i.l.[1--5].Compressresidualstressishelptoincreasethefatiguelif…     

单晶结构残余应力的X射线衍射分析技术

准确测定单晶材料残余应力是控制和调整单晶构件中残余应力的前提。基于弹性力学对单晶材料弹性模量与对应衍射晶面的关系进行理论分析,建立立方单晶材料的残余应力分析模型,并提出具体试验方法,以DD3单晶叶片为例,进行试验验证。结果表明：不同衍射晶面的弹性模量受独立弹性柔度系数、取向系数影响,DD3单晶叶片表面应力模型计算值与实测值间相对误差在20 MPa范围内。这种X射线衍射残余应力测定方法测定的残余应力值可靠性较高,为工程应用中测定立方单晶残余应力提供了理论依据和试验基础。     

Evaluation of residual stress development in FRP-metal hybrids using fiber Bragg grating sensors

This paper presents experimental measurement methods for the determination and evaluation of process related thermal residual stresses in fiber metal laminates. A cure monitoring system with fiber Bragg grating (FBG) sensors is used to measure the in-plane strains during processing of carbon fiber reinforced plastic (CFRP)-steel laminates. The simultaneous measurement captures the thermal expansion during the heating stages, the cure shrinkage, and the cooling thermal shrinkage. The results enable the characterization of the co-cure bonding process and the stress transfer between the metal and FRP-layers during the creation process. The residual strains, which are used for calculation of the residual stresses, are recorded at room temperature after manufacturing. In addition, an advanced method using FBG-sensors and the deflection of asymmetric hybrid specimens is developed to validate the gained residual stress data. Asymmetrical specimens are created by removing selected layers after cure. Quantitative evaluation is achieved by determination of their curvature and measuring the strain changes with the embedded FBG-sensors. For validation, the methods were successfully demonstrated on two different curing cycles with different resulting residual stress levels. The simultaneous strain measurement enables the investigation of stress development and delivers more in-depth process knowledge for further optimization of the manufacturing process.     

基于温度函数法的铝合金电弧增材制造残余应力与变形数值模拟

电弧增材制造是制造大型复杂铝合金部件的新方法,但残余应力和变形对制造件的性能有重要影响. 建立了铝合金电弧增材制造件残余应力和变形的顺序热-力耦合有限元模型,采用移动热源法计算了增材过程的温度场,根据峰值温度的分布和演变特征确定了温度函数的提取方案,并分别采用移动热源法和温度函数法进行了残余应力和变形计算.结果表明,1段,3段,5段温度函数法分别将力学分析时间缩短91%,79%,63%,残余应力和基板变形误差均在20%以内,在满足计算精度的前提下显著提高了计算效率,为大型铝合金电弧增材制造件残余应力与变形的预测提供了途径.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.