X射线衍射法测试轧板表面残余应力

从试验角度讨论采用X射线衍射法测试轧板表面残余应力时遇到的一些问题。用X射线衍射法测试织构材料的表面残余应力时会出现2θ-sin2ψ震荡现象,但是测得的应力数据与加工工艺仍保持对应,反映出不同工艺对板材表面残余应力的影响。考虑到在较大的ψ角范围内缩小各衍射峰强度差异,对于面心立方钢铁材料宜选用(311)晶面测试。增加测试的ψ角站数也有助于得到好的应力测试效果。     

高强度钢丝残余应力的研究进展

回顾了近年来以珠光体钢丝为代表的高强度钢丝残余应力的数值模拟及其相关试验研究进展,主要介绍常规X射线衍射、中子衍射及同步辐射X射线衍射技术在钢丝残余应力分析中的应用,对残余应力的来源、测量原理及其结果进行了讨论;简述了残余应力对钢丝性能,如拉伸、应力松驰和环境促进断裂性能等指标的影响,同时对通过改变残余应力分布实现钢丝性能优化的主要工艺进行了介绍.     

Determination of Remnant Residual Stresses in Fracture Toughness Specimens Extracted From Large Components

Abstract: Material fracture toughness data are required to undertake fitness‐for‐service assessments of engineering components containing cracks. Calculations of crack driving force in the component are compared with material fracture toughness values to assess the likelihood of subsequent failure. Experimental measurements of fracture toughness are usually made on small specimens extracted from a larger ‘parent’ component following strict experimental guidelines, formulated to ensure measured toughness values in the fracture specimens are appropriate for use in the full‐size component. Implicit in this procedure is the assumption that the extracted fracture specimens contain no residual stresses, with any residual stresses in the full‐size component being accounted for in the crack driving force calculation. This paper considers a recent conjecture within the structural integrity community that the extracted fracture specimens may themselves contain a residual stress field which may influence measurements of fracture toughness. This could potentially lead to a degree of ‘double accounting’, i.e. the effect of residual stresses may be included in both the material toughness and the crack driving force. This, in turn, could lead to unnecessary conservatism in safety assessments. To explore this conjecture, the results of numerical modelling and neutron diffraction measurements of residual stresses in fracture specimens extracted from two different welded parent components are presented. One of the components is significantly larger than the extracted specimens, with the other being marginally larger than the extracted specimens. Results confirm the intuitive expectation that the residual stresses in specimens extracted from much larger components are negligible, whereas if the dimensions of the extracted specimens are comparable with the larger component then significant residual stresses may remain.     

用X射线衍射法测定振动时效后水电站钢岔管中的残余应力

介绍了采用振动时效技术消减水电站钢岔管焊接残余应力,以及用X射线衍射法进行焊接残余应力测试来对振动时效效果进行定量评价。并举例说明X射线衍射测试焊接残余应力的应用情况。     

单晶材料X射线应力测定原理与方法

结合单晶X射线应力测定基本原理,通过必要的理论分析,对现有单晶应力测定方法进行必要的改进和优化。基于工程实际应用需要,精简了单晶应力测定步骤并拓宽其应用范围,即不需要事先精确已知200,只需改变空间方位角驴和驴,再通过多元线形回归分析方法即可计算出各应力分量。最后给出了单晶应力测定的典型实例,即对同一部位重复测定应力,证实测量误差不超过±20MPa,说明该方法具有较高的测量精度和可靠性。     

残余应力检测与消除方法的研究现状及发展

残余应力的存在会严重影响工件的强度及相关性能,对残余应力的检测及消除方法的研究具有重要的理论意义及工程应用价值。从残余应力的概念及形成原因入手,介绍了钻孔法、X射线衍射法、磁测法、超声波检测法等测量残余应力的手段以及研究发展现状;同时阐述了热处理法、振动时效法、超声波冲击法等消除残余应力的方法。     

A Method for Determining X-ray Elastic Constants for the Measurement of Residual Stress

Abstract: The X-ray diffraction method is arguably the most convenient method of measuring residual stresses in terms of cost, spatial resolution, measurement time and the accuracy of measurement. The normal methods for calibrating X-ray diffractometers are not conveniently applied to automated scanning systems, however, and so a new approach is required. In this study, a scanning X-ray diffractometer was calibrated and the X-ray elastic constant for a steel alloy was determined using a customised four-point bending rig. The bending rig, in turn, was calibrated by dead loading. This study also described a simple alternative method for determining the X-ray elastic constant, without the use of specialised software. After calibration, the error band of the diffractometer was found to be less than ±10 MPa. As this is ±5% of the yield stress for a typical steel, this level of accuracy was deemed to be acceptable for the measurement of residual stress.     

电阻焊直缝焊接套管残余应力分布的测定

采用X射线法结合环劈法对电阻焊直缝焊接套管的管体和焊缝的应力分布,以及焊接套管切割后应力的变化进行研究。结果表明：焊接套管残余应力在周向上分布不均,并且焊缝处残余应力很高,接近其屈服强度;焊接套管切割后管体外表面残余应力随着时效时间的增长由拉应力转为压应力,而内表面由压应力转为拉应力。     

中子衍射测量残余应力研究进展

中子衍射技术是一种测量材料或工程部件内部的三维应力状态的方法。综述了近年来中子衍射在宏观部件焊接、热加工与热处理过程中残余应力测量的应用,在探究材料微观变形机理方面的应用,在金属基复合材料与多相合金中各相微观应变测量的应用,以及与其他残余应力测量技术对比等方面的研究情况,并展望了中子衍射测量技术的应用前景。     

晶体材料内部残余应力衍射法无损检测的研究进展

目前能够准确、无损地测试材料内部残余应力的手段主要是中子衍射和同步辐射,但这两种测试手段需要核反应堆或高能同步辐射源,投资巨大,只为少数发达国家的少数实验室所拥有,难以应用到实际生产中。短波长X射线衍射仪通过钨靶-K_α特征射线(波长约0.02 nm)以及独特的谱接收方式,达到或接近同步辐射及中子衍射对晶体材料内部晶格应变的无损定点测试,为内部残余应力无损检测的广泛应用开辟了一条新的渠道。介绍了中子衍射和同步辐射对残余应力测试的国内外研究现状,重点展示了短波长X射线衍射仪用于内部应力测试的结果,并就三种测试方法特点进行了对比分析。     

简述2015年至2019年残余应力学术进展

概括介绍了近几年残余应力技术应用研究的进展,还介绍了激光冲击强化技术的相关问题,以及中子衍射和同步辐射残余应力技术发展概况.并将残余应力分类及其X射线表征、形变强化的机制等方面不同的学术观点进行了归纳,供业界参考.     

挤压管状SiCw/Al复合材料中残余应力及其高温松弛行为

利用X射线应力测量方法,研究挤态20vol%SiCw/6061Al复合材料中残余应力,发现复合材料中存在较大的残余应力,而且各方向的残余应力分布很不均匀,动态测量去应力退火期间复合材料残余应力的高温松弛过程,证实高温状态下残余应力按幂指数的方式发生松弛,基于蠕变机制,分析残余应力搞温松弛行为,结果表明复合材料应力指数及应力松弛激活能明显高于基体合金。     

铸造TC4钛合金电子束焊残余应力测试

对铸造TC4钛合金进行电子束焊接,使用X射线衍射法对焊后母材、热影响区以及焊缝的表面残余应力分布状况进行测试和分析。结果表明：垂直于焊缝方向的测试点上,焊缝及热影响区在横、纵两个方向上主要存在拉应力;剪切应力数值均在±50MPa范围内,可以认为对焊缝性能没有影响。沿焊缝长度方向的测试点上,无论横向应力还是纵向应力,焊缝起始端的应力值要低于焊缝终止端的应力值。纵向残余应力表现为拉应力,横向残余应力由压应力逐渐向拉应力方向转变。     

搅拌摩擦焊接件内部残余应力无损测试研究进展

搅拌摩擦焊是近年来发展的一种新型焊接技术,目前国内主要着力于搅拌摩擦焊工艺及应用方面的研究,但由于测试方法和相关设备的限制,关于搅拌摩擦焊接件内部残余应力的研究几乎是空白,而国外利用其先进的中子衍射和高能同步辐射装置已经开展了较多搅拌摩擦焊接件内部残余应力的无损测试。综述了近10余年来国外搅拌摩擦焊接件内部残余应力测试的研究进展,讨论了影响残余应力测试结果的各种因素;最后介绍了国内用短波长X射线衍射仪测试材料内部残余应力的探索,对未来准确、高效、经济而无损地测试搅拌摩擦焊接件内部残余应力的研究方向进行了展望。     

欧美最新X射线衍射残余应力测定标准介绍

对最新的欧盟X射线衍射残余应力测定标准EN15305-2008,从测试原理、材料特性、仪器的选择、限制条件及处理方法等方面进行了详细的介绍。指出在进行X射线残余应力测定时特别需要注意以下几个方面：EN153052008和美国X射线残余应力测定标准ASTME915—2010均明确要求采用不假定剪切应力为零的完整应力方程和椭圆拟合方法,否则会出现系统误差;用于拟合的sin^2φ值在正负妒方向上最少需要测试7个,建议测试9个以上;测定钛合金材料残余应力时建议使用铜靶X射线管,如使用其他靶材则需考虑X射线穿透深度不同带来的与标准方法的差异;应选择高能量分辨率、不易产生X射线辐射饱和的探测器;无应力铁粉残余应力测定的精度要求为正常±6．9MPa,最大±14MPa。     

预拉伸厚铝板内 部残余应力 与晶粒取向均匀性的研究

目的消减预拉伸铝板内部残余应力。方法利用短波长X射线衍射仪(SWXRD),分别对某公司国产25 mm厚2024-T351预拉伸铝板,以及美国铝业公司(ALCOA)20 mm厚7075-T651预拉伸铝板的内部残余应力、内部织构及其沿板厚的分布,进行了无损测定。结果 ALCOA的20mm厚7075预拉伸铝板内部残余应力小于25 MPa,其内部晶粒取向沿板厚均匀分布;而某公司原工艺生产的25 mm厚2024预拉伸铝板,内部残余应力高达100 MPa左右,其内部晶粒取向沿板厚分布很不均匀。结论源自于轧制的内部织构沿板厚分布的不均匀性,使得以消减残余应力为目的的预拉伸处理中的铝板塑性变形不均匀,导致某公司国产预拉伸铝板内部残余应力的消减效果差,在其后续加工中容易产生加工变形超差的问题,需要抑制强剪切织构的产生,减小织构在整个板材厚度上的不均匀分布程度。     

Confirmation of Principal Residual Stress Directions in Rectilinear Components by Neutron Diffraction

Abstract: Large magnitude residual stresses in precipitation hardened aluminium alloys are a consequence of inhomogeneous plastic deformation arising from thermal strains. Thermal gradients develop because of the metallurgical requirement to quench the material rapidly from the solution treatment temperature. Characterisation of the resulting residual stresses can be usefully performed by neutron diffraction. For rectilinear shapes, it is usually assumed that the orthogonal directions of the sample are coincident with the principal stress directions. To test this assumption, residual strains were measured in a rectilinear block of the aluminium alloy 7449 using the SALSA neutron strain analyser. The strains at a single point in the forging were measured as a function of orientation; that is the forging was rotated around the three orthogonal axes of a coordinate system with its origin at the measurement point. Analysis of the neutron diffraction data allowed the determination of the full three‐dimensional strain and stress tensors which confirmed that the orthogonal directions of the forging did coincide with the principal stress directions.     

转速对 7075-T651 铝合金搅拌摩擦焊接件内部残余应力分布的影响

目的掌握铝合金搅拌摩擦焊接板内部残余应力的分布,为控制焊接残余应力、改进焊接工艺和提高焊接件质量。方法以13.6 mm厚的7075-T651铝合金为研究对象,用短波长X射线衍射技术,对在不同搅拌头转速下搅拌摩擦焊接板内部的残余应力进行了无损测试,并对焊接接头在板厚中心层上的微观组织和显微硬度进行了研究。结果在垂直于焊缝截面上的显微硬度均呈"W"型分布,焊核区的显微硬度高于其两侧的热机械影响区和热影响区,但低于母材区的硬度;随着转速的增大,接头硬度的最小值减小,低硬度区的范围越大。横向残余应力绝对值整体小于焊接方向;焊核区为正应力,热机械影响区残余应力减小且变化梯度最大;残余应力的极大值位于热影响区和热机械影响区的交界处;残余应力极大值与硬度最小值的位置重合。结论通过残余应力的无损检测分析,不仅可以直接获得加工件内部应力分布,还可以间接获得加工件内部的加工缺陷情况,为改进加工工艺、提高成形精度提供依据。     

Residual Stresses in Plasma-Sprayed Coatings Al 2 O 3

Residual stresses affect significantly the quality and performance of thermally sprayed coatings. The residual stresses in alumina coatings were investigated by means of X-ray diffraction with Cr- and Cu-radiations. The sin² method could be applied to the evaluation of the stress fields. A very small stress gradient was indicated in surface layers of alumina coatings.     

两种残余应力测定方法的研究和比较

先用X射线衍射法再用盲孔法测定了同一试样的残余应力,对测试结果进行了分析比较。结果表明：对于残余应力分布不随深度改变的情况,两者结果一致;但对于其他情况,两种方法得到的结果不一致。通过测试残余应力沿试样深度的分布和从原理上比较两种测试方法的不同,得出盲孔法的测试结果受深层残余应力分布影响,而X射线衍射法的测试结果不受其影响。