7050和7075铝合金板材的淬火残余应力

铝合金板材的残余应力主要产生于淬火过程中,而残余应力是导致航空航天用铝合金板材机加工变形的主要原因。采用X射线衍射法、超声波法和盲孔法分别对7050铝合金板材水浸淬火试样的残余应力进行了测试,并对3种方法的测试结果进行了对比和分析;采用超声波法对7075铝合金板材喷淋淬火试样的残余应力进行了测试。结果表明:超声波法测得的7050铝合金板材水浸淬火试样的残余应力分布规律与X射线衍射法和盲孔法测得的具有较好的一致性,板材近表层处的残余应力随着测试深度的增加而减小;7075铝合金板材喷淋淬火试样的残余应力随着辊速和喷水量的增大而增大。     

X射线法测量淬火铝合金厚板表面残余应力

采用无损X射线衍射技术测试了7075铝合金厚板淬火后表面残余应力水平与分布,得到了淬火铝合金厚板表面残余应力的分布区间和一般规律,分析了准直管对测试结果的影响,并与中心钻孔法得到的结果做了比较。结果表明,两种方法都能有效并正确测量构件的表面残余应力,但中心钻孔法不适合用于应力梯度大的场合,而X射线法在无应力或原始应力水平很低的场合效果欠佳。淬火铝板表面残余应力的测试结果呈正态分布,且淬火过程中边缘局部有应力释放,释放值可达40%,且此区域大小约为铝板的一个厚度。     

应用纳米压痕法测量电沉积镍镀层残余应力的研究

应用纳米压痕法测量残余应力的2种理论模型对5种电沉积镍镀层中的残余应力在不同压痕深度处进行了测量,并与X射线衍射法的测量结果进行了比较.结果表明,压深位于薄膜/基底界面处的2种压痕法测量结果与X射线衍射法的测量结果相近,且Yun-Hee模型与其符合得更好.     

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。     

X射线应力仪侧倾法测定板材的残余奥氏体含量

采用X射线应力仪侧倾法对某型板材的残余奥氏体含量进行了测定，研究了测试条件对测定结果的影响。结果表明：不同试样表面状态、不同测试方向和侧倾角度的单次测定结果之间存在较大的差异，因而单次测定结果不适合作为最终测定结果；就不同侧倾角残余奥氏体含量测定结果的平均值而言，试样表面状态对测定结果没有明显的影响．并4用X射线应力仪，采用多个测试方向、较大直径的准直管和多个侧倾角进行残余奥氏体含量测定，可以获得较为均匀一致的残余奥氏体含量平均值。     

高钢级大口径焊管残余应力的测试方法

针对X80钢大口径UOE,JCOE和SAWH(螺旋缝埋弧焊)三种焊管,研究了盲孔法、切块法和切环法在高钢级大口径焊管残余应力测试中的应用.结果表明:对于这三种管型,通过切环法估算的残余应力与盲孔法和切块法的测试值较为接近,三种方法的结果重合性较好.     

X射线衍射法测残余应力的“突变”现象与定峰技巧探讨

X射线衍射法（XRD）是一种常用的测试金属表面残余应力的无损检测法。依据X射线应力测试的原理,对试验中遇到的衍射强度“突变”现象进行了初步探讨,并对其产生的原因和定峰中的处理方法进行了具体分析,为进一步发展和完善铝合金焊接残余应力的X射线分析技术提供了参考。     

金属基复合材料残余应力测定

分析了金属基复合中热残余应力的形成机理及表现特点，并对几种常用的测定金属基复合材料残余应力的方法进行了分析比较，普通Ｘ射线法虽然简便、经济、但穿透能力有限，所测值仅反映试样表面的残余应力状态；中子衍射的区域较大，测出的仅是残余应力平均值。Ｘ射线能量衍射法虽然穿透能力较强，能测出试样内部较深范围的残余应力，但由于产生衍射法穿透力强，分辩率高，能测出复合材料内部的残余应力场梯度，是测定金属基复合材料残     

Q345钢对接焊缝的残余应力测试

Q345低合金钢是大型起重机械主要受力结构件的制造用材,其母材及焊缝的残余应力是影响起重结构疲劳寿命的重要因素。试验采用X射线衍射法对Q345钢对接焊缝试样的残余应力进行测试分析,得到Q345铜表面残余应力的分布曲线。结果表明焊缝熔合线区域的残余应力梯度较大,该区域应重点关注。     

测试大型汽轮机转子残余应力的环芯法和X射线法

采用X射线法对汽轮机转子近表面的残余应力进行了测试,结果表明,不同的加工方式,其残余应力的状态和分布是不同的。应用环芯法和X射线法测试了汽轮机转子的残余应力,其结果是相近的,环芯法是目前国际通用的测试方法,值得采用。     

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。     

Zur Ermittlung verformungsbedingter Makro- und Mikroeigenspannungen durch mechanische und röntgenographische Eigenspannungsanalysen

Analysis of deformation induced residual macro-and microstresses by mechanical and X-ray methods Residual stress distributions in plastically deformed tensile and bending specimens of perlitic steel were analysed using X-ray diffraction technique and incremental holedrilling method. After tensile loading compressive residual stresses are measured by X-ray analysis in the ferrite phase. Consequently X-ray analysis detects compressive microstresses. In the case of bending specimens residual macrostresses are superposed with residual microstresses after unloading. In no case identical residual stress values were measured by X-ray and hole drilling methods. Microstresses can be separated combining both measurement methods. Microstresses after tensile loading were found to be greater than in surface layers of respective bending samples subjected to the same amount of plastic strain.     

Procedure to Perform a Validated Incremental Hole Drilling Measurement: Application to Shot Peening Residual Stresses

Abstract: The paper describes a test rig designed to check and assess the accuracy of the incremental hole drilling (IHD) method. An external load produces a controlled linearly through thickness variable uniaxial stress field (reference bending stress), known with good accuracy, that can be applied and removed at each hole increment. After the separation between the bending relaxed strain from the residual stress relaxed strain, it is possible to reproduce the bending stress distribution in order to have complete confidence of the residual stress measurement. The bending verification of the IHD method was already proposed by other investigators before, but residual stress measurements were then performed on independent configurations. The proposed testing procedure gives a ‘real time’ verification of the residual stress measurement. Any experimental malfunctioning due to the operator inexperience, or any error during the stress calculation from the relaxed strain would produce an evident difference between the expected reference bending stress and the IHD bending stress output. Moreover, the reference bending stress helped for understanding that the not perfect hole cylindrical shape causes an underestimate of the predicted stress near the surface. A zero depth offset correction was proposed. This correction was tested on the reference bending stress, and then applied to the residual stress prediction. Three shot peening residual stresses IHD measurements were successfully validated by means of the bending stress; moreover, they were in good agreement with independent X‐ray diffraction measures also proposed in the paper.     

Development and comparison of residual stress measurement on welds by various methods

Abstract

Residual stress constitutes an integral part of the total stress acting on any component in service. It is imperative to determine residual stress to estimate the life of critical engineering components, especially those that are welded. The stresses caused by non-uniform temperature distribution due to welding and the effect of these multiaxial stresses upon service performance are discussed. A controlled thermal severity test (CTS) was performed on mild steel plates bolted together, with anchor welds deposited on opposite sides. After cooling, bithermal and trithermal test welds were deposited one after the other. Varying welding stresses were deliberately introduced by using different thicknesses of both plates to change the thermal severity numbers (TSN). The main experimental technique used here to determine the magnitude and nature of residual stress is based on X-ray diffraction (XRD). It was utilised to develop and standardise other techniques. The XRD method is based on the peak shiftin the diffraction profile due to the presence of stress using a sin² ψ method. The peak shift is determined by orienting the sample at different angles ± ψ to the incident X-ray beam. The semidestructive technique of hole drilling and use of a strain gauge was also employed to determine residual stress in CTS specimens. The magnitude, nature, and direction of principal stresses were determined by relieving stresses through incremental blind hole drilling and measuring strain values at each step. The surface displacements arising due to hole drilling can also be determined by laser holography. A sandwich holography technique was developed to avoid unwanted rigid body motions of samples due to hole drilling when relieving stresses. Stress values were obtained by measuring fringe displacement between two exposures of a sandwich hologram, due to hole drilling. Results on the change in residual stress values with TSN are discussed. The residual stress values determined by XRD and sandwich holography were found to be comparable, and stress values obtained by hole drilling/strain gauge measurement were higher than these values. The reasons are discussed.     

Extension to the blind hole drilling technique for residual stress determination with airabrasive hole forming

For an austenitic clad ferritic steel plate it was necessary to determine the residual stress state between the austenitic surface and a region below the austenitic/ferritic interface.
The thickness of claddings was 6 mm and to determine the stress variation between the surface and 8 mm an incremental analysis is required. Any material removal en masse in conjunction with small hole residual stress measurements would have resulted in a stress redistribution and hence a distortion in the stress field being measured. In conjunction with strain change measurements on the other face the sensitivity would not have been sufficient. These two options assume that a thin layer of material over relatively large areas can be removed by a non-stress inducing technique.
A blind hole residual stress measurement using a 13 mm diameter hole 13 mm deep will facilitate accurate incremental analysis to a depth of 8 mm.
The end mill method of hole forming cannot be used with stainless steels because of the random damage effect which is induced in the readings. The airabrasive method which induces no damage effect was used.
The standard airabrasive method of hole forming produces a 2 mm diameter and a 2 mm deep hole.
The modification of the standard airabrasive system is discussed which enables 13 mm diameter and 13 mm deep holes to be formed.
A deviation from the standard hole/gauge layout geometry has been investigated due to non-availability of suitable standard rosettes, and a significant increase in sensitivity has been obtained.
The incremental stress results for the austenitic layer and the austenitic/ferritic interface are discussed using the results from 1.6 mm, 3.2 mm and 13 mm diameter/deep holes.     

Moiré Interferometry Assessement of Residual Stress Variation in Depth on a Shot Peened Surface

Abstract: The main goal of this work was the development of experimental techniques to measure in depth non‐uniform residual stresses, as alternative to the more conventional hole‐drilling method with strain gauges. The proposed experimental methodology is based on moiré interferometry. This high resolution field technique allows in‐plane displacement assessment without contact. Grating replication techniques were also developed to record high quality diffraction gratings onto the specimen’s surface. A laser interferometry setup was implemented to generate the master grating (virtual). The stress relaxation was promoted by blind hole‐drilling and the obtained fringe patterns were video recorded. Image processing techniques were applied to assess the in‐plane strain full‐field. A finite elements code (FEM), ANSYS^®, was used to simulate the stress relaxation process and to calculate the hole‐drilling calibration constants.     

热时效对消除钢结构焊接残余应力的工艺评估

针对钢结构拼焊过程中产生的焊接变形和残余应力,采用热时效工艺对焊接构件进行了消应力处理,然后采用盲孔法对焊接构件焊后和热时效后的残余应力分布及变化进行了测定,定量地评估了热时效消除钢结构焊接残余应力的工艺效果。结果表明：通过热时效处理,可使钢结构的焊接残余应力大大降低,消除应力效果良好。     

Application of multiple residual stress determination methods to coarse-grained biomedical implant castings

ASTM F75 femoral knee implant components distort during manufacture due to residual stress re-distribution or inducement. X-ray diffraction, neutron diffraction, centre-hole drilling and the contour method residual stress determination techniques were applied to as-cast and/or shot-blasted components. The centre-hole drilling and contour methods can only be considered qualitative as a result of uncertainty associated with the elastic anisotropy of gauge volumes. Additionally, neutron diffraction experimentation returned unfeasible results. However, it was qualitatively identified that a shot-blasting shell-removal process has the ability to significantly alter the bulk residual stress state of the implants and induce a stress state which would cause distortion by re-distribution following material removal during manufacturing processes.