自增强反应管残余应力的测试

介绍一种用Ｘ射线法测试自增强反应管残余应力的方法，并将试验结果与常用的镗削法加以比较，结果表明Ｘ射线法可以用于自增强管体的残余应力测试。     

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。     

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。     

X射线法测量多晶材料残余应力

简要介绍了机械工件(或构件)的残余应力的来源及其对机械工件使用寿命的影响。概述了晶体残余应力测量中的有损检测和无损测量各自所包括的具体测量方法以及各测量方法的特点和适用情况。重点阐述了X射线法测量残余应力的基本原理、特点和测量时应注意的问题。     

陶瓷—金属连接残余应力X射线衍射测试方法

用大功率的ＭＸＰ１８－ＨＦ Ｘ射线衍射仪测量了金属与陶瓷连接处的残余应力分布。实验表明，该衍射仪Ｘ射线强度高，光斑细，适用于材料残余应力分布的精确测量。通过用它对金属－陶瓷界面应力梯度的测量，为残余应力的缓解提供了依据。     

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.     

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.     

球罐裂纹及不同修复过程的残余应力

壁厚为42mm的1 500m3液化石油气球罐,运行4年后出现大量裂纹,在局部补焊中又反复出现裂纹,最后采用了对赤道带大环焊缝的重新焊接及整圈热处理才使球罐得以修复.用X射线法对该球罐进行了系统的残余应力测试.结果表明,内壁赤道带原始焊缝处残余应力高达0.72σs,说明球罐建造时的热处理效果较差;而局部修复及热处理后在焊缝附近残余应力接近或达到屈服应力,又表明局部热处理未起到应有作用.在球罐大环重新焊接及整圈热处理后的相同位置又进行两次测试,残余应力水平大幅度降低,整体下降约50%,显示最终的热处理效果良好.     

45Cr4NiMoV钢支承辊锻件表面感应淬火后的残余应力分布

采用机械剥层和电解剥层相结合的剥层工艺,利用X射线应力分析仪研究了支承辊锻件表面中频感应淬火后的残余应力沿横截面的分布规律。结果表明:180mm的45Cr4NiMoV钢支承辊表面中频感应淬火后表层为压应力,压应力层深约30mm,从表往里逐渐由压应力转变为拉应力,拉应力峰值出现在距表面约60mm处,不在支承辊锻件的中心部位。通过对支承辊锻件表面感应淬火后残余应力沿横截面分布规律的研究,可为生产特大型支承辊锻件制定合理的生产工艺方案提供可靠的试验依据。     

激光相变硬化提高旋转接头的耐磨性

为了提高35CrMo旋转接头的耐磨性,采用正交试验法研究了35CrMo旋转接头激光相变硬化适合的工艺方法和参数,获得的优化工艺参数为:激光功率P=1 500 W,光斑直径D=3.5 mm,扫描速度V=20 mm/s.结果表明:激光相变硬化层的平均硬度达786 HV1 N,比渗氮淬火提高了约30%,耐磨性提高了约1倍,表面残余应力大部分为压应力,能满足旋转接头工作要求,为改进旋转接头的表面处理方法提供了依据.     

Effect of Process Parameters on Laser Surface Hardening of Plain Carbon Eutectoid Steel

Influence of power density and interaction time for austenitisation during laser surface hardening of plain carbon eutectoid steel has been investigated. The analysis involves numerical prediction of thermal and solute diffusion profiles and thereby, the time needed for homogenization of austenite for different processing conditions. Experimental results provide qualitative validation.     

Simulation and Validation of Welding Residual Stresses Based on Non‐Linear Mixed Hardening Model

Abstract: This study contributes to Phase 2 of the Task Group 1 round robin in the NeT European Network. To obtain better prediction results, in the thermal analysis, two significant changes are used. The welding efficiency, η, is fixed at 75%, and the weld bead fusion boundary profiles are based upon macrographs taken from welded specimens, which have been destructively examined. In the subsequent mechanical simulation, a non‐linear kinematic or mixed isotropic–kinematic hardening model should be employed, and a progressive annealing scheme or explicit consideration of visco‐plastic or creep effects should be implemented to handle high‐temperature inelastic strains and reduce stress discontinuities. In this study, an uncoupled 3D thermal and mechanical analysis was carried out using the software code SYSWELD. In the thermal simulation, a two‐offset‐double‐ellipsoid heat source model was developed, and the parameters were fitted using the heat source fitting tool. Power intensity was applied to simulate 1‐s dwelling time at the weld start end. Offset distances between two double ellipsoids were adjusted to obtain the weld bead transverse fusion boundary profiles at different positions. Predicted temperatures were compared with the measured data by thermocouples on the test pieces. In the mechanical analysis, a new material constitutive model, non‐linear mixed hardening model, was developed. Tension–compression cyclic tests were simulated at different temperatures using three different material hardening models (isotropic hardening model, kinematic hardening model and non‐linear mixed isotropic–kinematic hardening model), and the predicted cyclic stress–strain curves were compared with the measured data. Effects of three different hardening models on the welding residual stresses were studied. Compared with the measured data, the optimum material hardening model was confirmed.     

Effect of Thermomechanical Treatment on X-Ray Elastic Constants and Residual Stresses in HSLA-100 Steel

The thermomechanical treatment of HSLA-100 steel is undertaken to upgrade its properties. The plastic deformation in our study was done below and above the recrystallization temperature of austenite, as well in the two-phase ( + ) region, followed by accelerated cooling. The plates were subsequently aged at two temperatures. The optical microstructures and hardness were done, and the effect of finish rolling temperature was established. The residual stress, X-ray elastic constants (XEC) and relative peak intensity were determined using X-ray diffraction. The effect of aging temperature on hardness, residual stress, Young's modulus, and Poisson's ratio was established. The residual stress values calculated using the XEC values obtained were found to be on the lower side compared to stress values using bulk elastic constants. The maximum difference in stress values is about 27%, which justifies the determination and use of XEC to obtain absolute values of stress.     

Corroding and Protecting of Surface Residual Stress With the Surface Hardening of Steel

The states of the stress with the surface hardening are analyzed, the related experiential formula of the stress -temperature and stress-depth hardened curves are set up, the protecting measures against hydrogen stress corrosion are discussed.     

喷丸起落架外筒焊接热影响区的残余应力测定

本文用X射线法测定了喷丸起落架外筒焊缝影响区的残余应力,并从残余应力角度考察了起落架外筒现行工艺路线的优劣。测定结果表明,在相同构件上虽然所测方向和部位不同,但残余应力的分布、大小及符号基本相同。与前起外筒相比,喷丸处理在主起外筒上形成的残余压应力值较低。分析认为消除焊接残余拉应力的合理工序,是两种外筒均应采用焊后热处理,但应防止表面脱碳。