超声法焊缝残余应力检测技术研究

文中基于声弹性理论,研究临界折射纵波（CriticallyRefractedLongitudinalwave,LCRwave）残余应力检测原理,通过超声波传播速度的变化,反映出构件表面和内部的残余应力,从而验证采用LCR波检测构件中残余应力的关键技术,具体包括LCR波的激发、接收和后续处理。设计并制作了基于声时的残余应力检测实验系统。声时是整个测量系统中的关键量,其测量水平决定残余应力的测量精度。在实现过程中采用“一发一收”的探头布局模式,通过测量固定长度上声时传播的变化,分析残余应力的分布情况。     

改善管道环焊缝接头残余拉应力的研究

本文对管道环焊缝残余应力的产生机理与分布规律进行研究。通过调整应力分布的工艺,可以显著降低焊接接头内表面残余拉应力,甚至产生压应力,从而提高管道抗应力腐蚀开裂的能力。     

环焊缝管道焊接应力应变三维有限元分析

利用ＡＤＩＮＡ非线性分析程序,考虑材料力学性能依赖于温度变化　,对低碳钢管道环焊缝接头进行三维有限元分析。通过焊缝单元“死、活”选择,模拟了焊　接热源的移动过程。结果表明：焊缝及附近的轴向残余应力在内表面为拉应力,外表面为压　应力;焊缝及附近的环向残余应力在内、外表面均为拉应力。计算值与实测值基本一致,表　明有限元法能够有效地预测管道环焊缝接头的残余应力。     

浅谈返修焊缝中残余应力的测定

为了确保返修焊缝的质量,除保证焊缝内无夹渣、气孔、裂纹、未焊透,焊缝外观上无咬边,焊缝圆滑过渡和有一定的焊缝尺寸要求外,还应尽量减少返修焊缝的残余应力。因为焊接残余应力的存在,往往会使焊接结构的许用应力降低,疲劳强度下降,同时还会使焊接结构或材料的薄弱环节出现裂纹。如果在高压下工作的,容器内存在着较高的焊接残余应力,将是十分     

不同坡口焊缝残余应力的有限元分析

对接焊缝在不同坡口型式时残余应力的影响是不同的。应用有限元方法,对不同坡口型式焊缝的残余应力进行了有限元分析,得出不同型式焊缝的残余应力分布与大小,为制定正确的焊接工艺、改善焊缝性能等实际生产和使用提供理论依据。     

相变对管道环焊缝残余应力的影响

利用ADINA程序计算了管道环焊缝接头未考虑相变和考虑相变两种情况下的残余应力,有限元分析中考虑了材料热物理性能参数和力学性能参数的温度相关性.结果表明,考虑相变应力比未考虑相变应力,其外表面的轴向压应力值增加,内表面的拉应力值降低;外表面的环向应力出现压应力,内表面的拉应力值降低,最大拉应力的峰值区偏向近缝区.这说明相变应力对管道接头焊缝和近缝区有较大的影响.计算结果与实测结果基本一致,对焊接接头的金相组织分析也验证了计算结果.     

薄壁筒焊缝残余应力研究

介绍了薄壁筒焊缝残余应力的实验研究。研究结果表明 ,薄壁筒环焊缝存在残余压应力 ,且垂直于焊缝纵向呈压应力分布 ,同时通过电测实验 ,对电测法测定压力容器残余应力的可靠性及测试精度进行了探讨和评价。     

薄壁金属直缝圆焊管残余应力超声检测

为了研究小口径的薄壁金属直缝圆焊管焊接区域残余应力的大小,利用临界折射纵波对焊管焊接区域进行残余应力检测。结合静载拉伸实验标定了焊管的声弹性系数。结果表明,残余应力随着拉伸距离的增加而变大;拉伸距离相同时残余应力随着焊管直径的增大而增大;声弹性系数与焊管直径无关。通过与盲孔法检测实验的对比,结果表明了临界折射纵波检测残余应力是可靠的。     

焊缝线膨胀系数匹配对焊接残余应力的影响规律

采用热弹塑性有限元法对焊缝与母材线膨胀系数匹配对焊接过程中的动态应力以及残余应力的影响规律进行了研究。在相同焊接热源模型和热输入量作用下的计算结果表明,焊缝与母材等胀匹配时,焊缝中心的纵向残余应力σｘ为拉应力,其值随母材屈服强度σ＾ｐｓ变化。     

Uncertainty of residual stresses measurement by layer removal

A model to evaluate the uncertainty in the measurement of the through-thickness residual stress distribution in plates by the layer removal technique is presented. Thin layers were chemically etched from a stripe on rectangular specimens cut from a low carbon cold-rolled steel sheet. Phase shifting laser interferometry was used to measure the ensuing curvature. Polynomials were least-squares adjusted to the curvatures as a function of the etched depth. The polynomials were inserted into an integro-differential equation relating the curvature to the residual stresses, which were assumed to be a function of depth only. A comparison with X-ray diffraction measurement of the surface residual stresses showed good agreement. The uncertainty was found to increase steeply at the surfaces and to depend mainly on the assumed value for the modulus of elasticity, on the curvature fit, and on the depth of etching.     

On analysis and measurement of residual stresses in the bending of sheet metals

A new method for evaluating distribution of residual stresses in bent sheet metals is presented. Due to the non-uniform distribution of strain and stress across thickness, springback on unloading induces residual stress in a bent specimen. The authors have formulated the problem and shown that the springback and residual stresses can be expressed as a function of geometric parameters and material properties of sheet metals, e.g. bending curvature, thickness, Young's modulus, work-hardening index, etc. The layer-removing method was used to determine the residual stresses in the study. By simulating the layer-removing process, analytical measurement of the residual stress was made. The analytical results were compared with the experimental data measured, and a good agreement was found.     

An ultrasonic method for measuring residual mechanical stresses in the rims of solid-rolled railroad wheels that considers the intrinsic anisotropy of the material

The acoustic properties of the material of solid-rolled railroad wheel rims are investigated. The results of the assessment of the intrinsic anisotropy of the material are reported. An analytical expression for calculation of the residual mechanical stresses in a rim that considers the effect of the material’s intrinsic anisotropy is obtained. A method for the ultrasonic testing of the distribution of the residual stresses is proposed. The results of the experimental investigation and practical application of the method at iron-and-steel plants are given.     

Estimation of residual stresses in locomotive wheel treads using the acoustoelasticity method

An ultrasonic method for the estimation of residual stresses in locomotive wheel treads with the electromagnetic acoustic excitation and reception of elastic waves is described. The results that were obtained for the distribution of residual stresses along the thickness of treads by the calculation and experimental methods with consideration for textural and structural factors are reported.     

Evaluation of residual stresses in rims of wagon wheels using the electromagnetic-acoustic method

A technique for testing residual stresses in the rims of solid-rolled wagon wheels with an ultrasonic method using the electromagnetic-acoustic method of exciting-receiving acoustic signals is described. An engineering solution that makes it possible to obtain trains of bottom signals using electromagnetic-acoustic transducers is proposed. The results from determining residual stresses in new and used wagon wheels are presented.     

A nondestructive acoustic method for estimating the residual stresses in a hardened layer

A theoretical model for estimating the residual stresses in a hardened layer of axially symmetric articles by a nondestructive acoustic method is considered. A technique of experimental investigations and an algorithm for estimating the residual stresses are presented. The envelope of a signal scattered by a structure and arising during propagation of ultrasonic waves in a hardened layer is qualitatively identified.     

Measurement of the residual stresses in the treads of railway wheels by the acoustoelasticity method

In this work, we present data on the residual stresses measured in the treads of 957-mmdiameter railway wheels using a nondestructive ultrasonic method on an ИH-5101A device. The measurement results show that the residual stresses are compressive and modulo increasing from the center to the periphery for each tested point. The reliability of the data is confirmed by a destructive method (cutting a wheel along its axis).     

A comparison of residual stresses in built-up steel beams using hole-drilling method

Residual stresses have a significant effect on the stability resistance of metal building systems. An experimental program was conducted to measure these stresses in built-up steel beams using incremental hole-drilling method. The experimental results reveal that the predicted residual stress type of pattern for built-up I-sections with fillet welds on one side of the web is not the same as the pattern of residual stresses in built-up I-sections with fillet welds on both sides of the web. This paper was recommended for publication in revised form by Associate Editor Youngseog Lee Mohammed Al-Nawafleh received his B.S. and M.S degrees in Mechanical Engineering from Leningrad Institute of Textile and Light Industry, in 1989. He then received his Ph.D. degree from Sankt-Petersburg State University of Technology and Design, Russia in 1993. Dr. Nawafleh (1997–2005) was a Professor at the Department of Mechanical Engineering at Al-Balqa’ Applied University in Jordan. From 2005 to 2008 he was a Professor at the Department of Mechanical Engineering at Tafila Technical University, and currently he is a Professor at the Department of Civil Engineering at Al-Hussein Bin Talal University, Jordan.     

Modeling of residual stresses in milling

A model to predict residual stresses produced from milling is presented. It uses process conditions as inputs and predicts surface and subsurface residual stress profiles due to milling. The model formulation incorporates cutting force and cutting temperature predictions and utilizes those parameters to define the thermomechanical loading experienced by the workpiece. Model predictions are compared with published experimental data for both cutting forces and residual stress profiles. The results show that the model performs well in predicting residual stress trends for various milling conditions. Residual stress magnitudes as well as profiles are well predicted with the modeling approach.