金属材料残余应力的超声测量方法的探索

测量金属材料残余应力的超声技术是基于超声波速度随应力的变化．本文描述用超声瑞利波测量金属材料由热处理引起的表面残余应力的方法．     

用超声波技术测量螺栓轴向紧固应力

超声波速度会因材料中加载应力而产生微小的变化，这一现象特别适用于测量螺栓的轴向应力。根据螺栓的轴向应力与超声波传播时间变化率的关系，作者研究了一种可直接测量螺栓轴同应力的仪器。实验结果显示，本项技术十分适合现场的实际应用。     

现代超声工业测量的若干发展

超声波在工业测量领域中的可用性非常广。目前，由于现代电子技术与微机技术的飞速发展；这种可用性得到愈来愈多的体现。本文简要介绍了超声波技术在若干方面的研究进展，其中包括：高精度声速测量，材料应力测量，化工过程检测及超声谱分析技术。     

螺栓形状对其紧固应力超声测量的影响

利用超声波技术直接测量螺栓轴向紧固应力的方法得到的螺栓轴向平均应力。本文根据工程上的实际情况，给出了螺栓形状对其曼固应力超声测量影响的简易修正途径，从而提高了这一技术的准确性。     

超声波流量测量技术及发展

本文叙述了超声波流量测量的原理、基本测量方法以及传统的多普勒和时差法超声波流量计的缺陷和测量局限性，分析了超声波流量测量最新进展所采取的新的测量技术和方法，并介绍了超声波相关流量计的原理和技术特点．     

超声波声速测量的谱分析技术

超声波声速测量的谱分析技术只需要产生和接收一次脉冲超声波,对超声波透射信号进行谱分析,即可得到材料声速,可以测量厚度较薄材料的声速,并且该技术可以广泛应用于自动化测量中。该技术既可应用于固体,也可应用于液体的声速测量。通过对铝板和钢板进行测量,并运用快速傅立叶变换和自回归模型进行谱分析,实验结果与理论分析结果一致。     

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。     

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。     

纤维增强复合材料声学性能检测方法研究

利用超声脉冲反射法直接测量材料声学性能的原理和方法,对声速、声阻抗和衰减系数等进行测量,并对影响材料的声学性能测量的因素进行了探讨,说明了纤维增强树脂基复合材料声学参数的测量方法,实验结果表明：基于超声检测原理,将超声波发射接收电路与数字化技术相结合,采用脉冲回波反射法是测量纤维增强树脂基复合材料声学性能的有效方法．只要测量条件选择适当,可以准确地测量材料的声学性能。     

用超声声速仪测量球墨铸铁的球化率

1测量原理 超声波在材料中的传播速度受材料的组织结构和特性的影响。就铸件而言，铸造工艺和后续的热处理决定了铸件的微观结构，包括金相组织、石墨的形状、尺寸大小和分布状态。特别是石墨的形态明显影响铸铁的力学性能。同样．石墨的形态也明显影响超声波在铸件中的传播速度。因此．利用测量超声波声速就可以控制铸铁中石墨状态。     

Taguchi optimization and ultrasonic measurement of residual stresses in the friction stir welding

The main goal of this study is optimization of residual stresses produced by friction stir welding (FSW) of 5086 aluminum plates. Taguchi method is employed as statistical design of experiment (DOE) to optimize welding parameters including feed rate, rotational speed, pin diameter and shoulder diameter. The optimization process depends on effect of the welding parameters on longitudinal residual stress, which is measured by employing ultrasonic technique. The ultrasonic measurement method is based on acoustoelasticity law, which describes the relation between acoustic waves and internal stresses of the material. In this study, the ultrasonic stress measurement is fulfilled by using longitudinal critically refracted (L_CR) waves which are longitudinal ultrasonic waves propagated parallel to the surface within an effective depth. The ultrasonic stress measurement results are also verified by employing the hole-drilling standard technique. By using statistical analysis of variance (ANOVA), it has been concluded that the most significant effect on the longitudinal residual stress peak is related to the feed rate while the pin and shoulder diameter have no dominant effect. The rotational speed variation leads to changing the welding heat input which affects on the residual stress considerably.     

提高碳纤维增强树脂基复合材料弹性常数超声表征精度的方法

为提高碳纤维增强树脂基复合材料（Carbon Fiber Reinforced Plastic,CFRP）单向板弹性常数的超声表征精度,基于超声液浸背反射法开展了实验测量和数值模拟。首先,搭建了角度旋转测试装置,并结合信号互相关处理技术实现了不同方向上的延时测量和声速计算;然后,通过模拟退火优化算法反演声速数据,得到了5个独立弹性常数;最后,利用理论计算和CIVA软件模拟仿真对实验测量结果进行了验证。结果表明:1-3平面内准纵波和准横波声速随入射角度而变化,与1-2平面内的表现出明显差异,由此显示材料为横观各向同性的;独立弹性常数分别为12.88、6.39、126.83、4.85、2.97 GPa;理论计算、CIVA软件模拟仿真及实验测量结果的声速偏差小于6.4 m/s,实验数据波动范围小于0.33%,对应的弹性常数误差均小于0.47%。相关方法同样适用于其他正交各向异性介质的弹性常数测试。      

微电铸层内应力超声去除实验

针对Ni微电铸层中内应力过大的问题,提出用超声时效技术去除铸层内应力的方法.利用自行研制的超声设备对铸层内应力进行去除,借助X射线衍射仪和应力测量公式求得超声前后的内应力大小,并对实验结果进行对比.结果显示,铸层内应力在50min时去除最为明显,平均应力由-209.0MPa减小到-109.0MPa,减小了100MPa,消除率达到47.9%.可知在合适的实验参数下利用超声时效技术可以有效地减小和消除电铸层的内应力.超声时效去应力效果与热处理效果相当,能够满足微器件的使用要求,具有一定的实用价值.     

Investigation of Stress and Temperature Effect on the Longitudinal Ultrasonic Waves in Polymers

This work aims at establishing the effect of stress and temperature on the velocity of ultrasonic longitudinal waves in typical engineering polymers, and evaluating the potential of ultrasonic stress measurement in the evaluation of residual stresses in polymer parts. In order to estimate the effect of material morphology, two amorphous and two semicrystalline polymers have been considered. A series of tests are implemented, to determine the acoustoelastic constants and temperature constant of materials, by using the designed transducer fixtures for in situ measurement of longitudinal wave velocity. As expected, the velocity changes linearly with stress and temperature, and the temperature effect is as important as the acoustoelastic effect. It shows that this kind of nondestructive method is a valuable quantitative tool to estimate the residual stress in polymer products, but the material temperature influence must be considered during the estimation.     

Analysis of the couplant influence on the ultrasonic thickness measurement of the steel grade S355J0

The ultrasonic thickness measurement is the most commonly performed technique as a part of quality management of systems and constructions. The paper carries out a study of the couplant impact on the wall thickness ultrasonic measurement results. Experimental samples are made from the steel grade S355J0. By performing a theoretical and experimental analysis, it estimates that there exists a significant effect of the particular parameters of the ultrasound transducer, the couplants type and their interactions on the thickness measurement results. An experiment scheme and the appropriate methodology for experimental results analyses create the preconditions for the assessment of the influence of the couplant type, material thickness and the parameters of ultrasound probe to the measurement uncertainty.     

Sub-surface stress measurement of cross welds in a dissimilar welded pressure vessel

Manufacturing process of pressure vessels used in high-temperature applications normally needs employing dissimilar metal welds (DMWs) between austenitic and ferritic steel. However, high amount of thermal stresses at the welds are induced due to differences in coefficient of thermal expansion between the types of steel. This study investigates the evaluation of welding residual stresses in a pressure vessel manufactured by DMW of 316 L stainless steel shell to A106 carbon steel caps as well as similar welding of stainless steel shells. By using longitudinal critically refracted (LCR) ultrasonic waves, the residual stresses are experimentally measured. The ultrasonic method is based on acoustoelasticity law by which the ultrasonic wave velocity could be connected to the material stress. By changing the frequency in which the ultrasonic transducers are working, the LCR waves are able to penetrate in various depths of the material in order to measure the sub-surface residual stresses. Hence, four main aspects are considered in this study: (I) stress evaluation of the DMW; (II) sub-surface stress measurement; (III) stress evaluation of longitudinal weld and (IV) stress measurement in cross weld. It is demonstrated that the residual stresses of the DMW pressure vessel could be comprehensively evaluated by using the LCR method.     

Numerical and Experimental Study of Crack Depth Measurement in Concrete Using Diffuse Ultrasound

This paper presents a combined numerical and experimental study on the diffuse ultrasonic measurement technique for determining the depth of surface breaking cracks in concrete. A finite element (FE) model for the dissipative diffusion in a two-dimensional domain with a surface breaking crack is developed using a commercial FE package; for this purpose, the dissipation term is eliminated by a simple change of variables. Three concrete blocks with a crack depth between 25.4 mm to 101.6 mm are prepared. Diffuse ultrasonic measurements are performed on uncracked and cracked concrete blocks, from which the diffuse energy evolution curves are obtained. The basic material parameters of the hardened concrete, i.e. the diffusivity and dissipation, are retrieved, which are needed for the numerical simulations. The crack depths are then determined by comparing the experimental and numerical arrival times of the average diffuse ultrasonic energy. Various geometrical configurations that arise in real-world concrete structures are simulated including an inclined crack, a partially closed crack, two parallel cracks, and a crack with an underlying reinforcement bar. The objective is to investigate the possible limitations of the diffuse ultrasonic measurement technique when implemented in real concrete structures. Finally, it is shown that the time of flight (TOF) of the average diffuse ultrasonic energy constitutes the theoretical basis of the present diffuse ultrasonic measurement of macroscopic cracks and therefore the present diffuse ultrasonic method forms another kind of TOF technique.     

蓝宝石光纤高温测量技术进展

温度是表征物体状态的参数之一,在科学研究和工程应用中具有重要的理论意义和价值。在氧化、高温、腐蚀、电磁干扰等恶劣环境下,温度的准确测量一直是难题。传感器材料是进行温度测量的基础。蓝宝石单晶光纤具有物理化学性能稳定、熔点高、机械性能强等优点,是进行高温测试的一种首选材料。本文介绍了利用蓝宝石单晶光纤进行温度测量的几种方法,即蓝宝石光纤辐射高温测试技术、蓝宝石光纤光栅高温测试技术、蓝宝石光纤珐珀高温测试技术、蓝宝石超声波导高温测试技术的原理、现状、优缺点及发展趋势,并进行了比较,为蓝宝石光纤温度测量应用奠定基础。     

Nondestructive Evaluation of Welding Residual Stresses in Dissimilar Welded Pipes

This paper investigates the nondestructive capability of ultrasonic waves in residual stress evaluation of dissimilar welded pipes. Longitudinal critically refracted (L _CR ) waves are employed to measure the residual stresses in a pipe-pipe joint of stainless steel 304 and carbon steel A106. Measuring the acoustoelastic constant is usually accomplished through the tensile test which needs cutting the tested material to extract tensile test specimens. However, cutting the tested pipe to complement the nondestructive ultrasonic measurement was not considered here. Instead, a dissimilar welded plate with the same welding specification, joint geometry, thickness and the same dissimilar materials is used to extract tensile test samples. The measured acoustoelastic constant of the plate along with the measured time of flight of the L _CR wave on the pipe, are utilized for ultrasonic stress measurement. A finite element model of welding process validated by hole-drilling method is used to verify the ultrasonic results. The results show good agreement between finite element and ultrasonic measurements in the pipe measured without any destructive process.