复杂应力状态下超细晶材料的塑性

本工作通过三维非接触全场应变测量系统(DIC)和有限元模拟(FEM)对比研究了超细晶铜和粗晶铜在拉伸过程中颈缩处的应变和应力分布,比较了在颈缩后的复杂应力状态下超细晶铜和粗晶铜延伸率的差异,实验发现虽然超细晶铜与粗晶铜在工程应力-应变曲线上的断裂延伸率相差较大,但两者颈缩区域的延伸率相当。有限元模拟揭示颈缩区域为三向应力状态,实验设计的缺口试样进一步验证复杂应力状态下超细晶材料的塑性变形能力与粗晶材料相当。复杂应力状态下,超细晶铜内部更多的滑移系被激发,使得超细晶铜的塑性变形能力与粗晶铜相当。     

Stresses and strains in a rectilinear region of a cryoturbogenerator field winding

A theoretical study is described of stresses and strains in a rectilinear region of a cryoturbogenerator field winding under the thermomechanical and ponderomotive forces and those forces encounterd during the winding assembly. Windings with a number of transverse cooling channels are considered. The model permits us to choose the winding parameters which will ensure the required cooling conditions and to calculate the strength of the winding.     

金属基体上硬质薄膜内应力的释放测量法

提出了一种基于Stoney公式测量金属基体上硬质薄膜内应力的应力释放法，并研究了不同基底温度对磁控溅射TiN薄膜内应力的影响。     

N80钢管残余应力的测试与分析

采用全释放法测试N80钢管的残余应力，结果发现：无论是直管还是发生变形的弯管在它们的同一部位，其内表面与外表面的残余应力是不均匀的，而且沿内圆周或是外圆周其残余应力的分布也不均匀。得出高的残余应力加上分布的不均匀性是钢管发生弯曲变形的主要原因之一。     

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。     

生物软组织内部压缩应变的测量与分析

通过不同边界条件的离体组织压缩实验,对非均匀组织内部的应变进行测量,并以线弹性有限尺度组织压缩模型的理论应变曲线为参照进行比较．结果表明,组织内部应变分布主要由边界条件和组织的生理结构决定,对称的压缩条件和丰富的纹理结构可以获得更好的应变估计效果．     

A Method of Measuring Through‐Thickness Internal Strains and Stresses in Graphite

Abstract: Currently, the structural integrity of the nuclear graphite reactor components is evaluated using irradiated material properties data obtained from test reactors. These data are applied to numerical or mathematical models to assess the integrity of the graphite components. On the other hand, there is a need to measure internal strains and stresses in reactor core graphite and to explore the potential for in‐situ measurement. The deep hole drilling (DHD) technique is a semi‐destructive method for measurement of the through thickness residual strains or stresses. Previously the technique has been applied successfully to metallic and composite materials. In this paper, the method for internal strain and stress measurement in polygranular graphite is examined particularly when a significant volume fraction of porosity is present. Finite element simulation shows that the method can be used to measure internal stresses generated by a thermal gradient. On the basis of this a series of experiments have been conducted using Pile Grade ‘A’ (PGA) and PG25 filter graphite; with the latter being a surrogate for service exposed material. Tests were conducted to illustrate that the bulk mechanical response was linear elastic for both graphites and elastic moduli were measured. The DHD method was then used to determine internal strain and stress profiles through the materials. The results were compared with the strain data obtained from strain gauges bonded to the samples. Overall, there was an excellent agreement between the measured through‐thickness internal strains and stresses and the surface strains and stresses determined from the applied loading.     

Making Resistive Components of Measurement Circuits with Preset Properties

Methods are described for making thermally compensated resistive components as well as ones with preset values of resistance and temperature coefficient of resistance on the basis of combinations of thin-film resistors with films made of various materials.     

小孔释放法测纤维增强复合材料残余应力的释放系数

介绍了小孔释放法测量残余应力的原理,给出释放应变与残余应力之间的关系公式.针对纤维增强复合材料的属性特点,应用坐标系转换原理推导出通孔法测量复合材料残余应力时的应力释放系数公式.以碳纤维增强复合材料为例计算其残余应力测试过程中的释放系数,由此得到释放应变,并将计算结果与同一预应力下用有限元法计算的结果进行了对比.     

Measurement of Residual Stresses with Optical Techniques

Abstract:  The goal of this work was the development of other experimental techniques to measure residual stresses, as an alternative to the hole-drilling method with strain gauges. The proposed experimental techniques are based on the use of Moiré interferometry and in-plane electronic speckle pattern interferometry (ESPI). Both are field techniques allowing the assessment of in-plane displacements without contact and high resolution. Grating replication techniques were developed to record high-quality diffraction gratings onto the specimen's surfaces. An optical set-up of laser interferometry was developed to generate the master grating (virtual). An in-plane ESPI set-up was also designed and implemented to measure displacements in one direction. The stress relaxation was promoted by the blind hole-drilling and the obtained fringe patterns (Moiré and speckle) were video-recorded. Image processing techniques were applied to assess the in-plane strain field. A finite-element code ( ansys ®) was used to simulate the stress relaxation process, whose values were compared with the experimental data, and to calculate the hole-drilling calibration constants.     

精密电阻器热阻分析与测定方法研究

提出了一种锰铜丝精密电阻的热阻测定新方法,推导出适用于锰铜丝精密电阻的热阻计算公式。通过建立电阻温度特性及负载效应的测试平台,解释了测试得到的锰铜丝零负载效应点现象。实验得到的零负载效应温度点重复性测试结果均达到10~(-8)量级。将已知零负载效应点的锰铜丝精密电阻作为参考电阻,可以对其他电阻进行额定功率下负载效应的准确测试。     

远程测量系统中被测零件的重建

坐标测量机（CMM）与测量者分离进行远程测量时,掌握被测零件的位置与形状信息具有重要意义。提出一种对被测零件进行三维重建和定位的方法,根据双目视觉原理,利用从测量现场获取被测零件的图像及机械零件的规则性较强采用体积表示方法进行被测零件的三维重建,详细阐述了准确识别组成被测零件基本几何体的方法,展示了应用该系统三维重建和定位示例。     

玻璃纤维-铝合金层板(GLARE)的残余应力

对确定纤维金属层板残余应力的几种方法的基本原理进行了介绍，用Ｘ光衍射法，解析法和腐蚀去层法确定了玻璃纤维－铝合金层板（ＧＬＡＲＥ）的残余应力，对以上几种测试方法的优缺点进行了分析，提出了确定纤维金属层板残余应力的建议。     

Comparison Between Using Longitudinal and Shear Waves in Ultrasonic Stress Measurement to Investigate the Effect of Post-Weld Heat-Treatment on Welding Residual Stresses

Fusion welding is a joining process widely used in the industry. However, undesired residual stresses are produced once the welding process is completed. Post-weld heat-treatment (PWHT) is extensively employed in order to relieve the welding residual stresses. In this study, effect of PWHT time and temperature on the residual stresses of a ferritic stainless steel is investigated. Residual stress distributions in eight welded specimens were measured by using an ultrasonic method. Ultrasonic stress measurement is a nondestructive method based on acoustoelasticity law, which correlates mechanical stresses with velocity of an ultrasonic wave propagating within the subject material. The ultrasonic wave employed could be longitudinal or shear wave produced by the longitudinal (normal) or transverse (shear) transducers, respectively. Ultrasonic stress measurements based on longitudinal waves use longitudinal critically refracted (L_CR) waves in this direction, while shear wave methods use an ultrasonic birefringence phenomenon. The results show that the effect of PWHT can be successfully inferred by both longitudinal and shear wave methods, but the former is found to be more sensitive to stress variation. Furthermore, the distribution of subsurface residual stresses is found to be more distinguishable when the L_CR method is employed.     

Application of Deep Hole Drilling to the Measurement and Analysis of Residual Stresses in Steel Shrink‐Fitted Assemblies

Abstract: Residual stress measurement of shrink‐fitted assemblies was achieved through finite element simulations and experiments using the deep hole drilling technique. Shrink‐fitted assemblies using stainless steel and cast iron were manufactured and residual stresses measured using a combination of deep hole and centre hole drilling. The results from the finite element simulations demonstrated that modifications to the deep hole drilling method were required to account for plastic relaxation during the measurement process. This was verified through the experimental measurements. The results from both the stainless steel and cast iron assemblies provided a clear demonstration that the final residual stress state was a consequence of the machining and assembly of the components.     

Determination of Residual Stresses in Electro-Spark Deposited Coatings

We propose a method of determining axial residual stresses in prismatic coated rods of rectangular cross section, which provides a means to study the stress state in both homogeneous and inhomogeneous coatings.     

压电层合板层间应力新研究

综述了压电层合板数值分析方面的一些进展，在一般层合板理论的基础上提出一个多层压电层合板单元，依据线性压电理论建立压电层合板单元的杂交元模型，利用三维8节点块状单元建立多层压电层合板的有限元列式，解决了压电层合板层间应力的连续性。     

Thermal Residual Stresses in Multilayered Coatings

The mechanical integrity and reliability of coated devices are strongly affected by the residual stresses in thin films and coatings. However, due to the metallurgical complexity of materials, it is rather difficult to obtain a closed-form solution of residual stresses within multilayered coatings (e.g. functionally graded coatings, FGCs). In this paper, an analytical model is developed to predict the distribution of residual stresses within multilayered coatings. The advantage of this model is that the solution of residual stresses is independent of the number of layers. Specific results are obtained by calculating elastic thermal stresses in ZrO2/NiCoCrAIY FGCs, which consist of different material layers. Furthermore, the residual stress distribution near the edges and the stress-induced failure modes of coating are also analyzed. The topics discussed provide some insights into the development of a methodology for designing fail-safe coating systems.     

Thermoelastic Determination of Individual Stresses in a Diametrally Loaded Disk

Abstract: In a cyclically loaded structure which experiences adiabatic and reversible conditions, the measured change in temperature is associated with the change in the stresses. For proportional loading and isotropy, the technique measures information on the sum of the principal stresses. As engineering analyses frequently necessitate knowing the individual components of stress, supplementary experimental methods or information is sometimes required to ‘separate the stresses’. This need is circumvented here in that individual stresses are evaluated throughout a loaded disk without additional measured data by hybridising the TSA information with an Airy stress function and some known boundary conditions. Although demonstrated here to a circular aluminium disk under diametral compression, the approach is applicable to more complicated shapes, under more complex loadings and inverse problems. The technique does not pre‐suppose knowing the details. While TSA information has been displayed previously for a loaded disk, the authors are unaware of the stresses being thermoelastically separated for this case.