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Shu-Chu Ren Nelson N. Hsu Donald G. Eitzen 《Journal of research of the National Institute of Standards and Technology》2002,107(5):445-473
Pulsed ultrasonic techniques can be and have been used to examine the interface conditions of a bonded structure. To provide a theoretical basis for such testing techniques we model the structure as a layer on top of a half-space, both of different elastic properties, with various interface bonding conditions. The exact dynamic Green’s tensor for such a structure is explicitly derived from the three-dimensional equations of motion. The final solution is a series. Each term of the series corresponds to a successive arrival of a “generalized ray” and each is a definite line integral along a fixed path which can be easily computed numerically. Willis’ method is used in the derivation. A new scheme of automatic generation of the arrivals and ray paths using combinatorial analysis, along with the summation of the corresponding products of reflection coefficients is presented. A FORTRAN code is developed for computation of the Green’s tensor when both the source and the detector are located on the top surface. The Green’s tensor is then used to simulate displacements due to pulsed ultrasonic point sources of known time waveform. Results show that the interface bonding conditions have a great influence on the transient displacements. For example, when the interface bonding conditions vary, some of the first few head waves and regular reflected rays change polarities and amplitudes. This phenomenon can be used to infer the quality of the interface bond of materials in ultrasonic nondestructive evaluation. In addition the results are useful in the study of acoustic microscopy probes, coatings, and geo-exploration. 相似文献
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Rafael Gallego Lucia Comino Alberto Ruiz‐Cabello 《International journal for numerical methods in engineering》2006,66(12):1913-1933
In this paper, the material constant sensitivity boundary integral equation is presented, and its numerical solution proposed, based on boundary element techniques. The formulation deals with plane problems with general rectilinear anisotropy. Expressions for the computation of sensitivities for displacements, tractions, strains and stresses are derived, both for boundary and interior points. The sensitivities can be computed with respect to the bulk material properties or to the properties of part of the domain (inclusions, coatings, etc.). To assess the accuracy of the proposed approach, the computed results are compared to analytical ones derived from exact solutions obtained by complex potential theory, when possible, or finite difference derivatives otherwise. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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羊皮服装革的弯曲应力松弛性能及其与(手感)弹性之关系研究 总被引:3,自引:0,他引:3
本文研究了羊皮服装革的弯曲应力衰减性能。对应力衰减常数(αb)及其与羊皮服装革手感弹性的关系进行了讨论。结果表明:αb与革的手感弹性相关。αb值定量反映出革的手感弹性优劣。 相似文献
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简支深梁用和函数法的级数解答 总被引:3,自引:1,他引:2
引用和函数法求解弹性力学平面问题, 对简支深梁受三角形荷载作用时的应力进行了分析,同时给出了该问题的付立叶级数解答,该方法不仅将求解弹性力学的偏微分方程组解耦成非耦联的几个偏微分方程,而且其结果与传统的Airy应力函数得到的解答完全一致, 证明了该方法的正确性和适用性,该方法拓展了将经典的弹性力学解析法用于解决工程实际问题的空间。 相似文献
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在环氧-聚酰胺体系中分别加入“海岛结构”QS-1、聚硫橡胶、液体丁腈橡胶增韧改性,通过对固化物剪切强度、弯曲弹性模量及断裂强度的对比,“海岛结构”QS-1增韧综合性能较好. 相似文献
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In recent years, numerous analytical and experimental researches have been performed on the prediction of thermal stresses in mass concrete structures. However, due to the difficulty of the problem, limitations still exist for both analytical and experimental methods of measuring thermal stresses in mass concrete. In this research, a new experimental device measuring thermal stresses directly in a laboratory setting is developed. The equipment is located in a temperature chamber that follows the temperature history, which has been previously obtained from temperature distribution analyses. Thermal forces are measured continuously by two load cells in the device. The results show that the thermal stresses estimated by the newly developed device agree well with general stress variations in actual structures. 相似文献
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The promising potential of cloud computing and its convergence with technologies such as mobile computing, wireless networks, sensor technologies allows for creation and delivery of newer type of cloud services. In this paper, we advocate the use of cloud computing for the creation and management of cloud based health care services. As a representative case study, we design a Cloud Based Intelligent Health Care Service (CBIHCS) that performs real time monitoring of user health data for diagnosis of chronic illness such as diabetes. Advance body sensor components are utilized to gather user specific health data and store in cloud based storage repositories for subsequent analysis and classification. In addition, infrastructure level mechanisms are proposed to provide dynamic resource elasticity for CBIHCS. Experimental results demonstrate that classification accuracy of 92.59% is achieved with our prototype system and the predicted patterns of CPU usage offer better opportunities for adaptive resource elasticity. 相似文献