共查询到20条相似文献,搜索用时 31 毫秒
1.
A. Koshti 《Experimental Mechanics》1998,38(4):270-277
An ultrasonic pulse/echo technique is used to measure preload in bolts used in structural joints. In this paper, the same
instrument is used in a different way to measure change in the ultrasonic measurements due to bending in the bolts. A theory
that explains the ultrasonic measurements is developed. The bending loads result in a rotation and a translation of the ultrasonic
pulse reflecting face. It also creates a stress gradient in the bolt. This results in a phase variation (or gradient) in the
received ultrasonic beam across the face of the transducer. It also results in a physical shift in the received beam relative
to the ultrasonic transducer. The phase gradient and the shift in the beam results in change in the pulse travel time. A number
of experiments were performed on the bolt to study the effect of the bending on the ultrasonic measurements. The experiments
and the theory validate a sensitive new method for measuring the bending loads in the bolts. 相似文献
2.
双柱单锥型液-液旋流管内流场的激光诊断 总被引:2,自引:0,他引:2
应用激光测速仪,对一种双柱单锥型液 液旋流管内的流动结构,进行了全场范围内的多工况流动诊断研究.揭示出其切向速度由内旋流区和外旋流区构成,其中内旋流区中的速度分布符合准强制涡关系,外旋流区中的速度分布符合准自由涡关系;轴向速度由上行流动区和下行流动区构成,两者之间在直管段以零速点作分界,在锥体段则以零速区作过渡并伴随有一定的回流出现,且该过渡区或回流区的大小随锥体截面的收缩而减小,直到进入直管段后消失;各湍流量的分布以管芯处最大向外逐渐减小,沿轴向是直管段中的湍流度大于锥体段中的湍流度,而且湍流度在旋流管内具有各向异性的特性. 相似文献
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化学跑合剂对跑合效果的影响 总被引:1,自引:2,他引:1
在BJ52A胶合试验机、JP-BD1500型接触疲劳试验机和CL-100齿轮试验机上考察了化学跑合剂的作用,并就其机理进行了探讨。结果表明:采用化学跑合剂跑合后,表面粗糙度明显降低;表面接触面积增大,可以实现1次满载快速跑合;与采用含磨料的跑合方法比较,化学跑合剂可以明显提高表面接触精度,减少裂纹源的发生和发展,使表面承载能力明显提高。当齿轮加工精度较低或高速、重载齿轮的硬齿面精加工存在困难时,可 相似文献
6.
Fluid-solid coupling typically plays a negligible role in confined converging shocks in gases because of the rigidity of the
surrounding material and large acoustic impedance mismatch of wave propagation between it and the gas. However, this is not
true for converging shocks in a liquid. In the latter case, the coupling can not be ignored and properties of the surrounding
material have a direct influence on wave propagation. In shock focusing in water confined in a solid convergent geometry,
the shock in the liquid transmits to the solid and both transverse and longitudinal waves propagate in the solid. Shock focusing
in water for three types of confinement materials has been studied experimentally with schlieren and photoelasticity optical
techniques. A projectile from a gas gun impacts a liquid contained in a solid convergent geometry. The impact produces a shock
wave in water that develops even higher pressure when focused in the vicinity of the apex. Depending on the confining material,
the shock speed in the water can be slower, faster, or in between wave speeds in the solid. For solid materials with higher
wave speeds than the shock in water, regions in the water is put in tension and cavitation occurs. Materials with slower wave
speeds will deform easily. 相似文献
7.
In the wake of a rectangular cylinder measurements of mean velocity and some turbulent stresses are carried out in a straight duct and in a curved duct. The difference in turbulent quantities in the wake of the body, in the straight duct an in the curved duct is significant especially in the downstream side of the wake. The shear stresses are more sensitive to curvature than the normal stresses. 相似文献
8.
有效集法在数学规划加权残值法中的应用 总被引:2,自引:0,他引:2
本文研究有效集法在数学规划加权残值法求解微分方程问题中的应用。从理论上和实际应用方面 阐明,对于数学规划加权残值法和线性规划问题,有效集法比常用的单纯形法更简便、易程序化、计算速度更快,因此更适用于数学规划加权残值法求解微分方程问题。 相似文献
9.
Ahmed Ezzat 《Experimental Mechanics》1961,1(7):10-15
Tanks and pipes vibrating in flexure and filled with various materials have been a problem in power plants, factories, airplanes and tankers. The present experimental investigation was carried out on a pipe vibrating in flexure and filled with various materials, both liquid and solid. The tests showed that, in general, filling a pipe in flexure with any material, liquid or solid, increases its damping characteristics. An increase in the kinematic viscosity of the filling liquid, or a decrease in the size of the particles of the filling solid, will result in a corresponding increase in the equivalent damping factor of the system. 相似文献
10.
以甲烷/空气混合物为研究对象,开展了连通容器气体泄爆影响因素的实验研究。结果表明:连通容器泄爆片泄爆时,随着破膜压力和量纲一泄压比的减小,大、小球容器的最大泄爆压力均增大;在等量纲一泄压比条件下,随着连接管道长度的增加,传爆容器的最大泄爆压力增大。连通容器无膜泄爆时,大球点火条件下,无论管长如何,起爆容器和传爆容器均比单个容器最大泄爆压力大。小球点火条件下,当管道长度为0.45 m时,起爆容器和传爆容器的最大泄爆压力均小于单个容器。连通容器无膜泄爆且量纲一泄压比相同时,当管道长度为0.45 m时,大、小容器内的最大泄爆压力基本相等;当管道长度为2.45 m时,大容器点火时,传爆容器最大爆炸压力大于起爆容器,但小容器点火时,起爆容器最大泄爆压力大于传爆容器;当管道长度为4.45和6.45 m时,传爆容器最大泄爆压力均大于起爆容器。 相似文献
11.
Instabilities in viscoelastic flows 总被引:5,自引:0,他引:5
R. G. Larson 《Rheologica Acta》1992,31(3):213-263
Viscoelastic instabilities are of practical importance, and are the subject of growing interest. Reviewed here are the fresh developments as well as earlier work in this area, organized into the following categories: instabilities in Taylor-Couette flows, instabilities in cone-and-plate and plate-and-plate flows, instabilities in parallel shear flows, extrudate distortions and fracture, instabilities in shear flows with interfaces, instabilities in extensional flows, instabilities in multidimensional flows, and thermohydrodynamic instabilities. Emphasized in the review are comparisons between theory and experiment and suggested directions for future work. 相似文献
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Remarks on the Behavior of Simple Directionally Reinforced Incompressible Nonlinearly Elastic Solids
The effect of directional reinforcing in generating qualitative changes in the mechanical response of a base neo-Hookean material
is examined in the context of homogenous deformation. Single axis reinforcing giving transverse isotropy is the major focus,
in which case a standard reinforcing model is characterized by a single constitutive reinforcing parameter. Various qualitative
changes in the mechanical response ensue as the reinforcing parameter increases from the zero-value associated with neo-Hookean
response. These include (in order): the existence of a limiting contractive stretch for transverse-axis tensile load; loss
of monotonicity in off-axis simple shear; loss of monotonicity in on-axis compression; loss of positivity in the stress-shear
product in off-axis simple shear; and loss of monotonicity for plane strain in on-axis compression. The qualitative changes
in the simple shear response are associated with stretch relaxation in the reinforcing direction due to finite rotation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
《中国颗粒学报》2006,4(3):103-103
This special issue of China PARTICUOLOGY is dedicated to Professors Yong Jin and Zhiqing Yu of Tsinghua University, China, to celebrate over five decades of their careers in chemical engineering research and education. Prof. Jin graduated in 1959 from Ural Polytechnic College in Svivdelovsk in the former USSR and then completed his post-graduate studies in Tianjin University in China in 1960. Thereafter, he taught at the Chinese University of Science and Technology for 13 years before joining Tsinghua University in 1973. Prof. Yu graduated in 1956 from Tianjin University in China and joined Tsinghua University thereafter. Between 1957 and 1959, Prof. Yu undertook more studies in Moscow Mendeleev Institute of Chemical Technology in the former USSR. During the 1970s, Professors Jin and Yu jointly created the Reaction Engineering Program in the Department of Chemical Engineering at Tsinghua University, which later became one of the largest fluidization research groups in the world, known as FLOTU - Fluidization Laboratory of Tsinghua University. 相似文献
15.
C. A. Sciammarella A. Boccaccio L. Lamberti C. Pappalettere A. Rizzo M. A. Signore D. Valerini 《Experimental Mechanics》2013,53(6):977-987
Thin film technology is an area of great importance in current applications of opto-electronics, electronics, MEMS and computer technology. A critical issue in thin film technology is residual stresses that arise when the coating is deposited onto a substrate. Residual stresses can be very large in magnitude and have detrimental effects on the role that the thin film must play. To save development time on coating deposition processes it is important to perform accurate residual stresses measurements in situ in real time where the deposition is made. A novel optical set up is developed in this study to measure deflections and residual stresses generated in coated specimens that can be applied directly in the reactor utilized in the deposition process. Experimental results are in good agreement with other measurements carried out independently and other data reported in literature for thin films like those tested in the experiments. 相似文献
16.
The present study investigated the effects of four parallel rib arrangements on heat/mass transfer and pressure drop characteristics
in rotating two-pass ducts. The experiments of mass transfer and pressure measurement are performed to obtain heat transfer
distributions and friction losses. The highest averaged heat (mass) transfer and friction loss in each region appeared in
the turning region in the stationary cases, but appeared in the upstream region of the second pass in the rotating cases.
Among the tested rib arrangements, the averaged heat (mass) transfer and the friction factor in the second pass in the stationary
ducts were high in the cases with the NN- and PP-type ribs; however, in the rotating ducts, they were high in the cases with
the NN- and PN-type ribs. The thermal performance in the four different rib arrangements was almost the same. 相似文献
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盐岩储库区地面沉降预测与控制研究现状与展望 总被引:2,自引:0,他引:2
利用盐岩地层建设地下油气储库群已成为各国发展能源储备的重要方向,然而关于储库区地面沉降的研究至今仍处于探索阶段。由于地面沉降所造成的重大事故屡见不鲜,因此有必要集中力量研究盐岩库区地面沉降问题,为我国盐岩储库群的建设提供可靠的理论依据。本文主要从以下3个方面总结了近几十年来国内外学者在盐岩储库区地面沉降预测方面所做出的努力与成绩: (1)现场监测——法国、德国、美国先后建立了现场监测网络,获得了大量的长期监测数据; (2)理论计算——我国学者于20世纪90年代末将随机介质理论引入到盐矿水溶开采地面沉降预测中,从而为储库区地面沉降预测提供了新的理论基础; (3)数值模拟——欧洲学者利用FLAC2D 程序对盐岩储库区的地面稳定性进行了数值模拟,而我国学者则利用在新概率积分法的基础上建立起的预测模型成功进行了沉降预测模拟。此外,为了有效地控制库区地面变形,预留矿柱式水溶开采法在国外众多盐岩地下储库群建设中得以广泛应用。本文最后提出在后续研究中将重点着眼于地表变形随时间的发展过程,并对现有理论模型进行适当的修正以及利用现场实测数据进一步完善预测所需参数的选取方法,从而使预测结果更为准确可靠。 相似文献
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Salvatore Lopez 《Nonlinear dynamics》2012,69(3):705-720
In the present paper, we propose a representation of the discrete motion equations in structural nonlinear dynamics to obtain an improvement in the stability of time numerical integrations. A geometrically nonlinear total Lagrangian formulation for three-dimensional beam elements in the hypotheses of large rotations and small strains is presented. In this formulation, slopes are used instead of rotation parameters to compute the nonlinear representations of the strain measures in the inertial frame of reference. Such representations of the internal strains??rotations compatibility are then imposed in their time derivatives version. The results, related to Newmark approximations for the variations in the displacement and velocity vectors, show a significant increase in the range of stability of the time integration process and a reduction in the number of Newton iterations required in the time integration steps. The numerical tests, furthermore, show that the variation in the total energy in the time steps has bounded oscillations about the zero value. 相似文献
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