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1.
The development of torque-induced shear stresses in the presence of slippage, and the residual stresses remaining after torque-induced
slippage, are analysed using frozen-stress photoelasticity. Shaft/ring specimens were manufactured from epoxy photoelastic
material and were assembled by shrink-fitting prior to being loaded under various regimes, notably the application and release
of a torque load. The interface pressure was predicted from Lamé thick cylinder theory, and was also estimated by fitting
the Lamé model to the measured stress distributions. The distributions of interface shear stress were calculated from averaged
photoelastic data, and compared with the results of a dislocation-based model and with a nonlinear finite element model. For
a torque loaded specimen there was good agreement between experimental, theoretical and FE data. Another specimen was loaded
in torque then unloaded, with results showing the expected features of slippage and residual stress.
相似文献
J. D. BookerEmail: |
2.
钻孔法测量残余应力过程中钻孔附加应变 总被引:3,自引:0,他引:3
本文叙述了钻孔法测量残余应力过程中的附加应变.研究应力水平对附加应变的影响是在单向应力条件下进行的,结果表明,钻孔条件、材料状态以及残余应力达到一定值时,附加应变为零. 相似文献
3.
本文应用弹塑性理论研究了被测试样的屈服强度、应力场对钻孔法测量残余应力过程中钻孔附加应变的影响,使用简化的理论模型推导了低速旋转钻头钻孔产生附加应变的一般表达式.结果表明钻孔引入的附加应变与被测试样的原始残余应力状态有关,随应力水平增加而增大,在压应力减小到某一临界值σ时,钻孔附加应变为零。在 Ly12铝合金上的实验测量结果与理论结果一致。 相似文献
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高压气瓶工艺残余应力测试和分析 总被引:3,自引:0,他引:3
用X射线及磁记忆两种方法对压缩天然气的高压气瓶应力状态进行了系统分析,对一个气瓶整体制造工艺中的残余应力变化用X射线法进行了跟踪检测。考察了气瓶锻造后、淬火后及回火后外表面的残余应力状况,对相同测点进行了三次应力测试。为准确找到测点位置并寻求两种方法之间关系,在每次应力测试之前,均用金属磁记忆方法进行了先期检测。结果表明:锻造后应力水平不高,但磁记忆曲线有小幅波动,显示应力不均匀;淬火后表面具有较大压应力,最大达到0.86σS,且磁场亦有较大变化,个别点有明显应力集中;回火处理有效地消除了淬火残余应力,最大值小于0.17σS,应力均匀化,磁记忆曲线几乎无波动,效果良好。而从定量角度,残余应力和磁记忆两者之间没有明确的对应关系。对于磁记忆所显示的磁场强度变化处,用X射线法进行残余应力测试,结果并没有显示出较高的应力水平。说明两种方法不可互相替代,但以其各自的特点和优势可做互相补充。 相似文献
6.
本文讨论了抽油杆通过感应线圈和水冷装置时的温度场和由温度场引起的相变。在有限元计算中,通过与实验数据对比,认为考虑温度对弹性模量有影响的计算模型更合理,并用此模型计算了由温度和相变共同作用的弹塑性应力场,及最终的残余应力。结果表明淬火层超过一定厚度后,残余应力分布的合理性降低;淬火前抽油杆的强度与残余应力的大小关系较弱。 相似文献
7.
Bayly PV Massouros PG Christoforou E Sabet A Genin GM 《Journal of the mechanics and physics of solids》2008,56(5):2036-2049
A magnetic resonance measurement technique was developed to characterize the transient mechanical response of a gel cylinder subjected to angular acceleration. The technique employs tagged magnetic resonance imaging (MRI) synchronized to periodic impact excitation of a bulk specimen. The tagged MRI sequence provides, non-invasively, an array of distributed displacement and strain measurements with high spatial (here, 4 mm) and temporal (6 ms) resolution. The technique was validated on a cylindrical gelatin sample. Measured dynamic strain fields were compared to strain fields predicted using (1) a closed-form solution and (2) finite element simulation of shear waves in a three-parameter “standard” linear viscoelastic cylinder subjected to similar initial and boundary conditions. Material parameters used in the analyses were estimated from measurements made on the gelatin in a standard rheometer. The experimental results support the utility of tagged MRI for dynamic, non-invasive assays such as measurement of shear waves in brain tissue during angular acceleration of the skull. When applied in the inverse sense, the technique has potential for characterization of the mechanical behavior of gel biomaterials. 相似文献
8.
H. Saraf K. T. Ramesh A. M. Lennon A. C. Merkle J. C. Roberts 《Experimental Mechanics》2007,47(3):439-449
Traditionally, Kolsky bars are used to study the dynamic response of hard materials in uniaxial compression, tension or torsion.
We present modifications to the technique that allow loading of a soft tissue specimen in (a) hydrostatic compression and
(b) simple shear. The first modification is designed to determine the pressure vs. volume behavior of each material, and thence
to extract a measure of the dynamic compressibility or equivalently of the bulk modulus. The second modification is designed
to develop the shear stress versus shear strain behavior for a near-simple shear experiment. The critically important questions
of the proper acquisition of human tissue samples and protocols for appropriate experimentation have also been addressed.
The experimental techniques and the results are discussed in detail and the results compared to finite element simulations.
We present examples of the dynamic response of typical tissue simulants as well as human liver and stomach tissues. 相似文献
9.
This paper presents results on the rheological behaviour of suspensions of two kinds of TiO2 particles in two different polymer solutions. The particles differ in their hydrophilic or hydrophobic properties. The dispersing
media are a solution of high molecular weight polyisobutylene in decalin and a solution of a low molecular weight polybutene
in decalin. The concentrations of polymer are adjusted in order to get the same zero shear viscosity. The shear viscosity
measurements display an apparent yield stress in some cases. The existence and the values of the yield stress depend on the
volume fraction of solid particles and on the type of particles. The evolution of the intrinsic viscosity and of the maximum
packing fraction vs the shear rate is interpreted in terms of evolution of the size and of the shape of aggregates of particles
under shear. The effect of temperature on the development of the yield stress is also discussed. The results are completed
by microscopic observations. 相似文献
10.
超声纯横波法测试45#钢的内部应力 总被引:1,自引:1,他引:1
声各向同性的金属材料在应力作用下,材料表现出声各向异性,这是用声弹性法分析材料内部应力的基础。本文用垂直于应力方向传播的超声纯横波对45#钢进行测试,测试时横波的偏振化方向分别平行和垂直于应力方向。实验结果表明:材料在拉、压应力作用下,相互正交的两超声纯横波的声速都发生了变化,且声各向异性因子与应力成线性关系。利用此关系可测试材料内部应力,提供了一种无损测试材料内部应力的方法,另外本实验方法也可以对材料内部残余应力进行评估。实验中利用回振法测量声速,可测量声速的微小变化,精度高。 相似文献
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Ang Liu Guanghui Tian Qingzhao Zhang Wenli Lin Jingcai Jiang 《Comptes Rendus Mecanique》2018,346(12):1179-1191
The stress relaxation characteristic of rock mass is an important aspect of rheology and has important practical significance for rock engineering. In order to investigate the relaxation characteristic of rock joints with different slope ratios and normal stresses, a series of shear stress relaxation tests were conducted on artifical rock joints poured by cement mortar. Test results show that the relaxation curves can be divided into three stages, i.e. instantaneous relaxation stage, attenuation relaxation stage, and stable relaxation stage. Furthermore, the nonlinear Maxwell relaxation equation was obtained by using the relation between the viscosity coefficient and time, and the theoretical curves based on the empirical equation agreed well with the test results. Moreover, the change law of the initial viscosity coefficient was investigated. Accordingly, a stress relaxation method, termed as relaxation stress peak method, was proposed to determine the long-term strength of rock joints. 相似文献
13.
Shear Rate and Permeability in Water Flooding 总被引:1,自引:0,他引:1
Water breakthrough during oil recovery can be inhibited by the use of novel shear-induced structure additives. These affect
the shear rate experienced by fluid inside the rock matrix. We relate this to the permeability for the purpose of applying
these novel non-Newtonian materials which thicken viscosity only in the shear range associated with the permeability of the
reservoir while maintaining base fluid properties outside this range. 相似文献
14.
A theory is presented for the onset of shear thickening in colloidal suspensions of particles, stabilized by an electrostatic
repulsion. Based on an activation model, a critical shear stress can be derived for the onset of shear thickening in dense
suspensions for a constant potential and a constant charge approach of the spheres. Unlike previous models, the total interaction
potential is taken into account (sum of attraction and repulsion). The critical shear stress is related to the maximum of
the total interaction potential scaled by the free volume per particle. A comparison with experimental investigations shows
the applicability of the theory. 相似文献
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The present paper is concerned with the stresses generated in a capillary-porous wall saturated from the bottom and dried naturally on its side planes. The upper cross-section of the wall is totally isolated and no heat and moisture transfer occurs through it, while the bottom one has an a priori determined temperature and moisture content. The vertical planes of the wall are surrounded by air having different temperatures and moisture contents on the left and the right sides. The problem is solved numerically based on a mechanistic model of drying earlier developed by the authors. The distributions of temperature, moisture content, and the drying induced stresses are determined. The variation of temperature on the wall left and right surfaces is analysed dependent on the surroundings temperature. The influence of boundary conditions on the stress distribution in the wall is discussed. 相似文献
17.
Shear banding occurs in the flow of complex fluids: various types of shear thinning and shear thickening micelle solutions
and liquid crystals. In order to cope with the strongly inhomogeneous interface between the bands, constitutive models used
in standard rheology must be supplemented by non-local terms. This leads rather generally to non-linear partial differential
equations of the reaction-diffusion type. We use this formalism in order to explain some observed experimental features and
as a guide for future research in this field.
Received: 17 May 1999/Accepted: 3 August 1999 相似文献
18.
In this paper, we show that a three-phase elliptic inclusion under uniform remote stress and eigenstrain in anti-plane shear
admits an internal uniform stress field provided that the interfaces are two confocal ellipses. The exact closed-form solution
is used to quantify the effect of the interphase layer on the residual stresses within the inclusion and the dependency of
this effect on the aspect ratio of the elliptic inclusion.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
N. Hu 《Journal of the mechanics and physics of solids》2004,52(3):499-531
In this paper, the phenomenon of strain localization, i.e., shear banding, in densely distributed metallic assemblies has been studied. A discrete element methodology for analyzing metallic granular materials has been put forward. In this numerical model, elastoplastic contact, as well as friction, rolling resistance and cohesion between spheres, are explicitly taken into account. The calculations reveal that the shear banding mechanism in dense assemblies can be thought as an instability triggered by initial imperfections. Within a band, the motion, deformation and rearrangement of spheres soften the resistance of the aggregate, as these mechanisms create additional geometric imperfections. Additionally, the simulations showed that the shear-band width does not change conclusively with the friction, rolling resistance and plasticity parameters. However, cohesive strength, even in small amounts, drastically increased the shear-band width. Finally, the shear-band thickness and inclination angles are strongly dependent on the degree of initial imperfection. Whereas for a perfect assembly the shear band inclinations were consistently around 60°, more heterogeneous assemblies lead to shear band angles closer to the continuum mechanics solution, which is 45°. This was found to be in agreement with recent experimental observations. 相似文献
20.
Full-field quantitative strain maps of phase transformation and plasticity in Nitinol under large shear-dominated deformation
are presented. To achieve a shear-dominated deformation mode with relatively uniform stresses and strains, a shear compression
specimen (SCS) geometry was utilized. Shear deformation appears to impede the development of the strain localization during
phase transformation that is seen in uniaxial testing. The shear-dominant deformation of Nitinol in the plastic regime exhibits
low hardening and results in the development of significant strain inhomogeneity. 相似文献