冻土的有限变形本构关系的实验研究

根据有限变形理论,给出了冻土三轴蠕变实验数据处理时所需Green应变和Kirchhoff应力的计算公式,并根据冻土三轴蠕变实验结果给出冻土的有限变形本构关系及其蠕变参数。通过对冻土的实验数据对比分析可知:在相同试验条件下,应变较小时,小应变ε1 和Green应变Ez的数值几乎相等,随着应变的增加,两种表征方式的计算结果差别越来越大,可见对于冻土如果不考虑试件变形前后长度的变化,计算得出的应变偏离实际变形情况较大,因此冻土材料的本构关系采用有限变形表征更确切。根据冻土的有限变形本构关系计算得到的冻结壁内侧最大径向位移更接近实测结果,因此冻结壁设计计算依据冻土的有限变形本构关系更为合理。对今后冻结工程的设计具有参考价值。     

冻土试验微机控制系统研究与应用

根据人工冻土力学性能的特点和试验规程,研究在同一台试验机上,设计出冻土单轴抗压强度试验和单轴蠕变强度试验的微机控制系统,系统设置了应力控制加载、应变控制加载和蠕变试验三个独立系统,并可以根据人为要求设定试验参数和微机控制试验;系统记录了全部试验数据,设置了查询、报表和图形等输出功能。文中介绍了冻土试验微机控制系统的关键技术,给出了冻土试验实例,对冻土力学性能的研究以及冻土试验机研制有较好的参考价值。     

Plane strain wave in an isotropic layer of a viscoelastic material

The velocity and the rate of decay of a strain wave in a layer of a viscoelastic material rigidly fixed on a solid foundation are determined. The wave structure (ratio of the longitudinal to the transverse displacement) and the profiles of these displacements are analyzed. Attenuation of waves in the first mode is found to be more significant than that in an infinite space. The most intense decay is observed at resonance frequencies. A strong effect of compressibility of the medium on wave parameters is revealed. Conditions at which such a system operates as a waveguide are found. For a loss tangent higher than 0.13 (for an incompressible medium), the character of the dispersion dependence is observed to change drastically: the wave velocity decreases with decreasing frequency. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 3, pp. 104–111, May–June, 2006.     

P1波入射准饱和土的波型转换问题

针对各向同性准饱和土体中体波的传播问题,本文深入研究了P1波(第一纵波)入射土体时所出现的波型转换现象。在准饱和土波动方程的基础上,通过数值算例,找出标准参数土体模型的临界饱和度及波型转换角,并分析土体孔隙率、渗流系数、水压力和入射波频率等参数对该现象的影响。     

Diffraction of Surface Waves by the Edge of a Wedge

Conditions of propagation of Rayleigh waves over an elastic wedge are considered. Refraction factors are determined for conversion of the initial wave into secondary volume and surface waves. Calculation results for the modules of the refraction coefficient agree well with published experimental data.     

冻土动态力学性能的实验研究

利用分离式霍布金森压杆(SHPB)对4种低温下的冻土进行了4种高应变 率的动态压缩实验. 实验结果表明：冻土不仅具有温度效应,还具有应变率效应,两种效应 反映出冻土材料的时温等效性. 另外这种时温等效性在分析冻土材料的破坏过程时还体现在 它的冻脆性和动脆性. 冻土材料动态应力应变曲线的汇聚现象和振荡现象均起源于这种冻脆 性和动脆性.     

Features of plane wave propagation along the layers of a prestrained nanocomposite

Features of the propagation of longitudinal and transverse plane waves along the layers of nanocomposites with process-induced initial stresses are studied. The composite has a periodic structure: it is made by repeating two highly dissimilar layers. The layers exhibit nonlinear elastic behavior in the range of loads under consideration. A Murnaghan-type elastic potential dependent on the three invariants of the strain tensor is used to describe the mechanical behavior of the composite constituents. To simulate the propagation of waves, finite-strain theory is used for developing a problem statement within the framework of the three-dimensional linearized theory of elasticity assuming finite initial strains. The dependence of the relative velocities of longitudinal and transverse waves on two components of small initial stresses in each layer and on the volume fraction of the constituents is studied. It is established that there are thickness ratios of layers in some nanocomposites such that the wave velocities are independent of the initial stresses and equal to the respective wave velocities in composites without initial stresses __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 4, pp. 3–26, April 2007.     

两微极磁热弹性固体分界面上波的反射与折射

给出了磁场、热场和弹性场多场耦合作用下微极广义热弹性固体的一般控制方程.该方 程既包含了磁场、热场和弹性场的耦合作用,又在其广义热传导方程中涵盖了耦合热弹理论 (C-D)及其5类推广(L-S理论,G-L理论,G-N(II,III)理论和C-T理论).运用该微极广义磁热 弹性控制方程,研究了在定常磁场作用下, 具有均匀初始温度的两理想接触微极弹性介质平面分界面上磁热弹性波的反射和折射现象.给出了分别在缺少磁场、热场作用或不同广义热传 导理论下反射或折射热波、纵向位移波、耦合横向和微旋转波与入射纵向位移波的振幅比随 入射角变化的关系曲线.对缺少磁、热和微极性以及热松弛时间时对应的反射、折射系数进 行了对比.结果表明磁、热和微极性以及热松弛时间对振幅比均有不同程度的影 响,与磁、热和微极性一样,热松弛时间对不同类型波的影响能力差别明显,但对同 一类型的反射波和折射波的影响相似.     

Propagation of elastic waves in water-saturated soils

A brief review of the literatures on the titled subject is given. A set of wave equations, taking the inertial coupling effect between soil skeleton and pore water into account, are established for saturated soils. The preliminary analysis shows that the nature of wave propagation is mainly influenced by permeability coefficient,k. There are three types of waves, two (P-and S-wave) propagating through soil skeleton and one(P-wave) through pore water. For a soil with large value ofk, compression wave velocity through pore water will be greater than that through single-phased water, and ask→∞, the former could be times as great as the latter. For a soil with extremely low permeability, the compression wave velocity could be either less or greater than that through single-phased water, depending on the rigidity of the soil passing through. Some phenomena observed from tests presented in the literature may be reasonably explained by the proposed theory herein, and thus more reliable parameters of soil could be obtained from wave velocity measurements. Further studies on this subject are still needed. This paper is a part of the dissertation of the first author for the Ph.D. degree, the second author is his advisor.     

Solution for plane strain forward and backward extrusions with a fractional reductionR=0.5 by the integartion depending on a parameter

A parameter t is introduced to boundary slip line of rigid regions for plane strain and indirect extrusions with a fractional reduction R=0.5. Integration by substitution has been used along the boundary slip line in order to obtain the extrusion pressure. By the integration depending on a parameter, the following results are obtained, and die pressure is 5.14k for backward extrusion; and pad average pressure is 2.57k for forward extrusion. All the results from this method are the same as those of the conventional solution.