非均质土层下基桩的动力稳定性研究

本文根据桩在轴向谐振力作用下，探讨了非均质层下基桩的动力稳定性问题，分析了各种地基土横向抗力系数K以及桩的几何特征，激振频率，桩土阻尼对桩动力稳定性的影响，结果表明，随地基土层的不同，基桩的动力不稳定区域将发生不同的变化，随桩径，桩长的增大，基桩的动力不稳定区域将逐渐减小，表明地基土的横向抗力对桩的动力稳定性起加强作用，桩土阻尼对基桩的动力稳定性影响较大，得出了一些有价值的结论，可为工程设计提供参考依据。     

纤维树脂界面剪切强度及纤维强度分布参数的实验测定

界面剪切强度及纤维强度分布参数是复合材料设计及应用研究中的重要参数，本文采用单纤维段埋入法测定了上述两个参数。通过实验研究说明了单纤维段埋入法是一种测定界面剪切强度及纤维强度分布参数的有效的实验方法；同时证实了基体的力学性能对界面剪切强度有着重要的影响。全部实验在自制的实验系统上完成     

Molecular-dynamics of a 2D Model of the Shape Memory Effect

This work investigates the thermodynamic properties of a qualitative atomistic model for austenite–martensite transitions. The model, still in 2D, employs Lennard-Jones potentials for the determination of the atomic interactions. By use of two atom species it is possible to identify three stable lattice structures in 2D, interpreted as austenite and two variants of martensite. The model is described in the first part of the work [6] in detail. The present work studies the thermodynamic properties of the model concerning a small, 2-dimensional test assembly consisting of 41 atoms. The phase stability is investigated by exploitation of the condition of minimal free energy. The free energy is calculated from the thermal equation of state, which is measured in numerical tensile tests. In the second part of this work a chain of eleven 41-atom assemblies is investigated. The chain is interpreted as an idealized larger body, where the individual crystallites represent crystallographic layers allowing for the creation of micro structure. By use of tensile tests at various temperature conditions we sketch how such chain may exhibit quasi-plasticity, pseudo-elasticity and the shape memory effect.     

机载惯导两套配置时的故障诊断研究

分析了飞机惯导采用两套配置时对不同故障的诊断方法,主要分为两类:一类是借助两个平台四个加速度计的输出,诊断陀螺慢漂移过大的问题,文中给出了两平台相对转角及其补偿的实现方法;另一类是借助大气数据系统和解析余度的方法,通过建立故障诊断模型,检测两个互不相关惯导系统的故障,文中给出了方案,指出了难点。     

On the basic laws of anisotropic viscoelasticity

The main aim of this work is to develop a consistent formulation of the rheological behavior for different anisotropic polymer systems. The unified theory of anisotropic viscoelasticity is developed based on the symmetry principles. The Maxwell rheological equation is extended to nonsymmetric anisotropic liquids. Transitions from the most general anisotropy to particular cases of anisotropy are established. It appears that the coupled relaxation of symmetric and antisymmetric stresses is a natural phenomenon in nonsymmetric viscoelasticity. Within the concept of an internal state variable, a stress–order relation is derived for a fully nonlinear case. The order tensor dynamics is also considered. A simple method of deriving the equation of the internal rotational motion is developed for the general macroscopic anisotropy. This paper was presented at the 3rd Annual Rheology Conference, AERC 2006, April 27–29, 2006, Crete, Greece     

形状记忆合金纤维复合材料的等效力学行为

在Aboudi提出的胞元模型以及Liu等建立的形状记忆合金的本构模型的基础上，由Legendre多项式，假设每个子胞元的位移场、应变场和应力场，再由子胞元间交界面的应力连续条件和外荷载边界条件推导出基体为弹塑性材料的形状记忆合金纤维复合材料的胞元模型；模拟了呈周期对称的形状记忆合金纤维复合材料受轴向单向拉伸、横向拉伸和横向剪切荷载作用下的等效力学行为，与有限元解进行了比较，结果基本一致。与有限元法比较起来，本文推导出的形状记忆合金纤维复合材料的胞元模型更具高效性。     

氮化硅陶瓷平板振动模态参数的研究

本文采用压电陶瓷片测振技术,试验分析了氮化硅陶瓷平板的固有频率及模态阻尼比,试验结果与有限元计算结果比较吻合。本文还对氮化硅陶瓷平板与普通钢平板做了对比试验,结果表明氮化硅陶瓷平板的固有频率及模态阻尼比都较高。     

ON THE METHOD OF ORTHOGONALITY CONDITIONS FOR SOLVING THE PROBLEM OF LARGE DEFLECTION OF CIRCULAR PLATE

In this paper,we reexamine the method of successive approximation presented byProf.Chien Wei-zang for solving the problem of large deflection of a circular plate,and findthat the method could be regarded as the method of strained parameters in the singularperturbation theory.In terms of the parameter representing the ratio of the centerdeflection to the thickness of the plate,we make the asymptotic expansions of thedeflection,membrane stress and the parameter of load as in Ref.[1],and then give theorthogonality conditions(i.e.the solvability conditions)for the resulting equations,bywhich the stiffness characteristics of the plate could be determined.It is pointed out thatwith the solutions for the small deflection problem of the circular plate and theorthogonality conditions,we can derive the third order approximate relations between theparameter of load and the center deflection and the first-term approximation of membranestresses at the center and edge of the plate without solving the differential equ     

Parametric analysis of lugged wheel performance for a lunar microrover by means of DEM

The purpose of this study was to develop a numerical tool to simulate the performance of lugged wheels designed for a lunar microrover. The performance was analyzed using a Discrete Element Method (DEM) whose accuracy was validated for interactions between lugged wheels and soil. DEM analysis indicated that, on flat horizontal lunar surfaces, wheels with 18 10-mm-high lugs would provide less net traction than would wheels with 36 5-mm-high lugs.     

Crack growth resistance of shape memory alloys by means of a cohesive zone model

Crack growth resistance of shape memory alloys (SMAs) is dominated by the transformation zone in the vicinity of the crack tip. In this study, the transformation toughening behavior of a slowly propagating crack in an SMA under plane strain conditions and mode I deformation is numerically investigated. A small-scale transformation zone is assumed. A cohesive zone model is implemented to simulate crack growth within a finite element scheme. Resistance curves are obtained for a range of parameters that specify the cohesive traction-separation constitutive law. It is found that the choice of the cohesive strength t₀ has a great influence on the toughening behavior of the material. Moreover, the reversibility of the transformation can significantly reduce the toughening of the alloy. The shape of the initial transformation zone, as well as that of a growing crack is determined. The effect of the Young's moduli ratio of the martensite and austenite phases is examined.