Generation and evolution of cavitation in magma under dynamic unloading

The full system of equations for the problem of rarefaction-wave passage over the magma-melt column in the gravity field is derived with the use of the kinetic theory of phase transformations, and the problem is numerically solved. With allowance for diffusion zones and nucleation frequency as a function of supersaturation, the dependence of the number of cavitation nuclei formed in the course of phase transformations behind the rarefaction-wave front is found. The dynamics of the size distribution of cavitation bubbles along the magma-melt column (1 km) whose viscosity varies dynamically as a function of the concentration of dissolved water is studied.Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 2, pp. 71–80, March–April, 2005.     

含能材料三轴动态压缩实验的一个计算机模拟方法

在含能材料单轴、受限三轴动态压缩实验的基础上，提出一种将计算机数值模拟和实验数据相结合，估算实验系统中钢筒与试件间的库伦摩擦力，从而正确确定含能材料的动态三轴力学性能（弹性模量Ｅ，泊桑比ν，屈服限Ｙ等）的方法。本方法用于ＴＮＴ炸药受限三轴动态压缩实验，通过建立钢筒－试件的库伦摩擦有限元模型，采用ＡＤＩＮＡ通用程序进行动力分析，估算了摩擦力对实验数据的影响，获得了考虑摩擦力修正后的ＴＮＴ三轴动态压缩响应，为含能材料三轴动态力学性能的确定提供了一种有效的方法。     

饱和地基上含刚核弹性圆板的竖向振动分析

基于作者提出的饱和土弹性波动方程，研究了饱和地基上含刚核弹性圆板在竖向集中谐和力作用下的振动特性。首先应用Hankel积分变换求解该饱和土波动方程，然后按混合边值条件建立起一组描述含刚核弹性圆板振动的对偶积分方程，并将其化为第二类Fredholm积分方程进行数值求解。文末给出了含刚核弹性圆板在饱和地基上振动的阻抗函数随无量纲频率a0的变化曲线，并考察了土的渗透系数，弹性板含刚域的大小以及板的柔度等参数对阻抗函数的影响，得出了一些有意义的结论。     

磁性敏感器用于冲击变形测量

一种新型的非接触式磁性位移敏感器,兼有高灵敏度(50-80mV/mm)、大线性范围(15-25mm)以及响应快(4kHz)等优点.用于测量20mm以内的冲击动态变形获得成功.     

磁浮列车的动力稳定性分析与Liapunov指数

针对弹性轨道上的磁悬浮列车线动力控制系统,给出了采用Ｌｉａｐｕｎｏｖ特性指数送别动力系统稳定性的判据：当动力系统的全部Ｌｉａｐｕｎｏｖ特性指数小于零时,动力控制系统是稳定的;而当动力系统有一Ｌｉａｐｕｎｏｖ特性指数大于零时,动力系统就成为不稳定的,由于Ｌｉａｐｕｎｏｖ特性指数可以由数值积分方式方便地给出,这一判断方法对于不便搜索参数稳定区域的高维动力系统,与寻求周期变系数线性常微分方法动力系统的Ｆ     

拱形试件动态断裂的动光弹分析

本文采用动光弹方法,分析了对带边裂纹的拱形三点弯曲试件在抢击加载条件下的瞬态反应。从多火花动光弹仪记录下来的16幅断裂过程的照片和微机输出的电火花光信号图上,得到了各时刻的等差线图形和裂纹长度。使用运动裂纹尖端附近的应力场解,去计算动应力强度因子。对环氧树脂材料,测定了动态应力强度因子与裂纹扩展速度之间的关系,并给出了当裂纹扩展速度达到410m/s时,为裂纹产生分叉的条件。     

Numerical solution to the buckling problem for a sandwich plate under uniaxial compression

A thin rectangular sandwich plate with isotropic linear elastic layers is considered. The plate is in a plane-strain state under uniaxial compression. An exact statement of the buckling problem is given. Its approximate solution is found by the finite-difference method. The concept of base scheme is used to formulate discrete problems in explicit and compact form. As an example, the critical parameters of the plate are calculated using a computation optimization procedure. Its efficiency is demonstrated __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 9, pp. 98–105, September 2006.     

旋转倒立双摆摆起控制量的动态设计变量优化

倒立摆的摆起过程是复杂的非线性力学与控制的综合问题,当力学模型和参数确定时,寻求有效方法计算控制律函数是实现摆起的关键。本文以倒立双摆模型为研究对象,将动态设计变量优化方法引入对摆起开环控制律的分析,编制计算机程序进行数值仿真,确定了控制律函数与状态量随时间变化的状态,为复杂强非线性系统的控制提出了一种有效方法。     

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.     

钨合金的冲击动力学性质及细微观结构的影响

简单介绍了钨合金(主要为W-Ni-Fe)的制备工艺和常用热处理方法,其后着重从动 态力学性能、剪切带的实验观察和研究、细微观结构对材料力学性能的影响等几方 面总结和评述了近年来针对钨合金取得的主要结果.并在文章的最后初步提出了有 前景的几个研究方向.