Studies on Stress Transference Mechanism of Steel Fibre Reinforced Concrete

ＩｎｔｒｏｄｕｃｔｉｏｎＨｏｗｔｈｅｉｎｔｅｎｓｉｏｎａｎｄｍｏｄｕｌｅｏｆｓｔｅｅｌｆｉｂｒｅｒｅｉｎｆｏｒｃｅｄｃｏｎｃｒｅｔｅ (ＳＦＲＣ)ｄｅｐｅｎｄｓｏｎｉｔｓｃｏｎｓｔｉｔｕｅｎｔｐｒｏｐｅｒｔｉｅｓａｎｄｃｏｎｔｅｎｔｉｓａｐｒｉｎｃｉｐａｌｐｒｏｂｌｅｍｔｏｐｒｅｄｉｃｔｍａｃｒｏ＿ｍｅｃｈａｎｉｃｓｐｒｏｐｅｒｔｉｅｓｏｆＳＦＲＣ,ｔｈｅｋｅｙｃｏｎｓｉｓｔｓｉｎｔｈｅｃｏｎｆｉｒｍａｔｉｏｎｏｆｓｔｒｅｓｓｄｉｓｔｒｉｂｕｔｉｏｎ .Ｉｎｔｅｒｆａｃｉａｌｓｔｒｅｓｓｔｒａｎｓｆｅ…     

计及相变微结构演化的形状记忆合金本构描述

基于对NiTi形状记忆合金的实验观察及有限元分析,考虑两相间的应变不协调关系,采用应变修正法建立了计及片层状微结构的本构模型,本模型考虑了两相间的相互约束,及其约束随微结构演化的变化规律.研究了NiTi形状记忆合金微圆管在拉伸和扭转下的响应特性.计算结果与实验结果的对比表明所建本构模型较好地描述了伪弹性响应尤其是较好地描述了拉伸实验过程中的应力跌落现象.     

基于微结构损伤的珠光体材料本构行为研究

珠光体材料由许多随机取向的珠光体团组成，每一珠光体团又由铁素体片和渗碳体片交替 叠合而成. 实验表明具有较小片层间距的珠光体材料具有较高的强度和寿命. 通过分析构成 珠光体团的各相及界面的损伤特征，利用损伤耗散功的概念，得到了铁素体、渗碳体与界面 损伤的具有统一形式的演化规律，将其嵌入基于细片层微结构和非经典塑性理论的珠光体团 的弹塑性本构方程，利用Hill自洽方法，得到了珠光体材料的损伤本构描述. 所得到的损 伤本构描述显含表征微结构特征的片层间距，容易证明具有较小片层间距的珠光体材料具有 较好的综合力学性能. 对珠光体材料的拉伸和循环拉压特性进行了分析，得到了与实验一 致的结果.     

STRUCTURAL DAMAGE MODEL OF UNSATURATED EXPANSIVE SOIL AND ITS APPLICATION IN MULTI-FIELD COUPLE ANALYSIS ON EXPANSIVE SOIL SLOPE

Focused on the sensitivity to climate change and the special mechanical characteristics of undisturbed expansive soil, an elastc-plastic damage constitutive model was proposed based on the mechanics of unsaturated soil and the mechanics of damage. Undisturbed expansive soil was considered as a compound of non-damaged part and damaged part. The behavior of the non-damaged part was described using non-linear constitutive model of unsaturated soil. The property of the damaged part was described using a damage evolution equation and two yield surfaces, i.e., loading yield (LY) and shear yield (SY). Furthermore, a consolidation model for unsaturated undisturbed expansive soil was established and a FEM program named UESEPDC was designed. Numerical analysis on solid-liquid-gas tri-phases and multi-field couple problem was conducted for four stages and fields of stress, displacement, pore water pressure, pore air pressure, water content, suction, and the damage region as well as plastic region in an expansive soil slope were obtained.     

A SIMPLIFIED MODEL FOR DOMAIN SWITCHING OF FERROELECTRIC CRYSTAL

I. INTRODUCTION Domain switching is the main source of nonlinear characteristics of ferroelectric materials. The trans-formation performance of domain is the basis for ferroelectric constitutive research. In many literatures[1??10], complete switching models were adopted, in which ferroelectric materials are considered tobe consist of several basic sorts of domains, which are independent of each other. Under the actionof su?ciently strong electric ?elds or mechanical stress, the orienta…     

RESEARCH ON METHOD TO CALCULATE VELOCITIES OF SOLID PHASE AND LIQUID PHASE IN DEBRIS FLOW

Velocities of solid phase and liquid phase in debris flow are one key problem to research on impact and abrasion mechanism of banks and control structures under action of debris flow. Debris flow was simplified as two-phase liquid composed of solid phase with the same diameter particles and liquid phase with the same mechanical features. Assume debris flow was one-dimension two-phase liquid moving to one direction, then general equations of velocities of solid phase and liquid phase were founded in two-phase theory. Methods to calculate average pressures, volume forces and surface forces of debris flow control volume were established. Specially, surface forces were ascertained using Bingham's rheology equation of liquid phase and Bagnold's testing results about interaction between particles of solid phase. Proportional coefficient of velocities between liquid phase and solid phase was put forward, meanwhile, divergent coefficient between theoretical velocity and real velocity of solid phase was provided too. To state succinctly before, method to calculate velocities of solid phase and liquid phase was obtained through solution to general equations. The method is suitable for both viscous debris flow and thin debris flow. Additionally, velocities every phase can be identified through analyzing deposits in-situ after occurring of debris flow. It is obvious from engineering case the result in the method is consistent to that in real-time field observation.     

JP-10裂解的激波管实验与动力学模拟

利用单脉冲激波管对碳氢燃料JP-10在1150~1300K条件下的高温热裂解特性进行了实验研究,采用气相色谱法分析热裂解产物并获得了热裂解速率系数.主要裂解产物有乙烯、乙炔、丙烯、丁烯、1,3-丁二烯、环戊二烯、环戊烯、苯、甲苯,以及少量的甲烷、乙烷、二甲苯和甲基环戊烯.将每次激波管实验后所有产物浓度累加, JP-10裂解速率系数由实验测定.为了消除激波运行中非理想性和边界层效应导致反应温度确定的误差,采用对比速率法确定裂解温度,即在反应物中加入少量热解速率已知的内标物,根据内标物在相同的激波管实验条件下的裂解程度确定反应温度.根据内标物裂解量确定的激波管裂解反应温度通常小于采用传统测量激波速度由激波关系计算的反射激波后5区温度.在1200~1300K之间两种方法得到的温度吻合得较好,差异在20K以内,随着温度升高,两者差异增大.在实验研究的基础上,依据San Diego Mechanism对JP-10高温裂解过程进行了动力学模拟.结果显示:主要裂解产物中乙烯、乙炔和1,3-丁二烯产量随温度变化的实验值与San Diego Mechanism的模拟结果有很好的一致性,但环戊烯产量的实验值比模拟值高很多,预示JP-10裂解中完全开环和部分开环反应都是重要的裂解通道.      

任意高差的多档输电线动刚度理论建模

针对目前多档输电线动力特性研究中存在的不足,将任意一档导线视为子结构并基于现有的索振动理论获得了其动张力;利用相邻两档导线的动张力建立了悬垂绝缘子串绕其悬挂点摆动的动力学方程;综合每一档导线的振动方程以及悬垂绝缘子串的摆动方程建立了两档及三档输电线的动力学方程,求解得到由端部位移激励产生的动刚度;通过对动刚度进行分析得到了多档输电线的固有频率以及模态的理论表达形式;建立了小高差的两档及三档导线的有限元模型,理论分析结果与有限元结果一致,验证了理论公式的正确性。本文提出的动刚度理论对于研究多档输电线的动态响应具有重要的应用价值。     

Wave-based analysis of dual acoustic black holes for anechoic termination of shock testing devices

Shock testing is an important issue for the survivability of an equipment under shock environment in aerospace and military industries. One of the problems faced in conventional shock testing devices is the need for redesigning of the geometry whenever the responses to different shock environments are tested. To circumvent the redesigning processes, a structure with two ‘acoustic black holes (ABHs)’ on both ends, referred to as the beam with dual ABHs, is proposed as a shock testing device. The beam with dual ABHs is capable of simulating diverse shock environments by controlling the applied force because it can be regarded as an infinite beam at high frequency range with the aid of the anechoic terminations by the ABHs. To systematically investigate the beam with dual ABHs, we develop a wave-based method that uses the reflection matrix of an ABH to perform free and forced vibration analyses. From the analyses on frequency response function and shock response spectrum of the beam with dual ABH, it is suggested that the beam with dual ABHs is feasible as a semi-permanent shock testing device.     

Consensus of delayed multi-agent dynamical systems with stochastic perturbation via dual-stage impulsive approach

Nonlinear Dynamics - This paper investigates the problem of consensus for delayed multi-agent systems with stochastic perturbation via dual-stage impulsive approach. A novel dual-stage impulsive...