强度理论研究发展概述

1强度理论发展过程 1.1早期强度理论 早期的强度理论包括以下三个强度理论： 第一强度理论最大应力理论是关于材料在复杂应力下强度的理论。认为最大拉应力或最大压应力是决定材料强度的准则。该准则曾经被Lame（1795年、1870年）和Rankine（1820年、1872年）等科学家采用。最大应力理论只考虑了3个主应力σ1、σ2、σ3中的一个主应力σ1。     

材料力学学习辅导之(二)

在掌握了轴向拉仲(压缩)、圆轴扭转及梁的弯曲这三种基本变形的内力、应力、变形及强度和刚度计算后,我们将进一步学习以这三种基本变形为基础的组合变形,而为解决组合变形时的强度问题,就必须先掌握应力状态理论和强度理论。     

关于应力理论与强度理论的教学探讨

在材料力学的应力理论与强度理论的教学中,深入对"横截面上点的应力与点的应力状态"、"由四个强度理论建立的强度条件与基本变形的强度条件"、"低碳钢、铸铁拉伸破坏及扭转破坏与材料的断裂破坏、屈服破坏"三个问题的教学讨论,促进了学生对应力理论与强度理论的学习,提高了应力理论在材料力学中的地位和作用,加深理解了强度理论的实践意义及应用价值。     

基于统一强度理论的拉压异性材料厚壁圆筒的自增强分析

运用统一强度理论对承受内压的拉压屈服强度不同材料的厚壁圆筒进行了自增强分析,得到了适用于多种材料的厚壁圆筒弹性区与塑性区中的应力分布,残余应力分布及合成应力分布的统一解析式,分析得出了最佳弹塑性半径和最佳自增强内压的统一解析解.     

线性强化材料厚壁球壳的统一自增强分析

运用统一强度理论对承受内压的线性强化材料的厚壁球壳进行了自增强分析,得到了适用于多种材料的厚壁球壳弹性区与塑性区的应力分布、残余应力分布及合成应力分布的统一解析式.并根据厚壁球壳的安定性条件和合成应力分布分析得出了最佳弹塑性半径和最佳自增强内压的统一解析解.     

应力圆在材料力学教学中的应用

研究平面应力状态的方法通常有解析法和图解法.图解法即应用应力圆解题,这种方法直观方便.讨论了应力圆在解释莫尔强度理论、求解三角形单元体有关应力问题中的应用.     

对轴的强度校核计算方法的讨论

轴的强度校核在材料力学和机械零件等课程的教学中具有重要的地位。转轴一般都是工作在弯曲与扭转共同作用的复合应力状态下,对它的强度校核,一般是采用当量应力法或疲劳安全裕度的方法。这些强度校核计算方法的理论依据是塑性材料屈服失效理论(最大切应力理论与歪形能理论),并且考虑轴危险剖面上的弯曲正应力与扭转切应力的循环特性,以及轴的绝对尺寸、表面质量和应力集中等因素对     

材料力学学习辅导之一

材料力学是一门专业基础课程,课程的主要内容包括:轴向拉伸与压缩、圆轴扭转、梁的弯曲这三种基本变形的内力、应力、变形计算及相应的强度问题;应力状态和强度理论及在此基础上对组合变形进行强度计算;压杆稳定问题;能量法等。 材料力学课程涉及的概念多,题目计算也较繁锁,要学好本课程,首先要认真理解概念,掌握基本公式、定义及结论,而且应了解各     

CAE在强度理论教学中的应用

本文提出了强度理论全程动态学习的理念,借助UG—CAE模块的实践教学,进一步强化了学生对材料力学中应力与强度理论的理解,实现了强度理论与CAE案例教学的有机融合,增强了学生处理工程问题的力学能力。     

材料力学复习概要(下)

在掌握了轴向拉伸(压缩)、圆轴扭转和梁的对称弯曲这三种基本变形后,下面将结合典型例题分析归纳总结应力状态理论和强度理论、组合变形、压杆稳定和疲劳强度问题以及能量法这几章的重点内容,最后还要就期末复习及考试的有关问题作一些说明,并给出一套综合练习题对题型加以说明。 一、应力状态理论和强度理论     

细环壳方程的非齐次解在Ω型波纹管整体弯曲问题中的应用

A linear complex equation for slender ring shells overall-bending in a meridian plane is given based on E. L. Axelrad's theory of flexible shells. And the non-homogeneous solution is obtained from W. Z. Chien's solution for axial-symmetrical slender ring shells to investigate the overall-bending problem of Ω-shaped bellows subjected to pure bending moments. The values calculated in the present paper are very close to the existing experiment. Thus Chien's work on axial-symmetrical problems for ring shells has been extended to overall-bending problems.     

The Hamilton System and Hamilton Type Generalized Variational Principle for the Laminated Composite Plates and Shells

lintroductionTileHamilton'systemwasfirstestablishedinthegeometricaloptics,andwasappliedtothetheoreticalmechanicslater.ItsbasicideaistotransformtheEuclidspacetothesymplecticgeometryspaceforcomputing,thatistosay,theLagrangeequationsarechangedintotheHamilton…     

Restrained torsion of open thin-walled beams including shear deformation effects

A first-order torsion theory based on Vlasov theory has been developed to investigate the restrained torsion of open thin-walled beams. The total rotation of the cross section is divided into a free warping rotation and a restrained shear rotation. In first-order torsion theory, St. Venant torque is only related to the free warping rotation and the expression of St. Venant torque is derived by using a semi-inverse method. The relationship between the warping torque and the restrained shear rotation is established by using an energy method. The torsion shear coefficient is then obtained. On the basis of the torsion equilibrium, the governing differential equation of the restrained torsion is derived and the corresponding initial method is given to solve the equation. The relationship between total rotation and free warping rotation is obtained. A parameter λ, which is associated with the stiffness property of a cross section and the beam length, is introduced to determine the condition, under which the St. Venant constant is negligible. Consequently a simplified theory is derived. Numerical examples are illustrated to validate the current approach and the results of the current theory are compared with those of some other available methods. The results of comparison show that the current theory provides more accurate results. In the example of a channel-shaped cantilever beam, the applicability of the simplified theory is determined by the parameter study of λ.     

Study on applicability of modal analysis of thin finite length cylindrical shells using wave propagation approach

INTRODUCTION Vibrations of cylindrical shells are of consider-able importance as they are extensively used in in-dustry,flight structures and marine crafts.The naturalfrequencies and mode shapes are important sources ofinformation for understanding and controlling thevibration of these structures,so many papers on theprediction of the natural frequencies of cylindricalshells have been published over the past years.Many shell theories have been developed andvarious solution methods have bee…     

粘弹性开敞浅壳的动力学性质

On the basis of the Kármán-Donnell theory of thin shells with large deflections and the Boltzmann laws for linear viscoelastic materials, the mathematical model for viscoelastic open shallow shells was formulated. By using the Galerkin average method, the original integro-partial-differential dynamic system was simplified as a integro-ordinary-differential dynamic system, which can be transformed into a ordinary differential dynamic system by introducing new variables. The dynamical behavior was studied by some classical methods. Dynamical properties, such as, chaos, strange attractor, limit cycle etc., were discovered. Supported by the Development Foundation of Shanghai Municipal Commission of Education (99A01)     

旋光仪三分视野原理和零度视野确定

该文叙述了旋光仪三分视野原理和旋光仪零度视野确定和调节方法,有助于正确掌握旋光仪的使用技术,提高测量准确度。     

妈祖像形珍珠雕刻贝屏的开发研究

应用现代珍珠养殖理论和技术以及贝雕工艺,并利用褶纹冠蚌(Cristaria Plicata Leach)研制妈祖像形珍珠雕刻贝屏,结果表明:妈祖像形珍珠雕刻贝屏既具有珍珠的自然属性,又蕴含妈祖文化品味,是一种赏心悦目和具有珍藏价值的高雅工艺品;褶纹冠蚌是生产妈祖像形珍珠雕刻贝屏较理想的一种淡水珍珠贝类。为弘扬妈祖文化提供一种新思路和新方法。     

关于中国修辞思想萌芽期的论定

中国修辞思想萌芽期的论定是中国修辞学史研究不可回避的重大问题。目前较为通行的“中国修辞思想的萌芽期———先秦时代”的观点尚有许多可质疑之处。修辞学研究也必须坚持“例不十 ,法不立”的立论原则。先秦时代已不是中国修辞思想的萌芽期 ,而是成熟期 ;许多例证表明 ,中国修辞思想萌芽于商周甲骨金文时代     

超细铅锌尾矿砂混凝土的研究

本文是关于如何利用工业废料—铅锌尾矿砂,制造混凝土和空心建筑砌块。该砂的细度模数 M 为0.4。如此的超细砂铅混凝土的生产工艺带来了很多困难。通过大量试验得出了超细砂的配合比。同时应用造壳理论我们还获得了超细砂混凝土的生产工艺。     

单模光纤频移效应及分子阻碍内旋转理论(英文)

本文用分子阻碍内旋转理论，分析了单模光纤的频移效应。