Based on the results of experiments, simulation and FEM calculation, the following are found: The values of mechanical properties measured in tensile tests are lower than those measured in compression tests. The inferior properties presented in tensile tests are caused by the damages of material, which are produced at much lower applied loads before yielding and resulted in more microcracks. Many micro-cracks initiate in the elastic condition, which shows the driving force initiating a cleavage crack is the tensile stress rather than the shear stress or the plastic strain. The interlamellar strength is lower than the translamellar strength, and even lower than the yield strength. The tensile properties of duplex microstructures are higher than that of fully lamellar, on the contrary, the fracture toughness of duplex microstructure are lower than that of fully lamellar, which is related to the grain sizes in a way. The intergranular fracture and finer interlamellar fracture are the dominant fracture mechanisms in the duplex microstructure materials, the fully lamellar microstructure materials resulted in more translamellar fracture. The fatigue fracture surface and mono-bending fracture surface presents almost the same mode. The cracks extend directly from a notch or a precrack controlled by the tensile stress. The superblunting, burification and deviating from direction of tensile stress of the crack-tip fronting an obstacle are the main toughening mechanism.
在这些实验与模拟计算的基础上，我们初步分析了TiAl基合金室温断裂机理，得到了以下几个方面的结论：这种材料的拉伸与压缩性能存在很大差异，拉伸性能远低于压缩性能，在拉伸时测得比较差的性能是由于材料在很小载荷拉伸时产生微裂纹，导致了材料的损伤；大量微裂纹产生于弹性阶段，其驱动力是拉伸应力，而不是剪切应力或者塑性应变；沿层强度低于穿层强度，甚至低于屈服强度；双态组织的拉伸性能高于全层组织，而双态组织的断裂韧性低于全层组织，这与晶粒尺寸的大小有一定的关系；双态组织的断裂形态表现出更多的沿晶粒边界断裂和小沿层面断裂，而全层组织中表现出更多的穿层断裂；疲劳裂纹的断裂形态与加载过程中产生的裂纹断裂形态没有本质差别，加载过程中产生的裂纹是疲劳裂纹的延续，是逐渐扩展的过程；无论缺口试件，裂纹试件还是光滑试件，都是逐渐扩展的过程，所以解理断裂为扩展控制，控制的因素为拉伸应力；裂纹扩展时遇到取向不利的经历而引起裂纹尖端的超钝化，分叉，方向偏移是其主要的韧化机理，在裂纹很短时表现出上升的阻力曲线。
Based on the analysis of cyclic fatigue load and the stress of gear shaft, the reason of the shaft fracture is discussed.
通过对齿轮轴进行循环疲劳加载和应力分析，我们对轴的断裂进行了探讨。
The properties of rock cutting fracture stress are further analysed by fractography of rock chip.
文中采用显微观察法，对三种硬岩的切削过程作了研究。
The thermal stress fracture resistance factor R is used to characterize the thermal shock resistance of the ceramic material.
结果表明：当Ti和SiC的体积含量分别为10.4%和27.1%时，该材料具有最高的抗热震性能，比纯氧化铝陶瓷提高约55%。
On the basis of the core fracture observation of Sangonghe Formation and the analysis of partial structural features of Baobei structure in Yanqi Basin, investigates the partial stress field and the fracture growing feature from the aspects of anticline and fault.
根据焉耆盆地宝北构造三工河组岩心裂缝的实际观测及宝北区块的局部构造特征，从背斜和断层两方面对局部应力场和裂缝发育特征进行解析，认为宝北构造的裂缝组合模式为：顺层滑脱裂缝+纵张裂缝+高角度共轭剪切裂缝+中、低角度共轭剪切裂缝+左阶张裂缝。
A macro and micro and chemical element analysis was made on fracture of ruptured coupling bolts, torsion test was performed and stress analysis and calculation were made, the results show that when the steam turbine had failure, MP-LP rotor coupling bolts and generator-exciter rotor coupling bolts failure were classified as overload shear fracture with partial deformation.
对215MW汽轮机断裂的对轮螺栓做断口宏观、微观分析，化学元素分析，扭转试验及受力分析计算，结果表明汽轮机组在事故中，中压-低压转子对轮螺栓和发电机-励磁机转子对轮螺柱的失效类型为：过载剪切断裂，同时局部挤压变形，这是由于事故过程中轴系受到冲击扭矩作用而引起的。
In order to establish contact between the damage analysis and the study of fracture mechanics, a new formulation of damage variable is proposed in this paper. Then the crack line field analysis method is for the first time used to investigate the micro crack in concrete. The formula referred to the un-dimensional length of damage cracking zone and the un-dimensional tension stress is found out. And also the maximum tension stress varied with micro crack spacing and the evolving equation with bending damage of the concrete pile are obtained. The influence of the micro crack density on damage cracking in concrete is analyzed. The calculation of the cracking level of the concrete pile is discussed.
本文提出了混凝土损伤变量的新的定义形式而将损伤分析与断裂力学分析联系起来；首次运用裂纹线场分析方法对混凝土中的微裂纹进行了分析；得出了裂纹线上损伤断裂区无量纲长度与无量纲拉伸应力之间的关系、不同微裂纹间距所对应的最大荷载以及混凝土桩抗弯的损伤演化方程：分析了混凝土内微裂纹密度变化对混凝土损伤断裂的影响，并对混凝土桩的抗裂度计算进行了讨论。
Besides, the fractography was observed by SEM, the results show that the reason of the fracture on the corner of workpiece is tensile stress.
此外，通过扫描电镜对断口形貌的观察，发现在薄壁件的刀具切出处的崩角主要是拉应力作用的结果。
In this paper, the authors try to investigate the possible relation between the fracture toughness Kc and the temperature T for nodular cast iron, who are ues the results from Rauh, Bullough and the domestic studies in the rules of the stress-driven migration of point defects to a crack, the following results are observed through the test.
本文运用Rauh和Bullough及国内研究者提出的裂纹应力场中点缺陷的迁移规律，研究了球墨铸铁断裂韧性Kc随温度T变化的规律。
Based on the example in Min114 block at Xinmin oil field, the authors analyze the relation of the fracture and crustal stress, measure the direction and length of the hydraulic fracture by receiving the microseism signals when the terrene is broken, which provides a basis for deploying reasonable flood pattern for development of low permeability reservoir.
以新民油田民114区块为实例，利用微震裂缝监测技术，通过接收地层破裂时的微震信号测定水力压裂产生的人工裂缝的走向与长度，分析裂缝发育与地应力的关系，为低渗透油藏开发中合理部署注采井网提供依据。
In view of practical problem during Sulige gas field development, this paper complete follow study content. Study material balance theory of two district compound gas reservoir. Carry out stress sensitivity experiment on matrix rock and labor created fracture core from Sulige gas field with America Core Company high pressure high temperature flow experimental instrument to study stress sensitivity change rule of different permeability matrix rock and created fracture core at the condition of time and again switch on and off well and different drawdown pressure. Carry out depletion experiment on matrix rock of different permeability serial combination with different kinds of allocation, using double core clamper serial connected experimental apparatus, to study gas well production performance of bi-zonal compound low permeability reservoir during low pressure production stage. At the basis of experimental study, establish single well simulation model to analyze development index infection caused by stress sensibility and production performance infection rule caused by inner formation and outer formation of bi-zonal compound gas reservoir permeability variation while considering stress sensitivity.
针对苏里格低渗气田开发中存在的实际问题，完成以下研究内容；研究了两区复合气藏物质平衡原理；利用美国岩芯公司高温高压流动实验仪，对取自苏里格气田基质岩芯和人工造缝岩芯进行应力敏感实验，研究不同渗透率基质岩芯和造缝岩芯在多次开关井和不同生产压差条件下的应力敏感变化规律；采用双岩芯夹持器串联实验装置，对不同渗透率串联组合的基质岩芯进行各种配产条件下的衰竭实验，研究两区复合的低渗储层气井在低压生产阶段的生产动态特征；在实验研究的基础上，建立单井模拟模型分析储层应力敏感性和非均质性对开发指标的影响，研究考虑应力敏感时两区复合气藏储层中内区和外区渗透率变化对开发动态的影响规律。
The crack tip stress analysis of fracture along coplanar slip band showed that, for the materials with lower or easy to be weakened strain hardening capacity, secondary slip is difficult to activate due to the plastic zone size of non-coplanar secondary slip much smaller than that of coplanar slip, so a large normal stress near crack tip can be set up and fracture along coplanar slip band with cleavage characteristics occurs.
沿共面滑移带开裂的裂纹尖端应力分析表明，对于应变硬化能力较低或这种能力易受到削弱的材料，非共面次滑移塑性区尺寸远远小于共面滑移，使次滑移很难开动，从而在裂尖形成很高的正应力，导致了具有解理特征的共面滑移带开裂。
FEM model of hinge axle is established and the force-stroke curve of the punch mold is described. The probabilities of material`s yield deformation and stress concentration are calculated respectively, and it is shown that the main cause of the fracture is stress concentration.
建立铰链轴的有限元数值模型，归纳出冲床上模的力—行程曲线，通过分析破坏指标值和有效应力指标值，计算出组织流动原因的可能度和应力集中原因的可能度，得出应力集中是产生裂纹的根本原因。
Based on the analysis result of stress states of the die structure, the influences of the draft angle of down punch and the wall unevenness of blank on the stress state of is analyzed with finite element numerical simulation. Researches are done on the fracture states of die by macroscopic examination, SEM analysis, metallographic analysis and Mechanical Properties. Then the reasons for early failure are determined.
在模具结构受力状况分析的基础上，利用有限元数值模拟，分析了成形下凸模拔模斜度和工件毛坯壁厚不均程度对模具应力的影响，采用断口分析技术，对断口进行了宏观检验、扫描电镜分析、金相分析和力学性能检测，对结果进行综合分析后确定了导致模具早期失效的原因。
The results of the structure analysis show that: when =2.0°, the stress of down punch has reduced to 2270Mpa and the utilization ratio of blank is higher, When the blank exists wall unevenness, the normal stress of die can increase to 2500~2700MPa. The results of fracture analysis show that: the form of failure is brittle overload fracture; cracks are cleavage brittle; the degree of carbide segregation is too high and bending strength is not enough.
对模具结构的模拟结果表明：当拔模斜度=2.0°时，下凸模最大等效应力减小至2270MPa，且具有较高的原料利用率；工件毛坯壁厚不均匀时，模具法向应力增大至2500～2700MPa之间；断口分析结果表明：模具失效机理为过载脆性断裂，断口呈现解理脆性裂纹，材料碳化物偏析程度过高且抗弯强度严重不足。
Based on the theory of fracture mechanics and the principle of structural reliability analysis, a computation formula of the fatigue failure of suspension cable system in a suspension bridge caused by alternate stress is deduced, thus an evaluation method on the safety life of suspension cable system which has been subjected to eroding is suggested, according to which, highway administration departments can arrange the opportunity of detection, maintenance and strengthening of bridges, as well as the investment.
根据断裂力学理论和结构系统可靠性分析原理，推导出交变应力引起的悬索桥吊索系统疲劳失效的计算公式，从而提出的一种考虑构件腐蚀后吊索系统安全寿命的评估方法，可以为公路管理部门合理安排桥梁的检测、维修、加固的时机和投资提供依据。
The following work is completed in this paper. Analyzing the types and affecting factors of the floor water invasion, this paper makes certain of the reason of the water invasion in the floor. This paper applies the fracture mechanics theory, the elastic-plasticity theory and the finite element method to resolve the damage depth, the transferring character of the stress and the utmost pressure of water invasion in the floor of the water-resisting layer in the coal seam with the complex effect of the mining pressure and the water pressure in the floor water-resisting layers. In addition, the resolution is put into the extract project of the 3629 working face in Zhu zhuang Coal mine forecasting the water invasion in the floor which plays an important guiding role in mining this working face safely.
本文主要开展了如下几个方面的工作：分析底板突水类型及影响因素，确定底板突水的原因；运用断裂力学理论、弹塑性理论及有限元方法解析煤层底板隔水层在采动矿压及底板含水层水压的复合作用下的破坏深度、应力传播特征、底板突水极限压力，并将解析解应用于朱庄煤矿3629工作面底板突水预测的实际工程中，对该面实现安全回采起到了重要指导作用；利用相似材料模型及大型有限元软件对煤层底板岩层应力分布规律和底板移动破坏特征进行了模拟，分析了煤层底板突水的机理及底板岩层的突水破坏规律。
Secondly, RFPA software which is simulating the Rock Fracture Process is used to analyze the fracture process from meso-damage to macro fracture of granite test block. And relationship curve between axial stress and strain is also obtained. Based on least energy consumption principle, stress-strain relationship under uniaxial compression is obtained by using Matlab software.
其次，采用试验和岩石失稳工程分析软件分析花岗岩试块从细观损伤到宏观破坏的整个过程，并得出了在整个过程中的轴向应力应变关系曲线，并用数学分析软件Matlab得出了基于最小耗能原理的单轴压缩下应力应变关系图，并且将其与经典的Marzars损伤理论、数值模拟曲线进行对比研究，可以发现基于最小耗能原理的损伤演变方程更能反映岩块的损伤过程，且更符合实际情况。
Considering the stress-strain field distribution rules of welded joints containing single-edge crack on fusion line, the fracture parameter COD is decomposed into two parts of mode I and Mode II.
结合裂纹尖端应力应变场的分布规律，讨论了熔合线上含裂纹焊接接头的COD断裂参量的分解情况。
Firstly, the temperature field of welded joints is simulated. Basingon the result, the welding residual stress is calculated, at the same time, thedistribution characteristics of residual stress, which for the welded joints especiallyfor the fatigue fracture zone, are studied.
首先模拟接头的焊接温度场，在此基础上计算接头残余应力，并且分析研究了焊接接头尤其是疲劳断裂危险区的残余应力分布特征。