高温构件的概率寿命预测与可靠性

通过应用高温构件蠕变损伤的随机方程及一次二阶矩理论和方法 ,对高温构件的概率寿命预测进行了研究。还应用高温构件寿命的概率计算方法 ,考虑服役高温构件的实际运行工况 ,得到了高温构件寿命与可靠性的关系。由于充分考虑了各参数的随机性和相关性 ,因而大大提高了计算的准确性     

油气管道的疲劳断裂分析及寿命预测

疲劳断裂是油气管道工程常见的损伤之一,科学的分析和预测对管道工程的安全运行具有十分重要的意义。本文从理论角度上,对疲劳积累损伤理论和疲劳裂纹扩展理论这两大疲劳断裂分析的基本理论进行了介绍,同时,对基于断裂力学的疲劳寿命预测方法进行了阐述,为管道维护、检修和管理提供一定的理论基础和指导。     

高温构件材料临界损伤的定量分析

以石化企业工业炉常用的炉管材料HK40为研究对象 ,采用定量金相技术 ,测定了裂纹尖端的A参数 ,应用A参数和损伤D的关系 ,得到材料的微观临界损伤值。并比较了A参数方法与应用局部损伤力学理论方法以及测定高温构件材料的弹性模量方法获得的材料临界损伤值。高温构件材料的临界损伤值的测定为准确进行高温构件寿命预测提供了条件。     

混凝土结构的损伤失稳分析

本文通过运用断裂与损伤力学的相关知识,从理论的角度,阐述了混凝土结构的宏观力学性质与断裂机理,分析了混凝土结构的失稳破坏过程。对比了传统固体力学与断裂损伤力学在混凝土结构分析问题上的异同。断裂力学主要是研究宏观裂纹的扩展以及含宏观裂纹的变形体的力学性能,而损伤力学主要是研究宏观裂纹扩展以前的情况,即微观下混凝土裂纹的形成过程。宏观的损伤力学是以连续介质损伤力学的观点来研究材料的损伤破坏。这种方法的优点是其以材料的宏观力学性能测试为基础,因而便于工程应用。     

高分子材料断裂力学评价方法研究进展

简要介绍了线弹性断裂力学、弹塑性断裂力学和基本断裂功这3种方法的理论背景和前提假设、材料参数的试验测试方法和计算过程、试样预制裂纹对测试结果的影响以及近些年在高分子材料上的应用研究进展，并对3种研究方法的应用范围和特点，具体实用效果进行了对比分析。     

浅谈断裂力学的发展与研究现状

本文通过对断裂力学的创立和发展的讨论,进一步说明科学技术与生产实践的进步是断裂力学产生的根本原因,继承和突破是断裂力学发展的基本途径,断裂力学的发展与生产实践紧密相关为基本论点,以及对新材料断裂理论的探索与对未来断裂力学的展望。     

建筑玻璃的断裂力学

基于经典断裂力学理论,研究建筑玻璃断裂原理、裂纹扩展、表面形貌与裂纹形态,并对I型断裂与格里菲斯方程结合对裂纹扩展速率的影响加以分析。根据有关玻璃断裂实例,对比全钢化、半钢化、未钢化玻璃的表面应力与颗粒度,分析玻璃挠度对于破裂颗粒度的影响,以期有助于玻璃材料断裂力学研究工作的开展。     

基于线弹性断裂力学的注塑机拉杆组件的微裂纹稳定要素的研究及应用(下)

基于线弹性断裂力学的微裂纹理论,分析了注塑机拉杆组件的微裂纹稳定要素与断裂之间的关联。纠正了传统的拉杆组件非对称循环的运动力学的特性的观点,首次提出了拉杆组件脉动循环的弹性力学的运动特性的新观点,为科学运用微裂纹稳定的应力强度因子理论奠定了理论基础。创建了微裂纹稳定的应力强度因子的判据理论,解释了拉杆断裂的力学因素,提供了卸载性能的微裂纹稳定的理论设计依据。结合实例,提出了微裂纹稳定的可靠性安全系数均值、承载能力的综合系数、脉动循环屈服强度等三个要素的工业设计理论及应用原则,提出了微裂纹稳定的卸载段直径、螺纹段底径及拉杆螺母的设计理论及确定原则。研究了线弹性断裂力学要素与弹性力学性能之间、与质量控制之间的关联,探索提高微裂纹稳定的质量要素研发方向。运用创新的拉杆组件的线弹性断裂力学要素的工业设计理论,分析了断裂失效实例,进一步说明线弹性断裂力学要素的微裂纹失稳的研究有助于预测和防止拉杆组件的断裂现象的发生。     

T700/双马复合材料蜂窝夹芯结构损伤修复实验研究

本文制备了复合材料蜂窝夹芯结构件和三种孔径的半穿透损伤件,采用挖补工艺对损伤件进行了两种不同体系的修复,并测试了完好件、损伤件和修复件在常温和高温下的力学性能。两种体系修复后测试结果表明,高温修复(同质修复)和中温修复(异质修复)对损伤构件的性能恢复差异较小,但是由于同质修复工艺性差,固化温度高于177℃,容易造成其他构件的损伤,而异质修复工艺性较好、固化温度低,所以采用异质修复工艺能够实现对损伤构件的性能恢复,且适合于外场快速修复。     

高性能复合材料弯曲疲劳性能研究

用湿法缠绕技术制作了CF／5228预浸料,对热压罐固化的CF／5228复合材料的力学性能和弯曲疲劳性能进行了研究,并用扫描电镜、电子显微镜等对复合材料的疲劳损伤机理进行了微观表征和理论探讨。研究表明,M40J／5228复合材料比M40／5228具有更为优异的耐疲劳性能。复合材料的疲劳损伤主要有纤维断裂、基体开裂和界面剪切破坏3种表现形式,通常复合材料构件的疲劳破坏多为3种形式的综合表现。基体增韧、选用高强高模碳纤维、界面强化和铺层优化是提高复合材料构件耐疲劳性能有效手段。     

发射过程中某硝胺发射装药的动态挤压破碎情况

利用发射装药动态挤压破碎试验装置对发射过程中低温、常温、高温发射装药的挤压破碎情况进行了模拟动态挤压破碎试验,用发射装药起始动态活度比确定了多种试验条件下破碎发射装药的起始动态活度比,可定量表征发射装药的破碎程度。结果表明,该发射装药在常温、高温下力学性能较好,低温时在相应力学环境下破碎严重。根据试验结果,建立了最大挤压应力与装药破碎程度之间的定量关系。     

水工混凝土结构裂缝的稳定性分析

对于带缝运行的水工混凝土结构,裂缝的稳定性直接关系到整个结构的安全状况.针对水工混凝土结构中裂缝扩展的稳定性问题,主要从断裂力学的角度,以缝端应力强度因子为特征参数,结合某重力拱坝,讨论了裂缝稳定性随水压、温度以及二者的不同组合的演变过程,分析了裂缝的转异特征.对该重力拱坝,水位对应力强度因子的影响较小,裂缝的稳定性主要受温度变化的影响.低温较低水位对裂缝的稳定最为不利,高温低水位对裂缝的稳定性也有一定的影响.还讨论了裂缝的时间效应和转异特征.     

高压蒸汽管帽开裂失效原因分析

对高压蒸汽管线上管帽开裂失效问题进行分析与测试,经过整体、内外壁、断口宏观检查,及微观金相组织、硬度检测,排除了超低温条件脆断、高温损伤石墨化脆断、晶间腐蚀脆断、应力腐蚀开裂,最终分析管帽开裂原因是热疲劳所致,针对失效原因提出相应的整改措施。     

塑料管道失效分析及寿命预测的研究进展

综述了慢速裂纹增长（SCG）和快速裂纹增长（RCP） 2种常见的塑料管道失效模式,详细阐述了塑料管道的失效机理及寿命预测方法,线弹性断裂力学、标准外推法、弹塑性断裂力学、银纹机理等,并分析了各方法的局限,指出了塑料管道寿命预测理论还不成熟,方法还不完善,有待进一步研究。     

Adhesive Fracture Energies of Some High Performance Polymers

A fracture mechanics approach was applied to determine the adhesive fracture energy of various high performance polymers. These polymers, including both thermosetting and thermoplastic materials, generally offer higher temperature capability than conventional epoxies. Double tapered cantilever beam specimens were used for fracture tests at both room temperatures and 225°C. The adhesive fracture energies of a tetrafunctional epoxy and a phthalocyanine resin were also determined at low temperatures. Adhesive fracture behavior of polymers at high temperatures was found to depend on polymer glass transition temperature, whereas at low temperatures it was related to secondary relaxation processes in the glassy state.     

Adhesive Fracture Energies of Some High Performance Polymers

A fracture mechanics approach was applied to determine the adhesive fracture energy of various high performance polymers. These polymers, including both thermosetting and thermoplastic materials, generally offer higher temperature capability than conventional epoxies. Double tapered cantilever beam specimens were used for fracture tests at both room temperatures and 225°C. The adhesive fracture energies of a tetrafunctional epoxy and a phthalocyanine resin were also determined at low temperatures. Adhesive fracture behavior of polymers at high temperatures was found to depend on polymer glass transition temperature, whereas at low temperatures it was related to secondary relaxation processes in the glassy state.     

PBX断裂力学行为研究进展

从常用实验方法、细观断裂模式、宏观断裂力学以及动态断裂方面,概述了近年来国内外关于PBX断裂力学行为的研究状况;介绍了PBX宏观和细观断裂特征及表征手段;阐述了细观结构、力学特性、温度和加载率对PBX断裂行为的影响。指出应开展PBX细观微裂纹萌生和扩展、宏观起裂机理研究,及动态加载下PBX裂纹扩展行为研究,建立适合PBX材料特性的复合型断裂准则。附参考文献51篇。     

Notch sensitivity and fracture toughness of concrete

Whether rules based on fracture mechanics or classical mechanics should be used as a basis for design and analysis depends on the notch sensitivity as well as the fracture toughness of the material. Therefore, information about these properties of all structural materials is important. Experiments were undertaken to investigate the notch sensitivity and fracture toughness of concrete with different types, volumes, sizes and strengths of aggregate. The investigation, which was carried out on small flexural specimens with notches of lengths up to 25 mm, indicates that both mortar and concrete are notch sensitive materials although not as sensitive as neat cement paste. If the assumption is valid that the fracture of neat cement paste is governed by the established theory of linear fracture mechanics, however, it appears that this theory is not applicable to small-size members of mortar and concrete. Light-weight concrete appears to have about the same fracture properties as neat cement paste.     

Investigation of Damage Growth in Single Lap Joints of Composite Laminates

In this paper, growths of different types of failures including adhesion, cohesion and delamination for a single lap joint (SLJ) of composite laminates were investigated using three-dimensional geometrically nonlinear finite element analysis and by adopting a suitable modeling technique. A unique damage modeling method called sub-laminate modeling was employed for the modeling of damages of different failure modes so as to avoid the oscillatory stress and displacement fields around the damage front. The strain energy release rate (SERR) parameter was used for studying the damage growth and the individual and total components of the SERR along the various damage fronts are evaluated using the virtual crack closure technique (VCCT) based on the linear elastic fracture mechanics (LEFM) approach. This study reveals: that the opening mode is the dominant mode of the propagation for the adhesion and delamination damages, while the sliding mode is dominant for the cohesion failure; that the cohesion failure grows at a faster rate than the adhesion failure; and that the delamination front entrapped within the overlap region in the top adherend of the SLJ grows faster when the delamination damages are present simultaneously in both the adherends. This is particularly true when the delamination centers are exactly aligned with the overlap ends of the joint.