陶瓷材料断裂力学参数的测量方法及选择

本文介绍了陶瓷材料断裂力学参数的定义,并讨论了断裂力学参数的测定方法以及在各种陶瓷应用中这些方法的选择,最后指出,陶瓷材料断裂力学参数的测定能为材料的断裂预报和研制现代陶瓷提供重要的理论基础.     

化工机械设备故障诊断实例

介绍了断裂力学在工程实践中的应用方法，并列举了3个实例证明其实用性和科学性。     

聚乙烯耐蠕变开裂的断裂力学实验方法与聚合物长时标开裂试验装置

介绍了按断裂力学原理设计的实验方法及其数据处理要点，以及按断裂力学原理设计的聚合物长时标开裂试验装置和ＰＥＳＣ－１型高分子材料环境应力开裂速度测定仪的设计要点和参数，该仪器的布置有１０个工作位，使用予制单边切口平板拉伸样条，用断裂力学参数－应力强度因子表征有裂纹样条的载荷；用光学显微镜追踪检测裂纹演化过程的细微变化并可拍照，可有目的地变化载荷和试验温度Ｔ，进行测试，初始应力强度因子Ｋ１０范围为０．     

有限元法在输油管道断裂失效分析中的应用

断裂力学是在生产实践中产生和发展的,是最近才发展起来的一门新兴学科。它应用力学成就,研究含缺陷材料和结构的破坏问题。由于它和材料或结构的可靠性直接有关,因此尽管它出现的时间很短,但实践和理论均有迅速的发展,并已开始为生产服务。断裂力学就是从材料或构件中存在宏观裂纹这一点出发,应用弹性力学和弹塑性力学理论,研究材料或构件中裂纹产生和扩展的条件及规律的学科。     

断裂力学方法在橡胶复合材料疲劳研究中的应用

综述断裂力学方法在橡胶复合材料中的应用现状,着重介绍了撕裂能理论在预测疲劳裂纹增长速率以及预报疲劳寿命方面的应用。     

断裂力学的形成发展与应用

通过对断裂力学形成过程和形成原因,来源于生产实践,又指导生产实践的辩证关系等进行分析,说明科学技术进步与社会生产实践相辅相成的辩证关系,阐述断裂力学的发展与工程实践是密切相关的基本观点,并按照断裂力学发展的成熟度,简要介绍了线弹性断裂力学、弹塑性断裂力学等经典断裂力学的基本理论。     

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。     

分离器缺陷评定

应用压力容器缺陷评定规范《CVDA-84》，对该容器的超标埋藏缺陷进行了断裂力学分析。     

炭黑补强NR硫化胶疲劳破坏特性的研究

用断裂力学方法研究炭黑N110，N220和N330补强NR硫化胶的疲劳破坏特性。结果表明，随着疲劳时问的延长，3种炭黑补强硫化胶的拉断形变能密度均减小，且炭黑粒径越小，硫化胶的拉断形变能密度降幅越大；炭黑粒径越小的硫化胶内部潜在缺陷越小，但抗裂纹扩展性能越差，疲劳寿命越短；3种炭黑补强硫化胶的疲劳寿命方程均能较准确地预测其疲劳寿命。     

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。     

Application of Wedge Splitting Test in Refractories

1IntroductionRefractory lining is simultaneously subjected to va-rious attacks in service,most of which are thermalshocks,corrosion,mechanical impact and abrasion.The mode of degradation by thermal mechanical impacthas not been thoroughly investigated to …     

The fracture toughness of inorganic glasses

Measuring the fracture toughness (K_Ic) of glasses still remains a difficult task, raising experimental and theoretical problems as well. The available methods to estimate K_Ic are reviewed, with emphasis on their respective advantages and drawbacks. In view of our current understanding, this analysis gives precedence to the SEPB method. The ultimate glass strength, the critical flaw size, and the indentation load for the onset of crack initiation are discussed, in the light of the fundamentals of fracture mechanics and classical background regarding the mechanics of brittle materials. Analytical expressions were further proposed to predict the fracture energy and fracture toughness of glasses from different chemical systems from their nominal compositions. The theoretical values were compared with the experimental ones, as obtained by self‐consistent methods when available. The agreement observed in most cases suggests that measured K_Ic values correspond to the crack propagation regime (as opposed to the crack initiation threshold), and supports previous investigations in glasses and ceramics, which showed that a crack tip is nearly atomically sharp in these materials (but for metallic glasses). Some ideas to design tougher glasses are finally presented.     

Surface Integrity Effects on the Fracture Resistance of Electrical-Discharge-Machined WC–Co Cemented Carbides

The flexural strength evolution for two WC–16 vol% Co cemented carbides, with different mean carbide size, subjected to sequential and upgrading electrical-discharge machining (EDM) is studied. It is compared with the fracture behavior exhibited by a reference surface finish condition, attained through conventional mechanical grinding and polishing using diamond as abrasive. Considering that rupture is related to existing defects, either introduced during sample elaboration or induced by machining, a detailed fractographic examination by scanning electron microscopy is conducted to discern fracture origins. The experimental findings indicate that the flexural strength of WC–Co hardmetals may be strongly affected by EDM, depending on the correlation existing between natural defects, as given by particular microstructural parameters, and EDM-induced flaws. An analysis of the results using a linear–elastic fracture mechanics approach permits one to establish a clear connection between surface integrity and fracture resistance. Quantitative discrepancies between the estimated and the experimentally measured critical flaw sizes for all the EDM-related grades are rationalized through the existence of local residual tensile stresses of considerable magnitude at the shaped surface. Release of these stresses through final mechanical and annealing treatments is pointed out as a quite effective alternative for improving the fracture behavior of WC–Co cemented carbides shaped by EDM.     

Fracture Analysis of the Constrained Blister Test

The constrained blister test is analyzed in the framework of linear elastic fracture mechanics. Exact results for the energy release rate and the mode mixedness are obtained as functions of quantities which are natural to measure in the test. Effects of geometrical non-linearities and initial in-plane stresses are included. An analysis of the range of loads for which the test results in configurationally stable delamination is performed.     

Thermodynamics of a Stable Blister Delamination at Elevated Temperature

A new blister test using thermal expansion of an internal working gas trapped at a dissimilar interface between a thin polymer coating and a rigid adherend is developed to measure the adhesive strength at elevated temperature. The blister dimensions are measured by a thermomechanical analyser (TMA) and an optical microscope as a function of temperature. The thermodynamics is presented based on both linear elastic fracture mechanics and the ideal gas law.     

Application of adhesively bonded single lap joints for fracture assessment of adhesive materials

In this study, a method has been proposed to obtain the failure envelope of brittle adhesives using the experimental failure loads of precracked single lap joints (SLJs). The proposed technique is based on the principles of linear elastic fracture mechanics (LEFM), on J-integral relations, and on results of a numerical analysis. Compared to the previous approaches, the introduced experimental method has some advantages such as low manufacturing costs and simpler test procedure. The proposed method can also provide a wide range of mode mix ratios without the need of an additional apparatus. The fracture envelope obtained from the proposed method was then verified by performing some fracture tests including double cantilever beam (DCB), end-notched flexure (ENF), and single leg bending (SLB) specimens. Good correlation was seen between the fracture envelopes of the proposed method and the ones obtained from the fracture mechanics experiments.     

基于非线性黏弹性理论的含缺陷PE管的脆性破坏

现阶段聚乙烯管道脆性破坏失效研究,多采用线弹性断裂力学理论进行分析,鲜有考虑管材非线性黏弹性力学行为.针对这一问题,基于非线性黏弹性理论,将材料黏弹性参数用Prony级数表示,在适当假设简化下推导了变栽荷含缺陷黏弹性体能量释放率的一般表达式.结合含轴向表面裂纹PE管的脆性破坏工程案例,给出其理论模型及相应计算结果,为研究PE管道脆性断裂现象提供理论依据.     

Assessment of temperature-dependent fracture behavior with different fracture mechanics concepts on examples of unoriented and cold-rolled polypropylene

Applicability of different fracture mechanics concepts, including linear elastic fracture mechanics (LEFM), equivalent energy concept, and elastic-plastic fracture mechanics (EPFM), to assessing the temperature-dependent fracture behavior was compared using examples of an unoriented and a cold-rolled polypropylene under quasistatic and under dynamic loading. Under quasistatic loading, the fracture toughness values were determined from the recorded load versus load-line displacement curves on compact tension (CT) specimens. Fracture toughness values under dynamic loading were determined from the recorded load versus deflection curves on single edge-notched bend (SENB) specimens. In spite of its simplicity as an engineering design parameter, on the basis of the LEFM concept, the stress intensity factor K can only be validly used in a limited temperature range. Instead, the EPFM parameters (i.e., the J integral and the crack opening displacement (COD) concepts) can be applied over a wider temperature range. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1237–1249, 1997     

Modelling of the strength–porosity relationship in glass-ceramic foam scaffolds for bone repair

Foam-like glass-ceramic scaffolds based on three different glass compositions (45S5 Bioglass and two other experimental formulations, CEL2 and SCNA) were produced by sponge replication and characterized from morphological, architectural and mechanical viewpoints. The relationships between porosity and compressive or tensile strength were systematically investigated and modelled, respectively, by using the theory of cellular solids mechanics or quantized fracture mechanics. Models results are in good agreement with experimental findings, which highlights the satisfactory predictive capabilities of the presented approach. The developed models could contribute to improve the rational design of porous bioceramics with custom-made properties. Knowing the scaffold recommended strength for a specific surgical need, the application of the models allows to predict the corresponding porosity, which can be tailored by varying the fabrication parameters in a controlled way so that the device fulfils the desired mechanical requirements.