金属材料的断裂准则及断裂行为数值模拟

论述了金属延性断裂形成的机理，介绍了常见断裂准则公式，对获得金属断裂准则的方法进行模型、原理介绍并给出验证。介绍了有限元技术在挤压、金属切削、切断和精冲工艺中断裂行为的成功分析。     

船用钢丝绳断裂失效分析

目的 了解某船用?76mm锚泊定位镀锌钢丝绳累计使用寿命较短、多处出现单丝断裂现象的原因。方法 采用宏观分析、硬度测试、力学性能试验、断口分析、化学成分分析、扫描电镜显微组织观察等方法对该钢丝绳的断裂原因进行分析。结果 拉伸试验断口为杯锥状断口,其放射区面积较纤维区更大,表明材料塑性差,硬脆性大,断口中包含有夹杂,这些因素会导致钢丝发生断裂;试样心部的显微硬度最高,钢丝断裂是从钢丝心部开始产生之后,裂纹向四周开始扩散直至整根钢丝断裂,纤维区硬脆性最大,断裂源位于纤维区。结论 钢丝绳断裂为韧性断裂。实际工况下,钢丝绳断口为劈裂状断口,符合韧性断裂的滑移分离特征,其主要原因是钢丝的屈服强度不能适应工作应力要求从而发生断裂。观察断口发现,断口的放射区面积占比较大,纤维区面积占比小,表明材料塑性差,硬脆性大,断口中包含夹杂,钢丝绳易在此处发生断裂。试样心部的显微硬度最高,距离心部越远,显微硬度越低,可知钢丝绳断裂源是由心部产生的,断裂源位于纤维区。     

8.8级紧固螺栓断裂原因分析

8.8级螺栓在使用过程中发生断裂,通过化学成分分析、力学性能试验、断口形貌分析以及金相检验等方法对断裂螺栓进行了分析。结果表明:失效螺栓的断裂为多源疲劳断裂,主要原因是螺纹表面脱碳层的存在导致构件的抗疲劳性能下降。     

双头螺旋道钉断裂分析

螺旋道钉与轨枕预组装后，在起吊运输过程中(环境温度-15℃左右)用榔头锤击螺旋道钉时，道钉发生断裂。对失效件进行了宏、微观检验、力学性能试验和化学成分分析，同时，对已断裂和未断裂的表面经多元共渗的道钉、表面未经处理的道钉进行了分析对比。结果表明，低温环境下操作和强力组装是导致螺旋道钉断裂的主要原因。     

定向断裂控制爆破机制与生产试验

本文采用动光弹超动态量测技术，在实验室模型试验基础上，优选出定向切缝药包爆破新方法，分析了定向断裂爆破应力场参数和定向断裂爆破机理，并在矿井巷道中进行了正规循环生产试验，证实了巷道定向断裂控制爆破新工艺可取得明显效果，具有广阔应用前景。     

高强螺栓断裂原因分析

对断裂的高强度螺栓断口及其腐蚀产物、螺栓表面存在的微裂纹进行了观察分析；对螺栓材料进行了热处理、氢脆敏感性和力学性能试验。结果表明，引起断裂发生的裂纹源─—微裂纹是Ｃｌ￣－应力腐蚀及氢脆交互作用的结果。断裂螺栓材料变脆是由于时效致使晶界产生铁铬碳化物偏聚引起的。对断口形貌和断裂过程用断裂力学方法提出了解释。     

水工混凝土的损伤模型

本文在混凝土断裂、损伤试验的基础上，提出了一个反映水工混凝土断裂、损伤破坏机理的损伤模型。这个模型在损伤力学有限元分析中具有良好的实用性。     

某仪器舱大套筒开裂失效分析

某仪器舱3个大套筒在振动试验过程中发生断裂,失效分析后认为套筒断裂性质为疲劳断裂;断裂原因是由于材料组织不均匀(存在大量条状析出相),以致套筒经硫酸阳极化后产生了表面腐蚀裂纹;断裂过程为在振动试验过程中表面腐蚀裂纹沿条状析出相扩展,导致套筒疲劳断裂.     

某钢芯铝绞线预绞式接头断裂原因分析

某输电线路的钢芯铝绞线预绞式接头在运行过程中发生了断裂。采用宏观分析、断口分析、力学性能试验等方法对接头的断裂原因进行了分析。结果表明:该预绞式接头断裂位置处于外绞丝与绞线钢芯之间形成的环形空腔处,线路运行过程中,环形空腔位置处的外绞丝吸收导线振动能量,长期振动后发生了疲劳断裂。外绞丝断裂后,接头位置电阻骤增,温度异常升高,使得钢芯强度显著降低,最终导致接头拉伸断裂。     

石材爆破的断裂控制原理及措施

首先论述了石材爆破的定向断裂控制基本原理和实施方法，然后介绍了石材爆破的破坏性断裂类型及预防措施。     

实用断裂试验方法的意义与内容（一）

为了在材料性能检测中普遍、持久地应用断裂试验，推荐一种延性材料断裂韧性实用测试方法。该实用测试方法包括侧切三点弯曲试件、测量δｃ的两点位移法和测量ＪＩＣ的位称计法。该方法具有科学合理、通谷易懂、准确可靠、简便快捷、费用低廉等显著特点，适合普遍推广应用。     

A status report on delamination resistance testing of polymer-matrix composites

The development of fracture mechanics test methods for the determination of delamination resistance or fracture toughness of fiber-reinforced, polymer-matrix composites is an active area of research. The emphasis in this review is on standardisation of test methods. Recent developments leading towards new standardized test procedures will be presented, complementing and updating earlier reviews.     

Experimental investigation on test methods for mode II interlaminar fracture testing of carbon fiber reinforced composites

In this paper, experimental investigation on the test methods for mode II interlaminar fracture testing of carbon fiber reinforced composites are carried out. Mode II interlaminar fracture testing of unidirectional composite of carbon fiber reinforced epoxy (T800/#3631) are conducted using four kinds of test methods, namely end notched flexure (ENF) test, end loaded split (ELS) test, four-point bend end notched flexure (4ENF) test, and over notched flexure (ONF) test. An analytical model based on a point-friction assumption and classical beam theory is proposed to evaluate the effect of friction between crack faces on the mode II interlaminar fracture toughness in the 4ENF and ONF tests. The analytical model is validated by the comparison of analytical results with previous ones obtained from finite element analysis. Experimental results show that the ENF test gives reliable initiation value of fracture toughness with a small scatter and that the average value of fracture toughness obtained from 4ENF test is about 2% higher than that obtained from the ENF test. The effect of friction in the 4ENF test is much lower than that in the ONF test in which the effect of friction increases with the crack growing. It is concluded that the 4ENF test method is an effective test method for the experimental evaluation of mode II propagation interlaminar fracture toughness of carbon fiber reinforced composites.     

CF-62钢焊接接头断裂韧性分布的试验研究

对ＣＦ－６２钢焊接接头Ｊ－Ｒ阻力曲线和断裂韧性Ｊ１Ｃ进行了８测试，并用参数假设检验及概率级等方法，对试验结果进行了分析和检验，得到了Ｊ１Ｃ的分特征值，为高强钢焊接接头断裂韧性的测试方法提供了依据。     

Ni—Ti—Nb宽滞后形状记忆合金焊接环拉伸断裂分析

研究了Ni—Ti—Nb宽滞后形状记忆合金点焊环拉伸试验的断裂行为。对形状记忆合金环的断口形貌及微区成分用扫描电镜作了分析,得出了形状记忆合金环中的（Ti,Nb）2Ni硬脆相是导致断裂的主要原因。并分析了（Ti,Nb）2Ni硬脆相形成的原因,提出了利用多次电弧炉熔炼和热变形工艺的方法来提高记忆合金冶金质量的建议。     

The fracture of bulk metallic glasses

The fracture of metallic glasses has received relatively little attention until recently. The development of bulk metallic glasses (BMGs) with more compositions, large sample sizes and diverse fracture behaviors provides a series of ideal model systems for the study of fracture in glassy materials. The fracture toughness of different BMGs varies significantly from approaching ideally brittle to the highest known damage tolerance. Diverse fracture patterns on the fracture surface, fracture modes and dynamic propagation of cracks have been observed in different BMGs. In this review paper, we present a comprehensive view of the state-of-the-art research on various aspects of the fracture of BMGs, including fracture behavior and characteristics, fracture mode, fracture criterion, fracture toughness, and fracture morphology. Accumulated experimental data on BMG fracture are presented and their possible theoretical connections with continuum fracture mechanics and the atomic-scale process are introduced and discussed. Modeling studies of the fracture of BMGs by various computational methods are also reviewed. The review also presents a number of perspectives, including the relation of BMG fracture study to other topics, and unsolved issues for future investigation.     

Temperature effect on fracture behaviour of an alumina particulate-reinforced 6061-aluminium composite

The effect of temperature on the fracture behaviour of a peak-aged alumina particulate 6061 aluminium composite was studied in the range of 25 to 180° C. The fracture toughness was found to be independent of test temperature. The role of the reinforcement phase was examined in detail at 180° C, and compared to observations at room temperature, by using an interrupted test methodology. Ductile fracture occurred at all temperatures. At room temperature the fractured particles acted as void nucleation sites and at 180° C both debonded and fractured particles were responsible for void nucleation. Large particles were found to be susceptible to fracture and nucleate microvoids earlier than small particles. A decrease in the range and size of the reinforcement phase would increase the fracture resistance for this MMC material.On leave at the Department of Mechanical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.     

Micromechanical modeling of damage and fracture of unidirectional fiber reinforced composites: A review

An overview of methods of the mathematical modeling of deformation, damage and fracture in fiber reinforced composites is presented. The models are classified into five main groups: shear lag-based, analytical models, fiber bundle model and its generalizations, fracture mechanics based and continuum damage mechanics based models and numerical continuum mechanical models. Advantages, limitations and perspectives of different approaches to the simulation of deformation, damage and fracture of fiber reinforced composites are analyzed.     

混凝土、岩石类损伤材料宏观断裂模型及应用

本文研究了混凝土、岩石类损伤材料的宏观断裂模型。文中从损伤材料中微裂纹等缺陷的拉裂扩展过程,研究宏观断裂的形成与发展,并由此建立了相应的本构关系和断裂判据。文中对此模型用地质力学模型试验作了验证。最后将其应用于某水电站建基面外移方案可行性研究中。