Recent developments in the understanding of fretting fatigue

Considerable progress has been made in the understanding of fretting fatigue over the last decade. Experiments have become more standardised and carefully controlled and this has provided the data necessary for development of methods for predicting fretting fatigue performance. This paper reviews a number of recent developments, starting with attempts to apply multiaxial initiation criteria to the fretting problem. The importance of the size effect is highlighted and an analogy is made between fretting and notch fatigue. Methods for characterising crack initiation using asymptotic analysis are discussed, together with short crack arrest concepts which provide a means of predicting fretting fatigue limits from plain fatigue data.     

The intrinsic XFEM: a method for arbitrary discontinuities without additional unknowns

A new method for treating arbitrary discontinuities in a finite element (FE) context is presented. Unlike the standard extended FE method (XFEM), no additional unknowns are introduced at the nodes whose supports are crossed by discontinuities. The method constructs an approximation space consisting of mesh‐based, enriched moving least‐squares (MLS) functions near discontinuities and standard FE shape functions elsewhere. There is only one shape function per node, and these functions are able to represent known characteristics of the solution such as discontinuities, singularities, etc. The MLS method constructs shape functions based on an intrinsic basis by minimizing a weighted error functional. Thereby, weight functions are involved, and special mesh‐based weight functions are proposed in this work. The enrichment is achieved through the intrinsic basis. The method is illustrated for linear elastic examples involving strong and weak discontinuities, and matches optimal rates of convergence even for crack‐tip applications. Copyright © 2006 John Wiley & Sons, Ltd.     

大方坯凝固过程鼓肚应变及内裂纹形成的研究

通过建立大方坯凝固过程的传热模型,获得大方坯冷却传热过程的主要凝固参数,在此基础上建立了凝固前沿坯壳所承受的应变模型,讨论了大方坯凝固过程的主要应变及其主要影响因素,并针对实际铸机的设备和工艺状况,计算大方坯凝固过程的鼓肚应变,讨论了具体钢种产生裂纹的可能性.     

Nondestructive testing for crack of tunnel lining using GPR

Lining craze, as a common engineering damage, affects the bearing capacity and the safety of tunnels.To improve the capabilities of the surface crack detection in the tunnel lining, ground penetrating radar(GPR) was employed. The principle and method of GPR for cracks investigation of tunnel lining were expounded. As an application example, some field measurements in order to detect the depth of cracks for the tunnel lining were achieved in a new tunnel. All GPR investigations were made with the antennae of 1 GHz. The cracks of concrete structure were located, and the distributing and depth of cracks are inspected and estimated by GPR. The results of investigation show GPR is accurate and efficient to detect cracks of tunnel lining.     

KNR860C车轮崩裂原因分析

KNR860C车轮在运行过程中发生大块裂损事故。为确定车轮失效原因，对其进行解剖检验分析。踏面酸洗后出现多条横向裂纹，断裂起源于踏面表面，源区微观形貌为沿晶断。通过对缺陷的金相分析，认为，踏面存在的马氏体、球状珠光体组织及热裂纹是长期受到强烈的热影响造成的，断裂源区位于热影响区较深的区域；车轮的崩裂是由热裂引起的。     

Evaluation of Fracture Toughness of Al-Cu-Fe-B Quasicrystal

1　IntroductionTheapplicationsofthequasicrystals (QCs)haveal waysbeenemphasized ,astheyhaveaseriesofunusualphysicalandchemicalproperties (forexample ,highhard ness ,lowsurfaceenergyandfrictionalcoefficient) ,result ingfromitsaperiodicalstructure .Manystudies[1-3 ] indi catedthatmostQCsareverybrittleatroomtemperatureandveryeasilytobefracturedevenifhavingverysmalldeformation .Athightemperature ,Al Cu TMQCs (TM =Fe B ,Cr ,Si)showahighplasticityaftercompressiontesting .ForAl Cu FeQCs ,asm…     

裂纹尖端的位错密度及其应用

本文为弹性断裂力学分析提供了一个新的变量：位错密度．并论证了这一变量在裂纹尖端具有1√r所阶的奇异性．分别给出了三类裂纹问题裂尖位错密度与应力强度因子的关系，对这一变量在数值计算中的应用进行了探讨．     

浅谈现浇混凝土构件非荷载作用裂缝及其控制

对现浇混凝土构件在温度、收缩变形作用引起裂缝的原因进行了分析，提出了在设计和施工中应采取的控制措施。     

22CrMnMo大模数齿轮磨削裂纹的原因与控制措施

从磨削过程中磨削热、磨削力、齿面应力状态及磨削之前的渗碳淬火工序所得的显微组织等方面，阐述裂纹产生的原因．并提出从磨削工艺上降低磨削温度、从淬火处理上改善齿轮表面应力状态等措施，可有效控制和防止该齿轮的磨削裂纹的产生。     

基于图像处理的路面裂缝特征提取方法

裂缝是一种常见的路面损坏形式,及时、准确地检测和评估路面裂缝的状态,对于路况监测和养护决策具有重要的意义。文章提出了一种基于图像处理的路面裂缝特征提取方法,首先,对分割得到的路面二值图像进行连通域分析,利用裂缝区域和干扰区域之间的特征差异,筛选出真正代表裂缝的连通域;然后,采用改进的快速并行细化算法提取出裂缝骨架,以端点所在分支的长度为标准来去除骨架中的毛刺,针对骨架断裂和向内缩短的问题,通过端点方向以及端点间距离来进行骨架的连接和生长。实验结果表明,该方法能够有效去除分割结果中的干扰区域,提取出清晰完整且无毛刺的裂缝单一像素骨架,较好地反映了裂缝的主要结构和形态特征。