Mn13铸件开裂及早期破损的分析

针对Ｍｎ１３铸钢件出现铸造开裂和使用寿命低，形成早期破损等问题，通过化学分析，金相组织检验等手段，从冶炼，铸造和水韧处理三方面对该钢的质量问题进行了全面分析，认为Ｍｎ１３铸件出现开裂的主要原因是由于化学成分控制不全理、Ｍｎ含量偏低，降低了钢的冲击韧性以及在熔炼脱氧过程中控制不严，造成铸造基体形成大量的氧化物夹杂且沿晶分布，增大了开裂的敏感性，另外，水韧处理温度低或保温时间不足，成品铸件未能获得单一     

制动器防尘罩冲压开裂CAE分析

某零件公司冲压"制动器防尘罩"零件,材质切换过程中发生板材不适用的情况,文章通过两种模式对照计算的方式,准确表达板料恶化趋势,并通过模拟分析给出性能调整方向,提高抗拉值并优化表面微观形貌以改善摩擦系数,使后续供货使用性能得到改善,用户反馈良好.     

连铸板坯纵向开裂成因分析

本文通过对连铸板坯纵向裂纹进行组织观察、裂纹扩展及材料热模拟试验，结合实际生产工艺，分析了板坯纵向裂纹产生的原因，提出了改善板坯纵向裂纹的措施。     

ML08Al冷镦开裂原因分析

冷镦钢ML08Al加工零件时的失效方式多种多样,较为常见的失效模式为零件开裂.零件冷镦开裂可能与加工有关,也可能与原材料有关,从生产实践看主要原因多为划伤所致.文中经分析找到了某型皮带螺母的开裂原因,并提出应对措施,有效避免了开裂情况的发生.     

50带钢开裂缺陷分析

鄂钢50热轧窄带钢经用户冷轧后,出现了较严重的开裂缺陷。通过金相显微镜、扫描电镜和能谱分析仪的观察,并结合50热轧窄带钢的生产工艺以及用户的加工工艺进行了分析,结果表明:原材钢质不纯净和用户酸洗时氧化铁皮未洗净是造成50热轧窄带钢出现开裂缺陷的主要原因。     

GCr15轴承钢轧件开裂原因的分析及解决方法

从化学成分、力学性能、金相组织等方面对Gcr15轴承钢轧件开裂原因进行分析,并提出了相应的解决措施.     

任意点置镜一站设同心曲线

介绍了一种可在任意一点放样出同心曲线各桩的方案 ,结论严密 ,方法简便 ,检核得力 ,适用性     

钛铝金属间化合物的氢致开裂

对了Ti₃Al+Nb金属间化合物,用预裂纹试样研究原子氢引起的氢致开裂。结果表明,无论在室温还是高温(400℃),氢能促进局部塑性变形。当它发展到临界状态时,氢致裂纹就在塑性区中某一特征位置处沿滑移带形核。研究了氢作为暂时合金元素对氢致开裂门槛值K_IH和断裂韧性K_IC的影响。还研究了氢化物含量对氢致开裂门槛值K_IH的影响。根据氢促进局部塑性变形从而促进解理断裂的理论导出了K_IH的定量表达式。     

65Mn钢板开裂原因分析

运用扫描电镜、金相检验、力学性能测试等手段,研究了65Mn钢板开裂的原因.结果表明:钢的组织中存在夹杂物(较大)、片状珠光体片间距偏大是导致65Mn钢板开裂的主要原因.通过降低钢中的夹杂物,调整热轧工艺,获得了良好的综合力学性能.     

The mechanisms of crack initiation and crack propagation in metal-induced embrittlement of metals

Metal-induced embrittlement (MIE) of 4140 steel by indium has been studied using delayed failure tensile tests. The temperature and stress dependence of the kinetics of crack initiation and crack propagation in both liquid metal-induced and solid metal-induced cracking have been examined in the same system for the first time in MIE. This was done using electrical potential-drop measurements along the indium-covered portion of the sample gage length to record the start and progress of cracking, and also through fractographic observations. In Part I of the report on this work, the experimental results are presented, and their implications with regard to crack propagation are discussed. In Part II, various mechanisms proposed in the literature for crack initiation are evaluated in the light of the experimental results and other known characteristics of MIE. It is concluded that crack initiation in the embrittlement of 4140 steel by indium can best be explained by a mechanism involving stress-aided embrittler diffusion penetration of the base-metal grain boundaries, and it is suggested this may also be more generally true. HENRY H. AN, formerly Graduate Student, Illinois Institute of Techogy     

疲劳裂纹萌生尺寸确定方法研究

以缺口件为研究对象 ,根据J积分理论 ,对Dowling法进行了改进 ,并根据疲劳非扩展裂纹的性质 ,给出裂纹萌生尺寸的定义 ,介绍疲劳裂纹萌生尺寸的确定方法     

GB/T17990-1999圆钢点式(线圈)涡流探伤检验方法编制说明

通过使用点式涡流探伤检验方法,能够检验出圆钢的表面和近表面缺陷,并与人工缺陷相比较,判定被检验的产品是否符合标准要求.     

The iron fusion curve and γ-δ-l triple point

The pressure-temperature lines for iron γ-δ and δ-liquid equilibria have been determined using improved methods for internal pressure measurement and improved thermocouple pressure error correction data. The experimental results indicate slopes for the γ-δ equilibrium of 6.3 ± 0.1° per kbar and for the δ-liquid equilibrium of 3.5 ± 0.1° per kbar. The γ-δ-liquid triple point was found at ∼1718°C, ∼52 kbar. A 5 kbar section of the γ-liquid line indicated a γ-liquid line slope of 3.85 ± 0.15° per kbar.     

A point defect model for fatigue crack initiation in Ni3Al+B single crystals

Transmission electron microscopy of boron-doped Ni₃Al single crystals, oriented for single slip and cyclically deformed at room temperature, revealed a high density of dislocation dipoles and point defect clusters. Observations of circular perfect dislocation loops, Frank loops, vacancy tetrahedra and spherical voids provide evidence of vacancy condensation during fatigue cycling at room temperature. It is suggested that lattice misfit develops between persistent slip bands (PSB) and matrix as a result of the generation and coalescence of excess vacancies in PSBs. The misfit strain at PSB/matrix interfaces is considered to increase with increasing cumulative plastic strain. Together with SEM observations of surface topography, it is suggested that fatigue damage in Ni₃Al single crystals is initiated by the formation of microvoids (microcracks) at PSB/matrix interfaces. The microvoids (microcracks) break down the coherency of the PSB/matrix interfaces and thereby relieve the accumulated misfit strain at the interfaces. A model of fatigue crack initiation based upon a surface energy criterion is proposed.     

A study of subsurface crack initiation produced by rolling contact fatigue

Results of subsurface crack initiation studies produced by pure rolling contact fatigue in 7075-T6 aluminum alloy are presented in this article. Microstructural changes and subsequent crack initiation below the contacting surface in cylindrical test specimens subjected to repeated rolling contact are illustrated. The rolling conditions are simulated in a three-dimensional elastic-plastic finite element model in order to estimate the plastic strains and residual stresses in the test material. The numerically estimated distribution of plastic strains in the model correlate well with the extent of microstructural changes observed in the test specimen. Results also indicate that a combination of plastic strains and low values of residual stresses is conducive to subsurface crack initiation and growth.     

氢致钢内部疲劳裂纹萌生和扩展的有限元分析

对氢致钢内部疲劳裂纹的萌生和扩展进行了数值模拟.首先用有限元法分析了氢在疲劳载荷作用下向钢中缺陷处扩散富集的过程,然后计算得到氢含量分布结果.根据夹杂理论将氢富集区视为在缺陷附近分布的弹性夹杂,用有限元法计算得到的氢含量场求出夹杂处的应力强度因子,进而建立疲劳裂纹萌生和扩展的判据.比较了在不同加载条件下氢致疲劳裂纹萌生和扩展的规律.用梯形法修正了Sofronis和McMeeking的瞬态扩散有限元公式,发现用梯形法可以缓解加载初期较高的浓度梯度和应力梯度引起的计算结果震荡的情况,这对于计算开裂判据是十分重要的.最后讨论了提高模拟精度和改进模型的方法.     

A theory of fatigue crack initiation at inclusions

The dislocation dipole accumulation model for fatigue crack initiation previously proposed by the authors is extended to an analysis of the fatigue strength reduction due to inclusions in high strength alloys. The initiation of a fatigue crack is determined by an energy criterion under the assumption that the crack initiation takes place when the self strain energy of dislocation dipoles accumulated at the damaged part in the material reaches a critical value. Explicit formulae for the crack initiation criterion in several cases are derived as functions of the applied stress, the inclusion size, the slip band shape, and the shear moduli of the inclusion and matrix. The following three types of fatigue crack initiation at inclusions are considered: the slip-band crack emanating from a debonded inclusion, the inclusion cracking due to impinging of slip bands, and the slip-band crack emanating from an uncracked inclusion. The first mechanism was reported to be operative in high strength steels, while the last two mechanisms were reported in high strength aluminum alloys. The present theoretical results are in good agreement with the experimental data published for each case of fatigue crack initiation at inclusions.