ADI的疲劳性能

发动机曲轴和齿轮的失效形式属于疲劳失效,因此,疲劳性能是应用ADI曲轴、齿轮首先要考虑的性能.根据破坏原因,曲轴的疲劳强度计算应当是计算连杆轴颈圆角处的最大疲劳强度.齿轮的疲劳强度计算则有两种：齿根部弯曲疲劳强度计算和齿面接触疲劳强度计算.球铁的旋转弯曲疲劳强度随抗拉强度提高而增加,但不呈线性关系.奥氏体-贝氏体型球铁的疲劳强度达到或接近部分碳钢、合金钢经调质处理后的疲劳强度.喷丸处理可以提高ADI的各种疲劳强度.为了提高疲劳强度,抗拉强度与伸长率应合理地配合.     

ADI的疲劳强度

论述了ADI的疲劳强度。ADI的疲劳强度优于普通球铁,具有与锻钢相当或比锻钢更好的疲劳强度。表面滚压或喷丸可以进一步增加ADI的疲劳抗力而与气体氮化钢和表面碳化处理钢相匹敌,使ADI完全可以在一定应用中替代碳钢和低合金钢铸件,锻钢件。     

奥贝球墨铸铁的接触疲劳与耐磨性能

结合起重机车辆的工况进行了奥贝球铁机械性能、接触疲劳性能和耐磨性能的试验表明,应用奥贝球铁代替ZG50SiMn制造起重机车轮是可行的.     

水平连铸ADI球铁在工程上的运用

根据铸铁水平连续铸造独特的生产工艺和品质,简要概述了连铸ADI优异的金相特征和机械性能.根据国内及美国、欧洲等国家连铸ADI的各行业大量的应用实例,对未来连铸ADI的工程应用提出美好展望.     

奥贝球铁材料接触疲劳强度的研究

奥贝球铁材料的弹性模量比钢小，因而奥贝球铁齿轮工作时受到的表面接触应力比钢齿轮小。奥贝球铁材料的接触疲劳应力可达1426MPa以上，高于280hp柴油机齿轮的接触应力，因此用奥贝球铁代替调质氮化钢生产280hp柴油机齿轮是完全可能的。     

奥贝球铁齿轮弯曲疲劳强度的试验研究

对各种状态的奥贝球铁齿轮的弯曲疲劳强度进行了试验研究.结果表明：（1）6DF1柴油机奥贝球铁曲轴正时齿轮的弯曲疲劳强度完全能满足设计要求,安全系数可达3.56倍.（2）适当减小齿轮与曲轴的热套过盈量有利于提高奥贝球铁齿轮的极限弯曲疲劳载荷;本试验的奥贝球铁齿轮齿根脱碳层未磨掉的比齿根脱碳层磨掉的极限弯曲疲劳载荷反而高,且其效果比减小齿轮热套过盈量更明显.（3）喷丸强化能使奥贝球铁齿轮极限弯曲疲劳载荷提高31.7%～47.6%.     

等温淬火球墨铸铁的等淬工艺及其壁厚敏感性

本文研究了奥氏体－贝氏体等温淬火球墨铸铁（以下简称ＡＤＩ）等淬工艺对组织、性能的影响,得到了各项力学性能指标所对应的工艺参数;对２０ｍｍ－５０ｍｍ范围试样壁厚敏感性进行了试验,认为通过控制合金成分、球化、孕育、等淬工艺可使断面组织均匀、齐一性好,并作了理论分析。     

铸造镁合金疲劳研究现状

归纳了典型铸造镁合金的疲劳强度和疲劳寿命研究现状,介绍了铸造镁合金疲劳裂纹的萌生及扩展机制,以及基体组织、晶粒尺寸、第二相、铸造缺陷和工作环境等多种因素对镁合金疲劳性能的影响规律,总结了提高镁合金疲劳性能的方法,最后对铸造镁合金疲劳方面的研究进行了展望。     

热处理对AE42压铸镁合金低周疲劳行为的影响

研究了固溶+时效处理(T6)对AE42压铸镁合金在疲劳加载条件下的循环应力响应行为、疲劳寿命以及断裂行为的影响。结果表明,压铸态和固溶+时效态的AE42镁合金均表现为循环应变硬化,固溶+时效处理可导致AE42压铸镁合金的循环应力幅有所提高,并可有效提高AE42压铸镁合金的疲劳寿命。疲劳断口形貌观察结果表明,疲劳裂纹萌生于疲劳试样的表面,并以穿晶方式扩展。     

半固态流变压铸铝合金件疲劳性能研究

对比研究了液态压铸和半固态流变压铸对ZL114A铝合金铸件疲劳性能的影响。结果表明,半固态流变压铸件相较于传统液态压铸件疲劳性能更好而且更稳定。液态压铸件的疲劳寿命主要受孔洞尺寸影响,孔洞尺寸越大,疲劳寿命越低。半固态压铸件的疲劳寿命主要受密度(孔隙率)影响,与密度成正比。半固态压铸ZL114A铝合金试样在密度大于2.62g/cm^3时,疲劳性能表现良好。在70MPa应力下,疲劳寿命可达107次。液态压铸件裂纹萌生于大的气缩孔,半固态压铸件的裂纹萌生是于中心缩松多孔的综合作用结果。     

Influence of casting defects on fatigue behaviour of A356 aluminium alloy

Abstract

The fatigue behaviour of A356 cast aluminium alloy under 10⁴ cycles was investigated by a servo-hydraulic machine at the temperature of 150°C. The specimens for the fully reversible tension compression tests were cut from cylinder head castings of automobile engines. The testing data were treated by S–N curve and the staircase method and the mean values of fatigue property coincided with each other by these two methods, though the data scattered with different casting defects. The fracture surfaces of fatigue specimens were examined by OM, SEM and EDS. It was found that in most of the specimens two or more fatigue crack initiations appeared at a fracture surface. Compared with casting defects such as oxide film, inclusion and blowhole, shrinkage porosity is more detrimental to the fatigue behaviour of aluminium alloy castings.     

压力对Al-5.0Cu-0.4Mn合金疲劳塑性应变能的影响

采用低周疲劳性能测试研究了不同压力对Al-5.0Cu-0.4Mn合金低周疲劳塑性应变能的影响。结果表明,不同压力下挤压铸造Al-5.0Cu-0.4Mn合金的塑性应变能密度均随着循环周次的增加而减小,并且压力越大,合金的塑性应变能密度下降的幅度越大;合金的塑性应变能密度跟循环应变幅的大小相关,同一应变幅下,压力下成形的合金塑性应变能密度更大;压力下塑性应变能密度差别在低寿命区比高寿命区大;压力越大,合金抵抗低周疲劳破坏的能力越好。     

基于ANSYS的液压矫直机机体的疲劳及模态分析

主机机体是液压矫直机的重要部件,为了缩短开发周期,降低生产费用,有必要在设计阶段对其工作寿命和动态性能进行分析评估。首先应用Solid Works建立矫直机主机机体的三维模型,然后将其导入ANSYS Workbench中进行疲劳分析。得到主机机体在脉动载荷作用下的疲劳寿命、损伤和等效交变应力。对机体进行模态分析,得到前六阶的固有频率和振型。分析结果显示机体结构满足疲劳设计寿命的要求;固有频率远高于矫直机的工作频率,矫直动作平稳;在砧座位置及机体转角位置易产生疲劳失效,应在下一步的设计中改进优化。     

Fatigue behaviour of dissimilar friction stir welds between wrought and cast aluminium alloys

Wrought aluminium alloy, A6016-T4, was welded to cast one ADC12 by a friction stir welding technique. A6016 was set on the advancing side, while ADC12 was on the retreating side based on the pre-tensile test results. The dissimilar welds exhibited lower fatigue strengths than A6016 but higher than that of ADC12. Fatigue strengths increased when the tool was offset into ADC12, which could be explained based on the risk volume concept. When ADC12 was set on the advancing side, the fatigue strengths decreased. Microstructural observation revealed that the macroscopic structure in the stir zone drastically changed by putting ADC12 on the advancing side, and insufficient mixing of dissimilar alloys resulted in the lower fatigue strengths.     

Fatigue behaviour of low temperature carburised AISI 316L austenitic stainless steel

Low temperature carburising (LTC) was applied to AISI316L austenitic stainless steel and its effect on microstructure and fatigue behaviour was investigated. LTC treatment enhances surface hardness and wear resistance of the steel without reducing its corrosion resistance. Surface hardness up to 1150 Vickers was achieved in the carburised layer, thanks to the formation of the so-called “S-phase”, a carbon-supersaturated austenite phase. The XRD evaluation of treated material verified expanded austenite with no evidence of carbide precipitation. Rotating bending fatigue tests showed that the low temperature carburising treatment enhances the fatigue strength of the 316L steel by 40% with respect to the untreated material due to the high residual stresses present in the treated layer. A major temperature increase was found testing the LTC specimens, with a peak value at the end of the test up to 600 °C. By air cooling the LTC specimens during the tests, a further increase of fatigue strength up to 70% was achieved with respect to the untreated material. Fatigue cracks in the surface-treated specimens always nucleated near the boundary between the carburised case and the core.     

Fatigue crack growth behaviour of pulsed current gas tungsten arc, friction stir and laser beam welded AZ31B magnesium alloy joints

The laser beam welded joints offered better resistance against the growing fatigue cracks compared to friction stir welded and pulsed current gas tungsten arc welded AZ31B magnesium alloy joints. The formation of very fine grains in weld region, higher fusion zone hardness, uniformly distributed fine precipitates and favourable residual stress field of the weld region are the main reasons for superior fatigue performance of laser beam welded joints of AZ31B magnesium alloy.     

Effect of HIP Treatment on Fatigue Notch Sensitivity of Ti-6Al-4V Alloy Fabricated by Electron Beam Melting

The effect of hot isostatic pressing(HIP)treatment on the fatigue notch sensitivity of Ti-6A1-4V alloy fabricated by electron beam melting(EBM)was investigated.The results indicate that the fatigue notch sensitivity of the as-fabricated samples is much lower than that of HIPed samples.The variation of α lamella thickness and the distribution of pore defects have an effect on the fatigue strength in smooth and notched EBM Ti-6A1-4V samples,resulting in the divergence of the as-fabricated and HIPed samples on fatigue notch sensitivity.