共查询到17条相似文献,搜索用时 156 毫秒
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对带有两个焊点的拉剪点焊试样进行了两级变幅疲劳加载,应力幅和平均应力均不相等.结果表明,两级变幅加载下存在应力次序效应.在低—高加载时存在"锻炼效应",线性累积损伤的值大于1;在高—低加载时存在"过载效应",高—低加载下的线性累积损伤值也大于1.在高—低加载方式下,高水平应力作用后,低水平应力剩余疲劳寿命大于按线性疲劳累积损伤法则所估算的剩余寿命,低应力作用下的剩余寿命甚至大于低应力单独作用下的全寿命.高—低加载下的线性累积损伤结果表明,焊点边缘更象是一个缺口. 相似文献
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不同工况下TC4(Ti-6Al-4V)钛合金疲劳累积损伤及强度退化存在较大差别。为了充分表征载荷参数的影响,基于Chaboche损伤模型以及改进的多轴疲劳损伤准则,提出新的强度退化模型,开展了TC4钛合金的多轴高周疲劳(HCF)寿命预测和强度退化评估。首先,开展TC4合金在一系列加载路径下的多轴比例和非比例疲劳试验。将Chaboche非线性损伤准则和临界平面法与提出的损伤控制参数相结合,描述了TC4合金的非线性疲劳损伤计算和寿命预测。其次,进一步建立了基于累积损伤的非线性强度退化模型,并证明了该模型在不同载荷工况下均可以获得更高的精度。实验结果表明,由于考虑载荷参数的影响,提出的TC4钛合金疲劳寿命与强度退化预测结果精度远高于其他的预测模型。 相似文献
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使用带超声频载荷分量的双周疲劳试验装置对Q345钢焊接接头分别进行纯低周、纯高周以及双周循环加载条件下的疲劳试验.应力比R为O.5,高周载荷频率约19 kHz.结果表明,叠加于大幅低周循环载荷上的小幅高周循环载荷及叠加于大幅高周循环载荷上的小幅低周循环载荷都能够对焊接接头造成严重的疲劳损伤.通过按外包络线表征双周疲劳强度,如果疲劳寿命使用低周载荷循环周次表征,低估了高周载荷分量对焊接接头造成的损伤;如果疲劳寿命使用高周载荷循环周次表征,又高估了低周载荷分量对焊接接头造成的损伤. 相似文献
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CuW80铜钨合金疲劳损伤过程的研究 总被引:1,自引:0,他引:1
借助扫描电镜研究了CuW80铜钨合金电触头材料在循环载荷作用下微观组织的变化过程,用系统分析的方法定义CuW80铜钨合金疲劳损伤参数,并对其三点弯曲疲劳损伤过程进行了定量跟踪分析.试验结果表明,CuW80铜钨合金疲劳的损伤过程可以分为三个阶段,具有双线性损伤过程的特征,分别对应于疲劳裂纹萌生阶段(EF)和扩展过程(FH)两个线性阶段,且分别占疲劳总寿命的60%和33%;在循环载荷作用下CuW80铜钨合金的疲劳裂纹主要萌生于铜钨合金铜相的晶体内,而非发生于铜、钨界面,并且疲劳裂纹在铜相晶体内不断扩展直至断裂. 相似文献
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Y.Noguchi M.Miyahara 《金属学报(英文版)》2004,17(4):355-360
A new method was proposed for the multiaxial creep-fatigue life evaluation under proportional loadings. Because this method was derived from the strain range partitioning method with a multiaxiality factor, it was possible to consider the influence of both creep-fatigue interaction and multiaxial stress state on fatigue life. In order to predict the combined axial-torsional fatigue life the damage under combined loading was defined as linear summation of the damages under axial loading and torsional loading. Axial-torsional creep-fatigue tests were carried out using tubular specimens of 316LC austenitic stainless steel and the ferritic rotor steel. This rotor steel was developed for the permanent magnet type eddy current retarder in heavy trucks. Experimentally obtained lives of both steels were well corresponded with the lives predicted by the proposed method. It was found that the proposed method was effective in multiaxial fatigue life evaluation under proportional creep-fatigue Ioadings. 相似文献
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Hai-tao HU Yu-long LI Tao SUO Feng ZHAO Ying-gang MIAO Pu XUE Qiong DENG 《中国有色金属学会会刊》2014,24(5):1331-1336
Vibration tests were carried out on three types of stiffened aluminum plates with fully clamped boundaries under random base excitation. During the test, the response of the specimens was monitored using strain gauges. Based on the strain history, the accumulation of fatigue damage of the stiffened plates was estimated by means of the rainflow cycle counting technique and the Miner linear damage accumulation model in the time domain. Utilizing the change of natural frequencies, a nonlinear model was fitted for predicting the fatigue damage of plate and then the foregone failure criterion of 5% reduction in natural frequency is improved. The influence of section and spacing of the stiffeners on the vibration fatigue behavior of the aluminum plate was investigated. The results show that the fatigue life of aluminum plate increases with adding either T or L section riveted stiffeners. With the same cross-sectional area of stiffener, the T section stiffened plate shows longer fatigue life than L section stiffened plate. Meanwhile, the vibration fatigue life also shows great sensitivity to the spacing between the stiffeners. 相似文献
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A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING 总被引:2,自引:0,他引:2
W.X. Yao 《金属学报(英文版)》2007,20(1):65-71
Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted. 相似文献
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The feasibility of the acoustic emission technique in predicting the residual fatigue life of 6061-T6 aluminum matrix composite reinforced with 15 vol.% SiC particulates (SiCp) is presented. Fatigue damages corresponding to 40, 60 and 80% of total fatigue life were induced at a cyclic stress amplitude. The specimens with and without fatigue damage were subjected to tensile tests. The acoustic emission activities were monitored during tensile tests. The number of cumulative AE events increased exponentially with the increase in strain during tensile tests. This exponential increase occurred when the material was in the plastic regime and was attributed mainly to SiC particulate/matrix interface decohesion. Cumulative events during post fatigue tensile tests reduced with a decrease in the residual fatigue life. Based on the high cycle fatigue damage accumulation model, a Weibull probability distribution model is developed to explain the post fatigue AE activity of specimens during tensile tests. Using the model, the residual fatigue life can be predicted by testing the specimen in tension and monitoring the AE events. In high cycle fatigue, it was observed that the residual tensile strengths of the material did not change significantly with prior cyclic loading damages since the high cycle fatigue life was dominated by the crack initiation phase. 相似文献
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采用红外热像法测量AZ31B镁合金板材在疲劳过程中表面温度场的变化,结果表明,当疲劳载荷大于疲劳强度时,镁合金试样表面的温度变化经历5个阶段:温度上升阶段、温度下降阶段、稳定阶段、断裂前的温升阶段和断裂后温度下降阶段。通过疲劳过程中镁合金试样表面的温度变化规律,基于不同的理论提出了2种预测疲劳寿命的方法:由试验过程中试样表面温升(?TM)特征确定其疲劳寿命,?TM–Nf曲线拟合结果表明,?TM=3.89℃为温升极限值,即?TM>3.89℃时,试样会发生断裂,与实测疲劳试样的温升值(3.68℃)相比,误差为5.7%;利用能量法提出了镁合金疲劳寿命的计算公式,用能量法和传统试验方法分别绘制S-N曲线,结果具有很好的一致性,用2种方法分别计算了循环次数为1×107时的疲劳强度ΔσeΦ=99.3 MPa、ΔσeSN=99.8 MPa,误差为0.5%。采用红外热像法估算疲劳寿命具有简单、省时等优势。 相似文献
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《Science & Technology of Welding & Joining》2013,18(5):306-312
AbstractThe influence of weld geometry in conjunction with the gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) processes on fatigue properties of AISI 304L load carrying transverse fillet welded cruciform joints, containing lack of penetration (LOP) defects, has been studied. The fatigue lives of the joints were evaluated using conventional S -N (stress - number of cycles to failure) and fracture mechanics methods. The fatigue lives were calculated according to the two stage approach in which both the fatigue crack initiation and the crack propagation phases were considered. Constant amplitude fatigue experiments with stress ratio R=0 were carried out using a 100 kN servohydraulic Dartec universal testing machine at a frequency of 30 Hz. An automatic crack monitoring system based on crack propagation gauges was used to obtain the crack initiation and propagation data during the fatigue process. The predicted life was compared with the experimental values. It was found that the fatigue lives of the joints fabricated via GTAW were longer than those of the corresponding GMAW joints. It was also observed that the fillet geometry plays a major role in determining the failure mode and life. Test results have been compared with the BS 5400 design curve. 相似文献