共查询到19条相似文献,搜索用时 109 毫秒
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LY12CZ铝合金缺口试件在谱载下的疲劳 总被引:3,自引:0,他引:3
进行了LY12CZ铝合金缺口试件常幅加载和战斗机宽带随机加载疲劳试验。分别用确定性方法和疲劳谱分析方法估算宽带随机载荷下的疲劳寿命。在确定性方法中比较了峰值计数法、穿零峰值计数法、雨流计数法的差别。在疲劳谱分析方法中比较了窄带累积频次与宽带累积频次法的差别。 相似文献
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本文介绍了用Z—80C档微型机对随机载荷数据进行处理的一个程序:峰谷值计数法和雨流计算法处理程序。并对采样频率、雨流计数法在计算机上的实现方法以及无效幅值的舍去等问题进行了讨论。 相似文献
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一种新的随机多轴疲劳寿命预测方法 总被引:2,自引:0,他引:2
提出一种多轴随机载荷下的疲劳寿命预测方法。该法首先基于von Mises等效应变和等效应力概念、符号修正公式以及传统的单轴雨流计数法,提出一种多轴随机载荷下的循环计数方法。此法主要针对多轴随机载荷下vonMises等效应变和等效应力历程中的符号丢失问题,建议采用一种符号公式来加以修正,以便于结合单轴雨流计数法对修正后的von Mises等效应变历程进行较为精准地循环计数,从而不仅有利后续疲劳损伤的正确估算,还可使单轴循环计数法能有效地应用于多轴载荷—时间历程。然后分析von Mises等效应变循环内的应变状态,并定义该循环内的临界平面和构造损伤参量的基本参数。最后,将提出的计数方法结合几种常见的临界面多轴疲劳损伤模型以及线性损伤定律,对随机拉—扭加载下的En15R钢薄壁管疲劳试件进行寿命预测验证,预测结果与试验结果吻合较好。 相似文献
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基于二维载荷谱的疲劳寿命估算 总被引:1,自引:0,他引:1
在随机疲劳载荷作用下.应用雨流计数法建立二维疲劳载荷谱,将随机载荷-时间历程处理成以载荷幅值和均值为变量的二维联合概率密度函数:通过建立等幅疲劳中值Su-Sm-N曲面,应用Miner线性疲劳累积损伤理论,提出了基于二维载荷谱的疲劳寿命估算方法?最后,给出了一个具体应用实例,计算结果表明,应用二维疲劳载荷谱进行疲劳寿命计算较一维载荷谱更为合理,具有较好的工程应用价值。 相似文献
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一种随机变化载荷的疲劳损伤累计方法 总被引:3,自引:0,他引:3
讨论随机载荷下构件寿命分析时的一种材料损伤计算方法.与通常采用恒幅数据计算变幅疲劳寿命的循环计数统计方法不同,这里针对载荷变程进行损伤计算.作为更一般性的技术,可以对载荷的任一变化即时计算材料发生的损伤结果.为构件局部材料的寿命分析和裂纹行为计算提供一种有效的方法,因为在进行逐个载荷变化的损伤模拟计算时,处于这些部位的应力与构件总体受力情况往往不同,而且与载荷变化的序列有关. 相似文献
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提出一种多轴变幅载荷下基于载荷支配模式的缺口件疲劳寿命预测方法。首先,通过循环计数方法确定多轴变幅载荷历程的计数循环(反复);其次,通过材料的循环应力应变关系和Neuber法推导出虚拟等效应变与真实等效应力之间的关系,并且分别将拉伸型和剪切型Shang-Wang多轴疲劳损伤参数替换虚拟等效应变幅来求解临界面上的真实等效应力幅;然后,通过真实等效应力幅和Neuber法则计算临界面上真实的拉压和剪切等效应变幅,并运用Manson-Coffin方程分别计算缺口部件的拉压和剪切疲劳寿命;最后,选择拉压和剪切疲劳损伤值中的较大值作为每个计数反复的疲劳损伤,并采用Miner法则进行疲劳损伤累积。缺口件多轴疲劳试验结果表明,采用基于载荷支配模式的缺口件疲劳寿命预测方法具有较高的预测准确度。 相似文献
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为探明汽车底盘构件在随机载荷下多轴高周疲劳准则的应用方法与寿命预测规律,以某品牌B级轿车为研究对象,通过采集试验场强化路轮心六分力信号,建立了整车多体动力学模型,应用虚拟迭代法获取转向节与其他零件连接点的载荷时间历程;建立转向节有限元模型,通过模态仿真与试验验证了有限元模型的准确性;提取了von Mises应力下寿命值最小节点的应力分量时间历程;研究了8种高周疲劳准则所基于的3种类型临界平面的计算方法,通过多轴循环计数提取临界面上正应力幅与剪应力幅,并计算不同准则对应的等效应力幅,总结幅值分布与寿命预测规律。研究结果表明,在幅值分布与寿命预测方面,Zhang-Yao准则的等效剪应力幅值整体偏大,预测寿命为1.09×105周次,较其他准则偏于保守;McDiarmid准则的大应力幅仅占3.4%,预测寿命为1.25×106周次,明显大于其他准则的预测寿命值,而改进的McDiarmid准则预测寿命值明显减小。在计算成本方面,von Mises准则无需提取临界面与多轴循环计数,应用最为便捷;Findley准则提取临界面过程需要计算所有平面的正应力与剪应力数据,故计算成本最高。 相似文献
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Hong Chen De-Guang Shang Yu-Jie Tian Jian-Zhong Liu 《Journal of Mechanical Science and Technology》2012,26(11):3439-3446
Based on the cycle counting method of Wang and Brown and on the linear accumulation damage rule of Miner, four multiaxial fatigue damage models without any weight factors proposed by Pan et al., Varvani-Farahani, Shang and Wang, and Shang et al. are used to compute fatigue damage. The procedure is evaluated using the low cycle fatigue experimental data of 7050-T7451 aluminum alloy and En15R steel under tension/torsion variable amplitude loading. The results reveal that the procedure is convenient for engineering design and application, and that the four multiaxial fatigue damage models provide good life estimates. 相似文献
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Predicting the fatigue life of remanufactured centrifugal compressor impellers is a critical problem. In this paper, the S-N curve data were obtained by combining experimentation and theory deduction. The load spectrum was compiled by the rain-flow counting method based on the comprehensive consideration of the centrifugal force, residual stress, and aerodynamic loads in the repair region. A fatigue life simulation model was built, and fatigue life was analyzed based on the fatigue cumulative damage rule. Although incapable of providing a high-precision prediction, the simulation results were useful for the analysis of fatigue life impact factors and fatigue fracture areas. Results showed that the load amplitude greatly affected fatigue life, the impeller was protected from running at over-speed, and the predicted fatigue life was satisfied within the next service cycle safely at the rated speed. 相似文献
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LIFE PREDICTION APPROACH FOR RANDOM MULTIAXIAL FATIGUE 总被引:1,自引:0,他引:1
Wang Lei Wang Dejun School of Mechanical Engineering Automation Northeastern University Shenyang China 《机械工程学报(英文版)》2005,18(1)
According to the concept of critical plane, a life prediction approach for random multiaxial fatigue is presented. First, the critical plane under the multiaxial random loading is determined based on the concept of the weight-averaged maximum shear strain direction. Then the shear and normal strain histories on the determined critical plane are calculated and taken as the subject of multiaxial load simplifying and multiaxial cycle counting. Furthermore, a multiaxial fatigue life prediction model including the parameters resulted from multiaxial cycle counting is presented and applied to calculating the fatigue damage generated from each cycle. Finally, the cumulative damage is added up using Miner's linear rule, and the fatigue prediction life is given. The experiments under multiaxial loading blocks are used for the verification of the proposed method. The prediction has a good correction with the experimental results. 相似文献
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In pulsed optically detected magnetic resonance (ODMR) spectroscopy, a lock-in amplifier is used to monitor the signal which is phase-matched to the duty cycle of an applied sequence of pulses. However, since the desired signals reside atop a much larger amplitude-modulated signal, lock-in amplification methods are difficult to use. Commerically available photon counters are of limited use, because the pulsed ODMR method requires sequential counting over several time intervals, often with minimum time delay between the intervals. The multiaccumulator photon counter described here is capable of such sequential counting over as many as four intervals. The microprocessor which controls the counter algebraically manipulates the photon counts during each of the duty cycles. The result is an inexpensive yet versatile photon counter which is suited for pulsed ODMR and other applications in which sequential counting is necessary. 相似文献