共查询到19条相似文献,搜索用时 218 毫秒
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以空气中腐蚀疲劳裂纹扩展速率为基准,引入环境加速因子Cenv,且把Cenv与Cair合并为C,用于表达07MnNiCrMoVDR钢在硫化氢溶液中的腐蚀疲劳裂纹扩展速率。利用Matlab中的神经网络工具箱,以介质浓度、载荷频率、应力比作为输入节点,C作为输出节点,训练该网络预测不同条件下的裂纹扩展速率。根据训练完毕神经网络预测不同条件下的C,利用Original找出这三个影响因素在裂纹扩展速率系数C中的关系表达式,从而由Matlab中的统计工具箱回归出07MnNiCrMoVDR钢在硫化氢溶液中的腐蚀疲劳裂纹扩展速率数学模型。 相似文献
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通过试验测得T851处理的2124铝合金板TL取向与LT取向不同应力比时的裂纹扩展门槛值及裂纹扩展速率;将应力比影响下的有效应力强度因子ΔKeff、有效裂纹扩展门槛值ΔKeffth及裂纹在循环应力作用下的临界应力强度因子K′C引入全范围裂纹扩展速率表达式中,并用修正后的公式对不同应力作用下2124铝合金TL取向与LT取向的疲劳裂纹扩展速率进行了预测。结果表明:预测结果与试验结果基本吻合,说明修正后全范围裂纹扩展速率表达式可以用来描述2124铝合金裂纹扩展速率。 相似文献
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填充天然橡胶材料疲劳裂纹扩模型是指裂纹扩展速率与撕裂能峰值之间的关系,它是用于橡胶减振元件疲劳寿命预测的重要模型。在裂纹扩展试验得到的填充天然橡胶材料裂纹扩展长度与循环次数的数据中,由于橡胶的应力软化现象,试验后期的部分数据不可用。为此,建立了数据处理方法,获得有效的裂纹扩展长度与循环次数数据。基于单轴拉伸载荷下填充天然橡胶材料最大应变能密度与最大应变满足幂函数关系的假设,建立了变幅加载工况下裂纹扩展长度与循环次数的数学模型和识别其模型参数的优化方法。在建立的裂纹扩展长度与循环次数模型的基础上,建立了裂纹扩展速率与撕裂能峰值关系的模型和确定模型中参数的数值方法。利用一组哑铃型试片的疲劳寿命实测数据,对建立的裂纹扩展速率模型进行了验证,证明了所建立模型的正确性。 相似文献
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钢板弹簧疲劳裂纹在变幅载荷作用下的扩展预测模型主要是Schütz疲劳裂纹扩展模型,但此模型未考虑裂纹闭合效应对疲劳裂纹扩展的影响,忽略了参数C和n随应力比的联系,疲劳裂纹门槛值△Kth也只考虑应力比为0的特殊工况.因此对Schütz疲劳裂纹扩展唯象模型进行修正,使修正后的模型各参数物理意义更加明确,适用于不同的工况.并将实车试验所测的应力幅值运用于修正后的模型,表征变幅载荷作用下钢板弹簧疲劳裂纹扩展进程.表明加载幅值增大,疲劳裂纹扩展速率加快,试验结果与模型预测结果良好吻合,为变幅载荷作用下疲劳裂纹扩展速率的计算提供了理论依据. 相似文献
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进行了3种应力水平下2024-T62铝合金的疲劳裂纹扩展试验,利用试验数据对疲劳裂纹扩展的分散性进行了统计分析。分析结果表明:2024-T62铝合金的疲劳裂纹扩展试验数据服从对数正态分布;随着载荷循环数的增加,疲劳裂纹尺寸的标准差和变异系数都增大;试验应力水平对疲劳裂纹尺寸的分散性有一定的影响,随着载荷循环数的增加,高应力水平下疲劳裂纹尺寸的标准差大于低应力水平下疲劳裂纹尺寸的标准差,且高应力水平下疲劳裂纹尺寸标准差与变异系数的增加速度比低应力水平下疲劳裂纹尺寸标准差与变异系数的增加速度快;利用疲劳裂纹扩展试验数据使随机疲劳裂纹扩展模型得到了验证。 相似文献
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A complete life model for the nucleation and growth of a fretting fatigue crack has been developed. The nucleation of a fretting crack is predicted by superimposing the crack growth rate experienced under fretting conditions onto S–N fatigue data for the alloy. The growth model utilizes small crack growth rate data and a fretting fatigue stress intensity factor to account for the small crack sizes and higher stresses experienced under fretting fatigue conditions. The development of the propagation model within the established fatigue crack growth code AFGROW allows this approach to be readily used by members of the aerospace industry. 相似文献
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Hyeon Chang Choi 《Journal of Mechanical Science and Technology》2000,14(4):401-407
An elastic-plastic finite element analysis is performed to investigate detailed closure behavior of fatigue cracks and the numerical results are compared with experimental results. The finite element analysis performed under plane stress using 4-node isoparametric elements can predict fatigue crack closure behavior. The mesh of constant element size along crack surface can not predict the opening level of fatigue crack. The crack opening level for the constant mesh size increases linearly from initial crack growth. The crack opening level for variable mesh size, is almost flat after crack tip has passed the monotonic plastic zone. The prediction of crack opening level using the variable mesh size proportioning the reversed plastic zone size with the opening stress intensity factors presents a good agreement with the experimental data regardless of stress ratios. 相似文献
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N. I. I. Mansor S. Abdullah A. K. Ariffin 《Journal of Mechanical Science and Technology》2017,31(10):4719-4726
This paper discusses the fatigue life behaviour of the API X65 steel tested under constant amplitude loading in ambient temperature. The influence of repeated loading at a particular stress ratio would favour the initiation of fatigue cracks that would consequently affect the fatigue crack growth. The main objective of this paper is to evaluate the load ratio effects on fatigue crack growth rate, taking into account their statistical characteristics. The fatigue crack growth test was carried out using compact-tension specimen at different load ratios of 0.1, 0.4 and 0.7. The experimental results showed the crack growth rate was dependent on the applied load. It was observed that the load ratio effect was less significant in stable crack growth regions. The result was consistent with the multiple regression test obtained by the least square method at a significance level of 0.05. The empirical model of Paris and Walker was utilised to evaluate the effects of load ratio on the fatigue crack growth rates. The approximation of fatigue life lies between 10-25 % of error using conservative model and 6 % error using the Walker model. The experimental data was scattered within a factor-of-2 correlation line suggesting that the accuracy of the experimental data towards the estimated values was high. 相似文献
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航空发动机涡轮盘用GH4133B合金疲劳裂纹扩展行为研究 总被引:3,自引:1,他引:3
材料的疲劳寿命由裂纹形成寿命和扩展寿命两部分组成。针对航空发动机涡轮盘用GH4133B合金,进行室温下不同应力比的疲劳裂纹扩展试验,测试疲劳裂纹扩展门槛值。Paris公式回归分析结果表明,裂纹扩展速率随应力强度因子和应力比的增大而增大,含门槛值的修正Paris公式能精确描述疲劳裂纹扩展行为。利用光学显微镜在线观测裂纹扩展路径,并利用扫描电镜考察试样断口微观形貌。结果发现,随应力强度因子增大,裂纹扩展路径由平直变得曲折。在疲劳裂纹萌生区、稳定扩展区和快速扩展区,断裂表面依次呈现为解理断裂、疲劳条带和沿晶韧窝混合断裂模式。基于断口反推理论反推载荷和裂纹扩展方程,结果表明,利用反推方程预测疲劳裂纹的扩展,可有效防范疲劳断裂的发生。 相似文献
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基于神经网络响应面的疲劳裂纹扩展寿命的可靠性分析 总被引:5,自引:0,他引:5
当失效形式的极限状态方程中随机变量个数较多或非线性较高时,其形式很复杂,因此传统的计算失效概率的方法不再适用。针对疲劳裂纹扩展寿命失效概率计算的复杂性,提出基于神经网络响应面的可靠性分析方法。首先建立神经网络响应面模拟疲劳裂纹扩展寿命的极限状态方程,然后使用遗传算法(GA)计算可靠性指标。数值试验表明,本方法可以快速、精确地模拟疲劳裂纹扩展寿命的极限状态函数,进而计算出失效概率和可靠性指标。同其他模拟技术相比,在精度相同的情况下,神经网络响应面法可以大大减少模拟时间。 相似文献
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Dong-Woo Lee Soon-Hyeok Hong Seok-Swoo Cho Won-Sik Joo 《Journal of Mechanical Science and Technology》2005,19(7):1393-1404
Fatigue crack growth and life have been estimated based on established empirical equations. In this paper, an alternative
method using artificial neural network (ANN) -based model developed to predict fatigue damages simultaneously. To learn and
generalize the ANN, fatigue crack growth rate and life data were built up using in-plane bending fatigue test results. Single
fracture mechanical parameter or nondestructive parameter can’t predict fatigue damage accurately but multiple fracture mechanical
parameters or nondestructive parameters can. Existing fatigue damage modeling used this merit but limited real-time damage
monitoring. Therefore, this study shows fatigue damage model using backpropagation neural networks on the basis of X-ray half
breadth ratioB/B
0
, fractal dimensionD
f
and fracture mechanical parameters can estimate fatigue crack growth rateda/dN and cycle ratioN/N
f
at the same time withinengineering limit error (5%). 相似文献
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LI Xuejun Key Laboratory of Health Maintenance for Mechanical Equipment of Hunan Province Hunan Science Technology University Xiangtan China Department of Precision Instruments Mechanology Tsinghua University Beijing China BIN Guangfu Key Laboratory of Health Maintenance for Mechanical Equipment of Hunan Province Hunan Science Technology Univsity Xiangtan China CHU Fulei Department of Precision Instruments Mechanology Tsinghua University Beijing China 《机械工程学报(英文版)》2007,20(3):79-82
To improve the diagnosis accuracy and self-adaptability of fatigue crack in ulterior place of the supporting shaft, time series and neural network are attempted to be applied in research on diag-nosing the fatigue crack’s degree based on analyzing the vibration characteristics of the supporting shaft. By analyzing the characteristic parameter which is easy to be detected from the supporting shaft’s exterior, the time series model parameter which is hypersensitive to the situation of fatigue crack in ulterior place of the supporting shaft is the target input of neural network, and the fatigue crack’s degree value of supporting shaft is the output. The BP network model can be built and net-work can be trained after the structural parameters of network are selected. Furthermore, choosing the other two different group data can test the network. The test result will verify the validity of the BP network model. The result of experiment shows that the method of time series and neural network are effective to diagnose the occurrence and the development of the fatigue crack’s degree in ulterior place of the supporting shaft. 相似文献