Residual strength of GFRP at high-cycle fatigue

Degradation of the residual strength of a glass-fiber-reinforced polyester composite of a lay-up typical of the wind rotor blade material is studied at low-cycle fatigue. A gradual reduction of the residual strength is observed as expected for GRP, accompanied by an increasing scatter of strength. The residual strength model based on the strength-life equal rank assumption yields an accurate approximation of experimental data. The strength reduction at a stress level corresponding to high-cycle fatigue (N>10 ⁶ cycles) appears to correlate well with the test results at higher stress levels, which indicates that the strength degradation at the design stress level can be evaluated using low-cycle tests. Assuming that the parameters of the strength degradation model do not depend on the applied stress level, the residual strength data obtained in low stress level tests of comparatively short duration can be used to estimate the average fatigue life at the same stress thus reducing the total test time. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 5, pp. 595–604, September–October, 1999.     

二级加载下疲劳可靠性分析

基于二维概率Miner准则,建立了在二级变幅加载下进行疲劳可靠性分析的系统方法并采用八组较大子样的二级低高和高低加载下的试验数据进行了验证、结果表明;本文方法初步实现了对第一级加载后的剩余疲劳寿命和二级加载下的疲劳总寿命进行较为准确的可靠性预测,预测值与试验值吻合良好     

应力场强(SFI)法下的疲劳缺口系数K_f的计算

着重研究场强法理论下疲劳缺口系数Kf的计算．结果表明应力场强法理论下的疲劳缺口系数Kf与试验结果符合得较好,用应力场强法理论计算得到的等幅和变辐载荷的寿命与试验寿命也符合得较好．     

纤维金属层极疲劳寿命预测的研究进展

简要介绍了纤维金属展板的起源、性能特点、应用现状与前景,对其疲劳损伤机理作了简要分析．对影响层板疲劳寿命的两个关键因素──桥接应力与分层扩展从理论分析与测量技术两方面结合自己的研究成果作了系统评析．详细分析了层板在等幅疲劳下寿命预测的研究现状．介绍了层板在变幅载荷下的疲劳行为（包括裂纹扩展与分层扩展）与寿命预测的研究进展,指出了目前预测模型的有待改进的建议．      

疲劳寿命估算中应注意的一个问题

指出疲劳寿命估算时,必须注意将Paris公式的系数C随所用单位制相应改变．     

用光塑性方法确定工程构件的疲劳裂纹扩展荷载门槛值

提出疲劳裂纹尖端塑性核半径门榄值Ｒｔｈ的概念及计算方法,Ｒｔｈ是材料性质,在满足光塑性相似关系要求及模型与原型几何形状尺寸相同的前提下,模型与原型间的相似系数ｎ为两种材料屈服极限之比。     

多轴非线性连续疲劳损伤累积模型的研究

根据所建立的单轴非线性疲劳损伤累积模型,在多轴疲劳损伤临界面原理研究的基础上,针对多轴比轴比例加载,建立了多轴非线性连续疲劳损伤累积模型,该模型可以考虑多轴疲劳极限、平均静水应力以及损伤参量与加载参数的不可分离的特点,并且能够反映出多轴加载顺序的影响,最后讨论了该多轴疲劳损伤累积模型在多级加载下的递推形式,经多轴二级及块载疲劳试验数据验证表明,用该模型预测多轴疲劳寿命,其结果令人满意。     

焊趾表面裂纹的形态发展曲线与疲劳寿命预测

以作者建立的焊地椭圆表面裂纹应力强度因子数据库以及复杂应力场中焊践半随圆表面裂纹前缘应力强度因子分布计算的基本模式法为基础上,给出了复杂应力场中焊践表面表纹在疲劳扩展过程中形态变化规律及寿命的工程分析方法。     

阵风谱载下疲劳寿命可靠性预测

基于维概率ＭＩＮＥＲ准则,建立了在阵风谱载下对结构构件疲劳寿命进行可靠性预测的方法。根据一组ＬＹ１２－ＣＺ铝合金中心孔试件的疲劳试验数据对上述方法进行了较为成功的验证,验证结果表明本方法的预测值与试验值吻合良好,具有较好的工程实用价值     

Fatigue properties of 2024-T3, 7075-T6 aluminum alloys modified using plasma-enhanced ion beams

This paper presents experimental results on the application of Microsecond Plasma Opening Switch (MPOS) technology to Al alloy surface modification. The main objective of the experiments presented here was to study the change in the tensile and fatigue properties of the MPOS-treated Al2024, Al7075 alloy samples. The bending fatigue test was carried out both in air and in corrosive media. The measurements indicate significant improvement of fatigue properties for the treated 7075 alloy in corrosive media (1.5 times higher in fatigue limit). For the 2024 alloy the enhancement in fatigue lifetime for higher stresses was measured. Anodic polarization curve measurements were carried out at various values of fatigue cycles.