基于平均扩展速率的裂纹扩展模型  

Crack growth model based on average growth rate

作　　者：兑红娜 刘小冬[1] 王凡[1] 董江 DUI Hongna;LIU Xiaodong;WANG Fan;DONG Jiang(Department of Strength,AVIC Chengdu Aircraft Design&Research Institute,Chengdu 610091,China)

机构地区：[1]中航工业成都飞机设计研究所强度部,成都610091

出　　处：《航空学报》2020年第11期343-352,共10页Acta Aeronautica et Astronautica Sinica

摘　　要：不同于基于线弹性断裂力学(LEFM)的经典裂纹扩展模型,基于平均扩展速率的裂纹扩展模型通过形式简单的经验公式来描述随机载荷谱下单位飞行小时的平均裂纹扩展,该模型将随机谱当作"当量常幅谱"处理,模型中仅有两个特征参数,反映了所有复杂的载荷顺序效应及其他影响。基于该模型,进一步提出速率类比法则,可基于试验谱下扩展速率对未试验谱下扩展速率进行合理预测。首先介绍了基于Frost&Dugdale公式和基于Paris公式的平均扩展速率模型的内涵及参数推导方法,然后通过典型机身框关键部位模拟件在多种随机谱下的疲劳试验数据对平均扩展速率模型和速率类比法则进行试验验证。经对比分析,推荐使用基于Paris公式的平均扩展速率模型。经验证,采用基于Paris公式的模型和速率类比法则,可实现随机载荷谱下裂纹扩展速率和寿命的高精度预测。同时,速率类比法则的准确度与理论参数推导时选取的经典LEFM模型有关。平均扩展速率模型和速率类比法则为外场飞机单机寿命监控提供了一种可靠的疲劳寿命预测方法。Different from crack growth models based on classical Linear-Elastic Fracture Mechanics(LEFM),the average growth rate based model describes the average crack propagation per flight hour under a random load spectrum using a simple empirical formula.The model treats the random spectrum as an equivalent constant amplitude spectrum with only two characteristic parameters reflecting all the complex load-sequence effects and other effects.A growth rate scaling method is adopted to adjust the average growth rate obtained under one test load spectrum to predict the crack growth rate under another untested load spectrum.First,the definition and parameter derivation procedures of average growth rate models based on the Frost&Dugdale formula and Paris formula are introduced.Then,representative coupon fatigue test data of a typical bulkhead critical location under different random spectra is reviewed and the average growth rate model and growth rate scaling method have been comprehensively validated.After comparative analysis,the Paris equation based average growth rate model is recommended.It has been demonstrated that significant prediction accuracy gains of the crack growth rate and life span under variable amplitude loading spectra are achieved when the Paris equation based model is combined with the growth rate scaling method.Meanwhile,the accuracy of the growth rate scaling method is related to the classical LEFM model selected in the derivation of theoretical parameters.Thus,the average growth rate based crack growth model in conjunction with the growth rate scaling method is anticipated to provide a reliable option for the individual aircraft tracking program to better assess the aircraft structural service life.

关 键 词：裂纹扩展模型 平均扩展速率 速率类比法则 Frost&Dugdale公式 Paris公式 

分 类 号：V215.51[航空宇航科学与技术—航空宇航推进理论与工程]