共振态下阻尼硬涂层对叶片疲劳裂纹扩展延缓效应的研究

Fatigue crack retardation by the application of hard damping coating to blades under resonance

本文提出采用大气等离子喷涂NiCrAlY阻尼硬涂层的方法来抑制叶片的裂纹扩展。首先,分别对无涂层和带涂层叶片试验件开展共振疲劳测试。结果表明,阻尼硬涂层具有一定的裂纹修复和扩展延缓能力。然后,建立了含裂纹叶片试验件的有限元模型,并通过对比叶片试验件固有频率随裂纹扩展的变化验证了该有限元模型的有效性。进一步引入裂纹扩展模型并获得了无涂层和带涂层叶片试验件在不同裂纹扩展阶段的裂纹尖端应力强度因子,揭示了阻尼硬涂层延缓裂纹扩展的机理。最后,给出了不同条件下叶片试验件的裂纹扩展曲线,并讨论了涂层参数厚度、涂层弹性模量和涂层密度对裂纹扩展速率的影响,还分析了涂层施加阶段对裂纹扩展的影响。进一步讨论了裂纹深度和裂纹角度对裂纹扩展的影响,这有助于优化涂层布局。实验和数值分析结果表明,阻尼硬涂层可以有效地延缓叶片裂纹扩展,是一种实用的延缓裂纹扩展技术。

The hard damping coating via atmospheric plasma spraying(APS)method was proposed to inhibit crack propagation of blade specimens in this paper.The fatigue test of uncoated and coated thin-walled blade specimens was carried out under resonance,and experimental results show that hard damping coating has the ability of crack retardation.Then,the finite element(FE)model of standard blade specimens with breathing crack was established and verified by natural frequency change of blade specimens with crack propagation.Furthermore,the crack propagation model was introduced.The crack tip stress intensity factors(SIFs)of uncoated and coated blade specimens under different crack lengths were calculated,and the crack retardation mechanism of coating was explained.Finally,the crack propagation curves of the blade specimens were calculated,and the effects of the thickness,elastic modulus and density of the coating on the crack growth were discussed.The influence of coating treatment in different stages on crack propagation was analyzed.The effects of crack depth and crack angle on crack propagation were discussed,which can help optimize coating layout.Experimental and numerical analysis show that hard damping coating can effectively delay the crack propagation,which is a practical technology in engineering application of crack propagation retardation.