【作者】 刘争； 陈皓若； 陈旭；

【Author】 LIU Zheng;CHEN Haoruo;CHEN Xu;School of Chemical Engineering and Technology,Tianjin University;

【机构】 天津大学化工学院；

【摘要】 准确地评价和预测深海装备承压结构材料在各种工况下的疲劳裂纹扩展(F CG)规律极为关键。然而,钛合金的各向异性特征,导致不同取向的FCG性能差异较大,为工程评价带来了极大的挑战。在本文中,以TA15钛合金为研究对象,采用理论、试验与微观分析相结合的研究方法,提出了一种基于粗糙度系数γ的裂纹闭合程度评估方法和不同取向下疲劳裂纹扩展速率预测方法。结果表明:材料各向异性对FCG规律影响较大,不同取向试样的裂纹扩展速率呈0°<30°<45°<75°<90°。发现粗糙度致使裂纹闭合效应,并结合电子背散射衍射(EBSD)技术揭示了裂纹扩展路径上粗糙度的微观成因。进一步,建立了基于γ的裂纹闭合程度评估方法,并引入γ对疲劳裂纹扩展驱动力ΔK和裂纹扩展速率da/dN进行了修正,修正后不同取向的FCG规律实现了统一,并可以准确地预测其他取向下的FCG行为。上述结果对深海承压结构用钛合金的设计、安全服役及结构完整性评估具有重要的意义。更多还原

【Abstract】 Accurately predicting and evaluating the fatigue crack growth(FCG) performance of pressure-bearing structural materials for deep-sea equipment under various working conditions is critically important.However,the anisotropic characteristics of titanium alloys result in significant differences in FCG performance across different orientations,posing great challenges for engineering evaluation.In this paper,TA15 titanium alloy is investigated through an integrated approach combining theoretical analysis,experimental testing,and microstructural characterization.A crack closure evaluation method and a prediction methodology for fatigue crack growth rates across orientations are proposed based on the roughness coefficient y.The anisotropy of materials has a significant impact on the FCG law,and the crack propagation rate of specimens with different orientations is 0°<30°<45°<75°<90°.Pronounced crack closure effects induced by roughness were observed,with EBSD revealing microstructural origins of roughness along crack path.Meanwhile,a crack closure level assessment method based on the y was established,and roughness was introduced to modify the crack growth driving force ΔK and the crack growth rate da/dN.After modification,the FCG laws across different orientations were unified,and the FCG behavior under other orientations could be accurately predicted.The above results are of great significance for the design,safe service,and structural integrity assessment of titanium alloys used in deep-sea pressure structures.更多还原