摘要
将基于小裂纹理论的疲劳全寿命预测方法应用于恒幅载荷作用下的高温合金GH4169材料的全寿命预测。采用单边缺口试样研究了该合金在室温下应力比为0.1和0.5的自然萌生的小裂纹的起始和扩展行为,结果表明疲劳小裂纹均起始于试样表面夹杂,并且小裂纹扩展寿命占疲劳全寿命的大部分比例。在裂纹扩展速率da/d N低于10-5mm/cycle的区域,表现出明显的小裂纹效应。基于小裂纹和长裂纹的扩展数据,利用Newman裂纹闭合模型,获得了裂纹扩展的da/d N-ΔKeff基线数据。对高周疲劳试样的断口形貌进行观察,得到以材料夹杂尺寸作为初始裂纹尺寸的值ai。根据初始裂纹尺寸和裂纹扩展的基线数据,利用FASTRAN软件,对GH4169合金的疲劳全寿命进行预测,并用高周疲劳试验S-N数据对预测结果进行评价,预测与试验结果能够很好地吻合。
Fatigue life prediction method based on small crack theory was used on GH4169 superalloy to calculate fatigue lives under constant-amplitude loading conditions.The growth behaviors of natural-initiated small fatigue cracks in single edge notched specimens of GH4169 superalloy under stress ratios of 0.1 and 0.5 at room temperature were studied.All small cracks initiate from the inclusions on specimen surface,and most of the total fatigue lives are cost on the phase of small crack propagation.Small crack effects are significantly shown in the zone of crack growth rate lower than 10-5 mm/cycle.According to the Newman crack closure model,the da/dN△Keff baseline data were obtained based on the long-and small-crack growth data.The fracture morphology of high cycle fatigue specimens were observed and analyzed.The results show that the fatigue cracks initiate from typical inclusions of the material on specimen surfaces.The initial crack size,ai,from the inclusion size,is obtained from analysis on specimen fracture surfaces.Based on the initial crack size and the baseline data,the total fatigue lives of GH4169 superalloy were predicted using FASTRAN software.The prediction results were evaluated by high cycle fatigue test data.Results from the tests and prediction agree well for both R ratios.
出处
《航空材料学报》
EI
CAS
CSCD
北大核心
2014年第6期75-83,共9页
Journal of Aeronautical Materials
