论文部分内容阅读
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。
The fatigue life prediction method based on the theory of small cracks was applied to the life prediction of GH4169 superalloy under constant amplitude loading. Uni-notch specimens were used to study the initiation and propagation behaviors of the naturally occurring small cracks with stress ratios of 0.1 and 0.5 at room temperature. The results show that all the small fatigue cracks originate from inclusions in the specimen surface and the small cracks propagate Lifetime accounts for most of the fatigue-to-life ratio. In the area where the crack growth rate da / d N is less than 10-5mm / cycle, the obvious small crack effect is shown. Based on the extended data of small crack and long crack, the da / d N-ΔKeff baseline data of crack propagation was obtained by using the Newman crack closure model. The fracture appearance of high-cycle fatigue specimens was observed and the value of ai, which was the size of the initial crack, was obtained with the inclusion size of the material. According to the initial crack size and the crack propagation baseline data, the fatigue life of GH4169 alloy was predicted by FASTRAN software, and the prediction results were evaluated by high cycle fatigue test (S-N) data. The predicted results are in good agreement with the experimental results.