An improvement in the resistance ability of fatigue crack propagation in a metal

提高金属抵抗疲劳裂纹扩展的能力

• 批准号: 07650109
• 负责人: MAKABE Chobin
• 金额: $ 1.41万
• 依托单位: University of the Ryukyus
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07650109/
• 关键词: Fatigue; Crack propagation; Crack closure; Cross-section shape; Local-heated material; Machining method; Residual stress; Metal; き裂伝ぱ則; き裂伝ぱ速度; き裂伝ぱの遅延; 部材断面; 応力拡大係数; き裂開口

If we can detect the crack initiation and control the crack propagation, the fracture accident owing to the metal fatigue can be reduced. Therefore, an improvement in the resistance ability of fatigue crack propagation in a metal was studied. For this purpose, the materials were machined and heat-treated by some method.One of these specimen has a groove which is cut in the loading direction. In this specimen the fatigue crack propagation was investigated when the material has a cross-section of complicated shape. The nondimensional depth of groove to the specimen thickness b/t was chosen three values, that is, b/t=0.125,0.45,0.65. The delay of crack propagation was observed in the case of b/t=0.65. Therefore, the resistance ability of fatigue crack propagation of a material can be improved, if the material was machined in a special shape.The crack propagation behavior of a local-heated specimen was investigated. This specimen was used for the substitution of a composite material. When the local-heated zone was located in front of the crack tip, the crack propagation rate was decelerated.From those results, it is found that a material can be improved in the resistance of the fatigue crack propagation, if the material is machined or heat-treated by a special technique. Also, it is expected that composite material can be designed for the purpose that the fatigue crack propagation rate is decelerated.

如果能检测到裂纹的萌生并控制裂纹的扩展，就能减少金属疲劳断裂事故的发生。因此，研究了金属中疲劳裂纹扩展的抵抗能力的提高。为了达到这个目的，这些材料被机械加工和热处理的一些方法。这些样本之一有一个槽，这是在加载方向切割。在该试样中，当材料具有复杂形状的横截面时，疲劳裂纹扩展进行了研究。无量纲沟槽深度与试样厚度之比B/t取三个值，即B/t= 0.125，0.45，0.65。在B/t=0.65的情况下观察到裂纹扩展的延迟。因此，将材料加工成特殊形状可以提高材料的抗疲劳裂纹扩展能力。该样本用于替代复合材料。当局部加热区位于裂纹尖端之前时，裂纹扩展速率减慢。从这些结果可以看出，如果材料通过特殊的技术进行机械加工或热处理，则可以提高材料的抗疲劳裂纹扩展能力。此外，可以预期的是，复合材料可以被设计用于疲劳裂纹扩展速率被减速的目的。