Fatigue Mechanism of Superlong Fatigue Failure of steels in Gigacycle Regime

十亿周体系钢超长疲劳失效的疲劳机理

• 批准号: 08405012
• 负责人: MURAKAMI Yukitaka
• 金额: $ 20.99万
• 依托单位: KYUSHU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08405012/
• 关键词: Superlong fatigue; Nonmetallic inclusion; Fish-eye; Hydrogen embrittlement; Crack growth rate; The ROO<area> parameter model; SEM; AFM; √ areaパラメータモデル; 超寿命疲労

When fatigue life Nf of a specimen of 10mm in size is longer than 10^8, the average fatigue crack growth rate is much less than lattice spacing(- 0.1 _ or 0.01nm or 10^<-11-12>m/cyc1e). In the early stage of fatigue process, the crack growth rate should be much less than the average growth rate and accordingly we cannot assume that crack growth occurs cycle by cycle.In this study, possible mechanisms for extremely high cycle fatigue are investigated. Of some possible mechanisms, a special focus was put on a newly found particular fatigue fracture morphology in the vicinity of fracture origin (nonmetallic inclusions) of a heat treated alloy steel, SCM435, which was tested up to N* 10^8 The particular morphology observed by SEM and AFM was presumed to be influenced by the hydrogen around inclusions. The predictions of fatigue limit by the ROO< > area parameter model are -10% unconservative for fatigue life of Nf= -10^8, though it successfully predicts the conventional fatigue limit defin … More ed for N=10^7. Thus, the fatigue failure for N*10^8 is presumed to be caused by a mechanism which induces breaking or releasing of fatigue crack closure phenomenon in small cracks.In the vicinity of a nonmetallic inclusion at fracture origin a dark area was always observed inside a fish-eye mark for specimens with long fatigue life. Specimens with short fatigue life of Nf=-10^5 do not have such dark area in fish-eye mark. SEM and AFM observations revealed that the dark area has a rough surface quite different from usual fatigue fracture surface in martensite lath structure.Considering a high sensititivity of high strength steels to hydrogen environment and high hydrogen content around inclusions, it may be concluded that the extremely high cycle fatigue failure of high strength steels from nonmetallic inclusions is caused by environmental effects such as hydrogen embrittlement coupled with fatigue.Similar studies have been also done on an aluminum cast alloy, powder metals and medium carbon steels under tension-compression and reversed torsion. The fatigue fracture mechanism of various metals has been discussed from the viewpoint of superlong fatigue life. Less

当尺寸为10mm的试件疲劳寿命Nf大于10^8时，平均疲劳裂纹扩展速率远小于晶格间距（- 0.1_或0.01nm或10^<-11-12>m/cyc1e）在疲劳过程的早期阶段，裂纹扩展速率应远小于平均扩展速率，因此我们不能假设裂纹扩展逐周期发生。在本研究中，可能的机制。在一些可能的机制中，特别关注了热处理合金钢 SCM435 断裂源（非金属夹杂物）附近新发现的特殊疲劳断裂形态。 N* 10^8 SEM 和 AFM 观察到的特定形貌被认为受到夹杂物周围氢的影响。ROO< > 面积参数模型对疲劳极限的预测对于 Nf= 的疲劳寿命来说不保守 -10%。 -10^8，尽管它成功地预测了 N=10^7 定义的传统疲劳极限，因此，N*10^8 的疲劳失效被认为是由导致疲劳断裂或释放的机制引起的。小裂纹中的裂纹闭合现象。在疲劳寿命长的试件中，在断裂源处的非金属夹杂物附近，鱼眼标记内总是观察到暗区，而疲劳寿命短（Nf=-10^5）的试件则不会。有SEM和AFM观察发现，该暗区具有与马氏体板条结构中通常的疲劳断口表面截然不同的粗糙表面。考虑到高强度钢对氢环境的高敏感性以及周围的高氢含量。夹杂物，可以得出结论，非金属夹杂物引起的高强度钢的极高循环疲劳失效是由环境影响（例如氢脆与疲劳相结合）引起的。对铝铸件也进行了类似的研究从超长疲劳寿命的角度讨论了合金、粉末金属和中碳钢在拉压和反向扭转下的疲劳断裂机理。

项目成果

村上敬宜,高橋宏治: "ねじり疲労強度に及ぼす引張圧縮疲労試験により導入した微小予き裂の影響" 材料. 47・8. 846-851 (1998)

Takayoshi Murakami、Koji Takahashi：“拉伸压缩疲劳试验引入的微预裂纹对扭转疲劳强度的影响”材料 47・8（1998）。

村上敬宜, 野本哲志, 村上保夫: "SCM浸炭窒化・焼入れ焼もどし材の疲労強度に及ぼす介在物の影響" 日本機械学会第75期通常総会講演会講演論文集. 385-386 (1998)

Takayoshi Murakami、Tetsushi Nomoto、Yasuo Murakami：“夹杂物对 SCM 碳氮共渗、淬火和回火材料的疲劳强度的影响”日本机械工程师学会第 75 届普通大会论文集 385-386（1998 年）。

村上敬宜, 高橋宏治: "ねじり疲労強度に及ぼす引張圧縮で導入した微小き裂の影響(せん断平均応力の影響)" 日本機械学会,第75期通常総会講演会講演論文集(II). 359-360 (1998)

Takayoshi Murakami、Koji Takahashi：“拉伸压缩引入的微裂纹对扭转疲劳强度的影响（平均剪切应力的影响）”日本机械工程学会第75届普通大会记录（II）359 -360（1998年）。 ）

Yukitaka MURAKAMI,Tetsushi NOMOTO,Yasuo MURAKAMI: "Effect of Nonmetallic Inclusions on the Fatigue Strength of Carburized and Nitrided SCM435steel" Proceedings of The 75th JSME Spring Annyal Meeting. 385-386 (1998)

Yukitaka MURAKAMI、Tetsushi NOMOTO、Yasuo MURAKAMI：“非金属夹杂物对渗碳氮化SCM435钢疲劳强度的影响”第75届JSME春季年会论文集。

村上敬宜,野本哲志,村上保夫: "SCM浸炭窒素・焼入れ焼きもどし材の疲労強度に及ぼす介在物の影響" 日本機械学会第75期通常総会講演会講演論文集. 385-386 (1998)

Takayoshi Murakami、Tetsushi Nomoto、Yasuo Murakami：“夹杂物对SCM氮渗碳、淬火和回火材料的疲劳强度的影响”日本机械工程学会第75届普通大会论文集385-386（1998）。