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10 mm试样的疲劳寿命Nf大于10^8时，平均疲劳裂纹扩展速率远小于点阵间距（-0.1nm或0.01nm或<-11-12>10^m/cycle）。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是逐周期发生的。在这项研究中，研究了极高周疲劳的可能机制。在一些可能的机制中，特别关注在热处理合金钢SCM 435的断裂起源（非金属夹杂物）附近新发现的特殊疲劳断裂形态，该合金钢在N* 10^8下进行了测试。通过SEM和AFM观察到的特殊形态被认为是受夹杂物周围的氢的影响。用ROO&lt; &gt;面积参数模型对疲劳极限的预测，虽然成功地预测了传统的疲劳极限定义，但对于Nf=-10^8的疲劳寿命，其预测值有-10%的不保守性。 ...更多信息 艾德，N=10^7。因此，N*10^8的疲劳失效被认为是由一种机制引起的，该机制诱导小裂纹中疲劳裂纹闭合现象的断裂或释放。对于疲劳寿命长的试样，在断裂起源处的非金属夹杂物附近，在鱼眼标记内总是观察到一个暗区。疲劳寿命较短的Nf=-10^5的试件在鱼眼痕中没有这种暗区。SEM和AFM观察表明，暗区表面粗糙，与通常的马氏体板条疲劳断口有很大不同，考虑到高强度钢对氢环境的敏感性和夹杂物周围的高氢含量，非金属夹杂物引起的高强钢超高周疲劳破坏是由氢脆等环境效应耦合作用引起的。在拉-压和反向扭转下，对铝铸造合金、粉末金属和中碳钢也进行了类似的研究。从超长疲劳寿命的观点出发，讨论了各种金属的疲劳断裂机理。少

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, 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）。 ）

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）。

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。

Hisao MATSUNAGA,Owe Mars, Bengt Johannesson, Yukitaka MURAKAMI: "Effect of Statistical Distribution of Iron Powder Size on Fatigue Strength of Powder Metals" J.Soc.Mater.Sci.Japan.(To be published).

Hisao MATSUNAGA,Owe Mars, Bengt Johannesson, Yukitaka MURAKAMI：“铁粉尺寸统计分布对粉末金属疲劳强度的影响”J.Soc.Mater.Sci.Japan.（待出版）。