氏名　JAYAPRAKASH MURUGESAN
学位の種類　博士（工学）
学位記番号　博甲第536号
学位授与の日付　平成22年3月25日
学位論文題目　A New Approach for Predicting Fretting Fatigue Strength Based on Tangential Stress Range - Compressive Stress Range Diagram　（接線応力範囲－圧縮応力範囲線図に基づく新たなフレッティング披露強度予測法）
論文審査委員
　主査　教授　武藤　睦治
　副査　教授　岡崎　正和
　副査　准教授　井原　邦夫
　副査　准教授　宮下　幸雄
　副査　実務家教授　永田　晃則

• 論文目次
• 論文要旨
• 論文審査の結果の要旨

［平成21（2009）年度博士論文題名一覧］ ［博士論文題名一覧］に戻る．

Table of contents
Acknowledgements　p.i
Abstract　p.ii
Table of Contents　p.iv
List of Figures　p.viii
List of Tables　p.xii
Chapter 1　Introduction
　1.1　Introduction　p.2
　1.2　Scope and objective　p.5
　1.3　Dissertation Outline　p.7
Chapter 2　Literature review
　2.1　Historical introduction of fretting fatigue　p.10
　2.2　Practical examples of fretting fatigue　p.11
　2.3　Crack nucleation in fretting fatigue　p.12
　2.4　Crack propagation during fretting fatigue　p.13
　2.5　Crack growth behavior in fretting fatigue　p.15
　2.6　Variables influencing fretting fatigue　p.17
　2.6.1　Coefficient of friction　p.18
　2.6.2　Contact pressure　p.18
　2.6.3　Relative slip　p.19
　2.6.4　Contact rigidity　p.19
　2.6.5　Temperature　p.20
　2.6.6　Humidity　p.20
　2.7　Palliatives of fretting fatigue　p.21
　2.7.1　Application of surface engineering　p.21
　2.7.2　Lubricants　p.21
　2.7.3　Change in design　p.22
　2.8　Effect of stress relief groove at the contact edge　p.22
　2.9　Fretting fatigue strength prediction　p.23
Chapter 3　Effect of Contact Pad Rigidity on Fretting Fatigue Behavior of Ni-Cr-Mo-V Turbine Steel
　3.1　Introduction　p.29
　3.2　Experimental procedure　p.31
　3.2.1　Materials and specimens　p.31
　3.2.2　Fretting fatigue tests　p.31
　3.2.3　Finite element analysis　p.34
　3.3　Results and Discussion　p.36
　3.3.1　Definition of contact pad rigidity　p.36
　3.3.2　Effect of Contact Pad Rigidity on relative slip amplitude　p.37
　3.3.3　Effect of Contact Pad Rigidity on tangential force coefficient　p.39
　3.3.4　Effect of Contact Pad Rigidity on stress state distribution along contact interface　p.40
　3.3.5　Effect of Contact Pad Rigidity on tangential stress range and compressive stress range　p.42
　3.3.6　Effect of Contact Pad Rigidity on fretting fatigue strength　p.45
　3.3.7　Fretting fatigue failure condition　p.48
　3.4　Conclusion　p.50
Chapter 4　Application of Tangential Stress Range - Compressive Stress Range Diagram to Dovetail Joint
　4.1　Introduction　p.57
　4.2　Experimental procedure　p.59
　4.2.1　Materials and specimens　p.59
　4.2.2　Fretting fatigue tests　p.59
　4.2.3　Finite element analysis　p.63
　4.3　Results and Discussion　p.65
　4.3.1　Conventional laboratory - type fretting fatigue test　p.65
　4.3.1.1　Stress component at the contact interface　p.65
　4.3.1.2　Effect of contact pressure and pad geometry on stress distribution at contact edge　p.65
　4.3.1.3　Effects of contact pad geometry and contact pressure on fretting fatigue strength　p.67
　4.3.1.4　Fretting fatigue design curve　p.70
　4.3.2　Fretting fatigue behavior of dovetail joint　p.70
　4.3.2.1　Contact pressure at dovetail joint　p.70
　4.3.2.2　Fretting fatigue strength of dovetail joint specimen　p.71
　4.3.2.3　Confirmation of fretting fatigue design curve　p.75
　4.4　Conclusion　p.77
Chapter 5　Fretting Fatigue Behavior and Strength Prediction of Bolted Joint
　5.1　Introduction　p.82
　5.2　Experimental procedure　p.84
　5.2.1　Materials and specimens　p.84
　5.2.2　Fretting fatigue tests　p.86
　5.2.3　Finite element analysis　p.87
　5.3　Results and Discussion　p.89
　5.3.1　Stress distribution at the contact　p.89
　5.3.2　Fretting fatigue strength of bolted steel plate　p.92
　5.3.3　Fretting fatigue test of conventional smooth specimen　p.95
　5.3.3.1　Specimen and contact pad　p.95
　5.3.3.2　Fretting fatigue tests and finite element analysis　p.95
　5.3.3.3　Effects of pad geometry and contact pressure on stress distribution at contact edge　p.95
　5.3.3.4　Effects of contact pad geometry and contact pressure on fretting fatigue strength　p.98
　5.3.4　Parameters controlling fretting fatigue　p.100
　5.4　Conclusion　p.102
Chapter 6　Fretting Fatigue Behavior of Cr-Mo-W-V Steel at Elevated Temperature and Strength Prediction
　6.1　Introduction　p.110
　6.2　Experimental procedure　p.111
　6.2.1　Materials and specimens　p.111
　6.2.2　Finite element analysis　p.115
　6.3　Results and Discussion　p.115
　6.3.1　Effect of Temperature on Fangential force coefficient　p.115
　6.3.2　Effect of temperature on fretting fatigue strength　p.116
　6.3.3　Fretting fatigue strength prediction　p.119
　6.4　Conclusion　p.122
Chapter 7　Generalized Fretting Fatigue Design Curve
　7.1　Introduction　p.126
　7.2　Construction of tangential stress range - compressive stress range diagram　p.127
　7.3　Generalized tangential stress range - compressive stress range diagram　p.128
　7.4　Example of fretting fatigue strength prediction based on the generalized tangential stress range - compressive stress range diagram　p.131
　7.4.1　Evaluation of tangential stress range and compressive stress range　p.131
　7.4.2　Fretting fatigue strength prediction of 12 Cr steel　p.132
　7.5　Experimental verification of predicted fretting fatigue limit　p.133
　7.6　Conclusion　p.136
Chapter 8　Overall Conclusions and Future Prospects
　8.1　Overall conclusions　p.139
　8.2　Future prospect　p.143
List of Publications　p.146

Fretting fatigue is a serious problem in engineering applications, where two components are in contact and one of them is subjected to cyclic loading.　Fretting, a small amplitude oscillatory relative motion between contacting components, creates surface and subsurface damage from which fatigue cracks nucleate and grow in the presence of a cyclic load.　This can occur at stress levels well below the fatigue limit of a material. Fretting fatigue can cause surface micro crack nucleation within first several thousand cycles, significantly reducing the component life. Additionally, cracks due to fretting are usually hidden by the contacting components and are not easily detected. If the conditions are favorable for continuous propagation of cracks nucleated by fretting, a catastrophic failure can occur. Fretting fatigue is particularly important in safety-critical industries such as automotive, railways aerospace and power generation.

Fretting fatigue behavior is strongly dependent on geometry of component and loading condition. However, most of the studies on fretting fatigue have been conducted by using simplified laboratory - type specimens and fretting fatigue set-up with simplified geometry of contact pads.　These simplified laboratory - type fretting fatigue tests are useful to understand basic characteristics of fretting fatigue, such as effect of contact pressure, effect of slip amplitude, effect of environment, etc. However, it is difficult to directly predict fretting fatigue strength and life of actual components based on the result of fretting fatigue test of laboratory - type specimen. It is still important to investigate how the fretting0 fatigue strength and life should be predicted based on the result of the laboratory - type fretting fatigue test.

In the present study, a new approach to predict fretting fatigue strength, irrespective of contact geometry and strength has been proposed, based on the stress distribution at the contact edge, i.e. the tangential stress range and compressive stress range. The content of the present dissertation are as follows.

In chapter 1, a brief introduction about present dissertation has been addressed. The scope and objective of the present dissertation have also been addressed.

In chapter 2, literature review on fretting fatigue related to this dissertation has been addressed. Historical background about fretting fatigue has been provided. Practical examples of fretting fatigue have been described. Parameters influencing fretting fatigue have been described. Fretting fatigue strength improvement methods has been discussed. Fretting fatigue strength prediction methods has also been described.

In chapter 3, the effect of contact pad rigidity on fretting fatigue strength of turbine steels （Ni-Cr-Mo-V steel specimen with 12 Cr steel contact pad） has been investigated, by conducting fretting fatigue tests and finite element analysis with contact pads of various foot heights. A design curve defined by two parameters （tangential stress range and compressive stress range diagram） to predict fretting fatigue life has been proposed.

In chapter 4, the applicability of the tangential stress range and compressive stress range diagram, to actual component geometries i.e. to dovetail joint has been discussed by conducting the fretting fatigue tests and finite element analysis with dovetail specimens. The results showed that the data point of tangential stress range and compressive stress range corresponding to particular fretting fatigue lives of dove tail specimens agrees well with the tangential stress range and compressive stress range diagram, which was constructed using conventional laboratory type specimen.

In chapter 5, the fretting fatigue behavior of automotive steel （JIS SAPH 400 steel） has been investigated. And then the applicability of the tangential stress range and compressive stress range diagram, to bolted joint has also been discussed.

In chapter 6, fretting fatigue behavior of Cr-Mo-W-V turbine steels at 673 K has been investigated. The Strength prediction based on tangential stress range and compressive stress range diagram, has been discussed for Cr-Mo-W-V steel at 673 K. For comparisons tangential stress range and compressive stress range diagram has also been constructed for Cr-Mo-W-V turbine steels at room temperature.

In chapter 7, from the tangential stress range and compressive stress range diagrams of Cr-Mo-W-V steel, 12 Cr steel, Ni-Cr-Mo-V steel and SAPH 400 steel, a generalized design curve has been proposed by normalizing the tangential stress range and compressive stress range using the tensile strength of each material. Fretting fatigue strength prediction based on normalized tangential stress ? compressive stress diagram, irrespective of material strength and geometry has been discussed. An example of strength prediction based on the proposed approach has also been illustrated by carrying out fretting fatigue tests and finite element analysis with 12 Cr steel specimens. Finally, it has been concluded that the normalized tangential stress range and compressive stress range diagram can be used as a generalized fretting fatigue design curve, to predict fretting fatigue strength effectively irrespective of contact geometry and material strength.

In chapter 8, the most significant results of the current work have been addressed. Also the suggestions for future work have been addressed.

　本論文は、「A New Approach for Predicting Fretting Fatigue Strength Based on Tangential Stress Range-Compressive Stress Range Diagram （接線応力範囲―圧縮応力範囲線図に基づく新たなフレッティング疲労強度予測法）」と題し、8章より構成されている。
第1章「Introduction」では、本研究の目的と範囲を述べている。
第2章「Literature review」では、フレッティング疲労の基本的事項と問題を概説するとともに、本論文に関連するこれまでの研究の概略を述べ、本研究の意義を明示している。
第3章「Effect of Contact Pad Rigidity on Fretting Fatigue Behavior of Ni-Cr-Mo-V Turbine Steel」では、フレッティング疲労に及ぼす接触片剛性の影響を検討するとともに、実験結果とFEMによる応力解析結果を組み合わせることにより、接線応力範囲―圧縮応力範囲線図に基づくフレッティング疲労寿命予測法を提案している。
第4章「Applicability of Tangential Stress Range-Compressive Stress Range Diagram to Dovetail Joint」では、前章で提案した接線応力範囲―圧縮応力範囲線図に基づく疲労強度推定法を実際のダブテイルジョイントに適用し、その有効性を示している。
第5章「Fretting Fatigue Behavior and Strength Prediction of Bolted Joint」では、提案する接線応力範囲－圧縮応力範囲線図に基づく疲労強度推定法をボルト締結部材に適用し、その有効性を示している。
第6章「Fretting Fatigue Behavior of Cr-Mo-W-V-Steel at Elevated Temperature and Strength Prediction」では、高温におけるCr-Mo-W-V鋼のフレッティング疲労試験を行い、高温においても室温と同様に、接線応力範囲－圧縮応力範囲線図が得られることを示している。
第7章「Generalized Fretting Fatigue Design Curve」では、第6章までに得られた異なる材料、温度における接線応力範囲－圧縮応力範囲線図に対し、一般化した線図の可能性を検討し、各材料の引張強度で接線応力ならびに圧縮応力を標準化することにより、材料、温度条件によらず、一般化した接線応力範囲－圧縮応力範囲線図が得られることを示すとともに、これに基づきフレッティング疲労強度を推定する手法を明らかにしている。
第8章「Overall Conclusions and Future Prospects」では、以上の研究の結果を総括的にまとめるとともに、将来の展望について述べている。
よって、本論文は工学および工業上貢献するところが大きく、博士（工学）の学位論文として十分な価値を有するものと認める。