The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Kenji Hirakawa - One of the best experts on this subject based on the ideXlab platform.
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Review of the fatigue damage tolerance of high-speed railway axles in Japan
Engineering Fracture Mechanics, 2011Co-Authors: Taizo Makino, Takanori Kato, Kenji HirakawaAbstract:Abstract Railway axles are one of the most important components in railway systems since a Fail-Safe Design is not available. In the present paper, the fatigue tolerance of the high-speed railway axle in Japan is reviewed. To maintain the safety, the fatigue strength of the axle has been extensively studied. Theses case histories and consequent improvements in manufacturing process are presented. The crack propagation behavior of the induction hardened axle is studied based on the fracture mechanics. Concerning the powered railway axles, the fatigue Design method in Japan is compared with that in Europe and the effect of the train velocity on the allowable load is discussed.
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The analysis and prevention of failure in railway axles
International Journal of Fatigue, 1998Co-Authors: Kenji Hirakawa, K. Toyama, Masanobu KubotaAbstract:Abstract Axles are one of the most important components in railway vehicle with regard to safety, since a Fail-Safe Design is not available. To maintain the safety record of high speed railway systems, the fatigue strength of the axles has been extensively studied. The objective of the present paper is to review and analyse the causes of failure in railway axles, and to show how the results have been applied to improve axle manufacture and in-service inspection. The problems of fretting fatigue crack initiation at press-fitted axle parts is emphasized, however, these problems have not been completely solved even though up-to-date fatigue Design methods are employed. The safety of the railway has been ensured by maintenance such as the regular inspection for fatigue cracks at critical parts.
Mark E. Walter - One of the best experts on this subject based on the ideXlab platform.
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A parametric study of damage initiation and propagation in EB-PVD thermal barrier coatings
Mechanics of Materials, 2020Co-Authors: Himanshu Bhatnagar, Somnath Ghosh, Mark E. WalterAbstract:In this paper, finite element models are used to investigate catastrophic failure of thermal barrier coatings (TBCs) due to delaminations along susceptible interface between thermally grown oxide (TGO) and the ceramic top coat. The top coat crack initiation and propagation is investigated using a thermo-elastic finite element model with bond coat creep. Cracks are assumed to initiate when the maximum principal stress exceeds rupture stress of the top coat. A sensitivity analysis estimates the contribution of geometric and material parameters. Subsequently, crack propagation simulations using a hysteretic cohesive zone model are performed for parametric combinations which initiate top coat cracks. A parametric relationship is established for assessing crack initiation in terms of geometric and material parameters of the TBC that helps identify the Fail-Safe Design space for TBC. The finite element predictions are also compared to the experimental observations of failure.
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Parametric studies of failure mechanisms in elastic EB-PVD thermal barrier coatings using FEM
International Journal of Solids and Structures, 2006Co-Authors: Himanshu Bhatnagar, Somnath Ghosh, Mark E. WalterAbstract:Abstract Catastrophic failure of thermal barrier coatings (TBCs), usually occurs due to large scale buckling and spallation, primarily originating at the bond coat and TGO interface. Spallation in TBCs is preceded by a competition between buckling and interface delamination that is stimulated by the waviness of the interface. In the presence of thermal loading, the waviness is responsible for growth of interfacial delamination. In this paper, a finite element model of the two and three layer TBC’s is developed in the commercial code ANSYS to investigate the buckle and interface delamination mechanisms and develop a simplified parametric understanding of these mechanisms. The models for simulation are validated with analytical and experimental results. Parametric relations, in terms of geometric and material parameters representing constituents of the TBC, are developed in this paper for critical stresses and energies causing buckling and debonding initiated instabilities. Through these relations, critical parameters that control failure mechanics are identified for a Fail-Safe Design space.
Xu Binshi - One of the best experts on this subject based on the ideXlab platform.
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Residual stresses within sprayed coatings
Journal of Central South University of Technology, 2005Co-Authors: Jiang Yi, Xu BinshiAbstract:Some important developments of residual stress researches for coating-based systems were studied. The following topics were included the sources of residual stresses in coatings: error analysis of Stoney’s equation in the curvature method used for the measurement of coating residual stress, the modeling of residual stress and some analytical models for predicting the residual stresses in coatings. These topics should provide some important insights for the Fail-Safe Design of the coating-based systems.
Himanshu Bhatnagar - One of the best experts on this subject based on the ideXlab platform.
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A parametric study of damage initiation and propagation in EB-PVD thermal barrier coatings
Mechanics of Materials, 2020Co-Authors: Himanshu Bhatnagar, Somnath Ghosh, Mark E. WalterAbstract:In this paper, finite element models are used to investigate catastrophic failure of thermal barrier coatings (TBCs) due to delaminations along susceptible interface between thermally grown oxide (TGO) and the ceramic top coat. The top coat crack initiation and propagation is investigated using a thermo-elastic finite element model with bond coat creep. Cracks are assumed to initiate when the maximum principal stress exceeds rupture stress of the top coat. A sensitivity analysis estimates the contribution of geometric and material parameters. Subsequently, crack propagation simulations using a hysteretic cohesive zone model are performed for parametric combinations which initiate top coat cracks. A parametric relationship is established for assessing crack initiation in terms of geometric and material parameters of the TBC that helps identify the Fail-Safe Design space for TBC. The finite element predictions are also compared to the experimental observations of failure.
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Parametric studies of failure mechanisms in elastic EB-PVD thermal barrier coatings using FEM
International Journal of Solids and Structures, 2006Co-Authors: Himanshu Bhatnagar, Somnath Ghosh, Mark E. WalterAbstract:Abstract Catastrophic failure of thermal barrier coatings (TBCs), usually occurs due to large scale buckling and spallation, primarily originating at the bond coat and TGO interface. Spallation in TBCs is preceded by a competition between buckling and interface delamination that is stimulated by the waviness of the interface. In the presence of thermal loading, the waviness is responsible for growth of interfacial delamination. In this paper, a finite element model of the two and three layer TBC’s is developed in the commercial code ANSYS to investigate the buckle and interface delamination mechanisms and develop a simplified parametric understanding of these mechanisms. The models for simulation are validated with analytical and experimental results. Parametric relations, in terms of geometric and material parameters representing constituents of the TBC, are developed in this paper for critical stresses and energies causing buckling and debonding initiated instabilities. Through these relations, critical parameters that control failure mechanics are identified for a Fail-Safe Design space.
Masanobu Kubota - One of the best experts on this subject based on the ideXlab platform.
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The analysis and prevention of failure in railway axles
International Journal of Fatigue, 1998Co-Authors: Kenji Hirakawa, K. Toyama, Masanobu KubotaAbstract:Abstract Axles are one of the most important components in railway vehicle with regard to safety, since a Fail-Safe Design is not available. To maintain the safety record of high speed railway systems, the fatigue strength of the axles has been extensively studied. The objective of the present paper is to review and analyse the causes of failure in railway axles, and to show how the results have been applied to improve axle manufacture and in-service inspection. The problems of fretting fatigue crack initiation at press-fitted axle parts is emphasized, however, these problems have not been completely solved even though up-to-date fatigue Design methods are employed. The safety of the railway has been ensured by maintenance such as the regular inspection for fatigue cracks at critical parts.
