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M D Chapetti - One of the best experts on this subject based on the ideXlab platform.

  • ultra long cycle Fatigue of high strength carbon steels part i review and analysis of the mechanism of failure
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003
    Co-Authors: M D Chapetti, Tetsuya Tagawa, Takashi Miyata
    Abstract:

    In this study, the Fatigue Crack propagation from the surface and from internal inclusions is analyzed and modeled in high strength steels that show both types of Crack Initiation. Fatigue Crack propagation lives of a Crack initiated from the surface and from internal inclusions are estimated and analyzed. The high cycle Fatigue life for a given Crack range is estimated by: (a) defining material resistance to Crack propagation as a function of Crack length, and (b) assuming that the difference between the applied driving force and material resistance for Crack propagation defines the effective driving force applied to the Crack. If the Crack growth rate as a function of this effective driving force is known for a given material, the high cycle Fatigue life for a given Crack length range can be estimated. The present model estimates reasonably well the Fatigue life associated with Crack initiated from the surface. On the other hand, the Fatigue life of Crack initiated from internal inclusions has an associated Initiation life defined by a hydrogen assisted Fatigue mechanism that represents a great part of the total Fatigue life. In this case, the Fatigue Crack propagation life predicted by the model is a small part of the total Fatigue life. The estimations and analysis made in this study, in accordance with previous observations reported in the literature, reveal that the total Fatigue life associated with Cracks initiated at internal inclusions is valid only if the number of cycles necessary to develop the optical dark area (ODA) by hydrogen assisted Fatigue can be properly estimated.

Takashi Miyata - One of the best experts on this subject based on the ideXlab platform.

  • ultra long cycle Fatigue of high strength carbon steels part i review and analysis of the mechanism of failure
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003
    Co-Authors: M D Chapetti, Tetsuya Tagawa, Takashi Miyata
    Abstract:

    In this study, the Fatigue Crack propagation from the surface and from internal inclusions is analyzed and modeled in high strength steels that show both types of Crack Initiation. Fatigue Crack propagation lives of a Crack initiated from the surface and from internal inclusions are estimated and analyzed. The high cycle Fatigue life for a given Crack range is estimated by: (a) defining material resistance to Crack propagation as a function of Crack length, and (b) assuming that the difference between the applied driving force and material resistance for Crack propagation defines the effective driving force applied to the Crack. If the Crack growth rate as a function of this effective driving force is known for a given material, the high cycle Fatigue life for a given Crack length range can be estimated. The present model estimates reasonably well the Fatigue life associated with Crack initiated from the surface. On the other hand, the Fatigue life of Crack initiated from internal inclusions has an associated Initiation life defined by a hydrogen assisted Fatigue mechanism that represents a great part of the total Fatigue life. In this case, the Fatigue Crack propagation life predicted by the model is a small part of the total Fatigue life. The estimations and analysis made in this study, in accordance with previous observations reported in the literature, reveal that the total Fatigue life associated with Cracks initiated at internal inclusions is valid only if the number of cycles necessary to develop the optical dark area (ODA) by hydrogen assisted Fatigue can be properly estimated.

Thale R Smith - One of the best experts on this subject based on the ideXlab platform.

Larry J. Stotts - One of the best experts on this subject based on the ideXlab platform.

  • Quantitative, low cycle, Crack Initiation Fatigue testing of fine wires and CENELEC standard pacing coil.
    Journal of biomedical materials research, 1999
    Co-Authors: Laurie B. Hildebrand, John A. Schmidt, John K. Prentice, Larry J. Stotts
    Abstract:

    Uniaxial Fatigue testing was performed on different diameters of fine wires made from MP35N. The Fatigue limits of the wires differed from each other based on the diameter of the wire. Multiaxial (shear) Fatigue testing was also performed on a benchmark coil used to evaluate the Fatigue life of all modern pacemaker leads (the CENELEC standard coil). A computer algorithm was used to quantify the maximum shear stress and strain on the coil. The bend radius, coil diameter, wire diameter, and pitch of the coil all affect the shear stress and strain and therefore the Fatigue properties of conductor coils. Based on the analysis presented, it was determined that the portion of the CENELEC standard dealing with Fatigue, when used in its present format, is not a valid Fatigue test for pacemaker leads.

James H. Starnes - One of the best experts on this subject based on the ideXlab platform.

  • Analytical Methodology for Predicting Widespread Fatigue Damage Onset in Fuselage Structure
    Journal of Aircraft, 1998
    Co-Authors: Charles E. Harris, James C. Newman, Robert S Piascik, James H. Starnes
    Abstract:

    A comprehensive analytical methodology has been developed for predicting the onset of widespread Fatigue damage (WFD) in fuselage structure. The determination of the number of e ights and operational hours of aircraft service life that are related to the onset of WFD includes analyses for Crack Initiation, Fatigue Crack growth, and residual strength. Therefore, the computational capability required to predict analytically the onset of WFD must be able to represent a wide range of Crack sizes, from the material (microscale) level to the global (structural-scale ) level. The results of carefully conducted teardown examinations of aircraft components indicate that Fatigue Crack behavior can be represented conveniently by the following three analysis scales: 1 ) small three-dimensional Cracks at the microscale level, 2 ) through-the-thickness two-dimensional Cracks at the local structural level, and 3 ) long Cracks at the global structural level. The computational requirements for each of these three analysis scales are described in this paper.

  • analytical methodology for predicting the onset of widespread Fatigue damage in fuselage structure
    1996
    Co-Authors: Charles E. Harris, James C. Newman, Robert S Piascik, James H. Starnes
    Abstract:

    NASA has developed a comprehensive analytical methodology for predicting the onset of widespread Fatigue damage in fuselage structure. The determination of the number of flights and operational hours of aircraft service life that are related to the onset of widespread Fatigue damage includes analyses for Crack Initiation, Fatigue Crack growth, and residual strength. Therefore, the computational capability required to predict analytically the onset of widespread Fatigue damage must be able to represent a wide range of Crack sizes from the material (microscale) level to the global structural-scale level. NASA studies indicate that the Fatigue Crack behavior in aircraft structure can be represented conveniently by the following three analysis scales: small three-dimensional Cracks at the microscale level, through-the-thickness two-dimensional Cracks at the local structural level, and long Cracks at the global structural level. The computational requirements for each of these three analysis scales are described in this paper.