ESTIMATING FATIGUE CRACK INITIATION AND PROPAGATION LIVES IN NOTCHED PLATES UNDER VARIABLE LOADING HISTORIES

The most common failure mode of structures and components subjected to cyclic stresses/strains is fatigue. For analysis it is often convenient to separate the fatigue process into two parts: (1) a portion of life spent in crack initiation and (2) a portion spent in crack propagation. Typically, the ground vehicle industry has ignored the crack propagation portion of the total fatigue life and the aircraft industry has ignored crack initiation. Both initiation and propagation must be estimated in order to optimize the material and geometry for the application at hand. A method of estimating fatigue crack initiation lives for notched members subjected to irregular loading histories is described. It is based on a knowledge of the local stresses and strains at the notch root and material property data. Techniques for estimating crack propagation lives for notched members are also described. Crack propagation is calculated from constant amplitude materials data using an effective stress intensity concept. Finite element analysis is used to determine residual stresses and strains due to notch geometry. Analytical estimates are compared to experimental data from the SAE Cumulative Fatigue Damage test program. Procedures developed are intended to be applicable to structures and components fabricated from structural steels and aluminums subjected to pseudo-random or block load histories.

  • Corporate Authors:

    University of Illinois, Urbana-Champaign

    Department of Theoretical and Applied Mechanics
    Urbana, IL  USA  61801
  • Authors:
    • Socie, D F
  • Publication Date: 1977-6

Media Info

  • Features: References;
  • Pagination: 85 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00173408
  • Record Type: Publication
  • Source Agency: Engineering Index
  • Report/Paper Numbers: TAM Rpt n 417
  • Files: TRIS
  • Created Date: Apr 26 1978 12:00AM