FATIGUE LIFE ESTIMATION BY LOCAL STRESS-STRAIN METHODS

Stress-strain techniques are the same as those for fracture mechanics except that local stress-strain tries to predict the number of loading cycles needed to start a crack whereas fracture mechanics deals only with the extension of an existing crack. The models used are nearer to actual physical behaviour than simple normal-stress methods and they do not require costly component testing. Two methods are developed, one a shortened version of the other, retaining nearly all its features but losing information about local stress. Flow charts are given for the two methods which can be programmed on a computer. Input information is needed on the nominal stress at a representative point and a stress concentration factor giving conditions at the most severe notch. The stress/strain curve for the material in a stable condition after repeated plastic deformation and the strain/life curve also need to be specified. The calculation works through the sequence, reversal by reversal, calculating the local stress and strain at the root of the notch building up a sequence of peaks and valleys by identifying the closure of hysteresis loops. An equation is developed to estimate the damage caused by each reversal, and the life is estimated by the number of repetitions of the sequence. This article is the third of four articles on fatigue. (TRRL)

• Supplemental Notes:
  • For abstracts of the other articles, published in the December 1982 and March and December 1983 issues of this journal, see TRIS nos. 373337, 388874 and 388872.
• Corporate Authors:

  Modino Press Limited

  Keswick House, 3 Greenway
  London N20 8EE,   England 
• Authors:
  • Sherratt, F
  • Eaton, D
• Publication Date: 1983-9

Media Info

• Features: Figures; References;
• Pagination: p. 28-36
• Serial:
  • Society of Environmental Engineers, Journal of
  • Volume: 22-3
  • Issue Number: 98
  • Publisher: Society of Environmental Engineers

Subject/Index Terms

• TRT Terms: Computer programs; Cracking; Deformation; Deformation curve; Ductility; Durability; Flow charts; Forecasting; Loads; Mathematical models; Mechanical fatigue; Modulus of elasticity; Plastic deformation; Service life; Strength of materials; Stresses
• Uncontrolled Terms: Fatigue life
• Old TRIS Terms: Flow charting
• ITRD Terms: 5211: Cracking; 5595: Deformation; 5909: Ductility; 5910: Durability; 5579: Fatigue (mater); 132: Forecast; 5567: Load; 6473: Mathematical model; 5919: Modulus of elasticity; 5544: Strength (mater); 5575: Stress (in material)
• Subject Areas: Design; Geotechnology; Highways; Materials; I30: Materials; I34: Steels and Metals;

Filing Info

• Accession Number: 00388871
• Record Type: Publication
• Source Agency: Transport Research Laboratory
• Files: ITRD, TRIS
• Created Date: Oct 30 1984 12:00AM