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Spectrum Fatigue Life from a Load History

Fatigue life of a part under a variable-amplitude stress history: the history is rainflow counted (ASTM E1049), every cycle's life comes from the MIL-HDBK-5J best-fit S/N equation of the chosen material and notch condition (log N = A − B log(Seq − C) with the equivalent stress Seq = Smax (1 − R)p, which carries the mean-stress effect), and Miner's rule sums the damage to give the blocks and hours to failure with a scatter factor. 139 handbook equations are on the dropdown (steel, aluminum, magnesium, heat-resistant and titanium alloys, unnotched and notched), harvested from the handbook figures and filed with their figure numbers; custom constants can be typed.

  • Paste a peak-valley stress sequence (or already counted blocks of Smax, Smin, n); rainflow counting by ASTM E1049 with the residue as half cycles

  • Cycle life from the handbook equivalent-stress equation of the chosen alloy, product form and Kt, mean stress through (1 − R)p

  • Miner's rule damage per block, blocks and hours to failure, scatter factor; the most damaging cycles tabulated

  • Charts of the history and of the S/N equation with every counted cycle on it

Material and Load History

Unit System: /

S/N Equation (MIL-HDBK-5J best-fit curves, stresses in ksi)








Load History







References

U.S. Department of Defense (2003). Metallic Materials and Elements for Aerospace Vehicle Structures. MIL-HDBK-5J, 31 January 2003.

ASTM International (2017). Standard Practices for Cycle Counting in Fatigue Analysis. ASTM E1049-85 (Reapproved 2017), West Conshohocken, PA.

Miner, M. A. (1945). "Cumulative Damage in Fatigue." Journal of Applied Mechanics, Vol. 12, No. 3, pp. A159–A164.

Matsuishi, M., and Endo, T. (1968). "Fatigue of Metals Subjected to Varying Stress." Paper presented to the Japan Society of Mechanical Engineers, Fukuoka.

Dowling, N. E. (2013). Mechanical Behavior of Materials, 4th ed. Pearson, Boston.

Worked Examples

Published examples this tool reproduces; each page lists the inputs to enter and the printed answers.

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