Tensile creep rupture at cyclic load variation

Abstract

Assuming the validity of the life fraction rule the life time is calculated for creep rupture of material subjected to tensile cyclic stress variation. Two cases are considered: a saw tooth stress-time profile with zero and non-zero holding period. The life times and hence the number of cycles at fracture can be predicted by means of values from the static stress-rupture diagram ( n, τ o, τ max ) and values characterizing the stress cycle ( a, ν, t H ). The calculations for zero holding period are compared to experiments performed on the stainless steel type: DIN 1.4970 at 700°C. Very good agreement is obtained for loading conditions leading to shorter rupture times.