Overload Effect on Fatigue of AerMet 100 Steel
Abstract
Overloads have been reported to perturb the steady state fatigue crack growth condition and retard the crack growth. The retardation effect is known to depend on material plasticity, slip planarity, microstructure, overload ratio, and background stress intensity range delta K and load ratio R. Extensive studies have been conducted to identify the effect of a single overload (or spike load) in terms of the number of delayed cycles. This study was initiated to understand the effect of a single overload on the threshold fatigue crack growth in AerMet 100 steel as a function of R-ratio and environment. A single 100% overload (or overload ratio 2) was applied after the fatigue crack growth rate da/dN reached the threshold one (5 x 10(exp -10) m/cycle) in the K-decreasing test of load shedding. The background load and the corresponding overload were stepped up until the crack began to grow after each loading of 5 x 10(exp -5) cycles. Subsequently, the fatigue test was continued under constant amplitude loading at various R-ratios, ranging from -1.1 to 0.9, and frequency of 10 Hz in air and vacuum of 5 x 10(exp -8) torr. The overload-induced increase in the threshold stress intensity range delta K(th) was taken as the measure of overload retardation effect. Furthermore, the overall results were analyzed in terms of two parameters, delta K(th) and maximum stress intensity at threshold K(max).
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2000
- Accession Number
- ADA378011
Entities
People
- E. Lee
- K. Sadananda
Organizations
- Naval Air Warfare Center