Fatigue Crack Growth and Crack Closure in Vacuum

Abstract

For S35C medium carbon steel and A5083-O aluminum alloy, fatigue crack growth tests were carried out in vacuum and in air under ΔK-increasing-decreasing condition, and crack growth rates and crack closure behavior were investigated in detail. In addition, ΔK constant tests were performed in air-to-vacuum-to-air environment. Fractographical study indicates that the material ahead of the crack tip deforms more easily in vacuum than in air. The crack opening point KOP under ΔK increasing condition was lower in vacuum than in air within the limit of present experiments, and Kop under ΔK-decreasing condition was found to increase with the decrease of ΔK. Fatigue crack growth resistance of material was increased in vacuum and the degree of increase was found dependent on material and crack growth rate regime. The variable environment test results show that fatigue crack growth resistance is hardly affected by environment history. © 1985, The Japan Society of Mechanical Engineers. All rights reserved.