H.W. Liu

A quantitative analysis of structure sensitive fatigue crack growth in steels

Abstract A quantitative theory for structure sensitive fatigue crack growth is constructed. The theory relates fatigue crack growth rate to mean free path for dislocation motion, Youngs modulus and yield strength. The theory agrees well with the measured growth rates in a number of steels.

A kinetic analysis of high temperature fatigue crack growth

Abstract : The increased fatigue crack growth rate at high temperature is primarily caused by environmental effects. The amount of the environmental effect depends on the penetration rate of the detrimental chemical specie relative to the crack growth rate. Depending upon the relative chemical penetration rate, there can either be no, partial, or full environmental effects. In both cases of no or full environmental effects, da/dN is not sensitive to cyclic frequency and temperature. In the case of partial environmental effect, da/dN is controlled by the rate of the transport of the detrimental chemical specie to crack tip, and da/dN is both frequency and temperature dependent. The da/dN data of IN 100, Waspaloy, and 304 stainless steel were analyzed. The data seem to support the analysis. (Author)

Fatigue in detrimental gaseous environments

Reports on the application of Sabatiers Principle to correlate the reverse bending fatigue life of ASTM A36 tested in N/sub 2/, CH/sub 2/Cl/sub 2/, CHCl/sub 3/ and CCl/sub 4/ gaseous environments. Tests ASTM A515 steel in the CHCl/sub 3/ and CH/sub 2/Cl/sub 2/ gaseous environments resulting in an identical correlation; however, the environmental effects were more severe. Concludes that the presented approach can be used to correlate data from both fatigue life and crack growth experiments. Suggests its extension to more complex chemical environments.