Simultaneous Application of Static and Dynamic Loads on Sonic Fatigue Test Articles. Supplement 1. Considerations of the Theoretical Aspects of Acoustic Fatigue
Rept. for Jun 1962-Jun 1963
NORTHROP CORP HAWTHORNE CA NORAIR DIV
Pagination or Media Count:
A theory of acoustic fatigue is proposed which is based on a general theory of fatigue of metals. The theory is based on the proposition that the problem is better understood if attention is focused on the growth of the crack which is responsible for the ultimate failure. One significant manner in which the present theory differs from others is that it invokes a stress dependent limiting condition on the crack growth to determine the cycles for failure. Representing the result of acoustic input as one of random stress response, expressions are derived for the prediction of time to failure. Indications are that the rate at which the damage is accruing in acoustic fatigue is strongly dependent upon the low stress end of the distribution function and the failure conditions and the associated probabilities of failure are strongly determined by the high stress end that is, the tail of the distribution function. Another important result of the analysis is that in any acoustic fatigue simulation tests, one has to take into account the design mean stress for which the structure is designed. This design mean stress not only influences the total time to failure but it also strongly affects the probabilities of failure by essentially changing the origin of the distribution function curve.