DETECTION OF FATIGUE-CRACK PROPAGATION WITH ACOUSTIC-EMISSION

Since its inception, acoustic emission has held great promise as a too l for detection and evaluation of damage in structures. Of particular concern is the occurrence of fatigue manifested by the processes of cr ack initiation followed by crack growth to failure. Early research rel ated acoustic emission parameters to physical variables, including loa d, stress, pressure etc. causing damage. In this paper, relationships relating acoustic emission to fatigue crack growth are developed. Acou stic emission equations, similar to Paris' law, are derived which allo w determination of the stress intensity factor and the crack growth ra te. These principles are embodied in a second-generation system which automatically and continuously determines these parameters. The approa ch is applied in the laboratory as well as to structures including bri dges, air frames and transmission towers for electrical power.