NONDESTRUCTIVE EVALUATION OF METAL FATIGUE.
SOUTHWEST RESEARCH INST SAN ANTONIO TEX DEPT OF ELECTRONICS AND ELECTRICAL ENGINEERING
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Methods investigated for generating and focusing Rayleigh waves are presented. Transducer design considerations and fabrication methods employed are summarized and discussed. The selection of specimen materials and designs are presented, including engineering drawings of the steel and aluminum fatigue specimens. Experimental results obtained from small drilled holes in a number of specimen materials and geometries using surface wave techniques plane wave are shown including a number of Polaroid photographs of the reflection signal patterns. Results obtained from methods investigated for focusing Rayleigh waves are presented. Ultrasonic plane wave and magnetic inspection results on steel fatigue specimen No. 18 containing a tiny fatigue crack are given. Many inspection records and surface photographs are also shown. Reproductions of Polaroid photographs of ultrasonic signal patterns obtained while stress cycling an aluminum specimen are shown. Inspection records showing a large increase in signal amplitude corresponding with the development of fatigue damage in the form of a crack are included. X-ray diffraction measurements, using a 0.004-inch diameter collimator, were made in the vicinity of the tip of a small fatigue crack, and the results of these measurements are reported. Author