ISSN:
1741-2765
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract This paper is concerned with recent applications of ultrasonic acoustic waves to characterizing fatigue-crack propagations in “part-through-crack” (PTC) specimens. A simple ultrasonic system recently developed is described in detail. Emphasis of the description is paid to the practical aspects of instrumentation and operation of this system which is based on the interaction of cracks with acoustic surface waves. The received signal contains information of the character of a static or a propagating crack. The sensitivity of the system mainly due to its highresolution power makes it particularly suitable for studying plasticity effects in fatigue-crack propagations. Of special importance, the present techique provides direct, experimental evidence on the crack-closure phenomenon and convenient means for measuring the amount of this closure, together with its associated crack-tip resistance. The significance of these parameters is discussed in terms of analytic predictions based on the residual deformations at the crack tip. Important fracture-mechanics quantities discussed, which are obtainable from the surface-wave test data, include: the instantaneous crack geometry and its variations with changing load conditions, the closure and resistance phenomena at the crack tip due to the material ductility, stress relaxations for sustained loads, and environmental effects on moving cracks. To get more general fracture-mechanics information, the present ultrasonic system can be simultaneously coupled to acoustic-emission detectors.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02324859
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