Some aspects of the damage caused in metallic materials by ultrasonic vibrations

Abstract

There has been a number of studies on the influence of ultrasonic vibrations on various metallurgical phenomena. In the present study, however, some investigations have been carried out on a relatively less familiar aspect of ultrasound, viz. its application towards bringing about a rapid fatiguing effect on materials under resonant conditions. Intense ultrasound was given to materials under resonance conditions to produce fracture in them by what is known as ultrasonic fatigue. The failure time was usually of the order of a few minutes and, sometimes, only a few seconds. Some well-known common materials such as commercially pure aluminium, age-hardenable aluminium alloys and armco iron in different heat-treated conditions were chosen for this study. The specimens were of dumb-bell shape conforming to resonance. The complete equipment for this purpose was designed, developed and fabricated in-house. Some aspects of the damage under these conditions are discussed here, primarily through fractography. The fractures appear to be different from conventionally produced fractures. The influence of ultrasonic loading (short of fracture) in affecting the strength of age-hardenable alloys is also discussed briefly, X-ray line broadening analysis seems to indicate a strong recovery of the matrix due to the rapid fatiguing effect.