Surface protection

Although in many cases residual stress is considered detrimental to component lifetime, it may also be used to provide protection against failure. Ultrasound Impact Treatment (UIT) was first developed in the Soviet Union in the 1970’s but is now being commercially exploited.

A high vibration speed ultrasonic indenter is used as a post-weld treatment to locally transform a detrimental stress into a more beneficial one.

The near-surface stress state resulting from UIT was studied by making use of the SALSA radial collimator optics which allows measurement of details as close as 40 micrometres from the surface. The use of collimators allows both stress and peak shape analysis to be performed. The figure shows the resulting residual stress profiles for an 8 mm UIT treated stainless steel plate.

Ref.: A. Evans.