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Stress Engineering

PreStress Engineering Division (PreStressED)

Redistribution of Residual Stresses
Ultrasonic Peening

Is a comparatively recent and promising technology that is based on the use of High Power Ultrasound (HPU). In most industrial applications, HPU involves power levels of hundreds to thousands of watts, and ultrasonic systems are operating in the frequency ranges from 15 kHz to 100 kHz with typical amplitudes range from about 10 to 40 microns.

The development of the Ultrasonic Peening (UP) technology was a logical continuation of the work done before directed on the investigation and further development of known before techniques for surface plastic deformation such as shot peening and hammer peening. During the different stages of its development the UP process was also known as "ultrasonic treatment" (UT), "ultrasonic impact technique/technology/treatment" (UIT) and ultrasonic impact peening (UIP)

See the historical review on UP in IIW Document XIII - 2010 - 04

The UP produces a number of beneficial effects in metals and alloys. Foremost among these is increasing the resistance of materials to surface-related failures, such as fatigue and stress corrosion cracking. One of the promising ways of industrial application of UP is the post-weld treatment of welded elements and structures. The results of fatigue testing showed that the UP is the most efficient and economical technique for fatigue life improvement of welded elements and structures as compared to the existing improvement treatments such as grinding, TIG-dressing, shot peening, hammer peening etc.

UP Equipment
Basic UP systems for manual (left) and robotic (right) applications

The UP technology is considered a leading technology in the application of High Power Ultrasound (HPU) for fatigue life improvement of parts and welded elements because of the following factors:
  • The UP technology is based on over 30 years extensive experience and knowledge of an international group of experts in application of HPU for improvement of quality and service life of parts and welded elements. The first publications of the group on relieving of residual stresses in welded elements are dated back to 1974.
    See the historical review on UP in IIW Document XIII - 2010 - 04
  • The design of the UP equipment is based on "Power on Demand" concept. The power and other parameters of UP equipment correspond to the necessary changes in residual stresses, stress concentration and mechanical properties of the surface layers of materials to attain maximum possible increase in fatigue life of welded elements. The basic UP system covers most of the applications in fatigue improvement with the power consumption of 300-500 watt. More powerful UP systems could be designed and produced on request.
  • The effects of improvement treatments, particularly the UP treatment, on the fatigue life of welded elements depend on the mechanical properties of used material, the type of welded joints, parameters of cyclic loading and other factors. For the effective application of the UP, depending on the above-mentioned factors, a software package for Optimum Application of Ultrasonic Peening was developed that is based on an original predictive model. In the optimum application, a maximum possible increase in fatigue life of welded elements with minimum time-, labor- and power-consumption is thought.

A number of research projects were completed to optimize the UP process and to find the efficiency of UP for different applications such as the increasing of the fatigue life of welded elements, eliminating of distortions caused by welding and other technological processes, residual stress relieving, increasing of the hardness of materials. At present time, we can perform the UP of materials, parts and real structures as a service by ourselves or to provide the equipment for UP.

Advantages of UP:
  • High (highest) efficiency
  • Quick (~ 0,5 m of weld/min)
  • Much less noise, vibration and easier to use than hammer peening
  • Deeper penetration
  • Computer controllable
  • Robotic line - ready
  • Lighter (total weight of UP system is only 6 kg) and no need for forced water cooling compared to similar magnetostrictive systems
Ultrasonic Peening: Areas of Application

Referenced Documents
Info on UP Info on UP 2005 Info on UP 2005
UP History, Technology & Equipment IIW Document XIII - 2010 - 04IIW Document XIII – 2010 – 04
Rehabilitation & Repair by UP IIW-2076-05IIW-2076-05

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