Abstract
Processing using multifunction cavitation (MFC) has recently enabled functional characteristics to be imparted to various materials. It is possible to process a material surface in the same manner as with conventional water jet (WJ) peening; however, the cavitation bubble temperature is different. To further improve this MFC technology, we examine the surface re-forming of low alloy steel (JIS-SCM435) using MFC with various modes of ultrasonic waves. The ultrasonic equipment used for MFC processing includes dual, single, pulse and frequency modulation (FM) ultrasonic modes. Improvement of the residual stress and corrosion resistance was confirmed for all modes. The dual mode showed the maximum values of residual compressive stress and surface potential. The sound pressure at the machining spot was the highest with dual mode, and the temperature in the bubble generated by the WJ nozzle was highest and the amount of dissolved oxygen was lowest. Improvement of the residual stress and corrosion resistance was promoted because the temperature and pressure in the bubble interior during processing was higher than in the other modes.
Highlights
Peening is a technique used to improve the fatigue strength and the stress corrosion cracking resistance of metal parts, due to work hardening and plastic deformation of the surface layer by strong tapping of the material surface
To further improve this multifunction cavitation (MFC) technology, we examine the surface reforming of low alloy steel (JIS-SCM435) using MFC with various modes of ultrasonic waves
The sound pressure at the machining spot was the highest with dual mode, and the temperature in the bubble generated by the water jet (WJ) nozzle was highest and the amount of dissolved oxygen was lowest
Summary
Peening is a technique used to improve the fatigue strength and the stress corrosion cracking resistance of metal parts, due to work hardening and plastic deformation of the surface layer by strong tapping of the material surface. Water jet peening (WJP) [1] [2] [3] [4] [5] is a peening method that utilizes the cavitation phenomenon, and it is applied for preventive maintenance [2] in nuclear. It is possible to reduce the tensile residual stress generated in a structure by welding or machining. When the WJP technique is applied to a structure, stress corrosion cracking [1] and metal fatigue [1] [6] can be prevented
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