Ultrasonic Pulsating Water Jet Peening: Influence of Pressure and Pattern Strategy.

Gabriel Stolárik,Akash Nag,Sergej Hloch,Jana Petrů,Jaroslava Svobodová

doi:10.3390/ma14206019

Abstract

Peening techniques are nowadays attracting more research attention due to their association with the extending of the service life and improving surface texture of engineering components. Ultrasonic pulsating water jet peening represents a new way of mechanical surface treatment. Accelerated water droplets via hammer effect cause small elastic-plastic deformations on the surface. This work deals with peening of aluminum alloy using an ultrasonic pulsating water jet, where periodically acting water droplets were used as the peening medium. The aim of the work was the feasibility study of the peening process and to observe the effects of pressure (p = 10, 20 and 30 MPa) and pattern trajectory (linear hatch and cross hatch). The peened surfaces were analyzed by the surface roughness profile parameters Ra and Rz and the microhardness along the peening axis into the material. Graphically processed results show a clear increase of measured values with increasing pressure (p = 10, 20 and 30 MPa), where the roughness values ranged from 1.89 µm to 4.11 µm, and the microhardness values ranged from 43.3 HV0.005 to 47 HV0.005, as compared to 40.3 HV0.005 obtained for the untreated sample. The achieved results indicate potential using of an ultrasonic pulsating water jet as a new method of surface treatment of metals. By controlled distribution of water droplets, it is possible to achieve a local distribution of surface roughness, and at the same time, strengthening of the subsurface layers in the material without thermal influence on the material.

Highlights

Surface treatment with continuous water jet (CWJ) is based on the principle of influencing the high-velocity water jet toward the target material with initial impact pressure acting for a shorter duration, followed by the stagnation pressure ps, which acts for the maximum duration of the impact and can be calculated using Equation (1) [8]
The increasing trend of microhardness was attributed to the induction of higher comIn this experiment, the effect of pulsating water jet (PWJ) on the surface topography of the material in pressive stresses in the material, as discussed previously [30]
The experimental roughness trend, the microhardness trend showed the opposite dependency with the type conditions were set such that it was possible to clearly compare the influence of the of pattern trajectory

Summary

Introduction

Wear is mainly initiated on the surface of the component in the form of cracks or increased roughness of the material Another negative factor affecting the service life of parts is the induced residual tensile stress caused by previous machining [2,3]. Some methods to overcome these shortcomings are already in practice, such as shot peening and laser peening [4] These surface treatment methods cause some limitations, such as in the shot peening process, the induction of compressive residual stresses are limited to a certain depth. One of the possibilities is water jet (WJ) technology, where the material is removed or the surface is treated using a highspeed water jet that impacts the component [6]. Surface treatment with continuous water jet (CWJ) is based on the principle of influencing the high-velocity water jet toward the target material with initial impact pressure acting for a shorter duration, followed by the stagnation pressure ps , which acts for the maximum duration of the impact and can be calculated using Equation (1) [8]

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Conclusion