Abstract
The degradation process of 316L stainless steel caused by cavitation was investigated by means of finite element analysis. The damage characteristics of metal specimens subjected to the cavitation bubble collapse process were recreated by simulation with a micro-jet water hammer. The simulation results were compared with the cavitation pits created in the experimental tests. In the experiment, different inlet and outlet pressures in a test chamber with a system of barricade exciters differentiated the erosion process results. Hydrodynamic cavitation caused uneven distribution of the erosion over the specimens’ surface, which has been validated by roughness measurements, enabling localisation and identification of the shape and topography of the impact pits. The erosion rate of the steel specimens was high at the beginning of the test and decreased over time, indicating the phase transformation and/or the strain-hardening of the surface layer. A numerical simulation showed that the impact of the water micro-jet with a velocity of 100 m/s exceeds the tensile strength of 316L steel, and produces an impact pit. The subsequent micro-jet impact on the same zone deepens the pit depth only to a certain extent due to elastoplastic surface hardening. The correlation between post-impact pit geometry and impact velocity was investigated.
Highlights
The degradation process of 316L stainless steel caused by cavitation was investigated by means of finite element analysis
The stress response characteristic of the micro-jet hammering process was explored by a comparison of the impact pit depths created at different impact velocities and pit geometries created in experimental tests [17]
316L stainless steel was performed for impact velocities between 100 and 500 m/s
Summary
The degradation process of 316L stainless steel caused by cavitation was investigated by means of finite element analysis. The damage characteristics of metal specimens subjected to the cavitation bubble collapse process were recreated by simulation with a micro-jet water hammer. There is a tendency to increase the specific speed of newly built machines Both conditions lead the cavitation erosion effects to be noticed more often. Cavitation is a multiphase phenomenon, involving multiple vapour bubbles (gas nuclei) to be created and collapse, that normally occurs at high frequency in a turbulent flow, during rapid acceleration of the liquid. This causes the pressure waves to generate and propagate through the liquid and structure. The nucleation process is described in both the theory and observations for flowing and quiescent liquids [1]
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