Influence of traverse trajectory overlapping of pulsating water jet on surface homogeneity and topography

UltrasonicQuery Pulsating Water Jet (PWJ) technology is studied for its potential to utilize the impact pressure (hammer effect) of individual droplets for surface modification and texturing. Although promising results have recently been achieved, indicating the potential use of impact pressure for controlled surface roughening, the determination of trajectory overlap has so far been based on theoretical assumptions regarding the diameter of the PWJ. Recent findings suggest that the velocity distribution across the PWJ is not uniform. This implies fluctuations in impact pressure distribution and the resulting compressive stresses, which may also be harnessed for controlled erosion. The goal is to achieve the most homogeneous surface treatment process. The aim of this study is to investigate how different pass-to-pass transverse displacement (TD) values influence the effectiveness and homogeneity of PWJ surface treatment. The methodology involved monitoring the pass-to-pass TD of the PWJ within the ranges of 25%, 50%, 75%, and 100% of the measured original groove width after a single pass. This approach subsequently modifies the effective overlap factor (OF) between successive passes. The findings demonstrate that a 25% TD consistently yields the most homogeneous surface, as confirmed by optical and profile analyses. While roughness (Ra) values were comparable between 25 and 50% TD, the 25% setting produced superior surface regularity. Notably, a six-pass treatment at 25% TD produced a valley-dominated topography (Rsk = -0.60), which is highly desirable for applications requiring enhanced load-bearing capacity. These results provide a practical methodology for optimizing PWJ surface treatments and advancing their application in precision engineering.