The water hammer effect is the basis of technologies which is artificially responsible for the decay of continuous jets. A recently developed technique enhances the pressure fluctuations using an acoustic chamber, leading to enhanced erosion effects for various water volume flow rates. The optimum standoff distance for an ultrasonic enhanced water jet is not appropriately estimated using an inclined trajectory. The objective of this study is to comprehend the true nature of the interaction of the standoff distance following the stair trajectory and traverse speed of the nozzle on the erosion depth. Additionally, it also critically compares the new method (staircase trajectory) that obeys the variation in frequency of the impingements for defined volume flow rates with the inclined trajectory. In this study, at constant pressure (p = 70 MPa), the role of impingement distribution with the variation of traverse speed (v = 5–35 mm/s) along the centerline of the footprint was investigated. The maximum erosion depth corresponding to each traverse speed is observed at approximately same standoff distance (65 ± 5 mm) and decreases with the increment in traverse speed (h = 1042 and 47 µm at v = 5 and 35 mm/s, respectively). The results are attributed to the variation in the number of impingements per unit length. The surface and morphology analysis of the cross-section using SEM manifested the presence of erosion characteristics (micro-cracks, cavities, voids, and upheaved surface). By varying the water cluster, different impingement densities can be achieved that are suitable for technological operations such as surface peening, material disintegration, or surface roughening.

This study compared the effect of the interaction time of periodic water clusters on the surface integrity of AISI 304 tungsten inert gas (TIG) welded joints at different excitation frequencies, as the effect of the technological parameters of pulsating water jet (PWJ) on the mechanical properties of TIG welded joints are under-researched. The TIG welded joints were subjected to different frequencies (20 and 40 kHz) and traverse speeds (1–4 mm/s) at a water pressure of 40 MPa and a standoff distance of 70 mm. The effect of the interaction of the pulsating jet on the material and the enhancement in its mechanical properties were compared through residual stress measurements, surface roughness, and sub-surface microhardness. A maximum enhancement in the residual stress values of up to 480 MPa was observed in the heat-affected zone, along with a maximum roughness of 6.03 µm and a maximum hardness of 551 HV using a frequency of 40 kHz. The improvement in the surface characteristics of the welded joints shows the potential of utilizing pulsed water jet technology with an appropriate selection of process parameters in the treatment of welded structures.

More efficient ways to process materials are constantly being sought, even in the case of continuous water flow technology, which acts on materials mainly by stagnant pressure. An alternative method is an ultrasound-stimulated pulsating water jet, the basis of which is the repeated use of impact pressure, which reduces the time interval for mechanical relaxation. This article focuses on a comparative study from the point of view of water mass flow rate on material penetration and its integrity. Relatively low pressures (p = 20, 30, and 40 MPa) with varying nozzle diameters (d = 0.4 and 0.6 mm) were used to identify the effectiveness of the pulsating water jet. The time exposure of the jet at a fixed place was varied from t = 0.5 to 5 s for each experimental condition. The results showed that with an increase in the pressure and diameter values, the disintegration depth increased. In addition, the surface topography and morphology images showed signs of ductile erosion in the form of erosion pits, upheaved surfaces, and crater formation. The microhardness study showed an increase of 10% subsurface microhardness after the action of the pulsating water jet as compared to the original material.

Friction stir welding (FSW) is a solid-state joining technique that bonds materials without reaching their melting point. In this process, the tool plays a central role by generating the frictional heat necessary for welding, which directly influences weld quality, productivity, and production costs. This study focuses on analyzing both the temperature of the FSW tool and the wear it experiences during operation. The tool used in this investigation is made from SS410 stainless steel and is employed to weld AA 6061-T6 aluminum alloy under varying process parameters. Post-weld thermal imaging captures the temperature distribution of the tool, revealing a peak temperature of approximately 500 °C. Notably, the tool shoulder surface records the highest temperature during welding. To further understand wear mechanisms, a field emission scanning electron microscope (FESEM) is used to examine the wear patterns on the tool’s shoulder and pin. Several distinct wear sites are identified and subjected to detailed FESEM analysis. The results highlight that the tool shoulder surface endures the most significant wear due to direct contact with the workpiece material. Despite being originally designed with a narrow thread profile, the FESEM analysis reveals complete thread erosion during the welding process. Additionally, the tool shoulder edges exhibit pronounced damage resembling lightning strikes. The FESEM images also show crater formations, fractured surfaces, and surface delamination on the shoulder. This comprehensive study provides valuable insights into the complex wear behavior of FSW tools. The findings contribute to optimizing tool design and welding parameters, ultimately enhancing tool longevity and the overall efficiency of the welding process.