Sivasrinivasu Devadula

Kerf profile generated by abrasive waterjet (AWJ) machining process has always been an interesting area as it dictates the quality of the part. However, due to the non-deterministic nature of the process, it is a challenging task to predict it. On the other hand, understanding and controlling the kerf profile in multi-layered structures (MLSs) is a further difficult task as various layers made of different materials respond to erosion in a different manner and results in a completely different kerf shape (barrel or x-shaped kerf profile) due to the material removal mechanisms dependency on the material property of the specific layers, jet divergence and position of specific layer. Therefore, it is important to understand and develop predictive models of resulting kerf profile in MLSs so that they can be used in controlling the accuracy of the resulting kerf which in turn dictates the final part accuracy. The attempts in this direction are very limited although some modeling efforts are reported in homogeneous materials (metals, ceramics). For the first time, an analytical model for predicting the kerf profile generated in MLS machining with AWJ was presented in this research work. Discretized form of Hashish model was used for determining depth of cut. The effect of jet divergence from the experimentally obtained values, upon passing through the upper layer has been considered. The developed predictive model was validated by the kerf shapes obtained from the experimental trials on metal-adhesive-rubber MLS. Kerf profiles obtained from the simulations have captured the resulted convergent-divergent (X-shaped) profile, while cutting metal-rubber laminate composite, effectively. Furthermore, the effectiveness of the proposed analytical model was demonstrated by generating the various kerf shapes generated at various jet traverse rates.

In high-value industries (aerospace, automobile, defense, etc.), various applications like assembly, engine cylinder bores, etc., require hole making with target size/shape, tolerances, and surface quality. The present study investigates the potential of the micro-AWJs (df = ~300 µm) in trepanning holes by considering Aluminum 6061-T6 alloy, as a case study. However, the stochastic, non-deterministic, and flexible nature of the AWJs result in holes with deviated form and dimensional characteristics that lead to part rejection. As the waterjet pressure (P) is the most significant parameter in dictating jet energy, material removal, and productivity, trepanning studies were carried out to investigate the waterjet pressure’s influence on the hole form, dimensional, and surface characteristics. Furthermore, the effect of P on productivity measures in terms of material removal rate (MRR) is investigated. From the results, the edge radius of the hole at the entry plane improved with a higher P by 30.19%. With the increase in the P, the hole diameter deviation from the nominal diameter and circularity error decreased by 10 and 58.88% at the top plane and 11 and 65.2% at the bottom plane. Cylindricity error and taper angle decreased by 11.84 and 15.23% at higher P. Uncut material size and burr length at the exit plane decreased by 43.48 and 24.77% at higher P and the MRR increased by 52.71%. Surface morphology was studied concerning the pressure, with the increases in the jet pressure surface roughness improves, and waviness increases. Micrographs were taken with the help of HRSEM to analyze the effect of P on material removal mechanism, it is observed that at lower P abrasive embedment is a visible phenomenon.