Overlapping adjacent passes of abrasive slurry jets can be used to fabricate micro-pockets or blind micro-slots. This study investigates the propagation of surfaces milled using overlapping passes of a high-pressure abrasive slurry jet on a ductile 6061-T6 target over a wide range of aspect ratios. Features such as shallow pockets with low aspect ratios to deep slots with aspect ratios ∼1.5 were fabricated to investigate the correlations between the aspect ratio, degree of pass overlap, and number of repeating passes with the machined surface evolution characteristics. A comprehensive model was presented that combined computational fluid dynamics (CFD) with surface evolution to predict the evolving machined feature topography after each of the overlapping and repeating passes, and to provide insights into experimental observations. The model explicitly considered the CFD-predicted local particle impact angles and velocities as well as effects due to secondary impacts, high sidewall slopes, and stagnation effects. For larger degrees of overlap, measurements revealed a more than linear rate of increase in depth after each repeat of two adjacent overlapped passes, as opposed to a linear depth increase for smaller overlaps and blind pockets. Large overlaps were found to result in asymmetric features. Up to a critical aspect ratio of ∼0.65, the model predicted the surface evolution of the features to within <8.6% of those measured. Beyond that, randomness in the machined feature shape and size made the process challenging to control and the surface evolution difficult to predict. Nevertheless, the model was able to elucidate the reasons for the randomness and other observed phenomena such as the more than linear growth in etch rate, and the occurrence of feature asymmetry. The findings emphasize that flow confinement, increases in the jet's turbulent kinetic energy, and the formation of vortices at the bottom of the machined features are critical factors influencing the machining process, and that in these cases explicit modeling approaches like the one presented in this study must be used.

中文翻译：

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考虑流体限制效应，用重叠磨料浆喷射足迹铣削的高纵横比特征的形貌预测

磨料浆射流的重叠相邻通道可用于制造微凹坑或盲微槽。本研究研究了使用高压磨料浆料射流在各种纵横比范围内的延展性 6061-T6 目标上重叠经过铣削的表面扩展情况。制造了诸如低深宽比的浅凹坑和深宽比~1.5的深槽等特征，以研究深宽比、道次重叠程度和重复道次数量与加工表面演变特征之间的相关性。提出了一个综合模型，将计算流体动力学 (CFD) 与表面演化相结合，以预测每次重叠和重复通过后不断演变的加工特征形貌，并提供对实验观察的见解。该模型明确考虑了 CFD 预测的局部粒子撞击角度和速度，以及二次撞击、高侧壁坡度和停滞效应造成的影响。对于较大程度的重叠，测量结果表明，每次重复两次相邻的重叠路径后，深度的增加速度超过线性，而较小的重叠和盲袋的深度则呈线性增加。发现大量重叠会导致特征不对称。在临界纵横比约为 0.65 的情况下，该模型预测特征的表面演化与测量结果的误差小于 8.6%。除此之外，加工特征形状和尺寸的随机性使得该过程难以控制，并且表面演变难以预测。尽管如此，该模型能够阐明随机性和其他观察到的现象（例如蚀刻速率的线性增长以及特征不对称的发生）的原因。研究结果强调，流动限制、射流湍流动能的增加以及加工特征底部涡流的形成是影响加工过程的关键因素，在这些情况下，像本研究中提出的显式建模方法必须使用。