Lebon G S Bruno, Tzanakis Iakovos, Pericleous Koulis, Eskin Dmitry
Brunel Centre for Advanced Solidification Technology, Brunel University London, Uxbridge UB8 3PH, UK; Computational Science and Engineering Group, University of Greenwich, 30 Park Row, London SE10 9LS, UK.
Brunel Centre for Advanced Solidification Technology, Brunel University London, Uxbridge UB8 3PH, UK; Faculty of Technology, Design and Environment, Oxford Brookes University, Oxford OX33 1HX, UK.
Ultrason Sonochem. 2018 Apr;42:411-421. doi: 10.1016/j.ultsonch.2017.12.002. Epub 2017 Dec 5.
In an attempt to quantify the instantaneous pressure field in cavitating liquids at large forcing signals, pressures were measured in four different liquids contained in vessels with a frequency mode in resonance with the forcing signal. The pressure field in liquid metal was quantified for the first time, with maximum pressures of the order of 10-15 MPa measured in liquid aluminium. These high pressures are presumed to be responsible for deagglomeration and fragmentation of dendritic intermetallics and other inclusions. Numerical modelling showed that acoustic shielding attenuates pressure far from the sonotrode and it is prominent in the transparent liquids studied but less so in aluminium, suggesting that aluminium behaviour is different. Due to acoustic shielding, the numerical model presented cannot adequately capture the pressure field away from the intense cavitation zone, but gives a good qualitative description of the cavitation activity. The results obtained contribute to understanding the process of ultrasonic melt treatment (UST) of metal alloys, while facilitating further the guidelines formulation and reproducible protocols for controlling UST at industrial levels.
为了量化在大驱动信号下空化液体中的瞬态压力场，在与驱动信号共振的频率模式下，对容器中包含的四种不同液体的压力进行了测量。首次对液态金属中的压力场进行了量化，在液态铝中测得的最大压力约为10 - 15兆帕。这些高压被认为是枝晶金属间化合物和其他夹杂物解聚和破碎的原因。数值模拟表明，声屏蔽会使远离超声换能器的压力衰减，在所研究的透明液体中这种现象很明显，但在铝中则不太明显，这表明铝的行为有所不同。由于声屏蔽，所提出的数值模型无法充分捕捉远离强烈空化区的压力场，但对空化活动给出了很好的定性描述。所获得的结果有助于理解金属合金的超声熔体处理（UST）过程，同时进一步促进工业层面控制UST的指导方针制定和可重复方案。
