Drop impact causes severe surface erosion, dictating many important natural, environmental and engineering processes and calling for substantial prevention and preservation efforts. Nevertheless, despite extensive studies on the kinematic features of impacting drops over the last two decades, the dynamic process that leads to the drop-impact erosion is still far from clear. Here, we develop a method of high-speed stress microscopy, which measures the key dynamic properties of drop impact responsible for erosion, i.e., the shear stress and pressure distributions of impacting drops, with unprecedented spatiotemporal resolutions. Our experiments reveal the fast propagation of self-similar noncentral stress maxima underneath impacting drops and quantify the shear force on impacted substrates. Moreover, we examine the deformation of elastic substrates under impact and uncover impact-induced surface shock waves. Our study opens the door for quantitative measurements of the impact stress of liquid drops and sheds light on the origin of low-speed drop-impact erosion.
Bibliographical noteFunding Information:
We thank Ben Druecke, Tai-yin Chiu, and Grace Lee for help with experiments and data analysis and Michelle Driscoll for fruitful discussions. This research is supported by the US National Science Foundation CBET-2017071 and 2002817 and ACS Petroleum Research Fund 60668-ND9. T.-P.S. acknowledges the partial financial support of the PPG fellowship via UMN IPRIME and the Government Scholarship to Study Abroad from Taiwan. F.A.-N., K.A., L.G., and P.G. acknowledge the financial support of the grants ANID/CONICYT Fondecyt Iniciación No. 11170700 and 11191106.
© 2022, The Author(s).
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