Chapter 11 Water Shock Experiments on Automotive Underbody Panels Kevin A. Gardner, Jeremy D. Seidt, and Amos Gilat Abstract Automotive underbody panels are susceptible to water shock loading that can be generated by driving over a puddle at high speeds. The thin panels can be permanently deformed or fail if the loading is large enough. Aluminum underbody panels are bolted into a custom test rig and subjected to water jet loading from a commercial pressure washer. The force on the panels is measured using four load cells and displacement data is captured using three-dimensional image correlation. The flow field is characterized using orthogonally mounted high speed cameras to determine the jet velocity. Additional experiments are performed using a custom water cannon that fires slugs of water contained in latex balloons at the underbody panels. This more accurately recreates the water splash event created when driving over a puddle. The velocity and shape of the water slugs are measured using orthogonally mounted cameras. Keywords Fluid-Structure Interaction • Water Shock • Digital Image Correlation • Experimental Mechanics • Automo- tive 11.1 Introduction Current releases of LS-DYNA [1] allow the user to study fluid-structure interactions with both the compressible and incompressible solvers. This provides a powerful design tool that can be used to help trim weight from automobiles. Automotive underbody panels are typically stamped from thin sheet metal or molded with polymers. These panels are intended to improve aerodynamics and provide protection for exposed components. Weight reduction is one of the simplest methods for improving fuel economy and can be accomplished by thinning the automotive panels. However, if underbody panels are made too thin they can become prone to deformation or failure from water shock loading. Driving over a puddle at high speeds causes a water shock that can hit the underbody panel directly or glance off of other components before hitting the panel. Experimentally validated results from fluid-structure interaction simulations can be used to predict and prevent the failure of underbody panels while optimizing their design to save weight and material. Many researchers have studied fluid-structure interactions in different scenarios and loading configurations. Deformation of steel plates subjected to underwater impulsive loading was investigated using a custom test apparatus [2]. A large water chamber is incorporated into a gas gun to generate the loading. Test plates were bolted onto the end of the water chamber and deformations were tracked using shadow moiré techniques. The deformation of composite structural plates subjected to underwater blast loadings has also been investigated using a test setup that replicates common fluid-structure interactions [2–4]. 11.2 Experimental Automotive underbody panels are primarily subjected to water shock loadings when driving over a puddle at high speeds. The interaction of the tires with the puddle creates high velocity sprays and splashes that impact the underbody panel. In order to match conditions observed by production vehicles and eliminate the need for fabricating lab scale test panels, full size aluminum underbody panels were using during the testing. The aluminum panels were bolted into the test rig using existing mounting holes. The panel holder was constructed of solid steel box beam and was vertically supported by linear bearings. K.A. Gardner () • J.D. Seidt • A. Gilat The Ohio State University, Department of Mechanical and Aerospace Engineering, Columbus, OH, USA e-mail: kevin.gardner.796@gmail.com © The Society for Experimental Mechanics, Inc. 2018 P. Zavattieri et al. (eds.), Mechanics of Biological Systems, Materials and other topics in Experimental and Applied Mechanics, Volume 4, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-63552-1_11 75