A theoretical model for wave propagation across solid–fluid interfaces with fluid–structure interaction (FSI) was explored by conducting experiments. Although many studies have been conducted on solid–solid and fluid–fluid interfaces, the mechanism of wave propagation across solid–fluid interfaces has not been well examined. Consequently, our aim is to clarify the mechanism of wave propagation across a solid–fluid interface with the movement of the interface and develop a theoretical model to explain this phenomenon. In the experiments conducted, a free-falling steel projectile was used to impact a solid buffer placed immediately above the surface of water within a polycarbonate (PC) tube. Two different buffers (aluminum and polycarbonate) were used to examine the relation between wave propagation across the interface of the buffer and water and the interface movement. With the experimental results, we confirmed that the peak value of the interface pressure can be predicted via acoustic theory based on the assumption that projectile and buffer behave as an elastic body with local deformation by wave propagation. On the other hand, it was revealed that the average profile of the interface pressure can be predicted with the momentum conservation between the projectile and the buffer assumed to be rigid and momentum increase of fluid. The momentum transmitted to the fluid gradually increases as the wave propagates and causes a gradual decrease in the interface pressure. The amount of momentum was estimated via the wave speed in the fluid-filled tube by taking into account the coupling of the fluid and the tube.

An understanding of the impact response of glass plates is important to protect people from injury. We investigated the fracture mode of a float glass plate that fractured under a low-velocity impact and conducted a numerical simulation. First, an impact fracture experiment of a float glass plate was carried out using a dropping weight, and crack development in the thickness direction of the glass plate was observed by a shadowgraph method. Then the numerical simulation was conducted applying two types of material models to the float glass: the Johnson-Holmquist model and the elastic model with tensile pressure failure. The two models were used in a simulation and the results were compared with the experimental result. At an impact velocity of 4.43 m/s, which correspond to the deformation velocity of the glass plate of 6.1 m/s in deflection, simulation with the Johnson-Holmquist model could reproduce the strain response of the glass plate but it could not reproduce the fracture mode of the glass plate. This result implied the limitation of applying the damage model to low-velocity impact for simulating the fracture mode of a glass plate. In the material model with elastic as the constitutive law and tensile pressure failure as the failure model, the simulated fracture strength of the glass plate was the same as the experimental fracture strength, and the fracture mode showed characteristics of the bending fracture mode that was observed in the experiment, although the fracture initiation time of the glass plate was slightly delayed in the strain history. In the low-velocity impact where the influence of inertia was small, the glass plate response could be reproduced easily using the elastic model. The efficacy of the model was confirmed in the simulation result with several deformation velocities. the impact object is large so that the loading area is large, and it is caused by the tensile stress acting on the non-impact surface by bending deformation. Additionally, the range in which breakage occurs is wide. The Hertzian fracture mode occurs when the impact speed is fast, the impact object is small so that the loading area is small, and it is caused by shear stress from the stress concentration on the impact surface. This fracture mode is characterized by a small fracture area and a conical fragment of the Hertzian cone. In our previous study, we conducted a low-velocity impact test of the float glass plate at a colliding velocity of 4.43 m/s. The test result implied that the fracture mode of the glass plate is a mixed-mode of bending and Hertzian fractures under this condition (Kojima et al. 2018). Further study is necessary to investigate how it changes according to the velocity. So far, we also conducted the quasi-static indentation test and the three-point bending test to observe the fracture mode of the float glass. It was confirmed that the glass was fractured in the bending mode in quasi-static conditions. The trapezoidal crack which is the characteristic of the Hertzian mode fracture did not appear (Momo...

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Please cite this article as: Kojima T, Inaba K, Numerical analysis of wave propagation across Solid-Fluid interface with Fluid-Structure interaction in circular tube, International Journal of Pressure Vessels and Piping (2020), doi: https://doi.

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