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This work investigates the effect of eardrum perforations and myringosclerosis in the mechanical behavior of the tympano-ossicular chain. A 3D model for the tympano-ossicular chain was created and different numerical simulations were made, using the finite element method. For the eardrum perforations, three different calibers of perforated eardrums were simulated. For the micro perforation (0.6 mm of diameter) no differences were observed between the perforated and normal eardrum. For the numerical simulation of the eardrum with the largest perforation caliber, small displacements were obtained in the stapes footplate, when compared with the model representative of normal ossicular-chain, at low frequencies, which is related with major hearing loss in this frequency range. For the numerical simulations of myringosclerosis, the larger differences in the displacement field between the normal and modified model were obtained in the umbo. When observing the results in the stapes footplate, there were no significant differences between the two models, which is in accordance to the clinical data. When simulating an eardrum perforation along with myringosclerosis, there is a decrease in the displacements, both from the umbo and the central part of the stapes footplate, often associated with a pronounced hearing loss. It could be concluded that the reduced displacement of the stapes footplate may be related to a greater hearing loss.

An axisymmetric smoothed particle hydrodynamics (ASPH) with contact algorithm is presented to simulate the normal perforation of aluminum plates. Traditional ASPH considering contact implicitly by conservation equations has the problem of virtual tensile stresses and shear stresses for perforation simulation. To overcome the problem, a particle-to-particle contact algorithm is employed to treat contact interfaces explicitly in the present method. An artificial stress method is extended for the method to remove tensile instability. The present method is firstly validated by three test cases. Then, it is used to simulate the normal perforation of aluminum plates with ogive-nose steel projectiles. Numerical simulation results show that the method predicted residual velocities of projectiles in good agreement with the experimental data.

In this paper, perforations of 12mm thick Weldox 460E steel plates by 20mm diameter blunt projectiles are simulated based on Two-dimensional Smoothed Particle Hydrodynamics method (SPH), and the modified Johnson–Cook (MJC) material model is adopted. To describe the shear plugging process, the particle approximation between different materials is canceled, and only the particle contact model based on the principle of conservation of momentum is applied. Then the separation of projectile and plug is simulated successfully, which is consistent with the experimental observations. Furthermore, it can be found that the particle size has a great influence on the calculation by comparing the effects of the different SPH particle sizes on plugging calculations. In general, the smaller the particle size is, the greater the residual velocity of projectile is. The residual velocities are tending towards stability as the decrease of particle size. Taking computational efficiency and accuracy into consideration, 0.033 (size$=$0.4mm) is the most appropriate dimensionless particle size. Then, the effect of target thickness on perforation is conducted, which shows that the target thickness has certain influence on the global deformation of target. Moreover, the sensitivity of MJC material constants on the residual velocity of projectile is also analyzed and discussed using orthogonal experimental design method and the range analysis method. The results indicate that the most sensitivity parameter is yield strength $A$, followed by strain hardening modulus $n$ and strain hardening exponent $B$.

Axisymmetric and three-dimensional smoothed particle hydrodynamics (SPH) models are developed to simulate normal and oblique perforation of 12 mm-thick Weldox 460 E steel plates. In the models, a particle-to-particle contact algorithm including friction effect is employed to model interactions between projectile and target plate. A constitutive model coupling viscoplasticity and ductile damage is implemented to describe material behaviors of target plate. Both axisymmetric and three-dimensional SPH models are validated by existing experimental results. By using axisymmetric models, effects of projectile structure on normal perforation are systematically studied. Two factors of projectile structure, nose shape and aspect ratio, are considered. Residual velocities, ballistic limits and failure modes are obtained for different projectile nose shapes and aspect ratios. Effects of nose shape and aspect ratio on ballistic limits predicted by SPH simulations are compared with those obtained by an analytical equation. By using three-dimensional models, oblique perforation is simulated. Effects of oblique angle on impact processes are analyzed. Intervals of critical oblique angle of ricochet are obtained for different impact velocities and caliber-radius-head values of ogival projectile. The results obtained in this work can provide reference for the design of protective structures with steels and similar materials. The SPH with contact algorithm including friction effect is proved to be a very effective method for ballistic impact simulation.

Penetration of flat-ended cylindrical projectiles into thin laminated composite plates was investigated analytically and experimentally. An analytical modeling was carried out for thin laminated composite plates by developing a new function for deflection by computing Von Karman nonlinear strains and by using the principle of energy balance. During the perforation process, different regions were considered for the plate, such as fracture region, elastic deformation region, delamination region, and undeformed region. The energy absorbed by each region was measured in small time intervals. To validate this model, the ballistic experiment is performed on the thin laminated composite plate near and beyond ballistic limit velocity. The samples were made from plain woven glass/epoxy using a hand lay-up method. In addition to the initial velocity, the residual velocity of the projectile was also measured using two parallel laser curtains. A comparison drawn between analytical and experimental results demonstrated a good consistency in the residual velocity of the projectile. Finally, the distribution of strains along the plate thickness direction over time, the different amounts of absorbed energy of the failure modes, delamination radius, and energy are assessed at near and beyond ballistic limit velocity.

Tsunamis have damaged bridges with various configurations to different extents. This paper reports an experimental investigation of the tsunami loads on two types of bridge configurations, namely bridges with solid and perforated parapets. The results reveal that the maximum forces acting on the bridge deck with 60% perforated parapets are about 17% lower than the one with solid parapets. However, the percentage of force reduction is found to be smaller than the percentage of perforation area in the parapets. It is also noted that the perforated parapets in the bridge deck can substantially reduce the tsunami forces acting on it throughout the force time-history. Hence, as far as the horizontal forces are concerned, the experimental results indicate that the bridge with perforation in parapets would suffer less damage as compared to the one with solid parapets because of the smaller energy input into the structure.

A numerical simulation of penetration/perforation process of a concrete slab by a cylindrical steel projectile using the Smoothed Particle Hydrodynamics (SPH) method is studied in the paper. In the simulation, the available hydrocode AUTODYN2D is employed with the improved RHT concrete model, in which a Unified Twin-Shear Strength (UTSS) criterion is adopted in defining the material strength effects, and constructed a dynamic multifold limit/failure surfaces including elastic limit surface, failure surface and residual failure surface. The proposed model is incorporated into the AUTODYN hydrocode via the user defined subroutine function. The results obtained from the numerical simulation are compared with available experimental ones. Good agreement is observed. It demonstrates that the proposed model can be used to predict not only the damage areas and velocity reduction of the projectile during the perforation process but also the debris clouds of spalling process.