Hypervelocity impact simulations of Whipple shields

The problem associated with protecting space vehicles from space debris impact is described. Numerical simulation is espoused as a useful complement to experimentation: as a means to help understand and describe the hypervelocity impact phenomena. The capabilities of a PC-based hydrocode, ZeuS, are described, for application to the problem of hypervelocity impact. Finally, results of ZeuS simulations, as applied to the problem of bumper shield impact, are presented and compared with experimental results

Music Education in Bali

This article explores what it means to be a music educator within the context of Balinese Gamelan and Balinese culture. It explores the differences between how teachers teach and how they become teachers in this context and the model in the United States for becoming a teacher and teaching models

Impact and Ricochet of a High Speed Projectile from a Plate

A computational study of a projectile (either 2024 aluminum or TiAl6V4 titanium alloy) impacting a plate (either titanium alloy or aluminum) is presented in this paper. Projectile velocity (ranging from 250 m/s to 1500 m/s) with varying impact angles are considered. The presence of ricochet (if any) is identified over the ranges of the projectile velocity and impact angle considered. For the cases where ricochet is identified, the ricochet angle and velocity are predicted as functions of the incident angle and the incident velocity. The numerical results are compared with an analytical solution of the ricochet problem. The analytical solutions are from a model developed to predict the ballistic ricochet of a projectile (projectile) penetrator. The dynamics and the deformation of an aluminum (or a titanium alloy) projectile impacting on a finite thickness titanium alloy (or aluminum) plate are simulated. The current work is interesting in that it looks in the field of ballistics of different material combinations than are traditionally studied. The present simulations based on detailed material models for the aluminum and the titanium alloy and the impact physics modelling features in the LS-DYNA code provide interesting details regarding the projectile/plate deformations and post-impact projectile shape and geometry. The present results indicate that for no cases (for specified incoming velocities and impact angles considered) can an aluminum projectile penetrate a titanium alloy plate. The ricochet ‘mode predictions ‘obtained from the present simulations agree well with the ricochet ‘mode predictions’ given in an analytical model

Material model for modeling clay at high strain rates

This paper was accepted for publication in the journal International Journal of Impact Engineering and the definitive published version is available at http://dx.doi.org/10.1016/j.ijimpeng.2015.11.005Modeling clay is a soft malleable material made from oils and waxes. This material is fundamental for ballistic evaluation of body armors because it is used as backing material in ballistic tests. After a ballistic impact, a back-face indentation is measured to assess performance of the armor. Due to the important role of modeling clay in this particular application, its mechanical characterization and comprehension of penetration mechanics are essential for development of new personal protection systems. This paper presents a two-step computational methodology to calibrate parameters of a Cowper-Symonds material model for modeling clay at characteristic strain rates up to 1.8×104 s-1. In the first stage, a high-speed camera is used to record the penetration of a gas-gun launched cylindrical mass with a hemispherical cap into a block of clay. Image-processing software is used to capture the tail of the projectile as it penetrates into the clay. These data are then used to sample the penetration depth as function of time. In the second stage, an in-house developed model of penetration, based on both the spherical cavity expansion theory and the Tate penetration equation, is used to determine, by inverse analysis, the parameters of the Cowper-Symonds clay model. The proposed constitutive relationship for clay and the determined material parameters can be applied accurately to problems involving high strain rates

The Application Of The Norton-Bailey Law For Creep Prediction Through Power Law Regression

Accurate determination of constitutive modeling constants used in high value components, especially in electric power generation equipment, is vital for related design activities. Parts under creep are replaced after extensive deformation is reached, so models, such as the Norton-Bailey power law, support service life prediction and repair/replacement decisions. For high fidelity calculations, experimentally acquired creep data must be accurately regressed over a variety of temperature, stress, and time combinations. If these constants are not precise, then engineers could be potentially replacing components with lives that have been fractionally exhausted, or conversely, allowing components to operate that have already been exhausted. By manipulating the Norton-Bailey law and utilizing bivariate power-law statistical regression, a novel method is introduced to precisely calculate creep constants over a variety of sets of data. The limits of the approach are explored numerically and analytically. Copyright © 2013 by ASME