Finite Element Studies of Transient Wave Propagation

The National Bureau of Standards (NBS) has been working to develop a nondestructive test method for heterogenous solids using transient stress waves [1-5]. The method is referred to as the impact-echo method. The technique involves introducing a transient stress pulse into a test object by mechanical impact at a point and measuring the surface displacement caused by the arrival of reflections of the pulse from internal defects and external boundaries. Successful signal interpretation requires an understanding of the nature of transient stress wave propagation in solids containing defects. A primary focus of the NBS program is on using the finite element method to gain this understanding.</p

Evaluation of coupled finite element/meshfree method for a robust full-scale crashworthiness simulation of railway vehicles

The crashworthiness of a railway vehicle relates to its passive safety performance. Due to mesh distortion and difficulty in controlling the hourglass energy, conventional finite element methods face great challenges in crashworthiness simulation of large-scale complex railway vehicle models. Meshfree methods such as element-free Galerkin method offer an alternative approach to overcome those limitations but have proved time-consuming. In this article, a coupled finite element/meshfree method is proposed to study the crashworthiness of railway vehicles. A representative scenario, in which the leading vehicle of a high-speed train impacts to a rigid wall, is simulated with the coupled finite element/element-free Galerkin method in LS-DYNA. We have compared the conventional finite element method and the coupled finite element/element-free Galerkin method with the simulation results of different levels of discretization. Our work showed that coupled finite element/element-free Galerkin method is a suitable alternative of finite element method to handle the nonlinear deformation in full-size railway vehicle crashworthiness simulation. The coupled method can reduce the hourglass energy in finite element simulation, to produce robust simulation

Design and numerical assessment of a rapid-construction corrugated steel-concrete-steel protective structure

A protective structure should be sufficiently resilient to protect its occupants from the harmful effects of an impact or explosion. In many instances, protective structures are also required to be assembled quickly, and be cost-effective. Steel-concrete-steel (SCS) sandwich structures combine the benefits of steel; ductility and anti-scabbing, and concrete; energy absorption and rigidity. Despite these favourable characteristics, the performance of profiled-plate steel-concrete-steel structures under blast and impact loads has yet to be studied in detail. This article presents the results from a numerical study investigating the efficacy of a newly proposed profiled-plate arched steel-concrete-steel structure under the loading from an extremely near-field high explosive detonation. It is observed that as arch thickness (concrete infill depth) increases, a greater proportion of energy is absorbed through concrete crushing and a larger concrete mass is mobilised. It is shown that a 240 mm arch thickness is adequate to resist the blast load from a 5.76 kg TNT charge, therefore proving the suitability of the proposed protective structure