Modelling of cantilever subjected to air-blast

This paper considers the response of cantilevers subjected to air-blast. The response of cantilevers (e.g. lamp-posts, street signs) had been observed and this was used to assess the effective energy yield of the two nuclear weapons dropped at Hiroshima and Nagasaki in 1945. Since then, a number of other researchers have also considered the behaviour of simple cantilevers of various cross-sections to monitor the blast parameters. The cantilevers considered in this paper are circular in cross-section and are assumed to have a ductile failure mode. It is observed that after being loaded the ductile cantilevers were straight throughout the entire length except at the clamped end where the cantilever was bent through an angle ?˚. Thus for the cantilever subjected to blast pressure, the critical parameter was the angle of deformation at the base. The tool used for simulation of cantilever response is AUTODYN- 3D (version 4.3). This software is specifically suitable for analysis of non-linear dynamics problems. In AUTODYN state-of-the-art analysis coupled with modern graphics provide appropriate environment for solving complicated engineering problems. Thus AUTODYN is an engineering and scientific tool for solving complex problems. AUTODYN is the right tool for analysis of nonlinear dynamic problems, which includes deflection of cantilever, and variation of material properties. This software has special features which enable the dynamic analysis of a cantilever subjected to varying pressure with time. Also AUTODYN has options to include strain-rate effects in the analysis of the problem. In special cases user defined subroutines can be incorporated in AUTODYN. AUTODYN has multi-processor system. For material modelling different processors namely, Euler, Lagrange, Arbitrary Lagrange Euler (ALE), Shell and Beam are available, which may be chosen corresponding to type of material. In this paper twenty cantilever specimens of 3mm and 5mm diameter and of length ranging from 50 mm to 700 mm were considered. These cantilever specimens were subjected to pressure of 50 kPa. Cowper-Symonds strain rate model is used for the analysis as used strain-rate is 2.72 ×106s-1. Details of the results obtained from numerical simulation using AUTODYN are presented in this paper. These results are also compared with earlier experimental results obtained by the author at Pulau-Senang.