Usually, energy generated from an explosive’s detonation is transferred partly in the form of the blast impulse and some in the form of the kinetic energy of casing fragments. When detonation occurs in an explosive casing, it breaks the casing into fragments of different weights with varying velocities. The extent of destruction by these energized fragments depends upon the initial velocity they gain after an explosion. The momentum gained by the fragments decides the capability to perforate a barrier or propagate an explosion. A three-dimensional non-linear FEA method is used to model a box-shaped steel structure. This box-shaped structure is subjected to an internal cased explosion for estimating the initial and striking velocities of primary fragments. The effect of varying charge weight and the effect of the sacrificial wall on the initial and striking velocity of fragments via numerical simulations are also carried out. The initial and striking velocity values obtained through simulation are compared with the design guidelines of the code-based approach, and a good agreement is reported.
A typical conventional aerial bomb is a streamlined cylinder with an outer casing, inner explosive material, a fuse to ignite the explosive filling, an arming mechanism for fuse and an optional tail unit. The outer casing is usually metallic with a pointed nose at the tip for better aerodynamic characteristics. The present work mainly focuses on Finite Element (FE) simulation of aerial bomb impact using Ansys Explicit Dynamics for imported three-dimensional model of aerial bomb using Solid Edge. FE simulation was carried out to find stresses and deformation limits for two varied impact distances between Bomb and fixed target fields. Further, the impact simulation results were validated by analytical solutions.
The present investigation deals with the characterization of tensile behavior of various Fiber Reinforced Polymer composites under Thermo-Mechanical loading. Five different types of Uni-Directional (UD) composites of Carbon, Glass, Carbon-Glass hybrid and Metal Laminates of Carbon & Glass were tested for tensile behavior. Tensile tests were performed at strain rates of 10-3, 10-2, & 10-1 s-1 at Room Temperature,250 0C and 450 0C. Stress-strain relations reveal the strain rate and temperature sensitive behavior of composites. Glass, Glass-Carbon, Glass-metal epoxy composites showed higher peak tensile stress under room temperature with varying strain rates as compared to neat carbon epoxy composites. Also, high strain rate tensile properties such as peak stress and peak strain of Glass-Carbon-Epoxy specimens were 26%, and 60% higher than that of the neat carbon epoxy composite. The failure mechanisms of both the composites were analyzed through scanning electron microscopy. The composites mainly failed due to matrix crack within elastic range under room temperature and failed with significant plastic deformation of matrix and fibers under test temperatures 250 0C and 450 0C. Finally, this study reveals that the continuous phase of metal layer embedded between Uni-Directional Glass and Carbon fiber, based composite system can be tailored to act as an energy-absorbing material system under both elastic and plastic stress strain regimes.
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