HCA Approach to Topography Design Optimization of a Structure for Fluid Structure Interaction (original) (raw)
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Effect of blast wave on lightweight structure performance
The use of explosives to attack vehicles has been increased during the last few years. The terror attacks lead to death of innocent people. The armored vehicles should be protected from explosives attacks using lightweight sandwich structure. In this study, the protection system against blast effect is highlighted using composite structures to protect vehicles. The response of the light composite structure is studied using 3-D finite element analysis (FEA). The blast field test is conducted and used to verify the 3-D numerical model. The composite structure strengthened by aluminum foam (ALF) is used to protect the bottom of the armored vehicle against the blast wave propagation. The ALF is used to fill the space at the sandwich structure as a light weight material. This study presents a comparison between the results obtained by both the reviewed field blast tests and the FEA to validate the accuracy of the 3-D finite element model. The effects are expressed in terms of displacement-time history effect on the sandwich steel panels as the explosive wave propagates. The results obtained by the reviewed field blast tests have a good agreement with those obtained by 3-D numerical model. The ALF improves the performance of the sandwich structure under the impact of blast loading. The light weight sandwich structure could be used as a mitigation system to protect the bottom of the armored vehicles against blast hazard.
Vehicle Hull Shape Optimization for Minimum Weight Under Blast Loading
2013
: Shape structural optimization for blast mitigation seeks to counteract the damaging effects of an impulsive threat on occupants and critical components. The purpose of a vehicle energy-deflecting hull is to mitigate blast energies by channeling blast products and high-pressure fluids away from the target structure. Designs of pyramid‐shaped protective structures have been proposed in existing and concept vehicle's platforms. These structures are more effective than the traditional flat-plate designs in terms of cabin penetration and weight. Studies on other blast concept design remain scarce. This investigation addresses the design of blast‐protective structures from the design optimization perspective. The design problem is stated as to finding the optimum shape of the protective shell of minimum mass satisfying a deformation and envelops constraints. Performance improvements are observed as the envelope constraint is relaxed and the optimization problem includes a larger num...
Investigation of Plate Structure Design under Stochastic Blast Loading
2013
1 Abstract The protection of lightweight ground vehicle crews from rapid acceleration events in hostile operating environments is an active field of study in defense research. Vehicle up-armoring traditionally entails the upgrading of standard shells with additional sacrificial components to improve blast protection capabilities. Resulting weight increment diminishes effectiveness and speed, increases vulnerability, and wears out vehicle components more quickly. This research furthers efforts in shape optimization relevant to blast events by incorporating robust design methods and the use of LS-DYNA to apply dynamic loading conditions in FEA simulations. The objective of this investigation is to establish a reliability-based robust design (RBRDO) methodology in blast mitigation. This approach controls the reliability of the protective shell while reducing the variance of the deflection performance caused by the variation of the uncontrollable environmental factors, namely the magnit...
2010
Structural optimization efforts for blast mitigation seek to counteract the damaging effects of an impulsive threat on critical components of vehicles and to protect the lives of the crew and occupants. The objective of this investigation is to develop a novel optimization tool that simultaneously accounts for both energy dissipating properties of a shaped hull and the assembly constraints of such a component to the vehicle system. The resulting hull design is shown to reduce the blast loading imparted on the vehicle structure. Component attachment locations are shown to influence the major deformation modes of the target and the final hull design. INTRODUCTION Gross vehicle acceleration, often measured in peak and sustained g's, is of interest in the vehicle level blast mitigation problem. Unlike frontal crash events, the acceleration of the vehicle achieved during a blast event translates to vertical loads exerted on the pelvis and compression of the spinal cord, resulting in ...
Shock Waves, 2016
Light armored vehicles (LAVs) can be exposed to blast loading by landmines or improvised explosive devices (IEDs) during their lifetime. The bottom hull of these vehicles is usually made of a few millimeters of thin armored plate that is the vehicle's weak point in a blast-loading scenario. Therefore, blast resistance and blast load redirection are very important characteristics in providing adequate vehicle as well as occupant protection. Furthermore, the eccentric nature of loading caused by landmines was found to be omitted in the studies of simplified structures like beams and plates. For this purpose, blast wave dispersion and blast response of centrally and eccentrically loaded flat-, U-, and V-shaped plates are examined using a combined finiteelement-smoothed-particle hydrodynamics (FE-SPH) model. The results showed that V-shaped plates better disperse blast waves for any type of loading and, therefore, can be successfully applied in LAVs. Based on the results of the study and the geometry of a typical LAV 6 × 6, the minimum angle of V-shaped plates is also determined. Keywords Blast wave • Blast dispersion • Blast response • SPH model • Blast loading Communicated by C. Needham and A. Higgins.
Multi-Material Structural Topology Optimization for Blast Mitigation Using Hybrid Cellular Auomata
51st AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference<BR> 18th AIAA/ASME/AHS Adaptive Structures Conference<BR> 12th, 2010
Design for structural topology optimization is a method of distributing material within a design domain of prescribed dimensions. This domain is discretized into a large number of elements in which the optimization algorithm removes, adds, or maintains the amount of material. The resulting structure maximizes a prescribed mechanical performance while satisfying functional and geometric constraints. Among different topology optimization algorithms, the hybrid cellular automaton (HCA) method has proven to be efficient and robust in problems involving large, plastic deformations. The HCA method has been used to design energy absorbing structures subject to crash impact. The goal of this investigation is to extend the use of the HCA algorithm to the design of an advanced composite armor (ACA) system subject to a blast load. The ACA model utilized consists of two phases: ceramic and metallic. In this work, the proposed algorithm drives the optimal distribution of a metallic phase within the design domain. When the blast pressure wave hits the targeted structure, the fluids kinetic energy is transformed into strain energy (SE) inside the solid medium. Maximum attenuation is reached when SE is maximized. Along with an optimum use of material, this condition is satisfied when SE is uniformly distributed in the design domain. This work makes use of the CONWEP model developed by the Army Research Laboratory. The resulting structure shows the potential of the HCA method when designing ACAs.
Experimental and Numerical Study of a Combined Blast and Ballistic Protection
Applied Mechanics and Materials, 2014
The work presented in this paper concerns a project on the optimization of protections subjected to explosions (IED's threat). Explosions generate two types of threats for a protective structure: blast and impact of fragments. Perforating and non-perforating impact tests were performed in our laboratory with steel spherical projectiles impacting a target based on Kevlar ® textile layers and a crushable material, Crushmat ® . These tests required to develop a specific experimental test setup in order to contain the composite protective structure and to be able to measure the relevant parameters. The experiments allow us to determine the ballistic performance and basic parameters of the protection, and to validate finite element numerical models (LS-DYNA) resulting in a performant prediction tool. The approach used for the simulation consists in the representation of the full textile architecture with solid elements. Therefore, the textile material is explicitly represented in the model in order to have a good representation of the physical phenomena occurring during impact. For the crushable material, a representation using SPH was chosen in order to take the granular behaviour of this material into account. Good results are obtained with such models. However, these models are very complicated and computing time consuming. The geometry has to be well adapted and symmetry has to be exploited. On the other hand, representation of a granular material with SPH does not take into account some characteristics of this material during impact, such as the pulverisation process of the granular material. Solutions to take these phenomena into account in the model are proposed.
Weight and Blastworthiness Design Considerations for Military Ground Vehicle Safety Optimization
ode.engin.umich.edu
Occupant safety is a top priority of military vehicle designers. Recent trends have shifted safety emphasis from the threats of ballistics and missiles toward those of underbody explosives. For example, the MRAP vehicle is increasingly replacing the HMMWV, but it is much heavier and consumes twice as much fuel as its predecessor. Recent reports have shown that fuel consumption is no longer solely an environmental or economic issue, but also a safety concern; a significant percentage of fuel convoys that supply current field operations experience casualties en route. While heavier vehicles tend to fare better for safety in blast situations, they contribute to casualties elsewhere by requiring more fuel convoys. This study develops an optimization framework that uses physics-based simulations of vehicle blast events and empirical fuel consumption data to calculate and minimize combined total expected injuries from blast events and fuel convoys. Results are presented by means of two parametric studies, and the utility of the framework is discussed in a dynamic context and for evaluating casualty-reduction strategies.