Sandwich armor structures with aluminum foam can be utilized to protect a military vehicle from harmful blast load such as a landmine explosion. The metal foam has the ability to control backface deformation, without sacrificing ballistic efficiency behind targets with highly deforming back plates, via a mechanism that will be discussed. In armor system 10, the closed-cell metal foam is effective in containing rearward deformation of the strike plate 11 in a ballistic target structure.The pores can be sealed (closed-cell foam) or interconnected (open-cell foam). IntroductionOur solar system is scary that's why my new book, 'tyger burning' takes place in it In this episode I take a look at an NC State R&D project involving a ne.A metal foam is a cellular structure consisting of a solid metal (frequently aluminium) with gas-filled pores comprising a large portion of the volume. The results show that the blast-resistant capability of the innovative sandwich armor structure with the isolating layer increases remarkably. An isolating layer between the aluminum foam and the vehicle floor is introduced to remediate this drawback. However, a severe blast load causes force enhancement and results in much worse crew injury. It is found that a sandwich armor structure with only aluminum foam is capable of mitigating crew injuries under a moderate blast load.This unexpected phenomenon is called “force enhancement” and needs to be considered in vehicle armor design. Besides all these benefits, an undesired phenomenon observed when using foam material for blast protection is that, under certain conditions, the peak force transmitted to the protected structure can be even higher than when the foam material is not used. The porus nature of the foam helps in heat dissipation and also provides acoustic damping. Metal foam is an ideal choice of sacrificial material for blast protection due to its low density, a characteristic that is very preferable for lightweight applications. Armor structures are usually employed to protect a military vehicle and crew from these extreme loads. According to the material’s inventor the material would make a great bumper, as the sponginess of the metal foam soaks up impact energy.For ground vehicles, blast loads from landmine explosions and ballistic loads from a bullet or a missile produce much damage to the vehicle structure and result in severe injuries to crew members.Altair HYPERMESH and LS-PREPOST were utilized for pre- and post-processing, respectively. In this study, the finite element models were developed for numerical simulations based on the LS-DYNA platform. Numerical techniques, such as the finite element method, are employed for blast process simulation as well as for structural damage analyses. Moreover, testing of structural damage processes from the blast loads is no easy task either. Modeling DescriptionThe blast process is both difficult and expensive to test. An isolating layer is introduced to the sandwich armor structure, which is demonstrated to be effective in mitigating the crew injury based on numerical simulation results.
The armor, which consists of a back aluminum panel and a layer of aluminum foam, is attached to the vehicle floor for enhanced blast-resistant capabilities of the vehicle.The back facesheet of the two types of sandwich panel is made of aluminum alloy AA6061-T4 with mechanical properties: mass density kg/m 3, Young’s modulus GPa, Poisson’s ratio , initial yield strength MPa, and ultimate strength MPa. Underbody armor is a kind of protective structure mainly used against threats from the ground. Underbody Armor ModelIn order to protect the crew members of a military vehicle at the time when dangerous loads, such as landmine blast load, are exerted on the vehicle body, it is essential to add an armor structure to the vehicle body. The FE model consists of 56851 elements with 60204 nodes. Properties of various materials, such as steel, rubber, and glass, in the model were imported from other publicly available FE vehicle models. The geometric information in the FE model was based on the CAD data of the vehicle obtained from the Internet. Since the aluminum is insensitive to the strain rate dependency, here the strain rate dependency is neglected. The sheets are represented by material model 24 (*MAT_PIECEWISE_LINEAR_PLASTIC) provided by LS-DYNA. Figure 1 shows the typical engineering stress-strain curves for the aluminum alloy AA6061-T4. This model includes the strain rate effect of the foam material under high speed impact loads. FE model of underbody armor plate for blast protection.Material model MODIFIED_CRUSHABLE_FOAM of LS-DYNA was used to represent the material behavior of the aluminum foam. The aluminum foam material in use has the following material properties: kg/cm 3, MPa, , , , , MPa, , MPa, and. The nodes of different components are tied together along the material interface. Both the aluminum panel and the aluminum foam are modeled by reduced one-point integration brick element. All ps2 emulatorsThe revolutions of the dummy are represented by spring elements with viscous damps. Figure 3 shows the 50th percentile male GEBOD dummy model the model is comprised of fifteen rigid bodies that represent the lower torso, middle torso, upper torso, neck, head, upper arms, forearms, and hands, and upper legs, lower legs, and feet of the dummy. Various dummy models for vehicle crashworthiness design have been developed, from very complicated FE models with thousands of degrees of freedom (DOF) to much simpler rigid body models. Crew ModelCrash dummy models are usually included in tests and simulations to predict occupant responses under different crash loads these responses will be used to guide the crashworthiness design. Strain rate effect of aluminum is accounted by using the Cowper and Symonds model. Is the displacement of the suspension base and can be obtained from the integral of. Here, and are the stiffness and the damping coefficient of the suspension. In this work, the GEBOD dummy model shown in Figure 3 is employed for blast protection design because of its low computational cost and an acceptable error level.The equation of occupant-seat model can be formulated as Where is the displacement vector, , , and are the mass matrix, the stiffness matrix, and the damping matrix, respectively and and are given as and. Due to the computational efficiency of this dummy model, a total of six GEBOD dummies were put at different positions in the LAV for the simulation. Studied crew member responses in a light armored vehicle (LAV) subjected to a mine blast load by using the GEBOD rigid body dummy model incorporated in LS-DYNA. Used the standard Hybrid III crash test dummy to study the lower leg injuries occurring in antitank mine strikes. Pokemon bricks bronze download pcBy selecting appropriate values for and , various decay characteristics can be indicated.The solution methodology of wave propagation for the front and back facesheet of the composite sandwich structures is given by Hoo Fatt and Surabhi. The predicted time-dependant blast overpressure is expressed asWhere and are the peak incident overpressure and the peak reflected overpressure, respectively, is the positive phase duration time, and and are decay coefficients. The model takes into consideration the angle of incidence of the blast, , the incident pressure, , and the reflected pressure. This model, which has been implemented as the *LOAD_BLAST loading card in LS-DYNA, can predict the blast overpressure under certain conditions: the free air detonation of a spherical charge and the surface detonation of a hemispherical charge the surface detonation approximates the conditions of a mine blast. This empirical model is based on the CONWEP air blast function developed by Kingery and Bulmash.
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