Projectiles with three different nose shapes (blunt, hemispherical and conical) have been used in gas gun experiments to penetrate 12 mm thick Weldox 460 E steel plates. Based on the experimental results, the residual velocity curves of the target material were constructed and compared. It was found that the nose shape of the projectile significantly affected both the energy absorption mechanism and the failure mode of the target during penetration. The ballistic limit velocities were about equal and close to 300 m/s for hemispherical and conical projectiles, while it was considerably lower for blunt projectiles. Blunt projectiles caused failure by plugging, which is dominated by shear banding, while hemispherical and conical projectiles penetrated the target mainly by pushing the material in front of the projectile aside. Also, the residual velocity curves were influenced by nose shape, partly due to the differences in projectile deformation at impact. The experimental study, given in this part of the paper forms the basis for explicit finite element analysis using the commercial code LS-DYNA presented in Part II of the paper.
"Finally, the fracture is propagated through the necking circle while the indenter pushes the plate. For specimen C20 (Fig. 5b), the indenter provokes a local shear ring at its perimeter which is named shear circle or shear banding  . These specimens suffer small local indentation and plastic deformation outside the shear circle. "
[Show abstract][Hide abstract] ABSTRACT: Experimental and numerical results of drop weight impact tests are presented, examining the plastic response and the crack initiation and propagation of small-scale clamped rectangular aluminium plates laterally impacted by different indenter shapes. The experiments are conducted using a fully instrumented impact testing machine. The shape of the deformation of the specimens and the process of initiation and propagation of the material fracture is presented. The obtained force-displacement responses show a good agreement with the simulations performed by the LS-DYNA finite element solver. The strain hardening of the material is defined using experimental data of quasi-static tensile tests and the critical failure strain is evaluated measuring the thickness and the width at fracture of the tensile test pieces. The results show that the absorbed energy to perforate the specimens is highly sensitive to the shape of the striker. Thus, the crack propagation for each striker type is analysed in terms of the force-displacement response. The failure modes are described by the matrix of the infinitesimal strain tensors and the shape of the deformation of the failing elements.
Journal of Offshore Mechanics and Arctic Engineering 10/2015; 137(5):051402. DOI:10.1115/1.4030725 · 0.57 Impact Factor
"The ballistic limit velocity of a target plate is severely affected by the nose shape of the projectile under the given impact conditions. Regarding the targets discussed in  , the hemispherical and conical projectiles gave a ballistic limit velocity close to 300 m/s; whereas, for blunt projectiles it was considerably lower, i.e. 185 m/s. Generally, it may be concluded that the effectiveness of a threat is governed by many parameters depended on given impact conditions, a target material, its thickness and a projectile nose shape. "
"However, no investigation into the SIP subjected to windborne debris impact has been found in the literatures. Various testing facilities including drop weight, pendulum, catapult , Hopkinson pressure bar and gas gun have been utilized for impact testing     . In accordance with the above mentioned testing guideline  and FEMA P-320/361  , large projectile cannon facilities have been developed at TTU and UF to simulate windborne debris impacts. "
[Show abstract][Hide abstract] ABSTRACT: Natural disasters such as cyclone, hurricane, tornado and typhoon cause tremendous loss around the world. The windborne debris usually imposes high speed localized impact on the building envelope, which may harm people inside the building and create dominant openings. A dominant opening in the building envelope might cause internal pressure increasing and result in substantial damage to the building structures, such as roof lifting up or even collapse. To withstand the impact of such extreme event, the penetration resistant capacity of wall or roof panels to windborne debris impact should meet the requirements specified in the wind loading codes, e.g., the Australian Wind Loading Code (AS/NZS 1170.2:2011). In this study, a composite Structural Insulated Panel (SIP) with Extended Polystyrene (EPS) core sandwiched by flat metal skins that is commonly used in building industry was investigated. To study the structural response and penetration resistant capacity of the composite panel against windborne debris impacts, a series of laboratory tests were carried out by using a pneumatic cannon testing system. The effects of various specimen configurations, impact locations and debris impact velocities on their performance were investigated. The failure modes under various projectile impact scenarios were observed and compared by using two high-speed cameras. The dynamic responses were examined quantitatively in terms of the opening size, residual velocity of projectile, deformation and strain time histories on the back skin measured in the tests. The penetration resistance capacity of the panels subjected to windborne debris impact were examined and analyzed. In addition, numerical models were developed in LS-DYNA to simulate the response and damage of the composite SIP under windborne debris impact. Laboratory tested panels were first modeled. The test data was used to calibrate the accuracy of the numerical model. The validated numerical model was then used to conduct more numerical simulations to obtain more results such as energy absorption, impact force and vulnerability curve of the SIP against windborne debris impact.
Materials and Design 08/2014; 60:409–423. DOI:10.1016/j.matdes.2014.04.038 · 3.50 Impact Factor
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