利用LS-DYNA有限元软件模拟弹体撞击作用下平纹织物的动态过程,分析织物断裂前的变形特性以及能量吸收特性,讨论边界约束条件和弹体形状对织物动态响应的影响.结果表明:纱线应变能和纱线动能是弹体动能转变的最主要形式,在给定计算的时间内,对于四边无约束、对边同定约束和四边固定约束3种边界条件,不论弹头形状采用平头、半球头和卵形头中的哪一种,两者之和占弹体动能损失量的比例不小于74.6%.模拟结果还表明.边界约束条件和弹体形状对织物的变形、应力分布以及能量吸收特性均有明显影响.边界条件不同,纱线动能和纱线应变能占弹体动能损失量的比例会发生较大变化,织物的能量吸收特性也不同.弹体头部形状不同,受撞击区影响的纱线数目也不同,弹头越钝,织物中抽拔出的纱线数目越多.从织物结构的抗弹性能角度看,织物结构抗钝头弹体的穿透能力要优于尖头弹体.
A commercially available finite element analysis code, LS-DYNA, is used to model the dynamic responses of a patch of plain-woven fabric under ballistic impact of projectile. The fabric deformation and time history of energy absorption mechanism before yams rupture were investigated by numerical simulation method, and effects on the fabric dynamic responses by boundary conditions and projectile shapes were also discussed. The simulation results showed that the yarn strain energy and the yarn kinetic energy were the dominant energy transfer of kinetic energy of projectile. At a given time, for the three boundary conditions with four edges free, two edges clamped and four edges clamped, the sum of yarn strain energy and kinetic energy accounted not less than 74.6% for different shaped projectile with flat, hemispherical or ogival nose. Simulation results also indicated that the boundary conditions and projectile shapes significantly affected the fabric deformation, stress distribution and time history of energy absorption mechanism. The yam strain energy and the yam kinetic energy changed the proportion in loss of projectile kinetic energy due to the different boundary conditions. The nose shape of projectile had an effect on the number of yams that was involving in the impact region. For the bulletproof performance of plain-woven fabric, the blunt nosed projectile was more difficult to perforate the fabric architecture than sharp nosed one.
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