【作者】 周稳；

【导师】 吴桂英；

【作者基本信息】 太原理工大学 ， 固体力学， 2010， 硕士

【摘要】 随着科学技术的发展,爆炸在国防工业、国民经济建设中应用愈来愈广泛,近年来,各类建筑结构与工业产品在爆炸载荷作用下动力响应已经越来越受到人们的重视,结构的动态响应也是固体力学领域内一个重要的内容。结构的反直观现象是一种特殊的动力响应,即结构受瞬时强动载荷作用时,其最终的变形与载荷作用方向相反。自从20世纪80年代著名学者P. S. Symonds等在研究冲击载荷作用下两端铰支梁的动力响应时发现了反直观现象后,愈来愈多的科技人员给予了关注并进行了相关的研究,在脉冲载荷,弹体冲击,爆炸载荷等方式作用下结构都可能出现反直观现象,这在数值模拟与实验中都得到了证实。在相关研究中,人们很少考虑炸药形状对爆炸冲击波的影响,球壳在爆炸载荷下反直观响应也是研究甚少。本文首先对结构反直观行为与近年来关于爆炸方面的模拟情况进行了综述,描述了爆炸过程中的物理化学现象,介绍了任意拉格朗日与欧拉(ALE)算法特点。运用数值模拟的方法做了以下工作:1、对比了爆炸冲击波超压峰值的几个经验公式,在比距离Z较大时,数值模拟与经验公式比较符合。对几种形状炸药在空气中起爆后爆炸冲击波传播进行了数值模拟,对比了几种形状炸药起爆后传播特性以及在两个垂直方向超压峰值,炸药起爆后在较大表面的法线方向具有较大的冲量且传播速度较快。2、研究了相同质量的几种形状炸药起爆后对球壳的动力响应,得到了各种形状炸药起爆后产生的超压峰值与冲量,同等质量的炸药,长方体炸药产生的产生冲量与超压峰值最大,球体炸药产生的最小,这与文献给出实验结果是一致的。3、运用ALE流固耦合方法对炸药起爆后球壳动力响应进行了数值模拟,得到了球壳在爆炸载荷下产生反直观现象的爆心距区域。数值模拟结果表明,球壳的矢高与壳厚对反直观影响较大。给出了炸药起爆后爆轰产物的扩散示意图,研究了空气中的超压分布。对比了球壳附近某些点的压力时程曲线,球壳前方区域会出现两次峰值,可以得到球壳对爆炸冲击波有反射作用。本文最后分别从动态内力耦合,塑性变形,能量转换等方面说明了产生反直观现象的特点,阐释了球壳产生反直观现象的机理。更多还原

【Abstract】 As science and technology develop,explosions are used more and more widely in national defense industry and economy. In recent years, dynamic responses of building structural and industrial products under blast loading have got more attention. Structural dynamic response is also one of important sides of solid mechanics. Counter-intuitive dynamic response is a special dynamic response, that is, structural final deformation is opposite to the direction of loading when under short-term impulsive loading.Since 1980s, P.S. Symonds and other scientists found the counter-intuitive response of beam when they studied dynamic response of beam supported by both hinged ends. More and more scientists pay close attention to the research. The structural counter-intuitive may occur under implusive loading (blast loading), projectiles (bullets shock) or explosive loading (pulse loading). And this has been confirmed in numerical simulation and experiments. But in related studies researchers rarely consider the influence of the shape of explosive on shock wave and pay little attention to the counter-intuitive response of spherical shells under explosive loading.In this paper, the structural counter-intuitive behaviour and simulations of blast shock in recent years are reviewed. Physical and chemical phenomena in the process of explosion are described. Then some theories of the finite element method and the ALE algorithm are introduced. At the same time, the following work is done with numerical simulation method:1、Comparing the peak blast overpressure of several empirical formula, It is considered that when the distance is larger than distance Z, the results of numerical simulation are more in line with empirical formula.The blast wave propagation is researched with numerical simulation after the detonation of explosives with different shapes in the air. The detonation propagation characteristics and two vertical peak overpressures are compared among several forms of explosives. After detonation explosives have larger impulse on larger surface in normal direction and spread faster.2、The dynamic response of forms of explosives with the same quality to spherical shell are studied. The peak overpressure and impulse are reached. To the same quality explosive, rectangular explosives produce the largest impulse and overpressure, but ball explosives produce the smallest impulse and overpressure, this document presents the experiment results are consistent. 3、ALE arithmetic are used for numerical simulation on dynamic response of spherical shell after detation of explosives. And the blasting distance area of spherical shell, which is under explosive load and produces counter-intuitive phenomenon, is obtained. Results of numerical simulation show that the height and thickness of spherical shell have greater influence on counter-intuitive phenomenon. Meanwhile, the diagram of proliferation of detonation products is gained, and the distribution of air overpressure is researched. Then, comparisions are done among pressure-time curves of some points near spherical shell. There are two peaks in front region of spherical shell. It is reached that spherical shell has reflection on shock wave.Finally, the phenomenon of counter-intuitive is explained individually from the perspectives of dynamic coupling, plastic deformation, energy transformation, etc. The mechanism interpreting the reasons for the phenomenon of shell counter-intuitive is also presented.更多还原