【作者】 谢青海；

【导师】 王志华； 赵隆茂；

【作者基本信息】 太原理工大学 ， 固体力学， 2012， 硕士

【摘要】 泡沫金属夹芯结构由上下两层金属面板和超轻泡沫金属芯层粘合而成。由于其独特的多功能复合特性(如高比刚度、比强度,隔音及保温隔热,阻尼减震,优越的抗冲击性能等),使其具有广泛的应用前景,例如可以设计出兼具高强度和良好能量吸收性能的超轻结构。因此,近年来泡沫金属夹芯结构广泛应用于航空航天飞行器、高速轨道车辆、汽车、舰船等高科技领域。本文主要研究冲击和准静态载荷下夹芯浅拱的变形/失效模式,能量耗散机制及结构响应。实验用夹芯拱由铝合金面板和泡沫铝芯层构成。实验研究了泡沫铝子弹冲击载荷作用下固支夹芯拱的动态响应。使用激光位移传感器记录了夹芯拱后面中心的位移历史,并用后面板永久位移和芯层压缩应变来衡量夹芯拱的抗冲击能力。首先,对夹芯拱的变形和失效模式进行了系统的分类和分析；其次,详细分析了冲击载荷作用下夹芯拱的结构响应和变形机理；最后,深入研究了子弹冲量、面板厚度、芯层厚度和曲率半径对其抗冲击性能的影响。使用LS-DYNA有限元软件对夹芯拱的动力响应进行了数值模拟计算。通过比较变形模态、位移历史、永久位移和芯层压缩应变的计算结果与实验结果,验证了有限元模型的合理性和可靠性,并进一步对有限元计算结果进行了详细的分析与讨论。研究结果表明：可以通过增加面板厚度、芯层厚度和适当调整曲率有效控制后面板的永久位移,提高夹芯拱的抗冲击能力。一个近似的质量最优化研究被提出,优化设计通过无量纲参数来确定。通过研究泡沫子弹作用于结构上的压力时程曲线和冲量,验证了使用泡沫铝子弹冲击加载是一种实验室环境研究结构抗冲击动态响应的安全、有效方法。通过实验和理论两方面研究了准静态载荷下夹芯拱的结构响应和塑性坍塌模式。实验结果显示,在准静态载荷下夹芯拱主要通过面板屈服、芯层剪切和压入失效三种模式发生塑性坍塌,并且对塑形坍塌机理进行了分析。建立了简化的理论分析模型,得到了夹芯拱弹性刚度和初始坍塌强度的分析方程,并且与实验结果有很好的吻合。更多还原

【Abstract】 Metal foam sandwich structures, obtained by combining metal face sheets with a lightweight metal foam core, have peculiar properties (low specific weight, efficient capacity of energy dissipation, high impact strength, acoustic and thermal insulation, high damping, etc.), that made them interesting for a number of practical applications, such as the realization of lightweight structures with high mechanical strength and good capacity of energy dissipation under impacts. Therefore, they have been applied to many fields, for example, aerospace aircrafts, high-speed rail vehicles, automotive, ships and so on.In this paper, the structural response of clamped shallow sandwich arches with aluminum foam cores subjected to impact and quasi-static loading have been measured. The shallow sandwich arches comprise2A12-0aluminum alloy face sheets and aluminum foam cores.The dynamic response of end-clamped shallow sandwich arches has been measured by impacting the arches at mid-span with aluminum foam projectiles. Laser displacement transducer was used to measure the permanent transverse deflection of the back face mid-point of the arches. The resistance to impact loading is quantified by the permanent back face deflection and final core compressive strain at the mid-span of the arches. First, the deformation/failure modes of shallow sandwich arch were observed and classified systematically. Further, the structural response and deformation mechanism of clamped shallow sandwich arches subjected to projectile impact were analyzed. Finally, the effects of projectile impulse, face-sheet thickness, core thickness, and radius of curvature on the structural response were obtained.Based on the experiments, corresponding finite element simulations were conducted using LS-DYNA software, and the simulation results are reported and discussed in this paper. Finite element simulations of these experiments are in good agreement with the experimental measurements. The results indicated that permanent deflection of the back face can be efficiently controlled by increasing thickness of face sheets, thickness of core or appropriately increasing curvature. Meanwhile, shock resistance of the shallow sandwich arch can also be improved. A limited study of weight optimization is carried out. Dimensionless parameters governing optimal designs are identified. Specific results are presented for the best performance that can be achieved and the optimal distribution of thickness between face sheet and core. The numerical simulations were employed to determine the pressure versus time history exerted by the foam projectiles on the arches. It was found that the pressure transient was reasonably independent of the dynamic impedance of the arch, suggesting that the metal foam projectile is a convenient experimental tool for ranking the shock resistance of structures.The structural response and plastic collapse modes for clamped sandwich arches under quasi-static loading have been investigated experimentally and theoretically. The experimental results showed that plastic collapse displayed in three competing mechanisms:face yield, core shear and indentation. Simplified theoretical models and analytical formulae are developed for the elastic stiffness and initial collapse strength of sandwich arches.更多还原