船桥碰撞过程引发的冲击动力学论题

对船桥撞击过程引发的几个冲击动力学论题进行了分析。研究表明:1为降低船撞力,应采用柔性(低的结构动态广义波阻抗)防撞装置;2撞击力所做的功,通过应力波传播转化为内能(变形能)与动能之和;而变形能中的不可逆部分愈高,防撞装置发挥的整体作用愈大,则愈有利于防撞装置发挥缓冲耗能作用。并且如何让船舶尽早结束撞击并带走尽量多的剩余动能,应是防撞装置设计的关键点;3黏性耗能可缓冲撞击过程、延长撞击历时,有利于防撞装置发挥整体作用,进而为船舶在低应力下转向滑离、从而带走尽可能多的剩余动能创造条件。因此,船撞桥防护装置的设计应该建立在如下的科学设计理念上:ⅰ低波阻抗意义上的冲击柔性,ⅱ缓冲撞击过程意义上的粘性耗能,ⅲ防撞装置能及早发挥整体作用,化撞击集中力为分布载荷,以及ⅳ让船尽早滑离而带走尽量多的剩余动能。以钢丝绳防撞圈为主要元件的柔性耗能防撞装置是这一防撞理念的工程应用实例,其有效性已为工程实践和实船撞击试验证实。

Impact dynamics topics motivated by ship-bridge collision process

Some impact dynamics topics motivated by the ship-bridge collision process are analyzed in this paper. It is shown that (1) in order to reduce the impact force a flexible (i.e. with low structural dynamic generalized wave impedance) crashworthy device should be applied. (2) The work done by the impact force is transformed via wave propagation into the internal energy (deformation energy) and kinetic energy. The larger the irreversible part of the former is, as well as the greater the overall role played by the crashworthy device is, the better the buffer role played by the crashworthy device will be. Moreover, how to make the ship as soon as possible to end the collision and carry away as much as possible the remaining kinetic energy should be a key point. (3) Viscous dissipation of energy can buffer the collision process, prolong the dissipation duration, and help the crashworthy device to play an overall role, and create the condition for turning ship away to end the collision. Thus the scientific design idea of crashworthy device should be based on (i) impact flexibility in terms of low structural wave impedance, (ii) viscous dissipation in terms of damping collision process, (iii) let the crashworthy device plays an integral role as soon as possible so that the intense impact concentrated force could be changed into a weaker distributed load, and (iv) let ship turns away as soon as possible, and thus takes away the remaining kinetic energy as much as possible. As an engineering application example, such design idea is reflected in the new flexible crashworthy device consisting of hundreds of steel-wire-rope coils. Its validity has been confirmed by the engineering practice and the real ship collision tests.