Study on Seismic Behavior of Mechanical Snubbers

机械缓冲器是一种用于高温、放射性等特殊环境下管道系统的防震装置，由滚珠丝杠、飞轮、刹车盘和刹车蹄组成。它在缓慢运动(如管道的热膨胀)时没有任何阻力地移动，并抑制由快速运动(如地震)引起的位移。为了从理论上分析机械式缓冲器的阻力特性，建立了机械式缓冲器的运动方程，并利用连续系统仿真语言(CSSL语言)对其阻力特性进行了仿真。对缓冲器的各种物理性能进行了大范围的数字仿真。用CSSL语言模拟了减振器支承管道(简支梁)的地震反应。讨论了减振器在地震作用下的约束效果和最大抗力，并与油压减振器的情况进行了比较，利用自行研制的振动试验机对市场上的减振器的抗力特性进行了测试。对由滚珠丝杠、飞轮和垂直振动调速器组成的新型机械阻尼器的隔振效果进行了理论和实验研究。该阻尼器对较大的飞轮转动惯量J起到了减振器的作用，对较小的转动惯量J起到了总的减振作用。

The mechanical snubber is an earthquakeproof device for piping systems under particular circumstances such as high temperature and radioactivity, and consists of a ball screw, a flywheel, a brake disk and brake shoe. It moves without any resitance in response to a slow movement such as thermal expansion of pipings and restrains displacement caused by a rapid movement such as earthquake. It has nonlinearities in both load and frequency response, so it will be very difficult to analyze the resisting force characteristics of the mechanical snubber theoretically.In this research, the equation of motion of the mechanical snubber was derived and the resisting force characteristics of the snubber were simulated using Continuous System Simulation Language (CSSL). The digital simulations were carried out for various kinds of physical properties of the snubber and over a wide range. The earthquake responses of piping (a simply supported beam) which is supported by the snubber were also simulated using CSSL. The restraint effect and the maximum resisting force of the snubber during earthquake were discussed and compared with the case of an oil damper.The resisting force characteristics of a snubber available in the market were measured using the vibration testing machine built as trial. The experimental results agreed fairly well with the results of the digital simulations, so that the validity of the digital simulations were substantiated.Moreover, the effects of vibration isolation of a new type of mechanical damer which is composed of a ball screw, a flywheel and a vertically oscillating governor were discussed theoretically and experimentally. This damper acts as a snubber for larger values of the moment of inertia J of the flywheel and acts as general absorber for smaller values of J.