In recent years, there has been increasing research in several industrial fields for development of semi-active vibration control devices. In particular, devices using magneto-rheological (MR) fluid have been attracting great research interest because they can realize high performance as capacity-variable dampers. MR fluids are controllable fluids that respond to applied magnetic fields. Applied magnetic fields drastically change the viscosity of MR fluids from an oily state to a semi-solid state. This paper describes a study on a large capacity device using an MR fluid, i.e., an MR damper. This developed MR damper provides a maximum damping force of 300 kN. Various tests were carried out and the dynamic characteristics, force-displacement hysteresis loops and controllable forces were investigated. These tests verified that the MR damper provides a technology that enables effective semi-active control of large-scale structure systems, i.e., real buildings and civil engineering structures.
Magneto-rheological fluid dampers (MR dampers) have recently been designed to control the response of civil engineering and building structures because of their large force capacity and controllable force characteristics. To enable them to control structural responses, the dynamic characteristics of structures need to be clarified. This paper discusses the design of MR dampers with a bypass orifice mechanism and verifies their performance by means of dynamic tests and dynamic analytical models. Their dynamic characteristics are investigated experimentally to compare the performance of two different magneto-rheological fluids. One is developed by the Lord Corporation and the other is newly developed in Japan. The effectiveness and validity
We propose a quick and controlled cracking method for industrial ceramic waste by applying a steam pressure cracking (SPC) agent. The agent is a non-explosive and low-vibration-type chemical, which was developed by one of the authors of this study. We prepared a concrete specimen that had a diameter and cylinder height of 150 mm. Several grams of the agent cracked the specimen. We could control the cracking better in water than air when the air and water conditions were compared. When tested in water, the agent was placed in the hole of the concrete specimen and ignited, and the specimen could be split into two or three pieces of the same size. However, using another SPC agent that was explosive, the concrete specimen was broken into small fragments and size of the concrete pieces could not be controlled. The crushing mechanism was different for the two cases. The explosive crushed the concrete mainly through elastic shock waves. However, the steam pressure cracking agent breaks the specimen using the steam pressure and shock waves. We demonstrated that the cracking can also be controlled using guide holes. This steam pressure method can be applied to industrial waste as a safe and well-controlled method.
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