Nobuo Masaki

Fundamental study of smart tire system

This study analyzes a system for measuring six force components acting between a tire and the road surface, by determining strains in the wheel-tire module. The measurement method was developed on the basis of the least squares method, and dynamic tests were carried out to demonstrate the effectiveness of the method. It is expected that real-time measurement of the six force components will greatly improve performance and reliability of control systems for vehicle dynamics

Development on Rubber Bearings for Sodium-Cooled Fast Reactor: Part 1 — Examination Plan

This paper describes the past preliminary examination results and the new characteristic examination plans of the thick laminated rubber bearing for the application to Sodium-cooled Fast Reactor (SFR).The preliminary examination focusing on mechanical characteristics such as shear modulus with a 1/8-scale model (ϕ= 200 mm) and creep characteristics with a 1/13-scale model (ϕ= 120 mm) were carried out [1]. With the basic mechanical characteristic examination, the basic design formulas were temporarily confirmed. Furthermore, to establish the creep prediction formula, the creep characteristic examination has been carried out and the creep amount during the plant life has been approximately predicted.To obtain the mechanical properties of thick laminated rubber bearing with the scale-effect, the basic mechanical characteristic examination, including the ultimate behavior test, with the 1/2-scale model (ϕ= 800 mm) will be planned to confirm design margin with clarifying the ultimate limit curve under the bi-axial loading such as shear strain and the normal stress. Moreover, the deterioration promoted examination will be planned. The object of this examination is intended to grasp the degree of aging that may be caused by environmental effects during the plant life. By the accelerated deterioration examination results, the influence by aging on the mechanical characteristic and ultimate behavior of the laminated rubber bearing could be evaluated.Copyright

Development on Rubber Bearings for Sodium-Cooled Fast Reactor: Part 2 — Fundamental Characteristics of Half-Scale Rubber Bearings Based on Static Test

This paper described the results of the static loading tests using a half-scale thick rubber bearing to investigate the fundamental characteristics such as horizontal and vertical restoring force of a rubber bearing applied to a Sodium-cooled-Fast-Reactor (SFR). Since the SFR has thin-walled component structures, a seismic isolation system is employed to mitigate the seismic force. A rubber bearing with thick rubber layers is used for the seismic isolation system applied to the SFR, it was developed aiming for isolation of not only horizontal response acceleration, but also vertical response acceleration. The thick rubber bearing of 1600 mm in diameter full-scale was designed to provide about a 10000 kN rated load with a horizontal natural period of 3.4 s and a vertical one of 0.125 s. Moreover, a linear strain limit of the thick rubber bearing was designed to accept a horizontal displacement of 700 mm or more in order to ensure a double safety margin for response displacements against a design basis ground motion. The static loading tests were performed using a half-scale thick rubber bearing with a diameter of 800 mm to investigate the horizontal/vertical stiffness, damping ratio, a linear strain limit in horizontal direction and a tensile yield stress in the vertical direction. The fundamental characteristic of rubber bearings employed to the SFR and the validity of a design formula became clear through the static loading tests.Copyright

Vehicle Dynamics Management of Electric Vehicle Based on Tire Force Usage (2nd Report, Electric Vehicle Examination of Tire Force Usage Control for In Wheel Motors)

It has been shown in our first report that DYC is not compatible with the tire force usage equalization and it is important to consider total tire force Fx and Fy as feedback signals for DYC being compatible with the tire force usage equalization. Also, the control logic devised then has been found very effective in simulation. In this report, an attempt has been made to clarify whether the control logic as predicted by simulation is effective or not for real vehicle by conducting real electric vehicle run tests. It has been found that the control logic of this study is very effective for the independent wheel-in motor electric vehicle. Also, handling has become neutral steering by using our control logic, and consequently, the vehicle could be neutrally steer up to higher speed than without control.

Restoring Force Characteristics of Laminated Rubber Bearings Under Various Restraining Conditions

We conducted the measurement of restoring force characteristics of laminated rubber bearings under various restraining conditions. In the experiment, we provided three laminated rubber bearings with various second shape factors (S 2 = 3,4,4.94). The restoring force is obtained by using a newly designed combined loading test apparatus. By using this apparatus, the laminated rubber bearing could be subjected to shear, compressive and rotational deformations independently. In this experiment, we defined the degree of restraint as the ratio of the bending moment to the restricting bending moment which was measured when the rotation angle of the laminated rubber bearing was zero radian. This means that the flanges on both sides of the laminated rubber bearings were kept parallel during horizontal deformations. From the experiment, it was confirmed that restoring force characteristics were affected by the degree of restraint. Some reduction in restoring forces was observed when the degree of restraint was small. In particular the laminated rubber bearing with a small second shape factor, namely the rubber bearing, had a slender shape, easily buckling under small horizontal displacement. It was also confirmed that bending stiffness of the laminated rubber bearing had shear strain dependency and vertical load i.e., surface pressure dependency. The results of this experiment reveal that we should consider the reduction of the restoring force if the upper or lower structure of the laminated rubber bearing is not sufficiently rigid.

Vibration Control Performance of Damping Coupled Tuned Mass Dampers

Recently tuned mass dampers have been installed on three-story prefabricated houses for reducing of traffic-induced vibration and improving living comfort. This tuned mass damper consists of a mass unit, spring units and laminated rubber bearings. The mass is supported by four laminated rubber bearings, and spring units are used for adjusting the natural frequency of the tuned mass damper to the optimal value. Vibration control performance of this type of tuned mass dampers is deteriorated when the natural frequency of the house is changed. To solve this problem, the authors have developed a damping coupled tuned mass damper. In this type of tuned mass damper, two mass units having slightly different natural frequencies are coupled by using a damping unit. In this paper, mechanism and vibration control performance of the damping coupled tuned mass damper are described.Copyright

Dynamic Characteristics of a Sliding Bearing Using Lubricant Material for Base Isolation of Light Structures

The authors have been developed a system for base isolation of a wooden house and a prefabricate house. It consists of sliding bearings and laminated rubber bearings. There are two types of sliding bearings, one has the coefficient of friction of 0.046, the other has 0.06. Each of sliding bearings supports 30 ∼ 40kN of vertical load, the surface pressure of the sliding shoe is 10 ∼ 12 N/mm2 (10∼12MPa). The horizontal stiffness of the laminated rubber bearing is 38.5N/mm. For base isolation of an ordinary wooden house, 12 ∼ 16 sliding bearings and 4 ∼ 6 laminated rubber bearings are used. If the mass of a wooden house is 40ton and it is supported by 16 sliding bearings of the coefficient of friction of 0.046 and attached by 4 laminated rubber bearings with the horizontal stiffness of 38.5 N/mm, therefore it has 0.249 of the equivalent damping factor and 3.2 second of the natural period. As for the base isolated houses which are used this system, 500 houses have been constructed in Japan currently by the August of 2002 (Takahashi, 2002). As an advanced system of this base isolation system, we have developed a new type of the base isolation system of sliding bearing using silicone lubrication materials and rubber spring devices.Copyright

Damping Force Characteristics of High-Damping Rubber Damper in Small Shear Strain Regions.

In this study we discuss the applicability of a high-damping rubber damper, which is composed of micro-networks and viscous material, as the damping device in microvibration-isolation devices or tables. For those purposes, damping force characteristcs of the high-damping rubber damper were measured using a new measuring device. We could estimate damping force characteristics to a shear displacement amplitude of 2.5×10-6m, and this high-damping rubber damper was found to have energy-absorption capacity in the regions of very small shear displacement amplitude. Also, the damping force characteristics of a viscous shear damper using silicone oil, which is the most popular damper for vibration-isolation devices, were measured. On comparing the damping force characteristics, our high damping rubber damper was found to have a larger energy absorption ability than the viscous shear damper. Furthermore, the rubber dampers were installed to the vibration isolation table which can mainly isolate microvibrations in horizontal direction. Through microvibrationisolation tests it was confirmed that this high damping rubber could be applied to microvibrationisolation devices.