Viscous Damping Factor Research Articles

Compensation of Transfer Deviation on Symmetry Type Bilateral Servo Mechanism

There are two types of bilateral servo mechanisms utilized in force reaction type manipulators. The simple symmetry type has the larger transfer deviation. The force feedback type with the smaller transfer deviation requires troublesome force sensing devices. This paper describes a simple compensation method of transfer deviation on the symmetry-type. We found that transfer deviation of the torque decreases by means of subtracting tachometer generator output through a PD circuit from the driving input of the opposite motor. The system is unstable when the gain constants in compensation circuits are over the limits, which are determined as equivalent mechanical inertia moment and viscous damping factor. The transfer deviation of the compensated symmetry type system is near to that of the force feedback system.

対称形バイラテラルサーボ機構における伝達誤差の補償

We have two types of the bilateral servo mechanisms utilized to force reaction type manipulater. The simple symmetry type has the larger transfer deviation. The force feedback type with the smaller transfer deviation needs troublesome force sensing devices. This paper describes the simple compensation method of transfer deviation on the symmetry-type. We found that the transfer deviation of the torque decreases by means of subtracting output of tachometer generator through PD circuit from the driving input of the opposite motor. The system is unstable when the gain constants in compensation circuits are over the limits, which are decided to equivalent mechanical inertia moment and viscous damping factor. The transfer deviation of the compensated symmetry type system is near to that of the force feedback system.

Damping characteristics of golfing equipment

The dynamic properties of golf shafts and golf balls were measured. This includes natural frequencies and damping factors. Both steady‐state and transient procedures were used in the test evaluations. Different types of golf shafts were used, including different steel alloys, aluminum, and graphite. Damping values are reported for the entire golf shaft portion, with and without the clubhead. Damping is also reported for smaller sections of the golf shaft by cutting the shaft into three parts and measuring each part. This was done to examine the influence of the manufacturing process since the small diameter end is processed differently from the large diameter end. Golf‐ball measurements were made of a coefficient of restitution which is converted to an equivalent viscous damping factor. This value is reported for different impact velocities and for different types of manufactured balls. This includes the solid ball with and without a covering layer as well as the core wound ball. The significance of the golf shaft and golf‐ball properties is discussed in the light of the entire golf swing and ball impact process. The aim is to assess the possibility of designing and manufacturing a better double impedance match between the initiation of the swing through the final stages of impact with the ball.

Comparative forced vibration test of two BWR-type reactor buildings

The basis of this paper is comparative forced vibration testing of two GE 460 MW(e) BWR-type reactor buildings. The tested nuclear power plants are the Fukushima Nuclear Power Plant Unit No. 1 of the Tokyo Electric Power Company (hereinafter referred to as Fukushima) and the Shimane Nuclear Power Plant of the Chugoku Electric Power Company (Shimane). They are almost the same in both structure and function, but are built on rock of quite different rigidity. The shear wave velocity of Shimane is about three times that of Fukushima. The forced vibration tests were performed immediately after completion of each reactor building using a vibrator with a maximum exciting force of 3 t. The computer simulation analyses were carried out using vibration models possessing different internal viscous damping factors for each structural element. Both the resonance periods and damping factors of Fukushima were found to be larger than those of Shimane. Thus, site selection of nuclear power plants must be reviewed as a matter of utmost importance from the viewpoint of seismic design.

Vibration and soil-structure interaction tests of a nine-story reinforced concrete building

abstract The Millikan Library Building, a nine-story reinforced concrete shear-wall structure at the California Institute of Technology, was tested dynamically by means of two eccentric mass vibration generators located on the ninth floor. The response levels ranged up to a maximum acceleration of 0:02 g. The natural periods of vibration, the mode shapes and the energy dissipation were measured for the first and second E-W translational modes, the N-S fundamental mode and the first torsional mode. Soil-structure interaction was investigated by measuring foundation motion and nearby soil surface movements during resonent vibrations in the N-S and E-W fundamental modes. Other tests included “man-excited” vibrations at low stress levels and a measurement of resonance of an air handling unit on the roof, which was found to magnify the roof response by a factor of 8.5. The measured fundamental periods were short compared to typical framed structures of this height, 0.50 sec in the N-S direction, 0.66 in the E-W direction and 0.46 in torsion. These values increased roughly 3 per cent over the range of testing. The energy dissipation as measured by a viscous damping factor, varied between 0.70 and 2.00 per cent of critical. This large variation over the testing range indicates that tests at higher stresses are needed to determine the energy dissipation expected during the response to strong earthquake motions. The soil-structure interaction measurements showed that the building responded very nearly as if fixed at the foundation; rocking contributed less than 1 per cent to the total roof motions of the structure and foundation translation about 2 per cent. Although negligible as far as the building motion is concerned, the results demonstrate the possibility of performing full-scale soil-structure interaction experiments.

Force-Deflection Relations From Dynamic Tests

A method is developed for determining the dynamic force-deflection relation of a one-degree of freedom hysteretic structure from the steady-state response to sinusoidal excitation. The data needed are the resonant frequency and the equivalent viscous damping factor, as defined in the paper, as functions of the amplitude of steady-state response. The method is applicable to oscillators of the Masing type, a classification which includes the more common models of yielding behavior (e.g., elasto-plastic, bilinear hysteretic). Examples of the application of the method to mathematical models of hysteretic structures and to dynamic test data are given.

Periodic Response of a General Yielding Structure

A general nonlinear hysteretic force-deflection relation for a one degree-of-freedom structure is presented. The relation is a continuous, smooth function and describes yielding behavior varying between the limits of the linear and elasto-plastic cases. The steady-state response to sinusoidal excitation of a structure having these properties is investigated, and the resonant amplitude and frequency response curves are obtained. A typical family of these curves is verified by numerical integration of the equation of motion. The equivalent viscous damping factor for the general structure is determined. It is concluded that the relation is sufficiently general to be useful as a model for dynamic behavior of yielding structures. Comparison of dynamic test results to the analytical results can furnish approximations to the dynamic force-deflection relations of many real structures.