Masanori Shintani

Development of Evaluation Method of Vibrational Stress in Piping System Applying Multiple Laser Displacement Sensors

Many damages of the piping system in the nuclear power plants have occurred due to the vibration fatigue induced by the mechanical vibration of pumps and so on. One of the preventive measures for the problem of vibration is the evaluation of vibrational stress, which is the methods using the strain gauge and the accelerometer. However, these evaluation methods require highly specialized skills and many man-hours, and nuclear plants are awaiting the development of vibration-measuring techniques and evaluation techniques that are easy to perform and produce accurate results promptly. The purpose of this study is the development of the method and the device measuring the vibrational stress directory using the laser displacement sensor. The proposed method evaluates the vibrational stress as follows: Three laser displacement sensors measure the displacement of the piping induced by vibrating, and the strain of the piping is calculated from the difference among the sensor-measured displacements to determine vibrational stress. The measurement equipment isn’t direct contact with the piping evaluated, can be easily reduced in size, and can realize quick and accurate measurement. This paper describes the concept of the proposed evaluation method of vibrational stress in the piping system using three laser displacement sensors, along with its theory and measurement procedure. And then, refer to the proposal of the evaluation method of torsional vibration using six laser displacement sensors. This paper also compares the stress values calculated based on the cantilever vibration identified by this method and the stress values calculated based on material mechanics, and discusses the applicability of the method in actual plants.Copyright

Experimental Study of Evaluation Method of Vibrational Stress in Piping System Applying Multiple Laser Displacement Sensors

In the pipe line installed in the nuclear power plant, there are many reports of damage caused by fatigue as a result of machine vibration of a pump etc. Vibrational stress evaluation by the method using the strain-gauge method or the accelerometer as one of the preventive measures of these oscillating troubles etc. is performed. However, since many special skill and working hours are required for these methods, the development of vibration measurement and stress evaluation technology which operates quickly and easily at the spot is desired. The purpose of this research is the development of a technique and equipment which measures vibrational stress immediately using a laser displacement sensor. In the measurement technique proposed, displacement by the bending vibration of piping which vibrates using three sets of laser displacement sensors is measured, and vibrational stress is obtained by calculating the strain produced from those displacement differences for piping. This measuring instrument is a non-contact system, and a miniaturization and short-time measurement of equipment are easy. This paper deals with the concept of the vibrational stress measurement technique, the theory of the measuring method, and the procedure, the authors propose, using three sets of the laser displacement sensors. Furthermore, using a cantilever model, vibration experiments are conducted, displacements and strain are measured. Next, comparison with the stress by using the displacement measured by the experiment based on this technique and the stress from the strain measured by the experiment is performed. The application possibility of the technique is described.Copyright

Study on Reducing Relative Displacement of Isolation Device With Friction Surface of Inclination

This paper deals with an isolation device by using friction force. An isolation device decreases response acceleration and external force. Therefore, earthquake damage is reduced. However, an isolation device has a demerit for large relative displacement. The purpose of this research is to decrease the relative displacement by using the friction force. Then, an analytical model in consideration of the friction force is proposed, and a simulation is analyzed with well-known earthquake waves. Consequently, it is thought that optimal friction force exists, and this force decreases both the response acceleration and the relative displacement. This is considered to change with the properties of earthquake waves. Then, it analyzed using the regular random wave. The result, the proportional relation was seen between relative displacement and the optimal coefficient of friction. Then, by changing a friction coefficient according to relative displacement, it is thought that both response acceleration and relative displacement can be reduced. However, it is difficult to change a friction coefficient. So, in this research, reduction of response acceleration and relative displacement is aimed by changing the angle of a friction surface and friction force. Furthermore, an angle is changed in the middle of a slope. It is thought that it becomes possible to reduce response acceleration and relative displacement further. An experimental device is made under the same conditions as the proposed analytical model. The experimental results are compared with the analytical results.Copyright

Study on Isolation Device by Friction

When an isolation device is exposed to earthquakes, the relative displacement between the device and the ground increases. The purpose of this research is to decrease the relative displacement by using the friction force. An analytical model in consideration of the friction force is proposed, and simulation analysis under the famous earthquake waves is performed. Consequently, as the friction force increases, the results show that the relative displacement decreases. However, it is found that the response acceleration increases. It is thought that optimal friction force exists, and this force decreases both the response acceleration and the relative displacement. This is considered to change with the properties of earthquake waves. It is shown that the relation between the optimal friction force and the maximum input acceleration is approximately linear from the results of many seismic waves. It is thought that the response acceleration and the relative displacement can be decreased changing the friction force to the most suitable value for each earthquake according to this relation. This isolation device is examined with simulation analysis.

Construction of the Health Monitoring System of a Machine Structure

When big power like an earthquake acts at the place that the machine is normally operating, abnormalities may occur to a machine. If the machine is operated without finding abnormally, danger may attain to mechanical fatal damage and a mechanical work pursuer. Therefore, detecting in the situation where mechanical abnormalities are operated is very important as a health monitoring system. In this research, the system that takes in the vibration wave on the rotation part of the machine currently rotated is constructed. A vibration wave is analyzed using time-frequency analysis (STFT, the Wigner distribution, wave let analysis) From the result, the system by which normal vibration and abnormal vibration are evaluated is constructed from random noise. As a result of comparing normal vibration with abnormal vibration, the peak may have occurred in the high frequency region. It turned out that the analysis result of an unsteady state has a peak 2000Hz–3000Hz of frequency domains, and 4000Hz–5000Hz also in STFT and Wigner distribution. I think that this becomes the important tool which distinguishes the stationary state and unsteady state in health monitoring.© 2009 ASME

Study on Two-Dimensions Base-Isolating Device for Reduction of Displacement by Using Friction Force

This paper deals with research of new isolation device with reduction of horizontal relative displacement by using friction force and reduction of vertical response acceleration and relative displacement by using spring and friction force. The isolation device is using a friction surface. The friction surface is subjected to acts on the slope plate. The restoring-force of horizontal direction is given to the isolation device from elastic force of a compression spring attached to the base. The restoring-force always works in the direction of the center. Therefore, the frictional force and the restoring-force are both proportional to the displacement. The restoring-force of the vertical direction is given to the isolation device from compression springs and draft springs. Simulation analysis was performed under various conditions using this analysis model. Condition reducing both response acceleration and displacement effectively is calculated on various conditions using the analysis model. Furthermore, an experiment is conducted using the experimental device. The experiment is conducted by an imagination wave. Analysis is also conducted on the same conditions. The results of the experiment are compared with the results of the analysis. The performance of the isolation device is examined. The validity of an analysis model is examined. As a result of conducting the analysis and an experiment with this model, it was shown that response acceleration and relative displacement can be reduced successfully. The validity of an analysis model is shown. Next, it analyzes by actual seismic waves. The performance of isolation equipment in actual seismic waves is examined and shown.Copyright

Intensity Analysis and Damage Experiment of a Universal Joint

This paper discusses research on the intensity analysis and damage experiments of a universal joint. The Kashiwazaki Kariwa nuclear power plant suffered damage from the Niigata Chuetsu offing earthquake which occurred on July 16, 2007. The earthquake motion damaged a driving shaft coupling of an overhead traveling crane of the No. 6 nuclear reactor building. The damaged portion consisted of the universal joint. The target of this research focuses on the universal joint and the cause of its damage from the earthquake, as well as the design of proposed measures. As a cause of the damage it is thought that the universal joint was loaded from the torque of the earthquake motion. The torque that loaded to the universal joint is calculated from the earthquake motion. The stress that loaded to the universal joint is calculated by an analysis by 3DCAD (Three Dimensional Computer Aided Design) and CAE (Computer Aided Engineering). In the experiment, a miniature model of the universal joint is loaded with the torque and damaged. Similarly, in the analysis by 3DCAD and CAE, the miniature model is loaded with the torque and damaged. The experimental result is compared with the analysis result and the validity of the analysis is examined. The proposed measures to improve the design of the universal joint to form earthquake loads are examined by 3DCAD and CAE.Copyright

Study on Isolation Device for Decrease of Displacement by Using Control of Friction

This paper deals with reduction of horizontal relative displacement by using a frictional force for a seismic isolator. First, a compression spring is attached to the base. Next, a slope plate is superimposed on it. The frictional force acts on the slope plate. The restoring-force is given to the seismic isolator by the compression spring attached to the base. In the equation of motion of the analytical model, the frictional force changes in proportion to the displacement. The restoring-force is also proportional to the displacement. The restoring-force always works in the direction of the center. Therefore, the frictional force and the restoring-force are both proportional to the displacement. Simulation analysis was performed under various conditions using this analysis model. As a result of conducting the analysis and an experiment with this model, it was shown that response acceleration and relative displacement can be reduced successfully. In order to reduce response acceleration and relative displacement more, analysis was carried out with the actual earthquake waves under the conditions to change the coefficient of friction by relative displacement. As a result, the coefficient of friction that reduces relative displacement most effectively without impairing the performance of the seismic isolator was established. However, the coefficient of friction that reduces the response acceleration and relative displacement effectively depends on by seismic waves. Therefore, in this report, the coefficient of friction that reduces response acceleration and relative displacement most effectively is determined by using white noise. It is analyzed with actual seismic waves by using the decided parameters. The performance of the seismic isolator is examined.Copyright

Vibration Characteristic Evaluation of Nonlinear Vibration Systems With Gaps Considering Energy Dissipation by Collision

This paper deals with nonlinear vibration of a continuum system with gaps under random waves considered collision phenomena. In order to investigate this nonlinear vibration characteristic, experiments are made with an experimental apparatus consisting of a nonlinear vibration system. A 2.3mm thick plate is used for the collision phenomena experiments. Moreover, an analytical model of the cubic equation is proposed based on the restoring force characteristics in the experiments. This analytical model is used for the simulation analysis, and the results are compared with the experimental results. However, the R oot- M ean- S quare (R.M.S.) values of the response acceleration of the analytical results are larger than R.M.S. values of the response acceleration of the experimental result. The difference of these results indicates that energy is dissipated in the collision phenomena. Then, the coefficient of restitution by the collision phenomenon between mass and plate is measured from the experiments. In the analysis, the dissipation energy is replaced with an equivalent damping ratio. The simulations are calculated by using this modified analysis. Consequently, the simulation results agree well with the experimental results.Copyright

Evaluation of Energy Absorption in Nonlinear Vibration System With Gaps

This paper deals with nonlinear vibration characteristics of a continuum system with collision phenomena under random waves with gaps. In order to investigate such a nonlinear vibration characteristic, an experimental apparatus consisting of a nonlinear vibration system was made. Moreover, we propose an analytical model based on the restoring force characteristics of the experiments. In this report, the size of the gap between a mass and a plate is set to 0.5mm or 1.0mm. For this experimental model we also propose an analytical model. We use plates of 1.6mm thickness in the collisions both in the experiment and the analysis. The analytical model is based on an elasto-plasticity solid model. When considering the coefficients of restitution or energy absorption, the experimental results nearly agree with the analytical results [10]. We found that the rate of a collision changes with the size of the gap at each input acceleration level. As the gap size widens, energy absorption decreases for each input acceleration level. Consequently, in order to increase the energy absorption, it becomes necessary to increase the rate of the collision.Copyright