Nobuo Oshima

Tuned sloshing damper using electro-rheological fluid

A tuned sloshing damper (TSD) utilizing an electro-rheological (ER) fluid as a sloshing liquid (ER-TSD) is proposed. The sloshing frequency of the TSD depends on the sloshing stroke length of the liquid contained in the tank. In this paper, the ER-TSD is used in the form of a rectangular tank with electrodes. The ER-TSD sloshing frequency can be controlled by applying an electric field to the ER fluid. We have studied the vibrations of a structure which had two natural frequencies. The forced and free vibration tests were carried out with and without the ER-TSD. By controlling the electric field, the ER-TSD can suppress the vibrations of the structure even when the natural frequency of the structure changes. The free vibration responses of the structure with the ER-TSD were analytically obtained by using a tuned mass damper model based on the Housner theory. The simulated results appeared to be in reasonable agreement with experiments.

Report on a simultaneous ion viscosity, strain and impedance measurement technique using a novel integrated dielectric, optical fiber and piezoelectric sensing element for the online characterization of smart structures

This paper reports on a simultaneous ion viscosity, strain and impedance (SISI) system in order to measure the physical and chemical properties of composites during their curing process. The SISI system uses an integrated multi-sensing element, entitled DOP, that is comprised of dielectric (D), optical fiber (O) and piezoelectric (P) sensors. This system was used to measure several data simultaneously in real time and in situ. The results clearly show that there is a direct relationship between the ion viscosity, impedance and strain changes during the curing process. It was found that dielectric sensor is very sensitive to physical and chemical changes of the composite both in the heating and cross-linking periods. The piezoelectric proved to be a useful element during the heating period with a very sensitive and surprising behavior during the cooling period. The optical fiber also demonstrated a very striking profile in strain variations during cooling.

Pattern recognition application in classification of intelligent composites during smart manufacturing using a C4.5 machine learning program

The development of an on line computer based classification system for the real time classification of different composites is addressed in this study. Different parameters were collected simultaneously when embeded sensors (dielectric, optical fiber, and piezoelectric sensors) were used within two different composite matrices during the curing process. The measurements were used by an algorithm software as a logged data file, resulting in to inducing a decision tree. Later, a systematic software is designed based on the rules derived from this decision tree, to recognise the type of composites used in the experiment together with recognition of their physical and mechanical characteristics. This is a new approach to data acquisition in intelligent materials produced by smart manufacturing system.

Constructing of cure monitoring system with piezoelectric ceramics for composite laminate

The cure monitoring system with piezoelectric ceramics is constructed. An embedded type piezoelectric ceramics sensor with flat lead wires is developed. And the piezoelectric ceramics is embedded into composite laminate. A dummy piezoelectric ceramics is set in the autoclave oven. The impedance of the piezoelectric ceramics which is embedded in the composite laminate and that of the dummy piezoelectric ceramics are measured by a LCR meter. The piezoelectric ceramics have strong temperature dependency. The temperature dependency of the impedance of piezoelectric ceramics is corrected by the information from the dummy piezoelectric ceramics. A dielectric sensor is also embedded in the composite laminate as a reference sensor for the degree of cure. The change in calculated cure index shows good correspondence with change in the log ion viscosity which is measured by the dielectric cure monitoring sensor.

Damping control of a CFRP cantilevered beam with electrorheological fluids actuator

Effects of waveform and frequency of electric fields applied to electro-rheological (ER) fluids are investigated on structural damping of a CFRP composite beam containing ER fluids. As the experimental results, the rectangular waveform is more effective for control of ER effects than the sinusoidal one. In vibration analysis, a simplified mass-spring-damper system is adopted to feature the first flexural mode of the cantilevered composite beam, where the damping factor is changed in time as a function of waveform which is applied to electric fields.