In recent years, iron-based materials such as steel have been utilized in many structural components. We have already proposed the fatigue evaluation method for steel by measuring an inductance of a pancake-type coil using an LCR meter. In the case of low carbon steel, pulsating tension fatigue was evaluated using the inductance method. In the case of steel such as SS400, pulsating tension fatigue was evaluated using the inductance method on both conditions when the dc magnetic field was not applied when the dc magnetic field was applied. The dc magnetic field was generated by a neodymium (Nd) permanent magnet. There is a good correlation between the amount of pulsating tension fatigue and the inductance of the pancake-type coil. This paper describes the inductance method for fatigue evaluation in steel.
This paper presents a non-destructive evaluation for high chrome Fe-based steels by using a magnetic sensor. In order to make clear the fundamental magnetic properties related to tensile strain damage and fatigue damage, the magnetic measurement apparatus, which can measure the magnetic flux density and the magnetic field strength by B-coil and H-coil, was developed. And then the relationships between the damages and the measured magnetic properties are shown to discuss the capability of a non-destructive testing for high chrome Fe-based steels. The developed magnetic sensor was applied to make clear magnetic properties related to material changes with creep damage. The measured magnetic properties showed the material changes due to creep damages, and these results were discussed for the capability of a non-destructive evaluation to detect the creep damages on high chrome Fe-based steels.
Magnetic hysteresis chacteristics have good correlation with material degradations, and magnetic flux leakage technique detects small defects in ferromagnetic steels. Both methods use a single magnetic yoke, therefore we have a potential to evaluate simultaneously material degradation and small defects using a single magnetic measurement system. In this study, we composed an electromagnetic sensor, which can measure hysteresis curves and detect leakage magnetic flux near surface of the specimen, and tried simultaneous evaluations of degradation and sub-mm sized defects. The hysteresis curves are sensitive to material degradation, while are sensitive to small defects. Though magnetic flux leakage can detect small defects, it does not show a significant change against degradation. We successfully evaluated material degradation and small defects separately with the single measurement system.
In this paper, a summary of the software which authors are currently developing for the purpose of Non Destructive Inspection and lifetime evaluation is explained. In addition, the mathematical background of the calculation carried out inside of the software is remarked, with particular emphasis on the inverse problem based on Tikhonov's regularization method, the L-curve method and the mesh-independent stress analysis based on the extended finite element method (XFEM).
The present paper has investigated the effects of parameters in the in-service inspections (ISI's) of time-based maintenance (TBM) or periodic maintenance on the rupture probability of a structural component subjected to creep. It is assumed that creep strain monitored in-service at regular time intervals to be a random variable following two-parameter Weibull distributions of the means and the standard deviations given by the modified θ method. The effects of such parameters as the allowable strain, the rupture strain and the shape parameters of the Weibull distributions on the rupture probability of the structural component is formulated based on Bayes' theorem and is calculated considering the replacement of the component in a total operation hour of 105 hr. The replacement model simulates TBM in which creep strain of a component is found to reach the allowable strain level and is replaced with a new one having zero creep strain. Variations of the rupture probability of the model with the parameters above were calculated and discussed.
Induction heating type hyperthermia treatment needs both high magnetic fields (> 2 mT) and a few hundred kHz inside of a body to heat magnetic particles and implant materials up to 43°C. We proposed the double-pancake type coils sandwiching human body。 The exciting coils of human scale could generate magnetic fields with both magnitude and frequency required to a medical treatment. In order to make magnetic fields inside a deep body further increase, we proposed that a back yoke as magnetic materials was added to both coils. The paper discussed magnetic- and electrical-circuit characteristics of the coils with a magnetic sheet and ferrite as back yoke.
Recently, the need for primary health care becomes stronger for general users to perform at home. This study is to develop a multichannel cardiac sounds in-home measuring system for monitoring children's congenital heart diseases (CHD). Children's cardiac auscultation is always influenced by their hyperactivity or breathing loudly, in view of this circumstance, the multichannel measuring system with auscultation clothes and electronic stethoscopes is designed to obtain the multichannel cardiac signals simultaneously. Further, the multichannel signals analysis methods are proposed to extract the diagnosis features, which are heart rates by characteristic moment waveform in time domain, frequency width by AR-PSD in frequency domain and murmur index by WPE from energy analysis. These effective parameters are using for children's parents and doctors to monitor disease state in simple and convenient way. This home health care system is verified to be useful and convenient for not only physicians but also general users.
In recent years, energy harvesting is an attractive research for worldwide engineers. An environmental magnetic field around power lines and electric appliances could be regarded as a reusable energy source. This paper considers the impedance matching on power conversion circuit for magnetic energy circuit. The Cockcroft-Walton circuit consisting of ideal diodes are used for this considerations. Based on the maximum power transfer theorem, the optimum load is expressed by the two parameters: input resistance and number of steps in the Cockcroft-Walton circuit. From both the analysis and experimental results, the estimated output voltage and power are confirmed.
Expensive equipments are usually necessary for the measurement of inductor characteristics in power converters. This paper proposes a simple measurement method without using them. It is composed of a coil to detect the voltage, a resistance to detect the current and an Excel file with a macro program for the Fourier analysis. The loss characteristic and B-H curve are outputted automatically using the proposed method. The inductance, resistance, iron loss and harmonic copper loss of an inductor are measured and discussed theoretically.
Linear DC motors (LDM), used in office automation equipments (OA) such as line printers and image scanners, are required to be with high acceleration and fast-response. Under the condition of limited power supply capacity and an outside dimension, the structure of LDM to make the acceleration rise most quickly is investigated by using finite element method. The target of acceleration, direct current and response time of acceleration are 490 m/s2, below10 A and 0.15 ms. As a result, maximum acceleration is 516 m/s2 and response time of acceleration is 0.125 ms, so the target is achieved.
Magnetic analysis method considering vector magnetic characteristic and two-dimensional magnetostriction of electrical steel sheet is suggested and distribution of the two-dimensional magnetostriction on transformer model core is clear by the analytical method. In particularly, the large magnetostriction occurs at T joint part due to occurrence of rotating magnetic flux. And, large principal magnetostriction of contraction occurs in rolling direction at same part. In order to validate the validity of the analyzed results, it is necessary to measure the local two-dimensional magnetostriction of the transformer model core. This paper presents measurement of the local vector magnetic characteristic and the local two-dimensional magnetostriction of three-phase transformer model core and the measured results are discussed.
Plasma actuator is up to date and innovative device for flow control. Plasma actuator can induce wall-jet flow by dielectric barrier discharge mechanism. Plasma actuator has many advantages (1) Light weight and simple structure, (2) No drive mechanism, (3) High jet velocity, and (4) Rapid response. Plasma actuator is effective in preventing flow separation in many fluid machinery and engineering devices by these features. We will introduce various applications for flow separation control.
The final aim of this research is to develop a quantitative evaluation system of shoulder joint function using the three-dimensional force display robot. In this paper, we proposed a screening test method for motor functional decline of shoulder joint function. Firstly, we proposed an estimation method of joint angles of upper extremity during the constant velocity section by measuring the force exerted by a subject. Secondly we proposed a screeing test method by analying the motion of therapist's manual test. Lastly, by comparing the test results of the proposed method and the test results by the therapist, we confimed the screening accuracy of the porposed method.
In this research, the effects of two types of electrical circuits, which detect back Electromotive Force (EMF) signals and output six step square waveform rotor position signals of 3 phase Brushless DC (BLDC) motors, on sensorless control are analyzed by implementing a coupled analysis of a Finite Elements Method (FEM) model of a BLDC motor and the electrical circuit. The 1st electrical circuit uses a dynamic threshold level which changes automatically according to the back EMF maximum level, and the 2nd electrical circuit uses a static threshold level which is determined at the start of motor control and is fixed regardless of the back EMF maximum level. Also, the results of the coupled analysis are verified by implementing experimental evaluation using an 8 pole 12 slot BLDC motor and embedded motor controller. Through this research, the advantages of the 1st electrical circuit is verified.
IPMC (Ionic Polymer Metal Composite) actuators have numerous promising applications in designing electroactive soft motion structures. It was reported that the bending behavior of Selemion CMV-based IPMC in response to the electrical stimulation was quite susceptible to the environmental absolute humidity, and the environmental absolute humidity increase appeared to cause the unstable bending of Selemion CMV-based IPMC. Previously a circuit model for the analysis of Selemion CMV-based IPMC bending behavior was proposed and it actually resulted in quite successful prediction of bending behavior. However, it does not provide us with any information of bending stability. In this study, using Simulink - Matlab, an open loop model was built, based on the circuit model, the stability analysis of Selemion CMV-based IPMC bending was carried out.