Showing papers by "Tetsuya Uchimoto published in 2016"

Research advances in eddy current testing for maintenance of carbon fiber reinforced plastic composites

Abstract: This paper presents the overview of previous studies on the eddy current testing of Carbon Fiber Reinforced Plastic (CFRP) composites. CFRP is composed of many unidirectional carbon fiber/epoxy plies stacked together, thus it has laminated structure and inhomogeneous nature. Eddy Current Testing (ECT) is an efficient and non-contact Nondestructive Testing (NDT) technique for conductive materials. The electrical conductivity of carbon fibers can be utilized by ECT system for fiber texture mapping and detection of defects that can cause the conductivity change. Recently a lot of attention has been paid to the electromagnetic properties characterization of CFRP material, fiber texture and defect detection, as well as the ECT technique enhancement. In this paper we will give the detailed information and results of these research works. In addition this paper also summarizes the available numerical simulation methods for the electromagnetic modeling of CFRP materials, and the calculation of eddy currents and ECT signals.

Application of Monte Carlo method for magnetic clusters introduced thermal distributions

Abstract: Magnetic properties were calculated for magnetic clusters including different temperature regions inside using Monte Carlo method. The model for the calculations is on the assumption that each of grains made of spin array has a different thermal bath of different temperature. The calculation result for temperature dependences under weak applied magnetic field showed different magnetic reversal process for each of grains. The simulation using this model will be valuable for the analysis of magnetic systems introduced thermal distribution like a thermal assisted magnetic recording.

Development and Performance Evaluation of High Temperature Electromagnetic Acoustic Transducer

Abstract: Monitoring techniques are in demand in high temperature metal processing environments such as steel manufacturing facilities or foundries. Important processes that affect the quality of the final product are often carried out under high temperature conditions, and the materials can reach temperatures ranging from 600 to 1500 degrees C. Electromagnetic Acoustic Transducer (EMAT) can provide non-contact measurements, and is suitable for measurements in high temperature. Conventional EMAT uses rare-earth based magnets such as Nd or Sm-Co base ones for its bias magnetic sources, but the operation temperature of these types of magnets are limited by their Curie points. Recently, pulsed electromagnet EMAT which uses iron yoke is developed [1], and it is confirmed that this EMAT can be used up to 600 degrees C. However, to use it in higher temperature, it is supposed that the Curie point of iron yoke becomes a problem. This study proposes an EMAT that uses an air-cored pulsed electromagnet to overcome the Curie temperature limitations of these devices. For the purpose, we design the air-cored electromagnet, which can apply a sufficiently high magnetic field, and fabricate a prototype EMAT using high temperature materials as shown in Fig. 1. To evaluate the performance of the proposed EMAT, pulse-echo waveforms are measured under high temperature conditions. To increase the signal-to-noise ratio of the echo signals, the pulse-echo waveform is discussed in the frequency. As a result, the echo signals are successfully obtained over the temperature range from RT to 700 degrees C, and the reduction of shear wave velocity with increasing temperature is confirmed as shown in Fig. 2. This work was performed with partial support from a Grant-in-Aid for Challenging Exploratory Research (grant no. 24656080) from the Japan Society for the Promotion of Science (JSPS), and from the JSPS Core-to-Core Program, A. Advanced Research Networks, “International research core on smart layered materials and structures for energy saving”.