Correlation between ultrasonic velocity and magnetic adaptive testing in flake graphite cast iron

A recently developed nondestructive method, called Magnetic Adaptive Testing was applied for investigation of flake graphite cast iron samples having various metallic matrices and graphite structures. MAT is typical by its low required magnetization of samples, because it is based on measurement of families of minor magnetic hysteresis loops. The flat samples were magnetized by an attached yoke and sensitive descriptors of their magnetic/structural state were obtained from evaluation of the measured data. Ultrasonic velocity measurements were performed and results of the non-destructive magnetic tests were compared with these data. A very good correlation was found between the magnetic descriptors and ultrasonic velocity.Web of Science667s17717

Nondestructive detection of local material thinning in ferromagnetic materials by Magnetic Adaptive Testing

A recently developed nondestructive method, called Magnetic Adaptive Testing, which is based on systematic measurement and evaluation of minor magnetic hysteresis loops was applied for detection of local material thinning in a thick, L-shaped ferromagnetic carbon steel, which simulates T-tubes with reinforcing plates. Artificially made slots were reliably detected with a good signal/noise ratio from the other side of the specimen, even through a covering ferromagnetic plate

Development and Performance Evaluation of High Temperature Electromagnetic Acoustic Transducer

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”