Scanning the steel 08G2B using superminiature eddy current probe

The article describes a hardware and software complex designed for defectoscopy and study of material properties. Sections of high-strength steel 08G2B pipes were scanned in the course of the research. The purpose of this study is to determine dependency of eddy current sensor signal and mechanical and operational properties of the base metal (K65 steel grade) and demonstrate the ability of developed eddy current probe to detect continuity defects and corrosion in this type of metal. The steel is ultra-low-carbon, which makes it possible to study their properties using the eddy current method. The eddy current method is a non-contact one being used both for cracks identification and determination of their characteristics. A special superminiature eddy current probe was developed, which includes three coils - stabilizing, measuring and exciting. The coils were placed on a pyramid-shaped core made of alloy 81NMA. The eddy-current transducer runs under the control of the developed hardware-software complex with a system for suppression of noise and amplification of signal received from the eddycurrent transducer. Signal processing makes it possible to separate the effects of closely spaced cracks on the eddy-current transducer signal and evaluate the contribution of each crack separately. As a parameter containing information about the presence of defects in the object of control, the voltage arrived at the measuring coil of the eddy current probe signal was used. The work studied sections of pipes with model continuity defects – cracks and holes. A research that allows to simulate the presence of corrosion in the metal was also conducted. The extreme values of the eddy current probe signal over defects of different types are obtained at various velocity, that allows to identify the type of defect, while changing the frequency of the signal on the probe allows to determine the depth of the defect.

Parasitic loads in torque standard machines: a characterization, comparison, and evaluation

In torque standard machines, different kinds of bearings are used to reduce the influence of parasitic loads under the assumption that such loads are low. In accordance with EURAMET cg-14, the signal of a torque transducer is averaged over three mounting positions. For this reason, the influence of parasitic loads on the transducer signal should be negligible. To test this assumption, two multi-component torque transducers are characterised in this study based on experimental, analytical, and numerical results. In this article, the parasitic loads of the torque standard machines at the Physikalisch-Technische Bundesanstalt (PTB), Teknologian tutkimuskeskus VTT Oy (VTT), and Cesky Metrologicky Institut (CMI) were characterised and compared. The results are presented together with a proposal for an evaluation.

An Active Self-Driven Piezoelectric Sensor Enabling Real-Time Respiration Monitoring

In this work, we report an active respiration monitoring sensor based on a piezoelectric-transducer-gated thin-film transistor (PTGTFT) aiming to measure respiration-induced dynamic force in real time with high sensitivity and robustness. It differs from passive piezoelectric sensors in that the piezoelectric transducer signal is rectified and amplified by the PTGTFT. Thus, a detailed and easy-to-analyze respiration rhythm waveform can be collected with a sufficient time resolution. The respiration rate, three phases of respiration cycle, as well as phase patterns can be further extracted for prognosis and caution of potential apnea and other respiratory abnormalities, making the PTGTFT a great promise for application in long-term real-time respiration monitoring.

Investigation of Uncertain Factors on Measuring Residual Stress with Critically Refracted Longitudinal Waves

Critically refracted longitudinal (LCR) waves are commonly used to evaluate the residual stress of a material. The utilization of LCR waves is advantageous in that these waves are not sensitive to the texture of the material. Thus, LCR can be considered as a bulk longitudinal mode and can penetrate into the material well below its surface. However, while measuring the residual stress, the precision of the LCR wave travel-time is influenced by several uncertain factors. In order to further improve the accuracy of test results, we developed a measurement approach based on three aspects. First, the distances between the transmitter and the receivers were determined by transducer signal analysis. Second, for the residual stress detection to be consistent, transducers with different frequencies presented similar beam divergence angles. Finally, three different frequencies were used to evaluate the residual stress throughout the plate thickness. Based on the results of the above analysis, we used LCR waves to test 304 stainless steel plates. The detection error of residual stress measurement was ca. ±23 MPa. When compared with the X-ray diffraction approach, our method showed similar trends for the same regions of the specimens.