ROTATING ELECTROMAGNETIC FIELD FOR NDT INSPECTIONS
Reliable performance of a component or structure depends on its pre-service quality and in-service degradation under operating conditions. The importance of Non-Destructive Testing and Evaluation is ever increasing, above all in ensuring pre-service quality and monitoring in-service degradation, in order to avoid premature failure of the components/structures. There are many Non-Destructive Techniques based on various physical principles. In this work, our main objective is the characterization of anomalies such as defects, stresses and microstructural degradations in materials. Particularly, in this work we propose a Finite Element Method based approach for modelling a fast and accurate evaluation of defects in metallic materials able to easily detect defects, aside from the orientation. Within this framework, the paper proposes the application of a magnetic fleld rotating perpendicularly to the analysed specimen. We discuss a few case studies, starting from numerical simulations and flnally highlighting the importance of this approach in order to evaluate the structural integrity assessment.
Eddy current examination of steel wires
Abstract This paper describes an automatic eddy current instrument designed and produced at the Center of Technical Physics of la§i and set up at the Metal Works, Cimpia Turzii, Romania. The diameter of the wires tested by the apparatus ranged between 2 and 9 mm. The control frequency can be adjusted between 1 and 100 kHz and the phase may be changed in steps of 15°. The test frequency was established theoretically so that the variations in the normalized components of impedance were highest for crack-type flaws. The theoretical results are compared with experimental ones for wires made of steel B 80N, 7 mm in diameter. By using a coil with a fill factor of 0.8 and a control speed of 1.5 m s −1 it was possible to reveal cracks with depths of 0.05 mm and 0.012 mm long, as well as areas of structural alteration due to the appearance of ferrite phases within the martensitic mass.
Traceability strategy for gear-pitch-measuring instruments: development and calibration of a multiball artifact
There is a strong demand to ensure the traceability of gear-measuring instruments (GMIs). We propose a multiball artifact (MBA) for the evaluation of pitch-measuring accuracy. The aim of the MBA is to transfer the minimum uncertainty from a calibrated value at the National Metrology Institute of Japan (NMIJ) to a measured value of GMIs at a shop floor. The MBA is composed of equally spaced high-accuracy balls around an axis. The pitch-measuring accuracy of GMIs is evaluated by measuring the angular pitch deviation of the balls instead of the angular pitch deviation of a gear. We calibrated the angular pitch deviation using a coordinate measuring instrument (CMM) at the NMIJ and adapting a multiple-orientation technique. We proposed a calibration strategy of the angular pitch deviation. The calibration value of the pitch deviation for the MBA at the NMIJ was obtained with a measurement uncertainty (U95) of 0.2 µm. We evaluated the pitch-measuring accuracy of a GMI using the calibrated MBA. Each value of U95 for the cumulative and single pitch deviations for the left and right flanks was less than or equal to 0.5 µm. The small uncertainty was transferred from the NMIJ to the GMI.