This paper presents an Acoustic Emission (AE) to detect pitting corrosion in stainless steel. The AE signals were analyzed to reveal the correlation between AE parameters and severity levels of pitting corrosion in austenitic stainless steel 304 (SS304). In this work, the corrosion severity is graded roughly into five levels based on the depth of corrosion. Relationships between a number of time-domain AE parameters and the corrosion severity were first studied and key parameters identified. The corrosion severity was also categorized into three stages: initial, propagation and final stages based on the source mechanisms of the AE signals. We identified these stages from the frequency-domain characteristic of the AE signal and the visual characteristic of the corroded pits in each level of corrosion severity. A number of measures were employed to quantify such characteristics and the source mechanisms hypothesized. To demonstrate the usefulness of such parameters, a feed-forward neural network was used to classify the corrosion severity. Preprocessing and verification techniques were provided to facilitate and to maintain the generalization capability of the network. The classification performance is excellent and demonstrates that the AE technique and a neural network can be efficiently used to detect and monitor the occurrence of corrosion as well as to classify the corrosion severity.
<p class="Abstract" align="left">The National Institute of Metrology of Thailand’s (NIMT) strain-controlled elastic hinge-type torque standard machine was designed to cover a measuring range of 1 N·m to 1 kN·m. The elastic hinge was used both at the fulcrum and the hanger of the lever arms. The designed elastic hinge’s thickness, 0.50 mm, caused a higher stiffness than a sheet metal plate of other types of torque machines. The bending moment of all elastic hinges affected the sum of the torque signal on the lever arm that was used to observe the balancing of the lever. The residual torque sensitivity, which was no better than 0.20 mN·m, significantly affected the uncertainty of the low-range torque realisation.</p><p class="Abstract">The calibration and measurement capabilities of the machine were 0.010 % (<em>k</em> = 2) in the measurement range of 10 N·m to 1 kN·m and 0.030 % (<em>k</em> = 2) in the measurement range of 1 N·m to 10 N·m. In the transducer calibration, the influence of the random bending moment of the elastic hinge affected the repeatability, reproducibility, and linearity of the low torque measurements. The cause of the bending moment of the elastic hinges was a result of the deviation of the centre of gravity (CG) of the weight on the pan from the reference line. To improve CMCs, separate signal calibrations were selected for this experiment i.e. the left hinge, the right hinge, and the fulcrum. The torque in each signal calibration was combined by software and was used to correct the calibration value of the torque.</p>
<p class="Abstract">A Torque Standard Machine (TSM) with a rated capacity of 5 kN·m was designed and constructed by the Torque Laboratory, National Institute of Metrology (Thailand), NIMT. The machine had initially used a flexure bearing as a fulcrum. It had been developed based on the research of a 10 N·m suspended fulcrum TSM. However, the bearing structure was changed to a combination of eight elastic hinges in order to withstand larger cross-forces for providing greater strength and providing a shorter stabilising time, consuming the lever arm’s swing. With a three-column weightlifting system, the machine provides five measuring ranges ranging from 100 N·m to 5,000 N·m in the same set of stacked weights.</p><p class="Abstract">The measurement results showed the sensitivity of the fulcrum within ± 0.005 N·m from 10 % to 100 % of the measurement range. The sensitivity of the fulcrum is one of the main sources of the uncertainty evaluation of the torque measurement. The Calibration and Measurement Capabilities (CMCs) of the torque measurement were 0.01 % (<em>k=2</em>) in the measurement range from 500 N·m to 5,000 N·m. To confirm the capability of the measurement, an informal comparison with Physikalisch-Technische Bundesanstalt (PTB) was conducted. The results were satisfactory, with the |<em>E</em><sub>n</sub>| less than 1.</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.