Noushin Karimian

Measurement of electromagnetic properties of power station steels

Accurate measurement of electromagnetic properties of steels is of significant importance as EM properties are indicative of microstructure and hence properties of the material. In this paper, we present the measurement of cylindrical power station steel samples in different microstructural states representative of their initial condition and after service exposure. Cylindrical air cored sensors were used. Analytical and numerical methods (Finite Elements Methods) were employed to calculate the sensor response of these samples. Experimental results were obtained for a range of samples and their electromagnetic properties inferred by fitting finite element models to the measured results. In addition, sensitivity and error analysis were carried out to evaluate the accuracy of the method.

Classification of Nonferrous Metals Using Magnetic Induction Spectroscopy

Recycling automotive, electronic, and other end-of-life waste liberates large quantities of metals, which can be returned to the supply chain. Sorting the nonferrous metals, however, is not straightforward. Common methods range from laborious hand-sorting to expensive and environmentally deleterious wet processes. The goal is to move toward dry processes, such as induction sensors and vision systems, which can identify and sort nonferrous scrap efficiently and economically. In this paper, we present a new classification method using magnetic induction spectroscopy (MIS) to sort three high-value metals that make up the majority of the nonferrous fraction—copper, aluminum, and brass. Two approaches are investigated: the first uses MIS with a set of geometric features returned by a vision system, where metal fragments are matched to known test pieces from a training set. The second approach uses MIS only . A surprisingly effective classifier can be constructed by combining the MIS frequency components in a manner determined by how eddy currents circulate in the metal fragment. An average precision and recall (purity and recovery rate) of around 92% was shown. This has significant industrial relevance, as the MIS-only classifier is simple, scalable, and straightforward to implement on existing commercial sorting lines.

Fast classification of non-magnetic metal targets using eddy-current based impedance spectroscopy

We present a new method to sort non-magnetic conductive metals — specifically brass, copper and aluminium — with the aim of improving economic yields in the scrap metal and recycling industries. The method uses the impedance spectra of the metal objects derived from the scattered magnetic field. Preliminary results are presented on a small sample set showing good accuracy across all metal classes even when the test objects are travelling at high speeds (1 m/s). The results suggest the method is both feasible and practical at the high-throughput demanded by industry.

Non-contact EM measurement of the properties of power station steels taken from service

Analysis of the electromagnetic properties of power station steels, measured using a non-contact EM sensor, is of significance as such properties are indicative of the microstructure of the material. In this paper, we present the measurement of cylindrical power station steel samples (namely P91 and P9 grades) in different conditions. Initially the B-H curves of these steel samples were measured. Then printed circuit board (PCB) coil integrated sensors were used to measure the incremental permeability. Analytical and numerical methods (Finite Elements Methods) were employed to calculate the sensor response of these samples. Experimental results were obtained for a range of samples and their electromagnetic properties inferred by fitting finite element models to the measured results.

Magnetic sensing for microstructural assessment of power station steels: Differential permeability and magnetic hysteresis

Failure of power station steel components can have severe economic impacts and also present significant risks to life and the environment. Currently components are inspected during costly shut-downs as no in-situ technique exists to monitor changes in microstructure of in-service steel components. Electromagnetic inspection has the potential to provide information on microstructure changes in power station steels in-situ. In this paper, tests have been carried out on pipe and tube samples in different microstructural conditions, using a lab-based closed magnetic circuit and impedance measurement systems. EM properties have been identified with correlations to material properties, which can quantify degradation in-situ and at elevated temperatures.

Magnetic sensing for microstructural assessment of power station steels: Magnetic Barkhausen noise and minor loop measurements

There are currently no techniques available to monitor the microstructural condition of power station steel components in-service (at elevated temperatures). Electromagnetic (EM) inspection methods have the potential to provide a solution to this problem. Tests have been carried out on power generation steel (P9 and T22) samples with different microstructural states using major and minor B-H loop measurements and correlations established between EM properties and material properties such as Vickers hardness. These correlations will be used to develop a field deployable tool for the quantification of degradation in power station steels.