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An investigation was made into the Barkhausen noise responses of three duplex grades: a lean alloy LDX 2101, a conventional duplex 2205 and a super duplex 2507, in welded conditions. The aim was to study the influence of alloy chemistry and microstructure on the Barkhausen noise response. In addition, the residual stresses of the grades were measured by X-ray diffraction and the microstructure and hardness of the base materials and welds were determined. It was observed that the Barkhausen noise responses in the rolling direction and in the transverse direction were governed by the phase morphology of the materials. Only the root mean square of the Barkhausen noise burst seemed to be additionally dependent on the alloy chemistry through the hardness of the materials. Furthermore, the relationships between various characteristics of the Barkhausen noise burst measured in the rolling direction and the transverse direction and microstructural features are discussed. [ABSTRACT FROM AUTHOR]

The main aim of this report is to review the recent progress in the utilisation of Barkhausen noise and other magnetic testing methods for railway inspection and to provide a basis for follow-on research. This paper reviews the technologies currently employed along with examples of recent field applications. The three main research areas that this review focuses upon are the residual stress determination from rail tracks, the stress-free temperature (neutral temperature) determination with magnetic Barkhausen noise measurements and the study of the corrugation of railroads with Barkhausen noise. The Barkhausen noise features utilised in these studies are also reported. Finally, some preliminary measurements carried out on Finnish rail tracks with commercial Barkhausen noise equipment are presented. [ABSTRACT FROM AUTHOR]

Barkhausen noise measurement is an intriguing technique for the non-destructive testing of material properties. It is applicable to ferromagnetic materials and shown to be sensitive to many material properties. Typically, some features are calculated from the Barkhausen noise signal and compared to the material properties. However, the results are mainly qualitative. In this study, quantitative prediction of residual stress based on the Barkhausen noise measurement is studied. The studied material is case-hardened steel 18CrNiMo7-6 (EN 10084). The development of the prediction model is divided into feature generation and selection, followed by model identification and validation. In feature generation, the aim is to generate features as robust as possible, while in feature selection the most suitable features are selected to be used in the prediction model. In the model identification step, a simple linear regression model is identified. The model is validated in the final modelling step to ensure that it can also be used for future predictions. The identified model gives rather accurate predictions, indicating that the proposed modelling approach is applicable for predicting material properties from the Barkhausen noise signal. [ABSTRACT FROM AUTHOR]

Barkhausen noise (BN) is widely used as a quality control method for grinding burn detection in ferromagnetic materials such as the case-hardened steels used in gears. The study of grinding burns with BN equipment requires, however, a calibration reference sample with a known BN response. The demand for better calibration samples is well recognised. In this study, artificial grinding burns with laser processing were produced in case-hardened steel. The laser was selected because it is a surface-sensitive heating method and it accurately simulates the heat generation during grinding between the grinding wheel and work-piece. A test series was made by changing the laser input power and traverse rate to process the surface of a ground gear wheel sample. The laser-processing parameters were optimised experimentally. The BN measurement data was used in the modelling of selected quality measures: hardness and residual stress (RS). The BN measurement device provided some features from the time-domain analysis of the signal and a new feature, BN entropy, was also used. The modelling was done with Matlab® using linear regression. The results showed that laser processing had a clear effect on the BN features and residual stresses. [ABSTRACT FROM AUTHOR]

Renewable energy sources have become nowadays very popular. Wind energy is one of the most promising renewable energy sources of the future. Due to the booming energy markets and increasing production of wind turbines, the requirement for long-lasting and reliably working windmills has emerged. The Barkhausen noise (BN) method is a world-leading technique in the quality control of industrial grinding processes, for example in windmill gear production. The main goal for this study is to create a profound approach to the multiparameter Barkhausen noise measured and to compare the measured values to the absolute values obtained with other research methods such as residual stress measurements by X-ray diffraction, hardness measurements and microstructural studies. A test bar series was made from a case-hardened steel used in wind turbine gears. Different tempering parameters were used to vary the surface hardness of the test bars. A stepwise loading was done simultaneously with the BN measurements to obtain relevant multiparameter BN data and to investigate the effect of applied stress on the BN signal. The results indicate clearly that the response of the studied material is mainly consistent with the known BN relations, but there exist some unequal BN stress correlations in the tempered test bars. [ABSTRACT FROM AUTHOR]