Papers by Keyword: Barkhausen Noise

Abstract: Barkhausen noise (BHN) measurement is one of electromagnetic testing methods that is suitable for ferromagnetic materials. It has a sensitivity to different material properties such as microstructure, composition, residue stress, hardness, etc. which can also be used to determine the hardness case depth of a hardened layer. The measurement is intriguing because of its time and cost-effectiveness. The aim of this work was to study and select a suitable method to evaluate and predict the hardness case depth of induction hardened S50C steel based on Barkhausen noise measurement. Signal processing of BHN signal was performed and extracted features were validated with the actual hardness case depth according to the destructive method of Vickers hardness and metallography in order to achieve the most accurate hardness case depth evaluation model. The results showed that the hardness case depth prediction model could be used to indicate the hardness case depth of induction hardened steel significantly at the correlation coefficient (R) of 0.97 and root mean squares error of estimation (RMSEE) of 3.56%.

Abstract: Barkhausen noise (BHN) is a technique that can be used to evaluate properties of ferromagnetic materials; case depth, coating depth, residual stress, grinding burnt damage, and hardness of a metallic material. The commercial BHN measuring devices commonly used are relatively expensive. Therefore, the steel industries in Thailand hardly use in their production process. A cost-effective measuring system based on BHN was developed in this research. The developed machine was tested by measuring the hardness of different steels. The hardness measured by the developed BHN system was validated with the hardness measured by the Vickers hardness test. It can be concluded that this proposed measuring machine can estimate the hardness of steels with accuracy of 96.76 percent on average (in hardness rage of 150 – 800 HV). This development can also be applied to measure other properties if the appropriate operating parameters of the machine are changed and calibrated with reliable standards.

Abstract: Steel weld seams are characterized by heterogeneity of their microstructure. Microstructure affects the nature of the distribution, sign and magnitude of residual stresses. In combination with unfavorable factors (low temperature, metal hypoductility and an unsuccessful joint form) residual stresses lead to a decrease of load carrying capacity of a whole structure. In a weld seam residual stresses are distributed in a complex way and can affect the build quality of heavy section welded structures. Monitoring of residual stresses remains a big problem. Residual stresses in welds are often evaluated only by modeling. Unfortunately, all mathematical models describe the stress state of the welded material with low accuracy. Simple quality control, the results of which can be easy interpreted, is necessary. Welded joints made by manual arc welding and by automatic submerged arc welding were investigated. Butt seams of steel sheets of different thickness have been welded. Steel was low-carbon and low-alloyed. It is often used in welded structures for various purposes, including construction, and for pipelines manufacture. The temperature range of welded structures operation is very large – from-70 to 450С. The authors studied the structure of butt weld seams by the Barkhausen noise method, which is interesting as it represents an alternative to the known methods, which characterizes the structure and stress state of material. The relationship between the weld microstructure and magnetic noise is shown. Studies have allowed us to establish the relationship between the structure and magnetic properties and to evaluate the feasibility of applying the Barkhausen noise method to welded structures.

Abstract: Carrying out fatigue testing of reactor vessel material 15H2MFA acoustic emission sensors were applied to follow changes. It is shown, that observed bursts can be explained only with appearance of acoustic Barkhausen Effect (ABE). Interesting source localization is shown during heat treatment and consecutive stress test, which can be explained acoustic emission due to material transition from martenzit phase to bainite phase. Observed ABE opens the way to apply it in industry using magnetic stresses to provoke acoustic response for characterization of the state of the magnetic materials.

Abstract: The plasma processing causes a change of a surface layer structure and characteristics of the surface layer of the material. During plasma processing the surface is subjected to ultrafast heating and cooling which causes a thin hardened layer, and the resulting non-equilibrium structure of the layer provides properties that are different from the properties of the base metal. Since transformations in alloys due to the ultrafast heating by highly concentrated energy flows are not sufficiently explored, the surface layer structural state and its properties are of a great practical and scientific interest. The article presents study results of the St3ps steel after surface hardening with plasma arc. To study the structure of steel, the author used the microanalysis, the magnetostructural Barkhausen Noise Method; residual stresses have been determined by the x-ray diffraction. The study revealed correlation between the processing mode, steel microstructure, residual stress values and the Barkhausen noise amplitude.

Abstract: Machined surface of hard steel parts like gears, bearings, camshafts etc. is full of local imperfections which are commonly described in terms of surface integrity. This surface integrity is usually quantified with the level of residual stresses or amplitude of Barkhausen noise signal for instance. The contribution introduces parameter called Sum of Effective Residual Stresses (SERS) to describe the level of surface damage after grinding. Experimental data obtained by X-Ray Diffraction (XRD) and Barkhausen Noise Analysis (BNA) methods of ground gears are shown. The way to use SERS approach for experimental determination of penetration depth of Barkhausen signal in steels is proposed, too.

Abstract: Non-destructive methods for detection and measurement of residual stresses (RS) have been increasingly used in the last few years. The paper outlines the capability of Barkhausen noise analysis (BNA) for evaluation of real structure changes and RS on cross-section of welds due to welding of ferromagnetic plates compared with X-ray diffraction (XRD). The purpose of this study is to evaluate the RS distribution of specimens joined using by high power diode laser and metal active gas (MAG) welding that can be used for quantitative analysis of macro and micro level RS separately. The principal advantages of BNA over XRD as a tool for RS analysis and real structure characterisation are that it is mobile, faster with more facile carrying out and hence BNA is frequently used for continuous monitoring of RS in industrial processes.

Abstract: This paper deals with the non-destructive evaluation of surface made of hardened roll bearing steel after hard milling via Barkhausen noise technique. The paper discusses magnetic anisotropy linked with the structure transformations with regard to variable flank wear of cutting tool. Effective value of Barkhausen noise (BN) and Peak Position derived from the raw BN signal as well as BN envelopes are compared with metallographic observations and theoretical background about magnetic domains reconfiguration when the near surface undergoes severe plastic deformation at elevated temperatures.

Abstract: The present paper investigates the utilization of both the magnetic Barkhausen noise and permeability measurements for the nondestructive distinguish of the three welding zones in a welded low carbon steel.

Abstract: Magnetic nondestructive testing methods including eddy current testing, magnetic memory, magnetic Barkhausen noise and so on are widely used in testing mechanical properties of ferromagnetic parts. Experiments were done to study the relationship between hardness and magnetic properties of ultra-high strength steel (UHSS), which plays an important role in automobile industry. The magnetic properties of UHSS specimens with different hardness were studied. The result shows that there is a strong connection between hardness and magnetic properties. Coercive force of UHSS is proportional to the hardness. This can be used to explain certain mechanism of magnetic nondestructive testing method such as connection between hardness and Barkhausen noise.