Grinding burn detection via magnetic barkhausen noise analysis independently of induction hardened depth

The electromagnetic technique based on magnetic Barkhausen noise (MBN) can be used to control the quality of ball screw shafts non-destructively, although identifying any slight grinding burns independently of induction-hardened depth remains a challenge. The capacity to detect slight grinding burns was studied using a set of ball screw shafts manufactured by means of different induction hardening treatments and different grinding conditions (some of them under abnormal conditions for the purpose of generating grinding burns), and MBN measurements were taken in the whole group of ball screw shafts. Additionally, some of them were tested using two different MBN systems in order to better understand the effect of the slight grinding burns, while Vickers microhardness and nanohardness measurements were taken in selected samples. To detect the grinding burns (both slight anddata intense) with varying depths of the hardened layer, a multiparametric analysis of the MBN signal is proposed using the main parameters of the MBN two-peak envelope. At first, the samples are classified into groups depending on their hardened layer depth, estimated using the intensity of the magnetic field measured on the first peak (H1) parameter, and the threshold functions of two parameters (the minimum amplitude between the peaks of the MBN envelope (MIN) and the amplitude of the second peak (P2)) are then determined to detect the slight grinding burns for the different groups

The application of electromagnetic measurements for the assessment of skin passed steel samples

This paper begins by exploring the relationship between magnetic properties such as coercive field, RMS Magnetic Barkhausen Noise (MBN), initial and differential permeability and percentage elongation of skin passed samples for three different steels; interstitial free, micro alloyed and dual phase. A closed magnetic loop system is used to measure the fundamental magnetisation properties and a system based on an impedance analyser and a cylindrical coil is used to determine low field differential permeability. The results show that coercive field increases consistently with increasing percentage elongation for all three steels, as increasing material hardness causes an increase in magnetic hardness and a corresponding increase in coercive field. This effect levels off at higher values as dislocation density saturates. As would be expected, the inverse trend is observed for differential permeability. Similar results are also reported for MBN and initial and low field differential permeability measurements for the interstitial free and dual phase steel, but the behaviour for the micro alloyed samples appears to be more complex. Finally, the paper considers the response of two on-line measurement systems that exploit these magnetic relations. The first system applies pulse excitation and measures the resulting remnant magnetisation and the second analyses the harmonic response from AC excitation. Both systems can detect microstructural changes associated with varying magnetic properties during strip production

Designing stem-cell-based dopamine cell replacement trials for Parkinson's disease

Clinical studies of Parkinson’s disease (PD) using a dopamine cell replacment strategy have been tried for more than 30 years. The outcomes following transplantation of human fetal ventral mesencephalic tissue (hfVM) have been variable, with some patients coming off their anti-PD treatment for many years and others not responding and/or developing significant side effects, including graft-induced dyskinesia. This led to a re-appraisal of the best way to do such trials, which resulted in a new European-Union-funded allograft trial with fetal dopamine cells across several centers in Europe. This new trial, TRANSEURO (NCT01898390), is an open-label study in which some individuals in a large observational cohort of patients with mild PD who were undergoing identical assessments were randomly selected to receive transplants of hfVM. The TRANSEURO trial is currently ongoing as researchers have completed both recruitment into a large multicenter observational study of younger onset early-stage PD and transplantation of hfVM in 11 patients. While completion of TRANSEURO is not expected until 2021, we feel that sharing the rationale for the design of TRANSEURO, along with the lessons we have learned along the way, can help inform researchers and facilitate planning of transplants of dopamine-producing cells derived from human pluripotent stem cells for future clinical trials

Nondestructive characterization of recovery and recrystallization in cold rolled low carbon steel by magnetic hysteresis loops

How structure sensitive parameters derived from hysteresis loops can provide nondestructive information about the evolution of the microstructure of cold rolled low carbon steel as a result of recovery and recrystallization processes during the annealing is shown. The coercive field, remanent induction and hysteresis losses can be used to monitor the decrease in the dislocation density during recovery. These parameters are also influenced by the average grain refinement that takes place during recrystallization, which compensates the variation produced by the annihilation of dislocations during recrystallization. The maximum of the induction and of the relative differential permeability are shown to be very sensitive to the onset and to the monitoring of the recrystallization, respectively. The correlations between coercive field and remanent induction and hysteresis losses can also be used to distinguish between recovery and recrystallization

A completely configurable digital system for simultaneous measurements of hysteresis loops and barkhausen noise

This paper describes a new accurate completely digital configurable computer-aided system for the simultaneous measurements of magnetic hysteresis loops and Barkhausen noise in a wide range of excitation frequencies (from 0.01 to 80 Hz) for the purposes of inspection of material properties and microstructure characterization. The importance of the correct choice of the data-acquisition (DAQ) card to have enough resolution in both hysteresis loop and magnetic Barkhausen noise (MBN) measurements is emphasized. Both the magnetic induction signal to construct the magnetic hysteresis loop and the Barkhausen noise are computed by the digital processing (numerical integration and digital filtering, respectively) of the induced electromotive force (EMF) signal. The accuracy of the hysteresis loop measurements is improved by using additional digital filters. The resolution of MBN results in simultaneous measurements is tested. Finally, some results of hysteresis loops and root-mean-square (RMS) envelopes of the MBN signal are presented to show the capability of the system to work at different excitation frequencies without changing any hardware

Magnetic Barkhausen noise for characterization of recovery and recrystallization.

The capacity of magnetic Barkhausen noise (MBN) measurements to characterize recovery and the onset and evolution of recrystallization processes occurring during the annealing of cold rolled low carbon steel is analyzed. Cold rolled low carbon steel samples were isothermally annealed at laboratory under different conditions in order to promote various degrees of recovery or recrystallization. The effect of recovery and recrystallization processes on the MBN envelope, the amplitude of the peak of the MBN envelope, the time integral of the MBN envelope and the MBN energy is discussed and related to the microstructural changes produced by these softening processes. The obtained results prove that several parameters derived from the MBN are able to follow the progress of recovery and recrystallization

Induction hardened layer characterization and grinding burn detection by magnetic Barkhausen noise analysis

The quality of the ball screw shafts used in the aeronautical sector has to be controlled and certified with the most advanced non-destructive techniques. The capacity of magnetic Barkhausen noise(MBN) as a non-destructive technique to control the quality of ball screw shafts by assuring the appropriate induction hardened layer depth and detecting local overheated regions, known as grinding burns, which may occur during grinding processes is shown in the present work. Magnetic Barkhausen noise measurements were made with a system designed and implemented by the authors and the derived parameters were compared with microhardness measurements made at various depths after the different induction hardening treatments and the grinding processes were applied. A multiparametric study of the MBN signal as a function of the magnetic field in the surface of the sample is done in order to estimate the thickness of the hardened layer and to detect the grinding burns produced during grinding processes. The hardened layer thickness can be characterized with an error of +/- 200 mu m in the range between 150 and 2500 mu m by the position of the first peak of the MBN envelope in terms of the tangential magnetic field measured at the surface and the grinding burns can be detected with the position of the second peak of the MBN envelope in terms of the tangential magnetic field measured at the surface

Quantitative estimation of nonmonotonic residual stress depth-profiles using an extended Kypris-Jiles model of the magnetic Barkhausen noise spectrum

Using nondestructive techniques to quantitatively estimate residual stresses along the depth is necessary to improve the ability to predict the real fatigue life of pieces for many applications. Magnetic Barkhausen noise has been proven to successfully estimate the residual stress at the surface produced by machining, plastic deformation, phase transformation or surface treatments such as shot peening, also allowing one to obtain information of the residual stress depth-profile in shot peened pieces which presented similar depth-profile shapes. However, residual stress depth-profiles with nonmonotonic or different shapes have not been successfully estimated. In the present study, an extended approach is developed in order to estimate these stresses independent of the shape of the residual stress depth-profile. The approach proposed here improves an existing model of the Barkhausen noise spectrum (Kypris-Jiles model) by adding the effect of the attenuation of the applied magnetic field on the Barkhausen noise. This extended approach is used to estimate the residual stress depth-profiles of samples with different depth-profiles using a calibration process. The approach is validated by estimating the residual stress depth-profiles, with errors smaller than 70 MPa in a depth of 130 mu m, in all the samples studie

Grinding burn detection via magnetic barkhausen noise analysis independently of induction hardened depth

The electromagnetic technique based on magnetic Barkhausen noise (MBN) can be used to control the quality of ball screw shafts non-destructively, although identifying any slight grinding burns independently of induction-hardened depth remains a challenge. The capacity to detect slight grinding burns was studied using a set of ball screw shafts manufactured by means of different induction hardening treatments and different grinding conditions (some of them under abnormal conditions for the purpose of generating grinding burns), and MBN measurements were taken in the whole group of ball screw shafts. Additionally, some of them were tested using two different MBN systems in order to better understand the effect of the slight grinding burns, while Vickers microhardness and nanohardness measurements were taken in selected samples. To detect the grinding burns (both slight anddata intense) with varying depths of the hardened layer, a multiparametric analysis of the MBN signal is proposed using the main parameters of the MBN two-peak envelope. At first, the samples are classified into groups depending on their hardened layer depth, estimated using the intensity of the magnetic field measured on the first peak (H1) parameter, and the threshold functions of two parameters (the minimum amplitude between the peaks of the MBN envelope (MIN) and the amplitude of the second peak (P2)) are then determined to detect the slight grinding burns for the different groups

Modeling the impact on wheel sensor readouts by Eddy Current Brakes installed in high-speed trains

This paper presents a model to anticipate the impact of Eddy Current Brakes (ECBs) installed in high-speed trains on the readouts of rail-side wheel sensors. The purpose is to anticipate false positive readouts of train wheels when traversing, one of the main obstacles for full ECB deployment. The ECB type EWB 154 from Knorr-Bremse and Wheel Sensor types RSR180 and RSR123 from Frauscher Sensor Technology are represented in a comprehensive model, integrating LTSpice and CST Microwave Studio. The wheel sensor predicted readout error is 4% compared to measurements when DC current is not applied to the ECB (passive case). It is demonstrated that the RSR180 is not compatible with ECBs, whereas the RSR123 is. The impact of active (DC current fed) brakes is analyzed when performing running tests with a high-speed ICE 3 train equipped with ECBs. The model is adjusted to study the saturation of the rail and ECB pole cores. The extra damping of the wheel sensor fingerprint is modeled by an extra 6% drop that may well be applicable to passive tests in a laboratory setting to shift to active tests without actually performing them. In this way, cost and time would be saved. Based on the model outcomes, a test bench is recommended for laboratory tests to emulate active behavior