Nkwachukwu Chukwuchekwa - Academia.edu (original) (raw)

Papers by Nkwachukwu Chukwuchekwa

Research paper thumbnail of Investigation of magnetic properties and Barkhausennoise of electrical steel

Research paper thumbnail of Barkhausen Noise in Grain-Oriented 3% Si-Fe AT 50 HZ

Barkhausen noise (BN) measurements were performed on samples of high permeability and conventiona... more Barkhausen noise (BN) measurements were performed on samples of high permeability and conventional grain-oriented steels at both high and low flux densities in order to investigate the characteristics in each magnetization regimes. Previous works deal with ...

Research paper thumbnail of Analysis of magnetic fields on the surface of grain oriented electrical steel

Magnetic properties of grain oriented electrical steel are often measured using well established ... more Magnetic properties of grain oriented electrical steel are often measured using well established surface field sensors. Use of magnetic domain observation, magnetic force microscopy (MFM) and Barkhausen noise measurement for studying magnetic properties and microstructure is demonstrated. It is shown that uncertainty over the region in which Barkhausen noise is detected needs clarification. It is further shown that different domain observation techniques appear to identify different types of micro structural features and that uniaxial magnetic field sensors may not reveal the total loss occurring in the steel. The origin of unusual MFM images is discussed.

Research paper thumbnail of arkhausen noise in grain-oriented 3% Si-Fe at 50 Hz

Journal of Electrical Engineering

Research paper thumbnail of Effect of magnetic domain refinement on barkhausen noise of large grain high permeability oriented electrical steel

Research paper thumbnail of Investigation of the Effects of Strips Thickness and Grain Size on AC Magnetic Barkhausen Noise of Grain-oriented Electrical Steel

Przeglad Elektrotechniczny

The influence of sample thickness and grain size of Conventional Grain-Oriented (CGO) and High Pe... more The influence of sample thickness and grain size of Conventional Grain-Oriented (CGO) and High Permeability Grain-oriented (HGO) steels on Magnetic Barkhausen Noise (MBN) of Epstein strips has been examined. It might be expected that MBN decreases with increasing sample thickness due to eddy current damping but the measurements show that the average domain width, hence the grain size influences MBN in strips less than 0.35 mm thick. From 0.35 mm and above, both strip thickness and domain width influence MBN in CGO and HGO. Streszczenie. Zbadano wpływ grubości próbki i rozmiaru ziarna dla stali konwencjonalnej o ziarnie zorientowanym (CGO) i stali o wysokiej przenikalności i ziarnie zorientowaym (HGO) na paskach Epsteina. Można oczekiwać, że amplituda sygnału Barkhausena MBN zmniejsza się wraz ze wzrostem grubości próbki z uwagi na efekt tłumienia od prądów wirowych, lecz pomiary wykazały, że średnia szerokość domen, związana z rozmiarem ziarna, ma wpływ na MBN w paskach o grubości mniejszej niż 0,35 mm. Dla grubości 0,35 mm i powyżej, grubość paska i szerokość ziarna mają wpływ na MBN zarówno dla stali CGO i HGO. (Badania wpływu grubości próbki i rozmiaru ziarna na efekt Barkhausena w blachach zorientowanych)

Research paper thumbnail of Effects of strip thickness and silicon content on Magnetic Barkhausen Noise of non-oriented electrical steel at 50 Hz

International Journal of Applied Electromagnetics and Mechanics

ABSTRACT

Research paper thumbnail of Models between Barkhausen noise and coercive force of grain-oriented electrical steel

Research paper thumbnail of Study of the Effects of Surface Coating on Magnetic Barkhausen Noise in Grain-Oriented Electrical Steel

IEEE Transactions on Magnetics, 2000

Magnetic Barkhausen Noise (BN) is a useful parameter for analysing physical and micro structural ... more Magnetic Barkhausen Noise (BN) is a useful parameter for analysing physical and micro structural properties of electrical steel. It is believed to be due to microscopic discontinuities in domain wall motion due to the presence of defects. Grain-oriented electrical steel has an insulating surface coating which provides a beneficial stress in the steel. BN is sensitive to changes in the surface condition of steels. Measurements have been carried out on strips of high permeability grain-oriented (HGO) and conventional grain-oriented (CGO) 3% silicon steels, at 50 Hz in the peak flux density range 8.0 mT to 1.0 T before and after chemical removal of the coatings. Coating removal from HGO and CGO materials increases BN at high and low fields. This can be explained in terms of widening of 180 domains due to the release of coating stresses so that domain walls move further between pinning sites thereby generating higher rates of change of magnetisation which result in higher BN. In the coated materials, BN was found to be higher in HGO than in CGO at flux densities above around 0.2 T but the trend changes at lower flux densities because of grain size/misorientation effects. However, it is interesting to note that in the decoated material the BN is higher in HGO at all flux densities. Application of a 3 MPa tensile stress to the decoated samples caused the BN below 0.2 T to become higher in CGO than in HGO demonstrating that domain refinement due to coating stress and externally applied stress produce similar effects on BN. A significant correlation was found between the average velocities of domain wall movement and changes in BN at all the peak flux densities in the test materials.

Research paper thumbnail of Effect of ball scribing on relative permeability of grain-oriented electrical steel

Acta Metallurgica Sinica (English Letters), 2013

Research paper thumbnail of Efficient Sideband Noise Cancellation for Co-located Networks Using ANCT

An efficient noise cancellation technique for a co-located network was realized using Adaptive No... more An efficient noise cancellation technique for a co-located network was realized using Adaptive Noise Cancellation Technique (ANCT). The technique was developed as improved feature to the classical application of passive filters. The paper focused on achieving a theoretical perfect cancellation considering three essential parameters: the amplitude, phase and delay characteristics of the signal and noise at both the primary path and the reference path of the co-located system. An experimental test-bed of the ANC Architecture was developed using Matlab-Simulink block design which demonstrated the error signals before and after cancellation.

Research paper thumbnail of Investigation of magnetic properties and Barkhausennoise of electrical steel

Research paper thumbnail of Barkhausen Noise in Grain-Oriented 3% Si-Fe AT 50 HZ

Barkhausen noise (BN) measurements were performed on samples of high permeability and conventiona... more Barkhausen noise (BN) measurements were performed on samples of high permeability and conventional grain-oriented steels at both high and low flux densities in order to investigate the characteristics in each magnetization regimes. Previous works deal with ...

Research paper thumbnail of Analysis of magnetic fields on the surface of grain oriented electrical steel

Magnetic properties of grain oriented electrical steel are often measured using well established ... more Magnetic properties of grain oriented electrical steel are often measured using well established surface field sensors. Use of magnetic domain observation, magnetic force microscopy (MFM) and Barkhausen noise measurement for studying magnetic properties and microstructure is demonstrated. It is shown that uncertainty over the region in which Barkhausen noise is detected needs clarification. It is further shown that different domain observation techniques appear to identify different types of micro structural features and that uniaxial magnetic field sensors may not reveal the total loss occurring in the steel. The origin of unusual MFM images is discussed.

Research paper thumbnail of arkhausen noise in grain-oriented 3% Si-Fe at 50 Hz

Journal of Electrical Engineering

Research paper thumbnail of Effect of magnetic domain refinement on barkhausen noise of large grain high permeability oriented electrical steel

Research paper thumbnail of Investigation of the Effects of Strips Thickness and Grain Size on AC Magnetic Barkhausen Noise of Grain-oriented Electrical Steel

Przeglad Elektrotechniczny

The influence of sample thickness and grain size of Conventional Grain-Oriented (CGO) and High Pe... more The influence of sample thickness and grain size of Conventional Grain-Oriented (CGO) and High Permeability Grain-oriented (HGO) steels on Magnetic Barkhausen Noise (MBN) of Epstein strips has been examined. It might be expected that MBN decreases with increasing sample thickness due to eddy current damping but the measurements show that the average domain width, hence the grain size influences MBN in strips less than 0.35 mm thick. From 0.35 mm and above, both strip thickness and domain width influence MBN in CGO and HGO. Streszczenie. Zbadano wpływ grubości próbki i rozmiaru ziarna dla stali konwencjonalnej o ziarnie zorientowanym (CGO) i stali o wysokiej przenikalności i ziarnie zorientowaym (HGO) na paskach Epsteina. Można oczekiwać, że amplituda sygnału Barkhausena MBN zmniejsza się wraz ze wzrostem grubości próbki z uwagi na efekt tłumienia od prądów wirowych, lecz pomiary wykazały, że średnia szerokość domen, związana z rozmiarem ziarna, ma wpływ na MBN w paskach o grubości mniejszej niż 0,35 mm. Dla grubości 0,35 mm i powyżej, grubość paska i szerokość ziarna mają wpływ na MBN zarówno dla stali CGO i HGO. (Badania wpływu grubości próbki i rozmiaru ziarna na efekt Barkhausena w blachach zorientowanych)

Research paper thumbnail of Effects of strip thickness and silicon content on Magnetic Barkhausen Noise of non-oriented electrical steel at 50 Hz

International Journal of Applied Electromagnetics and Mechanics

ABSTRACT

Research paper thumbnail of Models between Barkhausen noise and coercive force of grain-oriented electrical steel

Research paper thumbnail of Study of the Effects of Surface Coating on Magnetic Barkhausen Noise in Grain-Oriented Electrical Steel

IEEE Transactions on Magnetics, 2000

Magnetic Barkhausen Noise (BN) is a useful parameter for analysing physical and micro structural ... more Magnetic Barkhausen Noise (BN) is a useful parameter for analysing physical and micro structural properties of electrical steel. It is believed to be due to microscopic discontinuities in domain wall motion due to the presence of defects. Grain-oriented electrical steel has an insulating surface coating which provides a beneficial stress in the steel. BN is sensitive to changes in the surface condition of steels. Measurements have been carried out on strips of high permeability grain-oriented (HGO) and conventional grain-oriented (CGO) 3% silicon steels, at 50 Hz in the peak flux density range 8.0 mT to 1.0 T before and after chemical removal of the coatings. Coating removal from HGO and CGO materials increases BN at high and low fields. This can be explained in terms of widening of 180 domains due to the release of coating stresses so that domain walls move further between pinning sites thereby generating higher rates of change of magnetisation which result in higher BN. In the coated materials, BN was found to be higher in HGO than in CGO at flux densities above around 0.2 T but the trend changes at lower flux densities because of grain size/misorientation effects. However, it is interesting to note that in the decoated material the BN is higher in HGO at all flux densities. Application of a 3 MPa tensile stress to the decoated samples caused the BN below 0.2 T to become higher in CGO than in HGO demonstrating that domain refinement due to coating stress and externally applied stress produce similar effects on BN. A significant correlation was found between the average velocities of domain wall movement and changes in BN at all the peak flux densities in the test materials.

Research paper thumbnail of Effect of ball scribing on relative permeability of grain-oriented electrical steel

Acta Metallurgica Sinica (English Letters), 2013

Research paper thumbnail of Efficient Sideband Noise Cancellation for Co-located Networks Using ANCT

An efficient noise cancellation technique for a co-located network was realized using Adaptive No... more An efficient noise cancellation technique for a co-located network was realized using Adaptive Noise Cancellation Technique (ANCT). The technique was developed as improved feature to the classical application of passive filters. The paper focused on achieving a theoretical perfect cancellation considering three essential parameters: the amplitude, phase and delay characteristics of the signal and noise at both the primary path and the reference path of the co-located system. An experimental test-bed of the ANC Architecture was developed using Matlab-Simulink block design which demonstrated the error signals before and after cancellation.