Harmonic analysis of B-H loops of constructional steel

B-H loops taken during plastic deformation of BS 4360(1979) 5OD constructional steel have been decomposed by Fourier analysis. An initial monotonic decrease is found in all odd order, odd power harmonic components with increasing plastic strain. The change in even order first harmonic was found to be proportional to the change in coercivity and increased in magnitude with strain. Changes in harmonic content during plastic deformation are compared with those observed following annealing and fatigue. The technique permits easy reconstruction of B-H loops at any point from digitized data.