Annual Meeting, May 7-8.
H AY HHO-T EX HMHECHA*
ACTION T)F STRAIN IN MILD STEELS.
EW6J1M^r.fKArjOQp^IiB]liBY TURNER, M.Sc, Member,
M „„_......................■ - ■ 323
J. DUDLEY JEVONS, B.Su. (Respectively Lecturer and Research Student in the Metalliroic,
Departme.nt of the University of Birmingham).
Many of the best-known metallurgists and engineers have applied themselves to the subject of strain in metals, directly or indirectly. Nevertheless, it is still impossible or extremely difficult to detect, by ordinary means, strain in a mild steel, unless the material has been drastically cold-worked and is severely strained. Slight permanent strain present in steels deformed but little cannot be recognised under the microscope by the ordinary worker. Few would be able to differentiate microscopically, or indeed by any other means, between two pieces of the same mild steel, the one stressed below and the other just above the elastic limit. Were such differentiation possible, information could be obtained of undoubted value to designers and users who are interested in the behaviour of new constructions, or in the cause of the failure of some steel part.
While employed in an engineering works, one of the present authors carried out the usual type of post-mortem investigations necessitated by the failure in service of various types of mechanisms. It was Iben thought ihat the location of strained area* in steels would be similar to the stress concentrations indicated by Coker (1) and his collaborators in their work with polarised light, and transparent bodies stressed within their elastic limits. It was felt, however, that it was not safe to go far in applying those results to the common metals and alloys, materials whose structures differed fundamentally from those of such transparent bodies.