The Thickness Effect and Plastic Flow in Cracked Plates

Citation

Swedlow, Jerold Lindsay (1965) The Thickness Effect and Plastic Flow in Cracked Plates. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/0WVE-W364. https://resolver.caltech.edu/CaltechETD:etd-12122003-100109

Abstract

Over a range of plate thickness, it is well known that the fracture behavior of flat plates is substantially different from that predicted by classical fracture analyses. Finiteness of the plate thickness causes a variety of failure mechanisms to occur, and qualitative features of the associated stress and strain fields may be deduced. It is indicated that both the three-dimensional nature of the stress field and the plastic deformations will be needed for an accurate prediction of the thickness effect. As a contribution to the three-dimensional analysis, an appropriate elastic boundary value problem is given limited consideration. It is observed that the three in-plane stresses can be singular, in accord with the two-dimensional results, but the transverse components appear to be bounded at the crack tip. Equations which include plastic behavior are outlined, and a plane stress problem is solved using numerical methods. Comparison with analytical and experimental results is made and found to be satisfactory. One important result indicates that, compared to the elastic solution, the intensity of stress at the crack point decreases with load, while that for strain increases. The results do not include determination of a fracture stress, as this further step requires the development of an elastoplastic fracture criterion. Comments on this extension are included, together with other aspects of future work.

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