Flow Leading to Fracture.

Abstract : Activity on the project was sharply focused on the principal research objectives; to establish a theoretical basis for the forming limit diagram. Formidable algebraic difficulties impeded this effort and it was not until the end of the second year that the first satisfactory theoretical development was completed. This theory accounts for biaxial stretching which comprises the right half of the forming limit diagram, and accounts for the effects of strain rate sensitivity on material behavior. However, it cannot be applied to the left half of the diagram (longitudinal stretching with transverse contraction) in any direct way. So much work remains to be done in the basic theoretical formulation. Numerical results calculated on the basis of the above theory were not entirely satisfactory. This led to an examination of the material flow law being used and this law was shown to have certain fundamental defects. Reformulation of the flow law led to preparation of a manuscript entitled 'A Generalized Quadratic Flow Law for Sheet Metals'. Numerical results calculated on the basis of the above theory incorporating the reformulated flow law are quite satisfactory. They are being incorporated in a manuscript entitled 'Biaxial Stretching of a Flat Sheet'. (Author)