PLASTICITY, FRACTURE AND FRICTION IN STEADY-STATE PLATE CUTTING

A closed form solution to the problem of steady-state wedge cutting th rough a ductile metal plate is presented. The considered problem is an idealization of a ship bottom raking process, i.e. a continuous cutti ng damage of a ship bottom by a hard knife-like rock in a grounding ev ent A new kinematic model is proposed for the strain and displacement fields and it is demonstrated that the analysis is greatly simplified if the strain field is assumed to be dominated by plastic shear strain s and moving hinge lines. Also. it is shown that the present shear mod el offers the basis for a convenient extension of the presented plate model to include more structural members as for example the stiffeners attached to a ship bottom plating. The fracture process is discussed and the model is formulated partly on the basis of the material fractu re toughness. The effect of friction and the reaction force perpendicu lar to the direction of motion is derived theoretically in a consisten t manner. The perpendicular reaction force is of paramount importance for predicting the structural damage of a ship hull because it governs the vertical ship motion and rock penetration which is strongly coupl ed with the horizontal resistance and thus with the damaged length. Th e derived expressions are discussed and compared with previously publi shed experimental results and formulas. (C) 1998 Elsevier Science Ltd. All rights reserved.