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 strai ns and moving hinge lines. Also, it is shown that the present shear mo del offers the basis for a convenient extension of the presented plate model to include more structural members as for example the stiffener s attached to a ship bottom plating. The fracture process is discussed and the model is formulated partly on the basis of the material fract ure toughness. The effect of friction and the reaction force perpendic ular to the direction of motion is derived theoretically in a consiste nt manner. The perpendicular reaction force is of paramount importance for predicting the structural damage of a ship hull because it govern s the vertical ship motion and rock penetration which is strongly coup led with the horizontal resistance and thus with the damaged length. T he derived expressions are discussed and compared with previously publ ished experimental results and formulas. (C) 1997 Elsevier Science Ltd .