Modeling slice-push cutting forces of a sheet stack based on fracture mechanics

It is a well known phenomenon that cutting materials with a slicing motion is much easier than cutting by simply pushing the knife down into the material. Energy-based analyses proof that slice-push cutting reduces the overall cutting forces with an increasing slicing motion. In this investigation, a model describing the cutting of a thin and planar material with an asymmetrical knife is developed, using equilibrium of forces and basic concepts of fracture mechanics. Finite-element-simulations are performed to determine the relationship between cutting forces and the parameters describing crack propagation. Consequently, normal pressure on the crack surface caused by the flanks of the cutting edge of the blade is the main cause leading to a crack tip opening and thus propagation of the crack. Overall cutting forces are augmented by the friction forces caused by the relative motion between cutting knife and material. Thus, the slicing motion allows the advance force to be reduced. The presented model is experimentally verified by sideways cutting stacked paper sheets.