Time and Feed Dependent Fracture of Cutting Tools — A Stochastic Model

Under given conditions, time and feed dependent fracture is the predominant failure mechanism of cutting tools. Assuming as a first approximation a decay in fracture resistance linear with cutting time, a model is developed which describes the overall variation in terms of variation in tool life (at constant feed) and fracture resistance (estimated from increasing feed tests). Validation of the model and quantitative evaluation of parameters are obtained from a set of cutting tests performed on a CNC lathe both at constant and variable feed rate. The effects on the model of single and combined variation of the main parameters are examined, and the main implications of the tradeoff between material removal rate and hazard function are discussed.