Multiscale Modeling of the Thermomechanical Tool Load in Gear Hobbing

 

Starting Point

For the evaluation of the tool load and the wear behavior, uncut chip geometries are commonly used for gear hobbing. The disadvantage of the geometric approach is the insufficient description of the contact conditions between tool and workpiece. Workpiece and cutting material, cutting speed, cutting edge shape as well as the (effective) rake and clearance angles have no influence on the penetration conditions. Continuum methods such as the finite element analysis (FEA) have been established to take these variables into account. However, the advantages of the FEA are offset by high computation times, the need for validated material and contact models, and a high level of effort in model generation, which makes application-oriented use difficult.

Research Objective

The objective is to develop a multiscale model that combines the geometric penetration variables with the FEA. In FE simulations of the orthogonal cut, cutting speed, uncut chip thickness and rake angle are varied within a defined parameter space. As a result, functional relationships between thermomechanical load and state variables and the variation parameters are available. In the geometric penetration calculation, the hobbing process is simulated and the chip characteristics are determined for each generating position. By discretizing the tool profile, the uncut chip geometries are resolved locally for each point of the tool cutting edge. These serve as input variables for the load functions determined by means of FEA. The equations are solved at all points of the cutting edge for each generating position. The result is a multiscale model for describing the thermomechanical tool load in each generating position. The multiscale model is validated in the fly-cutting trial with respect to the resulting cutting force. The temperature simulated by means of the multiscale model is verified by an FE simulation of a full cutting engagement in one generating position.