Thermomechanical Model For Helical Milling Titanium Alloy Based On Analysis Of Chip Shape

Titanium alloy plays an important role in the field of aerospace as a kind of structural material, of which high strength and low thermal conductivity lead to a series of problem such as high cutting force and cutting temperature. Helical milling is a novel method of machining materials difficult to cut such like titanium alloy, which has some advantages of eccentricity being changeable, low cutting force, well heat dispersion, and etc. Using specialized helical milling cutter can obtain much better performance than traditional end mill. It is of significance for describing the forming reason and relationship between cutting force and cutting temperature and optimizing the structure of the tool and machining parameters to build an thermomechanical model of helical milling titanium alloy relative to tool’s structure parameters and machining parameters.Firstly, the motive process of helical milling is simplified according to the feature of parameters used in the helical milling. Aiming at simplified chips’model, the relationships between the chips’geometric shapes produced by two kinds of cutting edges, which are W edge and S edge, and tool’s structure as well as machining parameters is built. Then, a double-cutting-edge oblique cutting model to calculate cutting forces caused by four cutting edges in any time is built. The chip produced during the cutting process is analyzed and the temperature field model containing the motive heat source of shear plane and friction zone on the rake face is built, which is used to calculate the temperatures on the shear plane, friction zone on the rake face and cutting edge. The cutting force model and the temperature model are combined to build a thermomechanical model, which considers the reciprocal action between cutting force and cutting temperature. The cutting force and cutting temperature of the cutting zone in the process of helical milling titanium alloy are measured through dynamometer and semi-artificial thermocouple method. The model is verified in an single-factor experiment, whose results show that the mean error of calculated values relative to measured ones is within 5%, which proves the model has considerable reliability. The relationships between cutting force as well as cutting temperature and machining precision as well as machining quality of helical milling titanium alloy are explored in an orthogonal experiment. Fianally, on the basis of precision and quality, the machining parameters and structure parameters are optimized througe the thermomechanical model.