Experimental-Analytical Method for Temperature Determination in the Cutting Zone during Orthogonal Turning of GRADE 2 Titanium Alloy

The paper presents an experimental-analytical method for determination of temperature in the cutting zone during the orthogonal turning of GRADE 2 titanium alloy. A cutting insert with a complex rake geometry was used in the experiments. The experimental part of the method involved orthogonal turning tests during which the cutting forces and the chip forming process were recorded for two different insert rake faces. The analytical part used a relationship between the cutting forces and the temperature in the Primary Shear Zone (PSZ) and the Secondary Shear Zone (SSZ), which are described by the Johnson-Cook (J-C) constitutive model and the chip forming model according to the Oxley’s theory. The temperature in the PSZ and SSZ was determined by finding the minimum difference between the shear flow stress determined in the J-C model and the Oxley’s model. Finally, using the described method, the relationship between the temperature in the PSZ and SSZ and the rake face geometry was determined. In addition, the temperature in the cutting zone was measured during the experimental tests with the use of a thermovision camera. The temperature distribution results determined experimentally with a thermovision camera were compared with the results obtained with the described method.

Constitutive Modelling of Mechanical Behaviour of a Ti-Alloy, Applicable in Metal Cutting

In order to simulate manufacturing processes, it is essential to have accurate information about mechanical behaviour of material for different deformation conditions depending on the type of the process. In finite element (FE) analysis based techniques for simulation, a constitutive equation is needed to model the mechanical behaviour of material. In the case of metal cutting, the Johnson and Cook (JC) flow stress model is the most suitable constitutive equation to be used in simulation since it contains the effects of strain, strain-rate and temperature. It is needed to evaluate the parameters and constants of the JC model to make it applicable in FE simulations. There are several ways to evaluate the parameters of the equation: experimental such as high strain-rate compression tests called “Split Hopkinson Pressure Bar” which is relatively complicated and expensive technique requiring special testing apparatus; and analytical approach based on Oxley’s theory. An integral method containing quasi-static compression and machining tests have been used in this paper to evaluate the JC equation parameters by fitting data from both tests for a Ti-alloy (Ti6Al4V). Finally the estimated JC model is validated by some other machining tests.