Abstract
Thermal properties of machined materials, which depend significantly on the change in cutting temperature, have a considerable effect on thermal machining characteristics. Therefore, the thermal properties used for the numerical simulation of the cutting process should be determined depending on the cutting temperature. To determine the thermal properties of the machined materials, a methodology and a software-implemented algorithm were developed for their calculation. This methodology is based on analytical models for the determination of tangential stress in the primary cutting zone. Based on this stress and experimentally or analytically determined cutting temperatures, thermal properties of the machined material were calculated, namely the coefficient of the heat capacity as well as the coefficient of thermal conductivity. Three variants were provided for determining the tangential stress: based on the yield stress calculated using the Johnson-Cook constitutive equation, based on the experimentally determined cutting and thrust forces as well as by directly calculating the tangential stress. The thermal properties were determined using the example of three different materials: AISI 1045 and AISI 4140 steel as well as Ti10V2Fe3Al titanium alloy (Ti-1023). With the developed FE cutting model, the deviation between experimental and simulated temperature values ranged from approx. 7.5 to 14.4%.
Highlights
Over the last decades, considerable improvements in modeling have turned numerical simulations of various machining processes, e.g. using the finite element method (FEM), into powerful tools for investigating machining characteristics, tool wear, physical-mechanical characteristics of workpiece boundary layers, etc. [1], [2], [3], [4]
The simulations were carried out with the values of the thermal material properties, established according to three variants: 1) due to the normal stress t calculated with the Johnson-Cook constitutive equation (JC), 2) based on the resultant forces FX and FZ determined by experiment (MF) and 3) through the direct calculation of tangential stress t (TS)
The simulation of heat flows in the modeling of cutting processes depends considerably on the thermal properties of the work materials
Summary
Considerable improvements in modeling have turned numerical simulations of various machining processes, e.g. using the finite element method (FEM), into powerful tools for investigating machining characteristics (mainly cutting forces and temperatures), tool wear, physical-mechanical characteristics of workpiece boundary layers, etc. [1], [2], [3], [4]. For establishing the thermal properties of the work material, which are necessary to simulate different cutting processes, it was suggested to determine by experiment the cutting temperature in the respective zones based on the analytical description of the stress-strain state of the material [36], [38] in the cutting zones Fig. 1 In this case, it was necessary to find out for which area or rather cutting zone the corresponding calculations and temperature measurements must be carried out. These were used further for establishing the desired thermal properties of the work material. C) Fig. 5: Temperature at the exterior surface of the chip
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