13th International Conference on Fracture June 16–21, 2013, Beijing, China -2- cutting zone. A finite element (FEM) thermal analysis program (NASTRAM software) was developed and reported here, utilizing a moving heating source model [5-6]. In that model, the grinding zone is assumed as a band source of heat that moves along the upper surface of the workpiece. The heat to the Workpiece in dry grinding was calibrated by matching between experimental data using an embedded thermocouples and FEM analysis temperature response. The FEM is used for extrapolation the temperature data from the measured points to the cutting zone. 2. Data acquisition system The data acquisition system consists of controller, amplifier, A/D convertor, and LabVIEW (Laboratory Virtual Instruments Engineering Workbench) for windows software developed by National Instruments. Once the program runs, thermocouples’ temperature and normal grinding force were collected and recorded on an Excel file. Figure 1. Schematic representation of Data acquisition system 3. Calibration experiment versus finite elements model The thermal analysis model utilizes parameters from the literature (specific heat capacity, Thermal conductivity and Density).The objective of calibration experiment is to verify the model and calibrate the parameters by matching the results with measurements. A solder-iron served as a heat source. It was placed at the center of the plate (x=0;y=39mm). An equally-spaced array of four thermocouples was placed in the upper surface and another two thermocouples – on the lower surface (Figure 4). The temperature at each thermocouple was measured after they reached a steady-state, 450 seconds after the initiation of the heat source (Figure 9). Plots of y-cut temperature distribution at each thermocouple’s position were calculated by the model (Figure 6). The ratio of the values at the peaks (locations of the thermocouples) matched the ratio of the measured values at the respective thermocouples. Values of (h) were then iterated in the model to reach a match with the measurements for -4 2 0 2.0 10 final W h mm C ⎡ ⎤ = ⋅ ⎢ ⋅ ⎥ ⎣ ⎦ . This is exhibited in Figure 6. The temperature evolution with time (as measured and displayed Figure 8) was then compared with a time evolution run of the model (Figure 9), which shows a good match. It is then easy to estimate the heat transfer coefficient (h) after calibrating the finite elements model, for every combination of tool cut and raw material.
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