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In metal cutting processes the use of cutting fluids shows significant effects on workpiece surface quality by reducing thermomechanical loads on cutting tool and workpiece. Many efforts are made to model these thermomechanical processes, however without considering detailed heat transfer between cutting fluid, tool and workpiece. To account for heat transfer effects, a coupling approach is developed which combines CFD (Computational Fluid Dynamics) and FEM (Finite Element Method) chip formation simulation. Prior to the simulation, experimental investigations in orthogonal cutting in dry and wet cutting conditions with two different workpiece materials (AISI 1045 and DA 718) are conducted. To measure the tool temperature in dry as well as in wet cutting conditions, a two color pyrometer is placed inside a EDM drilled cutting tool hole. Besides tool temperature, the cutting force is recorded during the experiments and later used to calculate heat source terms for the CFD simulation. After the experiments, FEM chip formation simulations are performed and provide the chip forms for the CFD mesh generation. In general, CFD simulation and experiment are in reasonable agreement, as for each workpiece setup the measured temperature data is located between the simulation results from the two different tool geometries. Furthermore, numerical and experimental results both show a decrease of tool temperature in wet cutting conditions, however revealing a more significant cooling effect in a AISI 1045 workpiece setup. The results suggest that the placement of drilling holes has a major influence on the local tool temperature distribution, as the drilling hole equals a thermal resistance and hence leads to elevated temperatures at the tool front.

As additive manufacturing (AM) technologies utilizing metal powders continue to mature, the usage of AM parts in gas turbine engines will increase. Current metal AM technologies produce parts with substantial surface roughness that can only be removed from external surfaces and internal surfaces that are accessible for smoothing. Difficulties arise in making smooth the surfaces of small internal channels, which means the augmentation of pressure loss and heat transfer due to roughness must be accounted for in the design. As gas turbine manufacturers have only recently adopted metal AM technologies, much remains to be examined before the full impacts of applying AM to turbine parts are understood. Although discrete film cooling holes have been extensively studied for decades, this objective of this study was to understand how the roughness of film cooling holes made using AM can affect the overall cooling effectiveness. Coupons made from a high temperature nickel alloy with engine-scale film holes were tested in a rig designed to simulate engine relevant conditions. Two different hole sizes and two different build directions were examined at various blowing ratios. Results showed that the effectiveness is dependent on the build direction and the relative size of the hole. It was also discovered that commercially available AM processes could not reliably produce small holes with predictable behavior.Copyright © 2017 by ASME

This paper presents a μ – EDM melt-pool model to predict workpiece (anode) material removal from a single discharge μ – EDM process. To model the melt-pool heat transfer and fluid flow equations are solved in the domain containing dielectric and workpiece material. A level set method is used to identify solid and liquid fractions of the workpiece material when the material is molten by μ – EDM plasma heat flux. The plasma heat flux, plasma pressure and the radius of the plasma bubble have been estimated by a μ – EDM plasma model and serve as inputs to the melt-pool model to predict the volume of material removed from the surface of the workpiece. Experiments are carried out to study the effect of inter-electrode voltage and gap distance on the crater size. For inter-electrode voltage in the range of 100–150 V and gap distance of 0.5–2 μm, the model predicts crater diameter in the range of 150–165 μm and maximum crater depth of 25–35 μm for discharge duration of 5 μs. The crater sizes for most of experimental craters at higher gap distances show good agreement with the simulated crater shapes. However, at lower gaps, the model over-predicts the crater size.

Thermal design was incorporated into an undergraduate heat transfer course through a multistage design project. The students were tasked with designing water channels to be cut in an aluminum block using a wire electrical discharge machining (EDM) process. The students begin the process by analyzing the internal channels as a one dimensional array of fins using traditional analysis and correlations and Engineering Equation Solver (EES) to perform the calculations. Working in groups of two, the students conduct several parametric studies and develop a preliminary design using an array of fins method. The requirements for the design included outcomes that had to be met, along with weighting factors for key aspects of the design such as thermal performance, pressure drop, fabrication cost and volumetric flow rate. Next, the students analyze their preliminary design using SolidWorks flow simulation and compare their results to the one dimensional array of fins analysis. The groups then begin the process of refining their design using SolidWorks flow simulation to predict key parameters. Finally, the students select their best design which is fabricated using a wire EDM machine. The heat sinks are tested using a single experimental apparatus and the best design is determined based on the original requirements. The project is first introduced when the students are covering resistor networks and the analysis of an array of fins. The computational aspect of the project begins after the students have covered steady state conduction using finite difference methods. Using the computational results the students plot the heat transfer coefficient on the surface of the channel, which complements the lectures on internal developing flows.