a b s t r a c tInverse problems can be found in many areas of science and engineering and can be applied in different ways. Two examples can be cited: thermal properties estimation or heat flux function estimation in some engineering thermal process. Different techniques for the solution of inverse heat conduction problem (IHCP) can be found in literature. However, any inverse or optimization technique has a basic and common characteristic: the need to solve the direct problem solution several times. This characteristic is the cause of the great computational time consumed. In heat conduction problem, the time consumed is, usually, due to the use of numerical solutions of multidimensional models with refined mesh. In this case, if analytical solutions are available the computational time can be reduced drastically. This study presents the development and application of a 3D-transient analytical solution based on Green's function. The inverse problem is due to the thermal properties estimation of conductors. The method is based on experimental determination of thermal conductivity and diffusivity using partially heated surface method without heat flux transducer. Originally developed to use numerical solution, this technique can, using analytical solution, estimate thermal properties faster and with better accuracy.
Moving heat sources are present in numerous engineering problems as welding and machining processes, heat treatment, or biological heating. In all these cases, the heat input identification represents an important factor in the optimization of the process. The aim of this study is to investigate the heat flux delivered to a workpiece during a micromilling process. The temperature measurements were obtained using a thermocouple at an accessible region of the workpiece surface while micromilling a small channel. The analytical solution is calculated from a 3D transient heat conduction model with a moving heat source, called direct problem. The estimation of the moving heat source uses the Transfer Function Based on Green's Function Method. This method is based on Green's function and the equivalence between thermal and dynamic systems. The technique is simple without iterative processes and extremely fast. From the temperature on accessible regions it is possible to estimate the heat flux by an inverse procedure of the Fast Fourier Transform. A test of micromilling of 6365 aluminium alloy was made and the heat delivered to the workpiece was estimated. The estimation of the heat without use of optimization technique is the great advantage of the technique proposed.
Nowadays, almost all cutting tools are coated due to improvements in manufacturing processes. The two main reasons are: (1) coatings allow a cut with less friction and less wear resulting in longer tool life and (2) thermal barrier effect, since the contact between workpiece-toolchip occurs in the coating and not in the tool material (substrate). This paper analyzes, the thermal effect of the coating without considering the tribological effect. The thermal behavior with three types of coating: cobalt (Co), titanium nitride (TiN), and aluminum oxide (Al 2 O 3) on a ISO K10 carbide insert of 3 mm thickness was investigated. This paper investigates the behavior of inserts with coatings of thickness of 1, 2, 5, 10, and 20 lm in a onedimensional transient thermal model proposed for a material composed of two layers. A constant heat flux simulates the heat generated in the tool-piece-chip interface for coated and non-coated inserts. The solution of the diffusion equation is obtained using the Green function method. The effect of the coating can then be calculated by analyzing the evolution of the temperature at the cutting interface in contact with the heat flux and the evolution of the temperature at the coating-substrate interface. It can be concluded that coatings have thermal barrier effect, although for coatings of 2 lm thickness, this influence is very small and produces temperature reduction of up to 14%. For thicknesses greater than 5lm, the effect becomes considerable depending on the coating-substrate pair. In the case of TiN carbide, the temperature reduction is 26, 34, and 41% for the thicknesses of 5, 10, and 20 lm, respectively.
Currently, polyurethane (PU) production is completely dependent upon fossil oil, as the two primary reagents necessary for PU production, polyol and isocyanate, are derived from fossil fuels. Eucalyptus branches are waste products for most forest management companies. In this work, polyols obtained by the liquefaction of eucalyptus branches were used for foam production. The influence of the isocyanate, catalyst, surfactant, and blowing agent contents on the foam properties was studied. Overall the amount of each chemical used in the production of PU foams had a noticeable effect on the density and compressive properties. The amount of water (blowing agent) had the strongest effect and decreased the density and compressive properties because of higher foam expansion. The other chemicals increased or decreased the density and compressive stress depending on the amount used. The density of the produced foams ranged from 36 kg/m3 to 108 kg/m3, the compressive stress ranged from 15 kPa to 149 kPa, and the Young’s modulus ranged from 64 kPa to 2100 kPa. The results showed that it is possible to convert these forest residues into PU foams with properties somewhat similar to those of commercial foams, although with a lower compressive strength.
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