1,721,043 research outputs found
Thermal conductivity of flat-pressed wood plastic composites at different temperature and filler content
No full textThe thermal conductivity of wood flour (WF) filled high density polyethylene composites (wood plastic composite, WPC) is investigated experimentally as a function of filler content and temperature. Samples are prepared by compression molding process of previously blended and extruded WPC pellets, up to 50% weight content of WF. The thermal conductivity is measured by the heat flow meter technique in a temperature range from 15°C to 80 °C. Experimental results show that the WPC thermal conductivity decreases with temperature and WF content, with the last effect due to the increase in porosity with the filler content, as confirmed by density measurements. Using the thermal conductivity of bare WF, the thermal conductivity of the wood material in WPC (WM) is estimated. This value successfully predicts the upper and lower bounds of the WPC thermal conductivity by means of the parallel and series conduction model of a multi-phase composite material
Strain hardening of carbon steel during wire drawing
No full textThe Avitzur's limit analysis for the calculation of the drawing force in a wire drawing process is used to study the real behaviour of a carbon steel in an industrial case. The linear hardening assumption, used by Avitzur only for the first step, is extended to the whole process and tested against experimental data. The result shows that the predictions resulting from this extension are in good agreement with the experimental results and are, as rule, conservative
Size-dependent distributions of particle velocity and temperature at impact in the cold-gas dynamic-spray process
No full textA mathematical model, which describes the particle velocity and temperature of impact in the cold-gasdynamic-spray process and accounts for varying drag and heat transfer coefficients, is developed andvalidated. Using the proposed model, the distributions of impact velocity and temperature as function ofparticle diameter are predicted and their dependence on process parameters, standoff distance and theparticular trajectory of the particle in the jet is analyzed. These distributions must be taken into accountif a correct description of the required impact conditions for successful deposition in cold-gas sprayingis to be understood and modelled
Shape of the melt pool produced by a moving Gaussian heat source
No full textA new dimensionless form of the solution to the problem of a Gaussian heat source in steady state on a semi-infinite solid is presented. Applying dimensional analysis, it is shown that dimensionless expressions of all characteristic values associated to an isotherm, as its maximum width or depth, are function only of the Rykalin number, Ry, and the dimensionless distribution parameter of the source, σ∗. Maps delimiting domains of Ry and σ∗ that give specific regimes of the solution are developed. Using these maps, it is possible to know a priori the regime expected for the solution without solving the equation. The proposed expressions can be useful to predict the behaviour of the weld width and depth as function of process parameters in a number of processes involving a Gaussian heat source. © 2021, International Institute of Welding
Case microstructure in induction surface hardening of steels: an overview
No full textThe microstructure and resultant mechanical properties of the hardened case produced in steels by induction surface hardening are discussed. The development of the final structure is followed throughout its characteristic evolutionary stages; its dependence on heating and cooling rate, maximum temperature of the treatment, composition, and initial microstructure is described in detail. Gradients of microstructure, composition, and hardness brought about by induction surface hardening inside the case are studied and explanations about their origin are proposed. The properties of the hardened case completely rely upon its microstructure, whose control is then a key factor for engineering applications
Evaluation of the Drilling Parameters Effects on Machinability of PM Materials Using ANOVA
No full textThe aim of this paper is the machinability analysis, in different drilling conditions, of sintered metals filled with a machinability enhancer. The cutting parameters involved in the study are: rotating velocity, feed rate and coating of the tool. To reduce the number of experimental tests required, a 2^(k-1) fractional design of experiment with three two-level factors and two replications for each run was employed. The experimental design was repeated for three sintered metals with different hardness or density. The obtained results show new insight into the machining mechanism of sintered material and into the influence of the cutting parameters on the machining forces
The Effect of Strain-Hardening on a 8% Carbon Steel: an Industrial Drawing Process
No full textSalerno, Ital
The Effect of Strain-Hardening on a 8% Carbon Steel: an Industrial Drawing Process
No full textSalerno, Ital
The Estimation of the Diameter Error in Bar Turning: a Comparison Among Three Cutting Force Models
No full textMachining accuracy is considerably affected by the deflection of the machine-tool-workpiece system under the action of the cutting force. A new model to estimate a bar diameter error due to the deflection of the tool, of the workpiece-holder and of the workpiece was defined by the authors, starting from a cutting force model. This work deals with a comparison among the bar diameter errors that are calculated by means of the developed model involving three different cutting force models. The considered cutting force models were the specific cutting resistance, the Kronenberg cutting force and the unified-generalised mechanics of the cutting force model developed by Armarego. The numerical results were compared with those obtained by experimental tests carried out through a parallel lathe. The results show that the Armarego's cutting force model provides values of the force components and, therefore, the values of the resulting bar diameter errors are closest to the experimental ones
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