No abstract

This study displays the effect of laser surface hardening parameters on the hardness profile (case depth) of a splined shaft made of AISI 4340 steel. The approach is mainly based on experimental tests wherein the hardness profile of laser hardened splines is acquired using micro-hardness measurements. These results are then evaluated with statistical analysis (ANOVA) to determine the principal effect and the contributions of each parameter in the laser hardening process. Using empirical correlations, the case depth of splined shaft at tip and root of spline’s teeth is also estimated and verified with measured data. The obtained results were then used to study the sensitivity of the measured case depths according to the evolution of laser process parameters and geometrical factors. The feasibility and efficiency of the proposed approach lead to a reliable statistical model in which the hardness profile of the spline is estimated with respect to its specific geometry.

No abstract

No abstract

This paper presents a numerical model able to control the temperature distribution along a 4340 steel cylinder heat-treated with laser. The numerical model developed using the numerical finite element method (FEM) was based on a study of surface temperature variation and the adjustment of this temperature by a control of the heat treatment laser power. The proposed analytical approach was built gradually by (i) the development of a numerical model of laser heat treatment of the cylindrical workpiece, (ii) an analysis of the results of simulations and experimental tests, (iii) development of a laser power adjustment approach, and (iv) proposal of a laser power control predictor using neural networks. This approach was made possible by highlighting the influence of the fixed (nonvariable) parameters of the laser heat treatment on the case depth and has shown that it is possible by controlling the laser parameters to homogenize the distribution of the maximum temperature reached on the surface for a uniform case depth. The feasibility and effectiveness of the proposed approach lead to a reliable and accurate model able to guarantee a uniform surface temperature and a regular case depth for a cylindrical workpiece of a length of 50 mm and with a diameter of between 16 and 22 mm.

This paper presents a numerical model able to control the temperature distribution along a 4340 steel cylinder heat-treated with Nd: YAG laser. The numerical model developed using the numerical finite element method, was based on a study of surface temperature variation and the adjustment of this temperature by a control of the heat treatment laser power. The proposed analytical approach was built gradually by (i) the development of a numerical model of laser heat treatment of the cylindrical workpiece, (ii) an analysis of the results of simulations and experimental tests, (iii) development of a laser power adjustment approach, and (iv) proposal of a laser power control predictor using neural networks. This approach was made possible by highlighting the influence of the fixed (non-variable) parameters of the laser heat treatment on the case depth, and has shown that it is possible by controlling the laser parameters to homogenize the distribution of the maximum temperature reached on the surface for a uniform case depth. The feasibility and effectiveness of the proposed approach leads to a reliable and accurate model able to guarantee a uniform surface temperature and a regular case depth for a cylindrical workpiece of a length of 50-mm and with a diameter of between 16-mm and 22-mm.

This paper presents a numerical and experimental analysis study of the temperature distribution in a cylindrical specimen heat treated by laser and quenched in ambient temperature. The cylinder studied is made of AISI-4340 steel and has a diameter of 14.5-mm and a length of 50-mm. The temperature distribution is discretized by using a three-dimensional numerical finite difference method. The temperature gradient of the transformation of the microstructure is generated by a laser source Nd-YAG 3.0-kW manipulated using a robotic arm programmed to control the movements of the laser source in space and in time. The experimental measurement of surface temperature and air temperature in the vicinity of the specimen allows us to determine the values of the absorption coefficient and the coefficient of heat transfer by convection, which are essential data for a precise numerical prediction of the case depth. Despite an unsteady dynamic regime at the level of convective and radiation heat losses, the analysis of the averaged results of the temperature sensors shows a consistency with the results of microhardness measurements. The feasibility and effectiveness of the proposed approach lead to an accurate and reliable mathematical model able to predict the temperature distribution in a cylindrical workpiece heat treated by laser.

This paper presents an analytical model able to explore the design method of natural smoke evacuation through an exhaust vent subject to wind pressure. The proposed model can be used to determine the flow rate of smoke and the optimal section of the exhaust vent according to the geometric parameters of the room, the heat release rate and the pressure exerted by the wind forces at the exhaust vent. The numerical resolutions of the mathematical equations of the model were performed using the dichotomy method. The proposed analytical approach is built progressively by, (i) the examination of interaction forces between buoyancy forces and wind pressure forces, (ii) a numerical validation of the analytical model using the numerical simulation software Fire Dynamics Simulator, and (iii) proposal of a method of approximation of the optimal section of the exhaust vent for a maximum smoke evacuation rate. The results show very satisfactory and provide adequate prediction of the optimal size of the exhaust vent between the theoretical approximation and various configurations of numerical simulation. The feasibility and effectiveness of the proposed approach lead to an accurate and reliable analytical model able to analyze the influence of the size of natural smoke evacuation vents subjected to the pressure of wind forces.