Servo-Control Applied to the Parameters of the Laser Hardening Process for a Regular Case Depth of 4340 Steel Cylindrical Specimen

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.