| The laser quenching process can form a hardened layer on the rail,which can improve the hardness and wear resistance of surface materials and prolong the service life of the rail.These can effectively prevent railway safety accidents.The morphology of hardened layer is closely related to the temperature distribution of the material.In order to assure the quality of quenching,this paper takes the material temperature during laser quenching of rail as the research object.With the help of classical control theory and finite element method,the temperature control technology for laser quenching was deeply studied by MATLAB and ANSYS software.In the meantime,the temperature control system was developed.The main research contents and results of this paper are as follows:1)Completed the design of temperature control scheme.A temperature control scheme is designed to adjust the laser power according to the material temperature feedback in the processing area;Different infrared temperature measurement methods are compared and analyzed.And a temperature measurement scheme based on colorimetric temperature measurement is determined;Hardware selection of temperature measurement module and control module is carried out to meet the requirements of temperature feedback and power regulation.2)In order to realize high-performance temperature control in laser quenching process,finite element software was used to study the relationship between them.Through three-dimensional modeling,gridding model,boundary condition establishment,cyclic loading and other operations,the temperature distribution of rail material during laser quenching is obtained;The morphology of hardened layer was analyzed according to the temperature distribution of finite element model.The results are consistent with the actual quenching,which verifies the validity of finite element analysis;The relationship between the thickness of hardened layer,laser scanning speed and material indication temperature was studied to provide guidance for the selection of process parameters in actual operation.3)In order to obtain good tracking performance,a temperature control algorithm combining internal model control with disturbance observer is designed.A temperature system is established with laser power as input and the temperature of the material in the spot area as output.The transfer function of the system is derived from the temperature response curve obtained by finite element analysis.Based on these,an internal model controller and an interference observer are designed.The use of internal model controller makes the control system have better dynamic response and robustness;The introduction of interference observer improves the anti-interference ability of the control system;MATLAB/SIMULINK and ANSYS software are used for simulation analysis to verify the effectiveness of the proposed control strategy.4)In order to verify the feasibility and efficiency of the control scheme in this paper,a temperature control system is built and experiments are carried out.Firstly,the hardware integration and software development of the control system are completed.Then,the quenching temperature control experiment of rail was carried out.The practicability and high efficiency of the temperature control algorithm are verified.Finally,the quenching quality of rail under constant temperature mode and constant power mode is compared and studied.It is found that the thickness of the hardened layer obtained in the constant temperature mode is more uniform.The experimental results show that the temperature control system developed in this paper can effectively control the material temperature during quenching.Compared with the constant power processing mode,the rail material temperature in the constant temperature mode is more stable in the quenching process.And the thickness of the processed hardened layer is more uniform.It is proved that the introduction of temperature control system can ensure the quality of rail laser quenching. |
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