Research On Numerical Simulation And Properties Of Hardened Layer Of Laser Surface Hardening Of Large Pitch Bearing

Development of wind power industry is one of the important energy strategies of our country.As a key component of wind turbine,large pitch bearing often suffers from wear and contact fatigue failure,which seriously affects the safety and reliability of the wind turbine equipment.As a new and efficient method to improve surface properties,laser surface hardening has been applied in engineering.Therefore,pitch bearing raceway needs to be strengthened by laser phase transformation.It is urgent to analyze the mechanism and process of laser surface treatment for large bearings,understand the characterization of hardened layer and its influencing factors,and then strengthening treatment of megawatt wind power bearing by laser surface treatment technology.In this paper,the numerical simulation,experiments and the effect of laser surface hardening for pitch bearings are studied,which provides theoretical and technical support for the application of laser surface hardening technology.The main research work is as follows:(1)The simplified specimens by reasonable method with the same material as the pitch bearing was proposed.The finite element model was established based on the key problems such as boundary conditions,heat source model and material parameters were solved.The numerical simulation of transient temperature field and thermal stress field of laser surface hardening has been completed.Based on the law of temperature field,the characterization and evaluation method of hardened layer depth was studied.(2)42CrMo steel specimens were prepared.Through orthogonal experimental design,several groups of laser surface hardening process experiments were carried out.By comparing the experimental hardening depth with the simulated hardening depth,the feasibility of finite element modeling and method was verified.To evaluate the effect of laser surface quenching,the surface roughness,metallographic structure and hardness of the quenched specimens were tested.(3)According to the design size,this paper established the raceway model of 2.2MW large propeller bearing.The raceway of laser quenching process was simulated and transient temperature field of laser surface hardening process has been calculated numerically.Researched on uniformity of hardened layer,the influence of different process parameters on hardening depth was analyzed.It provides a theoretical reference for the reasonable selection of process parameters.(4)According to engineering requirements,a Kriging approximate model of laser surface hardening process effect based on finite element method is proposed.Using uniform experimental design,a mathematical prediction model of hardening depth was established.Compared with the simulation results,the validity of the approximate model was illustrated,which can be used to replace the complex finite element calculation.On this basis,a simple software for engineers based on Matlab is developed.