Numerical Simulation Of Wind Turbine Spindle Brake And Its Friction Pair Fatigue Life

Currently, energy crisis and environmental problems attracted widespread attention.Wind energy is a kind of clean and rich energy which is both promising alternative.Wind power is an important way of wind energy use.Spindle brake was used for wind turbine to shut it down completely,which is an important part of wind turbine nacelle.Spindle brake involves coupling between heat and stress,friction pair bears alternating warming and cooling,resulting in thermal cracking,which would affect the life of friction pair.The other components subject to the role of load changes,and the fatigue cracks of which will also lead to brake failure.Fatigue analysis is an important part of the spindle brake design.This paper focuses on numerical calculation and analysis of wind power spindle brake fatigue life under the actual conditions started.this paper use the ANSYS to establish a finite element model for friction pair,simulate the mechanical stress,thermal coupling process and fatigue life of friction pair,analyze the mechanical stress,contact stress,temperature,heat stress,fatigue life,fatigue damage and so on.Also stress of the overall structure of the brake and the fatigue life of main component have been analyzed.The main work and results were showed as follows:Firstly,physical model and finite element analysis model of friction pair was established for different braking conditions. The mechanical stress have been simulated and the friction contact state has also been analyzed.Results show that the maximum mechanical stress of brake disk occurs at the edge of connection hole at radial position of 0.33 m,and the maximum mechanical stress of friction plate occurs on the surface of first friction plate in the braking direction.Mechanical stress is greater in emergency braking than normal braking condition at the initial moment of braking.Contact stress values changed little in different braking conditions.Secondly,according to results of mechanical stress and friction contact state,the physical model of thermal analysis was simplified,and thermal conduction finite element model was established,comparative analysis shows that the thermal stress is the major factor of thermal fatigue damage,and high thermal stress occurs at a temperature gradient larger location.Thermal stress is much greater than mechanical stress,which is a major factor causing thermal fatigue damage.The results show that axial stress of brake disc is larger than tangential stress, and the value is superior.This is the direct cause of the thermal crack and expansion of it to surface.Axial stress lead to heat crack formation and crack tangential stress will cause the extension.Thirdly,Based on heat- stress analysis results,the brake disc thermal stresses in the tangential and axial direction have been analyzed,numerical simulation of the brake disc thermal fatigue cracks under different conditions of formation of the brake disc life and contacts section creep transition process have been done.Results show that radial fatigue shorter life appears at the edge of the outer diameter of the brake disc,and axial shorter life located at the bottom of friction surface;Fatigue life of emergency braking is much less than normal braking,and the surface roughness will lead to reduce of fatigue life;Creep strain rate of emergency braking conditions is higher than normal braking.Finally,A finite element model of the overall structure of the brake has been established, and numerical simulation of the fatigue life of mechanical stress distribution and the main bearing component of the overall structure have been done.The results show that the change of stress at work is the major factor of the fatigue for brake.When the brake is not working,structure is only affected by the bolt preload.When the brake is working,in addition to preload,the structure is affected by fluid pressure and friction.Stress variation regions cross-checked with areas prone to fatigue damage.This paper is the basic application for practical engineering,research can provide a technical basis for the wind turbine brake and friction material design and improve optimization.