| Currently, energy shortages have become increasingly prominent, wind energy as a green and Inexhaustible renewable energy catch attention around the world. Wind power is the main way to wind energy, the spindle brake is a major component of the braking system of the wind turbine and plays an irreplaceable role in the braking process. Brake of Spindle Brake involves mutual coupling between heat and force, under the action of friction, friction pair generated uneven temperature field, and uneven temperature field generated uneven stress field, in the repeated friction during braking, brake easily lead to thermal fatigue. For the finite element analysis of thermal coupling, with the development of computer simulation technology, model credibility problem also catch more and more attention.This paper focuses on friction pair of wind turbine spindle brake, using finite element analysis software ABAQUS builds finite element analysis model, in normal braking conditions and emergency braking conditions, this paper analyses distribution of the stress field and temperature field, and explores the cause of the brake disc cracks in an thermal stress of alternating cycle, on this basis, also analyses the fatigue life prediction. and this paper uses response surface method analyze model credibility assessment of friction pair of wind turbine spindle brake coupling thermal. Research method is also suitable friction heat coupling or other problems yaw brake disc brakes.The main work and results are showed as follows:Firstly, this paper builds geometric model and finite element model of friction pair, and comparatives analysis of the friction distribution trends of temperature and stress field under different conditions. The results showed that different conditions of temperature distribution is uneven and shows cyclic temperature zone, there is large temperature difference in the radial and axial, yet small in the circumferential, and the friction zone temperature is greater than the area of non-friction, there is the small changes in temperature at the inner diameter of the disc near; throughout the braking process, the brake disc temperature gradually decreased after increase, and temperature presents jagged changes; disc brake at the highest temperature is higher under emergency brake than normal, so in emergency braking the brake disc more susceptible to failure or even damage.Secondly, stress distribution is similar to temperature field in the brake disc, and presents cyclic stress zone, since the brake discs is alternative action of heat input and convective heat transfer, such that the stress versus time curves appear jagged, disc brake at maximum stress is greater than normal emergency braking conditions; three-stress components of maximum stress are analyzed and stress hoop stress is greater than the axial and radial stresses. Therefore, the circumferential stress is the major cause initiating disc brake crack, so the brake disk is easy to produce radial cracks.Thirdly,compare the difference between direct and indirect coupling method about coupling results, it is found that the distribution of temperature field and stress field is similar at two different coupling methods, but under the direct coupling method, the maximum temperature and the maximum stress are located in the brake disc friction region. in the actual project brake disc cracks also occurred in the area of friction, so a direct coupling method to solve the problem of thermal coupling is more in line with the real situation.Fourth, basing on thermal direct coupling analysis and combining with FE-SAFE software, using Manson-Coffin fatigue prediction model, taking into account the brake disc cyclic stress-strain curve, the minimum life of the brake disc is 4648 times, and it appear in the maximum stress of the brake disc at.Fifth, this paper selects the material thermal conductivity, specific heat capacity and density as independent variables of response surface model, uses central composite experimental design to obtain the sample point within the design parameter space. By applying significance test of design parameters and stepwise regression to obtain the response surface model, then verifying the accuracy of the response surface model to obtain the coefficient of determination R2 is 0.9647, the relative root mean square error is 0.0032, indicating that the response surface can accurately be replaced finite element model. Encoded form of proxy response surface model: y=299.68-17.96A+7.14B-19.18C-4.3 BC+4.18A2-10.67B2-20.01A2 B.Finally, this paper considers random variables obeying normal distribution, and use Monte Carlo random sampling method, on the basic, response surface model calculates and the response value is introduced into SPSS, then obtaining the mean response is 294.3 ?, compared with wind station frame 310? to get an error of 5.1%, less than Model credibility evaluation criteria 10%, so it can be determined wind power spindle brake thermal-mechanical coupling model is reliable to determine wind power spindle brake finite element simulation model can accurately reflect the process of wind power brake. |
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