Failure Mechanism Analysis On Water-cooling Disc Brake Of Offshore Drilling Drawworks

The disc brake is one core component in the ocean drilling equipments. The practical resultsshow that the crack or fracture induced by thermal fatigue is the main failure mode of thebrake. Therefore, to carry out the failure mechanism research of the disc brake has a veryimportant significance in safeguarding the safety of drilling workers and equipments.Aiming at a water-cooling disc brake of offshore drilling drawworks, the thermo-mechanicalcoupling characteristics of the water-cooling disc brake were simulated by the method FEM.Based on the above results, the formation mechanism of thermal fatigue cracks of the brakedisc was analyzed. The main research and innovation work include:(1) The basic theory used in this thesis was elaborated, including friction heat theory,thermal conduction theory, and thermo-mechanical coupling analysis theory. The finiteelement solution method of heat transfer and the finite element description of temperaturefield and stress field under thermo-mechanical coupling conditions were also given in thethesis.(2) Thermo-mechanical coupling theoretical analysis model of the brake system wasestablished according to the structural features of water-cooling disc brake, then the initialand boundary conditions of thermal analysis were determined. Three dimension modelingsoftware Pro/E was used to build the real dimension brake disc system. The softwareHypermesh was applied to mesh the brake system. And the FEA software ABAQUS wasadopted to build up the thermo-mechanical coupling model.(3) According to the characteristics of emergency braking and repeated braking, thetwo braking conditions were simulated respectively by using software ABAQUS, and thedistribution characteristics and variation disciplinarian of temperature field and stress fieldof the brake disc were obtained. The factors of temperature field and stress field werediscussed through changing the working parameters and material parameters, etc.(4) Based on the results of thermo-mechanical coupling analysis during braking, thefailure mechanism of water-cooling brake disc was analyzed. Then dangerous parts and loadspectrum of the brake disc were determined. Thermal fatigue life prediction model of thedisc was established by the local stress and strain law. The thermal fatigue life of the brakedisc and its factors in different braking forms were also analyzed.The research showed that temperature field and stress field during braking were coupled. The higher specific heat, thermal conductivity and the lower thermal expansioncoefficient, elasticity modulus could help decrease the maximum values of the temperatureand stress of the brake disc. The greater the rate of cooling water was, the more obvious thecooling effect of the brake disc was, but when the rate of cooling water reached a certainvalue, and the cooling effect was unobvious. In the three-dimensional stress, circumferentialstress was the main reason for causing the initial cracks on the surface of brake disc. Thevelocity of round trip was a major factor in influencing thermal fatigue life of the brake disc.