Study On Mechanical Behavior Of Hollow Cylindrical Roller Bearings For

Cone bit is the major rock-breaking tool in petroleum drilling engineering, its life and working performance have a significant impact on the drilling quality, drilling efficiency and drilling cost. The bearing system is a key component of cone bit, its fast failure is the main reason for low cone bit’s life. The thesis comprehensively considered the effect of structural loads and thermal loads, used the basic theoretical knowledge such as finite element, contact mechanics, frictional wear and thermodynamics, etc, and combined with experimental study, started with analyzing working characteristics of rolling bearing system for cone bit, applyed simulation software ANSYS to compete the mechanical performance research of hollow cylindrical roller bearing for cone bit, and further discussed the influence rule of various key engineering parameters on contact performance and thermal-structure coupling field of the bearing. The main research work of this article can be summarized as follow:(1) Studied the operating characteristics, structural features, materials and technologies of rolling bearing for cone bit; analyzed the main failure modes of rock-bit’s rolling bearing, respectively for fracture failure, plastic deformation, wear, ablation and seal failure; studyed the force distribution of rolling brearing for cone bit, derived and calculated the axial load, radial load and cumferential torque during drilling of bearing system.(2) Based on the theory of hydrodynamic pressure and hertz contact, designed the pin-disk unit trial scheme to test friction and wear performance of rolling bearing for cone bit, researched the change rules of friction coefficient, temperature and wear loss under different working conditions, provided the necessary material performance parameters for the mechanical properties analysis of bearing.(3) Established the finite element model of rock-bit’s rolling bearing in software ANSYS according to finite element theory, and simulated mechanical properties of the model in different conditions, the results show that bit pressure and fit clearance have a relatively significant effect on the mechanical properties of the bearing, the effect of friction coefficient on static performance of the bearing is smaller, the influence of roller’s number and diameter on bearing performance has no obvious regularity.(4) To improve the the stress states of the main cylindrical rollers in rock-bit’s rolling bearing, maked the solid rollers into hollow rollers, and analyzed mechanical properties of hollow cylindrical roller bearing for cone bit by the finite element method. The results show that with the increase of hollowness, the equivalent stress peak of bearing parts, the contact stress peak of thrust surface and small journal surface in rock-bit’s rolling bearing present a trend of increase with the decrease of the first; they reach the minimum value when the hollowness is55%, while the contact stress peak of hollow roller decreases gradually; the influence laws of engineering parameters such as bit pressure, friction coefficient, roller’s number and diameter, fit clearance, etc on the hollow bearing are similar to the solid bearing; comparing with the ordinary hollow roller, the stress peak of conical concave-ened hollow roller with reasonable structure paramaters decreases, and the stress concentration at the end of roller is improved. (5) Studied heat output and convective heat transfer calculation model of the bearing, and analyzed temperature field and thermal-structure coupling field of rolling bearing for cone bit by using the finite element method, and also discussed the influence rules of engineering parameters such as hollowness, bit pressure, friction coefficient, revolving speed and well temperature, etc on thermal-structure coupling field of hollow bearing. The results show that the temperature rise is an important factor affecting mechanical properties of the bearing; comparing with the solid bearing, temperature peak, stress peak and displacement peak of hollow bearing parts decrease significantly.In this paper, the research results can give a theoretical basis for designing and optimizing the structure of rolling bearing for cone bit, and they have a certain reference value to improve the working life and reliability of rock-bit’s rolling bearing.