No abstract

A data processing method for constitutive relation of large deformation rubber core in spherical blowout preventer is put forward in this article. Based on the Yeoh constitutive model and the large-deformation theory of rubber material, this article studied the constitutive relation of core material in blowout preventer. The constitutive relation experiments, the uniaxial tensile experiment, the uniaxial compression experiment, the plane tensile experiments, and the volume compression experiment were conducted and the corresponding experiment data were fitted, respectively, on basis of which the uniaxial compression data were selected for further study. For comparison, the data were, respectively, processed with a novel method and the method in GB/7757, and accordingly, two different constitutive relations were obtained and introduced into ABAQUS to simulate the experiment process. Research results show that the relative error of maximum axial deformation between the simulation using GB/7757 and the actual experiment is 34.7%, while that between the novel method and the actual experiment is 20.4%, having improved the accuracy by 14.3%, proving that the data processing method in this article can effectively improve the accuracy of finite element simulation for the core material and will contribute to the research on the performance of spherical blowout preventer.

In oil and gas drilling, the roller-cone bit and the hybrid bit configured with roller cones are two commonly used rock-breaking tools; however, service lives of the bits are limited by the sliding bearings therein. In order to improve the performance and reliability of the bearing in the roller cone, a novel bearing with a floating sleeve is researched in this paper. Firstly, motion characteristics of the bearing are researched, and motion relations between the elements in the bearing are analyzed, respectively. Then, on the basis of the motion relations, three motion statuses of the float sleeve are clarified, including the sleeve start to rotate, the sleeve rotates stably with the pushing force exerted by the rollers, and the sleeve rotates stably with the opposing force exerted by the rollers. At last, bearing performances in three different conditions are respectively tested in the experiment. The results, with the specific speed value being in the range of 0.375∼0.833 and the average value in 0.613∼0.618, show that the sleeves with 6∼12 rollers are able to start and rotate stably under 5 kN radial load, indicating that the sleeves can be started to rotate and work stably, whereas, for the sleeve with less than 4 rollers, the specific speed value varies in the large range of 0∼1.176, indicating that this sleeve cannot rotate stably in the bearing. This research revealed that the amount of rollers is an important factor that determines whether the sleeve is able to float stably in the bearing; therefore, roller quantity should be focused in the bearing design to optimize its performance.