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Three-cone bit is the key equipment in the exploration of the oil in offshore drilling and exploration, the bearing system and the seal system are the critical components for the bit. Especially in the offshore drilling environment, the seal design need to be carefully considered. A multi-objective optimization design including orthogonal design method and F-test with finite element analysis for a three-cone bit seal is proposed. Firstly, the calculation method of optimization targets are given, including the minimization of maximum contact pressure and leakage rate analyzed by ANSYS and MATLAB respectively, to maximize seal life and reliability. Then, an orthogonal experiment approach is used to investigate the effects of the eleven parameters on the seal performance, and the influence degrees of the seal factors on the optimization targets have been confirmed by F-test, and the reasonable factors can be determined by the trend of the targets. Finally, in order to validate the analysis results, a new seal was designed and tested on a seal tester compared to the previous seal. In this test, the seal maximum interface temperature that reflects the position of maximum contact pressure can be obtained by using three high precision thermocouples. Both the experiment results and the numerical analyses proved that the maximum contact pressure and leakage rate of the improved seal have been reduced compared to the previous.

In this paper, a closed-form frequency equation of the pipe-in-pipe (PIP) structure with arbitrary boundaries is obtained. The frequency equation is derived from Green's function of the transverse forced vibration of the PIP structure and takes into account the effects of internal two-phase flow and axial pressure. The reliability of the method in this paper is proved by comparison with the published literature. In the numerical discussion part, the PIP structures with clamped-clamped, clamped-free, and elastic boundary conditions are used as examples to discuss. The effects of equivalent stiffness coefficient, internal flow velocity, and gas volume fraction on the stability of PIP structure are studied. The results show that the stability of the PIP structure is better than that of the single-pipe structure, and the greater the equivalent stiffness coefficient of the elastic layer, the higher the critical flow velocity of the structure. In addition, a modal conversion phenomenon existing in the PIP structure is discovered. There are different forms of modal conversion for different boundary conditions, and the modal conversion makes the order of instability of the PIP structure different from that of a single-pipe. The conclusion of this paper has positive significance for the dynamic research of PIP structure. [ABSTRACT FROM AUTHOR]

In harsh drilling conditions (e.g. abrasive drilling fluid), turbo-drill thrust ball may suffer from raceway surface indentation under the high axial load. The indentation can cause early failure of the bearing components. This paper establishes a micro-scale finite element model (FEM) to discuss the raceway surface indentation resulted from solid particle. For the sake of simplicity, the interaction between steel ball and solid particle as the latter is pressed into the raceway surface was depicted by axial and circumferential displacements. The distribution of stress and strain in solid particle and raceway surface was obtained from the finite element analysis. Through the discussion on solid particle ellipticity and the effect of friction coefficient on indentation features, it is learned that the variation in ellipticity has a slight impact on indentation depth, but a marked effect on raceway surface deformation; the friction coefficient has a significant impact on indentation edge shape and bottom centre of indentation. The simulation results provide a valuable reference for prevention of bearing raceway indentation. [ABSTRACT FROM AUTHOR]

A new fluorescent supramolecular self-assembly gelator (1) based on naphthalimide derivative with a tetrazole group was designed and synthesized, which could form a stable gel in acetone/H2O (1/1, v/v). The self-assembly process of gelator 1 was studied through SEM, UV-Vis absorption, fluorescence emission, XRD, and water contact angle. The microbelt structure was observed for the self-assembly system with its hydrophobic surface with the contacting angle of 143°. J-type aggregation mode was employed in the gel state, whose fluorescence emission showed a large red-shift of 153 nm compared with that for the solution state. This self-assembly system could selectively detect Cu2+ and K+, and their corresponding limit of detection was 5.65 × 10−7 M and 1.73 × 10−7 M, respectively. it's the fluorescence emission and color changed during the detection process of K+. This self-assembly was immune to acid although it has a tetrazole group. Interestingly, this self-assembly system could continuously respond to the organic amine and gaseous acid in three different states such as solution, gel, and xerogel. The limit of detection in the solution state for TEA and TFA was 7.66 × 10−5 M and 2.01 × 10−7 M, respectively. The limit of detection of the xerogel film towards TEA was 0.19 ppm. This research will provide a new way for the construction of multifunctional self-assembly systems for the detection of metal ions or organic amines and gaseous acids. [ABSTRACT FROM AUTHOR]