Key Engineering Materials Vol. 693

Abstract: Deepwater pipeline repairing machine (DPRM) is an appropriative equipment which is used to repair damaged deepwater oil and gas pipelines. With the development of deepwater oil and gas exploitation, inventions of such kinds of equipments are urgent priorities. Grinding technology is used in DPRM to remove pipeline anticorrosive coating. It is easy to cut the pipeline excessively when grinding pipeline anticorrosive coating for large orality of deepwater pipelines, which is not conducive to use mechanical connector to seal the pipeline. In order to settle this problem, the rotating compliant mechanism is designed and the grinding tool is steel wire brush. Based on the theory of boundary layer, the underwater rotating mechanical model of grinding tools is established to gain the relationship between grinding drag torque and grinding tool radius, rotational speed, and positive pressure. The grinding experiment gives the effect of structural parameters of steel wire brush on removing anticorrosive coating and indicates that medium density bowl type steel wire brush is the best choice. Finally, the grinding pipeline anticorrosive coating test is completed to verify the rationality of the design of grinding device. These studies provide technical basis for the development of deepwater multifunctional pipeline repair machinery.

Abstract: As an efficient heat conducting unit, micro heat pipe is widely used in high heat flux microelectronic chips, and thermal resistance is one of the factors that are crucial to its heat transfer capacity. Based on heat transfer theory, this paper established a theoretical model of total thermal resistance through analyzing the structure and heat transfer performance of circular heat pipe with trapezium-grooved wick, simplified the model and tested the micro heat pipe for its total thermal resistance performance by setting up a testing platform. The testing results show that when the micro heat pipe is in the optimal heat transfer state, its total thermal resistance well coincides with that from the established theoretical model. As for a micro heat pipe with trapezium-grooved wick, its total thermal resistance first decreases, then increases with heat transfer capability increment, and reaches the minimum when it is in the optimal state of heat transfer performance. That too much working fluid accumulates in evaporation section and the vapor velocity is rather low is the main cause for the greater thermal resistance when the pipe is in low heat transfer quantity, yet the greater total thermal resistance when the pipe is in high heat transfer quantity is mainly caused by the working fluid drying up in condensation section. The total thermal resistance is related to many factors, such as the thermal conductivity of tube-shell material, wall thickness, wick thickness, the number of the grooves, the lengths of condensation and evaporation sections, the diameter of vapor cavity etc.. Therefore, the structure parameters of a micro heat pipe with trapezium-grooved wick should be rationally designed according to specific conditions to ensure its heat transfer capacity and total thermal resistance to meet the requirements and be in the optimal state.

Abstract: Taking a vertical machining center as an example, thermal characteristics of the spindle system were researched by finite element simulation and experimental test. Firstly, temperature field and thermal deformation of the spindle system were simulated considering boundary conditions of the finite element model, such as heat sources, convective heat transfer coefficients and thermal contact resistances between joints. Accuracy of the simulation was verified compared with test. The results shows that key areas of temperature rise locate at spindle bearing; thermal deformation of Y and Z directions are large; thermal characteristics of the spindle system has little influence on other parts. Thermal characteristics of the spindle system were optimized by changing structures and sizes of the cooling passage located at the headstock, and effectiveness of the optimization was verified by finite element simulation. The research results provide guidance for thermal characteristic simulation and optimization of a machining center.

Abstract: This paper obtains the formula for calculating fuel dynamic viscosity based on the Barus formula and Eying formula from both macroscopic and microscopic perspectives, studies the mathematical model of fuel bulk modulus changing with temperature and pressure based on equation of state for gases and solids, and computes the fitting formula and correlation coefficients of dynamic viscosity and bulk modulus based on IFO 180 test data. The result indicates that the calculation models for fuel dynamic viscosity and bulk modulus are effective.

Abstract: The current cutting equipment and methods cannot meet the demand of offshore wind cut jacket. In order to solve this problem, we develop a new suit of offshore wind jacket intersecting line cutting equipment. In this paper, detailed structure and operating guide of the equipment have been presented. The characteristics and application range are also included. The new equipment is simple and practical.

Abstract: Vibration is a torsional vibration essentially, which will produce additional stresses in the shaft, and when the stress exceeds the allowable limit total the shaft parts will produce fatigue damage. The vibration analysis on the tripod sliding universal joint of ships is analyzed including modal analysis and response spectrum analysis. The analysis result shows that it need to increase the strength of the shell and the tripod in the future design to enhance the reliability, safety and work life of the tripod sliding universal joint.

Abstract: In order to get a reasonable and effective adaptable structure design solution, fuzzy comprehensive evaluation method was applied to evaluate various schemes synthetically which has adopted the method of data normalization of the grey correlation evaluation method in pre process. Through the integrated calculation, the result of evaluation can be obtained accurately and rapidly from the static and dynamic value of the structures. An example of column of vertical grinding machine improvement design was given to explain the process of evaluation in details. Result of evaluation indicates that this method performs well in operability and practicability and can be used in the practice of product design and development.

Abstract: To realize accurate prediction of disk cutter performance and determine the crucial parameters in the design process of TBM (Full face tunneling boring machine), a new performance forecasting method of the circular blade cutter is presented, which integrates the parameters of breaking rock such as rock, disc cutter and construction. Furthermore, the second derivation in the process of breaking rock is considered, a new comprehensive performance forecasting model of the circular blade cutter is established based on the Coulomb-Mohr failure criterion. On the basis, the existed performance forecasting models of disc cutter such as Liner Cutting and CSM, and the performance forecasting model of disc cutter presented this paper are analyzed and calculated, according to Colorado linear cutting experiment. The calculation results indicate the prediction accuracy of the performance forecasting model presented in this paper is greatly improved, comparing with the existed models (such as CSM, linear cutting). Finally, the influences of the parameters (rock, disc cutter and construction) are analyzed, which provides for the overall design of TBM cutter and construction with some scientific basis.

Abstract: Large nonlinear rotor-bearing system is an important structure in rotating machinery, such as NC machine. Due to the mass imbalance of the system, vibrations induced by centrifugal forces inevitably exist in rotating machinery. So, nonlinear dynamic response of a complex rotor-bearing system was dealt with in this paper. The system considered was modeled using the finite element method and has 124 DOFs (degrees of freedom). A linear reduction method was used and a reduced-order dynamic model of the system with two DOFs had been obtained. Harmonic balance method was applied to the reduced-order dynamic model of the system and an approximate analytical expression of the solution for nonlinear dynamic response of the system at steady state was derived. The analytical solution obtained from the reduced-order dynamic model of the system was compared with the numerical one obtained from the direct integration of the equations of motion of the original system.

Abstract: Charpy impact test is very sensitive to mechanical processing technologies and product defects. Charpy impact test can give quantitative test data and improve the product quality of advanced manufacturing industry and the safety of the application of new materials. The Charpy impact test machine has elastic deformation. The center of percussion is different from the designed center of strike and this difference can affect the vibration energy on the pendulum. In this article, by using the finite element analysis method, we simulate experimental processes having different distance to the center of percussion and obtain the numerical quantity related effects. In the end, we verify the accuracy of the finite element analysis by using different energy level impact test.