Applied Mechanics and Materials Vols. 157-158

Abstract: At present, as the increasing of ultra-large structures, the contradiction that domestic lifting equipments can not meet the requirement of ultra-large structure’s lifting has become increasingly prominent. Based on the need of ultra-large steel structures (offshore oil platforms) jack-up, using strength theory and finite element analysis, a hydraulic continuous jack-up system for ultra-large structures’ jack-up was studied in this article. A new control system, which combines mechanics, hydraulics and electrics, was presented. More particularly, the modules of speed control and multi-cylinder synchronous control for the ultra-large structure’s lifting was designed. In the WINCC environment, a human-computer interface (control software) was developed by VB to achieve the system's real time monitoring and synchronization control. All movements of the jack-up system could be controlled through the software. To conclude, the jack-up system consists of two parts: the mechanical support structures and the control system. The former can assure great height (10m or more) jack-up, and the later can accomplish multi-point (more than 4 points) synchronous jack-up.

Abstract: This paper presents a calibration system by video processing technique. The system can calibrate large number of different types of dial instruments. The system is composed of an automatic recog-nition approach and a half-automatic approach. Both the automatic calibration and half-automatic calibration include four steps: 1st, dial plane circle edge extraction and center identification; 2nd, pointer extraction; 3rd, scale start and end position identification; 4th, result reading. For half-automatic method, the 1st step and 3rd step are manually indentified. By experiments and practical application in industry, it proves that our calibration system is effective for more than hundreds of different types of dial instruments.

Abstract: Considering the coupling moving of shaft and pads, a theoretical model for calculating the complete dynamic coefficients (CDCs) of tilting-pad journal bearing (TPJB) is described in this paper. The model includes the influence of fluid film temperature. Based on this model, the effect of fluid film temperature on journal equilibrium position, pads inclinations, and complete dynamic coefficients is investigated for given load cases. The numerical results indicate that the effect of temperature is not neglected for the dynamic properties of TPJB. The solution will provide useful tool for precise prediction of dynamic behavior of the rotor systems supported by TPJB.

Abstract: The paper introduces the characters of coordinated control system which belongs to 2×350MW supercritical air cooling heating units in a power plant. Meanwhile this article analyzes the control strategyies and the characters of main control circuits of boiler units and steam turbines respectively. The request of supercritical units running steadily and reacting quickly is satisfied by employing the technique of static feed-forward and so on.

Abstract: The compression behavior of closed cell aluminum foams with different density has been examined. Stress-strain curves were obtained. The microstructure evaluation of cell walls was investigated using X-ray computer tomography. A series of images of internal microstructures were given, the structural deformation evolution was analyzed. The images of cell wall evolution shown that crack appeared in cell wall after a small deformation of elastic deformation. As the compression proceeded, further cracks occur and some of the cell walls fracture. The fracture area become expanded, a part of dislocation on the sample side is formed. As the fracture area spreads, some regions become dense. The stress-strain curves showed brittle characteristics. As the relative density increases, yield strength and elastic modulus of aluminum foams increased. The best fit lines are obtained, where, is 0.97 and 0.2 respectively.

Abstract: Waterjet propulsion system have been increasingly used in the world due to its advantage of good maneuverability, operability, less vibration etc. The full understanding of waterjet reaction thrust is the preliminary step for the design of waterjet system. A recent research in this area is optimizing the nozzle structure of waterjet propulsion system to increase the waterjet reaction thrust as much as possible. In order to obtain the optimal parameters of nozzle, a new integrated method combining genetic algorithm with CFD simulation analysis is put forward in this paper. The integrated method will not only shorten the system design cycle, it will also develop optimization technique to realize the potential of computer based design automation. Finally, the optimal results are presented and discuss.

Abstract: Based on the vehicle air braking system circuit analysis, a pressure characteristics model in the states of normalcy and leakage was built, and the relationship between brake pressure characteristics and leakage was studied. Based on the modeling and study, simulation was done using the MATLAB; On the other hand, experimental setup of vehicle air braking system was designed, and the experiments were carried. Then the simulation results were compared with experimental results. By comparison and analysis, we come to a conclusion that the model in this paper can accurately describe the pressure characteristics of vehicle air braking system.

Abstract: In this paper, The finite element analysis software is applied to compute the flow field in the fixed orifice with different structural parameter combinations, the pressure distribution curve, the velocity distribution curve, flow rate characteristic, power loss are obtained. By analyzing simulation results, the influence of the orifice parameters on the performance of the orifice is clear. The research is important for the design and optimization of the fixed throttle orifice of the nozzle-flapper valve.

Abstract: The controller that used to follow the change of load for the single free-piston engine generator is presented here. It aims to achieve the stable operation with the piston oscillation. Based the energy balance equation in consecutive cycles, the kinetic energy of the free piston was described by discrete state functions. According to its error varying with minimums, the following controller was established to set the fuel injection. It was applied into the performance simulation. The results indicate that the controller is available. Due to the discrete characteristic of the energy transfer, the restoration progress has to require two or three cycles at least. And the stroke is increased with the load stepped up. The top dead center position has smaller changes than the bottom dead center. The displacement versus velocity limit loop is bigger than before. It will be used in the prototype design in the experimental research.

Abstract: Firstly, the creep curves of mica-quartzose schist are obtained through the triaxial creep test, the triaxial creep characteristics are found out by analyzing the creep curves. Secondly, a linear viscoelastic model is established by using model theory, a viscoplastic model is established by using empirical formula, added the above two model, a non–linear viscous elastic-plastic creep model of mica-quartzose schist is obtained. Lastly, the creep model parameters are got by data fitting, the good consistency of the test curves and the theoretical curves show the right and reasonable of the creep model. The non–linear viscous elastic-plastic creep model established can well describe the accelerated creep of mica-quartzose schist.