Advanced Materials Research Vols. 503-504

Abstract: Vibration characteristics of a misaligned rotor with asymmetric shaft stiffness are studied. The system consists of two shafts connected by a flexible coupling with parallel misalignment, two rigid disks attached at the middle of each shaft and one of the shafts has asymmetric stiffness. The governing ordinary differential equations are derived using Lagrange dynamics and integrated through numerical methods. The effects of asymmetry, eccentricity and misalignment are studied through the peak-to-peak lateral vibration amplitude at different rotor speed. Simulation results show that the amplitude peaks at the natural frequency associated with unbalance and parallel misalignment, while half the natural frequency associated with the asymmetric shaft stiffness. This study may contribute to enrich understanding of the vibration of a rotor system under the cases of eccentricity, parallel misalignment and asymmetric shaft stiffness.

Abstract: The prestressing wires of prestressed concrete cylinder pipe (PCCP) provide pipe wall with compressive stress to resist internal pressure. Broken wires may cause yielding of steel cylinder and increase the risk of pipe failure with time. In order to reveal the mechanism of steel-cylinder yielding in PCCP with broken wires, a simplified model is developed and the maximum number of broken wires to preclude exceeding limit stress in steel cylinder can be determined conveniently by the equations derived in this paper. Verification analysis shows that the solution of simplified model agrees well with that of nonlinear finite element analysis. By comparing the calculated maximum number of broken wires with the detected actual number of broken wires, steel-cylinder yielding in prestress loss zone can be predicted, thus aiding condition assessment of PCCP

Abstract: To solve the problem of support speed of hydraulic support flipper, the match relations between the flipper throttle control and shearer cutting coal speed are analyzed, the AMESim simulation model of the throttle optimal control for hydraulic support flipper jack is established, the simulation results show that flipper can be supported timely by speed optimal control of flipper jack which improve the reliability of the system and provide certain theory basis to meet the miner safety and high efficiency production.

Abstract: General heat exchange efficiency is one of important economic indicators for the evaluation of the air washer. Based on the amount of test data analyzed by an orthogonal experiment method, this efficiency is mainly affected by the following factors in the air washer of the target-type nozzle namely air mass flow rate, water pressure, nozzle aperture, nozzle spacing, and obtains the optimal combination scheme of the four factors. Orthogonal test methods which had been verified by multiple regression equation has high reliability(R＞0.9)and good prediction for the level of significance of various factors.

Abstract: This paper gives the influences of the coarse aggregate size on the cracks of the beam with different aggregate sizes under static loads. The coarse aggregate sizes are ranked into three classes: small size (4.75mm ~ 19mm), big size (19mm ~ 37.5mm) and mixed size (4.75mm ~ 37.5mm). The developments of cracks of three reinforced concrete beams with the different of coarse aggregate sizes under the static loads are researched. The results show that under the action of the same loads, The reinforced concrete beams with the big aggregate size and mixed aggregate size have almost the same maximum crack width, while the maximum crack width of the beam with small aggregate size is less than formers. Using fractal theory, the fractal dimension of the cracks is studied. The result shows that the aggregate sizes have significant effect to the cracks on the reinforced beams.

Abstract: Based on performance driving design concept, sensor of high-precision balance is researched. Performance index system and performance model of sensor are established based on analytic design approach and finite element method, furthermore, the design process of structure of the sensor is proposed. The performance of the sensor has achieved integrated optimization, such as sensor linearity, counter electrode coupling displacement and range.

Abstract: To cope with the multi-physics fields simulation in MEMS device, based on PSPICE software, a multi-fields simulation model of capacitive micro-accelerometer is proposed, in which the mechanics, thermal and electric fields are included. Through the comparison of maximum step and pulse acceleration response under large displacement condition, which are obtained by simulation model and classic formula respectively, it is indicated that the difference between them is less than 3%. Furthermore, the comparison has been done with sensitivity test results in open loop mode. The comparison results show that the difference is less than 5% for large displacement situation and 3% for little displacement situation. Hence, the model could basically accomplish multi-physics fields simulation in MEMS device and be helpful in further research.

Abstract: To make clear the work mechanism of geosynthetic in asphalt overlay under the aircraft wheel loads, one 3D dimension finite element model was constructed on the basis of the general purpose finite element software ABAQUS. Numerical calculation results with different geosynthetic modulus are presented in this paper, and show that it is very limited for geosynthetic to reduce bottom stress and surface deformation of asphalt overlay, and asphalt overlay bottom is in compression state, thus, geosynthetic can not exert it’s film tension function, namely the main role of geosynthetic is not to bear loads together with asphalt overlay, but to improve stress state of asphalt overlay for preventing cracks appearance or delaying cracks expansion.

Abstract: Slotting is a good way to reduce the vibration and noise of circular saw blade. Optimization of slotting structure for low noise circular saw blades has become important in the recent designs. Altair_Optistruct provides an optimization toolkit to determine the most efficient load path for various constraints. This paper details the application of optimization techniques to reduce vibration and noise of circular saw blade with slots, the finite element model under the load conditions have been established in Hypermesh software, the vibration of peak ground displacement of modal for frequency response can be optimized to obtain maximum reduction, volume fraction range between 0.1 and 0.3 as constrained condition. The approach results have been successfully realized, and the optimization of slotting placement has been obtained.

Abstract: A research method of the deflection of throttle slice under the uniform distribution of variety load is presented. The analytical equation of slice deflection under the uniform distribution of variety load is deduced using the sheet mechanics according to the physical model of throttle slice, which is convenient for the theory analysis and engineering application. The correctness of equation is validated compared with finite element calculation results. The rules that different loads and the structure parameters and material characters of throttle slice influence on the deflection at any radius are studied. The analytical equation and conclusion offer reference to design throttle valve of shock absorber accurately.