Advanced Materials Research Vols. 199-200

Abstract: The model based fault identification method was used to identify the two unbalance faults in two-span rotor system. The unbalance location and magnitude were identified using least squares fitting approach by the system’s transient residual vibration. The all-phasic FFT technique was used to analyze the original phases of vibration signals. The unbalance location and magnitude of the rotor system can be detected by using only a few sensors. Numerical simulations and experiment on rotor system with two unbalance faults were used, which proved the efficiency of the method.

Abstract: Considering the characteristics of Dimethyl ether(DME), such as low viscosity, strong dissolvability, swelling and ageing for usual rubber blankets, as well as mechanical property variation, some gum elastic parts could be corroded and lose their sealability. In order to avoid leak out of fuel feeding line and oil reserve tank, the taper face Hermetically-sealed construction was designed as the tube joint and the ether-resistance materials FM-1 was chosen as the sealant. And a gas impermeability experiment of joint was conducted to assess the tightness.

Abstract: In the process of computed order tracking, traditional method is based on the given analyzed order requirements, and also assumed that the highest order component is known. But in practice, the order component in signal is usually unknown. With regards to this issue, the paper proposed a method using filter to limit frequency and order. A principle on how to choose filter cut-off frequency and angular domain resampling order are deduced in this paper, then the relationship is analyzed between filter cut-off frequency and resampling frequency in time domain. Simulated signals are tried on the method, the results show that it can solve order aliasing problem successfully, and also effectively reduce resampling order.

Abstract: To more fully explore the effect of blade numbers on aerodynamic performance and noise of small axial flow fan, some solutions are adopted to obtain the parameters’ distribution of the flow field.Firstly, the standard k-ε turbulence model is used to calculate the steady flow field of six different fan blades(such as 5,7,9,11,13,15) , and the SIMPLE algorithm is applied to couple vecolity and pressure. Secondly, the large eddy simulation in conjunction with the FH-W noise model are used to compute the unsteady flow field and noise. Finally, the experimental results verify that the calculation methods of steady flow field and unsteady flow field are correct. The conclusions show: (1)Total pressure and efficiency generally maintain the trend of firstly increasing and then decreasing with increasing the blade numbers, and it is the greatest when fan blade number is 11. The flow rate coupled with the maximum efficiency has never changed with increasing the blade numbers. (2)With the increasing blades, overall sound pressure level of the aerodynamic noise is gradually decreasing near the outlet of fan tip, while it is firstly decreasing and then increasing before decreasing again 1 meter away from the central axis of the impeller along the outlet. When fan blade number is 11, overall sound pressure level of the aerodynamic noise is the greatest.

Abstract: Stress wave test technique has broad prospects because of the long distance, large scale and relatively low cost. This paper studies the stress wave propagation characteristics in the butt weld joints in the case of external symmetrical impact. The stress wave propagating before and after the joints is measured by dynamic strain gauge. Then model analysis and simulation is applied to research stress wave. The results show the loss of stress wave is small. After spectrum analysis, the change of propagating stress wave can be detected.

Abstract: Due to its compact sizing, fast response and good control performance traveling wave type rotary ultrasonic motor (TRUM) has significant potentials for applications in robot actuation. In order to considering the complex geometries, this paper presents modeling approach for micro-TRUM stator. First piezoelectric composite stator is partitioned into three substructures, two of which are modeled as several continuous annular plates by semi-analytical method. Without losing the complex geometries, the stator teeth as another substructure are modeled by means of finite element (FE) approach. Based on both component-mode synthesis and dynamic reduction, the coupled method for continuous plate and FE discretized teeth is presented in order to consider dynamic behavior of composite stator with good accuracy and short computation time. It allows combination of the continuous parameters and FE discretized substructures, and the mathematical model representing the complete stator is derived. Finally the prototype is manufactured according to the presented method. The validation of the analysis and design method is attained through the experiments for the manufactured stator. It is pointed that radial friction can be capable to increase s for the ultrasonic motor with smaller dimension. It explains why micro-TRUM has a fast heat output at the contact interface.

Abstract: This essay reveals that on the basis of fluid-structure interaction having appreciable impact on auto-vibration of gate structure, analysis and calculation on dynamic response characteristics of gate structural fluid-structure interaction have been conducted. The results indicate that under the same dynamic load the structural dynamic response value with fluid-structure interaction effect considered is remarkably larger than vibration response with fluid-structure interaction effect considering. The calculating results indicate that the largest response increase of typical parts of gate structure is from 50% to 60%. Therefore, as to making calculations on structural dynamic response with fluid-structure interaction effect, the impact flow field exerting on structural response should be taken into consideration.

Abstract: This paper presents a systematic research on the gear transmission system of the electric vehicle. An accurate 3-D model of the gear transmission system is established in UG (Unigraphics NX) using software Gearwizard, and then imported to ADAMS/View environment. Based on the contact force of ADAMS, the vibration at 3 different test points of the model are simulated. The simulation results seem to be in good accordance with the test results, which proved the validity of the gear transmission model. Finally, the influence of helix angle on vibration at 3 different test points are also researched. The results of the total analysis can be used further to optimize the gear transmission system of the electric vehicle.

Abstract: Two-degree-of-freedom vibro-impact model with clearance nonlinearity of torsional vibration is presented in this paper. Clearance in coupling in any rotating machinery can exhibit chaotic and multiple periodic phenomena. Coupling inertia also contributes to change the vibration characteristic significantly. In this paper, coupling effects, from a small inertia to large inertia compare to rotor, have been investigated for a wide frequency zone by simulation and some experiments focusing on resonance and bifurcation diagrams. As the spring in the clearance usually possesses quite low stiffness compared to shaft stiffness, symmetric and asymmetric characteristics can be exhibited. The results found are noticeably different from each other for the symmetric and asymmetric conditions. The presence of vibro-impact due to clearance can cause periodic, multiple periodic and chaotic motions.

Abstract: Vibration of the suspension system of a vehicle is crucial for comfort of the passenger. In this paper, a mathematical model of the suspension system is presented with half car model with four degrees of freedom. Vibration characteristics due to different pitch line excitation and different damping coefficients are investigated for heavy vehicle suspension system. The model is simulated in MATLAB SIMULINK for this investigation. ANSYS Structural software has also been used to determine the resonance frequency and mode shape of vehicle bounce and pitch motion.