Advanced Materials Research Vols. 139-141

Abstract: A three dimension model of some aircraft engine’s pipeline has been established to study dynamic characteristics of the pipeline under random excitation. The relationship between the supports’ parameters and the dynamic characters of the pipeline was also presented. In order to avoid the harmful resonance, depress the vibration level and reduce the dynamic stresses of the pipeline, a specific dynamical optimized method was proposed and the supports’ layout and parameters (location, quantity) were analyzed and optimized. The results show that 1) Under random excitation, the maximum stresses are located near the bushing with serious stress concentration and the ends of pipeline. Fracture failure easily occurs in these parts. 2) The supports’ optimized method of the pipeline proposed in this paper is reasonable and effective. And the optimized pipeline has less dynamic stress and better anti-vibration capability.

Abstract: Piezoelectric accelerometers are widely used for the measurement of middle- or high-frequency vibration. It is necessary to verify via experiments whether piezoelectric accelerometers can accurately measure low-frequency vibration. An experiment is designed to test the output characteristics of piezoelectric accelerometers for vibration of 1~5 Hz frequency, using a standard vibrator at low frequency (≤5Hz) and an accurately calibrated non-contact eddy current sensor as datum sensor. The experiment shows that the output characteristics of piezoelectric accelerometers are relatively stable when measuring vibration of 4~5Hz frequency. However, the output characteristics of accelerometers change with the frequencies and accelerations of vibration when the vibration frequencies are 1~3 Hz. It will affect the accuracy of vibration measurement.

Abstract: The precision of transferring paper is key factors to decide the print overprint accuracy, and vibration has an important impact on paper transferring accuracy. Empirical mode decomposition (EMD) can be used to extract the features of vibration test signal. According to the intrinsic mode function (IMF) by extracted, it is useful to analyze the dynamic characteristics of swing gripper arm on motion state. Due to the actual conditions of printing, the vibration signal of Paper-Transferring mechanism system is complex quasi periodic signals. Hilbert-Huang marginal spectrum that is based on empirical mode decomposition can solve the problem which is modals leakage by FFT calculated in frequency domain. Through the experimental research, the phase information of impact load at the moment of grippers opening or closing, which can be used for the optimization design of Paper-Transferring system and the improvement in the accuracy of swing gripper arm.

Abstract: The tip clearance flow of axial turbomachines is important for their aerodynamic and maneuver performance. And the tip clearance gap leakage flow is of continuing concern in reducing efficiency losses that occur within turbines. In order to gain significant reductions in emissions and specific fuel consumption as well as dramatic improvements in operating efficiency and increased service life of aero-engine, variation mechanism of blade tip clearance was analyzed and the equation of dynamic clearance was shown firstly, then the effect of rotor vibration in clearance variation which include flight loads and engine loads was studied in this paper; based on the dynamic measurements of blade tip clearance, a method that ensure tip clearance at optimal state in given mission profile through active rotor vibration control and active tip clearance control was presented. Besides, fuzzy control theory was used to solve the high nonlinear variation of tip clearance. The analysis result shows that this technique is useful.

Abstract: The shock response of single freedom system was studied based on impact theory. The shear blade of some merchant shearing machine was selected as the object. The static calibration and impact load testing was carried on the object. Based on the impact theory and finite element technology, the feasibility of the testing scheme and the influence of the shock wave shape on the testing accuracy were discussed. The results show that for the shear blade, when the impact load time history is 50ms and the natural frequency is 2848Hz, there only 0.42% difference between the maximum dynamic response and the static calibrated response. So it is practicable to use the static calibrated results to decide the relationship of the impact load and strain.

Abstract: In this paper, the main problem is how to eliminate vibration came from the compressor base in petrochemical industry. The absolute transmissibility was calculated by building the compressor isolation system model. The spectrum information of compressor vibration was got through the vibration test, and the results can be acted as the condition for the isolator’s design. Isolators were designed with damping part connecting metal rubber with helical spring. Nonlinear simulation calculation was completed by finite element software. The results show that the maximum stress of isolator is about 494MPa and its maximum distortion is approximately 6mm. It verifies that the new-style isolator can satisfy vibration elimination of compressor. It is with wide-range rigidity and better capability of energy dissipation than that of general rubber isolator. It has a useful application and perspective on vibration elimination for the mechanical equipment in petrochemical industry.

Abstract: The liquid switch gyroscope is used as a reference of the original horizontal coordinate system in the inertial navigation system of ballistic rockets. The stability of gyro is significant for finding ground level when a missile enters the destination region. A damping is adapted to increase the tremor convergence rate which may be caused by vibrations of generators, crustal movement and others. This paper proposed several experiments of the liquid electrolyte in the gyro horizon. The damping rate is variational with the bubbles. As a result of that, small tremor can be eliminated and the gyrohorizon can achieve steady mode rapidly.

Abstract: This paper investigates the selection method of vari-speed milling parameters by experiments. The orthogonal experiments of vari-speed milling were studied on a given speed according to the stability lobes, and various parameters were selected. The experimental results show that varying speed milling approach possesses effects on vibration suppression on proper parameters selection though the acceleration damping ratio γa and the sound damping ratio γs. The variance analysis of dual factors test is adopted to data process and the acceleration damping ratio γa is taken as the evaluation index of vibration suppression. Finally, the preliminary conclusions on how to select proper parameters are obtained on the basis of the analysis of the experimental results, which is applied to online monitoring techniques using vibration to achieve automatic control of variable speed cutting.

Abstract: A new control method for suppressing vibration in a rotating beam system of a helicopter has been presented. The method used a non-linear dynamics equation to compute actual natural frequencies using FFT, not based on nominal natural frequencies of linear dynamics. A design based on linear coupling may not take account of the effect of non-linear coupling in the system, so a conceptual controller design has also been presented, and a detailed control algorithm has been developed. In fact, this is a non-linear dynamics optimization problem. In a gyroscopic system, tuning of the flywheel allows a commensurable relationship to be established between the natural frequencies of the system, resulting in a strong coupling between the vibrating modes. Having established a strong coupling within the system, damping was introduced in the flywheel via an actuator, resulting in rapid vibration suppression. Numerical simulation demonstrated the efficiency of the modification.

Abstract: The radial equal-thickness feeder in the paper is designed for the rotary hearth furnace and achieves radial equal-thickness distributing for material. Vibratory feeder is a complex elastomer. Dynamic analysis is an important part for the large radial equal-thickness vibratory feeder. In order to attain the vibration characteristics of the basis and the screen body, such as amplitude, frequency, vibration locus, vibrating direction angle, and improve design quality, so the vibration feeder is tested and analyzed. Dynamic response parameters of large radial equal-thickness vibratory feeder are tested in field and the data in different time are collected by software DH5920. Material transportation speed and throughput are derived. The real average velocity is νmmax=0.054m/s, the real throughput is Q=3600hBνγ=25.19t/h. The results showed that the feeder can meet the production process requirements.