Abstract: This study explores the effect of semi-active friction damping on vibration isolation systems by means of numerical simulation. Since the Lugre friction model can describe many phenomena observed in laboratories, it is chosen to provide accurate friction force model for the analysis and simulations. The drawback of the passive friction damping system is that it decreases the resonance response at the cost of worsening the performance for high frequencies. A semi-active control method (skyhook method) is used to tune the normal force so that the energy dissipated by the friction force is maximized. Such semi-active friction damping system is simple but efficient, and it can achieve result almost as good as that of active systems. Results from numerical simulations show that compared with passive system, semi-active control method decreases the response significantly for both low and high frequencies, with harmonic and random excitations.
Abstract: A new type viscous damper designed especially for the anti-impact requirements of piping systems on ship is studied．In order to analyze the operating characteristic of the damper in practical application，two experiments about the new type damper was carried out. One is on the drop test machine; the other is on a real ship. The results of the drop tests showed that the shock load was smoothly and gently brought to rest and decelerated with the lower possible force, which eliminates damaging force peaks and shock damage to machines and equipment. The real explosion experiment confirmed the good anti-impact ability of the new type damper．
Abstract: The tribological experiments of different metal frictional pairs were investigated by using MMU-5G friction and wear tester under oil-lubricating condition with serpentine powder additives. The upper and lower specimen pairs were 45 steel/45 steel, 45 steel/HT200 cast iron, HT200 cast iron/45 steel, HT200 cast iron/HT200 cast iron, respectively. Serpentine powder used as oil additive was characterized by transmission electron microscopy (TEM) and x-ray diffraction (XRD). Applying SEM and EDS, the surface morphologies of self-repairing coatings and their chemical compositions were detected. The test results revealed that self-repairing coating could be generated on 45 steel specimen surfaces. However, no obvious self-repairing coating formed on the worn surface in all tests which is mainly due to the unique microstructure of HT200 cast iron and the segregation effect of graphite.
Abstract: The generalized differential quadrature method (GDQM) developed recently is more and more widely used in structural analysis, but that is restricted by some conditions. The finite element method (FEM) is a conventional numerical method, but the calculational work is very great. In this paper, the GDQM and the FEM are combined together to analyze the transverse vibration of circular plates with an elastically mounted mass. The results show that this combination is a new way first proposed in this paper to solve the problems with complex domains in structural analysis. And it is a rapid, efficient, accurate and flexible numerical method with both the advantages of the GDQM and the FEM. Comparison with the existing literature has proved that the results obtained by this method are very accurate.
Abstract: To design a milling machine with high static stiffness and machining precision, the three-dimensional (3-D) model and the finite element model of a large-scale high-speed gantry type CNC milling machine have been established according to the demand of engineering. The main components of the milling machine have been studied separately by static and dynamic analysis to make an optimal structure design. The results indicate that the structure of the milling machine has great static stiffness, little structural deformation, and good dynamic characteristics. The method used in this paper provides helpful theoretical guidance to the dynamic design of milling machine.
Abstract: Based on the Maxwell equation and Kirchhoff assumption of thin plate, nonlinear magneto-elastic vibration equation, electrodynamics equation and electromagnetic force expressions of current-conducting thin plate were deduced. Furthermore, nonlinear super-harmonic resonance of thin beam-plate under lateral mechanical motive load in longitudinal magnetic field was studied. Considering the thin plate simply supported on two opposite sides, the magneto-elastic coupled vibration differential equations about function of displacement of vibration and electric field intensity were obtained by the method of Galerkin. Then, the amplitude-frequency response equation under super-harmonic resonance was derived by using method of Multiple scales. Correspondingly the stability of stable solution was analyzed. Through the numerical calculation, characteristic curves of amplitude changing with detuning parameter, the excitation amplitude and the magnetic intensity. At last, the influence of electric-magnetic and mechanic parameter on resonance phenomenon and stability of solution was analyzed.
Abstract: As the result of wheel-rail surface conditions, external environment and vehicle speed change, the state of adhesion is changing. In order to ensure the validity and security of high speed train in braking, and obtain the maximum utilization of adhesion, control system must provide a stable and effective braking force. This paper presents a new pressure model of brake cylinder, and a 90 DOF vehicle dynamic model, uses Oldrich Polach’s model to calculate adhesion force, and adds a track irregularity on vehicle model. Switch signal controls brake cylinder. Direct torque strategy controls the induction motor, Recursive least squares determines the adhesion-slip state of wheels, Sliding mode control Strategy calculates the best braking force. The simulation results show the high brake performance of this wheel-slip prevention system, and the desired objective of control.
Abstract: The nonlinear superharmonic resonance phenomenon of damped circular sandwich plates under uniform load is investigated. From the movement equation of circular sandwich plate showed in displacement components, got the relevant nonlinear vibration equation by Galerkin method. Under the clamped BC. Using multi-scale method, the periodical solutions were obtained which was of nonlinear the third-order superharmonic resonance. The FRF equation of the superharmonic resonance is obtained, and the necessary and sufficient condition on stability of the vibration are obtained synchronously.The infection to the amplitude while the correlative physical and geometric parameters changing were discussed, Drew the trajectories in moving phase planes during the stabilization process, and the stabilities and singularities of the solutions are analyzed.
Abstract: The nonlinear forced vibration of damped circular sandwich plates is studied. From the movement equations of circular sandwich plate expressed in displacement components, got the relevant nonlinear vibration equation by Galerkin method. The standard Duffing equation with square and cubic minor items was obtained by dimensionless processed. The quadratic analytical solution of the principal resonance was deduced by multi-scale method. The FRF of primary resonance periodical solutions were obtained, synchronously the necessary and sufficient condition on stability of the vibration are obtained. The infection to the amplitude when the correlative physical and geometric parameters changing was discussed. The trajectories in moving phase planes during the stabilization process, the stabilities and singularities of the solutions are analyzed.
Abstract: The single array element of cymbal transducer has a low transmitting power, poor directivity and narrow bandwidth, which however can be improved, even overcome by array forming. First of all, 9 cymbal transducer array elements were designed and made on the basis of the research results obtained in the early stage, and were assembled into a 3x3 array by using a set of stable and reliable array forming techniques developed from the research. The array was shaped by casting with organic silica-gel and then getting cured. The array was tested in air for resonance frequency and equivalent circuit parameters demonstrating the stability of array forming techniques. The array and a single array element were also tested in anechoic water-tank for transmitting, receiving and directivity performances, and the result indicates that, the array forming by elements can strengthen the transmitting power and improve the directivity effect, but may reduce the free-field receiving sensitivity. The research has a great significance to the development of a new super multi-element cymbal array.