Advanced Materials Research Vols. 199-200

Abstract: In recent years, vibration roller market has required increasingly not only on working capacity but also ride comfort. Thus, in order to reduce the effect of vibration to operators, identification and elimination of vibration sources are the most important tasks to achieve optimum design. In this paper, the attention is paid to cab’s low-frequency sloshing analysis and optimal design for cab’s isolation system of vibratory roller. When working, it often exists the problem of cab’s low-frequency sloshing in the direction of forward motion. In order to solve this problem, the dynamic test and simulations analysis are carried out; and the main reasons causing cab’s low-frequency sloshing are found out. The optimization model according to the two points response amplitude in the direction of forward motion on the cab to reach the minimum value in the low frequency range is proposed in this paper. And also, the auxiliary vibrations isolator for solving the low-frequency sloshing in the direction of forward motion is designed.

Abstract: The random vibration will cause a severe decline of the dynamic imaging quality if the seeker’s optomechanical system has not been properly optimized. Firstly, based on the integrated optomechanical analyzing method and the requirement of the seeker, an optimization approach utilizing the numerical simulation is presented. Then an optimization design of the support position, in which the optical modulation transfer function is as the optimal target, was processed under the random vibration with high-accelerator in a wide frequency range (10 GRMS). The simulation result shows that the optimum structure has a better performance than the other available structures in dynamic imaging quality: the degradation of optical modulation transfer function is less than 0.5% in central field of view and about 8.25% in the full relative field of view.

Abstract: An analytic method is developed for dynamic stress concentration of a subsurface elastic cylindrical inclusion below a semi-cylindrical hill under SH-wave. And the dynamic stress concentration factor (DSCF) is given by complex variable function. During the solution, a standing wave and scattered wave displacement functions are constructed in different parts respectively. All of these displacement functions should satisfy the boundary conditions of each part. Employed to the boundary conditions around the elastic cylindrical inclusion, a series of infinite algebraic equations about the problem can be obtained. The calculating results of DSCF around the elastic cylindrical inclusion are plotted to show the effects of some parameters on DSCF.

Abstract: An analytical solution based on modal decomposition is presented to investigate Lamb wave scattering at plate end. Take boundary condition into biorthogonality relation, a matrix equation is established with all matrix elements have analytical expressions. The scattering feature is then expressed in matrix form, named as reflection matrix, which has explicit expression composed of those matrixes. Calculation examples have be implemented when antisymmetric modes are reflected. Scattering coefficients are figured out in a range when frequency-thickness product vary from 0 to 8kHzm, to prove the calculation efficiency. The calculation precision is very close to the least square method based on model discretization.

Abstract: A scheme of the separate control technique of electro-hydraulic vibrator is proposed, in which symmetrical hydraulic cylinder is controlled by a parallel mechanism of a two-dimensional valve (named as 2D valve) and a parallel servo valve. The working frequency and vibration amplitude of the electro-hydraulic vibrator are dominated by the rotary speed and the sliding displacement of the spool of the 2D valve respectively, and the vibration central piston is controlled by the sliding displacement of the spool of the parallel servo valve. This paper analyzes the relationship between vibration characteristic values and control parameters using the analytic method based on the hydrodynamic control theory. The experimental system is built to verify that the theoretical analysis is consistent with measured results.

Abstract: The shock signal’s fluctuation characteristics of debris flow stem from two aspects, one is the composition of debris flow with the solid and the liquid, another is the surging property of debris flow in motion. Based on the initial shock signals collected in model experiment in laboratory, 9 shock spectrum levels are decomposed by the db8 wavelet method, i.e., 0~0.195Hz, 0.195~ 0.391Hz, 0.391~0.781Hz, 0.781~1.5625Hz, 1.563~3.125Hz, 3.125~ 6.25Hz, 6.25~12.5 Hz, 12.5~25Hz, and 25~50Hz. Taking the peak each shock spectrum as the standard, the energy distribution curves of 9 shock spectrum levels are obtained. These curves display that the shock energy of debris flow focus on the low frequency smaller than 1.0Hz, and the percentage below 6.25Hz is about 95%. The results provide a reference to select wallop peak as the design load of structures against debris flow disaster.

Abstract: It is generally existed that the vibration problem of hydraulic gate structure during water conservancy project, whose vibratory magnitude is closely related to inherent feature of gate structure and spectrum signature of hydrodynamic loads. In this project, through contrastive analysis of modal test procedure of multi-support excitation and single-point response as well as finite element computational analysis, test model and finite element model of some hydraulic sector gate had been built to indicate the results of modal test were basically close with that of finite element model, the changing frequency being the same. Both of them could truly reflect the dynamic characteristics of gate, which proved it effective that the methods for researching on vibration modes of hydraulic gate adopted and provided important basis for further dynamics research and design optimization.

Abstract: The problems of SH-wave scattering caused by a subsurface circular lining structure and a beeline crack with arbitrary length at an arbitrary position were studied by using the methods of Green's function, complex variables and multi-polar coordinates. A adaptive Green's function, an essential solution to the displacement field for the elastic space possessing circular lining structure while bearing out-plane harmonic lining loads at an arbitrary point, was constructed firstly, and then a crack was created using “crack-division”. Thus the expressions of displacement and stress were established while the crack and the inclusion both existed. Finally, we give some numerical examples to discuss the variety of the horizontal surface displacement in the case of different parameters.

Abstract: The modal properties of continuous active structures are studied in this paper. The reciprocity theorem is derived and presents the relationship between the two co-adjoint active structures. The modal orthogonality conditions of the active plate and active beam with distributed sensor and actuator are developed. The continuous active structures and their adjoint active structures have the same eigenvalves, and their modes are weighted orthogonal. The present study concludes that the modes of active structures are related to the control law, measurement and actuation configurations. As a numerical example a rectangular plate was calculated to give the notes about modes of the active structures.

Abstract: In the view of the fault of bistable response appeared in the disk-rod-fastening rotor, the peculiar structure of this kind rotor was taken into account in this paper. By considering the influence of contact effect of discontinuous interfaces on the rotor stiffness, the tie-rod and the contact surface between the wheel disks were equated to a bending resistance spring with nonlinear stiffness. Then the equation of motion of the disk-rod-fastening rotor was put forward according to this simplification. The vibration characteristics of rotor was calculated by the harmonic balance method that combined with the predict-correct and homotopy arithmetic. The bistable response behaviors recurred in this simplified model was much closer to the measured results in flying. The study showed that the nonlinear factor of stiffness, resulted from the contact effect of discontinuous interfaces, was the main reason which led to the appearance of bistable response in the disk-rod-fastening rotor.