Due to the sweep excitation of the vibrator, the dynamic stiffness of the seismic vibrator has an enormous influence on the performance of the vibroseis system and the accuracy of the output signal. In order to improve the dynamic stiffness of the vibrator, an optimization strategy is presented to improve the weak link which is defined by dynamic analysis of the vibrator. The weak link is the weakest part, which brings about the resonance, and the weak link in different excitation frequencies is identified by dynamic stiffness analysis in this method. A modified finite element model with reaction mass is built; harmonic response analysis and modal analysis are employed to find out the weak link of the vibrator, which indicates that the supporting column is the weakest component. Sensitivity analysis is used to determine the optimization parameters of the supporting column. Response surface model developed from a parametric finite element model is used to establish the objective function, and the mass is the constraint condition. The optimization problem is solved by particle swarm optimization, and the dynamic stiffness of the optimized vibrator is calculated by harmonic response model. Results show that compared with the original model, the natural frequency of the optimized vibrator is increased by 6.63% and the resonance peak is decreased by 9.00%.

This paper is focused on the influence of the rough contact interfaces on the dynamics of a coupled mechanical system. For this purpose, a two-degree-of-freedom model of a coupled seismic-vibrator-rough-ground system is proposed with which the nonlinear vibration properties are analyzed. In this model, the force-deflection characteristic of the contact interfaces is determined by finite element analysis. By analyzing the undamped free vibration, it was found that the variation of the second-order natural frequency with amplitude increases with rougher contact interfaces; however, the amplitude has little influence on the first-order natural frequency of the system. For the harmonic excited analysis, the jump frequencies and hysteretic region both decrease with rougher contact interfaces. Moreover, it is inferred from the bifurcation diagrams that, increasing the excitation force, the system can bring about chaotic motions on rough contact interfaces.

No abstract

No abstract

No abstract