A Study of a Pendulum-Like Vibration Isolator With Quasi-Zero-Stiffness

This article introduces a pendulum element to a 3-spring vibration isolator to achieve a high-static-low-dynamic (HSLD) stiffness or even quasi-zero stiffness (QZS) around the equilibrium position. Numerical simulation is given and the harmonic balance method (HBM) is used to obtain time responses for analysis. Effects of different parameters on the isolation performance are studied and summarized. Approximation force and displacement transmissibility of the system are calculated to evaluate the isolation performance. Comparisons are made with those of an equivalent linear isolator and the typical 1 degree-of-freedom (DOF) QZS isolator. Results show that the novel vibration isolator performs better than existing isolators under selected parameters. The left bent backbone of the novel isolator demonstrates evident softening geometric nonlinearity. Therefore, it achieves a wider frequency range of isolation than the linear 1DOF isolator and typical 3-spring QZS isolator. Moreover, the transmissibility of the novel isolator is smaller at higher frequencies as the jump phenomenon occurs on the left.

Research on the Performance of an Aircraft Landing Gear Hook Lock Based on Bifurcation Analysis

To design and analyze a hook lock mechanism for a certain type of aircraft landing gear, numerical continuation and bifurcation theory are employed to study the performance of the lock mechanism in this paper. First, dynamic and static models of the hook lock mechanism are created separately, and by analyzing the locking and unlocking processes of the lock mechanism, the dynamic results are compared with the static numerical continuation results. According to the results, the static numerical continuation results agree excellently with the dynamic model results at the position of the stable equilibrium solution. Although the dynamic results can hardly explain the jump phenomenon of the lock mechanism at the moment of locking or unlocking, the bifurcation point of the static results suggests the occurrence of a stability change in the lock mechanism at the moment of jumping, thereby explaining the jumping mechanism of the lock mechanism. Therefore, the influences of the landing gear overload, lock spring parameters and attachment position on the performance of the lock mechanism are investigated. Furthermore, the critical installation position of the limit stop is defined, and the critical unlocking force of the lock mechanism is designed optimally based on the multi-island genetic algorithm.

Study of the relation between hydraulic jump and the flood water level in the river on the downstream of a spillway

Kuningan Dam which is located in Kuningan District, West Java has 21,8 km2 watershed area. This dam also acts as a flood control facility which functions supported by the reservoir’s topography and its spillway building. The spillway building releases excess water from the dam into the downstream area. In the downstream part of the spillway, usually, hydraulic jump phenomenon occurs which depends on the flood water level of the river. The hydraulic jump used in the designing process of stilling basin length. The stilling basin in the spillway building generally designed using Q100. The spillway in Kuningan Dam is designed as a closed conduit channel. In this study, the Kuningan Dam spillway is re-designed as an open channel using ogee type spillway. Based on the modeling result, the length of hydraulic jump that occurs when modeled with the return period discharge of Q25 is 21.54 m, Q50 is 16.65 m, and Q100 is 0.98 m. It is seen that in Q25 the jump was the furthest, so an elaborate study regarding hydraulic jump phenomenon and design standards of the spillway is required.

ASYMPTOTIC EXPANSION OF SOLUTION OF GENERAL BVP WITH INITIAL JUMPS FOR HIGHER-ORDER SINGULARLY PERTURBED INTEGRO-DIFFERENTIAL EQUATION

In this article we constructed an asymptotic expansion of the solution undivided boundary value problem for singularly perturbed integro-differential equations with an initial jump phenomenon m – th order. We obtain the theorem about estimation of the remainder term’s asymptotic with any degree of accuracy in the smallparameter.