Mulyadi Bur

Dynamic Vibration Absorber for Squeal Noise Suppression in Simple Model Structures

In recent research it was found that squeal noise caused by friction-induced vibration can result in mode coupling instability. Presently, there is no method that can be reliably used to eliminate this kind of noise. This paper is focused on the use of dynamic vibration absorbers (DVAs) to suppress the generation of squeal noise. The performance of the DVA is investigated numerically for two simple cases, i.e. a simple two-degree of freedom model, and an L-shape space frame. It is found that the DVA can be applied to shifting or reducing the unstable region of mode coupling, by which the unstable region is removed from the operating condition. Particularly, the addition of the DVA in horizontal direction on the near-point-of-friction can possibly avoid unstable mode coupling. However, the addition in vertical direction will increase the possibility of squeal noise incident. Moreover, a high frequency DVA in horizontal direction at the near-point-of-friction shifts the unstable region into higher normal contact stiffness and higher friction coefficient. Consequently, addition of a mass with very stiff spring or a rigid mass in the horizontal direction can prevent the occurrence of unstable mode coupling, as long as it is not coupled with the vertical direction. If the added mass affects the dynamic behaviors in both vertical and horizontal directions, squeal noise in the original normal contact stiffness can still occur.

Response Reduction of Two DOF Shear Structure Using TMD and TLCD by Considering Absorber Space Limit and Fluid Motion

A Combination of dynamic vibration absorbers (DVAs) consist of Tuned Mass Damper (TMD) and Tuned Liquid Column Damper (TLCD) for reducing vibration response of a two-DOF shear structure model is proposed. The absorber parameters are optimized using Genetic Algorithm (GA). The cost function is derived from the ratio between structure response and the excitation signal. The limitation in absorber space and fluid motion are considered during optimization process. The simulation results show that GA optimization procedure is effective to get the optimal absorber parameters in the case of limited absorber size and motion.

The influence of TLCD junction angle on the structure response with TLCD

A Tuned Liquid column Damper (TLCD) performance depends on the TLCD natural frequency and damping ratio. Theoretically, the TLCD natural frequency is determined by its dimension and the length of fluid inside TLCD column. The damping ratio of TLCD is influenced by several factors such as friction between the fluid and TLCD column, TLCD junction angle and a built-in orifice plate with a small opening. In this research, the effect of TLCD junction angle to its performance in reducing the structural response is evaluated by varying the TLCD angle from 30° to 90°. An experimental model of two DOF shear structure with TLCD is governed to evaluate the TLCD performance. The experimental results show that a TLCD with junction angle 60° filled with 325 ml water is better than others in reducing the vibration response of a two DOF shear structure.A Tuned Liquid column Damper (TLCD) performance depends on the TLCD natural frequency and damping ratio. Theoretically, the TLCD natural frequency is determined by its dimension and the length of fluid inside TLCD column. The damping ratio of TLCD is influenced by several factors such as friction between the fluid and TLCD column, TLCD junction angle and a built-in orifice plate with a small opening. In this research, the effect of TLCD junction angle to its performance in reducing the structural response is evaluated by varying the TLCD angle from 30° to 90°. An experimental model of two DOF shear structure with TLCD is governed to evaluate the TLCD performance. The experimental results show that a TLCD with junction angle 60° filled with 325 ml water is better than others in reducing the vibration response of a two DOF shear structure.

A new concept for UAV landing gear shock vibration control using pre-straining spring momentum exchange impact damper

This study proposes a new method for reducing the shock vibration response of an Unmanned Aerial Vehicle (UAV) during the landing process by means of the momentum exchange principle (MEID). The performance of the impact damper is improved by adding a pre-straining spring to the damper system. This research discusses the theoretical application of the damper to the UAV landing gear system. The UAV dynamics is first modeled as a simple lumped mass translational vibration system. Then we analyze a more complex two-dimensional model of UAV dynamics. This model consists of the main wheel, nose wheel and main body. Three cases of UAV landing gear mechanisms: without damper, with passive MEID (PMEID) and with pre-straining spring MEID (PSMEID) are simulated. The damper performance is evaluated from the maximum acceleration and force transmission to the main body. The energy balance calculation is conducted to investigate the performance of PSMEID. The simulation results show that the proposed PSMEID method is the most effective method for reducing the maximum acceleration and force transmission of UAV during impact landing.

Performance Analysis of 3-URU Spherical Parallel Mechanism Designed Based on Velocity Transmission and Force Constraint Indices

In this paper was observed performances of developed three degrees of freedom (dof) parallel mechanism named 3-URU spherical parallel mechanism. The mechanism is composed of three identical limbs mounted symmetrically to base (fixed link) and platform (output link). The limb is constructed by universal-revolute and universal joints. The kinematic constants of mechanism consisting of link lengths, radius of platform, radius of base, mounting angle of limb and platform to base and platform were determined with consideration of velocity transmission and force constraint indices. To evaluate performance of mechanism, it was manufactured a prototype of mechanism designed base on these two mentioned indices. There are three steps proposed to realize the mechanism, (i) kinematic synthesis to determine of kinematic constants, (ii) design of mechanical components to define shape and dimension of links and joints by considering collision in wokingspace and static analysis, (iii) evaluation of mechanism performances consisting of workingspace, controllability of platform motion and static payload. Based on obtained results, it can be clarified that, the mechanism can produce spherical motion of platform which rotates on steady point recognized as center of platform rotation. The platform can achieve maximum inclination angle, 80 degree and at this posture occurs translational error, 0.0102 mm. On the other hand, the mechanism can support payload ten times of weight of moving parts.