Papers by Keyword: Transmissibility

Abstract: It is well known fact that vibrations contribute to excessive wear, fatigue failure and other premature failure of machine components. Thus, various methods have been applied to control these vibrations. One of the commonly used is vibration absorber. The aim of this paper is to explore the potential of epoxy reinforced natural fibers as an alternative material for vibration absorber. Both mechanical properties and dynamic characteristic of the composites are investigated through tensile test and transmissibility test, respectively. Two types of natural fibers were selected for the study; coconut coir and pineapple leaf. The results show that the tensile modulus of composites increases with the increase of fiber content, although the strength was found decreases. This reduction indicates an ineffective stress transfer between the fiber and matrix. From the tensile test result, 20 vol% of pineapple leaf fiber was found to be the optimum fraction, in which afterward was employed for fabrication vibration absorber. Meanwhile, from the transmissibility test, it was noticed that when base excitation increases, the resonance peak and attenuation frequency were changed to the lower value. The fixed-fixed end beam with attached composite vibration absorbers showed that the resonance amplitude of the beam decreased significantly. More absorbers attached on the beam produce better result in attenuating the global structural vibration.

Abstract: Characteristics cushions from PU foam together with coat determine comfort automobile seats. Frame of car seat with cushion from PU foam and cover serve like body rest. Also perform safety rules, that are demanded on car seat. Cushion in car seat is basically manufactured from PU foam. Experimental testing their property investigate correlation between their characteristic and comfort. One type of experiment is combination static and dynamic loading in medium term time interval . Subject research and content hereof article is recognition transmission characteristics and contact pressures cushions from PU foams in time interval two o'clock in turns static and dynamically weight constant loading.

Abstract: This paper presents the Mullins effect on the laminated rubber-metal spring analytically modeled using lumped parameter system. The general form of the equation is developed to represent the multi-degree-of-freedom system for layer of embedded metal plates. The Mullins effect can be observed when a compression load is applied to the spring. It is shown that by increasing the embedded metal plate, the Mullins effect inside the rubber is reduced due to the improved stiffness in vertical direction.

Abstract: In International Standard 10819 (1996), the requirements for a glove to be considered an anti-vibration glove are determined by the transmission of vibration to the palm of the hand. The transmission of vibration to a finger is very different from the transmission of vibration to the palm, but there are currently no requirements to measure the transmission of vibration through gloves to the fingers. This study investigated the effects of material dynamic properties on the transmission of vibration to the palm of the hand and to the fingers. Two materials (foam material from one anti-vibration glove and gel material from another anti-vibration glove) were investigated. Subjects placed their palms or index fingers on the material and pushed down with a force of 10 N while the transmission of random vibration was measured over the frequency range 5 to 500 Hz. At frequencies greater than 20 Hz, both materials attenuated vibration to the palm of the hand but amplified vibration to the finger. The study shows that the materials in gloves can both attenuate and amplify the transmission of vibration, depending on the material, the frequency of vibration, and the location on the hand (palm or finger).

Abstract: The laminated rubber-metal spring is well known in application as the vibration isolator for earthquake protection. The spring is therefore designed to be able to sustain the vibration waves from horizontal direction. This paper discusses the possibility of the laminated spring to be employed for other applications where the excitation mainly comes from axial direction, such as to isolate vibration transmission from heavy engine. The model is first developed for a simple finite rod to simulate the effect of internal resonances at high frequency when the wavelength is much smaller than the length of the rod. The effect of metal plates inserted in the rubber is then modelled using the lumped parameter system. The results are presented in terms of the vibration transmissibility.

Abstract: In this paper are presented some aspects of transmissibility control of mechanical systems with 1 DOF so that the effects of vibration on their action to be minimized. Some technical solutions that can be used for this purpose is analyzed. Starting from the mathematical model of an electro-mechanical system with 1 DOF, are identified the parameters which influence the effectiveness of the transmissibility control system using an electrodynamic actuator who work in "closed loop".

Abstract: Starting with the mathematical model of a simple electro-mechanical system with 1 DOF, are identified the electrical parameters which may influence the efficiency of control of the system transmissibility using an electrodynamic actuator. Based on simulation of system operation and determination of transmissibility are obtained Bode diagrams and diagrams that shows the maximum variation of the resonance frequency of the system when varying the electrical parameters of the actuator. In the paper is indicated the limits of the theoretical and practical technical solutions to control mechanical transmissibility of a system using an electrodynamic actuator.

Abstract: This paper discusses the isolation performance of a laminated rubber-metal spring. A multi-degree-of-freedom-system model using mass-damper-spring components is developed to calculate its transmissibility due to only axial vibration in the spring. The results show the embedded layers of metal plate can improve the transmissibility at high frequency.

Abstract: Metal Rubber(MR) vibration isolator is a new type of isolator developed to overcome the fatal aging phenomenon of current rubber isolator. It has broad practical application in the military, such as aerospace. In this paper, the fatigue life experiment is conducted to MR vibration isolator, and resonant frequency and resonant accelerate transmissibility are chose as degradation parameters. It’s found that MR vibration isolator possesses jump phenomenon; resonant frequency and resonant transmissibility increase quickly to the maximum, then attenuate slowly with the increasing number of vibration. This provides fundamental basis for the design and application research of MR vibration isolators.

Abstract: A method is formulated to model the properties of honeycomb paperboard based on Hilbert transform, In this method, there are no assumptions on the forms of the stiffness and damping properties, this method is truly nonparametric. An experiment system is set up to record the free response of the mass loaded honeycomb paperboard system, the experiment data are used to identify the stiffness and damping properties of honeycomb paperboard. The motion equation of mass loaded honeycomb paperboard system is formulated, the transmissibility curve is simulated, the comparison of the simulated curves and the experiment data indicates the model in this paper is accurate.