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2 2015

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Numerical, experimental and analytical study on MRE used for vibrating pile hammer efficiency improvement

Kwietniewski M., Miedzińska D., Nguyen H. P., Gieleta R., Osiński J.

Journal of Achievements in Materials and Manufacturing Engineering

2015

Vol. 73, nr 2

151--156

Purpose: of this paper is a research on Vibratory Pile Hammer (VPH) efficiency improvement with the use of Magnetorheological Elastomer (MRE) controlled with external magnetic field. Design/methodology/approach: The analytical equations are made to describe physical dependence of MRE on VPH work. To describe elastomer properties reduced polynomial model proposed by Oon H. Yeoh was used. The shear tests for Magnetorheological Elastomer of two with different volume of carbonyl-iron particles and its influence on elastomer pillow implemented in VPH were carried out. Tests were carried out in external magnetic field and without it. Numerical analyses were conducted with the use of MSC Software applying Finite Elements Method (FEM). The FE model was built on the experimental boundary conditions. Findings: MRE significantly changes elastic properties under applied magnetic field, what can be used to stiffness and damping properties of the construction control. Research limitations/implications: In further analyses, the test results will be used for the evaluation and selection of MRE regulation system. Practical implications: The presented results were used in modification of Vibratory Pile Hammer to improve its efficiency and a maintain device in resonance. Originality/value: The new application of the phenomenon of MRE stiffness change caused by the variable external magnetic field will allow to keep the mechanical system in resonance.

Experimental and analytical research on resonance phenomena of vibrating head with MRE regulating element

Miedzińska D., Gieleta R., Osiński J.

International Journal of Applied Mechanics and Engineering

2015

Vol. 20, no. 1

201--208

A vibratory pile hammer (VPH) is a mechanical device used to drive steel piles as well as tube piles into soil to provide foundation support for buildings or other structures. In order to increase the stability and the efficiency of the VPH work in the over-resonance frequency, a new VPH construction was developed at the Military University of Technology. The new VPH contains a system of counter-rotating eccentric weights, powered by hydraulic motors, and designed in such a way that horizontal vibrations cancel out, while vertical vibrations are transmitted into the pile. This system is suspended in the static parts by the adaptive variable stiffness pillows based on a smart material, magnetorheological elastomer (MRE), whose rheological and mechanical properties can be reversibly and rapidly controlled by an external magnetic field. The work presented in the paper is a part of the modified VPH construction design process. It concerns the experimental research on the vibrations during the piling process and the analytical analyses of the gained signal. The results will be applied in the VPH control system.