Experimental study and mathematical modelling of a new of vibro-impact moling device

International Journal of Non-Linear Mechanics 43 (2008) 542 – 550

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Experimental study and mathematical modelling of a new of vibro-impact

moling device

Van-Du Nguyena, Ko-Choong Woob,∗, Ekaterina Pavlovskaiac

aThai Nguyen University of Technology, 3-2 Street, Thai Nguyen City, Viet Nam

bThe University of Nottingham Malaysia Campus, Faculty of Engineering and Computer Science, Jalan Broga, 43500 Semenyih, Selangor, Malaysia cCentre for Applied Dynamics Research, School of Engineering, University of Aberdeen, King’s College, Aberdeen AB24 3UE, Scotland, UK

Received 26 April 2007; received in revised form 7 September 2007; accepted 3 October 2007

Abstract

In this paper experimental study and mathematical modelling of newly designed vibro-impact moling rig are presented. The design is based

on electro-mechanical interactions of a conductor with an oscillating magnetic field. The rig consists of a metal bar placed within a solenoid

which is connected to an RLC circuit, and an obstacle block positioned nearby. Both the solenoid and the block are attached to a base board.

Externally supplied alternating voltage causes the bar to oscillate and hit the block resulting in the forward motion of the base board mimicking

a mole penetration through the soil. By varying the excitation voltage and the capacitance in the circuit, a variety of system responses can be

obtained.

In the paper the rig design and experimental procedure are explained in detail, and the mathematical modelling of the rig is described. Then

the obtained coupled electro-mechanical equations of motion are integrated numerically, and a comparison between experimental results and

numerical predictions is presented.

2007 Elsevier Ltd. All rights reserved.

Keywords: Vibro-impact; Solenoid; Impact force; Moling

1. Introduction

Vibro-impact machines have been used since 1949 for the

installation of piles. The impact-vibration hammer, introduced

by Tsaplin [1] consisted of a vibrator unit and springs placed

inside a frame, where rotating eccentric masses induced vi￾brations and impacts in the vertical direction. The adoption

of the vibro-impact principle to a horizontal direction applica￾tion also involved the use of rotating eccentric masses [2,3].

In order to install underground cables and pipes, the diameter

of the mechanism had to be reduced to 100 mm or even less.

The cam system of Lok [4] addressed this issue. However, due

to the friction between moving parts and high stresses gener￾ated, the reliability of this device posed a problem for further

∗ Corresponding author.

E-mail address: [email protected] (K.-C. Woo).

0020-7462/$ - see front matter 2007 Elsevier Ltd. All rights reserved.

doi:10.1016/j.ijnonlinmec.2007.10.003

development. A detailed investigation of the vibro-impact

mechanism had been performed with an electromagnetic

shaker by Franca and Weber [5]. Nevertheless, the diameter

of the electromagnetic shaker was still much larger than the

100 mm required.

The new idea developed in this paper is to use the solenoid￾activated system for the pipe installation. The linear self￾oscillating motor of Mendrela and Pudlowski [6] can serve as

the basis for such system. This motor is capable of oscillations

in a vertical direction and is based on the electrical resonance

of the current in the series RLC circuit, the phenomenon which

was described by Blakley [7]. Mendrela’s motor worked with￾out a mechanical load, and there is no known application of

this motor to either pure impact or vibro-impact systems, both

theoretically and experimentally.

This paper describes the design, operation and mathematical

modelling of a novel vibro-impact mechanism which can be

used in moling machine. The design is based on the resonance