Abstract:

This study proposed a transfer path analysis (TPA) method to estimate the percussion force of hydraulic breakers. The frequency response function (FRF) obtained through modal impact experiments are applied to the TPA model. The impact stress wave generated from the piston transmitted to the housing of hydraulic breaker. The impulsive force components on the housing were measured. The force components derived from TPA model are compared with the data obtained from the standard method using strain gauges. The TPA data were in good agreement with the standard method. This new method can be used to estimate the forces and vibrations of hydraulic breakers and rock drilling machines.

1 Introduction

An excavator is often equipped with a hydraulic breaker to fracture the ground or bedrock in order to produce resource materials, aggregates, or to demolish structures (Song et al., 2017; Kwak and Chang, 2008; Giuffrida and Laforgia, 2005) (Figure 1(a)).

The hydraulic breaker comprises a directional valve, which controls the flowing direction of fluid; an accumulator for storing the hydraulic energy and for supplying necessary flow during the operation. The back head which is filled with nitrogen gas; pistons for delivering the striking energy to the chisel while performing a reciprocal motion; and a chisel which directly breaks the subject material. The hydraulic breaker is mounted onto an excavator by a coupler (Figure 1(b)).

Previous studies of hydraulic breakers include the work of Ficarella et al., (2006, 2007, 2008), who used a 1D simulation and experimental tests to investigate the performance and design of a hydraulic breaker. Several other studies have focused on improving performance, reducing the weight of the housing, and optimizing vibration and noise (Lee et al., 2003; Park et al., 2011).

In the construction equipment having percussive operations, the impact loads are continuously generated, and these are closely related to the durability of the equipment. However, few studies have sought to quantify the impact loads delivered to the housing. Because the strain gauges attached on the equipment easily break away during the percussion test, a direct measurement and data acquisition are very difficult.

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