Research on the Matching of Impact Performance and Collision Coefficient of Hydraulic Rock Drill

Yelin Li,Amr A Nassr

doi:10.1155/2021/6651860

Abstract

The stress wave produced by the piston impact, on the drill rod, is an important factor affecting impact performance. It is particularly important to control the stress waveform generated by the piston impact on the drill rod to meet the requirements of efficiency and component durability of some impact mechanical systems. Based on wave theory, the impact stress wave model of rock drilling is established, a dimensionless collision coefficient γ is put forward, and the matching relationship between different collision coefficients γ and stress waveforms is analysed. The length of the impact piston under the same material condition determines the change rule of the waveform. The stress waveform experimental verification is thus designed. The pressure chamber curves of different pistons in the rock drill were tested, the collision velocity of the piston was obtained, and the impact energy and impact power were calculated. The relationship between the impact performance and the collision coefficient γ is analysed. When γ is in the range of 9–11, the impact piston’s design of a high-power rock drill can be satisfied. When γ is in the range of 3∼5, it is mainly designed for low-power rock drills.

Highlights

As drilling equipment, rock drills are widely used in mining, tunnel excavation, urban construction, slag removal, and other operations
The hydraulic motor of the rock drill drives the drill bit to rotate and break the rock. e rock cuttings are discharged by using flushing water or air
Dante [16] systematically studied the propagation of stress waves in shock mechanical systems. It can be seen from the above analysis that in the hydraulic rock drill, the parts collide with each other, such as piston, shank, and drill rod, in the direction of impact and the axial dimension is far larger than the radial dimension, so it is not appropriate to simplify them as mass points by using classical collision theory

Summary

Introduction

Rock drills are widely used in mining, tunnel excavation, urban construction, slag removal, and other operations. Hashiba [9] simulated the impact process of the rock drill based on the one-dimensional wave theory and researched the dynamic drilling characteristics by using the two-point strain measurement method. Dante [16] systematically studied the propagation of stress waves in shock mechanical systems It can be seen from the above analysis that in the hydraulic rock drill, the parts collide with each other, such as piston, shank, and drill rod, in the direction of impact and the axial dimension is far larger than the radial dimension, so it is not appropriate to simplify them as mass points by using classical collision theory. E relationship between impact power and collision coefficient is obtained, which provides a theoretical basis for structural design, optimization, and energy efficiency evaluation of hydraulic rock drills Based on the stress wave testing technology, the stress wave curves of different length impact pistons are tested and the impact performance is calculated. e relationship between impact power and collision coefficient is obtained, which provides a theoretical basis for structural design, optimization, and energy efficiency evaluation of hydraulic rock drills

Stress Wave Model and Collision Coefficient

Impact Energy Experiments of Different Pistons

Figure 9

Conclusions