Rock fragmentation mechanisms and an experimental study of drilling tools during high-frequency harmonic vibration

Abstract

Resonance drilling is a new technology, still at the laboratory stage. It has great potential to state mechanical vibration excited by harmonic vibration in rocks and an apparatus was built to achieve other parameters on the rate of penetration (ROP) in resonance drilling was analyzed. The results show that the rock drillability decreased with an increase in excitation frequency. When drilling with a large size drill bit, the ROP increased with excitation frequency. The ROP reached a maximum value at the resonant frequency of the rock. The ROP of the bit increased linearly with rotary speed when no vibration was applied on the rock and increased approximately exponentially when harmonic vibration was applied. In addition, the resonant frequency of the rock was changing during the process of rock fragmentation, so in order to achieve the desired resonance of the rock, it is necessary to determine an appropriate harmonic vibration excitation frequency.

The Mechanical Properties of Granite under Ultrasonic Vibration

“…In the strain decrease stage, crack closure can change the internal structure of the rock [32,35], which in turn can affect the response of the rock to ultrasonic vibration. When rock is subjected to a continuous harmonic external excitation, a steady-state response is generated in the rock as follows [35]:…”

“…When the rock had deformed to its compressive limit, the natural frequency also approached its maximum, and so did the displacement amplitude. e fatigue process will accelerate due to increased displacement [30,35]. As the cracks subsequently expanded, the natural frequency decreased, and a decrease in the displacement amplitude occurred.…”

“…e results of our study show that the frequency of vibration had a significant influence on the mechanical properties of the granite samples. When the vibration frequency is close to the natural frequency of the sample, resonance will cause a significant increase in the displacement amplitude of the sample [35].…”

“…e abovementioned studies all focused on the mechanical properties of rock under conventional low-frequency cyclic loading. It has been found that the effect of this process on the mechanical properties of rock is related to the loading frequency, and many investigators have concluded that the response of rock materials under external harmonic excitation will change with loading frequency [34][35][36].…”

Research on Energy Response Characteristics of Rock under Harmonic Vibro-Impacting Drilling

“…Slow penetration rate, drilling tool failure and other problems have always been the major troubles in drilling operation [1][2][3]. As a result, many efficient techniques for rock breaking are proposed to enhance the penetration rate [4][5][6][7].…”