Transmission and Dissipation of Stress Wave at a Sleeve of Percussive Rock Drill

Transmission and dissipation of stress wave at a percussive-drill rod-joint of the coupling sleeve type were determined at three sleeve-preload levels. The experimental results show that a tension wave is reflected from a sleeve, following the compression incident wave. An amplitude of reflected wave decreases with sleeve-preload. These observed results indicate that the ends of rods coupled by the sleeve do not contact perfectly each other. A simple model (model 1) is proposed which consists of two rods and a spring connecting two rods. The spring k12 with a finite spring constant represents rigidity between two rod ends. Selecting an appropriate value for a spring constant, good agreement is obtained between numerical and experimental results. Model 2 is also proposed which is characterized by a spring k12, the mass for sleeve and two additional springs representing the rigidity between rod and sleeve. The model 2 is an improved version of model 1 and very good agreement is obtained in case of transmission of compression wave.