Abstract
Transmission and dissipation of stress wave at a percussive-drill rod-joint of the coupling sleeve type are discussed with special attention to the effects of wave length and rod diameter.At first, a simple model proposed by Okubo et al, which consists of two rods and a spring, is analytically examined. It is found that dissipation of stress wave at a model sleeve depends on non-dimensional parameter t1/τ: larger dissipation for smaller value of t1/τ. t1 and τ=Z/2k are wave length and retardation time, respectively, and Z is characteristic impedance of rod.Experiments are carried out with five combinations of rod and sleeve ranging from 32 to 51 mm nominal diameters. Also, five kinds of hammer are used to impact rod end and generate elastic wave. The experimental results show that dissipation increases with rod diameter or Z, and decreases with hammer weight or t1. It is found that fairly well agreement can be obtained between theoretical and experimental results.Also, dissipation during drilling by a rock drill is measured. It is found that amplitude of elastic wave decreases by 2.9% per sleeve. This result can be also explained by the model.
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