| As an important component of gallery drilling equipment, the drill pipe is thenecessary tool for drilling operation in underground coal mines. Its fatigue performanceinfluences directly the safe and stable operation of drilling in gallery. Aiming at a few ofresearch on invalidation due to fatigue of outer flat drill pipe and lack of necessary meansof fatigue test, the paper, on the basis of analysis and summing up the previous research andthe existing problems, selected φ63.5mm1500mm friction-welded outer flat drill pipe asresearch object, has obtained the following research results:（1）According to the movement status of drill pipe during drilling in undergroundcoal mines, the underground space coordinate system was established, differentialgeometry equation, differential equation of equilibrium, geometry equation, constitutiveequation, equation of vertical and horizontal bending deformation, half wave bendingequation of drill pipe were derived. The formula for calculation of the maximum bendingstress of drill pipe was deduced from the principle of strut stabilization. The constraintrelation of borehole and drill pipe was analyzed.（2）The method suitable to analysis and prediction of fatigue and life of drill pipewas optimized. The mechanism of the generation and extension of fissures due to fatigue ofdrill pipe was analyzed in detail. On the basis of the method for prediction of extension offissures, the formula for fatigue and life of drill pipe was derived.（3）On the basis of the calculation equation of fatigue and life of drill pipe, the t finiteelement software ANSYS Workbench was used to put forward a emulation method forfatigue and life of drill pipe, realizing emulation of fatigue of drill pipe during drilling,providing condition for prediction of fatigue and life of drill pipe.（4）A composed fatigue tester for real torsion of drill pipe of great capacity wasdeveloped, filling the gap in China and abroad. The torque of the tester can be adjustablefrom300Nm to15000Nm, rotation speed is0-800rpm with steeples adjustment. Thetested length of drill pipe is9000mm，providing testing approach for analysis of fatigue ofproducts with long axis.（5）The fatigue test of three sets of drill pipe was conducted under limit conditions.Investigation of drill pipe usage in three coal mines was carried out. The results verified theaccuracy of emulation method of fatigue，checked the research results on prediction offatigue and life of drill pipe, establishing a good basis for prediction of fatigue and life ofdrill pipes of different specifications. |
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