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A three dimensional dynamic elastic-plastic finite element analysis of the interaction ofpercussion bits with rock roasses is presented.The dynamic contact problem was investigated with thenumerical method developed for high velocity impact calculations.The numerical analysis was carried out for three simultaneously loaded percussion bits arrangedon a straight line on the rock surface,the loading time was kept constant throughout this work.Thenumerical calculation for various strengths of the dynamic load on the percussion bits shows that a crit-ical minimum dynamic load exists for the generation of plastic deformations in the rock.For this criti-cal value of the load the maximum normal stress of the longitudinal wave in the percussion bit exceedsthe yield stress of the rock mass.
A three dimensional dynamic elastic-plastic finite element analysis of the interaction ofpercussion bits with rock roasses is presented. The dynamic contact problem was investigated with thenumerical method developed for high velocity impact calculations. The numerical analysis was carried out for three times loaded percussion bits arrangementon a straight line on the rock surface, the loading time was kept constant throughout this work. Chenumerical calculation for various strengths of the dynamic load on the percussion bits shows that a crit-ical minimum dynamic load exists for the generation of plastic deformations in the rock .For this criti-cal value of the load the maximum normal stress of the longitudinal wave in the percussion bit exceedsthe yield stress of the rock mass.