Estimation of energy losses due to elastic wave emission during operation of a dynamic plow

Abstract

When rock is broken up by the cutting head of a dynamic plow, a part of the impact energy is expended on the generation of elastic waves which are attenuated as they travel through the rock. The energy carried by the elastic wave is lost unproductively in the rock, and the magnitude of the loss depends mainly on the strength parameters of the rock, together with its fracture parameters and the total energy of the impact.in bench tests of a powerful dynamic plow on a coal-cement block, we made special investigations in order to estimate the amount of energy expended on generation of an elastic wave for various impact energy values. For this purpose, in the coal-ce~nent block at various distances from the cutting edge of the head of the plow, we measured the intensity of the elastic wave emitted at impact.The stresses in the wave were rectxded with specially developed three-component temometric gages fixed in the block. Each gage was a cube, 60x 60x 60 mm in size, made of strong cement. In the cube was embedded a shaped steel p.late, to which wire strain gages were glued in three planes and carefttlly insulated. Before being fixed in the block, each cube was calibrated in a press. The signals from tlm strain gages were amplified by a UTSI-VT-12 rensometric amplifier (transmission band 0-7 kI-Iz) and recorded on photographic paper by a K-10fi oscillograph.The fracture parameters of the rock at the time of the measurements were as follows: the thickness of the plowed slice varied between 15 and 20 cmi the angle of attack of the blade was 10"; and the total impact energy for one blade varied between 200 and 700 kg-rn. The resistance of the coal-cement block to fracture Ok) was found with the aid of an SDM dynamometer drill, and averaged 240 kglcm. The scheme of the measurements is t ~,~Y ~ ~=2o cm l~s;l-VZ-19 ~=={KsI~

Mechanical-impedance method in research on the interaction between a powerful activated plough and solid coal

“…According to estimates made by us [6], 10-16%of the entropy is expended on exciting an elastic wave in the rock. An appreciable effect must be exerted by mechanical resistance in the form of viscous friction, which is proportional to the speed of penetration.…”