Research on prediction method of horizontal cutting force of chisel pick based on upper bound theorem of limit analysis

The wheel bucket excavator is the key mining equipment in the continuous process system of open-pit coal mines, pick design and cutting force prediction are key technical problems in the development of wheel bucket excavators. In order to guide the mechanical design of wheel excavators, optimize the design of bucket picks, and more accurately predict the cutting resistance of wheel excavators during mining, an upper limit method for the horizontal cutting force of chisel picks is proposed based on the limit analysis theory. The upper limit method is based on the flow law associated with the Coulomb yield criterion and establishes a rotary motion mechanism with a logarithmic spiral as the failure surface; by equating the input load power with the energy dissipation rate of the failure zone, the horizontal cutting force expression of the chisel pick is derived; The horizontal cutting force coefficient diagram is obtained through numerical derivation, which shows the influence of the cutting rake angle and the internal friction angle of the rock on the horizontal cutting force of the chisel pick, and simplifies the prediction calculation of the horizontal cutting force of the chisel pick. Different from the chisel pick tensile or shear failure model based on the mechanical analysis of chip-pick interaction, the advantage of the upper limit method is that there is no need to assume the stress distribution on the failure surface. Seven sets of experimental data are used to compare and verify the prediction results of the upper limit method and other traditional methods. The results of 14 statistical indicators show that the upper limit method is similar to the semi-empirical method and Evans method in terms of prediction accuracy, and is better than the Nishimatsu method. The effectiveness and applicability of the upper limit method to the horizontal cutting force of rock cutting with chisel picks is verified. The prediction performance of the upper limit method can be improved by considering the three-dimensional failure motion mechanism and using the flow law of stretch truncation.