Research On Numerical Simulation Of Cutting Of Soft Rock And Clay With Plane Tine Cutters

With the continuous progress of modern science and technology,our fundamental construction is developing toward large-scale,mechanization and intelligentization.The demand for high-performance cutting equipments for rock and soil cutting is very urgent.Carrying out the study of simulation of rock and soil cutting is of great significance for design of new type cutting equipments.In this paper,the cutting of soft rock with low uniaxial compressive strength and clay with high water content by plane tine cutters are studied.Simulation methods which are suitable for simulating the deformation characteristics and failure modes of the cutting media are established.Firstly,the direct simulation of rock excavation process of the cutterhead of dredger is achieved.The effectiveness of the simulation method of rock cutting by cutterhead is verified through experiments.Problems of discontinuities of rock and dynamic contact determination are solved.The rock excavation process of"contact-deformation-damage-fragmentation-recontact"is completely simulated.Results show that when uniaxial compressive strength of rock or transverse velocity of cutterhead increase,the cutting forces,torque and power of cutterhead increase significantly.When rotational velocity of cutterhead increases,the power of cutterhead increases,but the torque and cutting forces of cutterhead decrease.In addition,it is conducive to reducing cutting specific energy if transverse velocity is increased or rotational velocity is decreased properly.Then,a novel 2D clay cutting simulation method including Eulerian boundaries is proposed.By introducing Eulerian boundaries,the cutting process of clay by cutting tool is transformed into the flow process of clay around a stationary cutting tool.Thus the mesh distortion problem is solved.A 2D clay cutting model which fully combines the merits of both the Lagrangian and the Eulerian descriptions is established.The large deformation of clay around the tool and unrestrained deformation of the free surface of clay are simulated simultaneously.No element is deleted and thus the complete contact surface is retained.Results of soil deformation and cutting forces obtained by simulation are very close to the results of experiments.Results show that when the cutting angle increases,the cutting force,the plastic deformation of soil,the thickness of soil chip and the ratio of soil chip thickness to cutting depth increase,but the failure angle of soil decreases.When the cutting depth increases,the cutting force and soil chip thickness increase,but the plastic deformation of soil,the ratio of soil chip thickness to cutting depth and the failure angle of soil have no significant changes.Finally,direct simulation of 3D clay cutting process considering lateral soil failure is achieved.Experiments are carried out and the effectiveness of the coupled Eulerian-Lagrangian finite element method is verified.The soil is represented by a material region adopting pure Eulerian description and thus the deformation of soil is no longer constrained by mesh.The dynamic contact between Eulerian material and Lagrangian tool is realized based on enhanced immersed boundary method.The complete clay deformation process of“front bulge-lateral split-chip formation”is simulated.Both experiment and simulation results show that the cutting force increases significantly with the increase of the cutting depth,but there is no significant change in cutting force when the cutting angle varies in the range of 30°to60°.For plane cutting tools,the minimum width to depth ratio for simplifying 3D clay cutting problem to 2D problem is proposed to be R_min=3.In addition,through simulation of clay cutting process of a curved moldboard plough,the applicability of coupled Eulerian-Lagrangian finite element method to 3D clay cutting simulation for complex curved tools is further validated.