Regularities of contact interaction of small-sized supporting elements of walking machines with weakly bearing soils

Abstract

The results of finite-element modeling of the mechanics of contact interaction of small-sized support elements (feet) of walking machines with weakly bearing soils are discussed. A flat contact task is formulated for rigid feet of a rectangular shape interacting with an elastoplastic supporting surface. Nonlinear models of soil behavior under loading were used. A two-stage iterative algorithm for solving the non-linear problem in the computer system of finite element analysis ANSYS is implemented. The task was solved under conditions of large deformations of the supporting surface. The simulation results showed that a sufficiently large amount of soil is loaded during the interaction of a small foot with a supporting surface. Under normal loading, the greatest stresses and strains occur directly under the foot. Here may be the destruction of the soil. At a standardized depth of 0,5 m, the stress decreases. The top layer of soil remains lightly loaded. In addition to vertical deformations, there is a «squeezing» of soil to the right and left from under the foot. With a tangential load, the stress and strain fields lose their symmetrical nature. The zones of greatest equivalent stresses and strains are shifted towards the action of the tangential load. The greatest ground stresses occur under the foot and on the lateral surface of the foot. In the direction of the tangential load, the entire mass of the soil, including its upper layers, is substantially loaded. Near the foot, in the zone of greatest stresses, a characteristic area appears, where the soil is squeezed up. Here the reverse process of compaction of the soil takes place. It is shown that the use of feet with a small supporting surface leads to an undesirable increase in soil stresses in the contact zone. On the other hand, in small feet, there is a decrease in the soil compaction zone and its upper layer is less loaded. Also, for small feet, the supporting surface is used more efficiently - the stresses along its length are distributed more evenly, and the side surface acts as a grouser.