Unilateral Multibody Dynamics Modeling and Simulation of Frog-hammer

The modeling and numerical simulation of frog-hammer are typical questions about multibody system dynamics with frictional unilateral constraints. With rational assumptions on frog-hammer and its working environment,simplified multibody model of frog-hammer is established. Dynamics equations are derived by means of Lagrange's equations of first kind. They are constrained by two unilateral constraints with friction. Time-stepping impulse-velocity schemes and corresponding linear complementarity formulas,which is equivalent to the stick-slip transition conditions,are adopted to simulate the whole working process of frog-hammer. The numerical results perfectly depict the stick-slip phenomenon in advancing process and periodic lift off-ramming process. With numerical results,two important frog-hammer performance parameters,i.e.,the advancing velocity of frog-hammer and ramming energy absorbed by the ground per impact,are calculated.