2010 Volume 66 Issue 2 Pages 299-311
In the DDA, the contact spring are introduced between the blocks contacting each other to prevent the penetration of the blocks but the dashpots are not usually introduced unlike DEM. However, it is well known that the numerical damping caused by numerical integration occurs during the simulations. In this study, the characteristics of numerical damping caused by Newmark β method in DDA was investigated using simple 1-D free oscillation problem. The 1-D collision problem was analysied using DDA with 3-D rigid sphere block and sensitivity analysis for the parameters related to Newmark β method was carried out. The effect of these parameters on the numerical stability and accuracy was also discussed. From the analytical results, in DDA, the calculation time step, Δt and natural frequency, T should satisfy the condition of Δt/T<0.05 to obtain the results with good accuracy. To evaluate the energy loss correctly when the two blocks collide each other, the effect of numerical damping and velocity ratio should be considered separately.
