Time Step in Explicit Dynamics - Lesson 2

Unlike implicit methods, explicit time integration methods are conditionally stable, meaning that they are stable only when the time step size is less than a certain limit. In this video, we learn how to calculate this upper limit or the critical time step. We then talk about the ways in which the mesh and the material properties influence the critical time-step. Finally, we discuss ways to manage the critical time step by either manipulating the mesh to ensure that no small elements drive the critical time step size down or by using mass scaling that selectively modifies the density to increase the critical time step size. 00:00 – Intro 00:49 – Conditional stability of explicit analysis 02:06 – Critical time step and CFL condition 02:55 – Characteristic length of an element 04:05 – Dependence of critical time step on material properties 05:46 – Increasing critical time step by modifying the characteristic length 07:15 – Mass scaling 08:05 – Checks associated with mass scaling