You can perform a transient Explicit Dynamics analysis in the Mechanical application using an Explicit Dynamics system. Additionally, the LS-DYNA system is available to analyze a model using the LS-DYNA solver. Unless specifically mentioned otherwise, this topics in this document address both the Explicit Dynamics and LS-DYNA systems. Special conditions for LS-DYNA are noted where pertinent.

An Explicit Dynamics analysis is used to determine the dynamic response of a structure due to stress wave propagation, impact or rapidly changing time-dependent loads. Momentum exchange between moving bodies and inertial effects are usually important aspects of the type of analysis being conducted. This type of analysis can also be used to model mechanical phenomena that are highly nonlinear. Nonlinearities may stem from the materials, (for example, hyperelasticity, plastic flows, failure), from contact (for example, high speed collisions and impact) and from the geometric deformation (for example, buckling and collapse). Events with time scales of less than 1 second (usually of order 1 millisecond) are efficiently simulated with this type of analysis. For longer time duration events, consider using a Transient analysis system.

The time step used in an Explicit Dynamics analysis is constrained to maintain stability and consistency via the CFL condition; that is, the time increment is proportional to the smallest element dimension in the model and inversely proportional to the sound speed in the materials used. Time increments are usually on the order of 1 microsecond and therefore thousands of time steps (computational cycles) are usually required to obtain the solution.

An Explicit Dynamics analysis typically includes many different types of nonlinearities including large deformations, large strains, plasticity, hyperelasticity, material failure etc.

An Explicit Dynamics analysis can contain both rigid and flexible bodies. For rigid/flexible body dynamic simulations involving mechanisms and joints you may wish to consider using either the Transient Structural Analysis or Rigid Dynamics Analysis options.