Explicit Dynamics Analysis is a finite element method used to simulate fast events such as impacts, collisions, explosions, penetrations and metal forming that occur within milliseconds or microseconds. With the ANSYS software distributed in Turkey by FE-TECH Advanced Engineering (Mechanical Explicit Dynamics, LS-DYNA, Autodyn, Ansys Forming), you can analyze these complex processes reliably and quickly. This article covers all fundamental principles of the explicit approach, practical tips and its relationship with the ANSYS ecosystem.
This method solves the equations of motion using explicit time integration. Without solving a global system of equations, the next step is directly computed from current values. It is used to simulate short-duration and highly-contact events.
Explicit Dynamics Analysis is suitable for short-duration loads, large deformations, complex contacts and rate-dependent materials. Implicit Dynamics Analysis is preferred for long-duration, quasi-static, small to moderate deformation and linear/mildly non-linear problems.
In explicit analysis, the time step is conditionally stable and the critical time step is calculated by Δt ≈ Lmin / c. For steel with 1 mm element size, the critical time step is about 0.19 μs.
Johnson–Cook, Cowper–Symonds, Mooney–Rivlin, Ogden, Hashin and Puck models as well as foam/cellular structures and energy-based damage criteria can be used.
Solid, shell, beam/rod, SPH and Eulerian elements can be used. Hourglass energy should not exceed 5–10% of the total internal energy.
Automatic surface–surface or node–surface contact; penalty or kinematic approach; static/dynamic friction coefficients and contact stiffness should be set properly.
Mass scaling is used to increase the time step. Hourglass control and artificial viscosity can also be applied for stabilization.
Kinetic energy gradually converts into internal energy. Hourglass and contact energies should remain a small percentage of the total energy.
Drop tests, vehicle safety, explosion and shock, penetration, metal forming.
Mechanical Explicit Dynamics (inside Workbench/Mechanical), LS-DYNA (advanced explicit solver), Autodyn (explosion/shock and ballistics), Ansys Forming (dedicated to sheet metal forming).
Explosion / shock / fluid–structure interaction: Autodyn; Full vehicle crash / spot weld: LS-DYNA; Drop test / basic penetration: Mechanical Explicit Dynamics; Sheet forming: Ansys Forming.
Models can be transferred from Mechanical to Autodyn or LS-DYNA. In LS-DYNA, commands such as *MAT* and *CONTACT* can be customized with Keyword Snippet.
LS-DYNA solutions require a separate license. Mechanical Explicit is included in ANSYS Mechanical license. Autodyn and Forming have their own license packages.
1. Drop Test (phone box) quick setup with Mechanical Explicit Dynamics.
2. Cabin Explosion Analysis in Autodyn with explosive EOS + air Euler + structure Lagrange.
3. Vehicle Subsystem Crash with LS-DYNA using general CONTACT and spot weld models.
4. Deep Drawing with Ansys Forming including springback and formability prediction.
Applying slow loads quickly with explicit leads to spurious inertia effects. Solution: ramp the load gradually. Very fine mesh reduces time step. Solution: local mass scaling. High hourglass energy means improve control. Contact bouncing means adjust stiffness and friction parameters.
Is the unit system consistent? Has critical time step and mass scaling been checked? Is hourglass energy under 5–10%? Is the energy balance reasonable? Is contact penetration acceptable? Has a mesh sensitivity study been performed?
FE-TECH Advanced Engineering is the distributor of ANSYS software in Turkey. We provide training, installation and technical support on LS-DYNA, Autodyn, Mechanical Explicit Dynamics and Ansys Forming solutions. We have contributed to dozens of projects in the defense, automotive, machinery and manufacturing sectors.