ANSYS Explicit Dynamics is used to analyze high-speed events that occur within extremely short time periods, such as collisions, impacts, drops, crushing, fracture, large deformations, shock, and explosions. According to Ansys, explicit dynamics is a finite element approach that calculates nonlinear, time-dependent behavior using very small time steps. It is especially utilized in applications such as drop tests, vehicle crashes, metal forming, and material failure analyses.
Explicit Dynamics is preferred when an event occurs very rapidly and causes significant deformation within a short duration.
Examples include:
The fundamental concept is simple: the load is not applied gradually; instead, the system is exposed to sudden energy within a very short time.
In Static Structural analysis, loads are generally assumed to be applied slowly and under equilibrium conditions. In Explicit Dynamics, however, time steps and event severity become critically important.
For example, if a vehicle collides with a barrier at 15 m/s, asking only “What is the force in Newtons?” is insufficient. Additional critical factors include:
Implicit analysis is generally used for slowly evolving, equilibrium-based problems and can progress with larger time steps.
Explicit analysis, on the other hand, uses extremely small time steps. Each step is solved rapidly, but millions of steps may be required. Therefore, it is highly effective for short-duration, highly nonlinear, and violent events.
In impact or collision analyses, the following results are commonly evaluated:
Shows how much the component deforms after impact.
Indicates regions exposed to high stress levels.
Used to determine whether permanent deformation has occurred.
Displays velocity changes of components after collision.
Important for understanding shock severity.
Represents the force generated between contacting surfaces during impact.
One of the most critical checks in explicit analysis. Kinetic energy, internal energy, hourglass energy, sliding energy, and eroding energy are monitored.
In Explicit Dynamics, a simple linear elastic material model is usually insufficient. During impact, materials may not only elastically deform but may also crush, plastically deform, tear, or fracture.
Therefore, the following material behaviors may need to be considered:
In high-speed events, the strain rate significantly affects the results. Compared to implicit analyses, explicit material models use highly advanced algorithms.
The general workflow is as follows:
Unnecessary small details are removed. Since excessively small CFL (Courant–Friedrichs–Lewy) values may prevent convergence, features reducing characteristic length are optimized.
Detailed material cards are created because mass, velocity, and energy are critical in explicit analyses.
Finer meshes are used in impact regions. Poor mesh quality may lead to inaccurate deformation or numerical instability.
Contact behavior between components must be defined correctly. Friction, separation, impact, and sliding behavior are determined here.
For example, an impacting body may be assigned a velocity of 10 m/s.
The simulation duration should be short yet sufficient to capture the entire event. For instance, if a collision lasts 5 ms or 0.5 s, the analysis time is adjusted accordingly.
Checking only colorful stress plots is not sufficient. Energy graphs are essential for validating solution reliability.
When interpreting Explicit Dynamics results, energy balance is extremely important.
Initially, the system mostly contains kinetic energy. During impact, this energy transforms into:
If the energy plots are physically inconsistent, the results may appear visually acceptable while still being unreliable.
Evaluates protection plate durability against stone, obstacle, or ground impacts.
Assesses connection points, weld zones, and structural members under sudden impact loads.
Analyzes the behavior of external structures, brackets, or internal equipment under sudden loads in rail systems.
Determines whether industrial machine safety covers remain secure during impacts.
Evaluates post-drop damage risk for electronic enclosures, battery packs, mechanical equipment, or defense industry components.
Examines thinning, wrinkling, and plastic deformation behavior in metal forming applications.
Analyzes delamination, localized damage, and energy absorption in composite structures.
Evaluates deformation, energy absorption, and safety performance when a vehicle impacts a barrier at a specific velocity.
The most severe impact and collision conditions that products may encounter in real-life scenarios can be virtually tested before manufacturing using ANSYS Explicit Dynamics.