Advanced methods for drop test
Ivan Mosa
James Kennedy
Dear Ivan,
Perhaps of some interest:
https://lsdyna.ansys.com/package-drop-test/
Several methods to represent fluids exist within LS-DYNA. Apart from the ICFD, ALE and CESE
solvers, there are also meshless methods that can be used. For this case study, it has been chosen to
explore the performances of the SPH and DES methods. The ability of SPH to represent fluids has
been explored in other case studies on this site, e.g. a tank sloshing example, whereas the abilities of
the computationally efficient DES solver are perhaps more unknown.
Fluid representation
Starting with the SPH description of the fluid, this input is rather straightforward. Physical properties
are assigned, viscosity and density on *MAT_NULL and speed of sound for water on e.g. *EOS_
GRUNEISEN. A standard node-to-surface contact can be used for the contact with the carton, in this
case it has been chosen to model it without friction or damping. Generation of the SPH particles is also
a simple operation through the use of the SPH generation tool in LS-PrePost shown on the right hand
side.
In the DES (Discrete Element Spheres) method, the bulk behavior of a material is entirely described by
the interaction between rigid spheres. By changing the friction, rolling friction and cohesion between the
particles, different bulk behavior can be achieved. In this case study, water-like properties have been
achieved by setting the friction between the particles very low.
Sincerely,
James M. Kennedy
KBS2 Inc.
February 19, 2026
p.s.
Ansys LS-DYNA is considered an industry-standard and highly effective tool for drop test simulations, particularly for modeling nonlinear, short-duration, high-impact events with complex contact and material behaviors. It enables designers to identify critical structural areas, predict failure, and validate product integrity, frequently used in industries for drop, impact, and crash testing.
Ansys +4
Why LS-DYNA is a Good Approach for Drop Tests:
· Explicit Solver Strength: Optimized for short-duration dynamic simulations where materials experience significant deformation and nonlinear behavior.
· Robust Contact Modeling: Effectively manages complex, multi-component interaction during impact and rebound.
· Industry Standard: Widely used for simulating product drops, such as consumer electronics or automotive components, ensuring reliable results (e.g., MIL-STD 810).
· Multiphysics Capability: Features like Arbitrary Lagrangian-Eulerian (ALE) can handle complex scenarios, such as liquid-filled containers, allowing for specialized modeling of fluid-structure interaction (FSI).
· Versatile Material Models: Supports a vast library of material models to accurately represent metals, polymers, composites, and foams under high-strain rates.
Reddit +7
Key Considerations for Successful Simulations:
· Mesh Quality: Proper meshing, especially around impact zones, is critical for accurate stress analysis.
· Time Step Management: Due to the explicit nature, selecting appropriate time steps and using mass scaling to manage runtimes without compromising accuracy is essential.
· Simulation Setup: Setting up proper boundary conditions, contact interactions, and accurately modeling the impact surface are crucial for valid results.
· Cost and Learning Curve: While powerful, LS-DYNA can be expensive and requires a higher level of expertise compared to some other simulation software.
Reddit +4
https://lsdyna.ansys.com/drop-test/
Example showing a drop test load case. A deformable body is dropped on a rigid wall.
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