MTA and METRA Using Ansys LS-DYNA and Autodyn to Simulate Blast Effects

Pic. 1: Experimental setup (a) general view, (b) piezoelectric acceleration sensor position, (c) comb-type device position and (d) cylinder charge of HITEX® [6]

Task Description

The Military Technical Academy “Ferdinand I” and the Military Equipment and Technologies Research Agency conducted a comparative study to evaluate the structural response of an armored sled exposed to a blast generated by a C4 explosive charge. The physical experiment involved a steel sled moving on four sliding rails, equipped with a perforated metallic plate designed to mitigate the upward impulse transmitted from the detonation. The C4 charge was placed centrally, just below the base of the sled, and the blast effects were captured via high-speed video and acceleration sensors.

Pic. 2: Device model in Impetus (up) and Ls Dyna (down)

The goal was to understand the deformation mechanisms and to quantify the effectiveness of the perforated plate in reducing the impulse transmitted to the structure. The experimental data served as a benchmark for validating numerical simulations, with a specific focus on residual deformation, motion profile, structural acceleration, and transmitted impulse. To support future use of virtual testing in armored vehicle design, the study compared three simulation environments: Ansys Autodyn, Ansys LS-DYNA, and Impetus AFEA, analyzing each tool’s ability to model the nonlinear, transient, and high-rate dynamics of the blast event.

Pic. 3: Device model in Autodyn

Solution

To replicate the experimental blast scenario in a virtual environment, the research team developed three distinct simulation models using Ansys Autodyn and Ansys LS-DYNA, leveraging their respective strengths in handling nonlinear dynamic events and multi-material interactions.

In Ansys Autodyn, the simulation setup involved:

• Eulerian formulation to model the explosive charge and surrounding air, capturing the detonation wave propagation and interaction with structural elements.
• Lagrangian solids for the sled, mitigation plate, and support structure, allowing accurate representation of material deformation and contact behavior.
• The use of material models such as the Jones–Wilkins–Lee (JWL) equation of state for C4, and Johnson–Cook plasticity and failure models for the steel components.
• An embedded fluid-structure interaction (FSI) approach to resolve the transfer of energy from the explosion gases into the structure.

Pic. 4: Accelerations measured in armour perforated tests

• A pure Lagrangian approach, modeling both the blast loading and structural response within a single domain.
• Airbag models and CONWEP blast loading options were explored as alternative blast input strategies, but direct pressure application based on physical charge mass and stand-off distance was ultimately selected for highest fidelity.
• Detailed contact definitions (AUTOMATIC_SURFACE_TO_SURFACE and TIED contacts) and hourglass control were used to ensure numerical stability during the large deformation phase.

Both simulations were calibrated using the experimental boundary conditions, including friction from the sliding rails and initial sled position. Meshing was performed using Ansys ICEM CFD, with refinement in critical areas such as the perforated mitigation plate and weld zones. Time-step control was enforced via explicit integration schemes with automatic load stepping to prevent instability.

Comparative analysis was carried out on:

• Residual deformation of the sled floor and mitigation plate.
• Vertical displacement and velocity curves for the sled center of mass.
• Acceleration peak values and duration, for correlation with sensor data.
• Impulse transfer calculated as the integral of force over contact duration.

Pic. 5: Deformation of lower plate center in Impetus, Autodyn and LsDyna vs. test

Benefits

The use of Ansys Autodyn and LS-DYNA in the simulation of the blast event yielded several technical and operational advantages:

High correlation with experimental results:

• In Autodyn, the maximum residual deformation of the sled floor matched experimental measurements within 4%.
• LS-DYNA produced nearly identical results for center of mass displacement and sled acceleration profile, with deviations under 5 ms in timing and under 6% in peak acceleration.

Impulse transfer accuracy:

• Both tools predicted the vertical impulse transmitted to the sled with less than 7% error, validating the simulation approach for future armor design studies.

Pic. 6: Comb-type device position (up) Comb-type device deformation (down)