Engineering service
Impact, Drop and Blast Analysis (Explicit Dynamics FEA)
When a load lasts milliseconds, a static check is not enough. SLETEC uses explicit dynamics FEA to predict how equipment, structures and protective systems respond to impact, drop and blast — with documented assumptions, energy checks and acceptance criteria.
Last updated: 2026-11-06
When you need explicit analysis
- Equipment or skids that may be dropped during lifting, transport or installation, where mounting-point g-levels must be checked.
- Structures exposed to accidental impact — crane strikes, dropped objects, vehicle impact.
- Protective structures and barriers that must arrest a moving object, including perimeter and aerial (counter-UAV) barrier systems.
- Components that must resist blast pressure and impulse at a defined stand-off distance.
- Materials and joints where large deformation, contact, strain-rate effects and failure govern the result.
How we run an impact or blast study
- Design basis — impactor mass and velocity or charge mass and stand-off, impact angles, materials, acceptance criteria. Values the client must confirm are logged as hold points.
- First-order checks — hand calculations of kinetic energy (E = ½mv²), momentum, mean arrest force versus stroke, and scaled distance (Z = R / W1/3) for blast. These set up the model and are used to cross-check the solver.
- Model — geometry from the client's drawings or a Tekla / CAD model; mesh refined at the contact zone; frictional contact; non-linear material models with strain-rate effects and element erosion where failure is expected.
- Loading — initial velocity for impact and drop cases; CONWEP-based blast loading (for example LS-DYNA *LOAD_BLAST_ENHANCED) or coupled ALE where the problem needs it.
- Quality checks — energy balance, hourglass and contact energy limits, mesh sensitivity and comparison with the hand calculations.
- Report — deformation, stress and plastic strain histories, support and anchor forces, accelerations at equipment mounting points, pass / fail against the agreed criteria, and recommendations.
Evidence from SLETEC projects
| Study | What was analysed | Key output |
|---|---|---|
| Oblique impact on bolted plates (Ref. 82) | Projectile at 800 m/s striking a two-plate Steel 4340 bolted assembly; Ansys Explicit Dynamics with element erosion | Perforation of both plates within 0.15 ms; peak von Mises 1.23 GPa; max. equivalent plastic strain 0.968 |
| Skid drop response | Corner, edge and flat drop cases in LS-DYNA with frictional contact | Mounting-point acceleration histories checked against the equipment g-limit; local permanent deformation |
| 40 m structural tower | Wind, response-spectrum seismic and accidental crane-impact response | Modal frequencies, member, bolt, weld and anchor forces, global drift |
See the explicit dynamics impact project for images and the full description.
Aerial and perimeter barrier engineering
Rope-and-net barriers that protect critical facilities from UAV (drone) impact combine several disciplines. SLETEC can deliver them as one package:
- Explicit FEA of the net, rope grid and posts under normal and oblique impact, followed by the blast load case.
- Design of lattice towers, ropes and connections to AISC 360 and the Saudi Building Code, with connections checked in component-based FEA.
- Foundation and anchor-bolt design.
- A detailed 3D model in Tekla Structures that feeds the FEA, the fabrication drawings and the Material Take-Off.
- A compliance report against the client's engineering requirements.
Threat values, acceptance criteria and site data are always taken from the client's approved specification and are treated as confidential.
Software
LS-DYNA and Ansys Explicit Dynamics for transient analysis; Ansys Mechanical for static and modal checks; Tekla Structures and STAAD.Pro for structural design. All analysis runs in-house; project data is not uploaded to cloud services.
Frequently asked questions
- What is explicit dynamics FEA?
- Explicit dynamics is a time-stepping finite element method for very short events — impact, drop, crash and blast — where large deformation, contact, strain-rate effects and material failure must be captured. Static FEA cannot represent these effects.
- Which software does SLETEC use for impact and blast analysis?
- LS-DYNA and Ansys Explicit Dynamics, with Ansys Mechanical for supporting static and modal checks.
- Can SLETEC design UAV (drone) protection barriers?
- Yes. SLETEC can carry out the explicit FEA for UAV impact and blast, design the towers, ropes, connections and foundations, and issue fabrication drawings and MTO, working to the client's approved specification.
- How do you make sure an explicit FEA result is reliable?
- We check energy balance, hourglass and contact energy, mesh sensitivity and compare the solver results with first-order hand calculations of energy, arrest force and blast pressure before reporting.
- Can you analyse a skid drop during lifting or transport?
- Yes. We model corner, edge and flat drops, report acceleration histories at equipment mounting points and compare them with the equipment g-limit.
Start a project
Send your scope, drawings, codes and schedule to enquiry@sletec.com or WhatsApp +966 55 545 8298. An engineer usually replies within 24 hours.
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