SIMPACT: Explicit Dynamic Code for non Linear Structural Analysis

SIMPACT is a finite element computer system developed at the International Center for Numerical Methods in Engineering (CIMNE) in Barcelona, Spain, for analysis of structures subjected to dynamic and impact loading. Typical application of SIMPACT include among others the seismic analysis of structures, the study of structures subjected to internal of external vibrations, the prediction of ship motions originated by waves crashworthiness studies in automobiles, aerospace and maritime vehicles, analysis of structures subjected to blast pressure loading and a wide range of impact problems typical of defense applications.

Reliable computational procedures to predict the deformation of a structure under dynamic impact loading are very complex since consideration must be given to the nonlinearity of the material, as well as other important effects like the unsteady nature of the process, the large magnitude of the strains involved and the importance of frictional effects at the contact interfaces. These analyses justify the use of sophisticated numerical methods and usually lead to the necessity for huge computer resources.

SIMPACT allows accurate computation of the geometrical and mechanical parameters of interest for the dynamic analysis of structures; these include the evolution of the deformation of the structure, the distribution of stresses and strains in the structure, and the frictional contact forces at every instant of the deformation process.

The requirements for the computer simulation of structural dynamic and impact problems using standard implicit codes typically demand significant memory requirements and computer power. The finite element formulation of SIMPACT is based on alternative explicit dynamic integration scheme. Among the distinct advantages of an explicit code are the memory requirements that are typically one order of magnitude less than the implicit case. Also non-linear effects and frictional conditions can be treated in a simpler manner allowing the solution of structural problems of practical size on standard workstations and PC’s.

SIMPACT is equipped with full graphic pre and post-processing tools which facilitate the preparation of geometry analysis data and visualization of results in a user friendly, menu driven environment.

System facilities

  • available on a variety of workstations and PC’s
  • logical and easy-to-use pre and post-processor
  • restart facility
  • control over history of loading
  • comprehensive error and warning messages

Pre- post-processor

  • based on MOTIF or TK
  • graphics library is abased on GL or Open GL
  • associative data structures: when a point is moved, for example, all the associated lines and surfaces are automatically up dated
  • full geometry definition
  • mesh generation
  • complete definition of analysis data
  • interfaces to DXF, FEMVIEW and IDEAS

Geometry definition

  • simple point, line, surface and volume generation
  • based on Coon surface definition which allows simple construction of curved lines and surfaces
  • copy, mirror, translate and rotate geometric features
  • automatic surface creation from line model


  • automatic generation of unstructured 2D triangular, quadrilateral and 3D tetrahedral meshes
  • generation of regular 2D triangular, quadrilateral and 3D hexahedral meshes

Analysis facilities

  • explicit time integration with automatic time stepping
  • includes structural damping
  • large deformation and large strains
  • simple modelling of rigid surfaces
  • concentrated masses

Element types

  • beam elements
  • plane stress/strain quadrilaterals and triangles
  • axisymmetric quadrilaterals and triangles
  • three dimensional hexahedral
  • 3-noded rotation-free shell triangles
  • axisymmetric shell elements
  • rigid surfaces in 2 and 3 dimensions

All elements have been developed specifically for explicit dynamic applications


  • isotropic elastic
  • orthotropic elastic
  • isotropic elasto-plastic with hardening
  • isotropic viscoplastic with hardening
  • stress resultant formulations for beam and shell elements
  • all continuum materials have been formulated for large strain applications

Boundary conditions/Loading

  • contact with friction across boundaries
  • prescribed displacements, velocities and accelerations
  • initial displacements, velocities
  • linear and rigid constraints
  • point, surface and gravity loads
  • initial load state and initial stresses
  • follower loads for large deformations/surface
  • blast loading

Results processing

  • user specified results output
  • graph plotting of quantities along arbitrary lines
  • deformed shape visualization
  • contour diagrams
  • spring back shape
  • vector diagrams
  • animation of results
  • picture files in postscript forma for printing


  • internal QA program
  • usage by industrial companies (CASA, Ital Design, CANDAMAT S.A., etc.)


The following pictures show examples of application of SIMPACT to the following problems:

  • Crash crashworthiness
  • Impact of objects
  • Impact of a pressure wave on a shell structures
  • etc..
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Document information

Published on 14/03/18
Accepted on 13/03/18
Submitted on 13/03/18

Licence: CC BY-NC-SA license

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