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Objexx Engineering

ObjexxSISAME Modeling Overview

ObjexxSISAME (Structural Impact Simulation And Model Extraction) is a unique and powerful system for vehicle crash modeling and safety design. The ObjexxSISAME Suite provides a sophisticated approach to the generation and simulation of efficient, accurate dynamic structural impact models. ObjexxSISAME can perform one-step structural design optimization to best achieve a desired crash performance subject to structural and cost constraints. ObjexxSISAME complements the detailed analysis abilities of finite element modeling with a direct design capability.

ObjexxSISAME extracts optimal lumped-parameter models that best reproduce observed or desired crash behavior. These models consist of rigid mass elements and massless load-paths. ObjexxSISAME models of modest granularity have a high degree of expressive power and can accurately characterize crash responses. More information on ObjexxSISAME's optimal model extraction can be found on the system identification page.


Applications for ObjexxSISAME modeling include:

  • Optimal structure redesign to meet a safety performance standard subject to structural and cost constraints.
  • Predictive simulation of crashes at other speeds or impacting other vehicles.
  • Tuning finite element models to improve conformance to measured test data.
  • Distillation of finite element models for efficient simulation of a matrix of events.


ObjexxSISAME provides many capabilities to make modeling efficient and successful.


  • 1, 2, and 3 dimensional models are supported.
  • Structural and mass properties can be extracted from test or FEA data.
  • Link (load-path) elements support axial, torsion, bending, and relative rotation loading properties.
  • A range of elastic and inelastic static link loading types is available.
  • A range of magnifier and damper dynamic link loading types is available.
  • Multiple event extraction is supported to extract models that are optimal for a set of impact types and speeds.
  • ObjexxSISAME is a high-performance C++ application with a state-of-the-art object-oriented design that facilitates rapid development of new capabilities.
  • There are no fixed size limits in ObjexxSISAME.
  • A range of output types is supported including signal files, tables, measure-of-fit reports, and visualizations.


  • Model configuration display and real-time simulation visualization is provided using the OpenSceneGraph library built on OpenGL® technology. Models can be examined using mouse-controlled zoom, rotate, and pan support. Samples of the OpenSceneGraph images can be viewed on the ObjexxSISAME Real-Time Visualization page.
  • High-quality ray-traced  POV-Ray™ animation frames can be generated during a run with user control over camera placement and frame rate. Multiple animations can be generated during a run. Scripts are provided to automate generation of the frame images, which can be viewed as or turned into movies. Animations can be post-processed using a provided script to generate alternative views.
  • Animations of extraction events can include an overlay of the actual and extracted model positions.


  • ObjexxSISAME uses YAML-style input files that are human readable/editable and self-documenting.
  • Extensive input checking is performed and error messages are clear and specific.
  • Input check only "test" runs can be performed during model development.
  • The ObjexxSISAME console provides progress and status information during a run.
  • Every run creates a log file with a summary of the run and any tabular output requested.


The original SISAME technology was developed by Objexx Engineering's principal for the U.S. Dept. of Transportation, National Highway Traffic Safety Administration (NHTSA) for car crash model parameter identification and simulation. ObjexxSISAME extends the SISAME concept into a fully graphical workbench for design and simulation of a wide range of structural systems during impact and other events.


Objexx offers the ObjexxSISAME Suite and provides ObjexxSISAME training, modeling, and customization services to clients in the structural modeling and automotive safety communities.