UM Loco  /  CONTACT add-on

CONTACT add-on

The CONTACT add-on for UM is a version of CONTACT that is integrated seamlessly into Universal Mechanism. This provides the option to simulate vehicle dynamics using CONTACTs detailed contact algorithms. Including the full non-Hertzian geometry instead of relying on Hertzian theory or the Kik-Piotrowski algorithm, and using full linear elasticity instead of FASTSIMs simplified theory.

The CONTACT add-on is included in the dynamic integration loop. It completely replaces the simplified algorithms. This way, one may study derailments using the full CONTACT model and compare with simplified algorithms. The calculation time is controlled effectively by varying the discretization accuracy.

Fast wheel-rail contact algorithms like FASTSIM make simplifications in order to achieve good calculation speed. This introduces inaccuracies that may exceed 50% in non-Hertzian circumstances. This may be unacceptable in critical scenarios like the investigation of derailments or the detailed study of wear and RCF. For those cases the CONTACT add-on is a valuable alternative. This provides Kalker’s variational theory (non-Hertzian geometry, linear elasticity) with Vollebregt’ solver algorithms. The CONTACT add-on is fully integrated in the UM solver, replacing the existing contact algorithms in the vehicle dynamic calculations, and is operated entirely automatically.

istory Main benefits


  • seamlessly integrated in the vehicle dynamic simulation;
  • easy access to Kalker’s non-Hertzian theory;
  • validation of results of simplified theories;
  • assessing the contact area and peak stresses causing damage phenomena.
istory Capabilities


The add-on takes care of all the preparations that are required:

  • determining the initial contact point(s) between wheel and rail;
  • defining a local coordinate system;
  • computing the initial penetration of the undeformed profiles;
  • computing the creepages.

The contact results then include:

  • the location of the contact patch(es) w.r.t. the wheel and the rail;
  • the contact angle and creepages;
  • the size of the contact, adhesion and slip areas;
  • the contact forces, normal and tangential, according to Kalker’s theories;
  • the maximum pressure, maximum shear stress and the wear number.
istory How to get a license


Licenses for the CONTACT add-on for UM are provided and supported by VORtech CMCC, You can request a trial license by e-mailing to In your e-mail request please specify your name, position and company/university.

istory Samples


"CONTACT" vs. "Kik-Piotrowski + FASTSIM" models
Normal force
Longitudinal creep force
Lateral creep force
Contact patch and lateral force distribution
Animation of contact patch