Viewing Contact Frictional Energy

When friction is enabled in contact treatment using static or dynamic fricition coefficients (FS, FD in *CONTACT), the energy dissipated due to friction can be recorded and visualized. The parameter that tells LS-DYNA to ouput the frictional energy is FRCENG in *CONTROL_CONTACT. FRCENG by default is set to 0 to ignore the recording and output…

December 14, 2010 | by

Thick shells in contact

During one of my recent trips, a question was raised about how LS-DYNA treats thick shells in contact in particular if the contact would detect the surface sides. This simulation Thickshells in contact shows that LS-DYNA treats the thickshells as solids in which all external (free) surfaces are included in the contact. ERODING contact would…

August 13, 2010 | by

Tolerance used for Tying Slave Nodes in TIED contacts

TIED contacts help “bond” two surfaces of different mesh densities. When using the default constraint method, the projection distance of the slave node onto to the closest master segment must be zero and this is achieved by LS-DYNA by updating the slave node coordinates such that it lies on the master surface. This coordinate update…

October 15, 2008 | by

Effects of Initial Penetrations

It is well known that the presence of initial penetrations can spoil the accuracy of the analysis. A few days ago, while working on ODB barrier, some strange spikes in energies was suspicious even with IGNORE turned on. To understand this, I simply did a simple shakedown and generated some 100 d3plots to capture the…

August 10, 2008 | by

Internal Contact for Solids using *SET_SEGMENT_GENERAL

In an earlier post on CONTACT INTERIOR , we saw how adding interior contact can help prevent negative volumes. An additional method that is available in LS-DYNA is the use of SET_SEGMENT_GENERAL to generate the interior segments of solids. When a list of parts are defined using PART_SLDIO in the SET_SEGMENT_GENERAL, LS-DYNA generates both external…

March 20, 2008 | by

TIEBREAK Example

Here is a TAR file that consists of a simple setup to demonstrate TIEBREAK interface contact in LS-DYNA. The example can be used under TENSION, COMPRESSION, TORSION and PEELING type of load. acumulatori camere constructii interioare avion romania spania cablu electric camera digitala canon componente motor sofer curier plante de decor excursii roma montaj faianta…

March 10, 2008 | by

Interior Contact for Foams, Honeycombs and Rubbers to eliminate Negative Volumes.

Under large compressive forces, elements belonging to either Foams, Honeycombs and Rubbers tend to invert causing numerical instabilities. To avoid such difficulties, which is one of the primary causes of simulation waste (unusable simulation results), a good set of modeling practices are first necessary as outlined in an earlier post . As an added protected…

January 24, 2008 | by

CONTACT_AUTO_MOVE to eliminate initial contact clearances

In many situations, initial clearances between two contact surfaces can cause convergence issues in IMPLICIT analyses while wasting simulation time in EXPLICIT analyses. To remove the initial contact clearance, LS-DYNA offers a capability using *CONTACT_AUTO_MOVE that helps to improve convergence in IMPLICIT analyses since contact is detected immediately. Contact AUTO_MOVE associates itself with another contact…

January 10, 2008 | by

Contact and Global Timestep

You may have seen this popular message that is printed out by LS-DYNA for every simulation. The LS-DYNA time step size should not exceed 0.456E-06 to avoid contact instabilities. If the step size is bigger then scale the penalty of the offending surface Lets review this to understand a little more. As we know, Explicit…

November 1, 2007 | by