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Sensor Definitions in LS-DYNA

Sensors can be used to trigger entities based on certain criteria. The following image is a high-level steps involved to take advantage of sensors in LS-DYNA.

Energy Output to D3PLOT Files

Several options exist in LS-DYNA to output the energies, stress and strain information for shells, solids and beams depending on the choice of parameters in *DATABASE_EXTENT_BINARY keyword. These are important to understand and enable proper postprocessing of the results when using any post-processors to read in D3PLOT. It must also be noted that increased output […]

Accelerometer Mass

Starting 971, LS-DYNA allows the direct input of the physical accelerometer mass in the *ELEMENT_SEATBELT_ACCELEROMETER keyword which is lumped equally to the three nodes that is used in defining the accelerometer. This eliminates the need to create additional *ELEMENT_MASS keywords to account for the physical accelerometer mass.

Nodal Time History in Local Coordinate System

In several simulations, the response of a nodal point (displacement, velocity, and acceleration) is helpful to be output in a user-defined local coordinate sytem. LS-DYNA offers several options to enable the local system output of nodal time history data and here are some examples of it. All nodal time history data is output to either […]

Principal Stress Calculator for Shell Elements in DYNAIN File

Recently, there was a request to ouput the principal stresses for each element at lower and upper surfaces of each shell element in DYNAIN file to use in some failure theories. I beleive this feature is a routine output in PamStamp simulations. To enable this, the attached ‘C’ code can be used that reads in […]

Monitoring Incremental Elapsed Time as a Function of Simulation Time

When running explicit simulations in LS-DYNA, it is very important to understand the total CPU clock and the total Elapsed time used by the solver. This information is available at the bottom of every D3HSP file written by LS-DYNA as shown below. The total elapsed time reported in the file is the difference between the […]

Mapping of Deformed Nodal Coordinates for SubSystem/Component Analysis

Several analyses sometimes requires the mapping of nodal positions (coordinates) from a previous run for use in current run. For single component this is a rather easy task since it just involves writing a DYNAIN file for part(s) of interest using *INTEFACE_SPRINGBACK_LSDYNA keyword which would consist of final deformed nodal coordinates and element history variables. […]

Number of Shell History Variables in *INTERFACE_SPRINGBACK

*INTERFACE_SPRINGBACK provides an easy way to store a part’s state at the end of a simulation for later use. The part’s state consists of element history variables such as stress and strain tensor (in the form of *INITIAL_STRESS/*INITIAL_STRAIN) and also nodal values such as its final coordinates (*NODE). Optionally, when using the THICKNESS option, it […]

Built-In Filtered Nodal Acceleration Output Using IACCOP in *CONTROL_OUTPUT

Starting in LS-DYNA v971, nodal accelerations can be filtered before being output to the ASCII file “NODOUT”. The type of filter can either be a built-in filter based on low-pass Butterworth frequency filter or can be user-defined. The filtering process is turned on by setting the IACCOP=2 in *CONTROL_OUTPUT keyword. The filtering process works by […]

Contact Force Output to RCFORC

The ASCII file “RCFORC” contains the incremental forces contributed by contact algorithms. Due to the nature of the contact-impact interactions, the raw output tends to be very noisy and is of little value. To eliminate the inherent noise in the contact force output, LS-DYNA averages the force magnitude over the preceing output interval which results […]

Use of *SENSOR in LS-DYNA 971

A powerful new feature available in LS-DYNA version 971 is the *SENSOR keyword. To briefly summarize the Keyword Manual description, *SENSOR allows boundary conditions and various model entities to be activated/deactivated based on element, force, and/or node based criteria. Options are available for modeling very elaborate systems, but we will focus on a very simple […]