Attached is a simple Excel sheet that can be used to quickly evaluate the timestep calculated by LS-DYNA for solids, beams and shells. It must be noted that for solid elements, Q is based on the C1 (default = 0.06) only. timestep.xls Update For solid elements using MAT_SPOTWELD, LS-DYNA uses a slightly different method of…
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…
LS-DYNA provides three ways to account for the non-structural-mass lumping on structures. 1. Traditional Node Based Mass Lumping using ELEMENT_MASS_{OPTION} This method relies on the preprocessors to compute the node-based additional mass that is to be lumped based on the total non-structural-mass that is to be included. The input (into a preprocessor) would simply be…
*MAT_PIECEWISE_LINEAR_PLASTICITY (*MAT_024) is widely used material model for metals and in some cases plastics. Its popularity is widespread since it offers several plasticity models and can also be strain-rate dependent. One particle parameter, the Yield Stress, in the material card can appear in more than one place and can be sometimes confusing to know which…
Since the first release of d3View, there have been many incremental but bold steps that were taken to tackle the problem of simulation data management especially related to LS-DYNA. I am proud to announce the next generation of simulation data manager that will be available shortly to worldwide users in the form of d3View v2.0…
Initial velocity is always specified to a single node and can carry only one value. Multiple initial velocity definitions for the same node will always use the last encountered value. To illustrate this, if we have nodes N1,N2 and N3 and we define a initial velocity for all nodes to be ‘V1’ followed by N2…
Attached is a simple code that I wrote a while back to convert a force-deflection/engineering-stress_strain/true_stress_strain curve to effective stress vs effective strain curve. The input is a simple LS-DYNA valid keyword file with *define_curve keyword. Its not an elegant code but works in most cases. A sample curve is also included. I am working on…
In an iterative simulation process, the main problem or difficulty is to use the existing results to understand its dependency on certain variables (design or just numerical). This difficulty, often causes us to rerun the simulations in a more controlled environment. Let me illustrate this with a simple problem in which we have some v1-v10…
Here is one of the simplest set up of a tiebreak test problem that was developed earlier. You can test the tiebreak under any load case by simply including the appropriate included file. The main file is named “main.k”. tiebreak_example.tar Thanks to Brian Wainscott, LSTC, who was instrumental in helping to understand some important aspects…
Recently, I came across this MIT Open Course Ware and thought it might be useful for others as well. MIT has made more than 1800 courses available at no cost.
