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…
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…
I am glad to announce that the latest version of LS-DYNA will support the use of *DEFINE_CONTACT_VOLUME in any *SET_{OPTION}_GENERAL keyword. As most of you know, *DEFINE_CONTACT_VOLUME offers many advantages over *DEFINE_BOX such as definition in a local system and multiple shapes such as sphere, ellipse, box, and cylinder. With this support, my earlier post…
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.
Recently, I was teaching a class for Black & Decker, and one of the students, Kevin, was taking notes that I thought captured my lecture quite well. I asked him to provide a scanned copy which is included here for others who may find it helpful. notes.ppt
Sven Holcombe of JARI sent us this great presentation summary that covers some of the paper presentation at the 2007 Japan LS-DYNA Conference. Its has been a lot of work for Sven I am sure and its greatly appreciated for his effort. Thanks a lot, Sven. (I removed the preview since the loading time of…
In 2D shell elements, the stress in the normal (fiber) direction is iteratively reduced to zero to meet the plane-stress condition. The strains are however nonzero in the fiber direction and will be linear though the thickness. Under membrane straining, LS-DYNA allows an option to account for the reduction in the shell thickness in the…
In mesh independent deformable spotwelds (see here ), the actual spotwelds are represented using either beams or solids (single or cluster). The nodes of the beam or solid element representing the spotweld are then tied to the sheet metal using a tied interface (TIED_SHELL_EDGE_TO_SURFACE or TIED_NODES_TO_SURFACE). The forces experienced by the beam are the result…
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…
