Welcome to LS-DYNA Universe

How I become an expert in LS-DYNA? A question that I get a lot. First of all, I am not an expert. I am just passionate about it. Where there is passion, there is a way!


I have covered many topics in my YouTube tutorials, in an attempt to share the good knowledge. However, due to time constraints, I cannot make good quality videos consistently. Thus, I am starting this blog to post weekly notes on LS-DYNA. 

But fear not, I am not planning to stop my YouTube channel. It is advisable that you go there to get the basics, then read the notes here for more advanced simulations.

That's all, see you next week!

BIG FAT DISCLAIMER: All the notes are not by me. It is from my collection of notes throughout my years of learning the software. 

Comments

Post a Comment

Popular posts from this blog

Delamination and Tiebreak Contact

Although the jury is still out, I think people are finding tiebreak contact to be less problematic than cohesive elements. Section 3.5.1, "Composite Delamination", of the Modeling Guidelines Document (MGD), available under "Resources" at http://awg.lstc.com, offers some pertinent tips. See also the example "Ballistic Impact on Composite Plate" at http://awg.lstc.com/tiki/tiki-index.php?page=QA+test+example+7. First of all, for modeling delamination, you'd need to model each ply with a layer of elements. *contact_automatic_one_way_surface_to_surface_tiebreak with OPTION 6,7, or 9 (solids) One approach would be to model a layer of shell or solid elements for each composite layer and bond the layers with a tiebreak contact, e.g., or OPTION 8,10, or 11 (shells). input variables in *mat_138 as follows: Refer to *mat_138 for a detailed description of t...
Read more

Energy Balance

Total energy reported in GLSTAT (see *database_glstat) is the sum of the following:   - internal energy (includes "eroded internal energy") - kinetic energy (includes "eroded kinetic energy") - sliding interface energy (better known as contact energy) - hourglass energy (starting at rev. 83861, includes "eroded hourglass energy") - system damping energy - stonewall energy (better known as rigidwall energy)   "Spring and damper energy" reported in the glstat file is the sum of internal energy  of discrete elements, seatbelt elements, and energy associated with joint stiffnesses  (*constrained_joint_stiffness....).   "Internal Energy" includes "Spring and  damper energy"   as well as internal energy of all other element types.  Thus "Spring and damper energy" is a subset of "Internal energy".   Two energy terms are written to jntforc in 971 R3.    The first term "energy" is new...
Read more

Hourglass

Guidelines provided herein for hourglass control are not to be considered as hard and fast rules, but instead may be considered as a starting point.  The user is responsible for observing the deformed shapes of the elements (to see if hourglassing modes are evident) and for checking hourglass energy in a manner described herein and in https://lsdynauniverse.blogspot.com/2021/03/energy-balance.html Trial and error may be necessary to determine the most effective hourglass control for a particular problem. Starting with 971 R3.1, the default hourglass control for underintegrated elements is: - Shells: viscous type (1=2=3) for explicit, stiffness type (4=5) for implicit - Solids: type 2 for explicit, type 6 for implicit (only 6 is implemented for implicit) See the User's Manual (*HOURGLASS) and   sections 3.2 and 7.4 of the 2006 LS-DYNA Theory Manual. Hourglass (HG) modes are nonphysical, zero-energy modes of deformation that  produce zero strain and no stress.   ...
Read more