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. ...