In several situations, simulation models (new or inherited), are quite often burderend with several expensive features that may have negligible effect on the response that is purely used for comparative numerical studies. When a large portion of any simulation model turnaround time consists of features that are irrelavant to the focued study, it is imperative [...]
Archive for December, 2006
Speeding up Simulations for Focused Studies
Published by December 22nd, 2006 in LS-DYNA Bytes. 0 CommentsInitial Penetrations in Contact Interfaces
Published by December 20th, 2006 in LS-DYNA Contact. 0 Comments1. Introduction
Contact definitions allow the modeling of interaction between one or more parts in a simulation model and have become a necessity in any small or large deformation problem. The main objective of the contact interfaces is to eliminate any “overlap� or “penetration� between the interacting surfaces and they accomplish this by first detecting the [...]
Prescribing Motion to a Rigidbody with Respect to a Local System
Published by December 19th, 2006 in LS-DYNA Bytes. 0 CommentsLS-DYNA offers several ways to prescribe a motion to a rigidbody using *BOUNDARY_PRESCRIBED_MOTION keyword. To prescribe a motion to a rigidbody along a local coordinate system, LS-DYNA offers two method to accomplish this. To demonstrate the differences in these two methods, we will consider a rigidbody that has initial rotational velocity and a prescribed displacement. [...]
Over the years, spotweld representation for crash and NVH applications have evolved from a crude to a detailed modeling resulting in reduced pre-processing effort while greatly enhancing the accuracy of numerical models. Here is link that gives a brief overview of spotwelding process in LS-DYNA. Please note that the document is over 2 years [...]
Modeling Press-Fit Conditions to Include Initial Stresses
Published by December 6th, 2006 in LS-DYNA Contact. 2 CommentsIn many designs, parts are often press-fitted as part of an assembly which causes an initial stress condition that is important to consider in simulations. To induce initial stresses that occur in such press-fit conditions, one can either linearly/non-linearly scale the overlap (penetration) or the contact stiffness over a certain interval depending on the following [...]
Full-Newton and Quasi-Newton Iterative Schemes
Published by December 5th, 2006 in LS-DYNA Implicit. 2 CommentsWhen running problems using Implicit solution sheme in LS-DYNA, the default iterative non-linear solver used is the BFGS method that employs a ‘Quasi-Newton’ method in which the global stiffness matrix is reformed only every ILIMIT steps and in between these a relatively inexpensive update to the stiffness matrix is performed. This default stiffness matrix update [...]
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