Deformable spotwelds modeled using beams or solids elements can invariably limit the global timestep due to its small dimensions. LS-DYNA provides two methods to scale the spotweld timestep. The first method is the well-known global mass-scaling using DT2MS in CONTROL_TIMSESTEP. When DT2MS is non-zero (usually a negative number), the density of the spotwelds are modified [...]
Archive for the 'LS-DYNA Materials' Category
Mass scaling for MAT_SPOTWELD elements
Published by April 5th, 2010 in LS-DYNA Connections and LS-DYNA Materials. 0 CommentsLS-DYNA now offers a modified version of *MAT_CRUSHABLE_FOAM in the form of *MAT_MODIFIED_CRUSHABLE_FOAM . In the new material model, the strain rate effects can be included in the foam a *DEFINE_TABLE . To reduce or eliminate the noise in the evaulation of the new yield stress as a function of strain and strain-rate, LS-DYNA offers [...]
Determining Prony Series Constants for Modeling Creep and Relaxation
Published by October 3rd, 2007 in LS-DYNA Bytes and LS-DYNA Materials. 0 CommentsCame across this excellent tutorial that talks in detail the steps involved in determining the Prony series constants. Determining a Prony Series for a Viscoelastic Material From Time Varying Strain Data
There are three different ways to model unloading behavior when using material model MAT_083. They are graphically depicted below (these figures may appear in the next release of the LS-DYNA keyword and theory manual). Option 1 – Default (Click image to enlarge) In the default option (1), HU=0, and the table is positive which then [...]
Stress Relaxation in Viscoelastic Material Models
Published by April 16th, 2007 in LS-DYNA Bytes and LS-DYNA Materials. 1 CommentLS-DYNA allows several ways to model of stress relaxation often seen in viscoelastic materials when subjected to a sudden constant strain. The methods to model the stress relaxation is briefly discussed here. 1. Curve Input When using MAT_GENERAL_VISCOELASTIC material model, one can directly input the time log dependence of the relaxation modulus using LCID parameter. [...]
Modeling Off-Axis Dependent Yield Stress for Honeycombs using MAT_126
Published by March 8th, 2007 in LS-DYNA Bytes and LS-DYNA Materials. 0 CommentsHoneycomb cell structures are popular among weight conscious designers due to their high strength to weight ratio. In the automotive space, aluminum based honeycomb structures are widely used to represent barriers to simulate a controlled energy absorption. Honeycomb structures are highly anisotropic and requires adequate testing to characterize them. This post focusses on the characterization [...]
Recent Comments