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increment for the substep in order to scale back the load to achieve convergence. Then, if the minimum time increment for a substep is reached and the program still cannot achieve convergence, it attempts to balance the residuals across two or more substeps. (The process is the same as that described in Balancing Residual Forces (p. 118) for rezoning; however, it cannot be controlled via the MAPSOLVE command.)

If a substep is introduced solely to balance residual forces, the following message (or similar) is written to the output file:

Substep information (rebalancing only) is not included in the monitor file (Jobname.mntr). Also, nonlinear adaptivity criteria are not checked at the end of each substep during rebalancing; therefore, the mesh remains unchanged.

5.6. Controlling Mesh Nonlinear Adaptivity

When using mesh nonlinear adaptivity to improve solution accuracy, the energy-based criteria is often the best selection for general simulations. If you are unsure which parts of the model are critical regions for mesh refinement, simply define an energy-based criterion for all solid elements in the model. A default value of 1.0 for the energy criterion should improve most problems.

If you know which regions are critical and require refinement, define the solid elements in those regions as components and create energy-based criteria for them, or use position-based criteria.

When mesh nonlinear adaptivity is applied to problems which would otherwise be unsolvable (for example, local deformations in buckling/bifuraction or rubber seal problems), combinations of criteria are often required. Contact-based criteria should be used only when solid elements touch target elements and more elements/nodes are necessary to simulate details of contact boundaries and filling. Positionbased criteria should be used for refining elements moving in to particular regions (for example, small cavities). Without a fine enough mesh and a sufficient number of degrees of freedom, the simulation might not accurately predict the behavior of material moving into such regions. Energy-based criteria can be used to refine elements at specific intervals by specifying a very low value or 0 as the minimum energy for splitting.

In any case, do not attempt refinement on a very distorted mesh, as the resulting mesh quality may be worse than that of the original mesh. Morphing and/or topology correction can adjust for mesh distortion to only a very limited extent.

5.7. Postprocessing Mesh Nonlinear Adaptivity Results

Mesh nonlinear adaptivity solution results should be processed as they are for rezoning results.

The displacements listed or plotted are not the total displacements from the beginning of the loading, but the displacements from the last splitting or refinement.

When listing solution results (SET,LIST), each substep starts with a new mesh and is marked “REZONE.”

5.8. Mesh Nonlinear Adaptivity Examples

The following example problems are provided to help you understand how to apply mesh nonlinear adaptivity:

5.8.1. Example: Rubber Seal Simulation

5.8.2. Example: Crack Simulation

5.8.1. Example: Rubber Seal Simulation

Following is the example input for the problem discussed in Rubber Seal Simulation (p. 136):

/batch,list

/prep7

/com geometry paratmeters rf = 1

yd = 6 yf = 12 xc = 0 yc = 12

disp = -4.0 w = 3

/com element types and size el = w

et,1,182

keyopt,1,3,2

!keyopt,1,6,1

et,2,169

et,3,171

keyopt,3,9,0

keyopt,3,10,1

!keyopt,3,2,3

/com materials c10=62.3584129 c01=-37.8485452 dd=1.E-03

tb,hyper,1,,2,mooney

tbdata,1,c10,c01,dd

mp,mu,2,0.0

r,2

/com create the model k,1,xc,yc k,2,xc+3*w,yc k,3,w,0.0

k,4,w,yd

k,5,3*w,yd

rect,0,w,0,yd

rect,0,w,yd,yf

/pnum,line,1

l,1,2

l,3,4

l,4,5

lfillt,10,11,rf

/com create mesh esize,el

mat,1

type,1

real,1

amesh,1,2

/pnum,elem,1

/pnum,node,1

nummrg,node

numcmp,node

/replot

/com the 1st contact paires mat,2

vk.com/club152685050Mesh Nonlinear Adaptivity | vk.com/id446425943

real,2

type,2

esize,yf

lmesh,9

allsel,all

type,3

lsel,,,,6,7

nsll,,1

esln,,0 esurf alls

/com the 2nd contact paires real,3

type,2

lplot esize,yf lmesh,9,12

lsel,s,line, ,10,12 esll,s,1

esurf, ,reverse allsel,all

lplot type,3 lsel,,,,6 lsel,a,,,2 nsll,,1 esln,,0 esurf alls

/com boundary condition

/com rigid punch lsel,,,,9 nsll,,1 d,all,uy,disp d,all,ux,0.0 alls

/com rigid die face lsel,,,,10,12 nsll,,1 d,all,uy,0.0 d,all,ux,0.0

alls

/com left side nsel,,loc,x,0 d,all,ux,0.0 alls

/com bottom nsel,,loc,y,0 d,all,uy,0.0 alls

/com check the contact definition cncheck

elist fini

/solution

/com define nonlinear adaptive criterion esel,,ename,,182

cm,solid,elem allsel

nlad,solid,add,box,xyzr,-0.0,9,5,12 nlad,solid,on,,,-2

pred,off

rescontrol,,all,1,20

eresx,no

nlgeom,on

time,1

NSUBST,50,500,5

outres,all,all solv

fini

5.8.2. Example: Crack Simulation

Following is the example input for the problem discussed in Crack Simulation (p. 139):

vk.com/club152685050Mesh Nonlinear Adaptivity | vk.com/id446425943

nsel,s,loc,y,-0.5 nsel,r,loc,x,10 f,all,fy,-5500 allsel,all