12. Debonding
12.1. Including Debonding in a Contact Analysis
12.1.4. Postprocessing
All applicable output quantities for contact elements are also available for debonding: normal contact stress (PRES), tangential contact stress (TAUR, TAUS, SFRIC), contact gap (GAP), tangential slip (TASR, TASS, SLIDE), etc. In addition, the following debonding specific output quantities are available as NMISC data: debonding time history (DTSTART), debonding parameter (DPARAM), and critical fracture energy (DENERI, DENERII).
For more information on how to review results in a contact analysis, see Reviewing the Results (p. 65) in Chapter 3, Surface-to-Surface Contact (p. 11).
12.1.4. Postprocessing
Appendix A. Example 2-D Contact Analysis with Fluid Pressure-Penetration Loading
This example represents a planar seal compression with applied fluid pressure-penetration loading at the contact interface. It demonstrates the application of the fluid pressure loads and the propagation of the fluid penetration path from one starting point into the contact interface.
A.1. Problem Description
The model represents a half symmetry planar hyperelastic seal.Figure A.1: Diagram of Planar Seal Model (p. 135) shows a diagram of the model, and Figure A.2: Meshed Planar Seal Model (p. 136) shows the meshed half
symmetry model.
Figure A.1: Diagram of Planar Seal Model
0.865 inches applied displacement
1/2 symmetry
Figure A.2: Meshed Planar Seal Model
The seal is compressed by a displacement-controlled load in the first load step. Fluid pressure is applied to all contact elements in the second load step (see Figure A.3: Fluid Pressure Loading on Planar Seal (p. 136)) so that the fluid opens and penetrates into the contact interface that was previously closed by compression.
The fluid pressure is applied using the SFE command with the load key set to 1 (LKEY = 1 on SFE). Using SFE with the load key set to 2 (LKEY = 2 on SFE), all default starting points are suppressed (STA1 = -1) and two elements are chosen as starting locations initially exposed to the fluid (STA1 = 1). (See Specifying Fluid Penetration Starting Points (p. 58) for more information on the STA values.) From this location the fluid penetrates gradually by opening the bottom part of the contact surface, while the top part of the contact surface completely closes.
Figure A.3: Fluid Pressure Loading on Planar Seal
At the end of the first load step (compression load step) most of the contact is closed as shown in the above figure. Plots of contact fluid pressure at an intermediate substep of load step 2 and at the end of load step 2 are shown in Figure A.4: Intermediate Fluid Pressure Distribution (p. 137) and Figure A.5: Final Fluid Pressure Distribution (p. 137).
Figure A.4: Intermediate Fluid Pressure Distribution
Figure A.5: Final Fluid Pressure Distribution
Three contact elements at the bottom of the seal are used for time history postprocessing, representing each region that undergoes fluid penetration. Time history results for fluid contact pressure and gap are printed and plotted to show the path of fluid penetration along the bottom contact elements. The fluid pressure history is shown in Figure A.6: Time History of Fluid Pressure for Three Contact Elements (p. 138).
A.1. Problem Description
Figure A.6: Time History of Fluid Pressure for Three Contact Elements
A.2. Input File
/title,Seal compression with fluid pressure-penetration loading
/com =====================================================================
/com OBJECTIVE:
/com The objective of this test is to verify the path of fluid /com penetration pressure with rigid-flex contact
/com and CONTA171 default keyoptions.
/com
/com DESCRIPTION:
/com The model represents a planar seal that is compressed. Fluid /com pressure is applied to all contact elements so that the fluid /com penetrates and opens the contact that used to be closed by /com compression.
/com
/com The fluid pressure is applied after the compression, and one /com starting point is chosen to be initially in fluid (STA=1 on SFE).
/com From this location the fluid penetrates gradually at the bottom /com surface.
/com
/com TEST SPECIFICATIONS:
/com SOLID ELEMENTS: PLANE182 - PLANE STRESS /com TARGET ELEMENT: TARGE169
/com CONTACT ELEMENT: CONTA171, K(14)=0, K(2)=0, K(4)=0 /com MATERIAL MODEL: HYPERELASTIC
/com /com
/com RESULTS:
/com At the end of load step 1 there are 3 regions where contact is /com closed at the bottom surface. One element from each of these /com regions is chosen, and the time history results for fluid /com contact pressure and gap are printed and plotted to show the /com path of fluid penetration along the bottom contact elements.
/com Notice that at the time when the contact opens /com (gap is not zero), the FPRS is nonzero.
/com =====================================================================
/prep7
et,1,182 ! PLANE182 with plane stress option
esize,0.02 ! Set element attributes and meshing parameters type,1
mat,1 smrtsize,5
amesh,all ! Mesh the model allsel
lsel,s,,,4 ! BCs to model half symmetry nsll,s,1
d,all,ux,0 allsel
/com **** Contact pair creation ****
et,2,169 et,3,171
keyopt,3,10,2
mp,mu,2,0.2 ! Friction r,2
/com **** Top and bottom rigid targets ****
type,2
nsll,s,1
d,all,uy,-0.865 ! Move top rigid target nlgeom,on
time,1
nsubst,25,2000,5 outres,all,all allsel
nropt,unsym ! Unsymmetric due to friction solve
esel,s,ename,,171 ! Select only contact elements
sfe,all,1,PRES, ,150 ! Apply fluid pressure of 150 to all contact elements sfe,all,2,pres,,-1 ! Suppress default starting points (STA1 = -1)
nsel,s,loc,x ! Select a location for starting points esln
esel,r,ename,,171 ! Reselect only the contact elements
sfe,all,2,pres,,1 ! Specify the above location to be initially in fluid (STA1 = 1]
allsel
nsubst,100,1000,10 solve
finish
/com **** Post1 postprocessing ****
/post1 /show set,2,last finish
/com **** Post26 time history postprocessing ****
/post26 timerange,1,2
esol,2,523,138 ,cont,fprs,CONTFPRS1 esol,3,523,138 ,cont,gap,CONTGAP1
/com *****************************************************************************
/com History of contact gap and fluid pressure for an element in the /com region that opens first
/com *****************************************************************************
prvar,2,3
esol,4,578,53 ,cont,fprs,CONTFPRS2 esol,5,578,53 ,cont,gap,CONTGAP2
/com ****************************************************************************
/com History of contact gap and fluid pressure for an element in the /com region that opens later
/com *****************************************************************************
prvar,4,5
esol,6,517,6,cont,fprs,CONTFPRS3 esol,7,517,6,cont,gap,CONTGAP3
/com ****************************************************************************
/com History of contact gap and fluid pressure for contact element /com that opens last
/com *****************************************************************************
prvar,6,7
/title,Time history of fluid pressure for three contact elements /axlab,y,Fluid pressure
plvar,2,4,6 finish
A.2. Input File
Index
B
beam-to-beam contact, 73
C
contact analysis, 1
asymmetric vs. symmetric contact, 14 beam-to-beam, 2, 73
birth and death option, 55
boundary conditions for node-to-node contact, 95 boundary conditions for surface-to-surface contact, 56
direct generation to create rigid target elements, 16 electric contact, 87
electrostatic elements, 87 emissivity, 85
explicit dynamics, 1 flexible-to-flexible, 1, 11
fluid pressure-penetration loads for surface-to-sur-face contact, 56
generating node-to-node contact elements, 92 generating surface-to-surface contact elements, 23 heat flux, 84, 87
heat generation due to electric current, 88 heat generation due to friction, 86
initial contact conditions, 41
node ordering in node-to-node analysis, 93 node-to-node, 2, 4, 91
node-to-surface, 2, 4, 69 node-to-surface KEYOPTS, 70 node-to-surface real constants, 71 normals, 7, 20, 23, 93
open far-field contact status, 48 open near-field contact status, 48 overall steps, 11
solution options for node-to-node contact, 96 solution options for surface-to-surface contact, 63 solving, 64
spurious contact, 49
Stefan-Boltzmann constant, 85 sticking contact status, 48
summary of contact capabilities, 2 superelements, 53
surface interaction for electric contact, 88 surface interaction models, 50
target surface element types and real constants, 15 target surface modeling and meshing tips, 20 target surface nodal number ordering, 20 target surface pilot node, 15, 55
target surface primitives, 15 temperature required, 84 thermal contact, 83 thickness effect, 54
time step control, 54
using meshing tools to create rigid target elements, 17
D
debonding, 131 delamination
in a contact analysis, 131
F
fluid pressure-penetration loads, 56
I
internal MPC, 99
L
line-to-surface contact, 79
M
magnetic analysis contact, 89
multipoint constraint, 99
P
penalty stiffness
in contact analysis, 23 pilot node
in contact analysis, 15, 55
S
spot welds, 119