Double-sided Contact

Chapter 17: Double-sided Contact

17

Double-sided Contact



Summary



Introduction



Requested Solutions



FEM Solutions



Results



Modeling Tips



Pre- and Postprocess with SimXpert



Input File(s)

257 258 258

258

262 262

304

266

CHAPTER 17 257 Double-sided Contact

Summary Title

Chapter 17: Double Sided Contact

Contact features

Deformable-deformable contact with bilinear friction, large strain plasticity, and work hardening

Geometry

2-D Plane Strain assumptions

Five at 1.0” each 1.5” 0.5” 0.5” 0.5” 1.5”

Material properties

Elastic-plastic material with isotropic strain hardening. The stress-strain curve is defined in the materials section. The material properties are: 6

E = 31.75 10 psi  = 0.268 psi  y = 80730 psi

Analysis type

Quasi-static analysis using: elastic plastic material, geometric nonlinearity, and nonlinear boundary conditions

Boundary conditions

Nodes on left-hand side are constrained in x-direction and nodes on bottom side are constrained in y-direction

Applied loads

Nodes on the top side are given the imposed displacement of -0.6 inch in y-direction

Element type

4-node nonlinear plane strain element

FE results

Deformed shapes at several steps, contours of von Mises stress, and total equivalent plastic strain

Stress Contours Last Increment

258 MD Demonstration Problems CHAPTER 17

Introduction This problem demonstrates MD Nastran’s ability to perform multibody contact analysis, incorporating automated double-sided contact with friction between the contact surfaces for linear plane strain elements. For these types of contact problems, it is not necessary to assign either body as a master or slave.

Requested Solutions The large displacement elastic-plastic contact analysis is carried out using MD Nastran for a deformable-todeformable contact problem with friction. The application of the nonlinear plane strain element is demonstrated by using the nonlinear extension PSHLN2 option along with the PLPLANE option. The following results from the MD Nastran model are compared with the results obtained from the Marc model. • Deformed shapes at steps 10, 20 and 30 • Contour plot for equivalent plastic strain

FEM Solutions A numerical solution has been obtained with MD Nastran’s SOL 400 for a 2-D representation of the contact simulation between two deformable bodies. The details of finite element model, contact simulation, material, load, boundary conditions, and solution procedure are discussed below.

Finite Element and Contact Model The finite element mesh for each of the two deformable bodies contains 60 elements and 79 nodes. MD Nastran’s 2-D plane strain solid elements with material ID 1 are selected using the following PLPLANE and PSHLN2 entries. The second line of the PSHLN2 option enables SOL 400 to access the 4-node plane strain elements using the regular CQUAD4 elements. This element can be used for both linear and nonlinear applications. When used for linear applications, the assumed strain formulation should be activated for this element using the NLMOPTS,ASSM,ASSUMED bulk data entry to get good bending behavior. This assumed strain option should not be used for the applications involving large strain plasticity as in the case of the present problem. The finite element model used for this simulation is shown in Figure 17-1. PLPLANE 1 PSHLN2 1 C4

1 1 PLSTRN

1 L

CHAPTER 17 259 Double-sided Contact

Figure 17-1

Finite Element Model used with MD Nastran Simulation

In defining the contact model, the elements comprising the deformable bodies are used to generate a deformable contact bodies with ID 1 and 2 using the following BCBODY and BSURF entries. The friction factor of 0.07 is defined for both these contact bodies. BCBODY BSURF ... BCBODY BSURF ...

1 1

2D 61

DEFORM 62

1 63

0 64

.07 65

66

67

2 2

2D 1

DEFORM 2

2 3

0 4

.07 5

6

7

Furthermore, the following BCTABLE entries identify how these bodies can touch each other. BCTABLE with ID 0 is used to define the touching conditions at the start of the analysis. This is a mandatory option required in SOL 400 for contact analysis and is flagged in the case control section through the optional BCONTACT = 0 option. The BCTABLE with ID 1 is used to define the touching conditions for later increments in the analysis and is flagged using BCONTACT = 1 in the case control section. The 0 defined for the first field (ISEARCH) of third data line of BCTABLE indicates that double-sided contact will be used for this contact pair. With this double contact option, SOL 400 will consider another contact pair for the analysis with body 1 as master and body 2 as slave in addition to the contact pair defined in the BCTABLE option. BCTABLE

BCTABLE

0 SLAVE

1 0 FBSH MASTERS 2 1 SLAVE 1 0 FBSH MASTERS 2

0. 0 1.+20

1 0. 0 0.9

0. 0 1.+20

1 0. 0 0.9

.07

0.

0

0.

.07

0.

0

0.

260 MD Demonstration Problems CHAPTER 17

The BCPARA bulk data entry shown defines the general contact parameters to be used in the analysis. BCPARA

0 FTYPE

6

BIAS

0.9

The ID 0 on the BCPARA option indicates that the parameters specified herein are applied right at the start of the analysis and are maintained through the analysis unless some of these parameters are redefined through the BCTABLE option. Important entries under BCPARA option include FTYPE – the friction type and the BIAS - the distance tolerance bias. As a general recommendation, BIAS is set to 0.9 (note that the default value of BIAS is 0.9). For the frictional case, FTYPE is set to 6 (bilinear Coulomb model).

Material The isotropic elastic and elastic-plastic material properties of the deformable bodies are defined using the following MAT1 and MATEP options. The stress-strain curve for this material is defined in TABLES1 which is referred in MATEP option. Figure 17-2 shows the stress-strain diagram defined in TABLES1. MAT1 1 3.175+7 .268 MATEP 1 TABLE 1 TABLES1 1 2 * 0.000000000e+0 8.073000000e+4 ... * *

7.000000000e-2 ENDT

200000

1.595880000e+5

7.4-4

5.13-6

1.000000000e-5

8.096400000e+4

2.200000000e-1

1.753830000e+5

Stress (Psi)

150000

100000

Plastic Strain (1) 50000 0.00 Figure 17-2

0.05

0.10

0.15

0.20

0.25

Stress-Plastic Strain Curve of the Material

The following NLMOPTS entry enables large strain formulation using additive plasticity with mean normal return. NLMOPTS,LRGS,1

CHAPTER 17 261 Double-sided Contact

Loading and Boundary Conditions The loads and boundary conditions are applied using the following SPCD and SPC1 options. SPCD options are used to impose the displacement of -0.6 inch for the nodes on the top side. The nodes on the left-hand side are constrained in x-direction and nodes on the bottom side are constrained in y-direction. These constraints are defined using the SPC1 options. Figure 17-3 shows the loads and boundary condition applied on the model. SPCADD 2 3 4 5 $ Enforced Displacements for Load Set : yu0 SPCD 1 104 2 -.6 105 2 -.6 SPCD 1 106 2 -.6 107 2 -.6 SPCD 1 108 2 -.6 109 2 -.6 SPCD 1 130 2 -.6 131 2 -.6 SPCD 1 132 2 -.6 133 2 -.6 SPCD 1 134 2 -.6 $ Displacement Constraints of Load Set : x0 SPC1 5 1 35 40 45 50 55 61 67 73 79 80 86 92 98 104 $ Displacement Constraints of Load Set : y0 SPC1 3 2 25 26 27 28 29 30 51 52 53 54 55 $ Displacement Constraints of Load Set : yu0 (just to trigger s-set) SPC1 4 2 104 105 106 107 108 109 130 131 132 133 134

Figure 17-3

Load and Boundary Conditions Shown on FE Mesh

Solution Procedure The nonlinear procedure used is defined through the following NLPARM entry: NLPARM

1

30 0.01

PFNT

25

P

YES

262 MD Demonstration Problems CHAPTER 17

where 30 indicates the total number of increments; PFNT represents Pure Full Newton-Raphson Technique wherein the stiffness is reformed at every iteration; KSTEP = 0 in conjunction with PFNT indicates that the program automatically determines if the stiffness needs to be reformed after the previous load increment is completed and the next load increment is commenced. 25 is the maximum number of allowed recycles for every increment. P indicates that convergence will be checked on residuals (P). YES indicates that intermediate output will be produced after every increment. The 0.01 defined in the second line of NLPARM indicates the convergence tolerances of 0.01 for residual checking.

Results The deformed shape at steps 10, 20, and 30 observed from both Marc and SOL 400 models are compared in Figure 17-4. The equivalent plastic strain contours observed at step 30 from Marc and SOL 400 runs are presented in Figure 17-5 and Figure 17-6. It is clearly observed from these pictures that, the predictions from SOL 400 matches closely with the predictions from Marc.

Modeling Tips • PSHLN2 entry in conjunction with regular PLPLANE entry allows the users to make use of the plane strain elements using regular Nastran elements CQUAD4, CQUAD8, and CTRIA6. Users should make use of the NLMOPTS,LRGS,1 option to flag the large strain behavior of these elements. • The value of 0 for ISEARCH parameter in BCTABLE defines the double sided contact for this problem. Assigning the value of 1 for ISEARCH parameter will define single sided contact for this problem, and this will not work properly in this case. The nug_17w.dat input file shows this wrong way of contact definition for this problem and Figure 17-7 shows how SOL 400 works in such situations.

CHAPTER 17 263 Double-sided Contact

Marc - Step 10

Marc - Step 20

Marc - Step 30

Figure 17-4

SOL 400 - Step 10

SOL 400 - Step 20

SOL 400 - Step 30

Deformed Shape Plots at Steps 10, 20, and 30

264 MD Demonstration Problems CHAPTER 17

Figure 17-5

Plastic Strain Contour from Marc

Figure 17-6

Plastic Strain Contour from MD-Nastran SOL 400

CHAPTER 17 265 Double-sided Contact

Figure 17-7

Penetration with Wrong Contact Definition

266 MD Demonstration Problems CHAPTER 17

Pre- and Postprocess with SimXpert

Units a. Tools: Options b. Observe the User Options window c. Select Units Manager d. For Basic Units, specify the model units: e. Length = m, Mass = kg, Time = s, Temperature = Kelvin, and Force = N

a

b d c

e

CHAPTER 17 267 Double-sided Contact

Create a Part for the body_lower a. Assemble tab b. Select Create Part c. For Title, enter body_lower d. Click OK: e. Observe body_lower in the Model Browser Tree

a b

c e

d

268 MD Demonstration Problems CHAPTER 17

Create Mesh for the body_lower a. Meshing tab: 3-4 Point Mesh b. Points: X,Y, Z Input: 0,-1.5,0;2,-1.5,0;2,0,0;0,0,0, click OK X,Y, Z Input: 2,-1.5,0;5,-1.5,0;5,0,0;2,0,0, click OK X,Y, Z Input: 0,0,0;2,0.0,0;1,1.5,0;0,1,0, click OK c. For n1, enter 5 d. For n2, enter 4 e. For n3, enter 5 f. For n4, enter 4 g. Click OK

a

b c

b

b

d e f g

b

CHAPTER 17 269 Double-sided Contact

Merge Equivalent Nodes in the body_lower a. Nodes/Elements tab: Equivalence b. Entities: Select All c. Click OK d. Click OK

a a

b

c

d

270 MD Demonstration Problems CHAPTER 17

Create a Part for the body_upper a. Assemble tab b. Select Create Part c. For Title, enter body_upper d. Click OK: e. Observe body_lower in the Model Browser Tree

a b

c

e

d

CHAPTER 17 271 Double-sided Contact

Copy Mesh from body_lower to body_upper a. Tools: Transform b. Select Create Part c. Select Reorient

a

b

c

272 MD Demonstration Problems CHAPTER 17

Copy Mesh from body_lower to body_upper (continued) a. Pick: check Make Copy b. Select Elements c. Click All d. Select Create Source LCS e. Select XYZ f. For X,Y,Z Coordinate: enter 0 0 0 1 0 0 0 1 0; click OK g. Select Create Target LCS h. Select XYZ i. For X,Y,Z Coordinate: enter 5 1.5 0 4 1.5 0 5 0.5 0; click OK j. Click Done k. Click Exit

d e

a

f

b

c

g

h

i

j

k

CHAPTER 17 273 Double-sided Contact

Create Stress-strain Curve from Excel File a. Copy stress-strain data from Excel file mat_nug17.xls

a

274 MD Demonstration Problems CHAPTER 17

Create Stress-strain Curve from Excel File (continued) a. Materials and Properties tab: Isotropic b. Click Plastic Strain c. Right click Row 1 Column 1 d. Select Paste Table e. Click OK

a b c

d e

CHAPTER 17 275 Double-sided Contact

Create Material Properties a. Fields/Tables tab: NastranBDF TABLES1 b. For Name enter Iso_1 c. For Young’s Modulus enter 3.175e7 d. For Poisson’s Ratio enter 0.268 e. For Density enter 0.00074 f. Click Advanced

a

b c d e f

276 MD Demonstration Problems CHAPTER 17

Create Material Properties (continued) a. Right click Add Constitutive Model b. Select Elasto Plastic c. Click Stress-Strain Data d. For Stress-Strain Data, select TABLE_1 e. Click OK

a b

c

d e

CHAPTER 17 277 Double-sided Contact

Define Property Data for lower_body a. Materials and Properties tab: Plane b. For Name enter prop_body_lower c. For Entities, select body_lower from Model Browser tree d. Click Advanced e. For Corner Element Keyword, select C4 f. Click OK

a

b c

e

d

f

g

278 MD Demonstration Problems CHAPTER 17

Define Property Data for upper_body a. Materials and Properties tab: Plane b. For Name enter prop_body_upper c. For Entities, select body_upper from Model Browser tree d. Click Advanced e. For Corner Element Keyword, select C4 f. Click OK

a

b c

e d

f

g

CHAPTER 17 279 Double-sided Contact

Define Contact Body for lower_body a. LBCs tab: Deformable Body b. For Name enter def_body_lower c. For Type, select Deformable Surface d. For Entities, select body_lower from Model Browser tree e. For Friction Coefficient, enter 0.07 f. Click OK g. Observe def_body_lower in the Model Browser Tree

a

b c d e b f

g

280 MD Demonstration Problems CHAPTER 17

Define Contact Body for upper_body a. LBCs tab: Deformable Body b. For Name enter def_body_upper c. For Type, select Deformable Surface d. For Entities, select body_upper from Model Browser tree e. For Friction Coefficient, enter 0.07 f. Click OK g. Observe def_body_upper in the Model Browser Tree

a

b c d e b f

g

CHAPTER 17 281 Double-sided Contact

Define Contact Table a. LBCs tab: Table b. Select Deactivate All c. Set Touching Condition for body 1 to 2 d. For Distance Tolerance, enter 0 e. For Friction Coefficient, enter 0.07 f. For Individual Contact Detection, select Double Sided g. For Bias Factor, enter 0.9 h. Click OK

a

b c

d e f g

h

282 MD Demonstration Problems CHAPTER 17

Define Boundary Conditions a. LBCs tab: LBC b. Select Pin c. For Name, enter fix-x d. For Entities, select nodes at left edges of the model e. Draw box about nodes at left edges of the model f. For Translation, select Tx g. Click OK

a b

c d f g

e

CHAPTER 17 283 Double-sided Contact

Define Boundary Conditions (continued) a. LBCs tab: LBC b. Select Pin c. For Name, enter fix-y d. For Entities, select nodes at left edges of the model e. Draw box about nodes at left edges of the model f. For Translation, select Ty g. Click OK

a b

c d f g

e

284 MD Demonstration Problems CHAPTER 17

Define Boundary Conditions a. LBCs tab: LBC b. Select General c. For Name, enter disp-y d. For Entities, select nodes at top edge of the model e. Draw box about nodes at top edge of the model f. For Translation, select Ty g. For Ty, enter -0.6 h. Click OK

a b

c e d f

g

h

CHAPTER 17 285 Double-sided Contact

Create SimXpert Analysis File a. Right click FileSet b. Select Create new Nastran job c. For Job Name, enter nug-17 d. For Solution Type, select SOL 400 e. For Solver Input File, specify the fine name and its path f. Unselect Create Default Layout g. Click OK

a b c

d e f

g

286 MD Demonstration Problems CHAPTER 17

Create SimXpert Analysis File (continued) a. Right click on Load Cases b. Select Create Global Loadcase c. Click OK

a

b

c

CHAPTER 17 287 Double-sided Contact

Create SimXpert Analysis File (continued) Select Contact Table for Loads in Global Loadcase a. Right click on Loads/Boundaries b. Select Select Contact Table c. For Selected BCTable, select BCTABLE_1 d. Click OK

a

b

c

d

288 MD Demonstration Problems CHAPTER 17

Create SimXpert Analysis File (continued) a. Right click on Loadcase Control b. Select Subcase Nonlinear Static Parameters c. For Stiffness Update Method: select Pure Full Newton (PFNT) d. Unselect Use Default Tolerance Setting e.Click Load Error and for Load Tolerance, enter 0.01 f. For Intermediate Output Control, select Every computed load increment (YES) g. Click Apply h. Click Close

a b c

d

e

f g h

CHAPTER 17 289 Double-sided Contact

Create SimXpert Analysis File (continued) a. Double click on Loadcase Control b. Select Stepping Procedure Parameters c. For Number of Steps: enter 30 d. Click Apply e.Click Close

a

b

c

d e

290 MD Demonstration Problems CHAPTER 17

Create SimXpert Analysis File (continued) a. Right click on Loads/Boundaries b. Select Select Lbcs c. For Selected Lbcs: using the Control Key and the Mouse, select fix-x, fix-y, disp-y from the Model Browser tree d. Click OK

a b c

c

d

CHAPTER 17 291 Double-sided Contact

Create SimXpert Analysis File (continued) a. Right click on Loads/Boundaries b. Select Select Contact Tables c. For Selected BC Table: select BCTABLE_1 from the Model Browser tree d. Click OK

c

a

c

b d

292 MD Demonstration Problems CHAPTER 17

Create SimXpert Analysis File (continued) a. Right click on Output Request b. Select Nodal Output Requests c. Select Create Displacement Output Request d. Check Suppress Print e. Click OK

a b

c

d

e

CHAPTER 17 293 Double-sided Contact

Create SimXpert Analysis File (continued) a. Right click on Output Request b. Select Elemental Output Requests c. Select Create Nonlinear Stress Output Request d. Check Suppress Print e. Click OK

a b

c

d

e

294 MD Demonstration Problems CHAPTER 17

Create SimXpert Analysis File (continued) a. Double click on Solver Control b. Select Solution 400 Nonlinear Parameters c. For Large Displacement: select Large Disp. and Follower Force d. Click Apply e. For Large Strain Formulation: select Hypoelasticy and Additive Plasticity for Large Strain Formulation f. Click Apply g. Click Close (not shown)

a b c

d

e

f

CHAPTER 17 295 Double-sided Contact

Create SimXpert Analysis File (continued) a. Double click on Solver Control b. Select Contact Detection Parameters c. For Bias on Distance Tolerance, enter 0.9 d. Click Apply e. Select Contact Friction Parameters f. For Type: select Bilinear Coulomb g. Click Apply h. Click Close (not shown)

a c b

d

e f g

296 MD Demonstration Problems CHAPTER 17

Create SimXpert Analysis File (continued) a. Double click on Solver Control b. Select Output File Properties c. For Nastran DB Options: select Master/DBALL d. For Binary Output: select OP2 e. Click Apply f. Click Close (not shown)

a

c

b

d

e

CHAPTER 17 297 Double-sided Contact

Create SimXpert Analysis File (continued) a. File: Save b. Right click on nug-17 c. Select Run d. After completion of job, select Save e. File: New

e a

d

b

c

298 MD Demonstration Problems CHAPTER 17

Attach the SimXpert Analysis Results File a. Results tab: Deformations b. For Deformed display scaling., select True c. Plot Data: Plot type, select Deformation d. For Results cases, select the last increment e. For Results Type, select Displacements, Translational f. Click Update

a

b

f c

e

d

CHAPTER 17 299 Double-sided Contact

Attach the SimXpert Analysis Results File (continued) a. Click Animate b. Results cases: select SC1:Step 1 (selects all increments) c. Results entities: Results type: select Displacements, Translational d. Click Update

d c a

b

300 MD Demonstration Problems CHAPTER 17

Attach the SimXpert Analysis Results File (continued) a. Animation tab b. Click Pause icon to stop animation

a b

CHAPTER 17 301 Double-sided Contact

Attach the SimXpert Analysis Results File (continued) a. Results: Fringe b. Click Animate c. Results entities: Results cases: select SC1:Step 1 (selects all increments) d. Results entities: Results type: select Contact Status e. Fringe tab: Display settings tab: Element edge display, Display, select Element edges f. Label attributes, select color of labels g. Click Update

a

b

d c

f e

g

302 MD Demonstration Problems CHAPTER 17

Attach the SimXpert Analysis Results File (continued)

CHAPTER 17 303 Double-sided Contact

Attach the SimXpert Analysis Results File (continued) a. Results: Fringe b. Click Pause icon to stop animation c. Plot Data tab: Results type: select Logarithmic Strains d. Derivation: select von Mises e. Click Update

a

b

e c

d

304 MD Demonstration Problems CHAPTER 17

Attach the SimXpert Analysis Results File (continued)

Input File(s) File

Description

nug_17.dat

MD Nastran SOL 400 input

nug_17w.dat

Same as nug_17.dat, but the contact is defined in a wrong way in BCTABLE

ch17.dat

MD Nastran SOL 400 input for SimXpert

ch17.SimXpert

Corresponding SimXpert input file