Animated MD User's Guide Ch. 49 - Shell Edge Contact

hChapter 49: Shell Edge Contact

49

Shell Edge Contact

Summary Introduction

992 993 993 999

Modeling Details Solution Procedure Results 1000

Modeling Tips Input Files

1003

1003 1004

SimXpert Example

992 MD Users Guide - Application ExamplesCHAPTER 49

SummaryTitle Features GeometryUnits: m, N, sy' z' y' z' y 45o z 10.0 m shell edge contact x' x x' shell edge contact z' y' 10.0 m 5 x 2 x 0.05 x'

Chapter 49: Shell Edge Contact Case 1: In-plane glued edge deformable-deformable contact Case 2: General shell edge deformable-deformable contactUnits: in, lbf, s

Case 1: Modal Analysis of a Thick Rombic Plate

Case 2: Diagonal Crushing of Square Tube

Material properties

Case 1: E = 200GPa , = 0.3 , = 8000 kg m3 Case 2: E = 2.1x10 11 psi , = 0.3

Analysis characteristics Boundary conditions

Case 1: Modal analysis using in plane glued edge contact Case 2: Quasi-static analysis using general shell edge contact Case 1: Upper and lower half of plate are connected using glued edge contact Fixed conditions at all four edges In-plane displacements restrained at all nodes except those nodes at the edges of the glued contact line Case 2: Edge-to-edge contact between two square tubes Clamped condition at bottom edge of lower tube Case 2 Move top edge of top tube down two inches. 4-node shell elements Displacement Contours

Applied loads Element type FE results

Case 1: Mode 1 134.18 Hz

Seam

CHAPTER 49 993 Shell Edge Contact

IntroductionThe 3-D contact capability introduced in MD Nastran R2 supported a general node to surface contact in all translational degrees of freedom. The new feature of shell edge to shell edge contact was added in the R3 release of MD Nastran. The following two cases are considered to demonstrate two different types of shell edge contact.

Case 1:

Modal analysis of thick rhombic plate. This is a NAFEMS test case involving evaluation of natural frequencies of a fully clamped rhombic plate. The plate is divided into two equal parts in the vertical direction. These two parts are meshed with different mesh densities and then connected with in-plane glued edge contact. Diagonal crushing of two square tubes. This model demonstrate the capability of general shell edge contact by crushing the lower square tube with the upper square tube as a result of the edge contact between the two tubes.

Case 2:

Modeling DetailsMD Nastran's solution sequences 103 and 400 are used to demonstrate the new shell edge contact capability with the two test cases. The details of the finite element model, contact simulation, material, load, boundary conditions and solution procedure for these two models are discussed below. Case 1: Two equal parts of rhombic plate are meshed with different mesh densities of 16 x 32 and 20 x 40 CQUAD4 elements. These two parts do not share any node at their common edge as they are connected using in-plane glued edge contact. The FE model used for the modal analysis (SOL 103) shown in Figure 49-1 and the case control section part of the input is given below: SUBCASE 1 METHOD = 1 BCONTACT = 1 SET 10 = 1,2,3,4,5,6 SET 20 = 137,182,213,280,327,593,600,639,703,744 SPC = 2 OMODE = 10 DISP(PLOT,PUNCH)=20 The modal analysis method to be used for extracting the eigenvalues is referenced by the METHOD option, and the associated contact table to be used is referenced by the BCONTACT option. The SPC option refers to the set of boundary conditions to be applied and the OMODE option identifies the list of modes to be extracted.


Case 1 bsurf-1 bsurf-2 bsurf-1 bsurf-2

Case 2

Y Z X Y Z X

Figure 49-1

FE Models used for Cases 1 and 2 of Shell Edge Contact

Case 2: The rectangular sides of each square tube are meshed using 5x10 CQUAD4 elements. The FE details for the SOL 400 analysis of Case 2 are given in Figure 49-1. The case control section part of the input for this model is given below: SUBCASE 1 STEP 1 ANALYSIS = NLSTATIC NLPARM = 1 BCONTACT = 1 SPC = 2 LOAD = 1 DISPLACEMENT(SORT1,REAL)=ALL SPCFORCES(SORT1,REAL)=ALL STRESS(SORT1,REAL,VONMISES,BILIN)=ALL BOUTPUT(SORT1,REAL)=ALL This section defines convergence controls via NLPARM, contact table and parameters via BCONTACT, applied displacements and loads via SPC and LOAD and the displacements, stress, and contact results for the output file.

Material ModelingThe isotropic, Hookean elastic material properties of the deformable body for Case 1 are defined in the SI (international) system using the following MAT1 option:MAT1 1 2.+11 .3 8000.

The MAT1 card for Case 2 is given in the samr system below:MAT1 1 2.1+11 .3 1.


Element ModelingBesides the standard options to define the element connectivity and grid coordinate location, the bulk data section contains various options with special relevance to nonlinear analysis. For the SOL 400 analysis of Case 2, the nonlinear extensions to the lower order shell element, CQUAD4, are activated by using the PSHLN1 property option in conjunction with the regular PSHELL property option in the manner shown below: PSHELL PSHLN1 1 1 C4 1 1 DCT .05 L 1 1

For the modal analysis of Case 1, regular CQUAD4 elements are defined using the following PSHELL option. PSHELL 1 1 1. 1 1

Modeling ContactThe BCPARA option used for the Case 2 model is given below. It defines the number of bodies in contact, together with the maximum number of contact entities (e.g. patches), nodes on the periphery of the contact surfaces and bias factor. The general shell edge contact option is enabled by activating the beam to beam contact flag BEAMB. BCPARA 0 BIAS NBODIES 2 .95 BEAMB MAXENT 1 400 MAXNOD 220

The definition of the contact bodies consists of the Bulk Data Entry BCBODY which defines the deformable body including the body ID, dimensionality, type of body, type of contact constraints and friction, etc. while the BSURF identifies the elements forming a part of the deformable body. The following BCBODY entries are used for cases 1 and 2. Figure 49-1 identifies the contact bodies used in both these models. BCBODY BSURF 1 1 8 16 3D 1 9 17 DEFORM 2 10 18 1 3 11 19 0 4 12 20 5 13 21 6 14 22 7 15 23

To identify the interaction between the contact bodies, the Bulk Data Option BCTABLE is used. BCTABLE with ID 0 is used to define the touching conditions at the start of the analysis. This is a mandatory card required in sol400 for contact analysis and it 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 it is flagged using BCONTACT = 1 in the Case Control Section. In MD Nastran, a new contact option, COPT, was introduced in BCTABLE to allow more advanced control on how the contact bodies should interact with each other. COPT is defined using the formula COPT= =A+10*B+1000*C, where the terms A, B, and C are defined as follows:


A: the outside of the solid elements in the body = 1: the outside will be in the contact description (DEFAULT) B (flexible bodies): the outside of the shell elements in the body = 1: both top and bottom faces will be in the contact description, thickness offset will be included (DEFAULT) = 2: only bottom faces will be in the contact description, thickness offset will be included = 3: only bottom faces will be in the contact description, shell thickness will be ignored = 4: only top faces will be in the contact description, thickness offset will be included = 5: only top faces will be in the contact description, shell thickness will be ignored = 6: both top and bottom faces will be in the contact description, shell thickness will be ignored Note if B = 6 for both bodies in a contact combination, then nodes that separate from a body, cannot come in contact again in the current step or in subsequent steps unless a different flag is chosen for one of the bodies B (rigid bodies): the rigid surface = 1: the rigid surface should be in the contact description (DEFAULT) C (flexible bodies): the edges of the body = 1: only the beam/bar edges are included in the contact description (DEFAULT) = 10: only the free and hard shell edges are included in the contact description = 11: both the beam/bar edges and the free and hard shell edges are included in the contact description Note that C has no effect if beam-to-beam contact is not switched on (i.e., BEAMB is left as 0 on BCPARA).


Figure 49-2

Contact Status Plot for Modal Analysis (Case 1)


The following BCTABLE entries are used for the SOL 103 analysis of Case 1: BCTABLE 1 SLAVE 2 0 FBSH 0. 0 1.+20 1 0. 0 0. 0. 0. 0. 3 60 60

It is important to note that the in-plane edge glued contact is activated by assigning value 60 for COPTS1 and COPTM1 in the 4th line of the BCTABLE option. The value 60 (B = 6) signifies that the edges are checked for contact without taking the shell thickness into account. Glued contact is defined by using a value of 3 for IGLUE in the 2nd line of the BCTABLE option. The value of IGLUE=3 allows moments to be transmitted across the contacting interface. JGLUE=0 in the 3rd field of the 3rd line ensures that glued nodes do not separate during the modal analysis. The contact status plot for Case 1 is presented in Figure 49-2. For the SOL 400 analysis of Case 2, the regular shell edge contact option is activated by assigning value of 10010 (B=1 and C=10) for COPTS1 and COPTM1 in the following BCTABLE entries: BCTABLE 0 SLAVE 2 0 FBSH MASTERS 1 1 SLAVE 2 0 FBSH MASTERS 1 0. 0 1.+20 0. 0 1.+20 1 0. 0 0. 1 0. 0 0. 0. 0. 0. 0. 0. 0. 0 10010 0 10010 10010 10010

BCTABLE

B = 1 in the definition of the COPT flags indicates that the thickness and both faces are considered for contact and C = 10 indicates that the shell edges are included in the contact description.

Loading and Boundary ConditionsFor the SOL 103 analysis (Case 1), the boundary conditions are applied through the following SPC cards. No additional loads are applied for this analysis. SPCADD SPC1 SPC1 SPC1 SPC1 2 1 1 3 3 1 126 126 123456 123456 3 1 25 1 44 THRU THRU THRU 65 23 44 23 86 107 128 149

For the SOL 400 analysis (Case 2), the loading and boundary conditions are applied with the following SPCD and SPC cards. SPCADD FORCE SPCD SPCD 2 1 1 1 1 1 1 3 3 3 3 0. 2. 2. .57735 2 4 .57735 3 3 .57735 2. 2.


SPC1 SPC1 SPC1

1 1 3

123456 123456 123456

36 391 1

THRU THRU

400 20

The loading and boundary conditions applied for Cases 1 and 2 are presented in Figure 49-3. For Case 1 the displacements u x = u y = z = 0 for all nodes and u z = x = y = 0 along all edges as shown in Figure 49-3 except that the in-plane translation boundary condition for are not applied at the interface of the contact bodies so that they do not conflict with the in-plane glued edge contact constraints.

Case 1

Case 2

Figure 49-3

Loading and Boundary Conditions for Cases 1 and 2

Solution ProcedureThe modal analysis SOL 103 procedure for Case 1 is defined with the following EIGRL entry: EIGRL 1 100. 500. 6 0 MASS

The six frequencies in the range 100 to 600 are requested through the above option. The SOL 4 00 nonlinear procedure for Case 2 is defined through the following NLPARM entry: NLPARM 1 0 The number of increments is provided in the 3rd field of the 1st line of NLPARM option. PFNT represents Pure Full Newton Raphson technique wherein the stiffness is reformed at every iteration. The value of KSTEP=1 along with PFNT option indicates that the stiffness matrix will not be updated between the 10 0.1 PFNT 1 0 PV 0 NO


convergence of a load increment and the start of the next load increment. PV indicates that the maximum vector component of the residuals will be checked for convergence. NO indicates that intermediate output will not be produced after every increment. The second line of NLPARM indicates that a tolerance of 0.1 will be used for convergence checking. The nonlinear procedure also deactivates Quasi-Newton, line search and cutbacks by assigning the value of 0 for MAXQN, MAXLS, and MAXBIS.

ResultsFrequencies of 6 modes extracted from the modal analysis are indicated in the Table 49-1. It clearly shows that the in-plane glued edge contact can be successfully used to assemble parts with different mesh densities, since the predictions are within a 2% error. The mode shapes of the 6 modes for rhombic plate are presented in Figure 49-4. Table 49-1 Comparison of Frequencies with NAFEMS Results SOL 103 Frequency Hz 134.18 204.37 270.59 284.56 341.13 385.79 NAFEMS Frequency Hz 133.95 201.41 265.81 282.74 334.45 NA

Mode Number 1 2 3 4 5 6

%Error 0.17 1.47 1.80 0.64 2.0 -


Mode 1: 134.18 Hz

Mode 2: 204.37 Hz

Mode 3: 270.59 Hz

Mode 4: 284.56 Hz

Mode 5: 341.13 Hz

Mode 6: 385.79 Hz

Figure 49-4

Mode Shapes of Thick Rhombic Plate


Figure 49-5 and Figure 49-6 demonstrate that the shell edge contact is properly detected as the top tube crushes the lower tube.Contact Status

50 % Load

100 % Load

Figure 49-5

Contact Status Plots for Square Tubes with Shell Edge ContactZ-Displacement

50 % Load

100 % Load

Figure 49-6

Original and Deformed Shapes of Square Tubes with Shell Edge Contact


Modeling TipsThe most important aspect in the shell edge contact analysis is the new COPT options introduced in BCTABLE. This gives more flexibility for users to define the interaction between different contact bodies (solid or shell or beam elements). Readers can observe the changes in results for the two cases presented in this chapter by removing the COPT options in BCTABLE. It is also possible to define the COPT options in the BCPARA and BCBODY options. The options ITOPBM, ITOPSH, and ITOPSL in the BCPARA option and COPTB in the BCBODY option can be used to define the same COPT option in cases where BCTABLE is not used in the model with BCONTACT=ALLBODY option. This is recommended as an exercise for the readers. It is important to remember that the general shell edge contact capability is activated by setting the beam to beam contact flag option BEAMB to 1 in BCPARA card.

Input FilesFile nug_49a.dat nug_49b.dat Description MD Nastran input for modal analysis of rhombic plate (Case 1) MD Nastran input for diagonal crushing of square tubes (Case 2)


SimXpert ExampleThis example will take you through Case 2 of the Shell Edge Contact Cases. The required input file can be downloaded by clicking the nug_49b.dat link in the Input Files section of this document.

Changing Units and Importing a Model


Creating Materials and Properties


Creating a Contact Table and Boundary Conditions


Setup Analysis


Attach and View Results

Animated MD User's Guide Ch. 49 - Shell Edge Contact

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