1. Page 1 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CHAPTER 12 - CONTACT

2. Page 2 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTENTS Contact definition Master Slave Surface Contact Single Surface Contact Adaptive Contact Penalty Method in Contact Contact Force Contact Search Contact Options Contact Output

3. Page 3 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTACT DEFINITION Defines interaction between Lagrangian gridpoints and elements Three types of contact exist Master Slave Contact Single Surface or Self Contact Adaptive or Eroding Contact

4. Page 4 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes Slave Surface Master Surface MASTER-SLAVE CONTACT Prevents two surfaces from penetrating each other Fast and efficient contact algorithm Example:Contact between surfaces 202 and 102 CONTACT,1,SURF,SURF,202,102 SURFACE, 102,, PROP, 103 SURFACE, 202,, MAT, 203

5. Page 5 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes SINGLE SURFACE CONTACT Prevents a surface penetrating itself Useful for modeling buckling problems where the points of contact can not be determined before the analysis In case it is not known beforehand where contact will occur or which parts of a structure will be in contact all the different parts of that structure can be put into a single contact surface definition. Expensive to use, but very powerful Easy to use Example:Self contact of surface 204 CONTACT, 1, SURF,, 204 SURFACE, 204,, ELEM, 204

6. Page 6 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes ADAPTIVE CONTACT Defines interaction between Lagrangian objects that can fail Upon element failure the element is removed from the calculation and the contact surface is automatically updated Automatic generation of initial contact surface Example:Contact between objects with properties 202 and 102 CONTACT, 1, PROP, PROP, 202, 102,,,, + +,,,, YES

7. Page 7 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTACT METHOD OF MSC.Dytran Contact uses Penalty Method Allowed penetration of nodes Forces perpendicular to face normals to push slave node back Conservation of momentum Contact is based upon the Master Face - Slave Node Algorithm Slave nodes will look for contact with master faces Therefore contact in MSC.Dytran is not symmetrical!!! Exception is Single Surface Contact

8. Page 8 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTACT SEARCH ALGORITM Four regions: Do nothing if free grid point Check for penetration if inside monitoring region If penetrated apply force to bring slave point to surface If penetrated to deeply do not apply any force (missed contact)

9. Page 9 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes Penetration region depth, d p, can be user defined Use to maintain stability of structure Monitoring region width, d m, can be user defined Monitoring region is dynamic: it will be increased automatically when slave nodes have high velocity CONTACT SEARCH ALGORITM (Continued)

10. Page 10 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes Contact can occur from different sides - TOP side: slave nodes will stay above the master faces CONTACT, 1, SURF, SURF, 202, 102,,,, + +,, TOP - BOTTOM side: slave nodes will stay beneath the master face CONTACT, 1, SURF, SURF, 202, 102,,,, + +,, BOTTOM Automatic initialization of contact side when side is set to option BOTH. MSC.Dytran will set option for each node to either TOP or BOTTOM and option can change during simulation Use only when initially a gap exists between master and slave surface Required to use BOTH option for self surface contact CONTACT, 1, SURF, SURF, 202, 102,,,, + +,, BOTH CONTACT SEARCH ALGORITM (Continued)

11. Page 11 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes To determine TOPor BOTTOM contact uniquely the normal of the faces of the contact surfaces must all point in the same direction Example of top side contact: Initial penetration would occur when BOTTOM option was defined No initial penetration would occur when BOTH was defined: the initial geometrical layout determines from which direction the contact occurs CONTACT SEARCH ALGORITM (Continued)

12. Page 12 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTACT FORCE Slave node penetrates master segment from time n to n + 1 over a distance  Slave Node Penetration Region n (normal) n n + 1  Contact force computed from penetration FACT =.1 by default to avoid instabilities A factor of 1.0 would result in the Lagrange multiplier method

13. Page 13 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTACT FORCE (continued) Conservation of impulse The computed contact force is put on the slave node in order to bring it back to the master surface The same, but reversed force will be distributed to the nodes of the master surface

14. Page 14 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTACT OPTIONS - THICK Shell thickness can be taken into account for contact The penetration region is increased with half of a user defined factor of the master element thickness. The position of the slave node used in the penetration calculation is update with half of a user defined factor of the slave element thickness. penetration  m 2 ss

15. Page 15 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTACT OPTIONS - GAP A gap can be taken into account for contact The penetration region is increased with the value of GAP penetration  g

16. Page 16 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTACT OPTIONS - FRICTION Friction may be included in the contact The coefficient of friction at low and high speed may be different: By default no friction Example: Master-Slave contact between surface 3 and 7 with a static friction coefficient 0.3 CONTACT, 1, SURF, SURF, 3, 7, 0.3

17. Page 17 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTACT OPTIONS - (DE)ACTIVATION Contact can be activated or deactivated to save calculation time - TSTARTTime at which contact is activated (default t = 0.) - TENDTime at which contact is deactivated (default ENDTIME) Example: Contact active between 0.1 and.5 of a Master-Slave contact between surfaces 3 and 7 CONTACT, 1, SURF, SURF, 3, 7,,,,+ +,,,,,,,,, + +, 0.1, 0.5

18. Page 18 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTACT OUTPUT Output is presently only available for timehistory and is specified using the following Case Control commands: CONTOUT -indicates variables to be output CONT -indicates a SET containing contact surface ID’s for which output is requested STEPS/TIMES - Time-interval at which output is requested TYPE -indicates time-history format (only TIMEHIS) SAVE - interval at which a new output file is to be created Example: TYPE (Contact_File) =TIMEHIS CONTOUT (Contact_File) =XFORCE, YFORCE, ZFORCE, FMAGN, AMAGN CONTS (Contact_File) =10 SET 10 = 111 TIMES (Contact_File) =0.0 THRU END BY 1.0e-4 SAVE (Contact_File) =1000000

19. Page 19 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes CONTACT VERSIONS DRAWBEAD Suited for modeling a drawbead

20. Page 20 Introduction to Lagrange Chapter 12 - ContactMSC.Dytran Seminar Notes APPLICATION OF DRAWBEAD IN CONTACT A drawbead model is implemented in the CONTACT algorithm for sheet metal stamping. A list of grid points must be created to define the location of the drawbead line. The grid points are then used to define a row of dummy rod elements representing the drawbead. An RCONN rigid connection is used to couple the drawbead grid points and the tool. The user need to define restraining force/unit of drawbead length on the contact card (“DRAWBEADF” entry ) and use “DRAWBEAD” flag as “VERSION” on the CONTACT card. Example: CROD,501, 5, 5001, 5002 SET1, 51, 5001, 5002 $ List of grid points at drawbead location PROD, 1, 5, 1.0E-20 $ Dummy properties for rod doesn’t add mass or inertia effects MAT1, 5, 1.0E-20,, 0.3, 1.E-10 $ Define a rigid connection between drawbead grid points (GRID Set =51) and the tol (SURFACE ID=11). $ RCONN,1,GRID,SURF, 51, 11,,,, + +,,,,,,,,, + +, YES $ Define the drawbead restraining force per unit length on the CONTACT Card. The force is applied via GRID SET = 51 on the blank (SURFACE ID=1) $ CONTACT,1, GRID, SURF, 51, 1,,,,+ +,DRAWBEAD,,,,1.0,,,,+ +,,,,,,,,, + +,drawbeadf = force/length