1、PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-1SECTION 10LAGRANGIAN BOUNDARY CONDITIONS第1页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-2SINGLE POINT CONSTRAINT-SPCnPrevents a point moving in a particular direction.nMust be initialized in the Case Control sect
2、ion:uSPC=SIDnAny SPCn entries not selected in case control are ignored.nThe displacement coordinate system of the constrained gridpoint determines the direction that the constraint is applied in.nCan be used to model boundary conditions and planes of symmetry.nAny component in grid coordinate system
3、 can be constrained.nComponents in a grid coordinate system are referred by digits 1 to 6.Any combination is possible,e.g.23,156.SPC=100 BEGIN BULK.SPC,100,27,123SPC1,100,156,19,THRU,28第2页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-3ROTATIONAL BOUNDARY CONDTION SPC2nUsed to
4、model rotational boundary conditions on gridpoints.nMust be selected in Case ControlSPC=SID 第3页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-4SINGLE POINT CONSTRAINT IN LOCAL COORDINATES SPC3nUsed to define a single point constraint in a local coordinate system or a cascade of
5、 two local coordinate systems.nMust be selected in Case Control.SPC=SID 第4页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-5ENFORCED MOTIONnPrescribes the motion of grid points.nForce of pressure loading-TYPE=2 in TLOAD1 definition.nMust be selected in Case Control.nAny loading(
6、TLOADn entry)not selected in Case Control is ignored.nEnforced motion can be prescribed in a local coordinate system.第5页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-6ENFORCED GRID POINT MOTIONnSpecified points can have their velocity set.nVelocity-TYPE=2 in TLOAD1 definitionT
7、LOAD1,100,110,2,120nDAREA defines magnitude of translational or angular velocity per DOF.nFORCE defines magnitude and direction of translational velocity.nMOMENT defines magnitude and direction of angular velocity.nVelocity can vary arbitrarily with time.nThe TABLED1 entry gives the variation of vel
8、ocity.TLOAD=100 BEGIN BULK.TLOAD1,100,110,2,120TABLED1,120,+,0.0,0.0,1.0,1.0,ENDTFORCE,110,27,-6.0,1.0第6页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-7ENFORCED MOTIONnFORCE in CORDXXXuIf on a FORCE entry a CID is referenced,the enforced motion is processed in a local coordina
9、te system.FORCE,110,27,2,-6.0,1.0 第7页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-8RIGID WALLS-WALLnModels a rigid plane which specified”slave”points can not penetrate.nUsed to model hard,undeformable target.nDefine a point on the wall and a vector perpendicular to it,pointin
10、g towards the model.nTwo kinds of contact:uPENALTY Method:Allowed penetration.Force increases as nodes penetrate deeper.Can have friction.uKINEMATIC MethodNodes are put back on the Surface.Impulse is applied to Nodes.Can not have friction.WALL,101,0.0,0.0,0.0,0.0,0.0,1.0,102,+,PENALTY,0.2SET1,102,1,
11、THRU,1999第8页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-9TIED CONNECTIONSnTwo meshes with different coarseness are permanently tied together during the analysis.nAllows beam,shell and solid meshes to be tied together without the need for coinciding grid point locations.nPoss
12、ible gaps between the meshes can be requested to be closed.nNot recommended in areas where stress peaks or failure is expected.nThree types of tied connections:uTwo surfaces tied togetheruGrid points tied to a surfaceuShell edge tied to a shell surface第9页，共17页。PAT328,Section 3,March 2001DYT101,Secti
13、on 10,September 2002S10-10TWO SURFACE TIED TOGETHER(RCONN)nTwo surfaces are permanently tied together during the analysis.nMaster surface:always attached to the coarse mesh.nSlave surface:always attached to the finer mesh.nLumping forces and velocities according to shape functions.nForces:uslave poi
14、nts master pointsnVelocities:umaster points slave pointsnExample:uTwo solids are tied together along their common surface 7 and 8.RCONN,1,SURF,SURF,7,8第10页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-11GRID POINTS TIED TO A SURFACE(RCONN)nIndividual grid points are tied to a
15、surface.nSlave surface type is GRID and OPTION must be set to NORMAL.nMaster surface must be defined as a set of segments.nOnly the translational degrees of freedom are tied.nExample:uThe node 1 to 10 of a beam mesh are tied to the shell surface 7.RCONN,1,GRID,SURF,3,7,NORMALSET1,3,1,THRU,10第11页，共17
16、页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-12SHELL EDGE TIED TO A SHELL SURFACEnConnects beams or shell-edges to shell elements.nSlave surface type is GRID and OPTION must be set to SHELL.nMaster surface must be defined as a set of segments.nTranslational and rotational degrees
17、 of freedom are tied.nExample:uThe edge grid points 1 to 10 of a shell mesh are tied to the shell surface number 7.RCONN,1,GRID,SURF,3,7,SHELLSET1,3,1,THRU,10第12页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-13RIGID BODY ELEMENTS(RBE2)nDefines a set of grid points that form a
18、rigid body.nThis entry allows particular degrees of freedom of a set of grid points to be tied together so that they always move the same amount.nUsed to model spotwelds,but elements can not fail.nExample:uNodes 1 to 28 will have the same displacement in x and z-direction as node 55.RBE2,12,55,13,1,
19、THRU,28nInstead of defining tied components,it is also possible to use the FULLRIG option.nThis causes the set of grid points to behave like a single rigid body element.nThe name of the RBE2 will become FR.nExample:uNodes 1 to 28 and 55 will behave like a rigid body.The name will be FR12.RBE2,12,55,
20、FULLRIG,1,THRU,28第13页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-14KINEMATIC JOIN(KJOIN)nShell to solid grid point connection.nJoins shell to solid elements by applying kinematic conditions to the shell grid points.nA normal JOIN would result in a hinge connection in which o
21、nly the translational DOFs are coupled.nSolves the closure problem for the different DOF of shell and solid elements.nConstitutes stiff connection between shells and solids Stiffness of join is user defined.nExample:uKjoin between solid nodes 30,40 and 50 and shell nodes 32,42 and 52.uAll nodes with
22、in a tolerance of 1e-5 are connected.KJOIN,2,333,1e-5,0.5SET1,333,30,32,40,42,50,52Rotation at C follows from the motion of the system Ri R1R2R3CSOLIDSSHELLS第14页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-15BREAKABLE JOIN(BJOIN)nDefines a breakable join between shell or beam
23、 grid points.nJoins shell or beam grid points and allows for the break of the join when a failure criterion is satisfied.nFailure models:uConstant Force or MomentuComponents FailureuSpotweld like behavioruUser definednBreakable join can have offset(spotweld modeling)nExample:uBreakable join that fails after 1.e6 is reached.uAll nodes within a tolerance of 1e-4 are connected.BJOIN,1,333,1.E-4,FOMO,1.E6SET1,333,31,THRU,2000第15页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-16第16页，共17页。PAT328,Section 3,March 2001DYT101,Section 10,September 2002S10-17演讲完毕，谢谢观看！第17页，共17页。
