Threaded connectors are commonly used components in the piping and offshore industry. The example presented here is a simulation of a simple threaded connection.
The analysis occurs in two load steps:
| Load Step 1: Internal pressure and tensile force loads are applied to a 2D model. |
| Load Step 2: A bending load is applied to the extruded 3D model. |
Because the geometry and loadings in the first load step are axisymmetric in nature, the analysis begins with a 2D axisymmetric model to solve for internal pressure and tensile loadings. Using a 2D-to-3D analysis, the 2D deformed mesh (left) is extruded to a new 3D mesh (right):
The analysis continues on the 3D model, on which a bending load is applied.
The 2D axisymmetric model of the simple threaded connection has two contact pairs:
A flexible-to-flexible contact pair at the threads.
A rigid-to-flexible redundant contact pair at the top face.
The rigid-to-flexible contact pair plays no role in the 2D axisymmetric analysis. It is required later, however, for applying the bending load on the extruded 3D model.
Elastic-plastic material properties are used with bilinear isotropic hardening (TB,PLAS,,,,BISO). Internal pressure is applied on the inner surfaces. Tensile force loading is applied on the top face. A static analysis with large-deflection effects (NLGEOM,ON) is performed on the 2D axisymmetric model.
Following are the equivalent stress and total mechanical strain plots from the 2D axisymmetric analysis:
| Step | Description | Command | Comments |
|---|---|---|---|
| 1 | Initiate the 2D-to-3D analysis. | MAP2DTO3D,START,1,38 | Begins the analysis at the last (38th) substep of the first load step. |
| 2 | Extrude the 3D mesh from the 2D deformed mesh. | EEXTRUDE,AXIS,36 | Revolves the 2D deformed geometry about the global Y axis with 36 elements in the hoop direction. |
| 3 | Map boundary conditions and loads. | MAP2DTO3D,FINISH | Transfers boundary conditions, pressure loads, applied nodal forces, applied nodal displacements, and applied nodal temperatures from the 2D mesh to the corresponding entities in the extruded 3D model |
| 4 | Map solution variables. | MAP2DTO3D,SOLVE | Transfers nodal and element solutions from the 2D model to the 3D model and initiates rebalancing. |
The following figures show the equivalent stress plots from the 2D axisymmetric model to the extruded 3D model:
After performing a multiframe restart, the analysis resumes using the new 3D model, where a bending load is applied:
| Step | Description | Command(s) | Comments |
|---|---|---|---|
| 1 | Restart the analysis. | ANTYPE,,RESTART,1,39 | Performs a multiframe restart at the last converged substep (after MAP2DTO3D,SOLVE). In this case, it is substep 39. |
| 2 | Apply the bending load. |
CNKMOD,9,12,5 D, 999,ROTZ,-0.00349 | This contact pair was created in the 2D model and transferred to the extruded 3D model automatically during the 2D-to-3D analysis. The CNKMOD command changes the behavior of the contact pair to bonded. The D command applies the bending load on the pilot node of the rigid-to-flexible contact pair (on the top of the 3D model). |
| 3 | Solve and review results. | SOLVE | Solves the 3D analysis and enables you to review results via standard output commands (PLNSOL and *GET) in POST1. |
For more information, see Input File for This Example.
The following figure shows the stress plot from the 3D analysis with bending load:
Following is the input file used in this example 2D-to-3D analysis of a simple threaded connection:
! Input file for Map2dto3d example number 1 fini ! BILL BULAT, 12/30/2023 (FOR TESTING PURPOSES) /cle ! BILL BULAT, 12/30/2023 /sys,del Map2dto3d_Example1*.png /fil,Map2dto3d_Example1 /PREP7 !************************************************ !Create the Geometry of Threaded Connection !************************************************ k,1,75 k,2,50 k,3,50,10 k,4,62,10 k,5,62,15 k,6,60,15.5 k,7,60,17.5 k,8,62,18 k,9,62,20 k,10,60,20.5 k,11,60,22.5 k,12,62,23 k,13,62,25 k,14,60,25.5 k,15,60,27.5 k,16,62,28 k,17,62,30 k,18,62,35 k,19,75,35 l,1,2 l,2,3 l,3,4 l,4,5 l,5,6 l,6,7 l,7,8 l,8,9 l,9,10 l,10,11 l,11,12 l,12,13 l,13,14 l,14,15 l,15,16 l,16,17 l,17,18 l,18,19 l,19,1 al,all lsel,s,,,5,15 lgen,2,all,,,,,,,0 allsel,all allsel,below,area lsel,invert lplot LGEN, ,all, , ,-0.9,0.2, , , ,1 allsel,all ldel,20 k,20,61.1,15.2 l,21,20 k,41,61.1,13.2 l,20,41 k,42,59.1,12.7 l,41,42 k,43,59.1,11 l,42,43 k,51,61.1,40 l,31,51 k,52,66,40 l,51,52 k,53,66,100 l,52,53 k,54,50,100 l,53,54 k,55,50,35 l,54,55 k,56,50,11 l,55,56 l,56,43 allsel,all allsel,below,area lsel,invert al,all k,100,45,100 k,101,71,100 l,100,101 allsel,all !************************************************ !Material Properties !************************************************ !BISO Material MP,EX,1,3e06 MP,PRXY,1,0.3 ET = 3e05 EP = 3e06*ET/(3e06-ET) TB,PLAS,1,,,BISO TBDATA,1,9e03,EP mp,mu,2,0.1 !Meshing et,1,182 keyopt,1,3,1 keyopt,1,6,1 esize,3 lsel,s,,,4,7 lsel,a,,,9,16 lsel,a,,,20,34 lesize,all,0.8 allsel,all amesh,all !************************************************ !Create contact pairs !************************************************ et,2,169 et,3,172 keyopt,3,10,2 lsel,s,,,5,17 nsll,,1 esln mat,2 type,3 real,3 esurf lsel,s,,,20,32 nsll,,1 esln mat,2 type,2 real,3 esurf allsel,all RMODIF,3,10,0.0245 !Create redundant contact pair for applying bending load in 3D model et,4,169 et,5,172 keyopt,5,2,0 keyopt,5,10,2 lsel,s,,,37 nsll,,1 esln type,5 real,5 mat,5 esurf lsel,s,,,41 type,4 real,5 lmesh,41 allsel,all !Create a pilot node for contact pair ID 5 REAL,5 TYPE,4 TSHAP,PILO N,999, 0,100,0.0 E,999 allsel,all !************************************************ !Create components for applying BCs and Loading !************************************************ lsel,s,,,1 nsll,,1 cm,nd_fixed,node d,all,all allsel,all lsel,s,,,38,39 lsel,a,,,2 nsll,,1 cm,nd_pres,node allsel,all lsel,s,,,37 nsll,,1 cm,nd_force,node allsel,all /PBC,ALL, ,1 /show,png eplot /show,close FINISH !************************************************ ! 2D analysis !************************************************ /solu time,1 outres,all,all eresx,no rescontrol,define,all,1 nsub,50,10000,10 nlgeom,on cmsel,s,nd_pres sf,all,pres,4000 cmsel,s,nd_force f,all,fy,6000 allsel,all solve finish !/eof /post1 /out, set,last *get,substep_last,active,,set,sbst ! BILL BULAT, 12/30/2023 pars ! BILL BULAT, 12/30/2023 fsum rsys,solu /show,png /graphics,full plnsol,epto,eqv *get,max_eptoeqv,plnsol,0,max *get,min_eptoeqv,plnsol,0,min plnsol,epto,x *get,max_eptox,plnsol,0,max *get,min_eptox,plnsol,0,min plnsol,s,eqv *get,max_seqv,plnsol,0,max *get,min_seqv,plnsol,0,min plnsol,s,x *get,max_sx,plnsol,0,max *get,min_sx,plnsol,0,min plnsol,cont,pres *get,max_pres,plnsol,0,max *get,min_pres,plnsol,0,min plnsol,cont,pene *get,max_pene,plnsol,0,max *get,min_pene,plnsol,0,min plnsol,cont,slid *get,max_slid,plnsol,0,max *get,min_slid,plnsol,0,min /show,close *status finish !************************************************ ! Map2dto3d Analysis !************************************************ /clear,nostart /fil,Map2dto3d_Example1 parr ! BILL BULAT, 12/30/2023 /solu MAP2DTO3D,START,1,substep_last ! BILL BULAT, 12/30/2023 allsel,all shpp,off EEXT,Axis,36 allsel,all eresx,no MAP2DTO3D,FINISH MAP2DTO3D,SOLV finish /post1 /out, !Settings for reverse video plot /rgb,index,100,100,100, 0 /rgb,index, 80, 80, 80,13 /rgb,index, 60, 60, 60,14 /rgb,index, 0, 0, 0,15 jpgprf,,,1 /VIEW, 1, 0.646367088986E-01, 0.223695995480 , 0.972513340510 /ANG, 1, -0.946434514981 set,last fsum rsys,solu /show,png /graphics,full plnsol,epto,eqv *get,max_eptoeqv,plnsol,0,max *get,min_eptoeqv,plnsol,0,min plnsol,epto,x *get,max_eptox,plnsol,0,max *get,min_eptox,plnsol,0,min plnsol,s,eqv *get,max_seqv,plnsol,0,max *get,min_seqv,plnsol,0,min plnsol,s,x *get,max_sx,plnsol,0,max *get,min_sx,plnsol,0,min plnsol,cont,pres *get,max_pres,plnsol,0,max *get,min_pres,plnsol,0,min plnsol,cont,pene *get,max_pene,plnsol,0,max *get,min_pene,plnsol,0,min plnsol,cont,slid *get,max_slid,plnsol,0,max *get,min_slid,plnsol,0,min /show,close /out, *status finish !************************************************ ! 3D analysis with Bending load in Restart Run !************************************************ /clear,nostart /fil,Map2dto3d_Example1 parr ! BILL BULAT, 12/30/2023 /solu antype,,restart,1,substep_last+1 ! BILL BULAT, 12/30/2023 cnkmod,9,12,5 allsel,all d,999,rotz,-0.00349 nsub,10,10000,5 allsel,all solve finish /post1 /out, /VIEW, 1, 0.646367088986E-01, 0.223695995480 , 0.972513340510 /ANG, 1, -0.946434514981 set,last fsum rsys,0 /show,png /graphics,full plnsol,epto,eqv *get,max_eptoeqv,plnsol,0,max *get,min_eptoeqv,plnsol,0,min plnsol,epto,x *get,max_eptox,plnsol,0,max *get,min_eptox,plnsol,0,min plnsol,s,eqv *get,max_seqv,plnsol,0,max *get,min_seqv,plnsol,0,min plnsol,s,x *get,max_sx,plnsol,0,max *get,min_sx,plnsol,0,min plnsol,cont,pres *get,max_pres,plnsol,0,max *get,min_pres,plnsol,0,min plnsol,cont,pene *get,max_pene,plnsol,0,max *get,min_pene,plnsol,0,min plnsol,cont,slid *get,max_slid,plnsol,0,max *get,min_slid,plnsol,0,min /show,close /out, *status finish