coupled
DESCRIPTION
ansysTRANSCRIPT
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
COMPUTER AIDED DESIGN[ME F 342]
Training in FEA using ANSYS
[P-6 Coupled Analysis][email protected]
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
One Field Influences another Field
THERMAL FIELD STRUCTURAL EFFECTS
MAGNETIC FIELD ELECTRIC EFFECTS
THERMAL FIELD FLUID EFFECTS
FLUID FIELD STRUCTURAL EFFECTS
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
A coupled-field analysis is an analysis that takes intoaccount the interaction (coupling) between two ormore disciplines (fields) of engineering.
The procedure for a coupled-field analysis dependson which fields are being coupled, but two distinctmethods can be identified sequential and direct.
Coupled-field analysis
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Sequential Method (Ex: Thermal-Structural)
Thermal stress analysis using sequential method involves two analyses
Thermal analysis
Jobname.rst
Structural analysis
Jobaname.rst
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
SequentialFirst do a steady state thermal analysis
Model with thermal elements Model thermal material properties Apply thermal loading Solve and review results
Then do static structural analysis Switch element types to structural Define structural material properties, including thermal expansion coefficient Apply structural boundary conditions Solve and review results
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Direct Method
The direct method usually involves just one analysis thatuses a coupled-field element type containing allnecessary degrees of freedom.
Coupling is handled by calculating element matrices orelement load vectors that contain all necessary terms.
An example of this is a piezoelectric analysis usingthe SOLID5 PLANE13, or SOLID98 elements.
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Direct MethodDirect method usually involves just one analysis thatuses a coupled field element type containing allnecessary degrees of freedom
Thermal analysis
Structural analysis
Jobname.rst
Prepare the model and mesh using one ofthe following coupled field element types PLANE 13 SOLID 5 SOLID 98
Apply both the structural and thermal loadsand constraints to the model
Solve and review both thermal and structuralresults
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Coupled Analysis | Theory
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
T1 | Coupled Analysis | Problem Statement A steel link, with no internal stresses, is pinned between two solid structuresat a reference temperature of 0 oC (273 K). One of the solid structures isheated to a temperature of 75 C (348 K). As heat is transferred from the solidstructure into the link, the link will attempt to expand. However, since it ispinned this cannot occur and as such, stress is created in the link. A steady-state solution of the resulting stress will be found to simplify the analysis.
Loads will not be applied to the link, only atemperature change of 75 degrees Celsius.The link is steel with a modulus of elasticityof 200 GPa, a thermal conductivity of 60.5W/m*K and a thermal expansion coefficientof 12e-6 /K.
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
T1 | Coupled Analysis | Thermal Physics!COUPLED ANALYSIS/TITLE, THERMAL to STRUCTURAL EXAMPLE
/PREP7 ! ENTER PREPROCESSOR
K,1,0,0 ! KEYPOINTSK,2,1,0L,1,2 ! LINE CONNECTING KEYPOINTS
ET,1,LINK33 ! Thermal Elt which can support Thermal-Structural Effect)R,1,4E-4, ! AREAMP,KXX,1,60.5 ! THERMAL CONDUCTIVITY
ESIZE,0.1 ! ELEMENT SIZELMESH,ALL ! MESH LINE
PHYSICS,WRITE,THERMAL ! WRITE PHYSICS ENVIRONMENT AS THERMALPHYSICS,CLEAR ! CLEAR THE ENVIRONMENT
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
T1 | Coupled Analysis | Structural Physics! CHANGES ELEMENT TYPES TO THEIR CORRESPONDING TYPES
ETCHG,TTS ! ELEMENT TYPE (THERMAL TO STRUCTURAL)! Automatic change from Thermal Elt to !corresponding structural Elt
MP,EX,1,200E9 ! YOUNG'S MODULUSMP,PRXY,1,0.3 ! POISSON'S RATIOMP,ALPX,1,12E-6 ! EXPANSION COEFFICIENT
PHYSICS,WRITE,STRUCT !WRITE PHYSICS ENVIRONMENT AS STRUCTPHYSICS,CLEAR
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
T1 | Coupled Analysis | Perform Thermal
/SOLUANTYPE,0 ! STATIC ANALYSIS
PHYSICS,READ,THERMAL ! READ IN THE THERMAL ENVIRONMENT
DK,1,TEMP,348 ! APPLY A TEMP OF 75 TO KEYPOINT 1
SOLVEFINISH
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
T4 | Coupled Analysis | Coupling /SOLU ! RE-ENTER THE SOLUTION PHASEPHYSICS,READ,STRUCT ! READ IN THE STRUCT ENVIRONMENT
LDREAD,TEMP,,,,,,RTH ! APPLY LOADS DERIVED FROM THML ENV!LDREAD, Lab, LSTEP, SBSTEP, TIME, KIMG, Fname, Ext,!KIMG: When used with the TEMP label, KIMG indicates how temperatures are to!be applied. KIMG = 0 is the only valid option for applying temperature loads.
TREF,273
DK,1,ALL,0 ! APPLY STRUCTURAL CONSTRAINTSDK,2,UX,0
SOLVEFINISH
!ENTER POSTPROCESSOR!List Results | Element Solution | Stress-X
Stress in the link should be a uniform 180 MPa in compression.
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
T2 | Coupled AnalysisThis example will demonstrate how much heat can beapplied to create desired amount of radial deflection ofinner surface of outer cylinder to accommodate innercylinder.Inner cylinder: Ri = 4 and RO = 5+0.025
Outer Cylinder: Ri = 5 and RO = 7. Find out radialdeflection at inner surface (Radius 5 unit)
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
T2 | Coupled Analysis | Expansion of a Hollow Cylinder
!Expansion of CYLINDER for shrink fit purpose
/PREP7
PCIRC,5,7,0,90 !CREATING A ANNULAR QUARTER CIRCLE
ET,1,PLANE55 !Thermal Elt which can support Thermal-Structural Effect)
MP,KXX,1,60.5 !SETTING THE CONDUCTIVITY
ESIZE,0.1
AMESH, ALL
PHYSICS,WRITE,THERMAL
PHYSICS,CLEAR
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
ETCHG,TTS ! CHANGE ELT TYPE (Thermal to Structural)
MP,EX,1,200E9 ! YOUNG'S MODULUS
MP,PRXY,1,0.3 ! POISSON'S RATIO
MP,ALPX,1,12E-6 ! EXPANSION COEFFICIENT
PHYSICS,WRITE,STRUCT ! WRITE PHYSICS ENVIRONMENT AS STRUCT
PHYSICS,CLEAR
FINISH
T2 | Coupled Analysis | Expansion of a Hollow Cylinder
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
/SOLU
ANTYPE,0 ! STATIC ANALYSIS
PHYSICS,READ,THERMAL
DL,3,,TEMP,1000 !APPLYING TEMP ON INNER ARC
DL,1,,TEMP,29 !APPLYING ROOM TEMP ON OUTER ARC
SOLVE
FINISH
T2 | Coupled Analysis | Expansion of a Hollow Cylinder
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
/SOLU !RE-ENTERING THE SOLVE MODE FOR STRUCT
ANALYSIS
PHYSICS,READ,STRUCT
LDREAD,TEMP,,,,,,RTH
TREF,29
DL,2,,UX,0
DL,4,,UY,0
SOLVE
FINISH
T2 | Coupled Analysis | Expansion of a Hollow Cylinder
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
T2 | Coupled Analysis | Expansion of a Hollow Cylinder
0.026 Unit deflection at inner radius 5
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Sequential vs. Direct methodSequential Direct
1. For coupling situations which do notexhibit a higher degree of non linearinteraction, the sequential method ismore efficient and flexible becauseone can perform the two analysisindependent of each other.
1. Direct field analysis is advantageouswhen the coupled field interaction ishighly non linear and is best solved ina single solution using a coupledformulation.
2. In a sequential thermal stress analysisone can perform a non lineartransient thermal analysis followed bya linear static stress analysis. One canthen use nodal temperatures from anyload step or time point in the thermalanalysis as loads for the stressanalysis.
2. Examples of direct coupling includepiezoelectric analysis, conjugate heattransfer with fluid flow, and circuitelectromagnetic analysis.
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
List of Elements Supporting Coupled Analysis