Add equilibrated constrained mixture model

[mrp089]

The model is defined here:

https://doi.org/10.1002/zamm.201700302
https://doi.org/10.1371/journal.pcbi.1008273

I will adapt Marcos's FEBio implementation to svFSI.

[mrp089]

@vvedula22 Is there a way to pass the current time and spatial position in MATMODELS.f to my material evaluation?

[vvedula22]

Try using this code as an example for passing the location of the integration point to MATMODELS.f. You can backtrace to see how the integration point is evaluated and passed to the stress subroutine. The global variable time is accessible through the module COMMOD which is already included in these subroutines.

[mrp089]

Thanks, @vvedula22!

[mrp089]

I need two different fiber orientations that are defined on the mesh.

I found an example to define a constant fiber direction, e.g. in https://github.com/SimVascular/svFSI-Tests/blob/master/05-struct/02-LV-Guccione-passive/Q1_svFSI.inp:

Add mesh: msh {
   [...]
   Fiber direction: (1.0, 0.0, 0.0)
   Fiber direction: (0.0, 1.0, 0.0)
}

I also found code to read mesh fibers (defined on each node/element?):

svFSI/Code/Source/svFSI/READMSH.f

Lines 334 to 380 in 8f4865a

	! Read fiber orientation
	flag = .FALSE.
	DO iM=1, nMsh
	lPM => list%get(msh(iM)%name,"Add mesh",iM)
	j = lPM%srch("Fiber direction file path")
	IF (j .EQ. 0) j = lPM%srch("Fiber direction")
	IF (j .NE. 0) THEN
	flag = .TRUE.
	EXIT
	END IF
	END DO
	IF (flag) THEN
	DO iM=1, nMsh
	lPM => list%get(msh(iM)%name,"Add mesh",iM)
	msh(iM)%nFn = lPM%srch("Fiber direction file path")
	IF (msh(iM)%nFn .NE. 0) THEN
	IF (rmsh%isReqd) err = "Fiber directions read from "//
	2 "file is not allowed with remeshing"
	ALLOCATE(msh(iM)%fN(msh(iM)%nFn*nsd,msh(iM)%gnEl))
	msh(iM)%fN = 0._RKIND
	DO i=1, msh(iM)%nFn
	lPtr => lPM%get(cTmp,
	2 "Fiber direction file path", i)
	IF (ASSOCIATED(lPtr))
	2 CALL READFIBNFF(msh(iM), cTmp, "FIB_DIR", i)
	END DO
	ELSE
	msh(iM)%nFn = lPM%srch("Fiber direction")
	IF (msh(iM)%nFn .NE. 0) THEN
	ALLOCATE(msh(iM)%fN(msh(iM)%nFn*nsd,msh(iM)%gnEl))
	msh(iM)%fN = 0._RKIND
	DO i=1, msh(iM)%nFn
	lPtr => lPM%get(fibN, "Fiber direction", i)
	rtmp = SQRT(NORM(fibN))
	IF (.NOT.ISZERO(rtmp)) fibN(:) = fibN(:)/rtmp
	DO e=1, msh(iM)%gnEl
	msh(iM)%fN((i-1)*nsd+1:i*nsd,e) = fibN(1:nsd)
	END DO
	END DO
	END IF
	END IF
	END DO
	ELSE
	msh(:)%nFn = 0
	END IF

@vvedula22 Do you have a sample input file that uses spatially varying fiber families?

[vvedula22]

I need two different fiber orientations that are defined on the mesh.

I found an example to define a constant fiber direction, e.g. in https://github.com/SimVascular/svFSI-Tests/blob/master/05-struct/02-LV-Guccione-passive/Q1_svFSI.inp:

Add mesh: msh {
   [...]
   Fiber direction: (1.0, 0.0, 0.0)
   Fiber direction: (0.0, 1.0, 0.0)
}

I also found code to read mesh fibers (defined on each node/element?):

svFSI/Code/Source/svFSI/READMSH.f

Lines 334 to 380 in 8f4865a

	! Read fiber orientation
	flag = .FALSE.
	DO iM=1, nMsh
	lPM => list%get(msh(iM)%name,"Add mesh",iM)
	j = lPM%srch("Fiber direction file path")
	IF (j .EQ. 0) j = lPM%srch("Fiber direction")
	IF (j .NE. 0) THEN
	flag = .TRUE.
	EXIT
	END IF
	END DO
	IF (flag) THEN
	DO iM=1, nMsh
	lPM => list%get(msh(iM)%name,"Add mesh",iM)
	msh(iM)%nFn = lPM%srch("Fiber direction file path")
	IF (msh(iM)%nFn .NE. 0) THEN
	IF (rmsh%isReqd) err = "Fiber directions read from "//
	2 "file is not allowed with remeshing"
	ALLOCATE(msh(iM)%fN(msh(iM)%nFn*nsd,msh(iM)%gnEl))
	msh(iM)%fN = 0._RKIND
	DO i=1, msh(iM)%nFn
	lPtr => lPM%get(cTmp,
	2 "Fiber direction file path", i)
	IF (ASSOCIATED(lPtr))
	2 CALL READFIBNFF(msh(iM), cTmp, "FIB_DIR", i)
	END DO
	ELSE
	msh(iM)%nFn = lPM%srch("Fiber direction")
	IF (msh(iM)%nFn .NE. 0) THEN
	ALLOCATE(msh(iM)%fN(msh(iM)%nFn*nsd,msh(iM)%gnEl))
	msh(iM)%fN = 0._RKIND
	DO i=1, msh(iM)%nFn
	lPtr => lPM%get(fibN, "Fiber direction", i)
	rtmp = SQRT(NORM(fibN))
	IF (.NOT.ISZERO(rtmp)) fibN(:) = fibN(:)/rtmp
	DO e=1, msh(iM)%gnEl
	msh(iM)%fN((i-1)*nsd+1:i*nsd,e) = fibN(1:nsd)
	END DO
	END DO
	END IF
	END IF
	END DO
	ELSE
	msh(:)%nFn = 0
	END IF

@vvedula22 Do you have a sample input file that uses spatially varying fiber families?

@mrp089 You can load fiber directions stored at element level from a vtu file as described here
svFSI_master.inp

   #  # Fiber directions may be loaded for some material models. Fiber
   #  # direction must be stored at the element level using the data
   #  # array name, "FIB_DIR", in the vtu format.
   #    Fiber direction file path: ./mesh/fibers_longitudinal.vtu
   #    Fiber direction file path: ./mesh/fibers_sheet.vtu

Note that the fiber directions are loaded within Add msh block in the input file. Here is an example:

https://github.com/SimVascular/svFSI-Tests/blob/master/06-ustruct/03-LV-Guccione-active/svFSI.inp

Add mesh: msh {
   [...]
   Fiber direction file path: mesh/P1/fibersLong.vtu
   Fiber direction file path: mesh/P1/fibersSheet.vtu
}