108 - finite element method

08 - finite element method -

density growth - theory

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2finite element method

from continuous problem…

… to linearized discrete initial boundary value problem

• temporal discretization

• linearization

• spatial discretization• staggered/simultaneous

implicit euler backwardfinite element methodnewton raphson iterationgateaux derivative

3finite element method

sequential solution - element based

staggered solution - integration point based

simultaneous solution - node point based

huiskes, weinans, grootenboer, dalstra, fudala & slooff [1987],carter, orr, fhyrie [1989], beaupré, orr & carter [1990], weinans,huiskes & grootenboer [1992], [1994], jacobs, levenston, beaupré,simo & carter [1995], huiskes [2000], carter & beaupré [2001]

weinans, huiskes & grootenboer [1992], harrigan & hamilton [1992],,[1994], jacobs, levenston, beaupré,simo & carter [1995]

jacobs, levenston, beaupré,simo & carter [1995], fischer, jacobs,levenston & carter [1997], nackenhorst [1997], levenston [1997]]

4finite element method

from strong form … to weak form (1d)• strong / differential form

• weak / integral form - nonsymmetric

• strong form / residual format

• integration by parts• integral theorem & neumann bc‘s• weak form / integral form - symmetric

5finite element method

integration point based

strong form

• cast it into its residual format

• with residual

• start with nonlinear mechanical equilibrium equation

6finite element method

integration point based

boundary conditions

• dirichlet / essential boundary conditions

• neumann / natural boundary conditions

• strong / differential form

7finite element method

integration point based

weak form

• mulitplication with test function & integration

• weak form / nonsymmetric

• strong / differential form

8finite element method

integration point based

weak form

• gauss theorem & boundary conditions

• integration by partsQuickTime™ and a

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• weak form / symmetric

9finite element method

integration point based

spatial discretization

• interpolation of test functions

• interpolation of trial functions

• discretization

10finite element method

integration point based

discrete residual

• discrete residual format

• discrete residual

QuickTime™ and aTIFF (Uncompressed) decompressor

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11finite element method

integration point based

discrete residual

• discrete residual

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• residual of mechanical equilibrium/balance of momentum

check in matlab!

12finite element method

integration point based

linearization

• incremental residual

• system of equations

• linearization / newton raphson scheme

• incremental iterative update

13finite element method

integration point based

linearization

• stiffness matrix / iteration matrix

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• linearization of residual wrt nodal dofs

14finite element method

integration point based

linearization

• stiffness matrix / iteration matrix

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• linearization of residual wrt nodal dofs

check in matlab!

15finite element method

integration point based

constitutive equations

with

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• constitutive equations - given calculate

and from

16finite element method

integration point based

constitutive equations

• stress calculation @ integration point level

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• constitutive equations - given calculate

check in matlab!

17finite element method

integration point based

constitutive equations

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.• constitutive equations - given calculate

• temporal discretization - euler implizit

with

with

• local newton iteration

18finite element method

integration point based

constitutive equations

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check in matlab!

• residual of biological equilibrium / balance of mass

• discrete density update

19finite element method

integration point based

constitutive equations

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depends on time discretization

with

• constitutive equations - given calculate

20finite element method

integration point based

constitutive equations

• tangent operator / constitutive moduli

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• linearization of stress wrt deformation gradient

check in matlab!

21finite element method

integration point based

staggered solution

loop over all time stepsglobal newton iteration

loop over all elementsloop over all quadrature pointslocal newton iteration to determine

determine element residual & partial derivativedetermine global residual and iterational matrixdetermine

determine state of biological equilibrium

22finite element method

integration point based

staggered solution

loop over all time stepsglobal newton iteration

loop over all elementsloop over all quadrature pointslocal newton iteration to determine

determine element residual & partial derivativedetermine global residual and iterational matrixdetermine

determine state of biological equilibrium