FINITE ELEMENT ANALYSIS OF HUMAN FEMUR 4 TH I NT. C ONFERENCE OF M ULTIPHYICS, L ILLE, F RANCE, 9-11 D EC 09 H. A. K HAWAJA (PhD Student, Dept. of Engineering) A. N AIK (PhD Student, Dept. of Material Sciences) K. P ARVEZ (Professor; Research Centre for Modelling & Simulation)

P OINTS FOR D ISCUSSION  I NTRODUCTION  F EMUR C AD D EVELOPMENT  Laser 3-D Scanning  CAD Model  Marrow Cavity (Approx.)  F INITE E LEMENT A NALYSIS  Finite Element Modelling  Material Properties and Assumptions  Loading and Boundary Conditions  Finite Element Analysis Results  S UMMARY & C ONCLUSION  REFERNCES  A CKNOWLEDGEMENTS H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC 09 2

I NTRODUCTION H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC 09 3 FEMUR  Largest Human Bone  Single Support Member  Less Flexible (Stiff)  Anisotropic Material  This work addresses:  Load Bearing limit of Femur  Natural Safety Factor  Results will aid in deciding substitute material for bone

F EMUR C AD D EVELOPMENT H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC 09 4  Laser 3-D Scanning: OBJECT LASER SCAN ROTATION COORDINATES CLOUD

 CAD Model: H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC 09 5 F EMUR C AD D EVELOPMENT Marrow Cavity is developed based on approximation

F INITE E LEMENT M ODELLING H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC 09 6  Finite Element Mesh:  Tetrahedral 20-noded 186 structural solid element has been used  Mesh sensitivity analysis is carried out to ensure the quality of results  Mesh has been refined in the regions of high Gradients

F INITE E LEMENT M ODELLING H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC 09 7  Material Properties & Assumptions:  Originally Bone material is anisotropic but assumed to be isotropic because complete femur was taken for analysis; a piece of bone could be solved for anisotropic solution but not the complete bone.  The bone Young’s modulus varies between 10 to 20 GPa. The Poisson’s ratio is about 0.3 *. “For linear static analysis stresses doesn’t depend on modulus of elasticity”  Physiological conditions has been ignored for time being; e.g. muscle stresses. x y z *BAOHUA, J., HUAJIN, GAO., (2004). Journal of Mechanics and Physics of Solids, 52,

F INITE E LEMENT M ODELLING H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC 09 8  Loading & Boundary Conditions:  Axial Load  Bending Load  Based on its position w.r.t. Its orientation  Load is varied until failure

H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC 09 9 F INITE E LEMENT M ODELLING  Finite Element Results (Compression):  Displacement Contour Plot 1 Units = 1 metres

H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC F INITE E LEMENT M ODELLING  Finite Element Results (Compression):  Von-Mises Stress Contour Plot 1 Units = 1 Pascal Max. Stress regions coincides under axial and bending load

F LUIDIZED B ED H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC F INITE E LEMENT M ODELLING  Finite Element Results (Based on 70 Kg Human Weight):  69 Kg is limit load under bending load and 414 Kg is limit load under axial load. *Failure limit is 100 MPa (BAOHUA, J., HUAJIN, GAO., (2004). Journal of Mechanics and Physics of Solids, 52, ) Loading (Kg) Max. Stress (Compression) Max. Stress (Bending) (Design Value) * *

S UMMARY & C ONCLUSION H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC  Summary:  3-D CAD Model has been developed via Laser Scanning  Approximations have been applied on material and model  Finite Element Analysis has been conducted  Results are evaluated  Conclusion:  Natural Margin of Safety under 35 Kg Design Load (70Kg average Human) of compression is  Natural Margin of Safety under 35 Kg Design Load (70Kg average Human) of bending is Human Femur is designed to bear 10 times more load compared to load at normal conditions. It has also been found out Femur resistance to fracture under compression is approx. 5 times to the bending.

F UTURE W ORK H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC  Evaluated results are the indicative of the mechanical properties of substitute material for bones.  Physiological conditions may be involved to increase the accuracy of results.  Whole human bone structure may be solved via FEM under the availability of computational resources.

R EFERENCES H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC ALBERT. H., ET AL, (1972). Journal of Biomechanics, 5, ANSYS® Multiphysics FEM Package, Release 11.0 ANSYS® Technical Manuals, Release 11.0 Documentation for ANSYS® BAOHUA, J., HUAJIN, GAO., (2004). Journal of Mechanics and Physics of Solids, 52, CURREY, J., D., (1979). Journal of Biomechanics, 12, CURREY, J., D., (1988). Journal of Biomechanics, 21, 2, LAWRENCE, J., (1984). IEEE Transactions on Biomedical Engineering, 31,12. WEINER, S., WAGNER, H., D., (1998). Annual Review Material Science, 28.

A CKNOWLEDGEMENTS  Institute of Space Technology (IST) – Pakistan  Cambridge Commonwealth Trust – Cambridge, UK  Research Centre for Modelling & Simulation, National University of Sciences & Technology (NUST) - Pakistan H. A. K HAWAJA MULTIPHYSICS 2009, L ILLE, F RANCE, 9-11 D EC 09 15

T HANK Y OU C ONTACT H ASSAN K HAWAJA Webpage: