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1. Authors:
Surya Pratap Singh ,Tarun Bhardwaj , Mukul Shukla
MED, MNNIT, Allahabad
Lattice Modeling and Finite Element Simulation for
Additive Manufacturing of Porous Scaffolds
IEEE International Conference on
Advances in Mechanical, Industrial, Automation and Management Systems
(AMIAMS 2017)
Department of Mechanical Engineering
Motilal Nehru National Institute of Technology, Allahabad(India)
3. Introduction
• Research Area: Design of lattice structure for use in segmental
bone defect as an orthopaedic implant
• Limitations in use of Natural bone scaffold has increased the use
of Synthetic bone scaffold.
• Fabrication of Synthetic bone scaffold by Additive Manufacturing
is a new area of research.
• SLM, EBM techniques are used for fabrication of lattice based
structure.
• Metals available for fabrication are Stainless Steel,
Ti6Al4V,Tanatalum,Co-CrAlloy, Ni-Ti alloy.
4. Designing for
Segmental Bone Defect
4
Segmental bone defect Bone defect filled with metallic
lattice structure
Full view of assembly of bone plate and
lattice structure
Ref: Jan Wieding et.al Finite element analysis on the biomechanical stability of open porous titanium scaffolds for large segmental
bone defects under physiological load conditions “Medical Engineering & Physics 35 (2013) 422–432”
6. Lattice Structure Generation
• Designing
• FEM Analysis- Mechanical ,Biological
• .Stl file format preparation
• Additive Manufacturing -SLM
• SEM, Micro CT scan
• Testing- Mechanical, Biological-In Vivo, In Vitro
6
7. Different Types of scaffold Modeling
7
Ref:S. Gómez et.al. Design and properties of 3D scaffolds for bone tissue engineering Acta Biomaterialia 42 (2016) 341–350
Three main methods to design lattice structure are widely used by researchers
3. By Micro CT scan data
2. Implicit Surface based design
1. CAD based geometric modeling
10. Design Parameters
1. Porosity (P) ,Pore Size
2. Surface Area to Volume ratio (S/Vs)
3. Mechanical Strength
Lattice Structure’s need connected pore space.
Pore connectivity is a very important factor for bone in growth.
16. Porosity Variation
D=4,L=10 D=6,L=10 D=8,L=10
L/D=2.5 L/D=1.67 L/D=1.25
Porosity=29% Porosity=54% Porosity=78%
Surface Area to
Volume Ratio=
766/714=1.072
Surface Area to
Volume Ratio=
690/457=1.51
Surface Area to
Volume Ratio=
509/216=2.36
L=10L=10
L=10 L=10 L=10
D=4 D=6 D=8
17. Porosity Calculation
• Total Volume of cube:
• Volume of scaffold=216
• Porosity=
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3826579/
1000101010)( dddV total
%2.78100
1000
216
1 Porosity
%1001
total
solid
V
V
18. Scaling of Unit Cell
Unit Cell=1
(1x1x1)
L=10,D=8
Area of
pore=50.24
Unit Cell=8
(2x2x2)
L=5,D=4
Area of
pore=12.56
Unit Cell=64
(4x4x4)
L=2.5,D=2
Area of
pore=3.14
Unit Cell=512
(8x8x8)
L=1.25,D=1
Area of
pore=.785
Length of cube for each specimen remains same=10x10x10mm
L/D ratio is same for all above specimens= 10/8=5/4=2.5/2=1.25
L/D ratio governs porosity, which is 78% for L/D=1.25
19. Surface Area/Volume Ratio
Unit Cell l/d ratio=1.25 No. of unit cell in same
volume
(10x10x10)=1000 (mm 3)
Pore Area(mm2),
Pore Size
Surface Area (mm2)
/Volume (mm 3)
1. (10/8)=1.25 1 50.24,
8000micron
509/216=2.36
2. (5/4)=1.25 8 12.56,
4000micron
720/216=3.33
3. (2.5/2)=1.25 64 3.14,
2000micron
1142/216=5.28
4. (1.25/1)=1.25 512 .785,
1000micron
1985/216=9.18
5. (.625/.5)=1.25 4096 .196,
500micron
(Min by SLM)
3710/216=17.1
27. Future Work
Scaffold –Bone growth Model Graded scaffold Model
Development of Scaffold –Bone growth Model
Graded scaffold Modeling
Additive Manufacturing of lattice structures
Mechanical and biological testing
Real life implantation
28. References
1. X. Wang, S. Xu, S. Zhou, W. Xu, M. Leary, P. Choong, M. Qian, M. Brandt and Y. M. Xie,
"Topological design and additive manufacturing of porous metal for bone scaffolds and
orthopedics implants: A review," Biomaterials, vol. 83, pp. 127-141, 2016.
2. J. Parthasarathy, B. Starly and S. Raman, "A design for the additive manufacture of functionally
graded porous structures with tailored mechanical properties for biomedical applications,"
Journal of Manufacturing Processes, vol. 13, pp. 160-170, 2011.
3. Q. Chen and G.A. Thouas, "Metallic implant biomaterials," Materials Science and Engineering
R, vol. 87, pp. 1-57, 2015.
4. J. Wieding, R. Souffrant, W. Mittelmeier and R. Bader, "Finite element analysis on the
biomechanical stability of open porous titanium scaffolds for large segmental bone defects under
physiological load conditions," Medical Engineering & Physics, vol. 35, pp. 422-432, 2013.
5. G. Ryan, A. Pandit and D. P. Apatsidis, "Fabrication methods of porous metals for use in
orthopaedic applications," Biomaterials, vol. 27, pp. 2651-2670, 2006.
6. M. Leary, M. Mazur, J. Elambasseril, M. McMillan, T. Chirent, Y. Sun, M. Qian, M. Easton and
M. Brandt, “ Selective laser melting (SLM) of AlSi12Mg lattice structures," Materials and
Design, vol. 98, pp. 344–357, 2016.
7. L. E. Murr, E. Martinez, K. N. Amato, S. M. Gaytan, J. Hernandez, D. A. Ramirez, P. W. Shindo,
F. Medina and R. B. Wicker, "Fabrication of Metal and Alloy Components by Additive
Manufacturing: Examples of 3D Materials Science," Journal of Materials Research and
Technology” vol. 1, pp. 42-54, 2012. 28