1. Design and Fabrication of an
Articulated 3-Point Bending Fixture
for Use in Assessing the Strength of
Heel Fracture Repair
Nathan Janiczek
Vincent Melillo
Justin Smialek
Sponsor: Dr. Mark Miller

3. Calcaneal Fracture

4. Calcaneal Repair and Testing

5. Irregular Shape

6. Functional Requirements
• Minimum load capacity of 700 lbf
with Minimal Deflection.
• 10o of Articulation about the base.
• 4 inches of adjustment for the
vertical support.
• 8 inches of adjustment for the
horizontal support.
• A reusable mold housing for equal
load distribution on the superior
face of the calcaneus.

7. Preliminary Research

8. Preliminary Designs

9. Preliminary Designs

10. Verification
Axial Load Stress
Analysis
𝜎 =
𝑃
𝐴
𝑛 =
𝑆 𝑦
𝐾𝑡 𝜎

11. Verification
Bearing Stress
Analysis
𝜎 𝐵 =
𝑃
𝐴 𝑏
𝑛 =
𝑆 𝑦,𝑏
𝜎 𝐵

12. Verification
Shear Stress Analysis
𝜏 𝑐 =
4𝑉
3𝐴
𝜏 𝑠 =
3𝑉
2𝐴
𝑛 =
𝑆𝑠𝑦
𝜏

13. Verification
Bending Stress
Analysis
𝜎 =
𝑀𝑐
𝐼
𝑛 =
𝑆 𝑦
𝜎

14. Verification
Deflection Analysis
𝛿 𝑚𝑎𝑥 =
𝑤𝑙4
8𝐸𝐼

15. Obtaining Materials

16. Fabrication

17. Assembly

18. Finished Product

19. Acknowledgements
• Dr. Mark Miller
• Dr. Schmidt
• Andy Holmes
• Jeff Speakman
• SCPI Student Workers
• Heather Manns

20. Questions

22. Appendix (Gantt Chart)

23. Appendix (Bill of Materials)
Part Vendor Total Price
Interstate Machine Vise MSC $196.21
ASTM B221-08 6061-T6 Aluminum Flat Bar Discount Steel $87.58
ASTM B221-08 6061-T6 Aluminum Square Bar Discount Steel $73.31
ASTM A108-07 1018 Cold Rolled Steel Flat Bar Discount Steel $39.82
Fully Threaded Steel T-Slot Nut McMaster Carr $3.39
Black-Oxide Alloy Steel Socket Head Cap Screw McMaster Carr $7.97
Type 316 Stainless Steel Flat Washer McMaster Carr $13.26
Black-Oxide Alloy Steel Socket Head Cap Screw McMaster Carr $14.19
Black-Oxide Alloy Steel Socket Head Cap Screw McMaster Carr $11.10
Medium-Strength Grade 5 Zinc-Plated Steel Cap Screw McMaster Carr $12.32
Type 18-8 Stainless Steel Flat Washer McMaster Carr $3.91
Standard Clevis Pin MSC $1.43
Hair Cotter Pin MSC $7.76
Rod End, Machined, Male Grainger $27.36
Miniature 12L14 Drive Steel Shaft McMaster Carr $17.32
Black-Oxide Alloy Steel Socket Head Cap Screw McMaster Carr $6.88
Grade 5 Steel Hex Nut McMaster Carr $11.22
18-8 Stainless Steel Knurled Head Thumb Screw McMaster Carr $17.40
General Purpose Low-Carbon Steel McMaster Carr $64.31
$616.72

24. Appendix (Linear Bearing Plate)

25. Appendix (Mold Box with Calcaneus)

26. Appendix (Calculations)
Aluminum Base
Bending Stress
Governing Equations:
Parameters Value
Rail Width (b) 96.52 mm
Rail Step Height (h) 12.7 mm
Rail Step Length (L) 57.2 mm
Moment of Inertia (I) 2.06(10-6) m^4
Load (F) 186.8 kN/m
Maximum Moment (M) 127 N-m
Distance to Neutral Axis (c) 6.35 mm
Bending Stress (σ) 98 Mpa
Yield Strength (Sy) 240 Mpa
Safety Factor (n) 2.45
𝜎 =
𝑀𝑐
𝐼
𝑛 =
𝑆 𝑦
𝜎

27. Appendix (Calculations)
Clevis Pin Shear Stress
Governing Equations:
𝜏 =
4𝑉
3𝐴
𝑛 =
𝑆𝑠𝑦
𝜏
Parameter Quantity
Maximum Load (V) 700 lbf
Diameter of the Pin (d) 0.5 in
Area (A) 0.19635 in2
Maximum Shear Stress (𝜏) 4753.43 psi
Yield Strength (Sy) 53700 psi
MSS Yield Strength for
Shear (Ssy) 26850 psi
Factor of Safety (n) 5.65

28. Appendix (Calculations)
Mold Box Bearing Stress
Governing Equations:
𝜎 𝐵 =
𝑃
𝐴 𝑏
𝑛 =
𝑆 𝑦,𝑏
𝜎
Parameter Quantity
Diameter of Pin 0.5 in
Thickness of Support 3.58 in
Bearing Stress Area 1.79 in2
Maximum Possible
Load 700 lbf
Bearing Stress 391.06 psi
Bearing Strength 56000 psi
Factor of Safety 143.2

29. Appendix (Calculations)
Deflection of Vise Step
Governing Equation:
𝛿 𝑚𝑎𝑥 =
𝑤𝑙4
8𝐸𝐼
Parameters Value
Young's Modulus (E) 69 GPa
Rail Width (b) 96.5 mm
Rail Step Height (h) 12.7 mm
Rail Step Length (L) 57.2 mm
Moment of Inertia (I) 2.06(10-6) m4
Distributed Load (w) 186.8 kN/m
Max Deflection (δmax) 0.00005 mm

30. Appendix (Calculations)
Deflection of Base Rail
Governing Equation:
𝛿 𝑚𝑎𝑥 =
𝑤𝑙4
8𝐸𝐼
Parameters Value
Young's Modulus (E) 69 GPa
Rail Width (b) 96.5 mm
Rail Height (h) 12.7 mm
Unsupported Rail
Length (L)
57.15 mm
Moment of Inertia (I) 1.65(10-8) m4
Distributed Load (w) 77.833 kN/m
Max Deflection (δmax) 0.24 mm

31. Appendix (Calculations)
Articulation Insert Stress
Governing Stress Concentration:
Parameters Value
Width (w) 96.5 mm
Height (h) 38.1 mm
Thickness (t) 19.1 mm
Force (F) -4480 N
Parameters Value
d 12.7 mm
w 76.2 mm
h 19.1 mm
t 19.1 mm
Area 1209.7 mm^2
h/w 0.25
d/w 0.1667
Stress Concentration 8
Yield Stress -26.45 MPa
Yield Strength 240 MPa
Factor of Safety 9.1