This document discusses the mechanical properties of bone. It begins by outlining the learning objectives, which are to conduct stress analysis on bone samples, identify how bone's anisotropic material properties arise, and analyze how changes in bone composition affect stress and strain. It then explains that mechanical testing of materials involves applying and measuring forces and deformations. The document discusses how bone is a composite material made of collagen and hydroxyapatite mineral, giving it anisotropic properties, and strongest in compression. It attributes bone's anisotropic properties to its cortical and cancellous bone structures. Finally, it notes bone is a dynamic material that repairs itself and changes with aging and weight-bearing levels.

1. Mechanical Properties of
Bone
Human knowledge and human power meet
in one; for where the cause is not known
the effect cannot be produced.
~ Sir Francis
Bacon
BIOE 3200 - Fall 2014
Nova special, “Making Stuff Stronger”:
https://www.youtube.com/watch?v=KE-
Y45WjiP0&list=PL9OMJke2jE_CuZgiOUJ0frfw3TRLKQByw&index=1

2. Learning Objectives
 Conduct stress analysis on bone
sample
◦ Identify the source of anisotropic material
properties
◦ Analyze how changes in bone
composition affect stress and strain within
bone
BIOE 3200 - Fall 2014

3. How is mechanical testing
conducted?
 Apply force,
measure
deformation
- OR -
 Pull (or push) a
known distance,
measure force
 Example of tensile
testing:
◦ https://www.youtube.co
m/watch?v=67fSwIjYJ- BIOE 3200 - Fall 2014
From http://web.ecs.baylor.edu/faculty/Skurla/research.htm

4. Bone
BIOE 3200 - Fall 2014

5. BIOE 3200 - Fall 2014

6. BIOE 3200 - Fall 2014

7. Bone is anisotropic: material
properties are different in different
directions.
 Bone is a composite of mainly
collagen and minerals (hydroxyapatite,
or calcium)
◦ Collagen has a low E, high tensile
strength, low compressive strength
◦ Hydroxyapatite is stiff, brittle, high
compressive strength
 Anisotropic material that can resist
different types of forces
 Strongest in compression, weakest in
shear, intermediate in tension
BIOE 3200 - Fall 2014

8. What gives bone its anisotropic
properties?
 Cortical bone
◦ E affected mainly by
mineral content
◦ Resists torque
(concentric
lamellae)
 Cancellous bone
◦ 25% as dense as
cortical
◦ 10% as stiff as
cortical
◦ 500% as ductile as
cortical
◦ Resists BIOE 3200 - Fall 2014

9. Bone is a dynamic material
 Self-repairs (osteoclasts, osteoblasts)
 Changes with aging: becomes stiffer
and less ductile
 Changes with lack of weight-bearing:
becomes weaker
BIOE 3200 - Fall 2014