- See:
-
Characteristics of Metals and Implants:
-
Elastic Strain
-
Metal Fatigue
-
Plates
-
Polyethylene
-
Screws
-
Strain
-
Stress
-
Ultimate Tensile Strength:
-
Visoelastic Materials
-
Yield Strength:
-
Young Modulus
- Biomechanical Definitions:
- isotropic materials: possess the same properties in all directions;
- anisotropic materials: have mechanical properties that vary w/ orientation of the loading;
- brittle materials:
- have little ability to exhibit plastic deformation, and therefore, exhibits a linear stress
-
strain curve up to the point of failure;
- ductile materials:
- undergo a large amount of plastic deformation prior to failure;
- measure of a metal's ability to withstand considerable plastic deformation w/o breaking;
- rigidity:
- bending rigidity for a rectangular plate: base * ht(exp 3) / 12
- torsional rigidity for a cylindrical rod: c * pi * r (exp 4) / l
- endurance limit (fatigue limit)
- the maximum stress under which a material will not fail when subjected to indefinite cyclic loading;
- fatigue strength:
- refers to the maximum cyclic load (10 million cycles) that a standard sized metal can absorb before fracturing;
- toughness:
- ability of a metal to absorb energy by bending without breakage (the strain energy in the metal
at the point of
ultimate stress;
- it is the area under the stress
strain curve;
- energy a structure absorbs as it deformed by applied force is equal to the work done by that force;
- creep:
- describes the amount of deformation that a material undergoes with time as it is subjected a constant load;
- when subjected to a constant load the deformation will reach a state of equilibrium;
- moment of inertia:
- refers to resistance to rotation;
- Stress Strain Curve:
- derived by axially loading a body and plotting
stress vs
strain;
- proportional limit (
yield point) is transition from elastic to plastic range; usually 0.2% strain in most metals;
-
ultimate tensile strength;
- break point:
- if
strain increases, a point will come when the material fails;
- plastic strain:
- if greater
stress is applied to the material, its power to
recover may be exceeded, and it remains permanently deformed;
- plastic deformation
- change in length after removing load (before breaking point) in plastic range;
|
1 Al2O3(ceramic)
|
2
Co-Cr-Mo (Alloy)
|
3
Stainless steel
S |
4
Titanium
t
|
5 Cortical Bone
r
|
6 Matrix polymers
e
|
7 PMMA
s
|
8
Polyethylene
s
|
9 Cancellous bone
|
10 Tendon/ligament
|
11 Cartilage
|
|__________________________________________
Strain
- Links:
Muller Institute for Biomechanics
Berkely Orthopaedic Biomechanics
Biomechanics Magazine
Department of Orthopaedic Research and Biomechanics - University of Ulm
Biomechanics World Wide
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