Biomechanics : Wheeless' Textbook of Orthopaedics

- 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;

- Links:

Muller Institute for Biomechanics

Berkely Orthopaedic Biomechanics

Biomechanics Magazine

Department of Orthopaedic Research and Biomechanics - University of Ulm

Biomechanics World Wide