Biomechanics

synonyms:

Stress

• stress = force (in newtons) / area (in meter²) = N/m².
• 1N/m2 = pascal (Pa)

Strain (Normal)

• The ratio of elongation to unit lenth.
• Stain = change in length / unit length.
• Stain is a ration and has no units. Can be presented as a percentage or as microstrain.
• Can be positive (tensile) or negative (compressive)

Shear Strain

• Change in angle between tow adjacent faces of an object that formerly were perpendicular to one another.
• Expressed in radians (360° = 2pie radians)

Modulus of Elasticity

• Modulus of Elasticty = ratio of stress / strain of a material = E.
• Modulus of elasticity = the slope a stress-verses-strain graph.
• Depends on the material being tested, not on the shape of the structure.

Stiffness

• Stiffness = the slope of the linear postion of a force versus displacment graph (N/mm).
• Depends on the geometry of the stucture and modulus of elasticity.

Strength

• Strength = maximum load a structure can withstand without causing material failure.