Biomechanics Exam One Flashcards
Stress (σ)
Force applied to an area
Measured in N/m^2 or pascals
σ = F/A
Strain (ε)
Deformation caused by applied stress
Tension
the act or action of stretching
Compression
the state of being compressed
Shear
unaligned forces acting on one part of a body in a specific direction, and another part of the body in the opposite direction.
Torsion
the twisting of an object due to an applied torque.
Bending
to turn or force from straight or even to curved or angular.
Stress/Strain Curve
Slope is Young’s Modulus/Stiffness
Elastic region which can go back to how the object was once stress is removed
After elastic region is yield point before plastic region
Plastic region is permanent deformation
After the plastic region the specimen fails
a type of test where a load is continuously applied to a test specimen until it fractures
Young’s modulus
Stiffness for material
Y=σ/ε=F/A=L/ ∆L
Residual Strain
Difference between original length and length resulting from stress into the plastic region
Stiffness
Resistance to deformation
Strength
Resistance to failure
expressed as force required to produce:
a permanent deformation: yield strength
a fracture: fracture strength
Metal vs glass
Metal: ductile-large plastic region
Glass: brittle-fracture and yield at the same time
Elastic material
Linear between stress and strain
Mechanical energy is fully recovered (provided it stays in elastic region)
Viscoelastic
Same definitions for elastic materials apply
Exhibits non-linear stress strain characteristics
Ex. Bone. Has these characteristics because of the liquid in bone
Hysteris
Loss of energy into the material and time dependent delay
Stress relaxation
Time dependent decrease in load or force or stress required to maintain a constant deformation
The deformation is temporary until the stress is removed
Creep
Time dependent increase in deformation while under constant load/force/stress
Bone tissue
connective tissue
short bones
square, triangular shape
Flat bones
flat
scapula, skull
irregular bones
irregular in shape
Long bones
has one dimension longer than another dimension