Biomechanics: Foundational Concepts

Flashcards reviewing foundational concepts of biomechanics, including stress, strain, elasticity, and material properties.

What is the effect of forces on fluids?

Forces produce pressure, and this stress deforms the fluid. Fluids cannot maintain a static deformation, so they deform through flow.

What is the effect of forces on solids?

Forces produce stresses that deform the solid, which can be characterized by the strain.

What is Hooke's Law?

F = -ku, where F is the applied force, u is the displacement, and k is the spring constant.

How do multiple springs behave in parallel?

k = k1 + k2

How do multiple springs behave in series?

1/k = 1/k1 + 1/k2

What is Stress?

Stress is the force per unit applied area.

What is Strain?

Strain is the fractional extension.

What is the Young's Modulus?

The slope of the stress/strain curve in the linear region.

What happens at the Yield Point?

The elastic material starts to become inelastic, behaving more like a plastic and not returning to its relaxed length.

What is Proof Stress?

The amount of stress a material can undergo before it demonstrates a small amount of plastic deformation.

What is Poisson's Ratio?

The ratio of the transverse (compressive) strain to the axial (tensile) strain.

What is Hysteresis?

The load extension curve returns to its relaxed state by a route that is different from that which created the deformation, indicating energy losses.

Define Strength

The (limiting) stress a body can withstand without failure.

Define Stiffness

The ability of a body to resist changes in shape when subjected to applied forces (related to Young's modulus).

Define Young's Modulus

Proportionality constant that relates stress to strain (E = stress/strain).

What is the Bulk Modulus (K)?

K = P/(ΔV/V), where P is pressure and ΔV/V is the fractional change in volume under compression.

What is Homogeneity?

A homogeneous material is the same at all points in space.

What is Isotropy?

An isotropic material has the same properties in all directions.

What is Engineering Strain?

The fractional change in length as a fraction of the original relaxed length.

What is Logarithmic Strain?

The integral of the incremental strain.