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Chap 9: Mechanical Properties of Biological Tissues. Elastic Materials. = E . Reversible in the elastic range and generally n ot dependent on time. Most engineering materials w e stay in this elastic region. Nonlinear Elasticity. Hookean Elasticity. “Rubber Band”. Pseudoelasticity.
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Chap 9: Mechanical Properties of Biological Tissues Elastic Materials = E Reversible in the elastic range and generally not dependent on time. Most engineering materials we stay in this elastic region.
Nonlinear Elasticity Hookean Elasticity “Rubber Band”
Pseudoelasticity Hysteresis
Definitions involving Viscoelasticity Stress relaxation – when a body is suddenly strained (deformed) and then the strain is maintained constant, the corresponding stresses induced in the body decrease with time Creep – if the body is suddenly stressed (loaded) and the stress (load) is maintained constant afterward, the body continues to deform with time Hysteresis – cyclic loading gives a situation wherein the loading and unloading processes are somewhat different, pseudoelastic
Models of Viscoelasticity • These models comprise a spring (elastic) with a dashpot (viscous) where • is the Hookean spring constant and is the viscosity. • Spring gives an instantaneous deformation proportional to the load (F), whereas • the dashpot provides a velocity proportional to the current velocity.