Force, Stress, Strain

Actuators for the promotion of:

Artificial Muscles and Tendons

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What are some of the physics we are looking at for artifial tendons and muscles?

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Hooke's Law: materials deform in linear proportion to the load (force) applied to it. F~KS where K is a constant and S is the amount deformed (Newman 2003).

Stress= force/area this looks like pressure, which also is a type of stress. There are two types of stress: 1)normal-which is perpendicular to the material 2)shear stress-which is parallel to the material.

The response of a material to a stress is called a strain.

Strain= change in length/original length.

There are two types of normal stress: 1)tensile 2)compressure

All materials have a stress/strain diagram.
Elastic moduli: 1)Young's modulus Y for tensile stress:

Y= stress/strain= (F/A)/(delta L/L not) this is related to K-- F= (YA/L not) times delta L where (YA/L not) is K which is Hookes Constant. This entire equation is Hooke's Law

2)shear modulus:

shear stress/shear strain

3)bulk modulus: volumetric stress/volumetric strain


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and Brian Epler email

Physics 103 Fall 2003 Dr. David Newman

last updated on 24-Nov-2003