1.2 Nanoscale Actors and Their Properties

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Figure 1.20: To more accurately describe non-ideal,

time-dependent mechanical strength, modulus is

combined with viscosity.

Figure 1.21: With the ideal, purely elastic response

all effects are immediate. To describe real be-

havior, the time dependence of the effect has to

be incorporated. This is done by adding viscous

flow behavior to the elastic response. The time-

dependent application of stress is called creep, the

time-dependent removal of stress is called recov-

ery. A large stress past the ideal region also leads to

permanent deformation.

And here is where toughness comes in: toughness is the force/volume needed to break

the material (Figure 1.22). Basically, you measure the real stress/strain curve until the

material breaks and then measure the area under the complete stress/strain curve;

that is toughness. Force is the stress, strength is the modulus in the ideal region of a