5487408519

(a)

Comments

Materials

Stress cycle

Time—►

Strain responses

Strain —►    Strain —►    Strain —►    Stress

Specimen is loaded to a given stress and subseąuently unloaded

Ideał elastic solid: elastic strain only, constant with time

Elastic plus plastic deformation: elastic strain is recovered on removal of stress, plastic strain is permanent

Viscoelastic: some instantaneous elastic strain followed by elastic strain which increases with time under stress and recovers slowly; some viscous (plastic) flow may also occur

Metals (below yield stress), thermoplastics [well below (Tg)], thermosets, ceramics and glasses

Ductile materials above yield stress

Thermoplastics at temperatures around Tg