Question

(A) Describe how fatigue damage could happen (although K I is less than K I C ). Draw sketches if needed. (B) If we maintain a constant stress on a material and never unload it, will fatigue damage occur? Why?

Answer 1

A)

When a element or structure comes under repeatedly or fluctuating stress after some time the material started showing plastic hinges which is the sign of failure of the materials this phenomenon is called fatigue damage of the element or structure.

We can also say that when any material have the stress for long time with fluctuations it goes under deformation and at a point it shows hinges or cracks which is the failure point of material and called as fatigue damage.

(B)

If we maintain a constant stress on a material and never unload it there will be No fatigue damage because fatigue is due repeated stress by which in Microscopic cracks forms and propagate overtime until a critical crack size is reached but in case of constant stress no such phenomenon of generating of crackes are occurs.

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