Consider the following statements: For a component made of ductile material, the failure criterion will be 1. endurance limit, if the external force is fluctuating 2. fatigue, if the external force is fluctuating 3. yield stress, if the external force is static Which of the above statements are correct?

Option 4 : 1, 2 and 3

Concept:

• For ductile material under static load, material start yielding at yield point beyond which material gets deformed permanently and finally fail by cup and cone fracture at UTS.
• The allowable stress of the material is also governed by yield stress and in industries too beyond this point material is termed as failed.
• If an external force is fluctuating then material get fail at stress which is considerably lower than the normal stress of static load. This behavior is termed as fatigue.
• There are two terminologies used in fatigue fractures. These are fatigue strength and fatigue life. The graph in between these tells the fatigue strength and finally define the endurance limit of a particular material.
• Under fatigue failure ductile material will fail as like as brittle material.
• The failure of ductile material under fluctuating load is called fatigue.
• Failure of ductile material under static load occurs at yield stress.
• The endurance limit is the maximum stress amplitude of a component that can withstand. It is the strength of the material.