Question

The most serious manufacturing defect from fracture toughness point of view is

• A. Crack
• B. Pore
• C. Surface roughness
• D. Spherical inclusion

Hint:

Cracks drastically reduce fracture toughness due to high stress concentration at the crack tip. Always inspect and eliminate cracks during quality control.

Answer 1

The Correct Option is A

Cracks are considered the most severe manufacturing defects from the standpoint of fracture toughness because: - They act as stress concentrators. - The stress intensity factor \( K \) near a crack tip increases dramatically. - Even under relatively low applied loads, a crack can propagate rapidly, leading to sudden failure (brittle fracture). - Unlike pores or inclusions, cracks provide a sharp discontinuity that severely lowers the material's ability to withstand tensile stress. Therefore, the presence of a crack in a component is far more critical than other defects like pores, surface roughness, or inclusions.