8. Compared to brittle fracture, ductile fracture: a) Occurs more rapidly at lower stress levels b) Occurs without yielding of the material c) Occurs after the material reaches its yield stress d) Has no visible deformation before failure 9. Why is ductile fracture considered better than brittle fracture? a) Because it occurs at lower stress levels b) Because it gives warnings before final failure c) Because it happens suddenly, preventing further damage d) Because it does not require yielding 10. What is the first step in the ductile fracture process? a) Formation of microvoids b) Crack propagation by shear deformation c) Necking d) Fracture 11. What occurs after the microvoids form during the ductile fracture process? a) Crack propagation by shear deformation b) Necking c) Coalescence of microvoids to form a crack d) Fracture 12. What is fatigue in engineering materials? a) Sudden failure due to high impact stress b) Gradual failure due to cyclic tensile stress c) Instant failure due to thermal expansion d) Deformation due to compressive loading 13. What happens to the microcrack during fatigue failure? a) It remains static b) It grows progressively through the material c) It heals over time d) It turns into necking 14. Which of the following is NOT a common source of cyclic stress? a) Vibrations in the system b) Stress cycling c) Thermal cycling d) Compressive stress at static load