Topic: Machine Design
The diagram below is showing the various criteria of fatigue failure. Which option is the correct representation of these criteria? (Subscripts e, y and u represent endurance, yield and ultimate respectively.)
- A. 1 - Soderberg line, 2 - Goodman line, 3 - Gerber line
- B. 1 - Goodman line, 2 - Soderberg line, 3 - Gerber line
- C. 1 - Soderberg line, 2 - Gerber line, 3 - Goodman line
- D. 1 - Gerber line, 2 - Soderberg line, 3 - Goodman line
Answer: A. 1 - Soderberg line, 2 - Goodman line, 3 - Gerber line
Explanation: The Soderberg line (1) is the most conservative, connecting the endurance limit (Se) to the yield strength (Sy). The Goodman line (2) connects the endurance limit (Se) to the ultimate tensile strength (Su). The Gerber line (3) is a parabola connecting Se to Su.