Mechanical: Machine Design and Materials PE

Remember that axial stress is positive for tension and negative for compression. Always check if the cross-sectional area is given or needs to be calculated from diameter/dimensions. Watch units carefully - stress problems often mix kips with inches or kN with mm.

L10 life represents 90% reliability (10% of bearings fail by this point). Always verify units match between C and P. For exam problems, you may need to calculate equivalent load P from radial and axial components using bearing-specific factors.

This is the Eytelwein (belt friction) equation. Remember wrap angle must be in radians. Larger wrap angles and higher friction coefficients allow greater tension ratios before slipping. Often appears with power transmission problems where you need to check if belt will slip under load.

This is THE fundamental bending equation. Know that y is measured from the neutral axis (centroid), maximum stress occurs at extreme fibers (y = c), and the equation assumes linear elastic behavior. Watch for section modulus S = I/c shortcuts.

CRITICAL: Torque coefficient definitions vary. Some sources use K where T = K×F_i (K ≈ 0.2), others use K_t where F_i = K_t×T (K_t ≈ 5). Always check the problem statement for the relationship direction. Standard lubricated bolts: K ≈ 0.2, so F_i ≈ T/0.2 = 5T.