What surface roughness parameter is commonly expressed as Ra, and what does a smoother surface imply for load-bearing components?

What surface roughness parameter is commonly expressed as Ra, and what does a smoother surface imply for load-bearing components?

• A. Ra is average roughness; smoother surfaces generally improve fatigue life and reduce friction
• B. Ra is maximum roughness
• C. Ra is roughness measured at micro scale
• D. Ra stands for roughness index

Answer: (A)