The area where asperities on two surfaces actually touch. When the asperities deform plastically it equals the load divided by the hardness, and it is far smaller than the apparent contact area.
Japanese name: 真実接触面積
Real area of contact appears in 4 practice questions across 1 topic, including Surface treatment and tribology.
Answer: C. About 0.05%
Ar = W/H = 1.0×10³/(2.0×10⁹) = 5.0×10⁻⁷ m² = 0.50 mm². The apparent area is 10 cm² = 1000 mm², so the fraction is 0.50/1000 = 5×10⁻⁴, about 0.05%. Even on a surface that looks flat, only a tiny part at the asperity tips actually touches, and those spots carry a high pressure equal to the hardness. About 0.5% is the value obtained by converting 1 cm² as 10 mm² instead of 100 mm², and about 50% is the value obtained by treating the hardness in MPa instead of GPa. The high local pressure at the real contact spots, together with the high temperature generated by sliding, is the starting point for adhesion and wear.
Because the asperities deform plastically to support the load, the real area of contact equals the load divided by the hardness and is proportional to the load regardless of the apparent area.
Which statement correctly describes the empirical law of fr…The friction force is the product F = sAr of the real area of contact Ar = W/H and the junction shear strength s, so F/W = s/H, giving a friction coefficient that depends neither on the load nor on the apparent area.
In the adhesion theory (the view of Bowden and Tabor), the …The Archard equation assumes that a number of contact spots proportional to the real area of contact W/H produce wear debris a number of times proportional to the sliding distance, so the wear volume is proportional to the load and the sliding distance and inversely proportional to the hardness.
In a pin-on-disk test, a pin of hardness H = 2.0 GPa is loa…Archard wear equation Abrasive wear Adhesive wear Carburizing Electroless nickel plating Nitriding Stribeck curve