“…In the process of HA and IA wear the stiffness coefficient of the stressed‐strained state of the surface of the materials, II, was determined using the Tsvetkov's technique (Pogodaev et al , 1997) according to which Π=( σ x + σ y + σ z )/ σ i =1.651 n (3,450/HV), where σ x , σ y , and σ z are the principal stresses acting along the axes X , Y , and Z , respectively; σ i is the stress intensity, and HV is the Vickers hardness measured in megapascals.…”