DISCIPLINES INVOLED ON INVESTIGATION OF MATERIAL'S TRIBOLOGY Prepared By: Masoud Sheykhi ,Sarcheshmeh copper complex ,Kerman , Iran. It is customary to introduce the subject by reference to idealized bearings of the types shown in theImage:Conformal conditions.pdf , Image:Counterformal conditions.pdf.pdf and Image:KEY.pdf. The load W when associated with frictional force μW produces the resultant applied force which is tangential to the friction circle. W may be constant in magnitude and in direction or it may vary in magnitude and also in direction relative to the system as a whole. The varying load encountered in engines is especially important. Similarly ,velocity may vary and in the general case both surfaces may be considered as moving. In the diagram , velocities U1 and U2 are measur