| Popis: |
Present gaps in our knowledge regarding the plastic behavior of solid lubricants and in the surface layers of contact spots during dry sliding include the following. 1. (i) By which mechanisms does the deformation occur? 2. (ii) Does there exist a limiting plastic strain beyond which further shearing is impossible so as to result in lubricant breakdown, fracture or delamination? 3. (iii) Can solid lubricants be permanently retained during sliding? 4. (iv) What is the theoretical value of the friction coefficient through solid lubrication, and how does it depend on the hardness of the lubricated material? 5. (v) On the basis of answers to (i)–(iv), can unlubricated sliding conditions and/or solid lubrication be optimized? Since the requisite information can be obtained through shearing experiments under superimposed high normal pressures, a study of the stress-strain behavior of ductile metals in a Bridgman anvil type of apparatus has been initiated. For the first time ever, the sample thickness has been monitored and thus shear stress vs. strain curves have been obtained in such an apparatus. |
