| Abstract: | Rigidity is one of the main factors decisive for the quality of machine tools, measuring instruments and many other devices. One of the principal deformation components of a machine element is contact deformation due to surface roughness. The contact rigidity can be controlled by selecting appropriate working methods and parameters, influencing directly the surface roughness characteristics. It is for this reason that many theoretical and experimental works have been devoted to the problem mentioned. As a result of the first load being applied the surface roughness undergoes elastic-plastic deformation, which has not yet been described by any consistent theory. During unloading and subsequent loading processes the deformed asperities remain elastic (if there are no tangential displacements). However, as a result of no data being available as regards the stereometric features (3-D) of roughness and their changes due to plastic deformation, the theoretical results are charged with considerable errors. In engineering problems the value of a contact deformation may be computed making use of statistical relations based on roughness models of various degrees of complication. These relations are established on the basis of the results of some tests of the surfaces of elements machined by the same methods and made of the same materials as the elements to be analysed. These methods enable us to evaluate contact deformations with an accuracy which is much better than that of the theoretical methods. Another method for ensuring the required rigidity of manufactured objects is by direct measurement of contact deformation in the course of the manufacturing process, for which a special apparatus is required. The devices which have been designed for the measurement of contact deformations of a surface enable such measurement by using a check surface of high hardness and low roughness as compared with those of the parts considered. |
