METHOD FOR DETERMINATION OF RESIDUAL STRAINS

摘要

Method for determination of residual strains relates to mechanical testing of coatings or materials and can be used for purposes of investigation at evaluation of mechanical properties of articles and formation of new materials and in industrial production for control of quality of coatings. The method includes pressing in of pyramidal indenter to cross-section of coating or layer of metal till obtaining imprint of hardness at orientation of its diagonals in normal directions with respect to effect of residual strains, at that one registers force of pressing in, measures after unloading geometrical parameters of the imprint, with account of those one determines residual stresses. The tests are carried out with use of pyramidal Knupp indenter with basis as rhomb. Pressing in of indenter is performed in two neighboring area of coating of layer of material with force of pressing in that exceeds critical value. One obtains two imprints of hardness with normal to each other orientation of long diagonals and with account of the measurements carried out one determines value of hardness (NK) by imprints in which ling diagonal is directed in parallel (NK) and normally (NK) with respect to effect of residual strains. Value of residual strainsis determined from difference between values of hardness (NK) and (NK) with use of norming graph that is being plotted with independent methods in coordinates (NK- НК) -. The method provides increase of accuracy of determination of residual strains at mechanical testing of coatings or materials and decrease of labor consumption of such determination.