Stanovení nejistot měření mechanických vlastností a součinitelů plastické anizotropie materiálu u zkoušek tahem

摘要

Paper deals with determination of measurement uncertainties of mechanical properties andplastic anisotropy ratios of material at the tensile tests at usage of either three or five test specimens inorientations 0º, 45º and 90º towards sheet-metal rolling direction. Standard for tensile testsČSN EN ISO 6892-1 contains determining of uncertainties partly for input dimensions of testspecimens, partly for testing device, no for values of measured mechanical properties. The standardfor determination of plastic anisotropy ratios ČSN ISO 10113 does not include the determination ofmeasurent uncertainties, hence the standard does not solve achieve results accuracy. In thiscontribution the selective averages, selective standard deviations and combined measurementuncertainties of directional and medium values of mechanical properties and plastic anisotropy ratiosof steel strip DD11 (11 320) are calculated using statistical methods. For calculations the softwareMS Excel was used. Based on the values of weighted average of plastic strain ratio of tested steelstrip and with the use of sheet-metal classification concept according to Shawki, the suitability oftested steel for drawing operations at which predominate pressure-pull mechanical diagrams of stresswas evaluated.