Zum Festigkeitsverhalten von mehrachsig stochastisch beanspruchtem Gußeisen mit Kugelgraphit und Temperguß.

In this work a method for the fatigue life estimation of components from materials which fail with only little deformation under multiaxial stochastic loading with different grades of correlation was determined and verified by tests. Two different materials of nodular iron (GGG40 and GGG60) as well as malleable cast iron (GTS45) were available. The multiaxial stochastic loading resulted from the superposition of tensile and torsional loading. Two extreme cases for the grade of correlation of both loads, the linear correlated and the uncorrelated loading were taken into account. For the failure in each case nominal strains in the most highly loaded cross-section are decisive. The characteristic quantities for the fatigue life estimation under linear correlated loading are based on the nominal strain hypothesis, for the uncorrelated loading the method of reference strain was introduced. The reference strain is not only a value related to the material behaviour, but takes also account for the statistical interaction of the uncorrelated loads based on the independance of casual values. Test and calculations correspondingly show for the uncorrelated loaded components a higher fatigue life by about factor of 2 compared to the results with linear correlated samples if the same particular characteristic values of loading (peak values of spectra) boundary conditions (shape of spectra and stress ratio) are choosen.