PSI - Issue 18

Christoph Bleicher et al. / Procedia Structural Integrity 18 (2019) 46–62 Author name / Structural Integrity Procedia 00 (2019) 000–000

57

12

Fig. 16. Stress-strain behaviourof different the Dross-affected specimens

Fig. 17. Specimen with the cut off test volume

Fig. 18 shows the determined virtual Young’s modulus plotted against the density for each specific specimen. It can be stated that a good regression between both values exists, as was also the case for the shrinkages in Bleicher (2016). The relationship between both values for Dross can now be used for an improved lifetime assessment, based on a measured density on the Dross-affected component. Therefore, if the local density of the component can be assessed by means of non-destructive testing, the designer is able to remodel the component with the local and specific stiffness for a more precise recalculation. This enables a decision as to whether or not the Dross-affected component can be used or needs to be rejected. Nevertheless, it is necessary to combine the determined density and stiffness with fatigue to enable a lifetime assessment based on local fatigue reduction factors or S-N curves for certain Dross classifications. Additionally, it is interesting to take a closer look at the scatter of the fatigue results. For both purposes, the determined results for the virtual Young’s modulus and the density of the Dross are used as classification parameter. Initially, it is of special interest that all specimens that did only reach one-half, one or two cycles to rupture also show the lowest values for the virtual Young’s modulus. For all such specimens, a maximum stiffness of 50 GPa could be determined. For densities, corresponding to a maximum virtual Young’s modulus of 50 GPa determined on the investigated cast component with NDT, a crack will initially take place in the component. Such cases need to be assessed by fracture mechanics. All other specimens in this investigation reached at least several 100 cycles to rupture on strain amplitudes of around 0.12 to 0.20 %.

Fig. 18. Correlation between density and stiffness