PSI - Issue 28

15

Stepan Major et al. / Procedia Structural Integrity 28 (2020) 561–576 Author name / Structural Integrity Procedia 00 (2019) 000–000

575

Fig. 12. Use of deviation angle β to map fracture surface, we can see directional vectors in the image: (a) pure bending; pure-torsion.

5. Conclusion Most convincing results of the analysis can be summarized into the following points:  In this article was presented new method for fracture surface description. This method is based on normal vectors of elementary flats, which are covering fracture surface. Proposed method is suitable for description of fracture surface roughness and measuring the angle α (deviation angel between normal vector of elementary flat and sample axis) can essentially replace classical roughness criteria.  The great influence of torsion loading component on the fatigue surface morphology has been confirmed. The critical value of the loading ratio is estimated as L R = 0.5. Increase of surface roughness on the macroscopic level as well as of the intensity of frictional effects is very evident after exceeding L R = 0.5, i.e. torsion prevails.  Measuring the angle α and its variance Δ α can be used to analyze fish-eye cracks. The great increase of Δ α scattering of indicates a change in the mechanism of crack growth.  Measured deviation angel β (which is the angle between normal vector of elementary flat and primary crack growth direction) can be used for mapping fracture surface. Acknowledgements Experimental work was financially supported by project MSM 0021630518 and its publication of this article was supported by project SV 2125/ 1440/ 1210. References Balankin, A. S., 14 May 1997. "Physics of fracture and mechanics of self-affine cracks". Engineering Fracture Mechanics. 57 (2–3), 135–203. Dong, W.P., Sullivan, P.J., Stout, K.J., 1994. Comprehensive study of parameters for characterising three- dimensional surface topography: III: Parameters for characterising amplitude and some functional properties, Wear, Volume 178, Issues 1–2, 29-43 Gadelmawlaa, E.S., Kourab,M.M., Maksoud, T.M.A., Elewaa, I.M., Soliman, H.H., 2002. Roughness parameters, Journal of Materials Processing Technology, 123, 133-145. Kobayashi, T., Shockey, D.A.,2003, The relationship between fracture surface roughness and fatigue load parameters, International Journal of Fatigue 23, 135-142. Laushmann, H., Nedbal, I., 2002. Auto-shape analysis of image textures in fractography, Image Analysis & Stereology, 21, 139-144. Antunes, F.V., Ferreira, J.A.M., Ramalho, A.L., 2000. Identification of fatigue crack propagation modes by means of roughness measurements, Int J Fatigue 22 (9) 781-788.