PSI - Issue 18

Matus Margetin et al. / Procedia Structural Integrity 18 (2019) 663–670

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Matus Margetin at al./ Structural Integrity Procedia 00 (2019) 000–000

5. Conclusion Based on the findings discussed in previous chapters and results shown in figure 1-6 the following conclusion can be postulated:  The discussed multiaxial criteria (McDiarmid, Matake) which defined critical plane based on the maximal shear stress amplitude acting in material overestimate damage in noncritical planes. As this effect is caused by normal and shear stress distribution as a function of plane orientation, it is probable, that the same problem will concerns other criteria with similar critical plane definition.  The criteria, that define critical plane as the plane with maximal damage (in our case Findley), overcome this problem from definition, however the critical plane orientation is usually inconsistent with observation.  The material properties have significant influence on damage distribution as a function of plane orientation. In case of Findley criterion it influence critical plane orientation, in case of McDiarmid and Matake criterions it strongly influence the maximal damage in noncritical planes.  The problem with damage calculation in noncritical plane has huge influence on fatigue damage calculation of material loaded with nonproportional variable amplitude loading. In this case the damage is accumulated in each plane and the lifetime of material is then defined by plane with highest accumulated damage.  As can be seen in figure 6 the lifetime of material loaded with simple nonproportional loading process is determined by damage caused in noncritical plane of individual segments of loading process. Acknowledgements This work was supported by the Slovak Research and Development Agency under the contract No. APVV-17 0666. The presented contribution has been prepared under project LO1502 “Development of the Regional Technological Institute” under the auspices of the National Sustainability Programme I of the Ministry of Education of the Czech Republic aimed to support research, experimental development and innovation. Chmelko, V., Šulko, M., 2015. Long-time loadings monitoring of a structure in real operation. EAN 2015 - 53rd Conference on Experimental Stress Analysis, pp. 145-148. Kepka, M., Kepka, M., Jr., 2018. Parametric calculations of fatigue life of critical part of trolleybus rear axle. Procedia Engineering, 213, pp. 227 238. DOI: 10.1016/j.proeng.2018.02.024 Findley, W.N., 1957. Fatigue of metals under combinations of stresses, Trans ASME 79 1337-1338 Polak, J., Man, J., Vystavel, T., Petranec, M., 2009. The shape of extrusions and intrusions and initiation of stage I fatigue cracks, Mater Sci Eng A, 517, 204-211. DOI: 10.1016/j.msea.2009.03.070 McDiarmid, D.L., 1991. A general criterion for high cycle multiaxial fatigue failure, Fatigue Fract Eng M 14, 4, 429-453 Matake, T., 1977. An explanation on fatigue limit under combined stress, Bulletin of the JSME, 20, 141, 257-263 Socie, D.F., Marquis, G.B., 2000. Multiaxial Fatigue, Society of Automotive Engineers, Warrwndale, PA, ISBN 0-7680-0453-5 References