Practical fatigue analysis of hydraulic cylinders and some design recommendations

In this paper, a numerical algorithm is presented which makes it possible to adopt the different loading schemes of specific structure at hand, for instance hydraulic cylinders, to specific Wöhler curves characterizing fatigue resistance of the given material. The model used in this paper is based on particular application of the constitutive model described in reference [S. Oller, O. Salomon, E. Onate, A continuum mechanics model for mechanical fatigue analysis, Comput Mater Science 2005;32(2):175–95]. Hydraulic cylinders investigated under E.C. project “PROHIPP” are analyzed and some solution of the crack problem in oil port area is proposed. Calculations have to be done for cylinders under loads, which differ from the experimental data provided in Wöhler curve. Oil penetration in oil port connection zone can be eliminated after some design modifications. As it is written at the end of EN 13445 rules description (point 18I) [European Norm EN 13445. Unifired pressure vessels, chapter 18: Detailed assessment of fatigue life, http://www.unm.fr/en/general/en13445/default.htm], the ‘marriage’ of stress analysis from finite element analysis and fatigue data is still one of the deficiencies in the current EN 13445. We believe that this paper partially reduces this deficiency.