PHOTOELASTIC ANALYSIS OF CYLINDRICAL ELEMENTS WITH INTERNAL CRACKS UNDER HERTZ CONTACT LOADING

The evaluation of the criticality of internal cracks or defects in contacting elements is a topical point in the design of many mechanical systems. This is due to the complexity of the problem and the difficulty in finding analytical solutions for the problem. In particular this is true if three-dimensional curved cracks and Hertz contact conditions are considered, both for the reasons just underlined and for the fact that this kind of problem involves mixed mode crack propagation, making the use of numerical methods generally not so accurate and reliable as for two-dimensional models. In this paper, an experimental approach based on photoelasticity is presented: the determination of the stress intensity factors of cylindrical bodies under non-conformal contact condition is dealt with, being the aim to provide a tool for comparing numerical and approximate solutions. The method considers models with internal cracks naturally obtained without the need of any mechanical tool and enables the determination of the stress intensity factors for modes I–III in the critical points of a curvilinear (circular or elliptical) crack. The analysed case considers two cylinders with perpendicular axes. Results are critically discussed and compared with the ones of a well-established numerical approach: the comparison is satisfactory.