Mode I stress intensity factors of sickle-shaped surface cracks in round solid bars under bending moment

Abstract

Sickle-shaped crack may occur on the surface of solid round cylinder under some specific reasons such as design discontinuities or material defects. This type of crack is capable to grow circumferentially around the bar and it is called a sickle-shaped surface cracks. The complete solution of stress intensity factors (SIF) of sickle-shaped surface cracks is hard to find and therefore the objective of this paper is to present the behaviour of these cracks under remotely applied bending moment. In order to understand the role of these cracks, there are seven crack aspect ratios, a/b considered, ranging from 0.0 to 1.2. For each crack aspect ratio, there are six relative crack depths, a/D used ranging from 0.1 to 0.6. ANSYS finite element program is used to model the crack. Stress intensity factor (SIF) which is based on the J-integral is used to characterize the cracks. For relatively shallow cracks (a/D  0.3), the role of SIFs along the crack front is insignificant regardless of a/b. However, for the deeper cracks (a/D > 0.3), the effect of a/b is tremendous on the SIFs. If a/b is increased from 0.0 to 1.2, higher SIFs are obtained around the central compared with the outer regions of the crack fronts. This is due to the fact that the circumferential cracks at both sides of the bar experience lack of mode I opening mechanism compared with the crack faces at the upper side cracks. It is suggested that the phenomena of crack closure are not only caused by the plastic deformation, surface roughness and other related factors but the shape of crack also plays an important role.

Numerical study of contact wire tension affecting dropper stress of a catenary system

“…Then, the fracture response is provoked. [20][21][22] In the actual operation of the contact wire, the tension at both ends of the contact wire can be increased scientifically, which can effectively reduce the fluctuation amplitude of the contact force between the pantograph and the catenary system. Through optimizing the relationship between the pantograph and the catenary system, and further reducing the failure caused by the fatigue fracture of the dropper, it can meet the operation safety of the electrified train.…”

Distribution of Mode I Stress Intensity Factors for Single Circumferential Semi-Elliptical Crackin Thick Cylinder

“…For this study, six contours around the crack front were created, and SIFs for each contour along the crack front were calculated. A proper selection for which contour gives more reliable results considered an important task, this is because of the large material shrinkage in the region close to the crack tips as mentioned by Ismail [19]. Therefore, the results of the 5th contour were selected.…”

A closed expression for the Stress Intensity Factor of concave fatigue cracks in rotating shafts

“…Further, Carpinteri [24] calculated the SIF on determined positions of the front of a concave crack contained in a circumferential notch of a shaft. Ismail [27] analyzed the SIF along the crack front for the concave shaped surface cracks in rounds bars, and investigated the effects on the SIF of the crack aspect ratio and the relative crack depth. Rubio [26] proposed a SIF expression for concave open cracks as a function of the shape factor, the relative crack depth and the relative position on the front.…”