Bernard Gross

Mode II Fatigue Crack Growth Specimen Development

A novel Mode II test specimen has been developed that has potential application in understanding phenomena associated with mixed-mode fatigue failures in high performance aircraft engine bearing races. The attributes of the specimen are as follows: it contains one single-ended notch, which simplifies data gathering and reduction; the fatigue crack grows in-line with the direction of load application; a single axis test machine is sufficient to perform testing; and the Mode I component is vanishingly small.

Analysis of Radially Cracked Ring Segments Subject to Forces and Couples

Results of planar boundary collocation analysis are given for ring segment (C-shaped) specimens with radial cracks, subjected to combined forces and couples. Mode I stress intensity factors and crack mouth opening displacements were determined for ratios of outer to inner radius in the range 1.1 to 2.5 and ratios of crack length to segment width in the range 0.1 to 0.8.

Mode I Crack Surface Displacements and Stress Intensity Factors for a Round Compact Specimen Subject to a Couple and Force

Mode I displacement coefficients along the crack surface and stress intensity coefficients are presented for a radially cracked round compact specimen, treated as a plane elastostatic problem, subjected to two types of loading; a uniform tensile stress and a nominal bending stress distribution across the net section. By superposition the resultant displacement coefficient or the corresponding stress intensity coefficient can be obtained for any practical load location. Load line displacements and stress intensity coefficients are presented for A/D ratios ranging from 0.40 to 0.95, where A is the crack length measured from the crack mouth to the crack tip and D is the specimen diameter. Through a linear extrapolation procedure, crack mouth displacements are also obtained. Experimental evidence and comparisons with other investigators shows that the results of this study are valid over the range of A/D ratios analyzed for a practical pin loaded round compact specimen.