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.

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Suggestions for testing of notched or cracked three-point bend specimens are presented that (1) correct displacement measurement errors resulting from misalignment between the load applicator and specimen; (2) account for coincidental strains not associated with the work of crack extension; (3) simplify record analysis and processing; and (4) extend displacement gage range without sacrifice of sensitivity or accuracy. These testing details are particularly applicable to procedures in which the crack extension force J1 is determined from the work done on the specimen.

A mode II specimen for fatigue crack growth measurements was described by Buzzard, Gross and Srawley [1]. Subsequently Buzzard [2] published results of displacement measurements at the crack mouth and at a selected point on the crackline for this specimen. A preliminary analysis of crack mouth displacements and stress intensity factors using boundary value collocation was also given [1], The analysis while giving qualitatively useful results could not accurately represent all boundary conditions. The present paper presents a finite element analysis of the mode II specimen which gives more accurate stress intensity factors and displacement results than previously presented. In addition, load point displacements were measured in order to allow an experimental determination of the stress intensity factors.

Mode II and Mode I calibrations of the NASA Lewis Research Center Mode II fatigue specimen were performed experimentally over crack length to specimen width ratios (a/W) of 0.5 to 0.9. Mode II displacements were measured both at the specimen notch mouth and at the intersection of the notch with the centerline of the loading pin holes. Mode I displacements were measured across the span of the specimen at the loading pins' centerline. Analytical stress intensity factor coefficients for both Mode II and Mode I are also presented.