110 circumferential and radial dimensioned positions, well within tolerance of rotational equipment. One assembled part is shown in Fig. 12.5, where the cyan-colored band is the thermoset adhesive. 12.3.2 Adhesive Bond Verification The bonded parts were subjected to rotational loading as pure torsion, and torqued to failure. The smooth surface adhesivebonded area failed by a combination of cohesive and adhesive failure. All of the 57 square centimeters of adhesive bond failed simultaneously, and the failure occurred at a load of 2400 Nm. For design purposes, this corresponds to a shear load on the specimen of 15 MPa, that is average for a structural epoxy adhesive. Compared to a flat interface, such as with a symmetrical shear-load coupon, this cylindrical shaped strength is slightly more than can be achieved by the same adhesive in a flat area. This shear strength of the adhesive bond is less than 10 % of that of the base material steel, so is significantly low for joining. Fig. 12.4 Rotational parts slathered with cyan-colored adhesive, before assembly Fig. 12.5 Rotational parts assembled together with cylinder-shaped adhesive dollops P.J. Fritz et al.
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