274 E.G. Koricho et al. Fig. 33.5 Comparison of logarithmic S–N Curves of conventional and hybrid bolted joints 0 500 1000 1500 2000 2500 0 10 45 50 55 60 65 70 75 80 y=26.42+59.66*exp(-0.00075*N) % of ultimate static load Number of cycles, [-] Conventional bolt Hybrid bolt y=41.79+44.66*exp(-0.00098*N) Fig. 33.6 Failure modes: (a) pre-cycled conventional bolted joints, (b) pre-cycled hybrid GCbolt, (c) failure mode of washers at 45 % of UFL Fig. 33.7 Stress-versus number of cycles diagrams of conventional and hybrid bolted joints 100 1000 10000 100000 1000000 0 50 100 150 200 250 300 350 s=115.54+1469.4*N-0.358 Shear stress, MPa Number of cycles, [-] Conventional bolt Hybrid bolt s=120.77+2266.34*N-0.45 Da logNCb (33.1) N D10. b/a (33.2) Where a and b are constants that can be found from the experimental tests, as shown in Fig. 33.7. N is number of cycles. For both the conventional and hybrid bolted joints, which were subjected to 30 % of UFL, the fatigue tests were interrupted at one million cycles and quasi-static tensile tests were performed to obtain the residual strength. Figure 33.8 presents the results of these tests as well as reproducing the results of the quasi-static strength tests on the as-fabricated specimens previously presented in Figure 33.3. As expected, the as-fabricated conventional bolted joint exhibit higher strength than does the pre-cycled specimen. The pre-cycled specimen shows moderate strength reduction, in this particular case by 6 %. Figure 33.6 showed the fatigue induced damage around the hole of the pre-cycled conventional bolted joint, which is evidence
RkJQdWJsaXNoZXIy MTMzNzEzMQ==