| Because of its significant advantages like excellent adhesive properties, uniform stress distribution in adhesive joints, corrosion resistance, simplicity in operation, epoxy adhesive bonding technology has been widely used in practical engineering fields. However, the fatigue properties of the epoxy butt bonding specimens are totally different with homogeneous materials. Therefore, it is very necessary to study the fatigue properties epoxy butt bonding specimens in actual application environment.Firstly, the effects of surface roughness of the bonding interface, adhesive curing temperature and curing time on the adhesive properties of the specimens are studied. The results show that the adhesive strength of the specimens increases with the increasing of the surface roughness at first, then decrease. The optimum roughness had been obtained by experimental method. When curing temperature exceed 90℃, the adhesive strength of the specimens decrease while the curing temperature increases, 60℃ is the optimum curing temperature. When the curing time is longer than 6h, adhesive strength of specimens doesn’t improve significantly, 6h is the optimum curing time.Secondly, the uniaxial fatigue behaviors of the specimens are studied. The results show that the adhesive strength of aluminum-epoxy butt bonding specimens is 23.0MPa, the adhesive strength of No.45 steel-epoxy butt bonding specimens is 16.7MPa. The fatigue life of the specimens decreases along with the increase of the fatigue stress amplitude. Simulation results show that the length of the initial crack of the butt bonding specimens is 0.035 mm, typical stress concentration phenomena appears near the bonding interface at 0.05 mm, the length of the critical crack size is 0.33 mm. Both of the S-N curve model and Paris fatigue life model are able to predict the fatigue properties of the butt bonding specimens. Compared with the S-N curve model, Paris fatigue crack life model is more suitable to predict the fatigue life of the butt bonding specimens which have higher bond strength and longer fatigue life.At last, multiaxial fatigue properties of the epoxy butt bonding specimens were studied. The results show that the fatigue properties of the butt bonding specimens are weakened by the additional strengthening effects generated by the multiaxial non-proportional loading conditions, the fatigue life of the specimens is reduced at the same time. Because of the maximum phase difference between the normal stress and shear stress, the fatigue life of the butt bonding specimen under the conditions of the circle path is shortest. The fatigue life decreases along with the increase of the fatigue stress cycle. The fatigue life of butt bonding specimens decreases exponentially along with the increase of the equivalent stress amplitude. Although the S-N curve model can predict the multiaxial fatigue life of the butt bonding specimens, but the prediction accuracy decreases and the error increases significantly. |
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