Predicting the macroscopic shear strength of adhesively-bonded friction interfaces by microscale finite element simulations

Anaerobic adhesives are commonly used to enhance the shear strength of clamped friction joints between metal parts. Experimental results show that the total strength of the friction-bonded interface steadily increases with the clamping pressure. However, if weak anaerobics are used, the combined strength is lower than in the dry (purely friction) joint under high applied pressures. This paper seeks an explanation for this macroscopic behaviour by means of microscale finite-element simulations. The analyses show that the experimental results can be explained by assuming that: (a) however great the clamping pressure, a thin film of adhesive remains trapped between the crests of the mating surfaces; (b) under the high local pressure the shear strength of this film is greater than the regular adhesive’s at no pressure; (c) the stronger adhesives entail a higher increase than the weaker adhesives.