Experimental Assessment of a Micro-Mechanical Model for the Static Strength of Hybrid Friction-Bonded Interfaces

D Castagnetti,E Dragoni

doi:10.1080/00218464.2012.747179

Abstract

Anaerobic adhesives are thermosetting acrylic polymers commonly used to improve the performance of most metal joints. Researches on the static strength of hybrid joints, available in the technical literature, show scanty and contradictory results that do not explain the effect of anaerobic adhesive on the hybrid joint behaviour. An early study by one of the authors of the present study formulates a micro-mechanical model describing the shear power of anaerobic adhesives as a function of the intimate properties of adherends and adhesive at the interface. According to the micro-mechanical model, the high local pressure acting on the thin film of adhesive trapped between the crests of the mating surfaces improves the film shear strength upon the adhesive's shear strength at zero pressure. The present work aims to assess this micro-mechanical model through a systematic experimental campaign. The tests are conducted on simple tubular specimens and consider three variables over two levels: adhesive-type (weak and strong anaerobic), pressure level during polymerization (0.5 and 134 MPa), and pressure level during failure test (0.5 and 134 MPa). The results confirm the proposed micro-mechanical model, and highlight that shear strength slightly differs by applying pressure before or after polymerization.

Highlights

Anaerobic adhesives are thermosetting acrylic polymers, which are introduced in most metal joints, in particular those relying on mechanical tightening, to obtain efficient friction-bonded interfaces
Many researches investigate the strength of hybrid joints [1]-[14]
For each of the four experimental configurations investigated with Loctite 243, Figure 4 reports the diagram of the torque load applied to the specimen as a function of the rotation angle

Summary

Introduction

Anaerobic adhesives are thermosetting acrylic polymers, which are introduced in most metal joints, in particular those relying on mechanical tightening, to obtain efficient friction-bonded interfaces. Bolted joints, flanged couplings or interference fits are typical Fo examples. Many researches investigate the strength of hybrid joints [1]-[14]. In [2], Mahon presents joint design parameters, test results and calculation techniques for bonded friction couplings, with particular reference to automotive drivetrain applications. Romanos [3] provides information on static and fatigue strength of friction bonded interfaces produced using appropriate industrial ev assembly techniques. Bartolozzi et al [4] show that the strength of hybrid joints is affected ie by various factors such as, for example, the coupling pressure. In [5], Croccolo et al

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