PSI - Issue 28

Sergey Smirnov et al. / Procedia Structural Integrity 28 (2020) 234–238 Author name / Structural Integrity Procedia 00 (2019) 000–000

237

4

where σ n is the stress normal to the area on glue-metal boundary, σ 0 is the yield stress of the adhesive material. By the value of hardness, according to the recommendations given in Morozov et. al., 1999, we have calculated the value of stress σ 0 = 110 MPa for the polymer adhesive at the yield point by the relation σ 0 ≈ 0.3 H (where H is hardness.) The values of hardness and the normal elastic modulus Е for the epoxy glue ETP-2 were taken from Smirnov et. al., 2017. The specific surface energy of shear-induced adhesive failure was calculated as

2  

W t

h



2

G

where G = 2 E /(1+ ν ) is the elastic shear modulus, ν is Poisson’s ratio. The dependence

  W k t , similarly to the dependence of ultimate adhesive failure strain used in Smirnov et. al.,

2014, was sought in the form of an exponent,     a k W k a t 1 0 exp  

(1)

where а 0 and а 1 are empiric coefficients. Figure 3 shows a diagram of the ultimate specific surface work of the shear-induced adhesive failure for the glued sandwich under study and the exponential dependence (1). It is obvious that, under compressive normal stresses ( k < 0), the value of the work spent on shear-induced adhesive failure increases rapidly.

Fig 3. Diagram of specific surface work of shear-induced adhesive failure

4. Conclusion Based on Brazilian test results, the dependence of the specific surface energy of adhesive failure on the shear stress state under compressive normal stresses has been obtained for a sandwich composed of AMg6 aluminum-magnesium alloy specimens glued together by the ETP-2 epoxy glue. Acknowledgements The experimental procedures for studying polymer coatings were developed according to the work plan of IES UB RAS, theme AAAA-A18-118020790145-0. The Russian Science Foundation financially supported (project 19-19-