Issue 41

Ch. F. Markides et alii, Frattura ed Integrità Strutturale, 41 (2017) 396-411; DOI: 10.3221/IGF-ESIS.41.51 404 the case for the “transtropic” material for which clearly γ rθ ( r , θ )≠γ rθ ( r , θ +Δ θ ). Moreover, it is observed that the differences in deformation between the particular “fictitious” isotropic and “transtropic” discs are more pronounced for ϕ o =60 o . (a) (b) Figure 4 : Deformed vs. undeformed (black dashed line) configuration of an element (Δ r , Δ θ ) (oriented along the loading axis and normally to it), for an isotropic (green line) and a “transtropic” (red line) disc, when the loading direction is ϕ o =20 o (a) and ϕ o =60 o (b) . The role of the length of the contact arc, 2ω o The specific parameter, i.e., the length of the loaded arc, is in general disregarded in practical applications of the Brazilian- disc test, since it is considered that the stress state at the disc center can be simulated as a biaxial stress field with a con-