PSI - Issue 57

Yann Chevalon et al. / Procedia Structural Integrity 57 (2024) 633–641 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

636

4

Fig. 4 (a) Typical polymer stain/stress set of curves for different temperatures (b) Dependency of the Young modulus to the temperature.

Figure 4(a) provides an illustration of the shift induced by an increase of temperature in the relationship between stress and strain. Figure 4(b) provides an illustration of the Young modulus dependency to temperature. 2.3. Internal forces generated by bending. The extruded layers deform cyclically under imposed displacements, such as curvature variations rather than under imposed loading. The figure 5(a) provides a representation of the initial and final configuration of the system. The figure 5(b) illustrates the location of tensile strains on the final configuration of the flexible.

Fig 5 (a) curvature variation on a flexible pipe (b) Straight and bent configuration of a pipe with tensile strain location represented by the Greek letter e .

A change in curvature results in a bending action of the pipe. Therefore, internal forces develop in the different layers. For the extruded layers, the configuration is a hollow cylinder, with tensile strains developing on the extrados and compressive strains on the intrados, as represented in figure 5. It has also been presented in section 2.1 that the surfaces of the extruded layers have irregularities, therefore stress concentration factors. This is taken into account by converting the strains from bending deformation into stresses via the Young modulus. This conversion has the double advantage of enabling the method to account for temperature effects, but also quantifying the SCF effects. SCF are taken from literature, but also estimated through FEA analysis, and, at the time this paper is written, experimental verifications are about to start on controlled geometry of polymeric samples.