Issue 43

F. Majid et alii, Frattura ed Integrità Strutturale, 43 (2018) 79-89; DOI: 10.3221/IGF-ESIS.43.05 81 This paper highlight a new and simplified approach for the industrials to get through the fastidious checks required by the different codes. On the one hand, we propose two ways to get fast to this purpose. The first approach is an accelerated damage creation through notches in HDPE pipes. From the latter, ultimate and residual pressures have been measured and used in a static damage model obtained through the Eq. (3). The establishment of the corresponding graph give rise to the prediction of the damage behavior of HDPE pipes. On the other hand, the same thing, which has been done through experimental burst tests, can be done only by theoretical calculations through rupture pressure formulas or the newly developed formulas presented in this paper. From then, we get to the theoretical static damage evaluation and to the plot of the damage curves, which tells about the material behavior. Figure 2 : Damage building methodology. Notch depth (mm) Life fraction (β) Burst pressure (bar) 0 0 63.2 1 0.17 57.8 1.5 0.26 49.7 2 0.34 47.5 2.5 0.43 42.3 3 0.52 37.5 3.5 0.60 23.5 4 0.69 20.4 4.5 0.78 18.2 5 0.86 11.9 Table 1 : Burst pressure evolution in function of the life fraction. THEORY Rupture pressure theories everal theories have been developed to predict the rupture of a cylinder under pressure by determining the limit loads. Hill, in 1950, developed a theory predicting the pressure at boundary load conditions. It gives the evolution of the internal pressure at break as a function of the value of the stress σ y , the internal diameter D 0 and the external diameter D i [7]. For the same purpose, Nadai proposed calculating the burst pressure using the ultimate stress instead of the yield S