PSI - Issue 47

7

Abderrahim Khtibari et al./ Structural Integrity Procedia 00 (2023) 000–000

A. Khtibari et al. / Procedia Structural Integrity 47 (2023) 855–862

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γ = 2.6 γ = 2.16 γ = 1.93 γ =1.7 Miner

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0.2 Damage by unified theory

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Fig. 6. Evolution of the damage estimated by the unified theory. From Fig.6 we can note that the damage process of chlorinated polyvinyl chloride specimens is represented by a series of curves for different values of loading level γ , each curve is associated with a residual ultimate stress and each residual ultimate stress reflects a degradation level. The concavity of the curves increases in the opposite direction to that of γ as it increases, in fact, for a low ultimate stress level γ = 1.7; the concavity of the damage curve is maximum and tends towards Miner's linear model at a high load level, this parameter γ takes a very low value for specimens subjected to high temperature, which was shown in Fig.7. The damages corresponding to a loading level γ =1.93 and γ =2.16 seem to be unstable since their concavities are accentuated. From the variation of concavity of curve, we are found three stages of damage, The first stage equivalent to the initiation of damage, it starts in the intervals β = [0 - 20%]. The second stage is situated in the intervals [ 20 – 78%], this zone specifically is responsible to the propagation of damage, at the end of this stage the life fraction reaches its critical value which correspond a critical damage that necessitates predictive maintenance. At the third stage, the critical life fraction appears as 78 %. The material in this zone becomes unusable and must be rejected. Based upon a careful comparison of the two damage calculation approaches, we simply conclude that both models (static damage and unified theory) are entirely appropriate for describing the damage in CPVC and the outcomes obtained from static damage are also in line with unified theory. 4. Conclusion In this paper, we have presented the impact of temperature on mechanical behaviour and on damage of (CPVC) Chlorinated Polyvinyl Chloride specimens subjected to tensile tests under temperatures from-10 to 90°C. In this context, the mechanical properties of CPVC, such as Yong’s modulus, yield stress and strain at break, are dependent on temperature. The modulus of elasticity and yield stress are decreased as the temperature increased. On the other hand, we can note, the strain at break increases as the temperature increased. This increasing is explained by the change in mechanical behavior of CPVC, from brittle to ductile under the temperature from -10 to 90°C. We can note also that the static damage evolves with the increase in life fraction. Based upon a comparison of the two damage calculation approaches, one of which was generated through static damage and the other, which was acquired via the use of unified theory, we simply conclude that both models of static damage and unified theory are entirely appropriate to describe the damage in CPVC they give a critical life of fraction near the value of 78%.