Reliability Evaluation of Stochastically Heterogeneous Thick-walled Pipe by Long-term Strength Criterion

N. N. Popov ; L. V. Kovalenko

Journal of Samara State Technical University, Ser. Physical and Mathematical Sciences, no. 1 (2014), pp. 86-92

Résumé

We have developed a method of probabilistic reliability evaluation of microheterogeneous thick-walled pipe, based on the already received solution of the stochastic creep boundary value problem. The rheological properties of the material were described using random function of one variable (radius $r$). Damage parameter $0\leq\omega(t)\leq1$ was introduced here to study the process of degradation of the material during creep stage. Also the power law of the rate of $\omega(t)$ change on the equivalent stress $\sigma_{\text{eq}}$, determined by Sdobyrev criterion, is assigned. The reliability evaluation is made by the mean integral value of the equivalent stress. We have found a random time before destruction and its distribution function, which was approximated by lognormal law. The problem of the probability of failure-free operation was calculated for a thick-walled microheterogeneous pipe with the specified parameters. The obtained results allow to evaluate reliability of stochastically inhomogeneous axisymmetric structural elements if necessary statistical data are obtained from the experiment.

Détail

Keywords: steady-creep state, thick-walled pipe, microheterogeneous material, stochastic boundary value problem, long-term strength, reliability function.