Creep and damage in shells of revolution under cyclic loading and heating

Abstract

Creep of cyclically loaded thin shells of revolution and their fracture due to creep and fatigue mechanisms are studied. Creep-damage equations for steels and nickel-based alloys are built by the use of scalar damage parameter. Constitutive equations were derived using the method of asymptotic expansions and averaging over a period of cyclic loading. The cases of fast and slow varying of temperature and loading are regarded. General problem statement and method for solution of creep problems at cyclic loading are presented. Strain-stress state in shell structures is determined by the use of homemade FEM creep-damage code, where the finite element of conical shell is used. Results of creep-damage problem for conical panel are discussed.

Deformation and damage of nuclear power station fuel elements under cyclic loading

“…This article contains an example of an approach that extends the method of forced oscillations analysis to model the creep-damage material behavior 13 in conditions of radioactive irradiation. The deformation, stress redistributions, and hidden damage growth in stationary fuel elements subjected to varying internal pressure due to temperature oscillations of cooling flow are considered.…”

“…This contradiction is overcome by temporal numerical integration of the state equations. 13 We use the third-order predictor-corrector scheme, which describes the behavior of stiff systems satisfactory. 28 Knowing the values of c true¯ t − Δ t , c true¯ t , c · true¯ t , and stresses σ true¯ t z at an arbitrary time step t , we find the solution at t = t + Δ t …”

“…The method presented has been implemented in computer code with pre- and post-processing programs. 13,29…”

“…11 Its mathematical justification for creep, strain and damage parameter functions (based on methods of asymptotical expansions and averaging over a period of stress variation) have been done. 11–13…”

Creep calculations at steady growth of temperature

“…Окремим випадком є циклічне змінювання температури за часом , яке, зокрема, є випадком наведених вище умов. Для моделювання цього процесу використовують ефективний метод осереднення на періоді змінювання температури за часом та отримують осереднені рівняння стану, в яких застосовується значення незмінної за часом температури [8]. Розглядаючи ці задачі, можливо зробити висновок, що в усіх з них знаходження температурних полів передує розрахункам повзучості, в яких попередньо знайдені розподіли температури грають роль початкових умов.…”