Creep damage processes in cyclically loaded structural members

The paper contains the description of the cyclic creep damage law that allows to estimate the long-term strength of metallic materials in wide range of frequencies of loading and heating. Asymptotic methods and procedures of averaging in a period were used for deriving the damage laws

Vibration of a Square Hyperelastic Plate Around Statically Pre-Loaded State

International audienceStatic deflection and free nonlinear vibrations of thin square plate made of biological material are investigated. The involved physical nonlinearity is described through Neo-Hookean, Mooney-Rivlin and Ogden hyperelastic laws; geometrical nonlinearity is modelled by Novozhilov nonlinear shell theory. The problem is solved by sequentially constructing the local models that describe the behavior of plate in the vicinity of a certain static configuration. These models are the systems of ordinary differential equations with quadratic and cubic nonlinear terms in displacement, which allows application of techniques used in analysis of thin-walled structures of physically linear materials. The comparison of static and dynamic results obtained with different material models is carried out

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

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

Static and Dynamic Behavior of Circular Cylindrical Shell Made of Hyperelastic Arterial Material

International audienceStatic and dynamic responses of a circular cylindrical shell made of hyperelastic arterial material are investigated. The material is modeled as a combination of Neo-Hookean and Fung hyperelastic materials. Two pressure loads are implemented: distributed radial force and deformation-dependent pressure. The static responses of the shell under these two different loads differ essentially at moderate strains, while the behavior is similar for small loads. The main difference is in the axial displacements that are much larger under distributed radial forces. Free and forced vibrations around pre-loaded configurations are analyzed. In both cases the nonlinearity of the single-mode (driven mode) response of the pre-loaded shell is quite weak but a resonant regime with co-existing driven and companion modes is found with more complicated nonlinear dynamics

High temperature creep and damage accumulation in cyclically loaded axisymmetrical bodies of revolution

The paper presents the constitutive equations as well as the data of numerical simulation of creep-damage problems of cyclically loaded and heated axisymmetrical structural members. The procedure of constitutive equations deriving is discussed. The experimental and numerical data have been obtained for cyclically heated specimens made from high quality steel were compared in order to verify the flow rule and damage parameter equation. The problem of creep and damage accumulation in the nipples of the regenerator for catalytic cracking of petroleum was analyzed with consideration of different temperature cycle parameters

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

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

High temperature creep and damage accumulation in cyclically loaded axisymmetrical bodies of revolution

The paper presents the constitutive equations as well as the data of numerical simulation of creep-damage problems of cyclically loaded and heated axisymmetrical structural members. The procedure of constitutive equations deriving is discussed. The experimental and numerical data have been obtained for cyclically heated specimens made from high quality steel were compared in order to verify the flow rule and damage parameter equation. The problem of creep and damage accumulation in the nipples of the regenerator for catalytic cracking of petroleum was analyzed with consideration of different temperature cycle parameters

Circular Cylindrical Shell Made of Neo-Hookean-Fung Hyperelastic Material Under Static and Dynamic Pressure

The present study is devoted to the investigation of static and dynamic behavior of the three-layered composite shell made of hyperelastic material. Such a shell can be considered as a model of human aorta. Since soft biological materials are essentially nonlinear even in the elasticity zone, not only geometrical, but also physical nonlinearity should be taken into account. The physical nonlinearity of soft biological tissues is usually modeled by certain hyperelastic law. The law chosen for this study is the combination of the Neo- Hookean law, which describes the isotropic response at small strains, and Fung exponential law, that models the stiff anisotropic response of the collagen fibers at larger strains. Each of three shell layers has its own hyperelastic constants set. These constants are determined basing on experiential data [1]. The straindeflection relations are modeled with higher-order shear deformation theory [2]. Initially, the shell is preloaded with static pressure. Since the defection in our study is large we use the expression for pressure as a follower load [3]. The static problem is solved with the help of the local models method [4]. Afterwards, the free and forced dynamical response of the preloaded shell is studied both in vacuo and with still fluid inside. The modes of interest are the first axisymmetric mode and mode with two half-waves in circumferential direction (so-called collapse mode). It is found that static pressure decreases the dynamic nonlinearity and it is quite weak. At the same time, the presence of fluid makes the softening nonlinearity stronger as in case of shells of conventional material [5]