Steady-State Creep Analysis of Pressurized Pipe Weldments by Perturbation Method

The stress analysis of pressurized circumferential pipe weldments under steady state creep is considered. The creep response of the material is governed by Norton's law. Numerical and analytical solutions are obtained by means of perturbation method, the unperturbed solution corresponds to the stress field in a homogeneous pipe. The correction terms are treated as stresses defined with the help of an auxiliary linear elastic problem. Exact expressions for jumps of hoop and radial stresses at the interface are obtained. The proposed technique essentially simplifies parametric analysis of multi-material components.Comment: 17 pages, 6 figure

Edge Effects in Moderately Thick Plates under Creep-Damage Conditions

The late F.P.J. Rimrott has published during his scientific life more than 200 refereed articles and conference papers. Various papers among them were devoted to the creep and plasticity analysis in metallic thin-walled structural elements mostly published in the period from 1958 till 1964. With regard to this early period below we discuss finite element solutions for moderately thick plates under creep-damage conditions based on shell and solid type finite elements. The results illustrate the time-dependent stress redistributions in the edge zones. We show that the transverse normal and shear stresses may have a significant influence on the damage evolution and must be considered in numerical lifetime estimations

Eigen-vibrations of Plates made of Functionally Graded Material

Within the framework of the direct approach to the plate theory we consider natural oscillations of plates made of functionally graded materials taking into account both the rotatory inertia and the transverse shear stiffness. It is shown that in some cases the results based on the direct approach differ significantly from the classical estimates. The reason for this is the non-classical computation of the transverse shear stiffness

Application of the Classical Beam Theory for Studying Lengthwise Fracture of Functionally Graded Beams

The present paper deals with analysis of lengthwise cracks in linear-elastic functionally graded beam configurations. A general approach for deriving of the strain energy release rate is developed by applying the classical beam theory. A crack located arbitrary along the beam thickness is considered, i.e. the crack arms have different thicknesses. The approach holds for beams which are functionally graded in the thickness direction (the modulus of elasticity can be distributed arbitrary along the thickness of the beam). The approach is applied to analyze the strain energy release rate for a lengthwise crack in a functionally graded cantilever beam. The beam is loaded by one concentrated force applied at the free end of the upper crack arm. An exponential law is used to describe the continuous variation of the modulus of elasticity along the beam thickness. The solution to the strain energy release rate in the cantilever beam is verified by applying the Jintegral approach. The solution is verified further by using the compliance method for deriving the strain energy release rate. The effects of crack location along the beam thickness, crack length and material gradient on the strain energy release rate in the functionally graded cantilever beam are analyzed by applying the solution derived

Identification of effective properties of particle reinforced composite materials

For the determination of effective elastic properties an energy averaging procedure has been used for particle reinforced composite materials. This procedure is based on finite element calculations of the deformation energy of a characteristic volume element. The proposed approach allows the determination of effective properties of particle reinforced composite with acceptable precision. The calculated effective properties of the composite are found in range between upper and lower Hashin-Shtrikman bounds. The averaging elastic properties of the composite depend on the properties of the particles, matrix volume fraction of the particles and some parameters taking into account the influence of the interphase between matrix and particles. These dependencies can be presented by simple analytical functions approximatically. An identification procedure basing on numerical experiments allows the estimation of the unknown approximation parameters. The obtained functions describe precisely the numerical data for any relationship between material constituents

Numerical Analysis of a Steam Turbine Rotor subjected to Thermo-Mechanical Cyclic Loads

The contribution at hand discusses the thermo-mechanical analysis of a steam turbine rotor, made of a heat-resistant steel. Thereby, the analysis accounts for the complicated geometry of a real steam turbine rotor, subjected to practical and complex thermo-mechanical boundary conditions. Various thermo-mechanical loading cycles are taken into account, including different starting procedures (cold and warm starts). Within the thermal analysis using the FE code ABAQUS, instationary steam temperatures as well as heat transfer coefficients are prescribed, and the resulting temperature field serves as input for the subsequent structural analysis. In order to describe the mechanical behavior of the heat-resistant steel, which exhibits significant rate-dependent inelasticity combined with hardening and softening phenomena, a robust nonlinear constitutive approach, the binary mixture model, is employed and implemented in ABAQUS in two different ways, i.e. using explicit as well as implicit  methods for the time integration of the governing evolution equations. The numerical performance, the required computational effort, and the obtained accuracy of both integration methods are examined with reference to the thermo-mechanical analysis of a steam turbine rotor, as a typical practical example for the numerical analysis of a complex component. In addition, the obtained temperature, stress, and strain fields in the steam turbine rotor are discussed in detail, and the influence of the different starting procedures is examined closely

Solution of Creep-Damage Problems for Beams and Rectangular Plates Using the Ritz and the Finite Element Method

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Vergleichende Untersuchungen zur Modellierung und numerischen Berechnung mehrschichtiger Rotationsschalen

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Numerical Treatment of Finite Rotation for a Cylindrical Particle

A problem for a rotation of a rigid cylindrical body in a medium is analyzed based on the laws of dynamics. The resistance moment is taken into account. For the numerical solution equations governing the rotary motion are formulated in terms of the right angular velocity and the rotation vector. The equations are solved numerically applying the Runge-Kutta method. The results illustrate the time variation of the unit vector spanned on the longitudinal axis of the body. By neglecting the moment of viscous friction the numerical results agree well with the classical analytical solution