16 research outputs found
Probabilistic Analysis of LCF Crack Initiation Life of a Turbine Blade under Thermomechanical Loading
An accurate assessment for fatigue damage as a function of activation and
deactivation cycles is vital for the design of many engineering parts. In this
paper we extend the probabilistic and local approach to this problem proposed
in [1,2] and [3] to the case of non-constant temperature fields and
thermomechanical loading. The method has been implemented as a finite element
postprocessor and applied to an example case of a gas-turbine blade which is
made of a conventionally cast nickel base superalloy.Comment: 8 pages, 3 figure
A Probabilistic Model for LCF
Fatigue life of components or test specimens often exhibit a significant
scatter. Furthermore, size effects have a non-negligible influence on fatigue
life of parts with different geometries. We present a new probabilistic model
for low-cycle fatigue (LCF) in the context of polycrystalline metal. The model
takes size effects and inhomogeneous strain fields into account by means of the
Poisson point process (PPP). This approach is based on the assumption of
independently occurring LCF cracks and the Coffin-Manson-Basquin (CMB)
equation. Within the probabilistic model, we give a new and more physical
interpretation of the CMB parameters which are in the original approach no
material parameters in a strict sense, as they depend on the specimen geometry.
Calibration and validation of the proposed model is performed using results of
strain controlled LCF tests of specimens with different surface areas. The test
specimens are made of the nickel base superalloy RENE 80.Comment: 20 pages, 6 figure
Magnetic properties of small Pt-capped Fe, Co and Ni clusters: A density functional theory study
Theoretical studies on M (M = Fe, Co, Ni) and MPt (for
= 3, 4, 5, 20) clusters including the spin-orbit coupling are done using
density functional theory. The magnetic anisotropy energy (MAE) along with the
spin and orbital moments are calculated for M icosahedral clusters. The
angle-dependent energy differences are modelled using an extended classical
Heisenberg model with local anisotropies. From our studies, the MAE for
Jahn-Teller distorted Fe, Mackay distorted Fe and nearly
undistorted Co clusters are found to be 322, 60 and 5 eV/atom,
respectively, and are large relative to the corresponding bulk values, (which
are 1.4 and 1.3 eV/atom for bcc Fe and fcc Co, respectively.) However, for
Ni (which practically does not show relaxation tendencies), the
calculated value of MAE is found to be 0.64 eV/atom, which is
approximately four times smaller compared to the bulk fcc Ni (2.7
eV/atom). In addition, MAE of the capped cluster (FePt) is
enhanced compared to the uncapped Jahn-Teller distorted Fe cluster
Electron Correlation Effects in the Fe Dimer
The potential energy surface of the Fe dimer is investigated on the basis of density functional theory in th