TY - BOOK

T1 - Characterisation of Residual Stresses using Neutron Diffraction and Finite Element Simulation

AU - Cihak, Ulrike

N1 - no embargo

PY - 2007

Y1 - 2007

N2 - The aim of the present thesis is the experimental verification of the simulated residual stresses within forged, large scale components. Neutron diffraction was used to asses the residual stresses within a forged and water-quenched turbine disc with a thickness of up to 25 mm. During machining, residual stresses within the disc can cause a physical distortion of the component. This can lead to failure of the finished component if the dimensional tolerances are not met. Therefore, a finite element model is required to determine the residual stress state within the as-forged component prior to machining and minimize the distortion during a machining process. In order to avoid any cross-couplings, the experimental and the finite element approach are treated strictly independently. A detailed parameter study shows that the heat transfer coefficient is a key parameter of the finite element model and has to be defined as a function of the surface temperature. The experimental part of the work focuses on the homogeneity of the residual stress states and the repeatability of the neutron diffraction measurements. Furthermore, the potential of an up-sizing of the finite element model to larger components is investigated. The comparison of experimentally determined stress results for a small model plate and the results obtained on the relatively large turbine disc show, that the finite element model correctly simulates the residual stress state in both samples.

AB - The aim of the present thesis is the experimental verification of the simulated residual stresses within forged, large scale components. Neutron diffraction was used to asses the residual stresses within a forged and water-quenched turbine disc with a thickness of up to 25 mm. During machining, residual stresses within the disc can cause a physical distortion of the component. This can lead to failure of the finished component if the dimensional tolerances are not met. Therefore, a finite element model is required to determine the residual stress state within the as-forged component prior to machining and minimize the distortion during a machining process. In order to avoid any cross-couplings, the experimental and the finite element approach are treated strictly independently. A detailed parameter study shows that the heat transfer coefficient is a key parameter of the finite element model and has to be defined as a function of the surface temperature. The experimental part of the work focuses on the homogeneity of the residual stress states and the repeatability of the neutron diffraction measurements. Furthermore, the potential of an up-sizing of the finite element model to larger components is investigated. The comparison of experimentally determined stress results for a small model plate and the results obtained on the relatively large turbine disc show, that the finite element model correctly simulates the residual stress state in both samples.

KW - Eigenspannungen

KW - Neutronen

KW - Finite Elemente

KW - Simulation

KW - DEFORM

KW - Superlegierungen

KW - Inconel 718

KW - Residual Stress

KW - Neutron

KW - Finite Element

KW - Simulation

KW - Superalloys

KW - Inconel 718

KW - DEFORM

M3 - Doctoral Thesis

ER -