Mechanical Stress Evaluation by Neutrons and Synchrotron Radiation

Paper Title Page

Authors: Krzysztof Wierzbanowski, Jacek Tarasiuk, Alain Lodini
Abstract: The genetic algorithm method was used in the present work as an alternative to classical calculation methods. It can be used in the situations where we search an optimal solution and a problem has many variable parameters. In this work the genetic algorithm method was applied in order to decompose the texture function into ideal components and also to optimize elastic constants by an appropriate choice of texture function. These example applications of genetic algorithm method show its potential in the field of material engineering.
Authors: Kenji Suzuki, Takahisa Shobu
Abstract: Material of the specimen was austenitic stainless steel (SUS316L). The specimens were given tensile plastic strains from 0% to 55%. The Vickers hardness of the specimen corresponded to the plastic strain. The residual macrostress was measured by Mn-Kα radiations. The residual macrostress of the annealed specimen had a small compression and changed into a tension after ten- sile plastic deformation. The specimen with 1% plastic strain showed the maximum tensile residual stress. To examine the dependency of the residual stress on the lattice plane, the residual microstress for each lattice plane was measured by hard synchrotron X-rays. The residual microstress was related with Young’s modulus which was calculated by Kro¨ ner model. A new method, 2θ-cos2 χ method, was proposed to solve the problem of coarse grains and it was excellent in comparison with the sin2 ψ method.
Authors: M.O. Acar, P. John Bouchard, Joao Quinta da Fonseca, Michael E. Fitzpatrick, S. Gungor
Abstract: Neutron diffraction has been used to investigate the weld residual stresses and the intergranular residual strains in butt-welded 316H pipes. Measurements have been made on pipes subjected to varying degrees of plastic pre-straining before welding, in order to assess the effects of plastic strain on the weld residual stresses and the intergranular strains in the material. The intergranular strains following plastic deformation will also be affected by the annealing effect of the welding. Pipes were initially prepared with plastic strain of 0, 10, 15, 20 and 25% plastic deformation. Thereafter, the pipes were cut in half and welded with a circumferential butt-weld. Bar specimens were extracted from the remote end of the 0, 10, 15, 20 and 25% pre-strained and welded pipes. Cross-weld bar specimens were also machined from the 0 and 20% pre-strained and welded pipes. Neutron diffraction measurements were made at ENGIN-X, ISIS and FRM-II, Munich. The aim of this paper is to evaluate the intergranular strains developed after pre-straining from measurements made in remote bar specimens from the remote-end of the pipes. The annealing effect of the welding cycle on the intergranular strains is also studied, with measurements done at several points on cross-weld bar specimens, obtaining the strain response of different hkl lattice planes. The results show that the {200} and {220} planes are at the extremes of response during loading. Furthermore, the welding thermal cycling relaxed the intergranular strains from the prior plastic deformation.
Authors: Suraiya Zabeen, Michael Preuss, Philip J. Withers, Sven Spanrad, Jie Tong, John Schofield
Abstract: The current study investigates the effect of foreign object damage (FOD) on the pre-existing compressive residual stress field associated with laser shock peening (LSP) and its evolution upon combined LCF/HCF cycling. FOD was introduced onto an aerofoil-shaped specimen that had been previously LSP treated through ballistic impacts at angles of 0° and 45° to the leading edge. It is shown that the FOD notch created by 45° impact was asymmetric in shape and smaller in depth compared to that created at 0° impact. Significant through thickness compression was introduced parallel to the leading edge as a result of the LSP process. The residual strain distribution was mapped around the FOD notch by synchrotron X-ray radiation. The results show predominantly compressive stresses ahead of the notch, being greater for the 0 compared to 45 impact. No significant stress relaxation was observed after a combined (1000 HCF cycles superimposed on 1 LCF cycle) cycle.
Authors: M.K. Khan, Michael E. Fitzpatrick, L.E. Edwards, S.V. Hainsworth
Abstract: The residual strain field around the scratches of 125µm depth and 5µm root radius have been measured from the Synchrotron X-ray diffraction. Scratches were produced using different tools in fine-grained aluminium alloy AA 5091. Residual stresses up to +1700 micro-strains were measured at the scratch tip for one tool but remained up to only +1000 micro-strains for the other tool scratch. The load-displacement curves obtained from nanoindentation were used to determine the residual stresses around the scratches. It was found that the load-displacement curves are sensitive to any local residual stress field present and behave according to the type of residual stresses. This combination of nanoindentation and synchrotron X-rays has been proved highly effective for the study of small-scale residual stresses around the features such as scratches.
Authors: Yoshihisa Sakaida, Takanori Serizawa, M. Kawauchi, M. Manzanka
Abstract: A motorcycle transmission gear of chromium-molybdenum steel with 0.2%C was carburized in carrier gas. Carburizing process including heating, carburizing, diffusing and quenching was simulated using elastoplastic finite element method. The carbon content, hardness, residual strain and residual stress fields of gear were analyzed. The unstressed lattice plane spacing and residual strains of the interior near the internal spline of gear were experimentally measured by synchrotron x-ray and neutron diffraction methods. As a result, the analyzed carbon content and hardness gradients of gear accorded with the experimental results. The radial, hoop and axial directions of cylindrical gear were found to be not always principal axes of residual stress field. On the other hand, the analyzed residual strains in the radial, hoop and axial directions of gear slightly discorded with the experimental results. Although correlation between the measured three strains was similar to that of the weighted average of analyzed strains, residual strain and stress fields of motorcycle transmission gear could not be accurately predicted at the present finite element analysis. It was concluded that carbon diffusion phenomenon and resultant hardening could be analyzed by the finite element method, and the actual interior residual strain and stress fields should be nondestructively measured by neutron diffraction method.
Authors: Jeremy Epp, Thomas Hirsch, Martin Hunkel, Robert C. Wimpory
Abstract: The present work has been executed within the framework of the collaborative research center on Distortion Engineering (SFB 570) in order to evaluate the residual stress state of a disc after carburizing and quenching as well as to validate a simulation procedure. The combined use of X-ray and neutron diffraction analysis provided information about the residual stress states in the whole cross section. However, the stress free lattice spacing d0 for the neutron diffraction experiments is problematic and induces systematic uncertainties in the results and the application of a force balance condition to recalculate d0 might be a solution for improving the reliability of the results. Comparison of experimental results with simulation showed that an overall satisfying agreement is reached but discrepancies are still present.
Authors: Abdeljalil Nady, Herve Bonnefoy, Vincent Klosek, Marie Helene Mathon, Alain Lodini
Abstract: The objective of this study is to investigate the effects of Heat Affected Zone produced by Plasma Transferred Arc process and residual stress in substrate steel 55NiCrMoV7. In this study, based on ABAQUS code, a sequentially coupled thermal, metallurgical, mechanical 2-D finite element model is developed. In the numerical simulations, the coating and Heat Affected Zone are used to predict the residual stresses. The simulation results revealed that the final residual stress in substrate steel do seem to be influenced by the HAZ.
Authors: Vladimir Luzin, Jiří Matějíček, Thomas Gnäupel-Herold
Abstract: A range of different spraying techniques can be used to coat the surfaces of engineering components. These techniques are based on different principles and can involve high temperature (plasma spray), high kinetic energy (cold spray) or both (HVOF spray – High-Velocity Oxi-Fuel). Resultant residual stress in such coatings, being a characteristic of the spraying process, can reveal details of the stress formation mechanism. When its dependence on the physical parameters and conditions of the spraying process is established, this knowledge can be used for the prediction and control of stress that occurs in applications. Neutron diffraction is a suitable method for obtaining stress distribution in such coatings. Residual stresses in two-phase Cu+W coatings made by water stabilized plasma spraying were studied. Two-phase coatings develop both significant microstress (inter-phase stress) and the stress dependence on phase content of the coating constituents. Through-thickness residual stress profiles have been measured by neutron diffraction with spatial resolution of 0.5 mm for a series of Cu+W coatings with varying volume fractions. Measurements were made in both phases in order to separate micro- and macro-stresses. Comprehensive sample characterization, measurements of the residual stresses, mechanical and thermal properties of the composite coatings enabled quantitative modeling and interpretation of the experimental data.

Showing 1 to 10 of 57 Paper Titles