Papers by Author: Thilo Pirling

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Authors: Hadi Moztarzadeh, Darren J. Hughes, Sampan Seth, Elspeth Keating, Ercihan Kiraci, Gregory J. Gibbons, Thilo Pirling, Richard J. Dashwood
Abstract: Neutron diffraction and curvature measurements were conducted to investigate the residual stresses associated with Plasma Transferred Arc Cladding (PTA) of Ti-6Al-4V on a substrate of the same material. The wire-feed PTA coupled with 3-axis CNC machine was used as an Additive Manufacturing (AM) technique to build parts. A combination of the process parameters was chosen to investigate their effects on residual stress evolution. Neutron Diffraction (ND) measurements of residual strains were performed on the SALSA instrument at the Institut Laue-Langevin (ILL), Grenoble, France. Longitudinal stresses were also inferred by using a Coordinate Measurement Machine (CMM) and Euler-Bernoulli beam theorem. Furthermore, Optical Microscopy (OM) of the cross section of the parts was used to analyse the microstructural evolution. The results show the effect of shorter and longer ‘dwell time’ between layers on the evolution of residual stresses.
Authors: G. Albertini, G. Caglioti, F. Fiori, Thilo Pirling, V. Stanic, J.S. Wright
Authors: Giovanni Bruno, Adele Carradò, B. Dunn, F. Fiori, E. Girardin, Thilo Pirling, F. Rustichelli
Authors: Jeremy Epp, Thilo Pirling, Thomas Hirsch
Abstract: In this paper the microstructural and residual-stress analysis of an induction hardened plate of medium carbon steel is described. The stress gradient was determined using laboratory X-ray diffraction (IWT, Bremen, Germany) and neutron strain scanning (ILL, Grenoble, France). Due to slight variations of chemical composition in the depth, matchstick like (cross section 2×2mm²) d0-reference samples were prepared from a similarly treated sample. The d0 shift induced by variation of chemical composition was measured by neutron and by X-ray diffraction along the strain free direction (sin²ψ*) and used for the evaluation of the neutron stress calculation. The d0 distribution obtained from the neutron measurement did not appear reliable while the method using X-ray diffraction seems to be an efficient and reliable method to determine d0 profiles in small samples. The evaluation of neutron measurements was then done using the X-ray diffraction d0 distribution. High compressive residual stresses were measured in the hardened layer followed by high tensile residual stresses in the core. A comparison of the neutron measurements with X-ray diffraction (XRD) depth profiles obtained after successive layer removal showed that both methods give similar results. However, these investigations opened the question about the direct comparison of the residual stresses obtained by neutron and XRD. Indeed, a correction of the neutron data regarding the residual stresses in thickness direction might be necessary as these are released in the case of X-ray diffraction measurements after layer removal.
Authors: Thilo Pirling, Darren J. Hughes, Jeremy S. Robinson
Abstract: Experimental errors in neutron residual strain imaging are often underestimated, mis-understood or simply ignored. The choice of beam defining optics can play a large role in the magnitude of these errors. In this paper we show that the use of a traditional slit beam defining system with large specimens can lead to several sources of errors. Large specimens usually require necessarily large distances between the slits and the instrument reference point (gauge volume). At large distances, the slit system can lead to significant underestimation of the residual strain magnitude as well as poor definition of the gauge volume. We show that for large specimens, the use of radial focussing collimators reduces these effects, leading to significant improvement in measurement reliability. Specifically, we show application of radial collimators at the SALSA instrument of the Institut Laue Langevin neutron source in Grenoble, France.
Authors: Jeremy S. Robinson, Christopher E. Truman, Thilo Pirling, Tobias Panzner
Abstract: The residual stresses in heat treated 7075 aluminium alloy blocks have been characterised using two neutron diffraction strain scanning instruments. The influence of uniaxial cold compression (1-10%) on relieving the residual stress has been determined. Increasing the magnitude of cold compression from 1 to 10% has been shown to have a beneficial effect on the residual stress distribution by reducing the range between the maximum and minimum residual stresses. The effect of over aging 7075 on residual stress has also been characterised using neutron diffraction and this was found to reduce the residual stress by 25-40%. A relationship between {311} peaks widths and amount of cold compression was also observed.
Authors: Thilo Pirling, Giovanni Bruno, Philip J. Withers
Abstract: SALSA (Strain Analyser for Large Scale engineering Applications) is a novel instrument for strain imaging at the high flux neutron reactor of the Institut Max von Laue – Paul Langevin (ILL) in Grenoble, France. It is the first of its kind that uses a precise robotic sample stage for sample manipulation. In addition to standard xyz-translation it provides tilts up to ±30° about any horizontal axis. Its load capacity is more than 500 kg and samples up to 1.5 m in length can be scanned with high accuracy. Thanks to a double focusing monochromator and supermirror guide count times are very short. A broad wavelength range, variable beam optics, including radial focusing collimators for high lateral resolution, make it a very flexible instrument for a large variety of strain imaging applications in small and large specimens. The instrument has been commissioned in 2005 and is open for access by a peer review proposal system and as well by industry. The paper describes the important aspects of the instrument and results from the first experiments.
Authors: B. Malard, Thilo Pirling, Karim Inal, Etienne Patoor, Sophie Berveiller
Abstract: This paper focuses on the study of the superelastic behavior associated to the stress induced martensite transformation in a Cu-12.5%Al-0.5%Be [wt. %] shape memory alloy. Neutron diffraction was used to track the evolution of stress in the (β1) austenitic phase during the onset of the stress-induced martensite phase change. A thin flat and a cylindrical specimen was analyzed, allowing us firstly to evaluate the stress evolution in the austenite phase during martensitic transformation with laboratory X-ray and neutron diffraction and secondly to compare differences between methods (sin2ψ, principal stress) for in-situ neutron diffraction experiments.
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