Robert C. Wimpory

Helmholtz-Zentrum Berlin für Materialien und Energie

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Carsten Ohms

Joint Research Centre

M. Hofmann

Heinz Maier-Leibnitz Zentrum

Kamran Nikbin

Imperial College London

Mirko Boin

Helmholtz-Zentrum Berlin für Materialien und Energie

Catrin M. Davies

Imperial College London

Noel P. O’Dowd

University of Limerick

C. E. Truman

University of Bristol

Joana Rebelo-Kornmeier

Heinz Maier-Leibnitz Zentrum

A.G. Youtsos

National Centre of Scientific Research "Demokritos"

Thilo Pirling

Institut Laue-Langevin

Cooperative Institutions

John Wiley & Sons (Germany)

Helmholtz-Zentrum Berlin für Materialien und Energie

Max-Planck-Institut für Nachhaltige Materialien

VDEh-Betriebsforschungsinstitut

Jernkontoret (Sweden)

Federal Institute For Materials Research and Testing

Salzgitter Group (Germany)

Chinese Society for Electrical Engineering

Imperial College London

Centre National de la Recherche Scientifique

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Evaluation of residual stress assessment methods using a repair weld benchmark

The Journal of Strain Analysis for Engineering Design (2010)

L.K. Keppas Robert C. Wimpory D.E. Katsareas N.K. Anifantis A.G. Youtsos

A simple design of a letterbox-type repair weld on a plate is evaluated as a benchmark problem. Residual stresses are recorded using the non-destructive neutron diffraction technique and compared with predictions by full three-dimensional finite element modelling. The comparison is performed over a number of path lines in an attempt to evaluate both methods as potential residual stress assessment tools, for weld repairs. The proposed finite element methodology is based on uncoupled quasi-static thermoelasticity and incorporates the element activation–deactivation technique for simulating weld deposition. Sensitivity analysis indicates that the effect of heat loss due to radiation on predicted residual stresses is negligible, whereas incorporation of full annealing into the model is recommended. The diffractometer used, is STRESS-SPEC, located at the FRMII research reactor (Munich, Germany) and comprises a highly flexible monochromator arrangement and a two-dimensional position-sensitive 3 He detector. The success of the repair weld benchmark design is illustrated by not only the satisfactory correlation between experimental and computational results in the form of residual stress but also temperature history data.

Monochromator

Benchmark (surveying)

Diffractometer

10.1243/03093247jsa558

Cite

Citations (1)

Measurement and simulation of temperature and residual stress distributions from friction stir welding AA2024 Al alloy

Materials at High Temperatures (2010)

Li-Pen Wang Carys Davies Robert C. Wimpory L.Y. Xie Kamran Nikbin

AbstractAbstractFinite element (FE) models have been developed to predict residual stress distributions resulting from the friction stir welding (FSW) process. Plates 250 mm × 50 mm × 5 mm in dimension of an Aluminium alloy (AA2024-T4) were butt-joined through FSW. The thermal profiles were monitored in-situ during the welding process using thermocouples. Sequentially-coupled thermo-mechanical simulations have been performed using an instantaneous relative linear velocity based heat source. Post weld residual stress measurements have been obtained using the neutron diffraction technique and were used to verify the finite element results. The thermal profiles measured during welding have been simulated in the FE model. Increasing the tool traversal speed is found to reduce the peak temperatures experienced during welding for a given tool rotational speed. The general trends and magnitudes of the residual stress distributions measured along the weld line have been predicted by the FE model. The residual stress distributions measured and predicted are relatively symmetric and uninfluenced by the range of tool traversal speeds for the cases considered. Further refinement of the material and process model may be required to improve the predictions accuracy. However, effective predictions have been obtained in the FE model presented by treating the material as a continuum without additional complexities.Keywords: AA2024 Al alloyresidual stressfriction stir welding

Friction Stir Welding

10.1179/096034010x12813743510192

Cite

Citations (0)

Residual Stresses in Welded Steels with Longitudinal Stiffeners Determined by Neutron and X-Ray Diffraction

International Journal of Offshore and Polar Engineering (2014)

Jonas Hensel Thomas Nitschke‐Pagel Klaus Dilger Robert C. Wimpory

Source

Cite

Citations (0)

Stress Intensity Factors Due to Residual Stresses in T-Plate Welds

Journal of Pressure Vessel Technology (2004)

Noel P. O’Dowd Kamran Nikbin Hyeong Y. Lee Robert C. Wimpory Farid Reza Biglari

Residual stress distributions in ferritic steel T-plate weldments have been obtained using the neutron diffraction method. It is shown that the transverse residual stress distribution for two plates of different yield strength are of similar shape and magnitude when normalized appropriately and peak stresses are on the order of the material yield strength. The resultant linear elastic stress intensity factors for these stress distributions have been obtained using the finite element method. It has been shown that the use of the recommended residual stress distributions in UK structural integrity procedures leads to a conservative assessment. The stress intensity factors for the welded T-plate have been shown to be very similar to those obtained using a smooth edge cracked plate subjected to the same local stress field.

Intensity

Stress field

10.1115/1.1804199

Cite

Citations (10)

Residual stress field determination in welds by means of X‐ray, synchrotron and neutron diffraction

Materialwissenschaft und Werkstofftechnik (2011)

Majid Farajian Th. Nitschke‐Pagel Robert C. Wimpory M. Hofmann M. Klaus

Abstract To what extent the welding residual stresses influence fatigue is still unclear and matter of debate. An important reason for this lack of clarity is that the exact determination of residual stress fields in welds is complicated which leads to conservative assumptions about these stresses in the fatigue design codes. The advances in the diffraction analysis of materials offer the opportunity for the full‐field residual strain mapping in welds albeit at the cost of time and technical complexity. In this work residual stress field determination in welded S1100QL specimens by means of the x‐ray, synchrotron and neutron diffraction techniques was undertaken. The results revealed that the maximum values of surface residual stresses are not as frequently assumed, as high as the yield strength in small scale specimens. At the weld toe which could serve as a fatigue crack initiation site, even lower residual stresses than the weld centreline could be present. The in‐depth measurements revealed that the effective part of the residual stress field which could be decisive for the fatigue failure initiation is concentrated at the surface of the weld.

10.1002/mawe.201100782

Cite

Citations (14)

Neutron diffraction stress determination in W-laminates for structural divertor applications

Nuclear Materials and Energy (2015)

R. Coppola Carsten Ohms J. Reiser M. Rieth Robert C. Wimpory

Neutron diffraction measurements have been carried out to develop a non-destructive experimental tool for characterizing the crystallographic structure and the internal stress field in W foil laminates for structural divertor applications in future fusion reactors. The model sample selected for this study had been prepared by brazing, at 1085 °C, 13 W foils with 12 Cu foils. A complete strain distribution measurement through the brazed multilayered specimen and determination of the corresponding stresses has been obtained, assuming zero stress in the through-thickness direction. The average stress determined from the technique across the specimen (over both 'phases' of W and Cu) is close to zero at −17 ± 32 MPa, in accordance with the expectations.

Brazing

Structural material

Stress field

10.1016/j.nme.2015.07.001

Cite

Citations (2)

Elasto-plastic deformation within diamond reinforced metals for thermal management

Diamond and Related Materials (2016)

M. Schöbel Patrik Dobroň Johannes Bernardi Robert C. Wimpory Kay André Weidenmann

Ductility (Earth science)

10.1016/j.diamond.2016.09.027

Cite

Citations (2)

Relaxation of residual stresses when extracting a specimen from a dissimilar metal electron beam welded plate

K. Abburi Venkata C. E. Truman D. J. Smith Robert C. Wimpory

Electron beam welding

Source

Cite

Citations (3)

Influence of low magnitude plastic strains on residual stress in 7075 aluminium alloy

Materials Science and Technology (2019)

J. S. Robinson Robert C. Wimpory

The effect of post quench delay on residual stress has been determined by subjecting four rectilinear blocks of quenched 7075, containing large residual stress magnitudes, to small (<1.0%) plastic strains applied by cold compression. One experiment kept the plastic strain the same in all samples (∼0.12%) by cold compressing simultaneously in one pressing. The second pressed the blocks separately to the same strain (∼0.45%). The post quench delays were <10, 60, 120 and 240 min. The residual stresses were characterised using neutron and X-ray diffraction. It was possible to detect the impact of the small plastic strains on all samples, but the diffraction measurement techniques could not conclusively isolate the influence of the post quench delay.

Strain (injury)

10.1080/02670836.2019.1625555

Cite

Citations (3)

Crystal quality boosts responsiveness of magnetic shape memory single crystals

Journal of Magnetism and Magnetic Materials (2008)

Katharina Rolfs A. Mecklenburg J.M. Guldbakke Robert C. Wimpory Annika Raatz

Tetragonal crystal system

Crystal (programming language)

10.1016/j.jmmm.2008.10.023

Cite

Citations (18)