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Jens Gibmeier

Bio: Jens Gibmeier is an academic researcher from Karlsruhe Institute of Technology. The author has contributed to research in topics: Residual stress & Stress (mechanics). The author has an hindex of 17, co-authored 134 publications receiving 1457 citations. Previous affiliations of Jens Gibmeier include Applied Materials & Helmholtz-Zentrum Berlin.


Papers
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Journal ArticleDOI
TL;DR: In this paper, laser surface texturing was applied to texture the rake face of the cutting tool with different textures (dimples and channels) to allow for changing the adhesion tendency of built-up edge (BUE) structures.

210 citations

Journal ArticleDOI
TL;DR: The EDDI beamline is especially suitable for the investigation of structural properties and gradients in the near surface region of polycrystalline materials in particular, this concerns the analysis of multiaxial residual stress fields in the highly stressed surface zone of technical parts as discussed by the authors.
Abstract: In April 2005 the materials science beamline EDDI (Energy Dispersive DIffraction) at the Berlin synchrotron storage ring BESSY started operation. The beamline is operated in the energy-dispersive mode of diffraction using the high energy white photon beam provided by a superconducting 7 T multipole wiggler. Starting from basic information on the beamline set-up, its measuring facilities and data processing concept, the wide range of applications for energy-dispersive diffraction is demonstrated by a series of examples coming from different fields in materials sciences. It will be shown, that the EDDI beamline is especially suitable for the investigation of structural properties and gradients in the near surface region of polycrystalline materials. In particular, this concerns the analysis of multiaxial residual stress fields in the highly stressed surface zone of technical parts. The high photon flux further facilitates fast in situ experiments at room as well as high temperature to monitor for example the growth kinetics and reaction in thin film growth. r 2007 Elsevier B.V. All rights reserved.

206 citations

Journal ArticleDOI
TL;DR: In this paper, the porosity distribution and morphology of laser melted rotation bending test samples before and after shot peening were investigated by means of micro-tomography analysis, which showed that porosity shrinkage could be achieved in near-surface areas (0-500μm), but also in depths that did not seem accessible via shot-peening, leading to an overall relative porosity reduction between 15-30%.
Abstract: This paper investigates the porosity distribution and morphology of selective laser melted rotation bending test samples before and after shot peening by means of micro-tomography analysis. The as-built samples show porosity clusters close to the surface, which are attributed to the contour-core scan strategy. In the following steps the effect of shot peening on pore size and morphology in dependency of depth was examined. A strong porosity shrinkage could be achieved in near-surface areas (0–500 μm), but also in depths that did not seem accessible via shot peening, leading to an overall relative porosity reduction between 15–30%. Furthermore, shot peening led to a pore sphericity increase, especially for large pores. The individual orientation of the pores were compared before and after shot peening, where the former mostly had their longest axis in surface normal direction, while the latter showed a more randomly orientation distribution. X-ray diffractography detected residual compressive stresses for the as-built as well as the shot peened samples. Finally fatigue tests were performed, indicating an increase in low- and high-cycle-fatigue resistance after shot peening by 20 MPa.

96 citations

Journal ArticleDOI
01 Feb 2014-EPL
TL;DR: In this paper, a new concept for x-ray computed tomography that yields information about the local micro-morphology and its orientation in each voxel of the reconstructed 3D tomogram is introduced.
Abstract: Here we introduce a new concept for x-ray computed tomography that yields information about the local micro-morphology and its orientation in each voxel of the reconstructed 3D tomogram. Contrary to conventional x-ray CT, which only reconstructs a single scalar value for each point in the 3D image, our approach provides a full scattering tensor with multiple independent structural parameters in each volume element. In the application example shown in this study, we highlight that our method can visualize sub-pixel fiber orientations in a carbon composite sample, hence demonstrating its value for non-destructive testing applications. Moreover, as the method is based on the use of a conventional x-ray tube, we believe that it will also have a great impact in the wider range of material science investigations and in future medical diagnostics.

88 citations

Journal ArticleDOI
TL;DR: In this article, a powder based on the chemical composition of IN 718 was cold-sprayed on IN718 substrates by using nitrogen gas for an application as a repair tool for aero engine components.
Abstract: In the cold spray process, deposition of particles takes place through intensive plastic deformation upon impact in a solid state at the temperatures well below their melting point. The high particle impact velocity causes high local stresses which lead to deforming the particles and the substrate plastically in the proximity of the particle–substrate interface. As a result, high residual stresses are introduced in cold spray coatings due to the peening effect of the particles collisions with the substrate. In this study, a powder based on the chemical composition of IN 718 was cold-sprayed on IN 718 substrates by using nitrogen gas for an application as a repair tool for aero engine components. The magnitude of the residual stress and its distribution through the thickness were measured by using the hole-drilling and the bending methods. Residual stress was also estimated by using an approach based on the physical process parameters. Mainly compressive residual stresses were observed in cold-sprayed IN 718 coatings. Accumulation of residual stresses in the coatings is highly affected by peening during deposition and it decreases with increase in thickness. It has been observed that the adhesion-strengths of cold-sprayed IN 718 coatings are highly influenced by coating thickness and residual stress states of the coating/substrate system. In the presence of residual stresses in the coatings, adhesion-strength decreases with increasing coating thickness. The energy-release-rate criterion has been used to predict adhesion-strength with increasing coating thickness. Predicted bond-strength values are close to the measured adhesion-strength values and decrease with increase in coating thickness.

70 citations


Cited by
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01 Jun 2005

3,154 citations

Journal ArticleDOI
TL;DR: A comprehensive understanding of the interrelation between the various aspects of the subject, as this is essential to demonstrate credibility for industrial needs, is presented in this paper, which highlights some key topics requiring attention for further progression.

761 citations

01 Jan 1985

626 citations

Journal ArticleDOI
TL;DR: In this article, the origins of residual stress are understood, opportunities for removing harmful or introducing beneficial residual stresses recognized, their evolution in-service predicted, their influence on failure processes understood and safe structural integrity assessments made, so as to either remove the part prior to failure, or to take corrective action to extend life.
Abstract: Our safety, comfort and peace of mind are heavily dependent upon our capability to prevent, predict or postpone the failure of components and structures on the basis of sound physical principles While the external loadings acting on a material or component are clearly important, There are other contributory factors including unfavourable materials microstructure, pre-existing defects and residual stresses Residual stresses can add to, or subtract from, the applied stresses and so when unexpected failure occurs it is often because residual stresses have combined critically with the applied stresses, or because together with the presence of undetected defects they have dangerously lowered the applied stress at which failure will occur Consequently it is important that the origins of residual stress are understood, opportunities for removing harmful or introducing beneficial residual stresses recognized, their evolution in-service predicted, their influence on failure processes understood and safe structural integrity assessments made, so as to either remove the part prior to failure, or to take corrective action to extend life This paper reviews the progress in these aspects in the light of the basic failure mechanisms

595 citations