Untersuchungen zur Betriebsfestigkeit schiffbaulicher Schweisskonstruktionen bei verschiedenen Randombelastungen. Anlagen Abschlussbericht

The wave-induced strains of the shipp's hull structural elements are interrupted during the lay time in the port. During loading and unloading the smooth water strains are varying. These variations of strains influence the fatigue life of structural elements. So welded cruciform specimens made of steel D 36 have been investigated unter unchanged random loading, random loading with static loads, random loading with static loads and single peak loads and random loading with alternating static loads. The experimental results are compared with the calculated fatigue life to the nominal strain concept and the local strain concept. For the calculation of the stress concentration factor the FE-programme ANSYS has been applied. Also single edge cracks made of steel D 36 have been investigated under the above mentioned loadings. The experimental results are compared with the calculated crack lengths according to the linear and nonlinear concept. Connection of transverse bulkhead longitudinal stiffeners with one- side- and double connection have been investigated under static loads and random loading. The linear and nonlinear computation of stress distribution and the calculation of the concentration factor the FE-programme ANSYS has been applied. The experimental results under static loads show that the computation of the linear stress distribution can be predicted with sufficient accuracy. Results under random loading show that the crack initiation life is comparable with the calculated fatigue life according to the nominal strain concept and the local strain concept. The nonlinear calculated crack lengths are comparable with the experimental crack lengths for these complex structures. Final welded single edge cracks made of steel D 36 without and with natural stress have been investigated under the above-mentioned loadings. The experimental results are compared with the calculated crack lengths according to a nonlinear mixed mode concept. (orig.)SIGLEAvailable from TIB Hannover: F95B1016+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Life Cycle Design C 5.1. Einfluss der Druckmittelspannung auf die Betriebsfestigkeit Abschlussbericht

The wave-induced strains of the ship's hull structural elements are interrupted during the lay time in the port. During loading and unloading the smooth water strains are varying. These variations of strains induce in certain ship's hull structural elements tension or compressive mean stress. While the influence of tension mean stress on fatigue strength is well researched, the knowledge of the influence of compressive mean stress on fatigue strength has to be completed. Expected is a favourable influence of compressive mean stress, which until now is not or not sufficient considered in the classification rules. So welded cruciform specimen with K-joints made of steel St E 355 have been investigated under - unchanged random loading, - random loading with tension and compressive mean stress, - random loading with tension and compressive mean stress and single peak loads by experiments and by calculation. During the experiments the number of life cycles until complete crack of specimens were counted and the krack growth was measured by registrating the variations of a potential of direct current, which was laid on each specimen by means of probes. The experimental results have been compared with the calculated fatigue life according to the nominal strain concept, to the effective notch concept and to the crack propagation concept. For the calculation of the stress distribution of the specimens and of the notches the FE-programm ANSYS has been applied. The experimental results show the expected influence of tension and compressive mean stress and of single peak loads on fatigue life, whereas the results of the calculation according to the above mentioned concepts only correspond to experimental results for tension mean stress and mean stress 'zero' including single peak loads. For random loading with compressive mean stress and single peak loads with tension the application of the mean stress concept and the effective notch concept give useful but very conservative results. Only the results of application of the crack propagation concept with linear statements of damage show a sufficient agreement in the test results for random loading with compressive mean stress and single peak loads with tension. (orig.)Available from TIB Hannover: F99B252+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Untersuchungen zur Betriebsfestigkeit schiffbaulicher Schweisskonstruktionen bei verschiedenen Randombelastungen Abschlussbericht

The wave-induced strains of the ship's hull structural elements are interrupted during the lay time in the port. During loading and unloading the smooth water strains are varying. These variations of strains influence the fatigue life of structural elements. So welded cruciform specimens made of steel D 36 have been investigated under unchanged random loading, random loading with static loads, random loading with static loads and single peak loads and random loading with alternating static loads. The experimental results are compared with the calculated fatigue life to the nominal strain concept and the local strain concept. For the calculation of the stress concentration factor the FE-programm ANSYS has been applied. Also single edge cracks made of steel D 36 have been investigated under the above mentioned loadings. The experimental results are compared with the calculated crack lengths according to the linear and nonlinear concept. Connection of transverse bulkhead longitudinal stiffeners with one- side- and double connection have been investigated under static loads and random loading. The linear and nonlinear computation of stress distribution and the calculation of the concentration factor the FE-programm ANSYS has been applied. The experimental results under static loads show that the computation of the linear stress distribution can be predicted with sufficient accuracy. Results under random loading show that the crack initiation life is comparable with the calculated fatigue life according to the nominal strain concept and the local strain concept. The nonlinear calculated crack lengths are comparable with the experimental crack lengths for these complex structures. Final welded single edge cracks made of steel D 36 without and with natural stress have been investigated under the above-mentioned loadings. The experimental results are compared with the calculated crack lengths according to a nonlinear mixed mode concept. (orig.)SIGLEAvailable from TIB Hannover: F95B1015+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Developments towards in-gas-jet laser spectroscopy studies of actinium isotopes at LISOL

To study exotic nuclides at the borders of stability with laser ionization and spectroscopy techniques, highest efficiencies in combination with a high spectral resolution are required. These usually opposing requirements are reconciled by applying the in-gas-laser ionization and spectroscopy (IGLIS) technique in the supersonic gas jet produced by a de Laval nozzle installed at the exit of the stopping gas cell. Carrying out laser ionization in the low-temperature and low density supersonic gas jet eliminates pressure broadening, which will significantly improve the spectral resolution. This article presents the required modifications at the Leuven Isotope Separator On-Line (LISOL) facility that are needed for the first on-line studies of in-gas-jet laser spectroscopy. Different geometries for the gas outlet and extraction ion guides have been tested for their performance regarding the acceptance of laser ionized species as well as for their differential pumping capacities. The specifications and performance of the temporarily installed high repetition rate laser system, including a narrow bandwidth injection-locked Ti:sapphire laser, are discussed and first preliminary results on neutron-deficient actinium isotopes are presented indicating the high capability of this novel technique.publisher: Elsevier articletitle: Developments towards in-gas-jet laser spectroscopy studies of actinium isotopes at LISOL journaltitle: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms articlelink: http://dx.doi.org/10.1016/j.nimb.2015.12.014 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved.status: publishe

In-gas-jet spectroscopy of actinium isotopes

International audienc

Towards high-resolution laser ionization spectroscopy of the heaviest elements in supersonic gas jet expansion

Resonant laser ionization and spectroscopy are widely used techniques at radioactive ion beam facilities to produce pure beams of exotic nuclei and measure the shape, size, spin and electromagnetic multipole moments of these nuclei. However, in such measurements it is difficult to combine a high efficiency with a high spectral resolution. Here we demonstrate the on-line application of atomic laser ionization spectroscopy in a supersonic gas jet, a technique suited for high-precision studies of the ground- and isomeric-state properties of nuclei located at the extremes of stability. The technique is characterized in a measurement on actinium isotopes around the N=126 neutron shell closure. A significant improvement in the spectral resolution by more than one order of magnitude is achieved in these experiments without loss in efficiency.status: publishe

Developments towards in-gas-jet laser spectroscopy studies of actinium isotopes at LISOL

International audienceTo study exotic nuclides at the borders of stability with laser ionization and spectroscopy techniques, highest efficiencies in combination with a high spectral resolution are required. These usually opposing requirements are reconciled by applying the in-gas-laser ionization and spectroscopy (IGLIS) technique in the supersonic gas jet produced by a de Laval nozzle installed at the exit of the stopping gas cell. Carrying out laser ionization in the low-temperature and low density supersonic gas jet eliminates pressure broadening, which will significantly improve the spectral resolution. This article presents the required modifications at the Leuven Isotope Separator On-Line (LISOL) facility that are needed for the first on-line studies of in-gas-jet laser spectroscopy. Different geometries for the gas outlet and extraction ion guides have been tested for their performance regarding the acceptance of laser ionized species as well as for their differential pumping capacities. The specifications and performance of the temporarily installed high repetition rate laser system, including a narrow bandwidth injection-locked Ti:sapphire laser, are discussed and first preliminary results on neutron-deficient actinium isotopes are presented indicating the high capability of this novel technique