The Experts below are selected from a list of 129435 Experts worldwide ranked by ideXlab platform
Patrick Ebermann - One of the best experts on this subject based on the ideXlab platform.
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irreversible degradation of nb3sn rutherford cables due to transverse compressive Stress at room temperature
Superconductor Science and Technology, 2018Co-Authors: Patrick Ebermann, Johannes Bernardi, J Fleiter, Friedrich Lackner, Florian Meuter, Magdalena Pieler, C Scheuerlein, Daniel Schoerling, Felix WolfAbstract:In the framework of the Future Circular Collider design study for a 100 TeV circular collider, 16 T superconducting bending magnets based on Nb3Sn technology are being developed. A pre-Stress on the conductor during magnet assembly at room temperature (RT) is needed to counteract the Lorentz forces during operation. The superconducting properties of the brittle Nb3Sn superconductor are strain sensitive and excessive pre-Stress leads to an irreversible degradation of the superconductor. In order to determine the level of acceptable pre-Stress during the magnet assembly process, reacted and impregnated Nb3Sn cables were exposed to increasing transverse compressive Stress up to a maximum Stress level of 200 MPa at RT. After each Stress Cycle, the critical current of the cable specimens were characterized at 4.3 K in the FRESCA cable test station. No significant critical current degradation was observed up to 150 MPa, followed by degradation less than 4% after a nominal Stress of 175 MPa. A dramatic permanent critical current degradation occurred after applying a nominal Stress of 200 MPa. A comprehensive post analysis consisting of non-destructive micro-tomography followed by microscopic characterization of metallographic cable cross sections was carried out after the critical current test to reveal cracks in the Nb3Sn sub-elements of the loaded specimen.
Jane Q Wang - One of the best experts on this subject based on the ideXlab platform.
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rolling sliding contact fatigue of surfaces with sinusoidal roughness
International Journal of Fatigue, 2016Co-Authors: Dong Zhu, Jiaxu Wang, Jane Q WangAbstract:Abstract Surfaces of mechanical components under combined rolling and sliding motions may be subjected to accelerated contact fatigue failure due to increased number of microscopic Stress Cycles and pressure peak heights caused by rough-surface asperity contacts. Available rolling contact fatigue (RCF) theories were developed mainly for rolling element bearings, for which the effect of sliding is usually insignificant. In various types of gears, however, considerable sliding exist in the critical tooth contact area below the pitch line, where excessive wear and severe pitting failures originate. Ignorance of sliding is most likely the reason why the conventional RCF models often overestimate gear fatigue life. This paper studies the effect of sliding motion on the contact fatigue life of surfaces with sinusoidal roughness that mimicks the topography from certain manufacturing processes. A set of simple equations for Stress Cycle counting is derived. Mixed elastohydrodynamic lubrication simulations are executed with the considerations of normal loading and frictional shear. Relative fatigue life evaluations based on a subsurface Stress analysis is conducted, taking into account the two sliding-induced mechanisms, which are the greatly increased number of Stress Cycles and the pressure peak heights due to surface interactions. Obtained results indicate that sliding leads to a significant reduction of contact fatigue life, and rough surface asperity contacts result in accelerated pitting failure that needs to be considered in life predictions for various mechanical components.
Felix Wolf - One of the best experts on this subject based on the ideXlab platform.
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irreversible degradation of nb3sn rutherford cables due to transverse compressive Stress at room temperature
Superconductor Science and Technology, 2018Co-Authors: Patrick Ebermann, Johannes Bernardi, J Fleiter, Friedrich Lackner, Florian Meuter, Magdalena Pieler, C Scheuerlein, Daniel Schoerling, Felix WolfAbstract:In the framework of the Future Circular Collider design study for a 100 TeV circular collider, 16 T superconducting bending magnets based on Nb3Sn technology are being developed. A pre-Stress on the conductor during magnet assembly at room temperature (RT) is needed to counteract the Lorentz forces during operation. The superconducting properties of the brittle Nb3Sn superconductor are strain sensitive and excessive pre-Stress leads to an irreversible degradation of the superconductor. In order to determine the level of acceptable pre-Stress during the magnet assembly process, reacted and impregnated Nb3Sn cables were exposed to increasing transverse compressive Stress up to a maximum Stress level of 200 MPa at RT. After each Stress Cycle, the critical current of the cable specimens were characterized at 4.3 K in the FRESCA cable test station. No significant critical current degradation was observed up to 150 MPa, followed by degradation less than 4% after a nominal Stress of 175 MPa. A dramatic permanent critical current degradation occurred after applying a nominal Stress of 200 MPa. A comprehensive post analysis consisting of non-destructive micro-tomography followed by microscopic characterization of metallographic cable cross sections was carried out after the critical current test to reveal cracks in the Nb3Sn sub-elements of the loaded specimen.
Mohammed M Ettouney - One of the best experts on this subject based on the ideXlab platform.
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probabilistic fatigue assessment of monitored railroad bridge components using long term response data in a reliability framework
Structural Health Monitoring-an International Journal, 2020Co-Authors: Katherine A Flanigan, Jerome P Lynch, Mohammed M EttouneyAbstract:Fatigue is a primary concern for railroad bridge owners because railroad bridges typically have high live load to dead load ratios and high Stress Cycle frequencies. However, existing inspection an...
Ze Xiang - One of the best experts on this subject based on the ideXlab platform.
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simulation study on fatigue behavior of wrap around weld at rib to floorbeam joint in a steel uhpc composite orthotropic bridge deck
Construction and Building Materials, 2021Co-Authors: Ze Xiang, Zhiwen ZhuAbstract:Abstract As an innovative cement-based material, the ultra-high performance concrete (UHPC) has been recently utilized to reinforce the orthotropic steel bridges. Based on an in-situ steel-UHPC composite orthotropic deck bridge, both the field testing and multi-scale finite element analysis modelling were conducted to investigate the fatigue behavior of wrap-around weld at rib-to-floorbeam (RF) joint, and factors influencing Stress were further studied to achieve an infinite fatigue life. It is found that a primary tensile Stress Cycle is jointly produced by the axle group of truck, while a small reversal compressive Cycle will be generated when the axle is directly located on the floorbeam. The Stress behavior of fatigue detail is extremely sensitive to the localized effect of axle loading instead of entire truck configuration. Since significant Stress concentration and high Stress gradient exist in the wrap-around weld, it is essential to utilize the hot-spot Stress approach rather than nominal Stress approach. The wrap-around weld presents an obvious out-of-plane bending deformation, which results from the torsion effect and Poisson’s effect. The Dong’s structural Stress reveals that the surface Stress is dominated by bending Stress. The application of bulkhead can greatly improve the fatigue performance of wrap-around weld. Both the large-scale rib and U-shaped rib are preferable, which are available to achieve an infinite fatigue life without extra fabrication procedure.