The Experts below are selected from a list of 4398 Experts worldwide ranked by ideXlab platform
J.r. Seume - One of the best experts on this subject based on the ideXlab platform.
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Thermo-mechanical stress in tubular solid oxide fuel cells: Part II - operating strategy for reduced probability of Fracture Failure
IET Renewable Power Generation, 2012Co-Authors: K. Fischer, J.r. SeumeAbstract:A spatially discretised thermo-electrochemical model is developed to calculate the temperature distribution in a tubular solid oxide fuel cell (SOFC). This is used in a mechanical model to compute the distribution of thermo-mechanical stress in the ceramic membrane-electrode assembly of the cell. The resulting risk of Fracture Failure is determined by means of Weibull analysis. Part I of this work covers the dynamic operating properties of the SOFC and the time scale of material creep in its ceramic components. This work, Part II, deals with the risk of Fracture Failure related to transient operating scenarios, discusses its dependency on the operating conditions and derives a low-risk operating strategy. Contrary to the common perception, thermal gradients are found to have little impact on thermo-mechanical stress in the studied SOFC. Failure-relevant stress levels arise merely due to thermal mismatch of the ceramic layers. Regarding the operating strategy, the dynamics of changes in operating conditions are of minor importance for the resulting risk of Failure, while operating strategies aiming at a constant mean cell temperature prove to be advantageous. The consideration of material creep is shown to be essential for a sound analysis of thermo-mechanical stress and risk of Fracture in the investigated SOFC.
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Thermo-mechanical stress in tubular solid oxide fuel cells: Part I - transient operating behaviour and the relevance of material creep
IET Renewable Power Generation, 2012Co-Authors: K. Fischer, J.r. SeumeAbstract:A spatially discretised thermo-electrochemical model is developed to calculate the temperature distribution in a tubular solid oxide fuel cell (SOFC). Model validation is accomplished based on the operating data from a demonstration plant. Using a mechanical model of the ceramic membrane-electrode assembly, the distribution of thermo-mechanical stress is calculated from the temperature profile. The resulting risk of Fracture Failure, being one of the crucial life-limiting factors of SOFC, is determined by means of Weibull analysis. The methodology and results are presented in two parts: Part I covers the dynamic operating properties of the SOFC and the time scale of material creep in its ceramic components. Part II deals with the risk of Fracture Failure related to transient operating scenarios, discusses its dependency on the operating conditions and derives a low-risk operating strategy. The dynamic operating behaviour is found to be dominated by the large thermal inertia of the solid cell components. An analysis of the creep relaxation indicates a significant relief of mechanical stress in the electrodes within a few hours of operation. This justifies a novel assumption regarding the stress-free state in the mechanical analysis of the fuel cell, which significantly increases the plausibility of the resulting risk of Fracture Failure.
K. Fischer - One of the best experts on this subject based on the ideXlab platform.
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Thermo-mechanical stress in tubular solid oxide fuel cells: Part II - operating strategy for reduced probability of Fracture Failure
IET Renewable Power Generation, 2012Co-Authors: K. Fischer, J.r. SeumeAbstract:A spatially discretised thermo-electrochemical model is developed to calculate the temperature distribution in a tubular solid oxide fuel cell (SOFC). This is used in a mechanical model to compute the distribution of thermo-mechanical stress in the ceramic membrane-electrode assembly of the cell. The resulting risk of Fracture Failure is determined by means of Weibull analysis. Part I of this work covers the dynamic operating properties of the SOFC and the time scale of material creep in its ceramic components. This work, Part II, deals with the risk of Fracture Failure related to transient operating scenarios, discusses its dependency on the operating conditions and derives a low-risk operating strategy. Contrary to the common perception, thermal gradients are found to have little impact on thermo-mechanical stress in the studied SOFC. Failure-relevant stress levels arise merely due to thermal mismatch of the ceramic layers. Regarding the operating strategy, the dynamics of changes in operating conditions are of minor importance for the resulting risk of Failure, while operating strategies aiming at a constant mean cell temperature prove to be advantageous. The consideration of material creep is shown to be essential for a sound analysis of thermo-mechanical stress and risk of Fracture in the investigated SOFC.
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Thermo-mechanical stress in tubular solid oxide fuel cells: Part I - transient operating behaviour and the relevance of material creep
IET Renewable Power Generation, 2012Co-Authors: K. Fischer, J.r. SeumeAbstract:A spatially discretised thermo-electrochemical model is developed to calculate the temperature distribution in a tubular solid oxide fuel cell (SOFC). Model validation is accomplished based on the operating data from a demonstration plant. Using a mechanical model of the ceramic membrane-electrode assembly, the distribution of thermo-mechanical stress is calculated from the temperature profile. The resulting risk of Fracture Failure, being one of the crucial life-limiting factors of SOFC, is determined by means of Weibull analysis. The methodology and results are presented in two parts: Part I covers the dynamic operating properties of the SOFC and the time scale of material creep in its ceramic components. Part II deals with the risk of Fracture Failure related to transient operating scenarios, discusses its dependency on the operating conditions and derives a low-risk operating strategy. The dynamic operating behaviour is found to be dominated by the large thermal inertia of the solid cell components. An analysis of the creep relaxation indicates a significant relief of mechanical stress in the electrodes within a few hours of operation. This justifies a novel assumption regarding the stress-free state in the mechanical analysis of the fuel cell, which significantly increases the plausibility of the resulting risk of Fracture Failure.
Karl Schulte - One of the best experts on this subject based on the ideXlab platform.
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Fracture, Failure and compression behaviour of a 3D interconnected carbon aerogel (Aerographite) epoxy composite
Composites Science and Technology, 2016Co-Authors: Swetha Chandrasekaran, Wilfried V. Liebig, Daria Smazna, Matthias Mecklenburg, Bodo Fiedler, Rainer Adelung, Karl SchulteAbstract:Aerographite (AG) is a mechanically robust, lightweight synthetic cellular material, which consists of a 3D interconnected network of tubular carbon [1]. The presence of open channels in AG aids to infiltrate them with polymer matrices, thereby yielding an electrical conducting and lightweight composite. Aerographite produced with densities in the range of 7-15 mg/cm3was infiltrated with a low viscous epoxy resin by means of vacuum infiltration technique. Detailed morphological and structural investigations on synthesized AG and AG/epoxy composite were performed by scanning electron microscopic techniques. The present study investigates the Fracture and Failure of AG/epoxy composites and its energy absorption capacity under compression. The composites displayed an extended plateau region when uni-axially compressed, which led to an increase in energy absorption of ~133% per unit volume for 1.5 wt% of AG, when compared to pure epoxy. Preliminary results on Fracture toughness showed an enhancement of ~19% in KICfor AG/epoxy composites with 0.45 wt% of AG. Observations of Fractured surfaces under scanning electron microscope gives evidence of pull-out of arms of AG tetrapod, interface and inter-graphite Failure as the dominating mechanism for the toughness improvement in these composites. These observations were consistent with the results obtained from photoelasticity experiments on a thin film AG/epoxy model composite.
Xu Yang - One of the best experts on this subject based on the ideXlab platform.
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Fracture Failure analysis of valve bolt in the gas transmission station
2016 IEEE International Conference on Mechatronics and Automation, 2016Co-Authors: Xu YangAbstract:Pipelines are important tools for transporting natural gas. With the increasing demand of natural gas, more and more long-distance pipelines are being constructed. Gas transmission stations are used for gas purification, mixture, pressure regulating, metering, and so on. In a gas transmission station, many valves need to be connected with pipelines, and bolts are frequently used in the connection between pipes or between pipes and valves. The Failure of a bolt is dangerous for the safe operation of gas transportation. The Failure of a bolt connection is very serious and dangerous for machinery or mechanical structures. In the natural gas pipeline connection, a bolt Failure may cause gas leakage and even gas explosion due to its flammability. Fracture Failure analysis of a valve bolt on a filter separator in a gas transmission station was carried out in this research. Effects of bolt pretightening force and fatigue load were simulated using finite element modeling. Macro and micro Fracture observations indicated that inclusions in the steel caused increased risk of screw fatigue Fracture. Furthermore, corrosion from the external environment accelerated the crack extension and eventually led to Fracture of bolt.
A. Kalaki - One of the best experts on this subject based on the ideXlab platform.
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Fracture Failure analysis of AISI 304L stainless steel shaft
Engineering Failure Analysis, 2020Co-Authors: Sh. Zangeneh, Mostafa Ketabchi, A. KalakiAbstract:Abstract Fracture Failure analysis of an agitator shaft in a large vessel is investigated in the present work. This analysis methodology focused on Fracture surface examination and finite element method (FEM) simulation using Abaqus software for stress analysis. The results show that the steel shaft failed due to inadequate fillet radius size and more importantly marking defects originated during machining on the shaft. In addition, after visual investigation of the Fracture surface, it is concluded that Fracture occurred due to torsional–bending fatigue during operation.
