The Experts below are selected from a list of 48303 Experts worldwide ranked by ideXlab platform
Wolfang G Bessler - One of the best experts on this subject based on the ideXlab platform.
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a multi timescale modeling methodology for pemfc performance and Durability in a virtual fuel cell car
International Journal of Hydrogen Energy, 2015Co-Authors: Manik Mayur, Stephan Strahl, Attila Husar, Wolfang G BesslerAbstract:Abstract The Durability of polymer electrolyte membrane fuel cells (PEMFC) is governed by a nonlinear coupling between system demand, component behavior, and physicochemical degradation mechanisms, occurring on timescales from the sub-second to the thousand-hour. We present a simulation methodology for assessing performance and Durability of a PEMFC under automotive driving cycles. The simulation framework consists of (a) a fuel cell car model converting velocity to cell power demand, (b) a 2D multiphysics cell model, (c) a flexible degradation library template that can accommodate physically-based component-wise degradation mechanisms, and (d) a time-upscaling methodology for extrapolating degradation during a representative load cycle to multiple cycles. The computational framework describes three different time scales, (1) sub-second timescale of electrochemistry, (2) minute-timescale of driving cycles, and (3) thousand-hour-timescale of cell ageing. We demonstrate an exemplary PEMFC Durability Analysis due to membrane degradation under a highly transient loading of the New European Driving Cycle (NEDC).
Pier Giorgio Malerba - One of the best experts on this subject based on the ideXlab platform.
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probabilistic service life assessment and maintenance planning of concrete structures
Journal of Structural Engineering-asce, 2006Co-Authors: Fabio Biondini, Dan M. Frangopol, Franco Bontempi, Pier Giorgio MalerbaAbstract:This paper presents a general approach to the probabilistic prediction of the structural service life and to the maintenance planning of deteriorating concrete structures. The proposed formulation is based on a novel methodology for the assessment of the time-variant structural performance under the diffusive attack of external aggressive agents. Based on this methodology, Monte Carlo simulation is used to account for the randomness of the main structural parameters, including material properties, geometrical parameters, area and location of the reinforcement, material diffusivity and damage rates. The time-variant reliability is then computed with respect to proper measures of structural performance. The results of the lifetime Durability Analysis are finally used to select, among different maintenance scenarios, the most economical rehabilitation strategy leading to a prescribed target value of the structural service life. Two numerical applications, a box-girder bridge deck and a pier of an existing bridge, show the effectiveness of the proposed methodology.
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cellular automata approach to Durability Analysis of concrete structures in aggressive environments
Journal of Structural Engineering-asce, 2004Co-Authors: Fabio Biondini, Dan M. Frangopol, Franco Bontempi, Pier Giorgio MalerbaAbstract:This paper presents a novel approach to the problem of Durability Analysis and lifetime assessment of concrete structures under the diffusive attack from external aggressive agents. The proposed formulation mainly refers to beams and frames, but it can be easily extended also to other types of structures. The diffusion process is modeled by using cellular automata. The mechanical damage coupled to diffusion is evaluated by introducing suitable material degradation laws. Since the rate of mass diffusion usually depends on the stress state, the interaction between the diffusion process and the mechanical behavior of the damaged structure is also taken into account by a proper modeling of the stochastic effects in the mass transfer. To this aim, the nonlinear structural analyses during time are performed within the framework of the finite element method by means of a deteriorating reinforced concrete beam element. The effectiveness of the proposed methodology in handling complex geometrical and mechanical boundary conditions is demonstrated through some applications. Firstly, a reinforced concrete box girder cross section is considered and the damaging process is described by the corresponding evolution of both bending moment–curvature diagrams and axial force-bending moment resistance domains. Secondly, the Durability Analysis of a reinforced concrete continuous T-beam is developed. Finally, the proposed approach is applied to the Analysis of an existing arch bridge and to the identification of its critical members.
Manik Mayur - One of the best experts on this subject based on the ideXlab platform.
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a multi timescale modeling methodology for pemfc performance and Durability in a virtual fuel cell car
International Journal of Hydrogen Energy, 2015Co-Authors: Manik Mayur, Stephan Strahl, Attila Husar, Wolfang G BesslerAbstract:Abstract The Durability of polymer electrolyte membrane fuel cells (PEMFC) is governed by a nonlinear coupling between system demand, component behavior, and physicochemical degradation mechanisms, occurring on timescales from the sub-second to the thousand-hour. We present a simulation methodology for assessing performance and Durability of a PEMFC under automotive driving cycles. The simulation framework consists of (a) a fuel cell car model converting velocity to cell power demand, (b) a 2D multiphysics cell model, (c) a flexible degradation library template that can accommodate physically-based component-wise degradation mechanisms, and (d) a time-upscaling methodology for extrapolating degradation during a representative load cycle to multiple cycles. The computational framework describes three different time scales, (1) sub-second timescale of electrochemistry, (2) minute-timescale of driving cycles, and (3) thousand-hour-timescale of cell ageing. We demonstrate an exemplary PEMFC Durability Analysis due to membrane degradation under a highly transient loading of the New European Driving Cycle (NEDC).
S Murugan - One of the best experts on this subject based on the ideXlab platform.
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Durability Analysis of a single cylinder di diesel engine operating with a non petroleum fuel
Fuel, 2017Co-Authors: Abhishek Sharma, S MuruganAbstract:Abstract Tyre pyrolysis oil (TPO) derived from pyrolysis of scrap tyres has been proven as a source of heat energy. Earlier investigations indicated that, a blend (JMETPO20) comprising of 20% TPO and 80% Jatropha methyl ester (JME) was found to be the optimum blend, when tested in a diesel engine. A comparative study reported in this paper is aimed to examine the Durability issues of a direct injection diesel engine run on the JMETPO20 blend and diesel. For this purpose, the engine operated with the JMETPO20 blend and diesel was run for 100 h, which consist of 14 test cycles of 7 h each as per the IS 10000 standards. Visual examination of the vital parts of the engine components such as cylinder head, piston crown, and nozzle injector tip, etc. was also carried out to find the carbon deposit after the Durability test. After the Durability test, several tribological characteristics of the used lubricating oil were evaluated after every 25 h of engine operation in order to analyze the consequence of fuel chemistry on the life of the lubricating oil. Measurement of different metal debris concentrations present in the lubricating oil samples drawn from the JMETPO20 blend and diesel operated engine was carried out by the atomic absorption spectroscopy.
Fabio Biondini - One of the best experts on this subject based on the ideXlab platform.
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probabilistic service life assessment and maintenance planning of concrete structures
Journal of Structural Engineering-asce, 2006Co-Authors: Fabio Biondini, Dan M. Frangopol, Franco Bontempi, Pier Giorgio MalerbaAbstract:This paper presents a general approach to the probabilistic prediction of the structural service life and to the maintenance planning of deteriorating concrete structures. The proposed formulation is based on a novel methodology for the assessment of the time-variant structural performance under the diffusive attack of external aggressive agents. Based on this methodology, Monte Carlo simulation is used to account for the randomness of the main structural parameters, including material properties, geometrical parameters, area and location of the reinforcement, material diffusivity and damage rates. The time-variant reliability is then computed with respect to proper measures of structural performance. The results of the lifetime Durability Analysis are finally used to select, among different maintenance scenarios, the most economical rehabilitation strategy leading to a prescribed target value of the structural service life. Two numerical applications, a box-girder bridge deck and a pier of an existing bridge, show the effectiveness of the proposed methodology.
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cellular automata approach to Durability Analysis of concrete structures in aggressive environments
Journal of Structural Engineering-asce, 2004Co-Authors: Fabio Biondini, Dan M. Frangopol, Franco Bontempi, Pier Giorgio MalerbaAbstract:This paper presents a novel approach to the problem of Durability Analysis and lifetime assessment of concrete structures under the diffusive attack from external aggressive agents. The proposed formulation mainly refers to beams and frames, but it can be easily extended also to other types of structures. The diffusion process is modeled by using cellular automata. The mechanical damage coupled to diffusion is evaluated by introducing suitable material degradation laws. Since the rate of mass diffusion usually depends on the stress state, the interaction between the diffusion process and the mechanical behavior of the damaged structure is also taken into account by a proper modeling of the stochastic effects in the mass transfer. To this aim, the nonlinear structural analyses during time are performed within the framework of the finite element method by means of a deteriorating reinforced concrete beam element. The effectiveness of the proposed methodology in handling complex geometrical and mechanical boundary conditions is demonstrated through some applications. Firstly, a reinforced concrete box girder cross section is considered and the damaging process is described by the corresponding evolution of both bending moment–curvature diagrams and axial force-bending moment resistance domains. Secondly, the Durability Analysis of a reinforced concrete continuous T-beam is developed. Finally, the proposed approach is applied to the Analysis of an existing arch bridge and to the identification of its critical members.
