| 1. |
- Zhang, Shidong, et al.
(författare)
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Simple and complex polymer electrolyte fuel cell stack models : A comparison
- 2018. - 13
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Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. - 9781607685395 ; 86, s. 287-300
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Konferensbidrag (refereegranskat)abstract
- In this paper, two distinct polymer electrolyte fuel cell stack models are constructed: a detailed numerical model (DNM) employing a fine-scale computational mesh and a coarse-mesh approach based on a distributed resistance analogy (DRA) where diffusion terms in the transport equations are replaced by rate terms. Both methods are applied to a 5-cell, high-temperature polymer electrolyte fuel cell stack with an active area of 200 cm2 per cell. The polarization curve and local current density distributions from both the DRA and DNM are compared with experimental data, finding good agreement. Temperature, pressure, Nernst potential, and species distributions are also exhibited. The DNM displays details of fine-scale local extrema not captured by the DRA; however, the latter requires orders of magnitude less computer processor power and memory for execution. Both methods provide much finer-scale results than present experimental techniques.
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| 2. |
- Djebien, S., et al.
(författare)
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Strain Rate and Notch Radius Effects on Evaluating the Stress–Strain Relations Using the Stepwise Modeling Method
- 2024
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Ingår i: Journal of Dynamic Behavior of Materials. - : Springer. - 2199-7446 .- 2199-7454. ; 10, s. 26-39
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Tidskriftsartikel (refereegranskat)abstract
- Accurate computer simulations require the selection of suitable material models and precise prediction of their parameters. In the fields of impact engineering and plastic working, stress–strain relations that include the post-necking regime up to fracture are crucial for predicting the behavior correctly. However, obtaining suitable stress–strain relations after necking requires some form of correction and adjustment for stress and/or strain. This study applies a stepwise modeling method for post-necking characterization that only utilizes the local strain field obtained from tensile experiments to precisely measure stress–strain relations at high strain rates. The effects of the notch radius of specimens on stress–strain relations were examined to measure stress–strain relations with large strain near the stress triaxiality of 1/3. The study also discusses adequate resolution for precise stress–strain measurements. Subsequently, specimens with suitable notch radius were used to measure stress–strain relations of plate specimens of aluminum alloy 2024-T3 at high strain rates. The study also examined the effects of strain rate on the flow stress and fracture strain of aluminum alloy 2024-T3.
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