Modeling the impact of paste additives and pellet geometry on paste utilization within lead acid batteries during low rate discharges

AbstractWhen designing a lead acid battery, there are many factors to consider in order to obtain the best compromise of cost, performance, and ease of manufacturability. We use a modeling approach to study some of the key factors which affect the amount of active material which can be utilized during a low rate discharge. We investigate the effects of pellet size, pellet geometry, disconnected grid mesh borders, and inert paste additives. Furthermore, we look at how the internal path length resistance within a pellet is dependent on those features. Our findings correlate well with earlier works, and help to explain some of the previously observed phenomenon. It is observed that utilization is indeed affected by pellet size, but small grid mesh sizes on the order of ∼4 mm edge lengths are necessary in order to realize a significant benefit. Utilization is presented as a function of pellet size, aspect ratio of the pellets, and the loading level of the inert additives in the pellets up to ten percent by volume

Single asperity friction in the wear regime

Abstract We used molecular dynamics simulation to investigate the friction of a single asperity against a rigid substrate, while generating debris. In the low wear regime (i.e., non-linear wear rate dependence on the contact stress, via atom-by-atom attrition), the frictional stress is linearly dependent on the normal stress, without any lubrication effect from the wear debris particles. Both the slope (friction coefficient) and friction at zero normal stress depend strongly on asperity-substrate adhesion. In the high wear regime (i.e., linear wear rate dependence on the contact stress, via plastic flow), the friction-normal stress curves deviate from a linear relation merging toward plastic flow of the single asperity which is independent of the interfacial adhesion. One can further link wear and friction by considering debris generation as chemical reaction, driven by both normal and frictional forces. The coupling between wear and friction can then be quantified by a thermodynamic efficiency of the debris generation. While the efficiency is less than 5% in the low wear regime, indicating poor mechanochemical coupling, it increases with normal stress toward 50% in the high wear regime

Tribological Behavior of New Martensitic Stainless Steels Using Scratch and Dry Wear Test

This paper focuses on the tribological characterization of new martensitic stainless steels by two different tribological methods (scratch and dry wear tests) and their comparison to the austenitic standard stainless steel AISI 316L. The scratch test allows obtaining critical loads, scratch friction coefficients, scratch hardness and specific scratch wear rate, and the dry wear test to quantify wear volumes. The damage has been studied by ex situ scanning electron microscopy. Wear resistance was related to the hardness and the microstructure of the studied materials, where martensitic stainless steels exhibit higher scratch wear resistance than the austenitic one, but higher hardness of the martensitic alloys did not give better scratch resistance when comparing with themselves. It has been proved it is possible to evaluate the scratch wear resistance of bulk stainless steels using scratch test. The austenitic material presented lower wear volume than the martensitic ones after the dry wear test due to phase transformation and the hardening during sliding.The authors would like to thank to BPI, Region Centre and Tours Plus for support of this research, and also to Aubert and Duval and UF1 for providing the materials of this study. This work is done under the project FUI 11 Mekinox. We also wish to appreciate the helpful advice from Aubert and Duval.Dalmau Borrás, A.; Rmili, W.; Joly, D.; Richard, C.; Igual Muñoz, AN. (2014). Tribological Behavior of New Martensitic Stainless Steels Using Scratch and Dry Wear Test. Tribology Letters. 56(3):517-529. doi:10.1007/s11249-014-0429-6S517529563Kwok, C.T., Lo, K.H., Cheng, F.T., Man, H.C.: Effect of processing conditions on the corrosion performance of laser surface-melted AISI 440C martensitic stainless steel. Surf. Coat. 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