To widely commercialize electric vehicles (EVs), more efforts to improve their life span seem profoundly inevitable. Thermal conditions have profound the nonlinear effects on the degradation rate, ...performance, and safety level of an EV battery pack. In the current study, both cycle life and calendar life of a commercial LiFePO
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-based cell are investigated experimentally via electrochemical impedance spectroscopy (EIS) for different operating temperatures. This is the first time that the effects of low temperatures such as − 20 °C and − 5 °C on the life of LiFePO
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-based cells are investigated via EIS, which is the crucial case during the cold start of EVs in cold climate regions of the world. The results show a considerable increase of solvent resistance for the cell which experienced calendar aging test at 55 °C; this demonstrates a drastic thickening of the SEI for this storage temperature. Moreover, anode cracking is clearly observed at such a high temperature. The results of the cycle aging tests also show that the increase in the solvent resistance is negligible for all other three operating temperatures. Nevertheless, the increasing of SEI thickness at low-temperature condition (− 5 °C) is noticeable. The role of temperature on the degradation level of LiFePO
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-based cells has also been discovered via scanning electron microscopy.
Obtaining the required surface finish and geometric accuracy, together with attaining a high production rate, is a challenge in finishing the inner surfaces of steel pipes and bushes. One of the ...promising techniques for the reduction of the surface roughness of metal parts is electrochemical machining. In this paper, the roughness and dimensional inaccuracy of the internal surface of a CK45 steel bush were controlled electrochemically. For this, a novel electrochemical finishing setup was constructed. The effect of electric potential difference along with temperature, flow rate, and concentration of electrolyte on the process outputs, including the material removal rate, surface roughness, and dimensional accuracy, were investigated. The Box-Behnken Design was utilized to design the empirical experiments. Analysis of variance was performed to validate the experimental models. Also, multi-objective optimization was implemented using response surface methodology to achieve a predetermined level of surface roughness and dimensional accuracy, along with maximizing the material removal rate.
This paper attempts to optimize welding parameters. The strength and quality of FSWed (Friction Stir Welding) sections are affected by materials transfer, work hardening, and transformations. These ...properties depend strongly on materials transfer, which is under the control of welding parameters. The soundness of friction stir welded sections is usually studied by Non Destructive Test (NDT) techniques. However, it could be characterized by physical properties such as electrical conductivity. The higher electrical conductivity implies less defects and higher welding quality. For this purpose, the Taguchi Lq orthogonal design of experiment was used to optimize the welding parameters. The optimum process parameters and their effectiveness in the electrical conductivity of welded sections were analyzed by Signal-to-Noise (S/N) ratio and Analysis Of Variance (ANOVA) tests. The results indicated that the tilt angle and tool shape were the most influential parameters to catch the maximum conductivity in welded joints. The optimum tool shape and tilt angle were cylindrical and 3°, respectively. The optimum conditions for welding and rotational speeds were characterized by 100 mm/min and 900 rpm in the stir zone, 250 mm/min and 900 rpm in Advancing Side (AS), and 100 mm/min and 450 rpm in Retreating Side (RS), respectively.
To widely commercialize electric vehicles more efforts for their life improvement seem extremely inevitable. Thermal conditions can have profound and nonlinear effects on the degradation rate of an ...electric vehicle battery pack as well as its performance and safety level. In the current study, both cycle life and calendar life of a commercial LiFePO
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cell are investigated experimentally by means of capacity fading and resistance increment evaluation for 4 different thermal conditions from extremely cold condition of − 20 °C—which is not well studied in the literature—till hot condition of 55 °C. The calendar life tests show that the best condition for storing cells is at 5 °C and 50% SOC and the cycle life tests demonstrate that the best operating temperature is 25 °C based on the dynamic stress test discharge/charge profile (a test profile for electric vehicles). It is also found that the capacity fading and resistance increment at a high temperature such as 50 °C are destructively significant. The presented curves in this paper can also serve as an aging data source for further work on battery lifetime modeling and diagnostics. The role of temperature on the degradation level is also discovered via scanning electron microscopy.
SIM-Lite is an astrometric interferometer being designed for sub-microarcsecond astrometry, with a wide range of applications from searches for Earth-analogs to determining the distribution of dark ...matter. SIM-Lite measurements can be limited by random and systematic errors, as well as astrophysical noise. In this paper we focus on instrument systematic errors and report results from SIM-Lite’s interferometer testbed. We find that, for narrow-angle astrometry such as used for planet finding, the end-of-mission noise floor for SIM-Lite is below 0.035 μas.
The SIM-Lite mission has finished its technology programme and continues with an engineering risk reduction activity while waiting for the results of the 2010 decadal review. One of the last ...remaining activities is work on the SCDU testbed, which is designed to calibrate the spectral bias in interferometric astrometry to 0.1 microarcsec. This talk will provide a summary of engineering activities on building flight-like prototypes of the key interferometer subassemblies, as well as an overview of the types of problems one encounters when attempting to do astrometry below 1 microarcsec, as well as their solution.
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