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Technical Paper

Predicting the Battery Residual Usable Energy under Dynamic Conditions: a Novel Adaptive Method with Enhanced Performance

Electric vehicle (EV) is a worldwide researching focus due to its environmental friendliness, but the inaccurate Remaining Driving Range (RDR) estimation hinders the EVs' popularity, and an accurate determination of the battery Residual Usable Energy (RUE) is the key factor to obtain a precise RDR value. A common RUE estimation method is based on State-of-Charge (SOC) estimation, in which the RUE is proportionally related to the current SOC. However, the battery voltage varies significantly under real-world conditions, and the traditional method results in certain estimation errors. An adaptive RUE prediction method (AEP) is introduced in this paper, in which the dynamic voltage is predicted based on the future discharge profile and a battery model, while the RUE is then calculated by the predicted voltage and current sequences.
Technical Paper

Characterization of Metal Foil in Anisotropy Fracture Behavior with Dynamic Tests

Metal foil is a widely-used material in the automobile industry, which is not only the honeycomb barriers material, but also used as current collectors in Li-ion batteries. Plenty of studies proved that the mechanical property of the metal foil is quite different from that of the metal sheet because of the size effect on microscopic scale, as the metal foil shows a larger fracture stress and a lower ductility than the metal sheet. Meanwhile, the fracture behavior and accurate constitutive model of metal foil with the consideration of the strain rate effect are widely concerned in further studies of battery safety and the honeycomb. This paper conducted experiments on 8081-H18 aluminum foil, aiming to explore the quasi-static and dynamic tension testing method and the anisotropy mechanical behavior for the very thin foil. Two metal foil dog-bone specimens and 3 types of notched specimens are tested with a strain rate ranges from 2 × 10−4/s to 40/s and various stress states.
Technical Paper

Structural Designs for Electric Vehicle Battery Pack against Ground Impact

Ground impact caused by road debris can result in very severe fire accident of Electric Vehicles (EV). In order to study the ground impact accidents, a Finite Element model of the battery pack structure is carefully set up according to the practical designs of EVs. Based on this model, the sequence of the deformation process is studied, and the contribution of each component is clarified. Subsequently, four designs, including three enhanced shield plates and one enhanced housing box, are investigated. Results show that the BRAS (Blast Resistant Adaptive Sandwich) shield plate is the most effective structure to decrease the deformation of the battery cells. Compared with the baseline case, which adopts a 6.35-mm-thick aluminum sheet as the shield plate, the BRAS can reduce the shortening of cells by more than 50%. Another type of sandwich structure, the NavTruss, can also improve the safety of battery pack, but not as effectively as the BRAS.
Journal Article

Mechanical Behavior of Lithium-Ion Battery Component Materials and Error Sources Analysis for Test Results

As mechanical damage induced thermal runaway of lithium-ion batteries has become one of the research hotspots, it is quite crucial to understand the mechanical behavior of component materials of lithium battery. This study focuses on the mechanical performance of separators and electrodes under different loading conditions and the error sources analysis for test results. Uniaxial tensile tests were conducted under both quasi-static and dynamic loading conditions. The strain was acquired through the combination of high speed camera and digital image correlation (DIC) method while the force was obtained with a customized load cell. Noticeable anisotropy and strain rate effect were observed for separators. The fracture mode of separators is highly correlated to the microscopic fiber orientation. To demonstrate the correlation microscopic images of separator material were obtained through SEM to match the facture edges of tensile tests at different loading directions.
Journal Article

Experimental Investigation of the Mechanical Behavior of Aluminum Adhesive Joints under Mixed-Mode Loading Conditions

In recent years, structural adhesives have rapidly become the preferred alternative to resistance spot welding in fabricating stronger, lighter aluminum connections. Connections inevitably undergo and must withstand complex quasi-static and/or dynamic loads during their service life. Therefore, understanding how loading conditions affect the mechanical behavior of adhesive joints is vital to their design and the advancement of structural safety. Quasi-static and dynamic tests are performed to analyze both the strength and failure modes of aluminum 6062 substrates bonded by an adhesive (Darbond EP-1506) for an array of loading directions. An Arcan test device, which enables application of mixed-mode loads ranging from pure peel (mode I) to pure shear (mode II) to the adhesive layer, is employed in quasi-static testing. A self-designed medium-speed test machine is utilized to perform dynamic testing.
Technical Paper

Comparative Study of Steel-Aluminum Mechanical Joints: Self-Piercing Riveting and Clinching

Nowadays manufacturing lightweight vehicles not only pursues more excellent structural performance of materials, but also puts effort on selecting or developing reliable technologies for joining dissimilar materials to offer sufficient structural stiffness and crashworthiness. Among the combinations of dissimilar materials, steels and aluminum alloys are the most prevalent that are applied to achieve viable and sustainable products. Joining processes of mechanical, chemical, thermal or a hybrid type can be selected to join steel and aluminum alloy together, which could become complicated considering the manufacturing conditions, the cost and so on. Self-piercing riveting (SPR) and clinching have many advantages, and are quite suitable for manufacturing steel-aluminum joints. SPR has good mechanical and fatigue strength while clinching has a lower manufacturing cost.