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This study analyzed the closed-die forging process of the copper alloy valve body is presented. Two variants represent the forging processes of the copper alloy valve body on conventional double-action press and multicored forging press, which differ in the initial positions of punches and the sequences of punches movement. A comparison of the two processes was made by finite element (FE) simulations, which include geometry, filling sequence, and force. However, during the experiment, it was found that when the copper alloy valve body was forged on a conventional double-action press, the central punch was easy to bend or even break, and the end surface of the central valve hole was prone to cold shut. Through further analysis of the experimental process and FE simulation results, the causes of mould failure and valve body defects were discovered. FE simulation results of force, strain, and stress all showed that the technological safety and the product quality of multicored forging press were considerably better than those of the forging on a conventional double-action press. The experimental results were in agreement with the FE simulation results.

Understanding the mechanical, thermal, and electrical properties of prismatic lithium-ion batteries (LIBs) is vital to battery safety design, which is key to electric vehicle safety. This study investigated prismatic LIBs subjected to multiple-position indentation loading. The side face of an intact prismatic LIB cell is divided into 15 compressed sections. Experimental results indicate that indentation loading of all sections could initiate thermal runaway. Among the sections studied, that near the positive terminal shows the highest risk of thermal runaway, whereas that near the top-right corner is relatively safe. Failure mode analysis reveals that short circuits may result from contact between the positive and negative current collectors.

Lithium-ion batteries (LIBs) inevitably encounter abusive mechanical loading during engineering applications and result in mechanical deformation, internal short circuit, and even thermal runaway. A 18650 LIB under minor mechanical deformation is subjected to cyclic charge/discharge experiments in this study to analyze its aging behavior. Aging mechanism of the battery with minor deformation is qualitatively investigated through the incremental capacity analysis (ICA). ICA, a commonly used method for exploring degradation mechanism of LIBs, can transform flat voltage plateaus into peaks in the capacity increase curve (IC curve). Experimental data during the battery charging/discharging cycle can be used to calculate the IC curve, which can reflect the characteristics of electrochemical changes inside the battery. Results showed that the LIB suffers from deterioration in the state of health (SOH) in the entire charge/discharge cycle upon minor mechanical deformation. Possible explanations for the slight decrease in SOH with the increasing number of cycles in the early stages and the rapid decrease in the charge/discharge capacity in the late stages were provided. However, precise mechanisms for these phenomena require further detailed research. Moreover, damaged cells demonstrate considerably higher temperature increments than original ones. This temperature difference will increase if additional charging/discharging cycles are conducted. This research infers that additional metallic lithium deposits in damaged cells compared with the original ones cause serious exothermic reactions and lead to enhanced heat accumulation.

Purpose The dent is one of typical surface defects on the surfaces of the machine elements and it is not in fact inerratic. This work aims to investigate the effect of a single dent with a marginal bump on the film shape in elastohydrodynamic lubrication (EHL) point contacts. Design/methodology/approach The experimental investigations of a single dent with marginal bump were carried out using multi-beam interferometry in EHL point contacts. In the meantime, its numerical simulation was also finished using multi-level method and multilevel multi-integration method. The effects of the entrainment velocity and the applied load as well as the slide-roll ratio on the film were chiefly discussed. Meanwhile, the comparison of films between smooth and dented surfaces was conducted under simple sliding conditions. Findings Under pure sliding conditions, the minimum film thickness presents itself near the marginal bump at lower entrainment velocity. The inlet dimple before the marginal bump is subjected to the operating conditions. Under pure rolling conditions, the shape of the dent is almost unchanged when it is passing through the contact region at lower entrainment velocity. The dent depth hardly depends on the applied load under static conditions. However, larger load enhances the inlet dimple and the elastic deformation of the dent with the marginal bump under pure sliding conditions. Originality/value This work is helpful to understanding the effect of the marginal bump before the single dent on point contact EHL films.

Cavitation in fluid film lubrication was experimentally observed by optical interferometry under point and elliptical contacts. Fern leaf cavities and stripe-shaped cavities presented themselves in pure rolling, while string-shaped cavities and sheet cavitation were found in disk simple sliding. Cavitation zone moves downstream toward the outlet of the contact zone with increasing entrainment speed in pure rolling, whereas it is just the reverse in disk simple sliding. Increasing applied load increases threshold speed of occurrence of sheet cavitation. Under elliptical contacts, this threshold speed increases with increasing included angle between the entrainment direction and the minor axis of the elliptical contact zone; the included angle mentioned above markedly affects the position and shape of cavitation zone.