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Central cracking refers to the formation of internal cavities in cross wedge rolling (CWR) products. It occurs in various materials such as aluminium/titanium alloys, steels and plasticine at room or elevated temperatures, driven by different central cracking mechanisms. However, these mechanisms are still elusive, and a unified central cracking predictive model is absent due to the complex stress states within the workpiece, including triaxial stress states, cyclic loading and severe shear effects. In this study, the underlying fracture mechanisms were revealed, and a robust unified damage model with sound physical meanings was developed using a lab-scale CWR physical model and finite element models. The physical model with the plasticine billets was built, allowing the CWR dies with different geometries rapidly 3D printed and the billets with various ductility efficiently manufactured. The central cracking transiting from brittle to ductile fracture was experimentally observed for the first time using specifically designed plasticine/flour composite samples at varying ductility. The corresponding physics-based central cracking predictive model was proposed and validated quantitatively with 60 groups of CWR tests and compared with ten existing damage models/fracture criteria. This study effectively solves the long-lasting central cracking problem in the CWR industry and enhances the scientific understanding of fracture mechanics in complex engineering applications.

Solid-state dissimilar bi- or multi-metallic bonding is promising for achieving lightweight or multifunctional components in automotive, nuclear power and aerospace industries. To understand how to achieve a high-quality bonding interface between dissimilar materials, aluminium alloy (Al)–steel (Fe) bimetal gears manufactured under hot forge bonding were systematically investigated. In this work, comprehensive analyses of forge bonding mechanics, microstructure features, bonding interface behaviours and resulting mechanical properties were undertaken using ex/in-situ experiments and finite element modelling. The results revealed that the bonding behaviour and microstructure evolution were significantly affected by the mechanical property mismatch between the two dissimilar workpieces (AA6082 and E355). This mismatch could be effectively adjusted by setting different forging temperatures. The interfacial bonding strengths of AA6082 and E355, manufactured at low and high temperatures, were observed to be governed by interdiffusion and oxide particles, respectively. Balancing interdiffusion and oxide breaking appears to be key to achieving optimized interface strength for dissimilar bimetallic forge bonding technology.

Review Lightweight Materials in Electric Vehicles Xianyan Zhou 1,*, Jun Jiang 2, Zhili Hu 3, and Lin Hua 3 1 Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway 2 Department of Mechanical Engineering, Imperial College London, Exhibition Road, London, SW7 2AZ, UK 3 School of Automotive Engineering, Wuhan University of Technology, Luoshi Road, Wuhan, 430070, China * Correspondence: xianyan.zhou@ntnu.no Received: 23 September 2022 Accepted: 21 November 2022 Published: 18 December 2022 Abstract: Lightweight materials are highly demanded in electric vehicles (EVs) to reduce environmental impacts and energy consumption. Aluminium alloys are promising materials in EVs due to their advantages such as high specific strength, corrosion resistance and recyclability. However, forming complex-shaped thin-wall aluminium products is challenging due to their poor formability and limited dimensional accuracy. Meanwhile, recycling some of the high-strength aluminium alloys from EVs is still challenging. This review highlights some of the future potential aluminium forming techniques for EV production, including incremental sheet forming (ISF), hot forming and quenching (HFQ ® ) technique, and transverse stretching and local bending (TSLB). Also, the issues associated with aluminium recycling are listed and discussed. This review provides scientific guidance to the industry and the scientific community for advancing the applications of aluminium alloys in EVs.

Background: Farmers harvest two batches fruits of Lemons (Citrus limon L. Burm. f.) i.e., spring flowering fruit and autumn flowering fruit in dry-hot valley in Yunnan, China. Regular lemons harvested in autumn have smooth skin. However, lemons harvested in spring have rough skin, which makes them less attractive to customers. Furthermore, the rough skin causes a reduction in commodity value and economical losses to farmers. This is a preliminary study that investigates the key transcriptomic and metabolomic differences in peels of lemon fruits (variety Yuning no. 1) harvested 30, 60, 90, 120, and 150 days after flowering from the same trees in different seasons.Results: We identified 5,792, 4,001, 3,148, and 5,287 differentially expressed genes (DEGs) between smooth peel (C) and rough peel (D) 60, 90, 120, and 150 days after flowering, respectively. A total of 1,193 metabolites differentially accumulated (DAM) between D and C. The DEGs and DAMs were enriched in the mitogen-activated protein kinase (MAPK) and plant hormone signaling, terpenoid biosynthesis, flavonoid, and phenylalanine biosynthesis, and ribosome pathways. Predominantly, in the early stages, phytohormonal regulation and signaling were the main driving force for changes in peel surface. Changes in the expression of genes associated with asymmetric cell division were also an important observation. The biosynthesis of terpenoids was possibly reduced in rough peels, while the exclusive expression of cell wall synthesis-related genes could be a possible reason for the thick peel of the rough-skinned lemons. Additionally, cell division, cell number, hypocotyl growth, accumulation of fatty acids, lignans and coumarins- related gene expression, and metabolite accumulation changes were major observations.Conclusion: The rough peels fruit (autumn flowering fruit) and smooth peels fruit (spring flowering fruit) matured on the same trees are possibly due to the differential regulation of asymmetric cell division, cell number regulation, and randomization of hypocotyl growth related genes and the accumulation of terpenoids, flavonoids, fatty acids, lignans, and coumarins. The preliminary results of this study are important for increasing the understanding of peel roughness in lemon and other citrus species.

Central cracking in cross-wedge-rolled workpieces results in high wastage and economic loss. Recent cross-wedge rolling tests on two batches of steel showed that one batch formed central cracks, while the other was crack-free. The batches were both nominally of the same chemical composition and thermomechanical treatment history. In addition, both batches had passed all the standard quality assessments set for conventional forging processes. It was suspected that the different cracking behaviours were due to differences in microstructure between the two as-received steel billets, and the material in cross-wedge rolling (CWR) was more sensitive to the initial microstructure compared with other forging processes due to its specific loading condition including ostensibly compression and large plastic strain. Nevertheless, no previous study of this important problem could be identified. The aim of this study is, therefore, to identify the key microstructural features determining the central crack formation behaviour in CWR. The hot workability of the as-received billets was studied under uniaxial tensile conditions using a Gleeble 3800 test machine. Scanning electron microscope with energy-dispersive X-ray spectroscopy and electron backscatter diffraction was applied to characterise, quantitatively analyse, and compare the chemical composition, phase, grain, and inclusions in these two billets, both at room temperature and also at the CWR temperature (1080 °C). Non-metallic inclusions (oxides, sulphides, and silicates) in the billets were determined to be the main cause of the reported central cracking problem. The ductility of the steels at both room and elevated temperatures deteriorated markedly in the presence of the large volumes of inclusions. Grain boundary embrittlement occurred at the CWR temperature due to the aggregation of inclusions along the grain boundaries. It is suggested that a standard on specifying the inclusion quantity and size in CWR billets be established to produce crack-free products.

A large number of biologically active compounds are present in ripe citrus fruits. However, few studies have been focused on the changes in flavonoids and the evolution of antioxidant activity during citrus fruit growth. In this study, fruits of five citrus cultivars cultivated in China were sampled at 60-210 days post-anthesis (DPA) at intervals of 30 days. The amounts of main flavonoids in the peel and pulp were analyzed by HPLC and their activities were studied by DPPH, ABTS and FRAP. The results showed that the contents of hesperidin, diosmin, eriodictyol, rutin and nobiletin increased before 90 DPA and then decreased with the growth and development of fruits, but an opposite tendency was observed for naringin and narirutin. The antioxidant activities in citrus peel and pulp were found to be significantly correlated with some flavonoids. The results may be of guiding values in citrus production and utilization of citrus fruit by-products.

Oleocellosis is a physiological disorder causing blemishes on fruit surface. This study investigated the influence of oleocellosis on the membrane fatty acids and wax in lemon fruit rinds at the morphological, physiological, metabolic and molecular levels by using a variety with a high incidence rate of oleocellosis (green lemon). Oleocellosis-damaged rinds showed loose and flaky wax layers with more fissures on the surface, as well as higher contents of C16 and C18 fatty acids and very long chain (VLC) fatty alkanes while lower contents of VLC fatty aldehydes. The main differentially expressed genes, including FabZ, FAD2 and SAD6 involved in the accumulation of C16 and C18 fatty acids and CER1 involved in the transformation of VLC fatty aldehydes to VLC fatty alkanes, were up-regulated by oleocellosis. These results indicate that oleocellosis accelerates the accumulation of membrane free fatty acids and transformation of VLC fatty aldehydes to VLC fatty alkanes.

Cross wedge rolling (CWR) is an innovative metal forming process to manufacture axisymmetric stepped shafts used in the transport industry. Central cracking, also called the Mannesmann Effect, consistently occurs in the central region of the CWR workpiece. This results in reduced product quality and increased costs due to rejected and failed parts. However, the understanding of central cracking mechanism and criterion is limited due to the complex stress states in CWR and the experimental limitations. A large number of CWR tests and different die geometries are required in the identification of the potential mechanistic factors such as the axial tensile stress, secondary tensile stress, shear stress and cyclic loading. Also, there is as yet no efficient method of determining the material constants associated with the central cracking fracture criteria. These problems are addressed in the present study. A physical model was built to reproduce the industrial CWR process. A newly designed model material (plasticine/flour composite) was used to mimic the material flows and internal fracture behaviours found in commercial CWR workpieces. This allowed a variety of die shapes to be rapidly and cost-effectively 3D printed, thereby enabling specific stress states to be achieved within the workpiece. Via experimental observations and the corresponding finite element modelling under different die geometries, the maximum shear stress was identified as the dominant factor for central cracking. The fracture criterion involving the maximum shear stress was quantitatively verified to be accurate and robust in predicting central cracking moments and locations. A novel approach using simplified die geometries to determine the associated material constants was proposed and validated. The high accuracy and cost/time efficiency of this new approach will be a significant benefit to fundamental research and also in industrial applications.

To cope with the problems of energy shortage and environmental pollution caused by the large number of retired cars, the energy efficiency of shredding recycled car bodies urgently needs to be improved. Before shredding, recycled car bodies are always cut into shaped metal plates and piled in several sheets like sandwich plates. Currently, the lightweight design philosophy has driven the widespread application of multi-materials in car bodies. In this study, the finite element and experimental methods are used to analyse the shredding process of multi-material plates from recycled car bodies in order to determine the characteristics of plates with different thicknesses and materials. The results showed that the shredding efficiency of steel laminates with less than three sheets is quite low although the efficiency can be raised by increasing the thickness. The shredding energy efficiency is higher for Al alloy laminates than for steels. The shredding energy efficiency can be improved by raising the strength of the shredding material. The results of this study proved that the shredding energy consumption can be reduced by shredding the different materials of the multi-material boards separately.

Recycling retired cars can relieve the environmental pollution and resource waste efficiently. However, a few publications can be found on the failure mechanisms and optimization method of recycling equipment, shredders. Thus, the failure mechanisms and structural optimization of shredder hammers for retired cars are studied aiming improving shredding efficiency and reducing cost. Failure types of shredder hammer are studied theoretically, and it is found that wear failure and fatigue failure are the two main failure types of shredder hammer. The shredding process of metal scraps is analyzed by finite element method, and it can be divided into four stages based on the stress states: initial stage, collision stage, grinding stage and separation stage. It is proved that the shredding efficiency can be improved by increasing cutouts on the hammer head. Finally, it is determined that the hammer with two cutouts is the optimal structure for metal scraps, which can improve the shredding efficiency by 20% and lengthen the hammer life by 15%. This study provides scientific basis for the industry application and theoretical foundation for further research.

The hammer shredder is the key equipment for cyclic utilization of retired car bodies. The axes' pin is the main component of the shredder, but it is damaged easily. To improve the shredding efficiency and lengthen the changing life of the shredder pin, it is significant to study its stress characteristic and the fatigue life. In this article, the complex force conditions of the shredder pin at the normal working condition were studied briefly by mechanics analysis method. The stress characteristics and fatigue life of the pin were analyzed by the finite element transient analysis method. The maximum stress distribution law of the shredder pin was found and the fracture mechanism of the retired car bodies was revealed. Furthermore, the reliability of the simulation results was verified by the experiment. It was found that when the pin rotates around the main shaft counterclockwise, the maximum stress of the pin at 0° of the main shaft is higher than other positions. Additionally, along the axial direction, the maximum stress occurs at the cross section at a distance of 2/9 of the pin length from the pin head and at 0° of this section, which orientation is made when the pin is at 270° of the main shaft. Comparing four working modes, it was found that the working life of the shredder pin could be doubled by changing the sides of the pin and rotate it along its axes by 180°.

Pummelo (Citrus grandis Osbeck.) is a major commercial fruit in the world. In this study, samples of three popular varieties, namely “Huangjin”, “Sanhong” and “Dongshizao”, were collected from three commercial orchards located in China. A total of 153 metabolites in the pulp were annotated and analyzed using UPLC-QTRAP-MS/MS and GC-MS, and PCA of these metabolites could clearly distinguish the three varieties. The pulp of “Dongshizao” had the most enjoyable taste, and that of “Huangjin” had the strongest aroma. The most important aroma compounds were hexanal, β-myrcene and trans-2-decene. Amino acids were positively correlated with 18 volatile substances, and also affected the tastes of sweetness, sourness and bitterness. Unsaturated fatty acids accounted for 70% of total fatty acids. The types of sugars and organic acids were similar among different varieties, but differences in the contents of individual substances and sugar/acid ratio contributed to different tastes.

Cross wedge rolling (CWR) is an innovative roll forming process, used widely in the transportation industry. It has high production efficiency, consistent quality and efficient material usage. However, the continual occurrence of crack formation in the centre of the workpiece is a critical problem excluding the CWR technique from more safety-critical applications, in particular, aerospace components. The mechanisms of central fracture formation are still unclear because of a combination of complicated stress and strain states at various stages of CWR. Thus, the aim of this study is to understand the stress/strain distribution and evolution during the CWR process and identify the key variables which determine central crack formation. A comprehensive investigation was then conducted to simulate 27 experimental cases. The stress and strain distributions in the workpiece were evaluated by finite element analysis. Various damage models from literature were applied and compared. A new fracture criterion was proposed, which was able to successfully determine the central crack formation in all 27 experimental cases. This criterion can be applied in CWR tool and process design, and the enhanced understanding may enable the adoption of CWR by the aerospace industry.

Spinel LiMn 2 O 4 cathode material was rapidly prepared by solid-state combustion synthesis based on a two-stage calcination progress which used lithium carbonate and manganese carbonate as raw materials and citric acid as a fuel. The structure and physicochemical properties of the obtained LiMn 2 O 4 powders were investigated by thermogravimetric analysis (TG) and differential thermal analysis (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge–discharge test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that the successful formation of single-phase LiMn 2 O 4 product is highly dependent on its second-stage calcination temperature. Compared with other conditions, the as-prepared LiMn 2 O 4 powders which experienced the second-stage, and calcined at 700 °C is the most uniform, and the charge transfer resistance ( R ct ) is the lowest, accompanying the best electrochemical activity and highest discharge capacity. Its initial discharge specific capacity is 119.1 mA h/g.

This paper presents analysis of a 3-dimensional engineered structural panel (3DESP) having a tri-axial core structure made from phenolic impregnated laminated-paper composites with and without high-strength composite carbon-fiber fabric laminated to the outside of both faces. Both I-beam equations and finite element method were used to analyze four-point bending of the panels. Comparisons were made with experimental panels. In this study, four experimental panels were fabricated and analyzed to determine the influence of the carbon-fiber on bending performance. The materials properties for finite element analyses (FEA) and I-beam equations were obtained from either the manufacturer or in-house material tensile tests. The results of the FEA and I-beam equations were used to compare with the experimental 3DESP four-point bending tests. The maximum load, face stresses, shear stresses, and apparent modulus of elasticity were determined. For the I-beam equations, failure was based on maximum stress values. For FEA, the Tsai-Wu strength failure criterion was used to determine structural materials failure. The I-beam equations underestimated the performance of the experimental panels. The FEA-estimated load values were generally higher than the experimental panels exhibiting slightly higher panel properties and load capacity. The addition of carbon-fiber fabric to the face of the panels influenced the failure mechanism from face buckling to panel shear at the face–rib interface. FEA provided the best comparison with the experimental bending results for 3DESP.

Spinel LiMn2O4 cathode material was rapidly synthesized in 1 h by solid-state combustion synthesis using metal carbonates as metal ion sources and glucose as a fuel. The effect of different amounts of glucose on the structure and electrochemical performance of as-prepared LiMn2O4 was investigated by X-ray diffraction (XRD), scanning electron micrographs (SEM), galvanostatic charge–discharge test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). LiMn2O4 spinel was identified as the main crystalline phase with the presence of minor Mn3O4. The amount of glucose greatly affected the formation of Mn3O4. The optimal content of glucose was found to be 10 wt%. Under this condition, the Mn3O4 peaks almost disappeared, and high-purity spinel LiMn2O4 was obtained. Its initial discharge specific capacity of was 125.9 mAh/g, and discharge specific capacity retained at 105.2 mAh/g after 40 cycles. The detail influence of glucose on the electrochemical activity, reversibility and cycling performance of LiMn2O4 was discussed.

Bamboo leaves has been used to heal some diseases in the Chinese Folk for a long time. In order to explore the wide biomedicine utilization, the determination of the chemical components of benzene-alcohol extractives from the fresh Phyllostachys pubescens leaves was made by using Py-GC/MS. The results indicated that the main components were 1,3-Butadiene, 2-methyl-, 1-Phenanthrenecarboxylic acid, 1,2,3,4,4a,9,10,10a-octahydro-1,4a-dimethyl-7-(1-methylethyl)-, 1-Hexadecene, 1-Butene, Propene, 1-Pentene, 4-methyl-, 1-Pentene, 2-methyl-, Bicyclo[3.1.1]heptane,2,6,6-trimethyl-, Stigmastan-3,5-diene, Nonacosane, 1-Docosene, 1,3-Cyclohexadiene, Tetracosane, Toluene, Heptacosane, 1-chloro-, 1-Heptene, 2-isohexyl-6-methyl-, Stigmast-4-en-3-one, Hexacosanoic acid, methyl ester, Sulfide, bis(2-cyano-3,4-dihydro-2,3,3-trimethyl-2H-pyrrol-5-yl)-, etc. So the benzene-alcohol extractives of Phyllostachys pubescens leaves could be used as rare biomedicines.

Bamboo is so easy to moulding that bamboo products haven't been high value added utilization. Therefore, the effect of wood extractives molecules on bamboo biology moulding was studied based on full-factor test. The result is: (1) The effect of tree species of wood extractives on bamboo biomass moulding was highly remarkable. The effect of treatment time on bamboo biology moulding was not remarkable.(2) The better anti-mold effects of wood extractives were Cassia siamea, Cunninghamia lanceolata, Eucalyptus urophydis, Populusdeltoides in turn. So this pointed out the direction for the development of the biologic mould inhibitor.

Long-term tests (864 days) were conducted on three types of columns, including plain concrete (PC) columns, reinforced concrete (RC) columns and concrete-filled steel tube (CFST) columns. The shrinkage and creep performance and the ultimate strength of the columns were tested and analyzed. The results show that the shrinkage strain of RC columns is about 87.6% of that of PC columns, the shrinkage strain of the CFST columns is about 34.8% of that of PC columns, and that the effect of expansion agent on shrinkage strain is about 2% for the PC columns. It was also found that the smaller the loading age, the greater the creep coefficient. Reinforcement can significantly reduce the creep deformation of PC columns. The creep coefficient of steel pipe surface is larger than that of inner concrete for CFST columns, leading to a longer life due to the creep of inner concrete to achieve stability. The loading age and the reinforcement have great impact on extreme compressive strain and ultimate strength. The hoop effect of RC columns is obvious. Loading rate influences the stress redistribution of CFST columns. The stress redistribution effect is relatively small for columns with loading course. However, the effect on the ultimate strength is very small for columns with or without loading courses. The difference of two is only 2.4%.