Mechanical degradation, especially fractures in active particles in an electrode, is a major reason why the capacity of lithiumion batteries fades. This paper proposes a model that couples Li-ion diffusion, stress evo...Mechanical degradation, especially fractures in active particles in an electrode, is a major reason why the capacity of lithiumion batteries fades. This paper proposes a model that couples Li-ion diffusion, stress evolution, and damage mechanics to simulate the growth of central cracks in cathode particles（Li Mn_2 O_4） by an extended finite element method by considering the influence of multiple factors. The simulation shows that particles are likely to crack at a high discharge rate, when the particle radius is large, or when the initial central crack is longer. It also shows that the maximum principal tensile stress decreases and cracking becomes more difficult when the influence of crack surface diffusion is considered. The fracturing process occurs according to the following stages： no crack growth, stable crack growth, and unstable crack growth. Changing the charge/discharge strategy before unstable crack growth sets in is beneficial to prevent further capacity fading during electrochemical cycling.展开更多
Central crack is a common quality defect in continuous casting strand,which is difficult to fully weld in the rolling and forging processes,and has become a key technical problem that restricts the stable production o...Central crack is a common quality defect in continuous casting strand,which is difficult to fully weld in the rolling and forging processes,and has become a key technical problem that restricts the stable production of high-end alloy rod/forging/pipe.In recent years,the central crack control has been one of the main focuses in high quality steel research.In order to fully understand the central crack,the research status of central crack characteristics,formation mechanism,influencing factors,and control methods in the world was reviewed.The deficiencies in the research of the central crack and the key research directions in the future were pointed out,which will provide references for other scholars in this field of research.It is found that alloying elements segregation during solidification and inclusions precipitated at grain boundaries are the main reasons for the central crack formation,while the unreasonable application of production processes can also induce the initiation of central crack.The optimization of alloying element composition and production process is helpful to reduce the initiation of central cracks.In addition,the quantitative characterization mechanism based on steel grades,temperature,stress,and other factors induced central crack should be established in the further study,forming a systematic quantitative determination criterion and control strategy for coupling the composition,process and thermal/mechanical characteristic.展开更多
In this paper, the fracture problem in non-principal directions of elasticity for a simple layer plate of linear-elastic orthotropic composite materials is studied. The formulae of transformation between characteristi...In this paper, the fracture problem in non-principal directions of elasticity for a simple layer plate of linear-elastic orthotropic composite materials is studied. The formulae of transformation between characteristic roots, coefficients of elastic compliances in non-principal directions of elasticity and corresponding parameters in principal directions of elasticity are derived. Then, the computing formulae of strain energy release rate under skew-symmetric loading in terms of engineering parameters for principal directions of elasticity are obtained by substituting crack-tip stresses and displacements into the basic formula of the strain energy release rate.展开更多
For determining the optimal percentage of RAP material in central plant hot recycling, binder was recovered from RAP by means of Abson recovery method, and properties tests of mixed binders consisting of recovered asp...For determining the optimal percentage of RAP material in central plant hot recycling, binder was recovered from RAP by means of Abson recovery method, and properties tests of mixed binders consisting of recovered asphalt and fresh asphalt at different ratios were performed. In addition, the performances of mixture with different percentages of RAP such as rutting resistance, anti-cracking, moisture susceptibility and fatigue resistance were tested. The binder test results showed that the high temperature performance was improved with the increase of the percentage of the RAP, while the low temperature performance was declined. When the percentage of the recovered binder was less than 30%, the mixed binder could match the technical standards for fresh asphalt. Tests on the mixtures showed that rutting resistance increased gradually as RAP percentage increased, while thermal anti-cracking at low temperature and fatigue properties declined. The effect of the percentage of RAP on moisture susceptibility was limited. It is indicated that low temperature performance and fatigue properties are important for selecting the optimal percentage of RAP. Based on data obtained from binders and mixtures, it is concluded that the maximum percentage of RAP is approximately 30% without the addition of rejuvenating agent.展开更多
基金support of the National Natural Science Foundation of China (11472165 and 11332005)
文摘Mechanical degradation, especially fractures in active particles in an electrode, is a major reason why the capacity of lithiumion batteries fades. This paper proposes a model that couples Li-ion diffusion, stress evolution, and damage mechanics to simulate the growth of central cracks in cathode particles（Li Mn_2 O_4） by an extended finite element method by considering the influence of multiple factors. The simulation shows that particles are likely to crack at a high discharge rate, when the particle radius is large, or when the initial central crack is longer. It also shows that the maximum principal tensile stress decreases and cracking becomes more difficult when the influence of crack surface diffusion is considered. The fracturing process occurs according to the following stages： no crack growth, stable crack growth, and unstable crack growth. Changing the charge/discharge strategy before unstable crack growth sets in is beneficial to prevent further capacity fading during electrochemical cycling.
基金financially supported by the National Natural Science Foundation of China(No.52074207)the Shaanxi Natural Science Basic Research Program(No.2023-JC-QN-0376).
文摘Central crack is a common quality defect in continuous casting strand,which is difficult to fully weld in the rolling and forging processes,and has become a key technical problem that restricts the stable production of high-end alloy rod/forging/pipe.In recent years,the central crack control has been one of the main focuses in high quality steel research.In order to fully understand the central crack,the research status of central crack characteristics,formation mechanism,influencing factors,and control methods in the world was reviewed.The deficiencies in the research of the central crack and the key research directions in the future were pointed out,which will provide references for other scholars in this field of research.It is found that alloying elements segregation during solidification and inclusions precipitated at grain boundaries are the main reasons for the central crack formation,while the unreasonable application of production processes can also induce the initiation of central crack.The optimization of alloying element composition and production process is helpful to reduce the initiation of central cracks.In addition,the quantitative characterization mechanism based on steel grades,temperature,stress,and other factors induced central crack should be established in the further study,forming a systematic quantitative determination criterion and control strategy for coupling the composition,process and thermal/mechanical characteristic.
文摘In this paper, the fracture problem in non-principal directions of elasticity for a simple layer plate of linear-elastic orthotropic composite materials is studied. The formulae of transformation between characteristic roots, coefficients of elastic compliances in non-principal directions of elasticity and corresponding parameters in principal directions of elasticity are derived. Then, the computing formulae of strain energy release rate under skew-symmetric loading in terms of engineering parameters for principal directions of elasticity are obtained by substituting crack-tip stresses and displacements into the basic formula of the strain energy release rate.
文摘For determining the optimal percentage of RAP material in central plant hot recycling, binder was recovered from RAP by means of Abson recovery method, and properties tests of mixed binders consisting of recovered asphalt and fresh asphalt at different ratios were performed. In addition, the performances of mixture with different percentages of RAP such as rutting resistance, anti-cracking, moisture susceptibility and fatigue resistance were tested. The binder test results showed that the high temperature performance was improved with the increase of the percentage of the RAP, while the low temperature performance was declined. When the percentage of the recovered binder was less than 30%, the mixed binder could match the technical standards for fresh asphalt. Tests on the mixtures showed that rutting resistance increased gradually as RAP percentage increased, while thermal anti-cracking at low temperature and fatigue properties declined. The effect of the percentage of RAP on moisture susceptibility was limited. It is indicated that low temperature performance and fatigue properties are important for selecting the optimal percentage of RAP. Based on data obtained from binders and mixtures, it is concluded that the maximum percentage of RAP is approximately 30% without the addition of rejuvenating agent.
