Graphene(G),as a typical two-dimensional material,is often used as an additive for liquid lubricants.However,graphene is mostly added to liquid lubricants in a one-time manner in friction;it mainly exists in the form ...Graphene(G),as a typical two-dimensional material,is often used as an additive for liquid lubricants.However,graphene is mostly added to liquid lubricants in a one-time manner in friction;it mainly exists in the form of multilayer agglomerated structures due to theπ–πstacking between graphene sheets,making it unable to fully exert the synergistic lubrication function.Herein,we propose a new macroscopic superlubric system of graphene/potassium hydroxide(G/KOH)solution;and the graphene additive involved is exfoliated in-situ from graphene/epoxy(G/EP)friction pair by friction,continuously providing freshly-peeled graphene into KOH solution and minimizing the adverse effects of graphene agglomeration.Moreover,the in-situ produced graphene additive has thinner thickness and better anti-aggregation ability,which provide more graphene to accommodate OH−,form more stacked sandwich structures of OH−/graphene/OH−between friction pairs(i.e.,equivalent to a moving pulley block with more wheels),and finally realize superlubricity.This study develops a new liquid superlubric system suitable for alkaline environments,and at the same time proposes a new way to gradually release graphene additives in situ,rather than adding them all at once,deepening the understanding to liquid superlubricity mechanism,and paving the experimental foundation for the practical application of macroscopic superlubricity.展开更多
The application of lightweight structures with excellent energy absorption performance is crucial for enhancing vehicle safety and energy efficiency.Cellular structures,inspired by the characteristics observed in natu...The application of lightweight structures with excellent energy absorption performance is crucial for enhancing vehicle safety and energy efficiency.Cellular structures,inspired by the characteristics observed in natural organisms,have exhibited exceptional structural utilization in terms of energy absorption compared with traditional structures.In recent years,various innovative cellular structures have been proposed to meet different engineering needs,resulting in significant performance improvements.This paper provides a comprehensive overview of novel cellular structures for energy absorption applications.In particular,it outlines the application forms and design concepts of cellular structures under typical loading conditions in vehicle collisions,including axial loading,oblique loading,bending loading,and blast loading.Cellular structures have evolved to meet the demands of complex loading conditions and diverse research methods,focusing on achieving high-performance characteristics across multiple load cases.Moreover,this review discusses manufacturing techniques and strate-gies for enhancing the manufacturing performance of cellular structures.Finally,current key challenges and future research directions for cellular structures are discussed.The aim of this study is to provide valuable guidelines for researchers and engineers in the development of next-generation lightweight cellular structures.展开更多
With the development of three-dimensional printing technologies, so-called cellular materials have achieved increasingattention due to outstanding properties. Unlike pure solid structures, properties of cellular mater...With the development of three-dimensional printing technologies, so-called cellular materials have achieved increasingattention due to outstanding properties. Unlike pure solid structures, properties of cellular materials are influenced by bothutilized material and cell microtopology. The present paper proposes a novel type of re-entrant square cellular material.To explore the relationship between microtopology and macrodynamic responses systematically, an explicit dynamic finiteelement simulation method is used. This work starts by constructing theoretical models of relative density employing atwo-dimensional unit cell. Then, the effects of geometric features and configurations on dynamic properties are explored,and simulations indicate that variations of geometric parameters strongly affect properties and that the staggered re-entrantsquares are more stable than the regular re-entrant squares. Subsequently, the effects of the impact velocity on dynamiccrushing behaviors are elaborated. On this basis, the relationship of unit mass energy absorption and geometric features isobtained by employing the response surface method. Furthermore, with targets of maximum unit mass energy absorption andminimum relative density, the optimal structural parameters are achieved by using non-dominated sorting genetic algorithm.The study provides a detailed introduction to dynamic behaviors of cellular materials and guidance to design new structureswith superior characteristics of energy absorption.展开更多
基金supported by the National Natural Science Foundation of China(52075224,21975109,51975252,and 52075225)Natural Science Foundation of Jiangsu Province(BK20201423)+1 种基金Foundation of State Key Laboratory of Solid Lubrication(LSL-1801)Tribology Science Fund of State Key Laboratory of Tribology(SKLTKF18B03).
文摘Graphene(G),as a typical two-dimensional material,is often used as an additive for liquid lubricants.However,graphene is mostly added to liquid lubricants in a one-time manner in friction;it mainly exists in the form of multilayer agglomerated structures due to theπ–πstacking between graphene sheets,making it unable to fully exert the synergistic lubrication function.Herein,we propose a new macroscopic superlubric system of graphene/potassium hydroxide(G/KOH)solution;and the graphene additive involved is exfoliated in-situ from graphene/epoxy(G/EP)friction pair by friction,continuously providing freshly-peeled graphene into KOH solution and minimizing the adverse effects of graphene agglomeration.Moreover,the in-situ produced graphene additive has thinner thickness and better anti-aggregation ability,which provide more graphene to accommodate OH−,form more stacked sandwich structures of OH−/graphene/OH−between friction pairs(i.e.,equivalent to a moving pulley block with more wheels),and finally realize superlubricity.This study develops a new liquid superlubric system suitable for alkaline environments,and at the same time proposes a new way to gradually release graphene additives in situ,rather than adding them all at once,deepening the understanding to liquid superlubricity mechanism,and paving the experimental foundation for the practical application of macroscopic superlubricity.
基金supported by National Key Research and Development Program of China(2022YFB2503502)National Natural Science Foundation of China(51975244).
文摘The application of lightweight structures with excellent energy absorption performance is crucial for enhancing vehicle safety and energy efficiency.Cellular structures,inspired by the characteristics observed in natural organisms,have exhibited exceptional structural utilization in terms of energy absorption compared with traditional structures.In recent years,various innovative cellular structures have been proposed to meet different engineering needs,resulting in significant performance improvements.This paper provides a comprehensive overview of novel cellular structures for energy absorption applications.In particular,it outlines the application forms and design concepts of cellular structures under typical loading conditions in vehicle collisions,including axial loading,oblique loading,bending loading,and blast loading.Cellular structures have evolved to meet the demands of complex loading conditions and diverse research methods,focusing on achieving high-performance characteristics across multiple load cases.Moreover,this review discusses manufacturing techniques and strate-gies for enhancing the manufacturing performance of cellular structures.Finally,current key challenges and future research directions for cellular structures are discussed.The aim of this study is to provide valuable guidelines for researchers and engineers in the development of next-generation lightweight cellular structures.
基金This work was supported by the China Scholar-ship Council(Grant No.201606170199)the NationalKey Research and Development Program of China(2016YFB0101601).
文摘With the development of three-dimensional printing technologies, so-called cellular materials have achieved increasingattention due to outstanding properties. Unlike pure solid structures, properties of cellular materials are influenced by bothutilized material and cell microtopology. The present paper proposes a novel type of re-entrant square cellular material.To explore the relationship between microtopology and macrodynamic responses systematically, an explicit dynamic finiteelement simulation method is used. This work starts by constructing theoretical models of relative density employing atwo-dimensional unit cell. Then, the effects of geometric features and configurations on dynamic properties are explored,and simulations indicate that variations of geometric parameters strongly affect properties and that the staggered re-entrantsquares are more stable than the regular re-entrant squares. Subsequently, the effects of the impact velocity on dynamiccrushing behaviors are elaborated. On this basis, the relationship of unit mass energy absorption and geometric features isobtained by employing the response surface method. Furthermore, with targets of maximum unit mass energy absorption andminimum relative density, the optimal structural parameters are achieved by using non-dominated sorting genetic algorithm.The study provides a detailed introduction to dynamic behaviors of cellular materials and guidance to design new structureswith superior characteristics of energy absorption.
