Cubic boron nitride(cBN)grinding wheels play a pivotal role in precision machining,serving as indispensable tools for achieving exceptional surface quality.Ensuring the sharpness of cBN grains and optimizing the grind...Cubic boron nitride(cBN)grinding wheels play a pivotal role in precision machining,serving as indispensable tools for achieving exceptional surface quality.Ensuring the sharpness of cBN grains and optimizing the grinding wheel’s chip storage capacity are critical factors.This paper presents a study on the metal-bonded segments and single cBN grain samples using the vacuum sintering method.It investigates the impact of blasting parameters-specifically silicon carbide(SiC)abrasive size,blasting distance,and blasting time-on the erosive wear characteristics of both the metal bond and abrasive.The findings indicate that the abrasive size and blasting distance significantly affect the erosive wear performance of the metal bond.Following a comprehensive analysis of the material removal rate of the metal bond and the erosive wear condition of cBN grains,optimal parameters for the working layer are determined:a blasting distance of 60 mm,a blasting time of 15 s,and SiC particle size of 100#.Furthermore,an advanced simulation model investigates the dressing process of abrasive blasting,revealing that the metal bond effectively inhibits crack propagation within cBN abrasive grains,thereby enhancing fracture toughness and impact resistance.Additionally,a comparative analysis is conducted between the grinding performance of porous cBN grinding wheels and vitrified cBN grinding wheels.The results demonstrate that using porous cBN grinding wheels significantly reduces grinding force,temperature,and chip adhesion,thereby enhancing the surface quality of the workpiece.展开更多
Conventional wound dressings only protect passively against bacterial infection.Emerging mechanically active adhesive dressings(AADs)are inspired by the active closure of embryonic wounds.It can promote wound healing ...Conventional wound dressings only protect passively against bacterial infection.Emerging mechanically active adhesive dressings(AADs)are inspired by the active closure of embryonic wounds.It can promote wound healing by actively con-tracting the wound bed.AADs meet the requirements of high toughness,stimulus-response,and dynamic adhesion proper-ties,which are challenging.Hence,we construct a water-responsive shape memory polyurea fibrous membrane(PU-fm)featuring favorable toughness,wet-adhesion,breathability,absorbency of four times its weight,and antibacterial.First,the water-toughened electrospun PU-fm is fabricated using a homemade polyurea(PU)elastomer with multistage hydrogen bond networks as a spinning solution.Furthermore,a Janus-structured polyurea-polydopamine-silver fibrous membrane(PU@PDA@Ag-fm)is engineered,integrating antibacterial properties without compromising mechanical robustness.It demonstrates strong adhesion to the skin,actively promotes wound contraction,and enables adaptive wrapping of tissues of varying sizes by the water-driven shape memory effect.Antibacterial tests and wound healing experiments indicate that the PU@PDA@Ag-fm has favorable antibacterial properties against Escherichia coli(E.coli)and accelerates the wound healing rate by 20%.For the first time,water-responsive shape memory PU-fm as the AADs is constructed,providing a new strategy for wound management.This can be extended to applications in other smart devices for biomedicine such as tendon repair,and bioelectronic interfaces.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.92160301,92060203,52175415,52205475,and 52205493)Science Center for Gas Turbine Project(Grant Nos.P2022-AB-IV-002-001 and P2023-B-IV-003-001)+3 种基金Jiangsu Provincial Natural Science Foundation(Grant No.BK20210295)the Huaqiao University Engineering Research Center of Brittle Materials Machining(Grant No.2023IME-001)Foundation of Graduate Innovation Centre in NUAA(Grant No.XCXJH20230509)Fundamental Research Funds for the Central Universities(Grant Nos.NS2023028 and NG2024015).
文摘Cubic boron nitride(cBN)grinding wheels play a pivotal role in precision machining,serving as indispensable tools for achieving exceptional surface quality.Ensuring the sharpness of cBN grains and optimizing the grinding wheel’s chip storage capacity are critical factors.This paper presents a study on the metal-bonded segments and single cBN grain samples using the vacuum sintering method.It investigates the impact of blasting parameters-specifically silicon carbide(SiC)abrasive size,blasting distance,and blasting time-on the erosive wear characteristics of both the metal bond and abrasive.The findings indicate that the abrasive size and blasting distance significantly affect the erosive wear performance of the metal bond.Following a comprehensive analysis of the material removal rate of the metal bond and the erosive wear condition of cBN grains,optimal parameters for the working layer are determined:a blasting distance of 60 mm,a blasting time of 15 s,and SiC particle size of 100#.Furthermore,an advanced simulation model investigates the dressing process of abrasive blasting,revealing that the metal bond effectively inhibits crack propagation within cBN abrasive grains,thereby enhancing fracture toughness and impact resistance.Additionally,a comparative analysis is conducted between the grinding performance of porous cBN grinding wheels and vitrified cBN grinding wheels.The results demonstrate that using porous cBN grinding wheels significantly reduces grinding force,temperature,and chip adhesion,thereby enhancing the surface quality of the workpiece.
基金supported by the National Key R&D Program of China(No.2022YFB3805700)National Natural Science Foundation of China(No.92271206).
文摘Conventional wound dressings only protect passively against bacterial infection.Emerging mechanically active adhesive dressings(AADs)are inspired by the active closure of embryonic wounds.It can promote wound healing by actively con-tracting the wound bed.AADs meet the requirements of high toughness,stimulus-response,and dynamic adhesion proper-ties,which are challenging.Hence,we construct a water-responsive shape memory polyurea fibrous membrane(PU-fm)featuring favorable toughness,wet-adhesion,breathability,absorbency of four times its weight,and antibacterial.First,the water-toughened electrospun PU-fm is fabricated using a homemade polyurea(PU)elastomer with multistage hydrogen bond networks as a spinning solution.Furthermore,a Janus-structured polyurea-polydopamine-silver fibrous membrane(PU@PDA@Ag-fm)is engineered,integrating antibacterial properties without compromising mechanical robustness.It demonstrates strong adhesion to the skin,actively promotes wound contraction,and enables adaptive wrapping of tissues of varying sizes by the water-driven shape memory effect.Antibacterial tests and wound healing experiments indicate that the PU@PDA@Ag-fm has favorable antibacterial properties against Escherichia coli(E.coli)and accelerates the wound healing rate by 20%.For the first time,water-responsive shape memory PU-fm as the AADs is constructed,providing a new strategy for wound management.This can be extended to applications in other smart devices for biomedicine such as tendon repair,and bioelectronic interfaces.
