A MICROSTRUCTURE-BASED ANALYSIS FOR CYCLIC PLASTICITY OF DUAL-PHASE PEARLITIC RAIL STEELS

Based on the assumption that a representative element of apearlitic steel is an aggregate of numerous spherical pearliticcolonies with randomly distributed orientations, and that each colonyis com- posed of many parallel fine lamellas of ferrite andcementite, a description for the dual-phase pearlitic steel isobtained by making use of a microstructure-based constitutiveequation for a single dual-phase pearlitic colony and the Hill'sself-consistent scheme. The elastoplastic response of dual-phasepearlitic steel BS11 subjected to asymmetrically cyclic loading isanalyzed, and a comparison with the experimental results showssatisfacto- ry agreement. The non-proportional cyclic plasticity ofBS11 is also analyzed, in which stress develops along a semi-circlein a biaxial tension/compression and shear stress plane, as istypically experienced by the sur- face elements in rolling andsliding contact.

The effect of different layered materials on the tribological properties of PTFE composites

Two-dimensional(2D)lamellar materials have unique molecular structures and mechanical properties,among which molybdenum disulfide(MoS2)and graphitic carbon nitride(g-C3N4)with different interaction forces served as reinforcing phase for polytetrafluoroethylene(PTFE)composites in the present study.Thermal stability,tribological and thermomechanical properties of composites were comprehensively investigated.It was demonstrated that g-C3N4 improved elastic deformation resistance and thermal degradation characteristics.The addition of g-C3N4 significantly enhanced anti-wear performance under different loads and speeds.The results indicated that PTFE composites reinforced by g-C3N4 were provided with better properties because the bonding strength of g-C3N4 derived from hydrogen bonds(H-bonds)was stronger than that of MoS2 with van der Waals force.Consequently,g-C3N4 exhibited better thermomechanical and tribological properties.The result of this work is expected to provide a new kind of functional filler for enhancing the tribological properties of polymer composites.

Immobilization of Proteases on Nanoflower-Like Metal Organic Framework

Proteases have been widely used in pharmaceutics and industry,and an economic,convenient and robust procedure for protease immobilization is of high interest.In this study,we report immobilization of proteases by the nanoflower-like zeolitic imidazole framework (nfZIF).Using trypsin,protease K,and Glu-C as model enzymes,we show nfZIF represents an excellent material for protease immobilization,and the resulting [email protected] composites exhibit activities comparable to or even higher than the free proteases in solution.The [email protected] composites are stable in high temperature and organic solvents,and retain almost fully active after several reaction cycles.Our studies demonstrate the great potential of nfZIF in the immobilization of proteases,which could be of interest in various industrial applications.