The quantitative relation between notched impact strength and fractured surfaceroughness of polymer materials at different testing temperature was investigated withdifferent polymer. The resultsshow thatthe notched im...The quantitative relation between notched impact strength and fractured surfaceroughness of polymer materials at different testing temperature was investigated withdifferent polymer. The resultsshow thatthe notched impactstrength σiof polymer materialsincreasedlinearly with theincrease offractured surface roughness parameter R Sin the case ofbrittle fracture atlowertesting temperature . Butthe variation ofimpact strength depends onboth R Sand the plastic deformation area in the case of ductile fracture at higher testingtemperature. The relation between σiand R Sat higher testing temperature could be dividedinto three models according to different polymer materials and their fracture mechanism .展开更多
The wall surface roughness renders a significant impact on ventilation of roadways and cross-sectional wind speed distribution.Herein,the wall roughness(Ra)in the roadway has been defined theoretically.Moreover,three-...The wall surface roughness renders a significant impact on ventilation of roadways and cross-sectional wind speed distribution.Herein,the wall roughness(Ra)in the roadway has been defined theoretically.Moreover,three-center arched roadway models for different situations are established based on the normal distribution of roof roughness.The influence of inlet velocity,roof roughness and roadway height on wind speed distribution is systematically studied by using Fluent software.At Ra=0.1 m,the simulation results reveal that the wind speed is negatively related to the distance from the wall to the point where 80%of the central wind speed is reached(DA).Also,the wind speed distribution is significantly influenced by increasing the roof roughness.However,the wind speed distribution becomes asymmetric at Ra=0.2 m and 0.3 m.Furthermore,the low-speed area(v≤1 m/s)started to concentrate on the roof with the increase of roadway height.Overall,an Ra value of<0.1 m can reduce the influence of wall roughness on wind speed distribution of the roadway,which is suggested in practical applications.展开更多
文摘The quantitative relation between notched impact strength and fractured surfaceroughness of polymer materials at different testing temperature was investigated withdifferent polymer. The resultsshow thatthe notched impactstrength σiof polymer materialsincreasedlinearly with theincrease offractured surface roughness parameter R Sin the case ofbrittle fracture atlowertesting temperature . Butthe variation ofimpact strength depends onboth R Sand the plastic deformation area in the case of ductile fracture at higher testingtemperature. The relation between σiand R Sat higher testing temperature could be dividedinto three models according to different polymer materials and their fracture mechanism .
基金Project(2017YFC0602901)supported by the National Key Research and Development Program of ChinaProject(2019zzts988)supported by the Postgraduate Independent Exploration and Innovative Project of Central South University,China。
文摘The wall surface roughness renders a significant impact on ventilation of roadways and cross-sectional wind speed distribution.Herein,the wall roughness(Ra)in the roadway has been defined theoretically.Moreover,three-center arched roadway models for different situations are established based on the normal distribution of roof roughness.The influence of inlet velocity,roof roughness and roadway height on wind speed distribution is systematically studied by using Fluent software.At Ra=0.1 m,the simulation results reveal that the wind speed is negatively related to the distance from the wall to the point where 80%of the central wind speed is reached(DA).Also,the wind speed distribution is significantly influenced by increasing the roof roughness.However,the wind speed distribution becomes asymmetric at Ra=0.2 m and 0.3 m.Furthermore,the low-speed area(v≤1 m/s)started to concentrate on the roof with the increase of roadway height.Overall,an Ra value of<0.1 m can reduce the influence of wall roughness on wind speed distribution of the roadway,which is suggested in practical applications.
