As metallic foams used for energy absorption in the automotive and aerospace industries, recently invented lotus-type porous metals are viewed as potential energy absorbers. Yet, solid conclusion on their eligibility ...As metallic foams used for energy absorption in the automotive and aerospace industries, recently invented lotus-type porous metals are viewed as potential energy absorbers. Yet, solid conclusion on their eligibility as energy absorbers is still in question, particularly when compression is in the direction perpendicular to the axial orientation of cylindrical pores. In this work, the energy absorption of lotus-type porous coppers in the perpendicular direction is investigated at strain rates from 0.001 s^（-1） to^2400 s^（-1）. The energy absorption capacity and the energy absorption efficiency are calculated to be4–16 k J/kg and 0.32–0.7, respectively, slightly inferior to metal foams and the same porous solid compressed in the parallel direction due to the shortened extent of the plateau stress region. The deformation mechanism is examined experimentally in conjunction with finite element modeling. Both suggest that gradual squeeze and collapse of pores are the mechanisms accommodating the energy absorption. The deformation is generally evenly distributed over pore ligaments and independent of strain rate.展开更多
In the present study,the performance of reinforced concrete tunnel(RCT)under internal water pressure is evaluated by using nonlinear finite element analysis and surrogate models.Several parameters,including the compre...In the present study,the performance of reinforced concrete tunnel(RCT)under internal water pressure is evaluated by using nonlinear finite element analysis and surrogate models.Several parameters,including the compressive and tensile strength of concrete,the size of the longitudinal reinforcement bar,the transverse bar diameter,and the internal water pre ssure,are considered as the input variables.Based on the levels of variables,36 mix designs are selected by the Taguchi method,and 12 mix designs are proposed in this study.Carbon fiber reinforced concrete(CFRC)or glass fiber reinforced concrete(GFRC)is considered for simulating these 12 samples.Principal component regression(PCR),Multi Ln equation regression(MLnER),and gene expression programming(GEP)are employed for predicting the percentage of damaged surfaces(PDS)of the RCT,the effective tensile plastic strain(ETPS),the maximum deflection of the RCT,and the deflection of crown of RCT.The error terms and statistical parameters,including the maximum positive and negative errors,mean absolute percentage error(MAPE),root mean square error(RMSE),coefficient of determination,and normalized square error(NMSE),are utili zed to evaluate the accuracy of the models.Based on the results,GEP performs better than other models in predicting the outputs.The results sh ow that the internal water pressure and the mechanical properties of concrete have the most effect on the damag e and deflection of the RCT.展开更多
基金financial support from the National Natural Science Foundation of China (Grant No. 50904004)
文摘As metallic foams used for energy absorption in the automotive and aerospace industries, recently invented lotus-type porous metals are viewed as potential energy absorbers. Yet, solid conclusion on their eligibility as energy absorbers is still in question, particularly when compression is in the direction perpendicular to the axial orientation of cylindrical pores. In this work, the energy absorption of lotus-type porous coppers in the perpendicular direction is investigated at strain rates from 0.001 s^（-1） to^2400 s^（-1）. The energy absorption capacity and the energy absorption efficiency are calculated to be4–16 k J/kg and 0.32–0.7, respectively, slightly inferior to metal foams and the same porous solid compressed in the parallel direction due to the shortened extent of the plateau stress region. The deformation mechanism is examined experimentally in conjunction with finite element modeling. Both suggest that gradual squeeze and collapse of pores are the mechanisms accommodating the energy absorption. The deformation is generally evenly distributed over pore ligaments and independent of strain rate.
文摘In the present study,the performance of reinforced concrete tunnel(RCT)under internal water pressure is evaluated by using nonlinear finite element analysis and surrogate models.Several parameters,including the compressive and tensile strength of concrete,the size of the longitudinal reinforcement bar,the transverse bar diameter,and the internal water pre ssure,are considered as the input variables.Based on the levels of variables,36 mix designs are selected by the Taguchi method,and 12 mix designs are proposed in this study.Carbon fiber reinforced concrete(CFRC)or glass fiber reinforced concrete(GFRC)is considered for simulating these 12 samples.Principal component regression(PCR),Multi Ln equation regression(MLnER),and gene expression programming(GEP)are employed for predicting the percentage of damaged surfaces(PDS)of the RCT,the effective tensile plastic strain(ETPS),the maximum deflection of the RCT,and the deflection of crown of RCT.The error terms and statistical parameters,including the maximum positive and negative errors,mean absolute percentage error(MAPE),root mean square error(RMSE),coefficient of determination,and normalized square error(NMSE),are utili zed to evaluate the accuracy of the models.Based on the results,GEP performs better than other models in predicting the outputs.The results sh ow that the internal water pressure and the mechanical properties of concrete have the most effect on the damag e and deflection of the RCT.
