借助等离子体引发丙烯酸-3-(全氟-3-甲基丁基)-2-羟丙酯在碳纳米管表面的诱导接枝聚合,得到新型氟化碳纳米管(f-CNTs),进而制备出f-CNT/热塑性聚氨酯(f-CNT/TPU)复合弹性体。结果表明,氟化虽不改变CNTs的表面结构,但却在其组成中引入了...借助等离子体引发丙烯酸-3-(全氟-3-甲基丁基)-2-羟丙酯在碳纳米管表面的诱导接枝聚合,得到新型氟化碳纳米管(f-CNTs),进而制备出f-CNT/热塑性聚氨酯(f-CNT/TPU)复合弹性体。结果表明,氟化虽不改变CNTs的表面结构,但却在其组成中引入了含量10.40%的氟元素。经含氟高聚物接枝碳纳米管的平均直径约为30 nm,均匀分散于TPU基体中。随着f-CNTs含量的增加,所得f-CNT/TPU复合弹性体的拉伸强度和断裂伸长率均呈现先增后减趋势。当f-CNTs加入量为0.3%时,该复合弹性体的拉伸强度和断裂伸长率分别高达36.5 M Pa和630%,较纯TPU弹性体分别提高40.4%和26.5%,并初步探讨了可能的增强增韧机理。而随着f-CNTs含量的增加,f-CNT/TPU复合弹性体的表面自由能由27.3 m N/m降低至9.9 m N/m,表现出优异的表面性能。展开更多
In deep ground engineering,the use of high-strength and high-toughness steels for rock bolt can significantly improve its energy absorption capacity.However,the mechanisms and effects of rock loading conditions on thi...In deep ground engineering,the use of high-strength and high-toughness steels for rock bolt can significantly improve its energy absorption capacity.However,the mechanisms and effects of rock loading conditions on this kind of high energy-absorbing steel for rock bolt remain immature.In this study,taking Muzhailing highway tunnel as the background,physically based crystal plasticity simulations were performed to understand the effect of rock loading rate and pretension on the deformation behaviors of twinning induced plasticity(TWIP)steel used for rock bolt.The material physical connecting to the underlying microscopic mechanisms of dislocation glide and deformation twinning were incorporated in numerical modeling.The rock loading conditions were mimicked by the real-time field monitoring data of the NPR bolt/cable equipment installed on the tunnel surrounding rock surface.The results indicate that the bolt rod exhibits pronounced deformation-softening behavior with decrease of the loading rate.There is also a sound deformation-relaxation phenomenon induced by the dramatic decrease of loading rate after pre-tensioning.The high pretension(>600 MPa or 224 k N)can help bolt rod steel resist deformation-softening behavior,especially at low loading rate(<10~(-1)MPa/s or 10~(-2)kN/s).The loading rate was found to be a significant factor affecting deformation-softening behavior while the pretension was found to be the major parameter accounting for the deformation-relaxation scenario.The results provide the theoretical basis and technical support for practical applications.展开更多
In this study,laboratory testing and numerical simulation methods are used to investigate the mechanical behavior and perform fracture prediction of a novel high-strength and high-toughness steel with a negative Poiss...In this study,laboratory testing and numerical simulation methods are used to investigate the mechanical behavior and perform fracture prediction of a novel high-strength and high-toughness steel with a negative Poisson's ratio(NPR)effect under combined tensile-shear loading conditions.A test device capable of meeting different tensile-shear combination test angles is designed and manufactured,wherein the mechanical experiments on the NPR(Negative Poisson's Ratio)steel specimens are carried out at various testing angles.Q235 steel and MG400 steel are used as experimental control groups.The results show that the mechanical deformation of NPR steel is significantly better than that of Q235 steel and MG400 steel.Its tensile-shear test curve has no yield plateau and it has quasi-ideal elastic-plastic mechanical properties.The loading direction gradually changes from tension-dominated to shear-dominated as the tension-shear angle increases,and the strength and deformation of the specimens show a decreasing trend.Based on the laboratory test results,a finite element numerical model of NPR steel is established.A series of numerical simulations are carried out under the conditions of different tension and shear angles and the average stress triaxiality and fracture strain data are obtained.The fracture data of NPR steel are fitted using the Johnson-Cook fracture criterion,and the Johnson-Cook fracture parameters under the tensile-shear test conditions of NPR steel are thus obtained.The numerical simulation verifies that the fracture model can accurately predict the tensile-shear fracture behavior of NPR steel.展开更多
The effect of notch volume on the mechanical behavior of a novel high-strength and high-toughness steel with negative Poisson’s ratio effect(called NPR steel)was studied.First,the quasi-static tensile test of NPR ste...The effect of notch volume on the mechanical behavior of a novel high-strength and high-toughness steel with negative Poisson’s ratio effect(called NPR steel)was studied.First,the quasi-static tensile test of NPR steel with different notch volumes was carried out,and its failure characteristics and mechanical properties parameters were studied.Then,the modified Johnson-Cook(J-C)constitutive model with coupled notch volume ratio was proposed.The model was validated based on three-dimensional finite element numerical simulations.The results show that the engineering stress–strain curve of NPR steel has no yield platform,and has the mechanical properties of high strength,high elongation,and high energy absorption.Notch volume significantly affects the mechanical properties of NPR steel.The elongation,yield strength,tensile strength,and energy absorption characteristics of steel bar gradually decrease with the increase in notch volume.The notch volume ratio V^{*},a characteristic parameter describing the notch volume of reinforcement,is defined,and the quantitative relationship between this parameter and mechanical parameters is established,which can accurately characterize the mechanical properties of specimens with different notch volume ratios.Based on the true stress–strain curves with different notch volume ratios,a constitutive model with modified Johnson-Cook model parameters is proposed.The finite element results show that the modified J-C model can accurately fit the quasi-static tensile mechanical behavior of NPR steel.展开更多
文摘借助等离子体引发丙烯酸-3-(全氟-3-甲基丁基)-2-羟丙酯在碳纳米管表面的诱导接枝聚合,得到新型氟化碳纳米管(f-CNTs),进而制备出f-CNT/热塑性聚氨酯(f-CNT/TPU)复合弹性体。结果表明,氟化虽不改变CNTs的表面结构,但却在其组成中引入了含量10.40%的氟元素。经含氟高聚物接枝碳纳米管的平均直径约为30 nm,均匀分散于TPU基体中。随着f-CNTs含量的增加,所得f-CNT/TPU复合弹性体的拉伸强度和断裂伸长率均呈现先增后减趋势。当f-CNTs加入量为0.3%时,该复合弹性体的拉伸强度和断裂伸长率分别高达36.5 M Pa和630%,较纯TPU弹性体分别提高40.4%和26.5%,并初步探讨了可能的增强增韧机理。而随着f-CNTs含量的增加,f-CNT/TPU复合弹性体的表面自由能由27.3 m N/m降低至9.9 m N/m,表现出优异的表面性能。
基金the National Natural Science Foundation of China(Grant No.41941018)the Science and Technology Major Project of Gansu Province(Grant No.19ZD2GA005)the Research Institute for Deep Underground Science and Engineering Foundation(Grant No.XD2021023)。
文摘In deep ground engineering,the use of high-strength and high-toughness steels for rock bolt can significantly improve its energy absorption capacity.However,the mechanisms and effects of rock loading conditions on this kind of high energy-absorbing steel for rock bolt remain immature.In this study,taking Muzhailing highway tunnel as the background,physically based crystal plasticity simulations were performed to understand the effect of rock loading rate and pretension on the deformation behaviors of twinning induced plasticity(TWIP)steel used for rock bolt.The material physical connecting to the underlying microscopic mechanisms of dislocation glide and deformation twinning were incorporated in numerical modeling.The rock loading conditions were mimicked by the real-time field monitoring data of the NPR bolt/cable equipment installed on the tunnel surrounding rock surface.The results indicate that the bolt rod exhibits pronounced deformation-softening behavior with decrease of the loading rate.There is also a sound deformation-relaxation phenomenon induced by the dramatic decrease of loading rate after pre-tensioning.The high pretension(>600 MPa or 224 k N)can help bolt rod steel resist deformation-softening behavior,especially at low loading rate(<10~(-1)MPa/s or 10~(-2)kN/s).The loading rate was found to be a significant factor affecting deformation-softening behavior while the pretension was found to be the major parameter accounting for the deformation-relaxation scenario.The results provide the theoretical basis and technical support for practical applications.
基金supported by the Postdoctoral Fellowship Program of CPSF under Grant Number GZB20240556.
文摘In this study,laboratory testing and numerical simulation methods are used to investigate the mechanical behavior and perform fracture prediction of a novel high-strength and high-toughness steel with a negative Poisson's ratio(NPR)effect under combined tensile-shear loading conditions.A test device capable of meeting different tensile-shear combination test angles is designed and manufactured,wherein the mechanical experiments on the NPR(Negative Poisson's Ratio)steel specimens are carried out at various testing angles.Q235 steel and MG400 steel are used as experimental control groups.The results show that the mechanical deformation of NPR steel is significantly better than that of Q235 steel and MG400 steel.Its tensile-shear test curve has no yield plateau and it has quasi-ideal elastic-plastic mechanical properties.The loading direction gradually changes from tension-dominated to shear-dominated as the tension-shear angle increases,and the strength and deformation of the specimens show a decreasing trend.Based on the laboratory test results,a finite element numerical model of NPR steel is established.A series of numerical simulations are carried out under the conditions of different tension and shear angles and the average stress triaxiality and fracture strain data are obtained.The fracture data of NPR steel are fitted using the Johnson-Cook fracture criterion,and the Johnson-Cook fracture parameters under the tensile-shear test conditions of NPR steel are thus obtained.The numerical simulation verifies that the fracture model can accurately predict the tensile-shear fracture behavior of NPR steel.
基金supports by the National Key Research and Development Program of China(Grant No.2016YFC0600901)the Fundamental Research Funds for the Central Universities(Grant No.2015QB02)are greatly acknowledged.
文摘The effect of notch volume on the mechanical behavior of a novel high-strength and high-toughness steel with negative Poisson’s ratio effect(called NPR steel)was studied.First,the quasi-static tensile test of NPR steel with different notch volumes was carried out,and its failure characteristics and mechanical properties parameters were studied.Then,the modified Johnson-Cook(J-C)constitutive model with coupled notch volume ratio was proposed.The model was validated based on three-dimensional finite element numerical simulations.The results show that the engineering stress–strain curve of NPR steel has no yield platform,and has the mechanical properties of high strength,high elongation,and high energy absorption.Notch volume significantly affects the mechanical properties of NPR steel.The elongation,yield strength,tensile strength,and energy absorption characteristics of steel bar gradually decrease with the increase in notch volume.The notch volume ratio V^{*},a characteristic parameter describing the notch volume of reinforcement,is defined,and the quantitative relationship between this parameter and mechanical parameters is established,which can accurately characterize the mechanical properties of specimens with different notch volume ratios.Based on the true stress–strain curves with different notch volume ratios,a constitutive model with modified Johnson-Cook model parameters is proposed.The finite element results show that the modified J-C model can accurately fit the quasi-static tensile mechanical behavior of NPR steel.
文摘本文通过板坯连铸、钢板控轧控冷(TMCP)、固溶淬火回火(QT)工业生产流程,开发低C含Cu高强韧NV-F690特厚(厚度t为80 mm)船体和海洋平台用钢板.使用SEM,EBSD和TEM分别研究了淬火(Q)态和QT态钢板的精细组织,测试了距离钢板表面t/4处(高冷却速率)和芯部t/2处(低冷却速率)的室温硬度和拉伸性能,在-60和-80℃下进行了Charpy冲击(Charpy V notch,CVN)示波实验.结果表明,淬火速率较大有利于板条组织形成和提高大角度晶界比例,t/4处的组织为板条状贝氏体(LB),板条间存在细小片状马氏体/奥氏体(M/A)组元,晶粒间大角度晶界(>15°)体积分数为67.5%;t/2处的组织为粒状贝氏体(GB)+LB,大角度晶界体积分数为63.0%;Q态下的LB具有高位错密度,但晶粒内不存在Cu析出相.经过650℃回火150 min,钢板的强韧性匹配优良,低温下呈韧性断裂,大量含Cu弥散沉淀相在基体组织内析出.t/2处的M/A组元分解为Cr-Mo碳化物,贝氏体板条宽度为0.4μm,大角度晶界分数为62.5%;t/4处的LB板条回复,板条内存在与基体取向差较大的亚晶,大角度晶界分数提高到71.7%,板条平均宽度为0.2μm.在-80℃下,NV-F690钢板t/4处的韧性高于t/2处的韧性.随着纤维断裂位移的增大,韧窝断裂区比例和韧窝尺寸逐渐增大,NV-F690钢低温Charpy冲击能量逐渐提高.
