The high variability of shock in terrorist attacks poses a threat to people's lives and properties,necessitating the development of more effective protective structures.This study focuses on the angle gradient and...The high variability of shock in terrorist attacks poses a threat to people's lives and properties,necessitating the development of more effective protective structures.This study focuses on the angle gradient and proposes four different configurations of concave hexagonal honeycomb structures.The structures'macroscopic deformation behavior,stress-strain relationship,and energy dissipation characteristics are evaluated through quasi-static compression and Hopkinson pressure bar impact experiments.The study reveals that,under varying strain rates,the structures deform starting from the weak layer and exhibit significant interlayer separation.Additionally,interlayer shear slip becomes more pronounced with increasing strain rate.In terms of quasi-static compression,symmetric gradient structures demonstrate superior energy absorption,particularly the symmetric negative gradient structure(SNG-SMS)with a specific energy absorption of 13.77 J/cm~3.For dynamic impact,unidirectional gradient structures exhibit exceptional energy absorption,particularly the unidirectional positive gradient honeycomb structure(UPG-SML)with outstanding mechanical properties.The angle gradient design plays a crucial role in determining the structure's stability and deformation mode during impact.Fewer interlayer separations result in a more pronounced negative Poisson's ratio effect and enhance the structure's energy absorption capacity.These findings provide a foundation for the rational design and selection of seismic protection structures in different strain rate impact environments.展开更多
The static tests of nine traditional and bird beak square hollow structure(SHS) T-joints with different β values and connection types under axial compression at brace end were carried out. Experimental test schemes, ...The static tests of nine traditional and bird beak square hollow structure(SHS) T-joints with different β values and connection types under axial compression at brace end were carried out. Experimental test schemes, failure modes of specimens, jack load-vertical displacement curves, jack load-deformation of chord and strain intensity distribution curves of joints were presented. The effects of β and connection types on axial compression property of joints were studied. The results show that the ultimate axial compression capacity of common bird beak SHS T-joints and diamond bird beak SHS T-joints is larger than that of traditional SHS T-joint specimens with big values of β. The ultimate axial compression capacity of diamond bird beak SHS T-joints is larger than that of common bird beak SHS T-joints. As β increases, the increase of the ultimate axial compression capacity of diamond bird beak SHS T-joints over that of common bird beak joints grows. The ultimate axial compression capacity and the initial axial stiffness of all kinds of joints increase as β increases, and the initial axial stiffness of the diamond bird beak SHS T-joints is the largest. The ductilities of common bird beak and diamond bird beak SHS T-joints increase as β increases, but the ductility of the traditional SHS T-joints decreases as β increases.展开更多
Stability analyses of perfect and imperfect cylindrical shells under axial compression and torsion were presented. Finite element method for the stability analysis of perfect cylindrical shells was put forward through...Stability analyses of perfect and imperfect cylindrical shells under axial compression and torsion were presented. Finite element method for the stability analysis of perfect cylindrical shells was put forward through comparing critical loads and the first buckling modes with those obtained through theoretical analysis. Two typical initial defects, non-circularity and uneven thickness distribution, were studied. Critical loads decline with the increase of non-circularity, which exist in imperfect cylindrical shells under both axial compression and torsion. Non-circularity defect has no effect on the first buckling mode when cylindrical shell is under torsion. Unfortunately, it has a completely different buckling mode when cylindrical shell is under axial compression. Critical loads decline with the increase of thickness defect amplitude, which exist in imperfect cylindrical shells under both axial compression and torsion, too. A greater wave number is conducive to the stability of cylindrical shells. The first buckling mode of imperfect cylindrical shells under torsion maintains its original shape, but it changes with wave number when the cylindrical shell is under axial compression.展开更多
In this paper, the mechanical behavior of acrylic polymers at elevated temperature was investigated. Four acrylic polymers were tested at high strain rate by using compression Hopkinson bar and at quasi-static strain ...In this paper, the mechanical behavior of acrylic polymers at elevated temperature was investigated. Four acrylic polymers were tested at high strain rate by using compression Hopkinson bar and at quasi-static strain rate by using an Instron servo hydraulic axial testing machine with the testing temperature from 218K to 393K. The results show that the mechanical property of acrylic polymers depends heavily on the testing temperature. The yield stress and Young's modulus were found to decrease with increasing temperature at low strain rate. At very low temperature, the materials display typical brittle fracture; however their plasticity improves remarkably at high temperatures. The predictions of the mechanical behavior including the effect of temperature and strain rate using a proposed theoretical model have a good agreement with experimental results.展开更多
基金financially supported by National Natural Science Foundation of China,China (Grant No.52022012)National Key R&D Program for Young Scientists of China,China (Grant No.2022YFC3080900)。
文摘The high variability of shock in terrorist attacks poses a threat to people's lives and properties,necessitating the development of more effective protective structures.This study focuses on the angle gradient and proposes four different configurations of concave hexagonal honeycomb structures.The structures'macroscopic deformation behavior,stress-strain relationship,and energy dissipation characteristics are evaluated through quasi-static compression and Hopkinson pressure bar impact experiments.The study reveals that,under varying strain rates,the structures deform starting from the weak layer and exhibit significant interlayer separation.Additionally,interlayer shear slip becomes more pronounced with increasing strain rate.In terms of quasi-static compression,symmetric gradient structures demonstrate superior energy absorption,particularly the symmetric negative gradient structure(SNG-SMS)with a specific energy absorption of 13.77 J/cm~3.For dynamic impact,unidirectional gradient structures exhibit exceptional energy absorption,particularly the unidirectional positive gradient honeycomb structure(UPG-SML)with outstanding mechanical properties.The angle gradient design plays a crucial role in determining the structure's stability and deformation mode during impact.Fewer interlayer separations result in a more pronounced negative Poisson's ratio effect and enhance the structure's energy absorption capacity.These findings provide a foundation for the rational design and selection of seismic protection structures in different strain rate impact environments.
基金Projects(51278209,51478047)supported by the National Natural Science Foundation of ChinaProject(2014FJ-NCET-ZR03)supported by the Program for New Century Excellent Talents in Fujian Provincial Universities,China+1 种基金Project(JA13005)supported by the Incubation Program for Excellent Young Science and Technology Talents in Fujian Provincial Universities,ChinaProject(ZQN-PY110)supported by the Young and Middle-aged Academic Staff of Huaqiao University,China
文摘The static tests of nine traditional and bird beak square hollow structure(SHS) T-joints with different β values and connection types under axial compression at brace end were carried out. Experimental test schemes, failure modes of specimens, jack load-vertical displacement curves, jack load-deformation of chord and strain intensity distribution curves of joints were presented. The effects of β and connection types on axial compression property of joints were studied. The results show that the ultimate axial compression capacity of common bird beak SHS T-joints and diamond bird beak SHS T-joints is larger than that of traditional SHS T-joint specimens with big values of β. The ultimate axial compression capacity of diamond bird beak SHS T-joints is larger than that of common bird beak SHS T-joints. As β increases, the increase of the ultimate axial compression capacity of diamond bird beak SHS T-joints over that of common bird beak joints grows. The ultimate axial compression capacity and the initial axial stiffness of all kinds of joints increase as β increases, and the initial axial stiffness of the diamond bird beak SHS T-joints is the largest. The ductilities of common bird beak and diamond bird beak SHS T-joints increase as β increases, but the ductility of the traditional SHS T-joints decreases as β increases.
基金Project(11102163)supported by the National Natural Science Foundation of ChinaProjects(JC20110218,JC20110260)supported by Foundation for Fundamental Research of Northwestern Polytechnical University,China
文摘Stability analyses of perfect and imperfect cylindrical shells under axial compression and torsion were presented. Finite element method for the stability analysis of perfect cylindrical shells was put forward through comparing critical loads and the first buckling modes with those obtained through theoretical analysis. Two typical initial defects, non-circularity and uneven thickness distribution, were studied. Critical loads decline with the increase of non-circularity, which exist in imperfect cylindrical shells under both axial compression and torsion. Non-circularity defect has no effect on the first buckling mode when cylindrical shell is under torsion. Unfortunately, it has a completely different buckling mode when cylindrical shell is under axial compression. Critical loads decline with the increase of thickness defect amplitude, which exist in imperfect cylindrical shells under both axial compression and torsion, too. A greater wave number is conducive to the stability of cylindrical shells. The first buckling mode of imperfect cylindrical shells under torsion maintains its original shape, but it changes with wave number when the cylindrical shell is under axial compression.
文摘In this paper, the mechanical behavior of acrylic polymers at elevated temperature was investigated. Four acrylic polymers were tested at high strain rate by using compression Hopkinson bar and at quasi-static strain rate by using an Instron servo hydraulic axial testing machine with the testing temperature from 218K to 393K. The results show that the mechanical property of acrylic polymers depends heavily on the testing temperature. The yield stress and Young's modulus were found to decrease with increasing temperature at low strain rate. At very low temperature, the materials display typical brittle fracture; however their plasticity improves remarkably at high temperatures. The predictions of the mechanical behavior including the effect of temperature and strain rate using a proposed theoretical model have a good agreement with experimental results.
