High-static-low-dynamic stiffness (HSLDS) vibration isolators have been demonstrated to be an effective means of attenuating low-frequency vibrations, and may be utilized for ship shafting applications to mitigate tor...High-static-low-dynamic stiffness (HSLDS) vibration isolators have been demonstrated to be an effective means of attenuating low-frequency vibrations, and may be utilized for ship shafting applications to mitigate torsional vibration. This paper presents the construction of a highly compact HSLDS torsional vibration isolator by connecting positive and negative stiffness components in paral lel. Based on mechanical model analysis, the restoring torque of negative stiffness components is de rived from their springs and connecting rods, while that of positive stiffness components is obtained through their circular section flexible rods. The quasizero stiffness characteristics of the HSLDS iso lator are achieved through a combination of static structural simulation and experimental test. The tor sional vibration isolation performance is assessed by means of numerical simulation and theory analy sis. Finally, the frequency-sweep vibration test is conducted. The test results indicate that the HSLDS torsional vibration isolator exhibits superior low-frequency isolation performance compared to its linear counterpart, rendering it a promising solution for mitigating low-frequency torsional vi bration in ship shafting.展开更多
Bone is a multi-phase,non-homogeneous material that exhibits strain rate sensitivity,and it may fail under compression,tension,torsion,or a combination of these loading.The mechanical properties of cortical bone with ...Bone is a multi-phase,non-homogeneous material that exhibits strain rate sensitivity,and it may fail under compression,tension,torsion,or a combination of these loading.The mechanical properties of cortical bone with strain rate effect under compression and tension have been obtained through the application of the split Hopkinson pressure/tension bar technique,but no such studies have been reported for determining the strain rate behavior properties of bony materials under torsion.In this study,the shear stress-strain curves with the rate-dependent cortical bone subjected to dynamic torsional loading were first obtained using a torsional split Hopkinson bar system.Based on the experiments,an improved mathematical model consisting of elastic,viscoelastic,and viscoplastic components was used to identify the material parameters of the cortical bone.Detailed material properties are derived through constitutive relations.The results may assist researchers in developing more accurate models of cortical bone behavior under different load conditions.展开更多
This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional sh...This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional shear apparatus was utilized to conduct tests on remolded samples under both normal and frozen conditions to investigate the mechanical properties and deformation behavior of loess under complex stress conditions. The results indicate significant differences in the internal changes of soil particles, unfrozen water, and relative positions in soil samples under normal and frozen conditions, leading to noticeable variations in strength and strain development.In frozen state, loess experiences primarily compressive failure with a slow growth of cracks, while at normal temperature, it predominantly exhibits shear failure. With the increase in the principal stress angle, the deformation patterns of the soil samples under different conditions become essentially consistent, gradually transitioning from compression to extension, accompanied by a reduction in axial strength. The gradual increase in the principal stress axis angle(α) reduces the strength of the generalized shear stress and shear strain curves.Under an increasing α, frozen soil exhibits strain-hardening characteristics, with the maximum shear strength occurring at α = 45°. The intermediate principal stress coefficient(b) also significantly impacts the strength of frozen soil, with an increasing b resulting in a gradual decrease in generalized shear stress strength. This study provides a reference for comprehensively exploring the mechanical properties of soil under traffic load and a reliable theoretical basis for the design and maintenance of roadbeds.展开更多
The microstructure, texture characteristics and torsion ability of two kinds of steel wires were investigated. The eutectoid steel wires were produced by hot and cold drawing with severe deformation. The torsinability...The microstructure, texture characteristics and torsion ability of two kinds of steel wires were investigated. The eutectoid steel wires were produced by hot and cold drawing with severe deformation. The torsinability of steel wires was measured under two cases, i.e. there exists either fiber texture or circular texture. The results showed that the torsional behavior of the steel wires was affected by their textures and microstructures. The {110}<110> circular texture weakened the torsion ability of the wires. The torsion fracture behavior of {110}<110> texture wires is related to the fact that only two slip systems were activated under simple shear strain deformation.展开更多
文摘High-static-low-dynamic stiffness (HSLDS) vibration isolators have been demonstrated to be an effective means of attenuating low-frequency vibrations, and may be utilized for ship shafting applications to mitigate torsional vibration. This paper presents the construction of a highly compact HSLDS torsional vibration isolator by connecting positive and negative stiffness components in paral lel. Based on mechanical model analysis, the restoring torque of negative stiffness components is de rived from their springs and connecting rods, while that of positive stiffness components is obtained through their circular section flexible rods. The quasizero stiffness characteristics of the HSLDS iso lator are achieved through a combination of static structural simulation and experimental test. The tor sional vibration isolation performance is assessed by means of numerical simulation and theory analy sis. Finally, the frequency-sweep vibration test is conducted. The test results indicate that the HSLDS torsional vibration isolator exhibits superior low-frequency isolation performance compared to its linear counterpart, rendering it a promising solution for mitigating low-frequency torsional vi bration in ship shafting.
基金supported by the National Natural Science Foundation of China(Grant Nos.12372363,12272254,and 12072219)the special fund for Science and Technology Innovation Teams of Shanxi Province(Grant No.202204051002006)+1 种基金the Natural Science Foundation of Shanxi Province(Grant No.202203021211170)the project of Key Laboratory of Impact and Safety Engineering(Ningbo University),Ministry of Education(Grant No.CJ202202)。
文摘Bone is a multi-phase,non-homogeneous material that exhibits strain rate sensitivity,and it may fail under compression,tension,torsion,or a combination of these loading.The mechanical properties of cortical bone with strain rate effect under compression and tension have been obtained through the application of the split Hopkinson pressure/tension bar technique,but no such studies have been reported for determining the strain rate behavior properties of bony materials under torsion.In this study,the shear stress-strain curves with the rate-dependent cortical bone subjected to dynamic torsional loading were first obtained using a torsional split Hopkinson bar system.Based on the experiments,an improved mathematical model consisting of elastic,viscoelastic,and viscoplastic components was used to identify the material parameters of the cortical bone.Detailed material properties are derived through constitutive relations.The results may assist researchers in developing more accurate models of cortical bone behavior under different load conditions.
基金This work was supported by the National Natural Science Foundation of China(Nos.42161026&41801046)the Natural Science Foundation of Qinghai Province(No.2023-ZJ-934M)the Youth Research Foundation of Qinghai University(No.2022-QGY-5).
文摘This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional shear apparatus was utilized to conduct tests on remolded samples under both normal and frozen conditions to investigate the mechanical properties and deformation behavior of loess under complex stress conditions. The results indicate significant differences in the internal changes of soil particles, unfrozen water, and relative positions in soil samples under normal and frozen conditions, leading to noticeable variations in strength and strain development.In frozen state, loess experiences primarily compressive failure with a slow growth of cracks, while at normal temperature, it predominantly exhibits shear failure. With the increase in the principal stress angle, the deformation patterns of the soil samples under different conditions become essentially consistent, gradually transitioning from compression to extension, accompanied by a reduction in axial strength. The gradual increase in the principal stress axis angle(α) reduces the strength of the generalized shear stress and shear strain curves.Under an increasing α, frozen soil exhibits strain-hardening characteristics, with the maximum shear strength occurring at α = 45°. The intermediate principal stress coefficient(b) also significantly impacts the strength of frozen soil, with an increasing b resulting in a gradual decrease in generalized shear stress strength. This study provides a reference for comprehensively exploring the mechanical properties of soil under traffic load and a reliable theoretical basis for the design and maintenance of roadbeds.
基金This work is supported by key project of the National Nat-ural Science Foundation of China(Grant No.50231030)the National High Technology Research and Development Pro-gram of China(Grant No.2003AA331030)the Teaching and Research Award Program for Outstanding Young Teach-ers in Higher Education Institutions.
文摘The microstructure, texture characteristics and torsion ability of two kinds of steel wires were investigated. The eutectoid steel wires were produced by hot and cold drawing with severe deformation. The torsinability of steel wires was measured under two cases, i.e. there exists either fiber texture or circular texture. The results showed that the torsional behavior of the steel wires was affected by their textures and microstructures. The {110}<110> circular texture weakened the torsion ability of the wires. The torsion fracture behavior of {110}<110> texture wires is related to the fact that only two slip systems were activated under simple shear strain deformation.
