The linear evolution of a resistive wall mode(RWM)with magnetic shears was analytically studied in a cylindrical geometry.The incompressible magnetohydrodynamic(MHD)equations were solved by the Fourier analysis method...The linear evolution of a resistive wall mode(RWM)with magnetic shears was analytically studied in a cylindrical geometry.The incompressible magnetohydrodynamic(MHD)equations were solved by the Fourier analysis method,and various equilibrium magnetic fields were considered.The shear in the magnetic field had an unstable effect on the linear evolution of the RWM.The linear growth rate increased obviously with increase of the magnetic shear rate for higher magnetic shears.Slow plasma rotation could stabilize the RWM with low magnetic shears,but the plasma rotation could not stabilize the RWM with high magnetic shears.The stabilizing effects of the wall conductivity on the RWM are more efficient for lager magnetic shear.展开更多
Based on the analysis of heat radiation intensity from flame, a new mathematical model ofthe tube-wall temperatmp of heated tubes is developed by taking down-fired, upright-tube cylindricalfurnace for example. The pro...Based on the analysis of heat radiation intensity from flame, a new mathematical model ofthe tube-wall temperatmp of heated tubes is developed by taking down-fired, upright-tube cylindricalfurnace for example. The proposed mathematical model can be employed to indicate both the positionand size of the hot spot at fire-facing wall of heated tube of combustion chamber, and is characteristicof simplicity and efficiency If coupled with thermoelectric couple or infrared viewer, the presentedlocation method of combustion hot spot can offer engineers very valuable proposal to keep furnacerunning more safely The same is true for any other type of tubular furnaces.展开更多
In this paper, a theory of thick-walled shells is established by means of Hellinger-Reissner's variational principle, with displacement and stress assumptions. The displacements are expanded into power series of t...In this paper, a theory of thick-walled shells is established by means of Hellinger-Reissner's variational principle, with displacement and stress assumptions. The displacements are expanded into power series of the thickness coordinate. Only the first four and the first three terms are used for the displacements parallel and normal to the middle surface respectively. The normal extruding and transverse shear stresses are assumed to be cubic polynomials and to satisfy the boundary stress conditions on the outer and inner surfaces of the shell. The governing equations and boundary conditions are derived by means of variational principle. As an example, a thick-walled cylindrical shell is disscussed with the theory proposed. Furthermore, a photoelastic experiment has been carried out, and the results are in fair agreement with the computations.展开更多
High load-bearing efficiency is one of the advantages of biological structures after the evolution of billions of years. Biomimicking from nature may offer the potential for lightweight design. In the viewpoint ofrnec...High load-bearing efficiency is one of the advantages of biological structures after the evolution of billions of years. Biomimicking from nature may offer the potential for lightweight design. In the viewpoint ofrnechanics properties, the culm of bamboo comprises of two types of cells and the number of the vascular bundles takes a gradient of distribution. A three-point bending test was carried out to measure the elastic modulus. Results show that the elastic modulus of bamboo decreases gradually from the periphery towards the centre. Based on the structural characteristics of bamboo, a bionic cylindrical structure was designed to mimic the gradient distribution of vascular bundles and parenchyma cells. The buckling resistance of the bionic structure was compared with that of a traditional shell of equal mass under axial pressure by finite element simulations. Results show that the load-bearing capacity of bionic shell is increased by 124.8%. The buckling mode of bionic structure is global buckling while that of the conventional shell is local buckling.展开更多
Earth buildings are common types of structures in most rural areas in all developing countries.Catastrophic failure and destruction of these structures under seismic loads always result in loss of human lives and econ...Earth buildings are common types of structures in most rural areas in all developing countries.Catastrophic failure and destruction of these structures under seismic loads always result in loss of human lives and economic losses.Wall is an important load-bearing component of raw soil buildings.In this paper,a novel approach is proposed to improve the strength and ductility of adobe walls.Three types of analyses,material properties,mechanical properties,and dynamic properties,are carried out for the seismic performance assessment of the adobe walls.These performed studies include that,material properties of the earth cylinder block,mechanical properties of adobe walls under quasi-static loads,and dynamic performance of adobe walls excited by seismic waves.On investigation of material properties,eighteen cylindrical specimens with a diameter of 100 mm and a height of 110 mm were divided into three groups for compressive,tensile,and split pull strength tests,respectively.The results of the three groups of tests showed that the yield strength ratios of compressive,tensile,and shear strength were about 1:0.3:0.2.In order to study the performance of structural components,three 1/3 scale model raw soil walls with a dimension of 1,200 mm in width,1,000 mm in height,and 310 mm in thickness were tested under cyclic loading.The average wall capacity of the wall obtained by the test was about 13.5 kN and the average displacement angle was about 1/135.The numerical simulation experiment is used to explore the mechanism of structural failure.A three-dimensional finite element model is established by choosing the material parameters based on the above test outcomes.The accuracy of the numerical simulation experiment is verified by simulation and comparison of the above quasi-static test results.Further,the collapse process of raw soil wall under a seismic wave is simulated for exploring the response and damage mechanism of structure.Based on those systematically analyzed,some useful suggested guidelines are provided for improving the seismic performance of raw soil buildings.展开更多
Cylindrical rings with thin wall and high web ribs(CRTWHWR)are widely used as the key load bearing structures such as rocket body and space station cabin in aerospace field.However,it is still difficult to efficiently...Cylindrical rings with thin wall and high web ribs(CRTWHWR)are widely used as the key load bearing structures such as rocket body and space station cabin in aerospace field.However,it is still difficult to efficiently manufacture CRTWHWR with high performance because of their extreme geometry with thin-walled skins,high web ribs and large size.In this paper,a novel radial envelope forming process is put forward to efficiently achieve the plastic forming of CRTWHWR with high performance.Firstly,the principle of radial envelope forming process is clarified.Then,an efficient design method for the tool motion and geometry is proposed based on the reverse envelope principle,i.e.,CRTWHWR is adopted to reversely envelope the tool and thus the tool which does not interfere with CRTWHWR can be efficiently obtained in a single operation.Finally,a reasonable 3D FE model of the radial envelope forming process of CRTWHWR is established and the radial envelope forming mechanism of CRTWHWR is comprehensively revealed.Through the FE simulation and experiments with material of plastic mud,a typical CRTWHWR with diameter of 300 mm,axial height of 192 mm,the maximum rib height of 25 mm,the minimum rib thickness of 3 mm and skin thickness of 5 mm is radial envelope formed,i.e.,the ratio of the maximum rib height to the minimum rib thickness reaches 8.33,the ratio of the maximum rib height to skin thickness reaches 5 and the ratio of diameter to the minimum rib thickness reaches 100.The above results verify that the proposed radial envelope forming process has great potentials in efficiently manufacturing CRTWHWR with extreme geometry.展开更多
基金National Science Foundation of Shangong Province of China(No.ZR2016AM30)National Natural Science Foundation of China(No.11875290)Foundation of Shandong Province Higher Educational Science and Technology Program,China(No.J15LN15)
文摘The linear evolution of a resistive wall mode(RWM)with magnetic shears was analytically studied in a cylindrical geometry.The incompressible magnetohydrodynamic(MHD)equations were solved by the Fourier analysis method,and various equilibrium magnetic fields were considered.The shear in the magnetic field had an unstable effect on the linear evolution of the RWM.The linear growth rate increased obviously with increase of the magnetic shear rate for higher magnetic shears.Slow plasma rotation could stabilize the RWM with low magnetic shears,but the plasma rotation could not stabilize the RWM with high magnetic shears.The stabilizing effects of the wall conductivity on the RWM are more efficient for lager magnetic shear.
基金This project is supported by National Natural Science Foundation of China(No.50175081).
文摘Based on the analysis of heat radiation intensity from flame, a new mathematical model ofthe tube-wall temperatmp of heated tubes is developed by taking down-fired, upright-tube cylindricalfurnace for example. The proposed mathematical model can be employed to indicate both the positionand size of the hot spot at fire-facing wall of heated tube of combustion chamber, and is characteristicof simplicity and efficiency If coupled with thermoelectric couple or infrared viewer, the presentedlocation method of combustion hot spot can offer engineers very valuable proposal to keep furnacerunning more safely The same is true for any other type of tubular furnaces.
文摘In this paper, a theory of thick-walled shells is established by means of Hellinger-Reissner's variational principle, with displacement and stress assumptions. The displacements are expanded into power series of the thickness coordinate. Only the first four and the first three terms are used for the displacements parallel and normal to the middle surface respectively. The normal extruding and transverse shear stresses are assumed to be cubic polynomials and to satisfy the boundary stress conditions on the outer and inner surfaces of the shell. The governing equations and boundary conditions are derived by means of variational principle. As an example, a thick-walled cylindrical shell is disscussed with the theory proposed. Furthermore, a photoelastic experiment has been carried out, and the results are in fair agreement with the computations.
基金National Natural Science Foundation of China (Grant No. 50575008)the Aeronautical Science Foundation of China (Grant No. 05B01004)
文摘High load-bearing efficiency is one of the advantages of biological structures after the evolution of billions of years. Biomimicking from nature may offer the potential for lightweight design. In the viewpoint ofrnechanics properties, the culm of bamboo comprises of two types of cells and the number of the vascular bundles takes a gradient of distribution. A three-point bending test was carried out to measure the elastic modulus. Results show that the elastic modulus of bamboo decreases gradually from the periphery towards the centre. Based on the structural characteristics of bamboo, a bionic cylindrical structure was designed to mimic the gradient distribution of vascular bundles and parenchyma cells. The buckling resistance of the bionic structure was compared with that of a traditional shell of equal mass under axial pressure by finite element simulations. Results show that the load-bearing capacity of bionic shell is increased by 124.8%. The buckling mode of bionic structure is global buckling while that of the conventional shell is local buckling.
文摘Earth buildings are common types of structures in most rural areas in all developing countries.Catastrophic failure and destruction of these structures under seismic loads always result in loss of human lives and economic losses.Wall is an important load-bearing component of raw soil buildings.In this paper,a novel approach is proposed to improve the strength and ductility of adobe walls.Three types of analyses,material properties,mechanical properties,and dynamic properties,are carried out for the seismic performance assessment of the adobe walls.These performed studies include that,material properties of the earth cylinder block,mechanical properties of adobe walls under quasi-static loads,and dynamic performance of adobe walls excited by seismic waves.On investigation of material properties,eighteen cylindrical specimens with a diameter of 100 mm and a height of 110 mm were divided into three groups for compressive,tensile,and split pull strength tests,respectively.The results of the three groups of tests showed that the yield strength ratios of compressive,tensile,and shear strength were about 1:0.3:0.2.In order to study the performance of structural components,three 1/3 scale model raw soil walls with a dimension of 1,200 mm in width,1,000 mm in height,and 310 mm in thickness were tested under cyclic loading.The average wall capacity of the wall obtained by the test was about 13.5 kN and the average displacement angle was about 1/135.The numerical simulation experiment is used to explore the mechanism of structural failure.A three-dimensional finite element model is established by choosing the material parameters based on the above test outcomes.The accuracy of the numerical simulation experiment is verified by simulation and comparison of the above quasi-static test results.Further,the collapse process of raw soil wall under a seismic wave is simulated for exploring the response and damage mechanism of structure.Based on those systematically analyzed,some useful suggested guidelines are provided for improving the seismic performance of raw soil buildings.
基金the National Natural Science Foundation of China(No.U2037204)the 111 Project(B17034)+1 种基金Innovative Research Team Development Program of Ministry of Education of China(No.IRT17R83)the National Natural Science Foundation of China(No.52005375)for the support given to this research。
文摘Cylindrical rings with thin wall and high web ribs(CRTWHWR)are widely used as the key load bearing structures such as rocket body and space station cabin in aerospace field.However,it is still difficult to efficiently manufacture CRTWHWR with high performance because of their extreme geometry with thin-walled skins,high web ribs and large size.In this paper,a novel radial envelope forming process is put forward to efficiently achieve the plastic forming of CRTWHWR with high performance.Firstly,the principle of radial envelope forming process is clarified.Then,an efficient design method for the tool motion and geometry is proposed based on the reverse envelope principle,i.e.,CRTWHWR is adopted to reversely envelope the tool and thus the tool which does not interfere with CRTWHWR can be efficiently obtained in a single operation.Finally,a reasonable 3D FE model of the radial envelope forming process of CRTWHWR is established and the radial envelope forming mechanism of CRTWHWR is comprehensively revealed.Through the FE simulation and experiments with material of plastic mud,a typical CRTWHWR with diameter of 300 mm,axial height of 192 mm,the maximum rib height of 25 mm,the minimum rib thickness of 3 mm and skin thickness of 5 mm is radial envelope formed,i.e.,the ratio of the maximum rib height to the minimum rib thickness reaches 8.33,the ratio of the maximum rib height to skin thickness reaches 5 and the ratio of diameter to the minimum rib thickness reaches 100.The above results verify that the proposed radial envelope forming process has great potentials in efficiently manufacturing CRTWHWR with extreme geometry.
