The purpose of this paper is to consider 1D Riemann shock tube to investigate the formation and propagation of compression waves leading to formation, propagation and reflection of 1D normal shocks using simplified ma...The purpose of this paper is to consider 1D Riemann shock tube to investigate the formation and propagation of compression waves leading to formation, propagation and reflection of 1D normal shocks using simplified mathematical models commonly used in the published work as well as using complete mathematical models based on Conservation and Balance Laws (CBL) of classical continuum mechanics and constitutive theories for compressible viscous medium derived using entropy inequality and representation theorem. This work is aimed at resolving compression waves, the shock structure, shock formation, propagation and reflection of fully formed shocks. Evolutions obtained from the mathematical models always satisfy differentiability requirements in space and time dictated by the highest order of the derivatives of the dependent variables in the mathematical models investigated. All solutions reported in this paper including boundary conditions and initial conditions are always analytic. Solutions of the mathematical models are obtained using the space-time finite element method in which the space-time integral forms are space-time variationally consistent ensuring unconditionally stable computations during the entire evolution. Solution for a space-time strip or slab is calculated and is time marched upon convergence to obtain complete evolution for the desired space-time domain, thus ensuring time accurate evolutions. The space-time local approximation over a space-time element of a space-time strip or slab is p-version hierarchical with higher-order global differentiability in space and time, i.e., we consider scalar product approximation spaces in which k = (k<sub>1</sub>, k<sub>2</sub>) are the order of the space in space and time and p = (p<sub>1</sub>, p<sub>2</sub>) are p-levels of the approximations in space and time. Model problem studies are presented for different mathematical models and are compared with solutions obtained from the complete mathematical model based on CBL and constitutive theories for viscous compressible medium to illustrate the deficiencies and shortcomings of the simplified and approximate models in simulating correct physics of normal shocks.展开更多
The experimental investigations on the effect of the fly ash particle size, velocity, impingement angle, and feed rate were done with an emphasis on the effect of erosion on annealed SA 210 GrA1 （A） and normalized S...The experimental investigations on the effect of the fly ash particle size, velocity, impingement angle, and feed rate were done with an emphasis on the effect of erosion on annealed SA 210 GrA1 （A） and normalized SA 210 GrA1 （N） carbon steel economizer-tube materials. Erosion rates were evaluated with different impingement angles ranging from 15° to 90°, at four different velocities of 32.5, 35, 37.5, and 40 m/s, and at four different feed rates of fly ash particles of 2, 4, 6 and 8 g/min. The erodent used was fly ash particles, sizes ranging from 50-250 μm of irregular shapes. Erosion rate is found to be the maximum at the impingement angle of 30°. Erosion rates of the carbon steel tube in different heat treatment conditions, annealed and normalized, at a constant velocity of 32.5 m/s with different angles were studied. In all cases of feed rates, impingement angles, particle sizes, and velocities of fly ash particles, it has been found that the erosion rate of the annealed tube is less than that of the normalized tube. Empirical correlations for erosion rate relating the velocity, size, feed rate, and impingement angle of the particles and elongation property of the target materials were arrived. Morphologies of the eroded surface were examined by scanning electron microscope （SEM）.展开更多
Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of t...Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of the tensile steel tube is 0.252 during the using stage,and the average crack space of beams depends on the ratio of the sum of the bottom chord steel tube's outside diameter and the secondary bottom chord steel tube's section area to the effective tensile concrete area. The coefficient of uneven crack distribution is 1.68 and the formula for the calculation of crack width is established. Test results indicate that the ultimate stress increment of unbonded tendon in the beams decreases in linearity with the increase of the composite reinforcement index β0. The pure bending region of beams accords with the plane section assumption from loading to failure. The calculation formula of ultimate stress increment of the unbonded tendon and the method to calculate the bearing capacity of normal section of beams have been presented. Besides,the method to calculate the stiffness of this sort of beams is brought forward as well.展开更多
Computer model is developed for non-steady and steady-state process of thin-walled tube extension by the rigid punch with curved profile. Rigid-plastic membrane shell theory with quadratic yield criterion is used. Tub...Computer model is developed for non-steady and steady-state process of thin-walled tube extension by the rigid punch with curved profile. Rigid-plastic membrane shell theory with quadratic yield criterion is used. Tube material normal anisotropy, work hardening, wall thickness variation and friction effects are considered. FORTRAN programs of the model predict distributions of the thickness, meridian stress, yield stress and pressure along curved generator of deformed tube and the tube extension force versus punch displacement relation. Model predictions are correlated with experimental data.展开更多
The effect of normal force on fretting wear behavior of zirconium alloy tube mated with grid dimple in simulated primary water of pressurized water reactor nuclear power plant was investigated.Results showed that the ...The effect of normal force on fretting wear behavior of zirconium alloy tube mated with grid dimple in simulated primary water of pressurized water reactor nuclear power plant was investigated.Results showed that the maximum wear depth,wear volume and wear coefficient of Zr alloy tube in simulated primary water at 315℃ gradually increased with increasing normal force,while the friction coefficient gradually decreased.Fretting process could be divided into four stages according to the variation of friction coefficient during test.When normal force exceeds 30 N,the fretting regime would transition from gross slip regime to partial slip regime after 3×10^(7 )cycles.Delamination was aggravated with increasing normal force,while abrasive wear became slighter.A thicker third-body layer with monoclinic ZrO_(2) was formed by the tribo-sintering mechanism under higher normal force.In addition,the schematic evolution processes of delamination and third-body layer formation were displayed according to morphology observation.展开更多
文摘The purpose of this paper is to consider 1D Riemann shock tube to investigate the formation and propagation of compression waves leading to formation, propagation and reflection of 1D normal shocks using simplified mathematical models commonly used in the published work as well as using complete mathematical models based on Conservation and Balance Laws (CBL) of classical continuum mechanics and constitutive theories for compressible viscous medium derived using entropy inequality and representation theorem. This work is aimed at resolving compression waves, the shock structure, shock formation, propagation and reflection of fully formed shocks. Evolutions obtained from the mathematical models always satisfy differentiability requirements in space and time dictated by the highest order of the derivatives of the dependent variables in the mathematical models investigated. All solutions reported in this paper including boundary conditions and initial conditions are always analytic. Solutions of the mathematical models are obtained using the space-time finite element method in which the space-time integral forms are space-time variationally consistent ensuring unconditionally stable computations during the entire evolution. Solution for a space-time strip or slab is calculated and is time marched upon convergence to obtain complete evolution for the desired space-time domain, thus ensuring time accurate evolutions. The space-time local approximation over a space-time element of a space-time strip or slab is p-version hierarchical with higher-order global differentiability in space and time, i.e., we consider scalar product approximation spaces in which k = (k<sub>1</sub>, k<sub>2</sub>) are the order of the space in space and time and p = (p<sub>1</sub>, p<sub>2</sub>) are p-levels of the approximations in space and time. Model problem studies are presented for different mathematical models and are compared with solutions obtained from the complete mathematical model based on CBL and constitutive theories for viscous compressible medium to illustrate the deficiencies and shortcomings of the simplified and approximate models in simulating correct physics of normal shocks.
文摘The experimental investigations on the effect of the fly ash particle size, velocity, impingement angle, and feed rate were done with an emphasis on the effect of erosion on annealed SA 210 GrA1 （A） and normalized SA 210 GrA1 （N） carbon steel economizer-tube materials. Erosion rates were evaluated with different impingement angles ranging from 15° to 90°, at four different velocities of 32.5, 35, 37.5, and 40 m/s, and at four different feed rates of fly ash particles of 2, 4, 6 and 8 g/min. The erodent used was fly ash particles, sizes ranging from 50-250 μm of irregular shapes. Erosion rate is found to be the maximum at the impingement angle of 30°. Erosion rates of the carbon steel tube in different heat treatment conditions, annealed and normalized, at a constant velocity of 32.5 m/s with different angles were studied. In all cases of feed rates, impingement angles, particle sizes, and velocities of fly ash particles, it has been found that the erosion rate of the annealed tube is less than that of the normalized tube. Empirical correlations for erosion rate relating the velocity, size, feed rate, and impingement angle of the particles and elongation property of the target materials were arrived. Morphologies of the eroded surface were examined by scanning electron microscope （SEM）.
文摘Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of the tensile steel tube is 0.252 during the using stage,and the average crack space of beams depends on the ratio of the sum of the bottom chord steel tube's outside diameter and the secondary bottom chord steel tube's section area to the effective tensile concrete area. The coefficient of uneven crack distribution is 1.68 and the formula for the calculation of crack width is established. Test results indicate that the ultimate stress increment of unbonded tendon in the beams decreases in linearity with the increase of the composite reinforcement index β0. The pure bending region of beams accords with the plane section assumption from loading to failure. The calculation formula of ultimate stress increment of the unbonded tendon and the method to calculate the bearing capacity of normal section of beams have been presented. Besides,the method to calculate the stiffness of this sort of beams is brought forward as well.
文摘Computer model is developed for non-steady and steady-state process of thin-walled tube extension by the rigid punch with curved profile. Rigid-plastic membrane shell theory with quadratic yield criterion is used. Tube material normal anisotropy, work hardening, wall thickness variation and friction effects are considered. FORTRAN programs of the model predict distributions of the thickness, meridian stress, yield stress and pressure along curved generator of deformed tube and the tube extension force versus punch displacement relation. Model predictions are correlated with experimental data.
基金supported by the CNNC Science Fund for Talented Young Scholars,Youth Innovation Promotion Assessment CAS(2022187)the IMR Innovation Fund(No.2021-PY10)the open-ended fund of the CAS Key laboratory of Nuclear Materials and Safety Assessment(Institute of Metal Research,Chinese Academy of Sciences,China)(No.2020NMSAKF01).
文摘The effect of normal force on fretting wear behavior of zirconium alloy tube mated with grid dimple in simulated primary water of pressurized water reactor nuclear power plant was investigated.Results showed that the maximum wear depth,wear volume and wear coefficient of Zr alloy tube in simulated primary water at 315℃ gradually increased with increasing normal force,while the friction coefficient gradually decreased.Fretting process could be divided into four stages according to the variation of friction coefficient during test.When normal force exceeds 30 N,the fretting regime would transition from gross slip regime to partial slip regime after 3×10^(7 )cycles.Delamination was aggravated with increasing normal force,while abrasive wear became slighter.A thicker third-body layer with monoclinic ZrO_(2) was formed by the tribo-sintering mechanism under higher normal force.In addition,the schematic evolution processes of delamination and third-body layer formation were displayed according to morphology observation.
