CN111475935A - Damage assessment method for high-temperature high-speed airflow erosion concrete material - Google Patents
Damage assessment method for high-temperature high-speed airflow erosion concrete material Download PDFInfo
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Abstract
The invention provides a damage evaluation method for a high-temperature and high-speed air flow erosion concrete material, which comprises the following steps of: step one, establishing a concrete material model through Digmat-FE software, and carrying out grid division; step two, carrying out thinning treatment on the grid in ANSA software; step three, transient heat conduction calculation is carried out in Abaqus software; calculating pneumatic shearing force, air hole internal pressure, airflow vertical load and concrete surface thermal convection coefficient; step five, performing transient heat-solid coupling calculation in Abaqus software; and step six, obtaining a conclusion based on the calculation data result. The evaluation method designed by the invention is scientific and reasonable, preferably adopts various software for cooperation, has good modeling simulation effect, clear and easy conclusion acquisition and scientific and reliable evaluation result, and can be popularized and used.
Description
Technical Field
The invention relates to the technical field of concrete performance research, in particular to a damage evaluation method for a high-temperature high-speed air flow erosion concrete material.
Background
Buildings of concrete material have an irreplaceable important role in social development. And the research on the high-temperature resistance and anti-explosion performance of the concrete material building has important guiding significance for the building safety. The concrete erosion damage caused by the high-temperature and high-speed airflow can provide technical reference for the specified concrete technical standard, and concrete materials can be conveniently subjected to more detailed quality evaluation.
However, a reliable and efficient research method is not yet available. At present, researchers have few researches on mechanical erosion damage mechanisms of concrete under pure meteorological conditions, generally simplify complex concrete structures to a certain extent for improving the modeling efficiency of aggregate mesoscopic models, and are insufficient in transient heat transfer research results under high-temperature and high-speed airflow impact.
Disclosure of Invention
The invention aims to solve the technical problem of providing a damage assessment method for a high-temperature and high-speed air flow erosion concrete material aiming at the defects of the prior art, the method is scientific, reasonable, convenient and quick, can intuitively and systematically obtain the erosion resistance of the high-temperature and high-speed air flow in the concrete, provides technical support for actual production and application, and has important scientific research value and economic value.
In order to solve the technical problems, the invention adopts the technical scheme that: a damage assessment method for high-temperature high-speed air flow erosion concrete materials is characterized by comprising the following steps:
step one, modeling through a Digmat-FE software, and carrying out grid division to obtain a concrete material preliminary grid model;
step two, carrying out refinement processing on the preliminary grid model in ANSA software to obtain a concrete material research model;
loading high-temperature high-speed airflow to the concrete material research model in Abaqus software;
fourthly, calculating the vertical airflow load, the thermal convection coefficient of the concrete surface, the air hole internal pressure and the pneumatic shearing force of the loaded concrete material research model;
and fifthly, performing transient heat-solid coupling calculation on the concrete material research model in the Abaqus software, and calculating a stress cloud chart of the concrete material research model, so as to calculate the heat transfer depth, the displacement cloud chart, the damaged area and the mass loss rate, thereby judging the damage degree of the high-temperature high-speed air flow erosion concrete material.
Preferably, the specific steps of modeling by Digmat-FE software in the step one are as follows:
s101, establishing a three-dimensional random aggregate mesoscopic model in Digmat-FE software, wherein the aggregate in the random aggregate mesoscopic model is in an ellipsoid shape and contains ellipsoid air holes;
s102, setting the volume proportion of aggregates in the aggregate meso-scale model to be 70%, setting the long axis size of the aggregates to be 5-20mm, setting the volume proportion fraction of air holes in the aggregate meso-scale model to be 1%, and setting the long axis size of the air holes to be 1-5 mm;
s103, setting a certain gap between the air holes and the aggregate model, wherein the gap is not overlapped and is completely contained in a three-dimensional random aggregate mesoscopic model matrix and randomly distributed;
and S104, setting a preliminary grid size on the basis of the three-dimensional random aggregate mesoscopic model obtained in the S103 to obtain a preliminary grid model.
Preferably, the specific operation steps of the second step are as follows:
s201, exporting the preliminary grid model obtained in the S104 to Ansa software in an inp format;
s202, defining the elastic modulus, Poisson ratio, specific heat capacity, thermal expansion coefficient, density and thermal conductivity coefficient of the aggregate and the concrete;
s203, adding a concrete model into the preliminary grid model in Ansa software to enable aggregate to be embedded in concrete and subdividing the grid, wherein the aggregate and the concrete model grid share nodes to form a relatively fixed relation, and a concrete material research model is formed.
Preferably, the concrete material research model is simulated and embedded into a ground foundation pit, the periphery of the concrete material research model is respectively fixed in X, Y directions, the ground is fixed in a Z direction, the upper surface of the concrete material research model is impacted by high-speed airflow and forms an angle α with the upper plane of the concrete material research model, the initial temperature of the concrete material research model is set to be 20 ℃, and the airflow impact can be simplified into an impact force P;
preferably, the specific steps of the fourth step include:
s401, calculating the vertical load of the airflow: decomposing the impact force P into vertical force PbAnd horizontal shear force fiThe impact force P is set as P ═ mv, m is the mass flow rate of the gas per second, here, 6.376kg/s is taken, and v is the effective discharge speed of the gas flow; vertical load Pb＝mvsinα；
S402, concrete surface thermal convection coefficient:
the impact heat transfer of the high-temperature high-speed airflow comprises heat convection between the hot airflow and the upper surface of the concrete and heat conduction inside the concrete;
on the fluid side, a cylindrical channel for discharging high-temperature and high-speed airflow is defined as an exhaust channel, the heat transfer process between the hot airflow in the exhaust channel and the wall surface of a concrete material research model is regarded as the turbulent forced convection heat transfer of a non-circular channel, and the Nussel number of the heat transfer process is calculated by the Gnielinski formula
For gas
In the formula, l is the length of the exhaust passage; d is the equivalent diameter of the exhaust passage; f is the Darcy resistance coefficient of turbulent flow in the exhaust passage; re is Reynolds number, PrfPrandtl constant for hot gas flow;
equivalent diameter of exhaust passage
In the above formula, A is the flow cross section of the hot airflow in the exhaust passage; c is the circumference of the exhaust passage, namely the part of the exhaust passage wall contacted with the hot air flow;
f＝(1.82lgRe-1.64)-2
in the formula, ρlIs the fluid density; u. of∞Is the incoming flow velocity; μ is hydrodynamic viscosity, and μ ═ ρ ν; x is the characteristic length, namely the equivalent diameter of the exhaust passage;
wherein ν is the kinematic viscosity of the fluid; a is the fluid thermal conductivity coefficient.
After Nu is determined, the convective heat transfer coefficient between the hot air flow and the wall surface of the exhaust passage can be obtained according to the definition formula;
wherein λ is the fluid thermal conductivity;
simultaneous upper type get
Heat convection formula q ═ h | Tf-Tw|；
On the solid side of the exhaust duct, i.e. inside the concrete, heat conduction mainly occurs, heat flows from places with high temperature to places with low heat, and according to the Fourier law, the expression of the heat flow density is
Wherein q is the heat flow density unit W/(m)2) (ii) a λ is the heat transfer coefficient in W/(m ℃); t is the temperature unit;
effective heat transfer coefficient lambda of unsaturated concreteeffThe relationship with temperature and pore water saturation is as follows
In the above formulad(T) is the heat conduction coefficient of concrete in dry environment, and the expression is
λd(T)＝λd0(1+Aλ(T-T0))
Wherein, T0Taking 298.15K as a reference temperature; lambda [ alpha ]d0Taking 1.67W/mK; a. theλTake-1.017 × 10-3K-1；ρlIs the density of water; rhosThe density of the concrete; n is the porosity of the concrete;
in a three-dimensional Cartesian coordinate system, assuming that the temperature of one point in the concrete is T, the heat transfer isotropy lambda of the concrete material is lambdaeffThe differential equation of the three-dimensional unsteady heat conduction in the concrete structure without the internal heat source is as follows:
in the formula, rho is the density of concrete; c is the specific heat capacity of the concrete under constant pressure;
the heat conduction differential equation is a mathematical expression describing the commonality of the heat conduction process, in order to obtain the transient temperature field distribution of the concrete, the temperature distribution and the thermal boundary condition of the initial moment of the concrete are required to be given according to the actual condition, and for the unsteady heat transfer condition, the initial condition of the concrete heat transfer calculation is as follows:
T(x,y,z,0)＝T0
in the formula, ToIs the initial temperature of the concrete;
the heat convection coefficient h and the hot air flow of the boundary surface of the fluid and the concrete are knownTemperature T offNamely:
calculating the convective heat transfer coefficient between the hot air flow and the wall surface (concrete) of the exhaust passage, taking the convective heat transfer coefficient as a thermal boundary condition, and loading the thermal boundary condition to a concrete side interface to obtain a concrete temperature field;
s403, calculating the pore internal pressure: saturated steam pressure PvsCalculated by empirical formula given by Hyland and Wexler
Wherein C is8＝-5.8x103，C9＝1.3915，C10＝-4.8640×102，C11＝4.1765×10-5，C12＝-1.445,C136.5460, when T ≧ 674.3K, Pvs＝22.09MPa；
S404, calculating the pneumatic shearing force: the viscous forces of the mould surface need to be obtained by summing the friction forces of all wall elements, i.e.:
wherein: fv is the total viscous force; f. ofiIs the viscous friction of the wall surface unit i; c. CfiIs the viscous friction coefficient of the wall surface unit i; qAiIs the local dynamic pressure of the wall surface unit i; a. theiIs the area of the wall cell i;
coefficient of viscous friction c of unit ifiCalculating by adopting a reference temperature method based on local flow field parameters, namely:
ρe、ue、μedensity, velocity, respectively, of the outer edge of the boundary layerAnd a dynamic viscosity coefficient, x being the length of the flow line emanating from the leading edge of the slab;
local pressure Q of unit iAiKinetic pressure at reference temperature T:
QAi＝0.5ρue 2
the viscous friction of unit i can then be expressed as:
the frictional force fiIs tangential to the flow line, i.e. the velocity direction of the local wall surface. Let the tangent unit vector be taui＝(τx，τy，τz) Friction force f of unit iiThe three components in the rectangular coordinate system (x, y, z) are:
fix＝fiτx
fiy＝fiτy
fiz＝fiτz
the total viscous force of the surface, in a rectangular coordinate system, can then be expressed as:
s405, dividing the concrete material research model into an impact area and an impact area according to different impact areas, and compiling a working condition table.
Preferably, the specific steps of the fifth step are as follows:
s501, the calculation result in the fourth step is divided into two parts, wherein the first part is an impact area and a model stress cloud chart, a heat transfer depth, a displacement cloud chart, a damage area and a quality loss rate which are analyzed after the impact area under the impact of high-temperature airflow; the second part is that when observing the change along with the air flow impact angle, the air flow temperature and the air flow impact speed in the impact area, a model stress cloud chart, a heat transfer depth, a displacement cloud chart, a damage area and a quality loss rate are analyzed;
s502, after the impact area and the impact area are respectively arranged, calculating according to a formula in the step four to obtain curves of the change of the pneumatic shearing force, the vertical load and the thermal convection coefficient along with time; then calculating a transient temperature field of the concrete material research model, importing the data of pneumatic shearing force, vertical load and thermal convection coefficient into calculation and analysis to obtain the temperature in the air vent, wherein the temperature in the air vent is the maximum value of the surface temperature of the concrete material research model, establishing a thermal-solid coupling field by the internal pressure of the air vent and the temperature of the air vent to obtain a stress cloud chart, then removing the failure unit and determining the quality of the failure unit to obtain the quality loss rate of the concrete material research model, measuring the volume of the failure unit, dividing the volume of the failure unit by the surface area of the concrete to obtain the average depth of a surface falling layer, finally obtaining the damage degree comparison of the concrete with different grades by setting the compressive strength standards of the different concrete grades, and finally obtaining the simulation calculation results of four regions;
s503, in the impact area, changing the impact angle of the high-temperature high-speed airflow, the temperature of the high-temperature high-speed airflow and the speed of the high-temperature high-speed airflow by controlling a variable method, and respectively calculating the loss degree of the impact area under different conditions, wherein the calculation method is the same as that provided by the S502;
and S504, comparing and analyzing the calculation results obtained by integrating the S502 and the S503 to obtain the damage condition conclusion of the concrete under the high-temperature and high-speed airflow erosion.
Compared with the prior art, the invention has the following advantages:
1. the method is scientific, reasonable, convenient and quick, can intuitively and systematically obtain the erosion resistance of the high-temperature and high-speed airflow in the concrete, provides technical support for actual production and application, and has important scientific research value and economic value.
2. The method can be used for evaluating the mechanism research of the erosion damage of the concrete material when the building of the concrete material is impacted by high-temperature and high-speed airflow, such as an explosive fire, and analyzing and summarizing the erosion damage law under different speeds, temperatures and pressures.
3. The invention can provide ideas and foundations for building a three-dimensional random aggregate mesoscopic model of a concrete material and provides a reliable research method for the damage mechanism of the concrete under high-temperature high-speed airflow impact.
4. The invention respectively uses the Digmat-FE software, ANSA software and Abaqus software, can fully utilize the advantages and characteristics of each software, establishes a three-dimensional random concrete aggregate meso-scale model for erosion simulation research of high-temperature high-speed airflow, and has good modeling effect and high simulation calculation speed.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
FIG. 1 is a flow chart of the operation of the present invention.
Fig. 2 is a schematic view of the load loading of the present invention.
FIG. 3 is a schematic view of the thermal convection loading of the present invention.
FIG. 4 is a schematic view of the dynamic-thermal shock effect of hot gas flow in the present invention.
FIG. 5 is a schematic heat transfer diagram of the exhaust stack of the present invention.
FIG. 6 is a schematic diagram showing the saturated vapor pressure and the temperature in the pores in the present invention.
FIG. 7 is a table of calculated operating conditions in the present invention.
FIG. 8 is a graph of aerodynamic shear force over time in accordance with the present invention.
Fig. 9 is a graph of vertical load versus time in the present invention.
FIG. 10 is a graph showing the change of the thermal convection coefficient with time in the present invention.
FIG. 11 is a cloud of transient heat conduction temperature profiles for the impingement zone of the present invention.
FIG. 12 is a cloud of equivalent stresses for the impact zone of the model of the present invention.
FIG. 13 is a cloud of equivalent displacements of the impact zone of the model in the present invention.
FIG. 14 is a cloud of cell stresses with the impact zone of the C30 model removed for failure in the present invention.
FIG. 15 is a graph showing the concrete volume loss rate according to the present invention as a function of time.
FIG. 16 is a table summarizing the results of the impact zone and the calculation after the impact zone in the present invention.
FIG. 17 is a summary of the results of the impact zone of the present invention at various impact angles.
FIG. 18 is a graph of the average depth of exfoliation layers over time for different gas flow temperatures in accordance with the present invention.
FIG. 19 is a summary of the results of the impact zone of the present invention at different impact temperatures.
FIG. 20 is a graph of mass loss rate over time for different air flow rates in the present invention.
FIG. 21 is a summary of the results of the impact zone of the present invention at various impact velocities.
Detailed Description
As shown in fig. 1, the present invention comprises the steps of:
step one, modeling through a Digmat-FE software, and carrying out grid division to obtain a concrete material preliminary grid model;
step two, carrying out refinement processing on the preliminary grid model in ANSA software to obtain a concrete material research model;
loading high-temperature high-speed airflow to the concrete material research model in Abaqus software;
fourthly, calculating the vertical airflow load, the thermal convection coefficient of the concrete surface, the air hole internal pressure and the pneumatic shearing force of the loaded concrete material research model;
and fifthly, performing transient heat-solid coupling calculation on the concrete material research model in the Abaqus software, and calculating a stress cloud chart of the concrete material research model, so as to calculate the heat transfer depth, the displacement cloud chart, the damaged area and the mass loss rate, thereby judging the damage degree of the high-temperature high-speed air flow erosion concrete material.
Preferably, the specific steps of modeling by Digmat-FE software in the step one are as follows:
s101, establishing a three-dimensional random aggregate mesoscopic model in Digmat-FE software, wherein the aggregate in the random aggregate mesoscopic model is in an ellipsoid shape and contains ellipsoid air holes;
s102, setting the volume proportion of aggregates in the aggregate meso-scale model to be 70%, setting the long axis size of the aggregates to be 5-20mm, setting the volume proportion fraction of air holes in the aggregate meso-scale model to be 1%, and setting the long axis size of the air holes to be 1-5 mm;
s103, setting a certain gap between the air holes and the aggregate model, wherein the gap is not overlapped and is completely contained in a three-dimensional random aggregate mesoscopic model matrix and randomly distributed;
and S104, setting a preliminary grid size on the basis of the three-dimensional random aggregate mesoscopic model obtained in the S103 to obtain a preliminary grid model.
In this embodiment, the specific operation steps of the second step are as follows:
s201, exporting the preliminary grid model obtained in the S104 to Ansa software in an inp format, drawing the outer surface of the preliminary grid model into a triangular shell grid in Ansa, defining a body grid according to the shell grid, so that the grid division time can be effectively saved, and the grid quality can also be guaranteed, wherein the total number of units of the whole model is 1165108, the total number of nodes is 254371, the type of aggregate units is C3D4T, the number of units is 263476, the number of nodes is 73745, the type of concrete units is C3D4T, the number of units is 901632, and the number of nodes is 180626;
s202, defining the elastic modulus of the aggregate as 41Gpa, the Poisson ratio as 0.3, the specific heat capacity as 840J/(kg DEG C), the thermal expansion coefficient as 6E-6 and the density as 1800kg/m3And a thermal conductivity of 1.16W/(m)2K); the concrete is defined as having an elastic modulus of 30GPa, a Poisson's ratio of 0.14, a specific heat capacity of 970J/(kg. multidot. DEG C), a coefficient of thermal expansion of 1E-5, and a density of 2400kg/m3And a thermal conductivity of 1.28W/(m)2*k)。
S203, adding a concrete model into the preliminary grid model in Ansa software to enable aggregate to be embedded in concrete and subdividing the grid, wherein the aggregate and the concrete model grid share nodes to form a relatively fixed relation, and a concrete material research model is formed.
As shown in fig. 2 and 3, in the present embodiment, the concrete material research model is embedded into the ground foundation pit in a simulated manner, the periphery of the concrete material research model is fixed in the X, Y direction, the ground is fixed in the Z direction, the upper surface of the concrete material research model is impacted by the high-speed airflow and forms an angle α with the upper plane of the concrete material research model, the initial temperature of the concrete material research model is set to be 20 ℃, and the airflow impact can be simplified to be the impact force P.
In this embodiment, the fourth step includes the specific steps of:
s401, calculating the vertical load of the airflow: decomposing the impact force P into vertical force PbAnd horizontal shear force fiThe impact force P is set as P ═ mv, m is the mass flow measurement of the fuel gas per second 6.376kg/s, and v is the effective discharge speed of the fuel gas flow; vertical load Pb＝mvsinα；
S402, concrete surface thermal convection coefficient:
as shown in FIG. 4, the high temperature and high speed gas flow impacts the concrete wall surface, resulting in severe dynamic-thermal impact effect. As shown in fig. 12, when the hot air flow acts on the surface of the concrete, positive pressure and pneumatic shearing force are generated, which causes corresponding stress strain to the concrete. Meanwhile, strong heat convection occurs between the concrete wall surface and the concrete wall surface, and then heat transfer is completed in the concrete in a heat conduction mode. Thermal stress and vapor pressure will also occur after heat transfer is complete due to the unevenness of the concrete structure and the presence of original defects (voids). The impact heat transfer of the high-temperature high-speed airflow comprises heat convection between the hot airflow and the upper surface of the concrete and heat conduction inside the concrete;
as shown in FIG. 5, on the fluid side, a cylindrical channel for discharging high-temperature and high-speed airflow is defined as an exhaust channel, the heat transfer process between the hot airflow in the exhaust channel and the wall surface of the concrete material research model is regarded as non-circular channel turbulent flow forced convection heat transfer, and the Knudsen number is calculated by the Gnielinski formula
For gas
In the formula, l is the length of the exhaust passage; d is the equivalent diameter of the exhaust passage; f is the Darcy resistance coefficient of turbulent flow in the exhaust passage; re is Reynolds number, PrfPrandtl constant for hot gas flow;
equivalent diameter of exhaust passage
In the formula, A is the flow cross section of hot airflow in the exhaust passage; c is the circumference of the exhaust passage, namely the part of the exhaust passage wall contacted with the hot air flow;
f＝(1.82lgRe-1.64)-2
in the formula, ρlIs the fluid density; u. of∞Is the incoming flow velocity; μ is hydrodynamic viscosity, and μ ═ ρ ν; x is the characteristic length, namely the equivalent diameter of the exhaust passage;
wherein ν is the kinematic viscosity of the fluid; a is the fluid thermal conductivity coefficient.
After Nu is determined, the convective heat transfer coefficient between the hot air flow and the wall surface of the exhaust passage can be obtained according to the definition formula;
wherein λ is the fluid thermal conductivity;
simultaneous upper type get
Heat convection formula q ═ h | Tf-Tw|；
On the solid side of the exhaust duct, i.e. inside the concrete, heat conduction mainly occurs, heat flows from places with high temperature to places with low heat, and according to the Fourier law, the expression of the heat flow density is
Wherein q is the heat flow density unit W/(m)2) (ii) a λ is the heat transfer coefficient in W/(m ℃); t is the temperature unit;
effective heat transfer coefficient lambda of unsaturated concreteeffThe relationship with temperature and pore water saturation is as follows
In the above formulad(T) is the heat conduction coefficient of concrete in dry environment, and the expression is
λd(T)＝λd0(1+Aλ(T-T0))
Wherein, T0Taking 298.15K as a reference temperature; lambda [ alpha ]d0Taking 1.67W/mK; a. theλTake-1.017 × 10-3K-1；ρlIs the density of water; rhosThe density of the concrete; n is the porosity of the concrete;
in a three-dimensional Cartesian coordinate system, assuming that the temperature of one point in the concrete is T, the heat transfer isotropy lambda of the concrete material is lambdaeffThe differential equation of the three-dimensional unsteady heat conduction in the concrete structure without the internal heat source is as follows:
in the formula, rho is the density of concrete; c is the specific heat capacity of the concrete under constant pressure;
the heat conduction differential equation is a mathematical expression describing the commonality of the heat conduction process, in order to obtain the transient temperature field distribution of the concrete, the temperature distribution and the thermal boundary condition of the initial moment of the concrete are required to be given according to the actual condition, and for the unsteady heat transfer condition, the initial condition of the concrete heat transfer calculation is as follows:
T(x,y,z,0)＝T0
in the formula, ToIs the initial temperature of the concrete;
the heat convection coefficient h of the boundary surface of the fluid and the concrete and the temperature T of the hot air flow are knownfNamely:
calculating the convective heat transfer coefficient between the hot air flow and the wall surface (concrete) of the exhaust passage, taking the convective heat transfer coefficient as a thermal boundary condition, and loading the thermal boundary condition to a concrete side interface to obtain a concrete temperature field;
s403, calculating the pore internal pressure: as shown in fig. 6, the saturated steam pressure PvsCalculated by empirical formula given by Hyland and Wexler
Wherein C is8＝-5.8x103，C9＝1.3915，C10＝-4.8640×102，C11＝4.1765×10-5，C12＝-1.445,C136.5460, when T ≧ 674.3K, Pvs＝22.09MPa；
S404, calculating the pneumatic shearing force: the viscous forces of the mould surface need to be obtained by summing the friction forces of all wall elements, i.e.:
wherein: fvThe total viscous force; f. ofiIs the viscous friction of the wall surface unit i; c. CfiIs the viscous friction coefficient of the wall surface unit i; qAiIs the local dynamic pressure of the wall surface unit i; a. theiIs the area of the wall cell i;
coefficient of viscous friction c of unit ifiCalculating by adopting a reference temperature method based on local flow field parameters, namely:
ρe、ue、μedensity, speed and dynamic viscosity coefficient of the outer edge of the boundary layer are respectively, and x is the length of a streamline emitted from the front edge of the flat plate;
local pressure Q of unit iAiKinetic pressure at reference temperature T:
QAi＝0.5ρue 2
the viscous friction of unit i can then be expressed as:
the frictional force fiIs tangential to the flow line, i.e. the velocity direction of the local wall surface. Let the tangent unit vector be taui＝(τx，τy，τz) Friction force f of unit iiThe three components in the rectangular coordinate system (x, y, z) are:
fix＝fiτx
fiy＝fiτy
fiz＝fiτz
the total viscous force of the surface, in a rectangular coordinate system, can then be expressed as:
s405, dividing the concrete material research model into an impact area and an impact area according to different impact areas. Defining an impact area as an airflow shunting area, wherein the airflow parameter change of the area is severe, the power impact and thermal impact effect are prominent, and erosion damage is easy to occur; the area after the airflow is divided is defined after the impact area, the erosion damage of the area is small, and the heat effect of the airflow on the concrete wall surface is more remarkable. And a table of the working conditions is compiled as shown in fig. 7.
In the embodiment, in order to verify the rationality of the divided grids, the grids of the model are reconstructed in Ansa, after a shell grid is defined as an entity, the maximum unit size is reduced, calculation is carried out, the result is compared with that of the model of the original grid, the total number of the two redrawn model grids is 1581518, the node number is 271500, the total number of the grids is 857861, the node number is 152256, the subdivided grid model is led into Abaqus in an inp format for calculation, the analysis type is set as transient heat conduction, the working condition is set as impact region loading, the maximum temperatures of the surfaces of the subdivided grid model are 282.3 ℃ and 284.6 ℃ respectively, the maximum temperature of the surface of the original grid is 283.1 ℃, the maximum temperature errors of the surfaces of the subdivided grid model and the original model are 0.28% and 0.53% respectively, the result errors are very small, and the concrete surface temperature change curves of the three grid models along with time are basically consistent within an allowable range, therefore, the reasonability of the drawn grid can be judged.
In this embodiment, the specific steps of the fifth step are as follows:
s501, the calculation result in the fourth step is divided into two parts, wherein the first part is an impact area and a model stress cloud chart, a heat transfer depth, a displacement cloud chart, a damage area and a quality loss rate which are analyzed after the impact area under the impact of high-temperature airflow; the second part is that when observing the change along with the air flow impact angle, the air flow temperature and the air flow impact speed in the impact area, a model stress cloud chart, a heat transfer depth, a displacement cloud chart, a damage area and a quality loss rate are analyzed;
s502, in the impact area, according to the common principle in the step fourThe curves of the aerodynamic shear force, the vertical load and the thermal convection coefficient along with the time are obtained through calculation according to the formula and are shown in the figures 8 to 10; then calculating a transient temperature field of a concrete material research model, importing data of pneumatic shearing force, vertical load and thermal convection coefficient into calculation and analysis to obtain the temperature in the air vent, wherein the temperature propagation depth is 4.34mm and accounts for about 8.68% of the total length as can be seen from the graph in fig. 11 to 13, the temperature in the air vent is 283.1 ℃ which is the maximum value of the surface temperature of the concrete material research model, the internal pressure of the air vent can be calculated to be about 6MPa according to an internal pressure calculation formula of saturated steam of the air vent, a thermal-solid coupling field is established according to the internal pressure of the air vent and the temperature of the air vent to obtain a stress cloud map, the included angle between high-temperature airflow and the upper surface of the foundation pit is 26 ℃, the maximum equivalent stress. The maximum equivalent displacement of the model is 0.0086 mm. The concrete compressive strength F of C30 is specified according to GB50010-2010 concrete structure design Specificationck＝20.1MPa，FtkThe failure unit was removed and the model stress cloud shown in fig. 14 was obtained at 2.01 Mpa. And removing the failure unit in the Abaqus post-treatment, measuring the mass of the removed failure unit by using a model stress cloud chart as shown in the above chart to obtain the mass loss rate of 8.58%, measuring the volume of the failure unit in the Abaqus, and dividing the volume by the surface area of the concrete to obtain the average depth of the surface release layer of 4.29 mm. According to GB50010-2010 concrete structure design code, the concrete compressive strength Fck of C25 is 16.7MPa, the Ftk is 1.78MPa, the concrete compressive strength Fck of C35 is 23.4MPa, the Ftk is 2.20MPa, and the concrete compressive strength F of C40 is regulatedck＝26.8.4MPa、FtkThe mass measurement of the removed failure units in Abaqus at 2.39Mpa gave a C25 mass loss of 9.44%, a C35 mass loss of 7.75%, and a C40 mass loss of 7.11%; the comparison shows that the mass loss rate of C25 is the largest, the average depth of the exfoliated layer is the largest, the mass loss rate of C40 is the smallest, and the average depth of the exfoliated layer is the smallest.
The analysis result in the Abaqus can be obtained, the total time is 5.17s, and the increment step number is automatically divided into 9 steps. In the simulation calculation process, the surface of the model is not fallen at 0.1s, the surface of the model begins to fall at 0.2s, the falling volume accounts for 0.87%, the appearance of the surface of the concrete at 0.2s is known, the falling part is mainly concentrated near air holes and aggregates, and the curve shown in figure 15 shows that the slope of the curve is larger and the falling speed of the surface of the concrete is fastest within 0.2s to 0.5s, and the main reason is that the high-temperature airflow temperature is highest within 0.2s to 0.5s, so that the increase speed of the thermal stress of the surface of the concrete is higher within 0.2s to 0.5s, and the phenomenon of breaking and falling of the surface concrete and aggregates is caused because the high-temperature airflow temperature exceeds the compression strength and tensile strength limits.
S503, after the impact zone, the same as the step S502, the heat transfer depth is 4.13mm, which accounts for about 8.26% of the total length, the temperature in the air hole is about 242.3 ℃, the internal pressure of the air hole is about 4MPa, the maximum equivalent stress of the concrete surface is 102.40MPa, the mass loss rate is 6.62%, and the average depth of the surface falling layer is 3.31 mm.
S504, compiling the impact area and the calculation result after the impact area are summarized and compared as shown in the table 16.
S505, in the impact area, the impact angle of the high-temperature high-speed airflow, the temperature of the high-temperature high-speed airflow and the speed of the high-temperature high-speed airflow are changed by controlling a variable method, and the specific process of respectively calculating the loss degree of the impact area under different conditions is that decoupling simulation of single-factor change is performed during research of the impact area, namely when one variable changes, other variables are constants:
s5051, when the angle is 18 degrees, different impact angles only affect the size of the vertical load, and the maximum equivalent displacement of the model is 0.0087 mm. The concrete compressive strength F of C30 is specified according to GB50010-2010 concrete structure design Specificationck＝20.1MPa，FtkRemoving the failure unit from 2.01Mpa, removing the failure unit from Abaqus, measuring the mass of the removed failure unit to obtain the mass loss rate of 8.57%, measuring the volume of the failure unit in Abaqus, and dividing by the surface area of the concrete to obtain the average depth of the surface release layer of 4.29 mm; when the angle is 60 degrees, the maximum equivalent displacement can be 0.0084mm, the mass loss rate is 8.56 percent, and the average depth is 4.29 mm; when the angle is 90 degrees, the maximum equivalent displacement can be obtained to be 0.0083mm, the mass loss rate is 8.55 percent, and the average depth is 4.28 mm. When the angle of the impact airflow is 26 degrees, the displacement in the vertical direction shows that the right area is verticalIt is great to the downward direction displacement, the regional vertical displacement that makes progress in left side is great, the reason is that the concrete receives and becomes 26 orientation slant decurrent air current impact rather than the surface, so there can be this kind of phenomenon, along with the change of time, the vertical direction displacement that makes progress in concrete model right side diminishes gradually, the vertical direction displacement that makes progress in left side increases gradually, the reason is that the concrete model receives high temperature air current impact model and wholly has the thermal expansion phenomenon, in addition become 26 air current load with the concrete plane, lead to the model to appear the partial vertical direction displacement of left side and increase gradually, right side direction displacement reduces gradually, draw and strike the result of district under different impact angle and summarize table 17.
S5052, the heat convection heat transfer coefficient, the pneumatic shearing force and the air hole saturated steam pressure of the concrete surface can be influenced by the change of the high-temperature high-speed air flow temperature, and each load needs to be substituted into a formula for recalculation. When the temperature of the air flow is 760 ℃, the heat transfer depth is 3.8mm, which accounts for about 7.6% of the total length, the temperature in the air hole is about 229.90 ℃, the internal pressure of the air hole is about 2.5Mpa, Abaqus removes failure units, a model stress cloud chart is shown in the above chart, the mass measurement is carried out on the removed failure units to obtain the mass loss rate of 6.72%, the volume of the failure units is also measured in the Abaqus, and the average depth of the surface stripping layer is 3.36mm by dividing the volume of the failure units by the surface area of concrete. When the temperature of the air flow is 900 ℃, the heat transfer depth is 3.9mm, which accounts for about 7.8% of the total length, the temperature in the air holes is about 269.60 ℃, the internal pressure of the air holes is about 3.75MPa, the mass loss rate is 6.90%, and the average depth of the surface peeling layer is 3.45 mm. When the temperature of the air flow is 1100 ℃, the heat transfer depth is 4.0mm, which accounts for about 8% of the total length, the temperature in the air holes is about 326.4 ℃, the internal pressure of the air holes is about 15Mpa, the mass loss rate is 7.63%, and the average depth of the surface peeling layer is 3.82 mm. When the airflow temperature is 2200 ℃, the heat transfer depth is 4.1mm and accounts for about 8.2 percent of the total length, the temperature in the air holes is about 638.40 ℃, the internal pressure of the air holes is about 22.05Mpa, the mass loss rate is 10.17 percent, and the average depth of the surface peeling layer is 5.09 mm. At 2500 deg.C, the heat transfer depth is 4.2mm, which accounts for 8.4% of the total length, the temperature in the air hole is about 638.40 deg.C, the internal pressure in the air hole is about 22.05Mpa, the mass loss rate is 10.17%, and the average depth of the surface exfoliation layer is 5.09 mm. Drawing a result summary table chart 19 of the impact area at different impact gas temperatures to obtain an influence curve graph 18 of the air flow temperature on the average depth of the falling layer, wherein the average depth of the falling layer at different temperatures changes along with time, and the graph 18 shows that the increase speed of the falling layer depth along with the change of time is fastest and then tends to be gentle when the air flow temperature is 2500 ℃ and 2200 ℃ and the time is 0s to 0.3s, the heat convection coefficient is continuously increased when the main reason is that the heat convection coefficient is increased from 0s to 0.3s, the heat convection coefficient is gradually reduced after 0.3s, the increase speed of the surface temperature of the concrete is higher and lower, the corresponding increase speed of the thermal stress also presents a trend of higher and lower, and the falling speed of the failure unit on the surface of the concrete is directly influenced. As can be seen from fig. 18, the higher the temperature of the air flow at the same time, the greater the average depth of the exfoliated layer. The higher the temperature is, the higher the corresponding concrete surface temperature is, the correspondingly larger the surface thermal stress of the model is, and the falling degree of the falling layer is correspondingly increased. The local analysis of the concrete surface is carried out, the appearance and the stress of the concrete surface begin to change along with the change of time under the impact of the air flow at 1100 ℃, the slight peeling phenomenon begins to appear at 0.2s, the leaked green part is the aggregate, the lower small hole is the air hole part, the shape change of the aggregate and the air hole is obvious along with the continuous increase of the time, the air hole gradually becomes small, the dropping part of the aggregate becomes more, the stress also continuously increases, when the stress value reaches the tensile strength and the compressive strength of the concrete, the concrete begins to lose efficacy, and the thickness of the dropping layer continuously increases.
S5053, along with the change of the impact velocity, the heat convection heat transfer coefficient, the high-temperature airflow load, the saturated vapor pressure of the air hole and the pneumatic shearing force on the surface of the concrete all change, and each load needs to be recalculated according to a formula. As shown in FIG. 21, the propagation depth of the temperature at 382m/s was 3.9mm, which is about 7.8% of the total length, the internal temperature of the pores was about 174.00 ℃, the internal pressure of the pores was about 0.25MPa, the mass loss rate was 6.08%, and the average depth of the surface exfoliation layer was 2.97 mm. When the speed is 790m/s, the temperature propagation depth is 4.05mm, which accounts for about 8.1% of the total length, the temperature in the air vent is about 284.70 ℃, the pressure in the air vent is about 6MPa, the mass loss rate is 7.40%, and the average depth of the surface exfoliation layer is 3.64 mm. At 1770m/s, the temperature propagation depth is 4.2mm, which accounts for 8.4% of the total length, the temperature in the pores is about 455.3 deg.C, the pressure in the pores is about 22.05MPa, the mass loss rate is 10.00%, and the average depth of the surface exfoliation layer is 4.90 mm. At a speed of 2000m/s, the temperature propagation depth of 4.275mm, which is about 8.55% of the total length, the internal temperature of the pores is about 479.00 ℃, the internal pressure of the pores is about 22.05MPa, the mass loss rate is 10.17%, and the average depth of the surface exfoliation layer is 4.97 mm. At a speed of 2200m/s, the temperature propagation depth was 3.9mm, which accounted for about 7.8% of the total length, the temperature in the pores was about 498.2 ℃, the pore internal pressure was about 22.05Mpa, the mass loss rate was 10.34%, and the average depth of the surface exfoliation layer was 5.07 mm. The graph 20 of the influence curve of the air flow speed on the mass loss rate is obtained comprehensively, and the change relation of the mass loss rate at different speeds along with the time can be known from the graph 20, wherein the mass loss rate increase rate is larger from 0s to 0.5s, the mass loss rate increase rate tends to be flat after 1s, and the temperature increase rate of the impact air flow is faster from 0s to 0.5s and tends to be flat later. The increase of the air temperature directly influences the thermal stress of the upper surface of the model, the higher the temperature is, the larger the thermal stress is, the too large thermal stress exceeds the tensile strength and the compressive strength of the model, the failure and falling phenomena of the upper surface of the concrete are caused, the same moment is along with the larger air speed, the mass loss rate is also increased, the convection heat transfer coefficient and the air hole internal pressure are mainly influenced by the impact speed of the air flow, the larger the impact speed is known according to a formula, the convection heat transfer coefficient of the upper surface of the concrete is increased, the convection heat transfer coefficient is increased, the temperature of the surface of the model is directly increased, the corresponding thermal stress and the air hole internal pressure are also increased, the thermal stress exceeds a unit of the C30 concrete strength value, and the unit is regarded as.
In summary, the following conclusions can be drawn:
(1) because the impact speed and the temperature of the impact area are maximum, the speed can cause the increase of the convection heat transfer coefficient, the increase of the pneumatic shearing force and the increase of the internal pressure of the air hole, the temperature can cause the increase of the convection heat transfer coefficient and the increase of the internal pressure of the air hole, and the increase of the equivalent stress of an analysis result can be caused;
(2) although the impact angle of the impact area changes, the heat flow temperature of the whole impact surface is basically consistent, the pore internal pressure of the model is basically consistent, the change of the angle of the impact area mainly influences the size of the vertical load, compared with the thermal stress of the model, the stress generated by the vertical load is basically negligible, and therefore the equivalent stress, the displacement and the mass loss rate of the model surface are basically consistent.
(3) Along with the increase of the temperature of the airflow in the impact area, the thermal convection coefficient and the internal pressure of the air hole are mainly increased, the equivalent stress and the equivalent displacement of the corresponding model are increased, and the mass loss rate is increased.
(4) Along with the increase of the air flow speed of the impact area, the pneumatic shearing force and the thermal convection coefficient are increased, the internal pressure of the air hole is correspondingly increased, and the equivalent stress, the equivalent displacement and the mass loss rate of the model are correspondingly increased.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way. Any simple modification, change and equivalent changes of the above embodiments according to the technical essence of the invention are still within the protection scope of the technical solution of the invention.
Claims (6)
1. A damage assessment method for high-temperature high-speed air flow erosion concrete materials is characterized by comprising the following steps:
step one, establishing a concrete material model to be evaluated through Digmat-FE software, and carrying out grid division to obtain a concrete material preliminary grid model;
step two, refining the concrete material preliminary grid model obtained in the step one in ANSA software to obtain a concrete material research model;
step three, loading high-temperature high-speed airflow on the concrete material research model obtained in the step two in Abaqus software;
step four, calculating the airflow vertical load, the concrete surface thermal convection coefficient, the air hole internal pressure and the pneumatic shearing force of the loaded concrete material research model;
and step five, performing transient heat-solid coupling calculation on the concrete material research model in Abaqus software according to the calculation result in the step four to obtain a stress cloud chart of the concrete material research model, and further calculating the heat transfer depth, the displacement cloud chart, the damaged area and the mass loss rate so as to judge the damage degree of the high-temperature high-speed air flow erosion concrete material.
2. The method for evaluating the damage of the high-temperature high-speed air flow erosion concrete material according to claim 1, wherein the concrete steps of establishing the preliminary mesh model of the concrete material through the Digmat-FE software in the first step are as follows:
s101, establishing a three-dimensional random aggregate microscopic model of the concrete material in Digmat-FE software, wherein the aggregate in the random aggregate microscopic model is in an ellipsoid shape and contains ellipsoid air holes;
s102, setting the volume proportion of aggregates in the aggregate meso-scale model to be 70%, setting the long axis size of the aggregates to be 5-20mm, setting the volume proportion fraction of air holes in the aggregate meso-scale model to be 1%, and setting the long axis size of the air holes to be 1-5 mm;
s103, setting a certain gap between the air holes and the aggregate model, wherein the gap is not overlapped and is completely contained in a three-dimensional random aggregate mesoscopic model matrix and randomly distributed;
and S104, setting a preliminary grid size on the basis of the three-dimensional random aggregate mesoscopic model obtained in the S103 to obtain a preliminary grid model.
3. The method for evaluating the damage of the high-temperature high-speed air flow erosive concrete material according to claim 2, characterized in that the second step comprises the following specific operation steps:
s201, exporting the preliminary grid model obtained in the S104 to Ansa software in an inp format;
s202, defining the elastic modulus, Poisson ratio, specific heat capacity, thermal expansion coefficient, density and thermal conductivity coefficient of the aggregate and the concrete;
s203, adding a concrete model into the preliminary grid model in Ansa software to enable aggregate to be embedded in concrete and subdividing the grid, wherein the aggregate and the concrete model grid share nodes to form a relatively fixed relation, and a concrete material research model is formed.
4. The method for evaluating the damage of the high-temperature high-speed air flow erosive concrete material as claimed in claim 1, wherein the concrete material research model is embedded into a foundation pit on the ground in a simulated manner, the periphery of the concrete material research model is respectively fixed in X, Y directions, the ground is fixed in a Z direction, the upper surface of the concrete material research model is impacted by the high-speed air flow and forms an angle α with the upper plane of the concrete material research model, the initial temperature of the concrete material research model is set to be 20 ℃, and the air flow impaction can be simplified into an impact force P.
5. The method for evaluating the damage of the high-temperature high-speed air flow erosive concrete material according to claim 4, wherein the concrete steps of the fourth step comprise:
s401, calculating the vertical load of the airflow: decomposing the impact force P into vertical force PbAnd horizontal shear force fiSetting the impact force P as P-mv, m as the mass flow rate of the gas per second, m as 6.376kg/s, and v as the effective discharge speed of the gas flow; vertical load Pb＝mvsinα；
S402, calculating the thermal convection coefficient of the concrete surface:
the impact heat transfer of the high-temperature high-speed airflow comprises heat convection between the hot airflow and the upper surface of the concrete and heat conduction inside the concrete;
on the fluid side, a cylindrical channel for discharging high-temperature and high-speed airflow is defined as an exhaust channel, the heat transfer process between the hot airflow in the exhaust channel and the wall surface of a concrete material research model is regarded as non-circular channel turbulent forced convection heat transfer, and the Nussel number of the heat transfer process is calculated by a Gnielinski formula:
for gas
In the formula (1), l isThe length of the exhaust passage; d is the equivalent diameter of the exhaust passage; f is the Darcy resistance coefficient of turbulent flow in the exhaust passage; re is Reynolds number, PrfPrandtl constant for hot gas flow;
equivalent diameter of exhaust passage
In the formula (3), A is the flow cross section of the hot airflow in the exhaust passage; c is the circumference of the exhaust passage, namely the part of the exhaust passage wall contacted with the hot air flow;
f＝(1.82lgRe-1.64)-2(4)
in the formula (5), rholIs the fluid density; u. of∞Is the incoming flow velocity; μ is hydrodynamic viscosity, and μ ═ ρ ν; x is the characteristic length, namely the equivalent diameter of the exhaust passage;
in the formula (6), v is a fluid kinematic viscosity; alpha is a fluid temperature conductivity coefficient;
after Nu is determined, the convective heat transfer coefficient between the hot air flow and the wall surface of the exhaust passage can be obtained according to the definition formula;
in the formula (7), λ is a fluid thermal conductivity coefficient;
the joint type (1) to the formula (7) are as follows:
heat convection formula q ═ h | Tf-Tw|；
At the solid side of exhaust passage, inside the concrete, mainly take place heat conduction, the heat flows to the place that the heat is low from the place that the temperature is high, according to the Fourier law, the expression of heat flux density is:
in the formula (8), q represents a heat flux density unit of W/(m)2) (ii) a λ is the heat transfer coefficient in W/(m ℃); t is the temperature unit;
effective heat transfer coefficient lambda of unsaturated concreteeffThe relationship with temperature and pore water saturation is as follows:
in formula (9) < lambda >d(T) is the heat conduction coefficient of the concrete in a dry environment, and the expression is as follows:
λd(T)＝λd0(1+Aλ(T-T0)) (10)
in the formula (10), T0Taking 298.15K as a reference temperature; lambda [ alpha ]d0Taking 1.67W/mK; a. theλTake-1.017 × 10-3K-1；ρlIs the density of water; rhosThe density of the concrete; n is the porosity of the concrete;
in a three-dimensional Cartesian coordinate system, assuming that the temperature of one point in the concrete is T, the heat transfer isotropy lambda of the concrete material is lambdaeffThe differential equation of the three-dimensional unsteady heat conduction in the concrete structure without the internal heat source is as follows:
in the formula (11), rho is the density of the concrete; c is the specific heat capacity of the concrete under constant pressure;
the heat conduction differential equation is a mathematical expression describing the commonality of the heat conduction process, in order to obtain the transient temperature field distribution of the concrete, the temperature distribution and the thermal boundary condition of the initial moment of the concrete are required to be given according to the actual condition, and for the unsteady heat transfer condition, the initial condition of the concrete heat transfer calculation is as follows:
T(x,y,z,0)＝T0(12)
in formula (12), ToIs the initial temperature of the concrete;
the heat convection coefficient h of the boundary surface of the fluid and the concrete and the temperature T of the hot air flow are knownfThen, it can be:
solving the convective heat transfer coefficient of the high-temperature high-speed hot air flow and the wall surface of the exhaust passage of the concrete material, taking the convective heat transfer coefficient as a thermal boundary condition, loading the thermal boundary condition on a concrete side interface, and calculating to obtain a concrete temperature field;
s403, calculating the pore internal pressure: saturated steam pressure PvsCalculated by the empirical formula given by Hyland Wexler:
c in formula (13)8＝-5.8x103，C9＝1.3915，C10＝-4.8640×102，C11＝4.1765×10-5，C12＝-1.445，C136.5460, when T ≧ 674.3K, Pvs＝22.09MPa；
S404, calculating the pneumatic shearing force: the viscous forces of the mould surface need to be obtained by summing the friction forces of all wall elements, i.e.:
in formula (14): fvThe total viscous force; f. ofiIs the viscous friction of the wall surface unit i; c. CfiIs the viscous friction coefficient of the wall surface unit i; qAiIs the local dynamic pressure of the wall surface unit i; a. theiIs the area of the wall cell i;
viscous friction of unit iCoefficient of force cfiCalculating by adopting a reference temperature method based on local flow field parameters, namely:
in the formula (15) < rho >e、ue、μeDensity, speed and dynamic viscosity coefficient of the outer edge of the boundary layer are respectively, and x is the length of a streamline emitted from the front edge of the flat plate;
local pressure Q of unit iAiKinetic pressure at reference temperature T:
QAi＝0.5ρue 2
the viscous friction of unit i can then be expressed as:
frictional force fiIs the tangential direction of the streamline, i.e. the velocity direction of the local wall surface, and the unit vector of the tangential direction is taui＝(τx，τy，τz) Friction force f of unit iiThe three components in the rectangular coordinate system (x, y, z) are:
fix＝fiτx
fiy＝fiτy
fiz＝fiτz
the total viscous force of the surface is then expressed in three components of the rectangular coordinate system as:
s405, dividing the concrete material research model into an impact area and an impact area according to different impact areas, and compiling a working condition table.
6. The method for evaluating the damage of the high-temperature high-speed air flow erosive concrete material according to claim 5, characterized in that the concrete steps of the fifth step are as follows:
s501, the calculation result in the fourth step is divided into two parts, wherein the first part is an impact area and a model stress cloud chart, a heat transfer depth, a displacement cloud chart, a damage area and a quality loss rate which are analyzed after the impact area under the impact of high-temperature airflow; the second part is that when observing the change along with the air flow impact angle, the air flow temperature and the air flow impact speed in the impact area, a model stress cloud chart, a heat transfer depth, a displacement cloud chart, a damage area and a quality loss rate are analyzed;
s502, after the impact area and the impact area are respectively arranged, calculating according to a formula in the step four to obtain curves of the change of the pneumatic shearing force, the vertical load and the thermal convection coefficient along with time; then calculating a transient temperature field of the concrete material research model, importing the data of pneumatic shearing force, vertical load and thermal convection coefficient into calculation and analysis to obtain the temperature in the air vent, wherein the temperature in the air vent is the maximum value of the surface temperature of the concrete material research model, establishing a thermal-solid coupling field by the internal pressure and the temperature of the air vent to obtain a stress cloud chart, then removing the failure unit and determining the quality of the failure unit to obtain the quality loss rate of the concrete material research model, measuring the volume of the failure unit, dividing the volume of the failure unit by the surface area of the concrete to obtain the average depth of a surface falling layer, and finally obtaining the damage degree comparison of the concretes with different grades by setting the compressive strength standards of different concrete grades;
s503, in the impact area, changing the impact angle of the high-temperature high-speed airflow, the temperature of the high-temperature high-speed airflow and the speed of the high-temperature high-speed airflow by controlling a variable method, and respectively calculating the loss degree of the impact area under different conditions, wherein the calculation method is the same as that provided by the S502;
and S504, comparing and analyzing the calculation results obtained by integrating the S502 and the S503 to obtain the damage condition conclusion of the concrete material under the high-temperature and high-speed airflow erosion.
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| CN115615820A (en) * | 2022-08-11 | 2023-01-17 | 河海大学 | Construction method of early-age concrete relative humidity-tensile stress coupling model |
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| CN112632814A (en) * | 2020-12-04 | 2021-04-09 | 西安理工大学 | Method for constructing three-dimensional model of recycled concrete based on ellipsoid random aggregate |
| CN115615820A (en) * | 2022-08-11 | 2023-01-17 | 河海大学 | Construction method of early-age concrete relative humidity-tensile stress coupling model |
| CN115615820B (en) * | 2022-08-11 | 2023-05-16 | 河海大学 | Construction method of early-age concrete relative humidity-tensile stress coupling model |
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