Design method of armored vehicle magneto-rheological soft backseat system

Abstract

The invention discloses a design method of a magneto-rheological soft backseat system of an armored vehicle, and relates to an anti-backseat system, the method comprises the following steps: building an analytical expression of a magneto-rheological damper based on a Bingham model for a magneto-rheological brake in the magneto-rheological soft backseat system; according to the analytic expression of the magneto-rheological damper based on the Bingham model, a motion equation of magnetofluid passing through an annular gap formed by a piston and an oil cylinder in the magneto-rheological brake is established; based on the motion equation of the magnetic fluid, a magneto-rheological damper model based on a Herschel-Bulkley constitutive equation is established for the magneto-rheological braking machine; a magnetorheological damper model based on a Herschel-Bulkley constitutive equation is utilized to perform simulation analysis including finite element magnetic field analysis and process analysis so as to evaluate the performance of the magnetorheological braking and annealing machine, such as the pressure regulation characteristic, and optimization of the magnetorheological braking and annealing machine is facilitated.

Description

Technical Field

[0001] The invention relates to an anti-recoil system, in particular to a design method for a magnetic flow softening recoil system for an armored vehicle. Background Art

[0002] The recoil device is one of the core subsystems of armored vehicles, which directly affects the magnitude of the force acting on the gun mount of the armored vehicle, thereby affecting the weight of the entire system, shooting stability, the comfort of soldiers in the firing environment, shooting accuracy, and even the structural dimensions of the weapon system. Therefore, the development of a high-performance recoil device is of great significance to improving the tactical and technical level and comprehensive performance of the weapon system.

[0003] At present, the anti-recoil device adopts a conventional hydraulic anti-recoil device, which is a passive hydraulic device and cannot adjust the recoil resistance it generates according to different firing conditions. The recoil energy generated by the fired projectile depends on a variety of factors including the type of projectile, charging conditions, firing angle, atmospheric temperature, etc. Generally, when designing a conventional hydraulic anti-recoil device, it is necessary to ensure that the determined structure can dissipate the estimated maximum recoil energy. Although an ideal trapezoidal recoil force can be generated for a certain firing condition when designing a conventional hydraulic anti-recoil device, the generated recoil resistance will show different characteristics when the firing conditions change.

[0004] The anti-recoil device can also adopt a magnetorheological soft recoil device including a magnetorheological recoil machine. The magnetorheological recoil machine is a semi-active controllable hydraulic resistance device, which uses magnetorheological fluid (MR fluid, magnetic fluid) as a new type of anti-recoil device with working medium. Magnetorheological fluid is an intelligent fluid material that can rapidly change its apparent viscosity with different magnetic field strengths. It has the characteristics of rapid response to magnetic field changes, wide operating temperature range, and low power consumption. These characteristics enable the magnetorheological damping device to achieve real-time continuous control of the damping force. When applied to the anti-recoil device, it can also achieve effective control of the recoil resistance and recoil length. Compared with the conventional hydraulic anti-recoil device, the magnetorheological damping device can change the magnetic field generated by the electromagnetic coil in the magnetorheological damping device under different firing conditions (or shooting conditions) with only a small current, and the rheological characteristics of the magnetorheological fluid will change rapidly, and this change is reversible, so that the recoil resistance can be smoothly and effectively controlled to produce the desired recoil resistance.

[0005] The performance of the magnetic fluid softening recoil device is affected by factors such as the type of magnetic fluid used and the parameters of each structure. Therefore, before making a test device or an actual device according to the design structure of the magnetic fluid softening recoil device, it is necessary to evaluate the designed magnetic fluid softening recoil device to ensure that the designed magnetic fluid softening recoil device has better performance while meeting the actual needs of anti-recoil. Summary of the invention

[0006] The present invention provides a design method for a magnetorheological recoil brake and a soft recoil system of an armored vehicle, aiming to ensure that the designed magnetorheological soft recoil device has better performance while meeting the actual demand for anti-recoil.

[0007] The invention provides a design method for a magnetorheological soft recoil system of an armored vehicle, the method comprising: constructing an analytical expression of a magnetorheological damper based on a Bingham model for a magnetorheological recoil mechanism in the magnetorheological soft recoil system; establishing a motion equation of a magnetic fluid in an annular gap formed by a piston and a cylinder in the magnetorheological recoil mechanism according to the analytical expression of the magnetorheological damper based on the Bingham model; constructing a magnetorheological damper model based on a Herschel-Bulkley constitutive equation for the magnetorheological recoil mechanism based on the motion equation of the magnetic fluid; and performing simulation analysis including finite element magnetic field analysis and process analysis using the magnetorheological damper model based on the Herschel-Bulkley constitutive equation to evaluate the performance of the magnetorheological recoil mechanism.

[0008] The present invention constructs a magnetorheological damper model and performs simulation analysis to evaluate the performance of a magnetorheological recoil machine in a magnetorheological soft recoil system, such as pressure regulation characteristics, which is beneficial to optimizing the magnetorheological recoil machine to achieve better performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a flow chart of the design method of the magnetic flow softening rear seat system of the armored vehicle provided by the present invention;

[0010] Figure 2 is the velocity profile of the MR fluid through the parallel plate orifice;

[0011] Figure 3 This is a typical velocity distribution diagram of Bingham plastic material passing through the annular electrode gap when there is a linear pressure gradient along the axial direction;

[0012] Figure 4 It is a finite element model for axisymmetric magnetic field analysis of magnetorheological valve;

[0013] Figure 5 It is the BH curve of Hiperco iron-cobalt alloy;

[0014] Figure 6 is the BH curve of magnetorheological fluid;

[0015] Figure 7 This is the magnetic flux path diagram when 0.5A current is applied to the coil;

[0016] Figure 8 It is the magnetic flux density diagram of the magnetorheological valve at 2.0A current;

[0017] Fig. 9 is the magnetic flux density diagram of the MR fluid region in the magnetorheological valve at 2.0A;

[0018] Fig.10 is the magnetic flux density diagram of the MR fluid region of the magnetorheological valve under different current conditions;

[0019] Fig.11 is a graph of the yield stress and magnetic flux density of the MR fluid;

[0020] Fig.12 is the mesh division diagram of the magnetorheological valve area;

[0021] Fig.13 It is the velocity distribution diagram of the magnetorheological valve area when the piston speed is 10m / s and the magnetic flux density is 0.5T;

[0022] Fig.14 It is the pressure distribution diagram of the magnetorheological valve area when the piston speed is 10m / s and the magnetic flux density is 0.5T;

[0023] Fig.15 is the pressure difference across the MR valve under different magnetic flux density and piston speed;

[0024] Fig.16 It is the resultant force diagram of the gun bore under high temperature of armor-piercing projectile;

[0025] Fig.17 This is a graph of the relationship between the recoil velocity and time of an armor-piercing projectile at high temperature;

[0026] Fig.18 This is the recoil displacement diagram of armor-piercing projectile under high temperature conditions;

[0027] Fig.19 It is the magnetorheological recoil force diagram of armor-piercing projectile under high temperature;

[0028] Fig. 20 It is the magnetorheological brake force and time of the forward thruster under high temperature of armor-piercing projectile;

[0029] Fig.21 It is the forward force, magnetorheological force, and recoil force of the armor-piercing projectile under high temperature, and the sum and position of the two.

[0030] Fig. 22It is the recoil speed of the armor-piercing projectile when it loses power due to high temperature;

[0031] Fig.23 It is the recoil displacement of the armor-piercing projectile when it loses power due to high temperature;

[0032] Fig.24 It is the magnetorheological recoil force of armor-piercing projectiles under high temperature and power failure conditions;

[0033] Fig.25 It is the magnetorheological brake force and time of the forward thruster under the condition of high temperature and power failure of the armor-piercing projectile;

[0034] Fig.26 It is the forward thrust force, magnetorheological repulsion force and the sum and position of the two under the condition of high temperature and power failure of armor-piercing projectile;

[0035] Fig. 27 It is the resultant force of the gun barrel under normal temperature of the armor-piercing projectile;

[0036] Fig.28 is the recoil velocity of an armor-piercing projectile at room temperature;

[0037] Fig.29 It is the recoil displacement of an armor-piercing projectile at normal temperature;

[0038] Fig.30 It is the magnetorheological recoil force of armor-piercing projectile at room temperature;

[0039] Fig.31 It is the forward thrust force, magnetorheological recoil force and resultant force and time of the armor-piercing projectile at room temperature;

[0040] Fig.32 It is the forward force of the armor-piercing projectile at room temperature, the magnetorheological force of the recoil force, and the sum and position of the two.

[0041] Fig.33 It is the resultant force of the gun barrel under normal temperature of the armor-piercing projectile;

[0042] Fig.34 It is the recoil speed of the armor-piercing projectile at normal temperature;

[0043] Fig.35 It is the recoil displacement of the armor-piercing projectile at normal temperature;

[0044] Fig.36 It is the magnetorheological recoil force of the armor-piercing projectile at room temperature;

[0045] Fig.37 It is the forward thrust force, magnetorheological recoil force and resultant force and time of the armor-piercing projectile at normal temperature;

[0046] Fig.38 It is the forward thrust force, magnetorheological recoil force and the sum and position of the two under normal temperature conditions of the armor-piercing projectile;

[0047] Fig.39It is the resultant force in the howitzer's barrel at normal temperature;

[0048] Fig.40 is the recoil velocity of the howitzer at normal temperature;

[0049] Fig.41 It is the recoil displacement of the howitzer at normal temperature;

[0050] Fig.42 It is the magnetorheological recoil force of the howitzer at normal temperature;

[0051] Fig.43 It is the forward thrust force, magnetorheological recoil force and resultant force and time of the howitzer at normal temperature;

[0052] Fig.44 It is the forward force, magnetorheological braking force and the sum and position of the two of the howitzer at normal temperature. DETAILED DESCRIPTION

[0053] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Figure 1 The design method of the armored vehicle magnetic flow softening rear seat system provided by the present invention may include the following steps:

[0054] Step S101: constructing an analytical expression of a magnetorheological damper based on a Bingham model for a magnetorheological recoil mechanism in a magnetorheological soft recoil system.

[0055] When the gap of the magnetorheological fluid channel is relatively small, the magnetorheological damper can be regarded as a parallel plate valve. MR fluid is a viscoplastic fluid. Figure 2 The velocity distribution diagram of the MR fluid flowing through the parallel plate orifice is given. In intervals A and B, the shear stress exceeds the yield stress of the fluid, so there is shear flow. In area C, the shear stress is less than the yield stress, so there is no shear flow. This area is often called the plug flow area.

[0056] For this parallel plate valve, the following control equation (1.1) is obtained based on the force balance.

[0057]

[0058] Where u is velocity, τ is shear stress, r is radial coordinate, z is longitudinal coordinate (along the axial direction), p is the pressure generated by the movement of the piston head, and ρ represents the density of the fluid.

[0059] For equation (1.1), consider the inertia term It is very difficult to express it. Generally, the average inertia method is often used in engineering, that is, in It is the flow rate of the liquid in the magnetorheological valve obtained based on the incompressibility of the liquid, and ξ is an inertia correction coefficient.

[0060] Assuming that the above inertial terms do not couple with the magnetorheological effect, the viscoplastic flow in the parallel plate valve can be regarded as a quasi-static problem. For quasi-static analysis, the acceleration terms can be ignored. For flow mode or mixed mode dampers, the pressure gradient is assumed to vary linearly along the length of the valve. The governing equation (1.1) can be written as

[0061]

[0062] Where, ΔP = -F / A p , F is the force on the piston head, A p is the cross-sectional area of ​​the piston head. If the one-dimensional parallel plate axisymmetric structure is used as an approximation, the control equation (1.2) can be simplified to

[0063]

[0064] Considering both Newtonian flow and Bingham plastic shear flow, under Newtonian flow conditions, the shear mechanism is

[0065]

[0066] The characteristics of Bingham plastic materials are represented by dynamic yield stress. Under pre-yield conditions, because the shear stress in the fluid is less than the yield stress, the fluid will not flow in the annular magnetorheological gap. When the shear stress exceeds the dynamic yield stress, or |τ|>|τ y |, the material begins to flow, the velocity gradient is greater than 0, or du / dy>0. Therefore, the shear stress can be expressed as

[0067]

[0068] Therefore, the Newtonian fluid can be regarded as a dynamic yield stress τ y Bingham plastic material with a value of 0.

[0069] The following is an approximate parallel plate analysis of the damper in the three working modes.

[0070] 1. Cut mode

[0071] An approximate parallel plate analysis of the shear mode damper is performed and an expression for the dimensionless Bingham number Bi is established.

[0072] (1) For Newtonian flow, according to (1.3) and the boundary conditions listed in Table 1.1, the fluid velocity distribution u(y) and shear stress distribution τ(y) in the annular gap can be obtained.

[0073]

[0074]

[0075] The resulting damping force is:

[0076] F=C s v0(1.8)

[0077]

[0078] Wherein, b is the circumference of the MR valve, L is the length of the MR valve in contact with the fluid, and d is the gap of the MR valve.

[0079] (2) For Bingham plastic flow, substituting equation (1.5) into (1.3) and satisfying the velocity boundary conditions listed in Table 1.1, we obtain a velocity distribution that is the same as that of Newtonian flow, as shown in equation (1.6). However, because the dynamic yield stress is not zero, the shear stress distribution is different, as shown in equation (1.7).

[0080]

[0081] The dimensionless number Bi is introduced and defined as

[0082]

[0083] Bi is the ratio of the dynamic yield stress of the Bingham plastic material to the shear stress of the Newtonian flow with viscosity μ between two parallel plates with a relative velocity of v0. When the damper shaft speed is small, or the damper works close to the yield point of the Bingham plastic material, the Bingham number is large. When the damper shaft speed is large, or when the damper works under strong post-yield conditions, the Bingham number is small. When the dynamic yield stress is 0, the Bingham number is also 0, which is equivalent to the case where there is no external magnetic field. Therefore, the Bingham number can be regarded as a measure of whether the working state of the damper is close to the yield condition.

[0084] The force is proportional to the speed of the shaft, i.e.

[0085] F=C eq.s v0(1.12)

[0086] Equivalent viscous damping constant C eq and Newton's damping constant C s The ratio is

[0087]

[0088] Obviously, if the Bingham number approaches 0, it will be a Newtonian flow analysis. When a large force is applied to the damper shaft, the shaft speed increases and the Bingham number decreases. Therefore, when the damper is subjected to a large force, the magnetorheological fluid behaves as a Newtonian flow in terms of damping performance.

[0089] Table 1.1. Boundary conditions of the damper for the three modes

[0090]

[0091] 2. Flow Pattern

[0092] Approximate parallel plate analysis of the flow mode damper.

[0093] (1) For Newtonian flow, the velocity distribution u(y) and shear stress distribution τ(y) are as follows:

[0094]

[0095]

[0096] The flow volume Q through the annular gap is

[0097]

[0098] Make the volume flow Q through the annular gap equal to the volume flow discharged by the piston head, while noting that ΔP = -F / A p ,get

[0099] F=C f v0(1.17)

[0100]

[0101] Among them, A d is the cross-sectional area of ​​the magnetorheological valve. The Newtonian velocity profile is the upper bound of the Bingham plastic velocity profile.

[0102] (2) For Bingham plastic flow, substituting equation (1.5) into (1.3), direct integration can obtain the velocity distribution shown in equation (1.19):

[0103]

[0104] According to the boundary conditions listed in Table 1.1, the velocity distribution diagram of each flow area is determined. Area 1 and Area 3 are the left rear yield area and the right rear yield area respectively, and Area 2 is the pre-yield area. The velocity distribution diagrams of these areas are shown in Figure 3 .

[0105] The boundary conditions of zone 1 are listed in Table 1.1, u1(0) ​​= 0, u1'(y pi )=0, the velocity distribution is:

[0106]

[0107] In zone 2, the shear stress is:

[0108]

[0109] The boundary conditions of zone 2 are given in Table 1.1. pi )=τ y ,τ(y po )=-τ y , so we can get the following equation:

[0110] and

[0111] Subtracting the two gives an expression for the plug flow thickness, as follows:

[0112]

[0113] Zone 3 is the post-yield zone, and the boundary conditions are shown in Table 1.1, u3(d) = 0, u'3(y p0 )=0, the velocity distribution is

[0114]

[0115] Since the velocity in the plug flow region is a constant,

[0116] u1(y pi )=u3(y po )(1.25)

[0117] Combined with the plug flow thickness equation (1.23), the following set of equations is obtained:

[0118] y p0 -y pi =δ and y pi +y o0 =d(1.26)

[0119] Solved

[0120] and

[0121] It can be defined as the dimensionless plug flow thickness

[0122]

[0123] Therefore, the position of the plug flow can be known based on the force acting on the damper. According to the approximate parallel plate analysis, the plug flow is symmetric about the center of the annulus. For the actual circular tube geometry, this conclusion is only an approximation to the actual situation.

[0124] Using these plug flow position values, the velocity distributions in regions 1, 2, and 3 are:

[0125]

[0126] The shear stress distribution in the gap is:

[0127]

[0128] Now, using the dimensionless plug flow thickness , Bingham number Bi is used to represent the equivalent viscous damping constant C eq,f The speed of the shaft can be expressed using the Bingham number:

[0129]

[0130] The dynamic yield stress is:

[0131]

[0132] then,

[0133]

[0134] Finally, we get:

[0135]

[0136] Equivalent viscous damping constant C eq，f and Newton's damping constant C f The ratio is

[0137]

[0138] Noting that the total flow through the annulus is equal to the flow displaced by the piston, the Bingham number can be expressed in terms of the dimensionless plug thickness, with the flow value for each region being

[0139]

[0140] Due to the symmetry of velocity distribution, Q1 = Q3. Total flow value | Q f |For

[0141]

[0142] The total flow value is equal to the flow value discharged by the piston head, so

[0143] |Q|=Q p =A p v0 (1.38)

[0144] From these relationships, it can be concluded that:

[0145]

[0146] 3. Blending Mode

[0147] Approximate parallel plate analysis of the mixed-mode damper.

[0148] (1) For mixed mode Newtonian flow, the velocity distribution u(y) and shear stress distribution τ(y) are:

[0149]

[0150]

[0151] The flow value Q through the annular gap is obtained by integration as follows:

[0152]

[0153] The total flow through the annulus is equal to the flow Q discharged by the piston. p =A p v0, note that ΔP = -F / A p , the damping force can be expressed as:

[0154] F=C m v0 (1.48)

[0155]

[0156] The Newtonian flow velocity profile is an upper bound for the Bingham plastic velocity profile, but a lower bound for the viscous damping of a mixed mode damper.

[0157] (2) For Bingham plastic flow, the boundary conditions of the mixed mode damper are the same as the flow mode except for zone 1. Because the piston head also includes electrodes, the fluid velocity at the piston head end is u(0) = -v0. Based on the boundary conditions, the following velocity distributions are obtained for zones 1, 2, and 3:

[0158]

[0159] The shear stress distribution is the same as for the flow mode damper. Since the plug flow velocity is constant, it is as follows:

[0160] u1(y pi )=u3(y p0 )(1.51)

[0161] Must be satisfied, so

[0162]

[0163] Considering

[0164] y p0 -y pi =δ(1.53)

[0165] The positions of the inner and outer plug flows are expressed as

[0166]

[0167] Similar to flow mode damper analysis

[0168]

[0169] However, in a mixed-mode damper, the relationship between the Bingham number and the dimensionless plug thickness is different. The total flow through the annular gap is

[0170]

[0171]

[0172]

[0173]

[0174] Therefore, considering that the total flow value through the annular gap is equal to the flow discharged by the piston head, the following relationship is obtained:

[0175] α2Bi 2 +α1Bi+α0=0(1.58)

[0176]

[0177] The Bingham number is the dimensionless plug flow thickness Function of the area ratio Ap / Ad

[0178]

[0179] Step S102 and step S103: According to the analytical expression of the magnetorheological damper based on the Bingham model, the motion equation of the magnetic fluid in the annular gap formed by the piston and the cylinder in the magnetorheological recoil machine is established, and based on the motion equation of the magnetic fluid, a magnetorheological damper model based on the Herschel-Bulkley constitutive equation is constructed for the magnetorheological recoil machine.

[0180] For the annular flow port formed by the piston and cylinder described in the previous section, according to the Navier-Stokes equation, the motion equation of the fluid can be expressed as:

[0181]

[0182] Here, x is the axial coordinate, r is the radial coordinate, ρ is the density of the fluid, u(r) represents the flow velocity, τ is the shear stress, is the pressure gradient. If the inertia of the fluid is ignored and only the quasi-static one-dimensional flow of the fluid is studied, equation (2.1) can be simplified to:

[0183]

[0184] Considering the small gap, if the parallel plate model is used ( Figure 2 ) replaces the axisymmetric geometric model, then equation (2.2) is simplified to:

[0185]

[0186] Integrating formula (2.3) we get:

[0187]

[0188] Where D is a constant determined by the boundary conditions.

[0189] The relationship between shear stress τ and shear strain rate du / dz is the "constitutive relationship" of MR fluid. Since the Bingham model is simple and easy to understand, many literatures use the Bingham model to estimate the mechanical properties of MR dampers. However, the Bingham model cannot accurately describe the behavior of the damper under high speed and high magnetic field input conditions. Under high shear rates or high magnetic field strengths, magnetic fluids will undergo shear thinning or shear thickening in the post-yield zone. The Herschel-Bulkley shear model can be regarded as a modification of the Bingham model, which uses a shear strain rate exponential model to replace the constant post-yield viscosity characteristics of the Bingham model. Since the damper under study is an impact MR damper, the Herschel-Bulkley viscoplastic model is used below.

[0190] In region A, the shear strain rate The relationship between shear stress and shear strain rate du / dz can be expressed as:

[0191]

[0192] In the formula, τ yis the yield stress, K is the viscosity index of the MR fluid, and n is the behavior index of the fluid. Substituting (2.5) into (2.4), using the boundary condition u(z=0)=0, we can integrate:

[0193]

[0194] By similar derivation, for region B, we get:

[0195]

[0196] Assuming that the MR fluid is incompressible, using equations (2.6) and (2.7), the volume flow rate through the parallel plate valve can be expressed as:

[0197]

[0198] Here, A p , A r is the cross-sectional area of ​​the piston head and piston rod. R1 and R2 are the outer radius of the piston and the inner radius of the cylinder respectively. v0 is the speed of the piston.

[0199] Take a fluid micro-segment along the boundary in the plug flow region and establish its force balance equation, and it is easy to get:

[0200]

[0201] Assume that dp / dx varies linearly along the axial direction and ignore the influence of boundary condition u(z=d)=-v0. Define the thickness of the infinite rigid plug flow Then from equation (2.8), the pressure difference at both ends of the orifice can be obtained:

[0202]

[0203] Among them, L a is the length of the magnetic field active area in the flow port, Δp a It is the pressure drop caused by the magnetic field activation area in the flow orifice.

[0204] Substituting equation (2.10) into (2.9) yields The nonlinear equation is:

[0205]

[0206] Here, B is called the generalized Bingham number:

[0207]

[0208] Figure 3 The thickness of the infinite rigid plug flow under different fluid behavior indices is given The actual characteristic index n mainly depends on the type and working conditions of different magnetorheological fluids. There is still a lack of in-depth research on how to experimentally determine the behavior index of the magnetorheological damper at work.

[0209] Therefore, according to the yield stress τ y , piston speed v0, the thickness of the infinite rigid plug flow can be obtained from equation (2.11): Using equation (2.10), we can find the pressure difference at the orifice, and then find the damping force F generated by the activation area. da :

[0210] F da =(A p -A r )Δp a (2.13)

[0211] Let L represent the total length of the piston, then the damping force generated by the area with zero magnetic flux density in the flow port can be expressed as:

[0212]

[0213] Therefore, the total damping force due to the magnetorheological effect is:

[0214] F d =F da +F du (2.15)

[0215] Step S104: using a magnetorheological damper model based on the Herschel-Bulkley constitutive equation, a simulation analysis including a finite element magnetic field analysis and a process analysis is performed to evaluate the performance of the magnetorheological damper.

[0216] 1. Finite element magnetic field analysis of magnetorheological machine

[0217] Finite element magnetic field analysis is performed on the magnetorheological damper model based on the Herschel-Bulkley constitutive equation to determine the magnetic flux density in the magnetic fluid area of ​​the magnetorheological damper under different currents. Specifically, a finite element magnetic field analysis is performed on the magnetorheological valve in the magnetorheological retarding machine to obtain the magnetic flux density in the gap area of ​​the magnetorheological valve under different applied currents. Figure 4 The finite element model of axisymmetric magnetic field analysis of magnetorheological valve is given. Figure 5 is the BH curve of Hiperco iron-cobalt alloy, Figure 6 It is the BH curve of magnetorheological fluid. Figure 7 is the magnetic flux path when 0.5A current is applied, Figure 8 and Fig. 9is the magnetic flux density of the magnetorheological valve when a current of 2.0A is applied. Fig.10 The magnetic flux density in the MR fluid region of the magnetorheological valve under different current conditions is given, and it is basically saturated when the current is 3A.

[0218] 2. Flow field analysis of magnetic variable solenoid valve

[0219] The flow field analysis of the magnetorheological damper model based on the Herschel-Bulkley constitutive equation is carried out to determine the velocity distribution and pressure distribution of the magnetic fluid region and the pressure difference at both ends of the flow port under different piston speeds and different magnetic flux densities, so as to evaluate the performance of the magnetorheological damper. Specifically, the flow field of the magnetorheological damper is analyzed using the FLOTRAN CFD analysis module in the ANSYS software.

[0220] Take out the damping gap in the magnetorheological retarding machine and establish a 2-D axisymmetric model, such as Fig.12 As shown. In the analysis process, it is approximately considered that the properties of the fluid are constants, that is, the density, viscosity and other parameters of the fluid do not change with the change of temperature; secondly, it is considered that the magnetorheological fluid under study is incompressible; finally, the Reynolds number is used to determine whether the fluid is laminar or turbulent. The analysis unit is set as a four-node quadrilateral unit, and the mapping grid division method is used in the gap. Considering that the gradient change of the fluid in the area close to the wall is relatively large, the density of the grid division in the area close to the wall is large. The grid model after division is as follows Fig.12 shown.

[0221] In flow field analysis, the loads and boundary conditions that need to be set are mainly velocity and pressure. Here, the inlet velocity is set to the flow velocity to be studied, and the velocity of the flow boundary is 0.

[0222] Since magnetorheological fluid can be regarded as Bingham fluid under the action of magnetic field, the Bingham model is activated in the fluid parameter setting of ANSYS software. The main parameters that need to be set in the Bingham model include Newtonian viscosity and yield stress. The magnetic induction intensity in the gap under different currents has been calculated through magnetic field analysis. Fig.11 The τ-B curve of the magnetorheological fluid (for example, model MRF-F28T) shown can obtain the magnitude of the yield stress under different magnetic induction intensities. The density, Newtonian viscosity and yield stress under the studied current of the magnetorheological fluid are input into the model.

[0223] The following calculation gives the pressure difference between the inlet and outlet of the MR valve under different magnetic flux densities to evaluate the pressure regulation characteristics of the MR valve. Fig.13 It shows the velocity distribution in the magnetorheological valve area when the piston speed is 10m / s and the magnetic flux density is 0.5T. Fig.14The pressure distribution in the magnetorheological valve area is shown when the piston speed is 10m / s and the magnetic flux density is 0.5T. Combining the calculation results under different piston speeds and magnetic flux densities, Fig.15 The pressure difference across the MR valve under different magnetic flux density and piston speed was obtained, reflecting the pressure regulation characteristics of the MR valve.

[0224] Furthermore, the method of the present invention may also include:

[0225] Step S105: Through simulation analysis, the performance of the magnetorheological deceleration machine when using different types of magnetic fluids and different structural parameters is evaluated respectively, and the magnetic fluid and structural parameters that make the magnetorheological deceleration machine perform best are selected to complete the design of the magnetorheological deceleration machine.

[0226] Through the above steps, the present invention determines the structural parameters of the magnetorheological retarding machine and the type of magnetorheological fluid used as follows:

[0227] (1) Left end magnetorheological internal valve: gap inner diameter 80 mm, gap outer diameter 84 mm, magnetorheological channel activation length 65 mm, magnetorheological channel width 2 mm;

[0228] (2) Left end magnetorheological external valve: gap inner diameter 104 mm, gap outer diameter 108 mm, magnetorheological channel activation length 64 mm, magnetorheological channel width 2 mm.

[0229] (3) The magnetorheological valve on the right is the same as the left one.

[0230] (4) Piston head diameter 100 mm, piston rod diameter 38 mm.

[0231] (5) Use the magnetorheological fluid model MRF-F28T provided by Chongqing Institute of Materials.

[0232] Through simulation analysis based on finite element magnetic field analysis and flow field analysis, it was found that if high-performance magnetorheological valves and high-performance magnetorheological fluids are used and the soft recoil launching process of the magnetorheological recoil brake is utilized, under normal soft recoil launching conditions, the damping force generated by the magnetorheological recoil brake can be adjusted by adjusting the current in the magnetorheological valve coil, thereby ensuring normal locking and launching under various launching conditions.

[0233] Application Examples

[0234] The magnetorheological soft recoil system using the above structural parameters and magnetorheological fluid can be used to calculate the recoil dynamics of high-temperature and normal-temperature soft recoil firing of armor-piercing projectiles, normal-temperature and low-temperature soft recoil firing of armor-piercing projectiles, normal-temperature soft recoil firing of grenades, misfire under high-temperature conditions of armor-piercing projectiles, and normal-temperature delayed firing of armor-piercing projectiles. The following only takes the high-temperature and normal-temperature soft recoil firing of armor-piercing projectiles, normal-temperature recoil firing of armor-piercing projectiles, and normal-temperature soft recoil firing of grenades as examples for soft recoil firing calculation.

[0235] 1. High temperature soft recoil firing of armor-piercing projectiles

[0236] The recoil mass is 2100kg, the magnetic flux density of the magnetorheological valve is 0.4T, and the initial pressure of the forward ram is 14.0MPa.

[0237] pass Figures 16 to 21 The calculation results show that under the condition of soft recoil launch, the maximum recoil resistance of high-temperature armor-piercing projectile is 32 tons.

[0238] In order to analyze the reset speed under the maximum value of overstuck, a fault situation is considered: the magnetorheological recoiling machine is not powered on, and the overstuck buffer reaches the limit state, which is used to examine the reset speed after the pinhole plays a braking role. The initial pressure of the forward punch is still set to 14.0MPa.

[0239] pass Figure 22 to Figure 26 It can be seen that when the armor-piercing projectile loses power due to high temperature, the over-stuck restraint force is very large. In the case of maximum over-stuck, the maximum reset speed is 1.5m / s, which can be tolerated by the lock.

[0240] 2. Armor-piercing projectiles fired at room temperature with soft recoil

[0241] The magnetic flux density of the magnetorheological valve is set to 0.4T, and the front punch hanging pressure is set to 14.0MPa.

[0242] from Figures 27 to 32 It can be seen that under this launch condition, the maximum recoil resistance is less than 30 tons.

[0243] 3. Soft recoil launch of armor-piercing projectile at room temperature

[0244] Under normal temperature conditions of the armor-piercing projectile, the magnetic flux density of the magnetorheological valve is set to 0.2T, and the forward plunger hanging pressure is set to 9.0MPa.

[0245] Figures 33 to 38 It is the calculation result of the armor-piercing projectile under the condition of soft recoil launch at room temperature.

[0246] 4. Grenade soft recoil launch at room temperature

[0247] When the grenade is at normal temperature, the magnetic flux density of the magnetorheological valve is set to 0.2T and the forward plunger clamping pressure is set to 10.0MPa.

[0248] Figures 39 to 44 It is the calculation result of the howitzer under the condition of soft recoil firing at normal temperature.

[0249] The above soft recoil launch calculation results show that by adjusting the magnetic field strength in the magnetorheological valve of the magnetorheological recoil machine, reliable soft recoil launch under various working conditions can be achieved. Under the condition of soft recoil launch, the maximum recoil resistance of the high-temperature armor-piercing projectile is 32 tons. Compared with conventional launch, the maximum recoil resistance of soft recoil launch can be reduced by more than 40%.

[0250] The preferred embodiments of the present invention are described above with reference to the accompanying drawings, but the scope of the present invention is not limited thereby. Any modification, equivalent substitution and improvement made by those skilled in the art without departing from the scope and essence of the present invention shall be within the scope of the present invention.

Claims

1. A design method for a magnetic flow softening rear seat system for an armored vehicle, characterized in that: The method comprises: An analytical expression for the magnetorheological damper based on the Bingham model is constructed for the magnetorheological recoil mechanism in the magnetorheological soft recoil system; According to the analytical expression of the magnetorheological damper based on the Bingham model, the motion equation of the magnetic fluid in the annular gap formed by the piston and the cylinder in the magnetorheological damper is established; Based on the motion equation of the magnetic fluid, a magnetorheological damper model based on the Herschel-Bulkley constitutive equation is constructed for the magnetorheological damper; Using a magnetorheological damper model based on the Herschel-Bulkley constitutive equation, simulation analysis including finite element magnetic field analysis and process analysis was performed to evaluate the performance of the magnetorheological damper.

2. The method according to claim 1, characterized in that The analytical expression for constructing a magnetorheological damper based on the Bingham model for the magnetorheological recoil mechanism in the magnetorheological soft recoil system includes: According to the force balance, the control equation of the magnetorheological damper is obtained, and the control equation of the magnetorheological damper is simplified by replacing the axisymmetric structure of the magnetorheological damper with the axisymmetric structure of the parallel plate valve, so as to obtain the simplified control equation including the shear mode, the flow mode and the mixed mode; By performing an approximate parallel plate analysis on the magnetorheological damper in shear mode, the shear stress distribution expression of the magnetic fluid in shear mode is determined as the analytical expression of the magnetorheological damper in shear mode. By performing an approximate parallel plate analysis on the magnetorheological damper in the flow mode, an expression for the total flow rate of the magnetic fluid passing through the annular gap in the flow mode is determined as an analytical expression for the magnetorheological damper in the flow mode; By performing an approximate parallel plate analysis on the mixed-mode magnetorheological damper, an expression for the total flow rate of the magnetic fluid passing through the annular gap in the mixed mode is determined as an analytical expression for the mixed-mode magnetorheological damper.

3. The method according to claim 2, characterized in that The simplified control equations including shear mode, flow mode and mixing mode are as follows: ΔP=-F / A p Where τ is the shear stress; y represents the radial direction of the parallel plate valve; F is the force on the piston head; A p is the cross-sectional area of ​​the piston head; L is the total length of the piston.

4. The method according to claim 2, characterized in that: The shear stress distribution expression of the magnetic fluid under the shear mode includes: If the magnetic fluid behaves as a Newtonian flow, the shear stress distribution expression of the magnetic fluid in the shear mode is: If the magnetic fluid behaves as Bingham plastic flow, the shear stress distribution expression of the magnetic fluid in the shear mode is: Wherein, τ(y) represents the shear stress distribution; Bi is the Bingham number, which is a dimensionless number; τy is the dynamic yield stress of Bingham plastic flow; d is the gap of the magnetorheological valve; μ is the viscosity of the magnetic fluid; and v0 is the relative velocity.

5. The method according to claim 2, characterized in that: The total flow rate of the magnetic fluid passing through the annular gap under the flow mode is expressed as: ΔP=-F / Ap Wherein, |Qf| is the total flow rate of the magnetic fluid passing through the annular gap in the flow mode; b is the circumference of the magnetorheological valve; L is the length of the magnetorheological valve in contact with the magnetic fluid; d is the gap of the magnetorheological valve; μ is the viscosity of the magnetic fluid; F is the force on the piston head; Ap is the cross-sectional area of ​​the piston head; is the dimensionless plug flow thickness; in the flow mode, the Bingham number Bi can be expressed in terms of the dimensionless plug flow thickness.

6. The method according to claim 2, characterized in that The total flow rate of the magnetic fluid passing through the annular gap in the mixed mode is expressed as: ΔP=-F / A p Wherein, Q is the total flow rate of the magnetic fluid passing through the annular gap in the mixed mode; b is the circumference of the magnetorheological valve; L is the length of the magnetorheological valve in contact with the magnetic fluid; d is the magnetorheological valve gap; μ is the viscosity of the magnetic fluid; F is the force on the piston head; A p is the cross-sectional area of ​​the piston head; A d is the cross-sectional area of ​​the MR valve; is the dimensionless plug flow thickness; Bi is the Bingham number, which is a dimensionless number.

7. The method according to claim 2, characterized in that The motion equation of the magnetic fluid in the annular gap formed by the piston and the cylinder in the magnetorheological retarding machine is expressed as: Where x is the axial coordinate; r is the radial coordinate; ρ is the density of the magnetic fluid; u(r) is the flow velocity; τ(r) is the shear stress, is the pressure gradient, Characterize the total flow rate in flow mode and mixed mode, Represents the shear stress distribution in shear mode.

8. The method according to claim 7, characterized in that The magnetorheological damper model based on the Herschel-Bulkley constitutive equation is constructed for the magnetorheological soft recoil system based on the motion equation of the magnetic fluid, including: According to the motion equation of the magnetic fluid, the equation of shear stress is obtained when the inertia of the magnetic fluid is neglected and the axisymmetric geometric model of the magnetorheological damper is replaced by a parallel plate model valve; According to the equation of the shear stress and the Herschel-Bulkley constitutive equation expressing the constitutive relationship between shear stress and shear strain rate, an equation for the pressure difference at both ends of the flow port of the parallel plate valve is obtained as a magnetorheological damper model based on the Herschel-Bulkley constitutive equation, wherein the total damping force of the magnetorheological damper model based on the Herschel-Bulkley constitutive equation is equal to the sum of the damping force generated in the activation area and the damping force generated in the area with zero magnetic flux density in the flow port.

9. The method according to claim 8, characterized in that The simulation analysis including finite element magnetic field analysis and process analysis using the magnetorheological damper model based on the Herschel-Bulkley constitutive equation includes: Finite element magnetic field analysis is performed on the magnetorheological damper model based on the Herschel-Bulkley constitutive equation to determine the magnetic flux density in the magnetic fluid region of the magnetorheological damper under different currents. The flow field analysis of the magnetorheological damper model based on the Herschel-Bulkley constitutive equation is carried out to determine the velocity distribution and pressure distribution in the magnetic fluid region under different piston speeds and different magnetic flux densities, as well as the pressure difference at both ends of the flow port, so as to evaluate the performance of the magnetorheological damper.

10. The method according to any one of claims 1 to 9, characterized in that: The method further comprises: Through simulation analysis, the performance of the magnetorheological recoil machine when using different types of magnetic fluids and different structural parameters is evaluated respectively, and the magnetic fluid and structural parameters that make the magnetorheological recoil machine perform best are selected to complete the design of the magnetorheological recoil machine.

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