Method for predicting disconnection time of disconnector based on multi-physics field coupling simulation

Abstract

The invention discloses a disconnector disconnection time prediction method based on multi-physics field coupling simulation. Comprising the following steps: establishing a geometric model of a core action part of the disconnector, constructing a time domain electric field equation of conductor parts on the basis, and calculating space loss distribution of each conductor part; and establishing a transient heat conduction equation, and obtaining a transient temperature field of each core action part. A finite deformation dynamic force field equation is established, thermal stress is solved based on a temperature field, and the displacement of each core part is obtained in combination with the electrode pre-tightening force and the spring force. Through time sequence solving, when the soldering tin displacement is larger than zero, the moment is judged to be the disconnection time of the disconnector. According to the method, the dynamic coupling effect of multiple physical fields of electricity, heat and force can be considered at the same time, the mechanical degradation and failure process of soldering tin under the combined action of temperature rise and mechanical load is truly reflected, accurate prediction of the disconnection time of the disconnector is achieved, and the reliability evaluation capacity of the surge protection device under the transient overvoltage working condition is improved.

Description

Technical Field

[0001] This invention belongs to the field of surge protector reliability simulation technology, specifically involving a method for predicting disconnection time of a trip unit based on multi-physics coupling simulation. Background Technology

[0002] Surge protectors (SPDs) are used to limit transient overvoltages (TOVs) and discharge surge energy. They typically contain a disconnector that quickly disconnects under abnormal operating conditions to prevent equipment damage and safety accidents caused by sustained overheating, arcing, etc. The disconnector usually consists of upper and lower copper electrodes, solder joints connected to a metal oxide varistor (MOV), an electrode structure with preload, and a spring and plastic mechanism providing reset / disconnection drive. Under TOV conditions, the MOV exhibits significant conduction and heating behavior, causing the solder temperature to rise and adding external mechanical load, which may ultimately trigger solder joint failure and mechanism breakage. Therefore, accurately and repeatably predicting the disconnector's disconnection time under TOV conditions is crucial to ensuring the reliability of the SPD.

[0003] In existing technologies, TOV tests using physical prototypes are often used to evaluate the release mechanism's operation, only obtaining macroscopic results such as whether it has tripped. To observe the dynamic process of the solder joint's heating-stressing-failure, expensive equipment such as high-speed photography and infrared thermography is required, resulting in high testing costs, poor repeatability, and difficulty in conducting sufficient scanning and rapid iteration under different structural parameters and operating conditions. Furthermore, many design methods treat the solder's melting point temperature as the primary or sole failure criterion, ignoring the significant temperature sensitivity of solder's mechanical properties (such as tensile strength, shear strength, and Young's modulus). In actual operating conditions, the solder's load-bearing capacity decreases significantly with increasing temperature even before it approaches its melting point. Simultaneously, the combined effect of external mechanical loads such as electrode preload and spring tension, along with thermal stress, causes a discrepancy between the structural margin judgment based solely on the melting point and the actual failure behavior, thus affecting the accurate prediction of the release mechanism's disconnection time. Traditional simulations often idealize the solder interface: either approximating a completely fixed rigid connection or instantaneously separating completely upon reaching a certain threshold. This type of treatment fails to reflect the progressive adhesion-peeling mechanism of solder under the combined action of thermal and mechanical stress, and ignores key physical processes such as interface damage evolution and energy competition of mixed-mode (tension / shear) fracture, resulting in inaccurate descriptions of the failure initiation and propagation sequence.

[0004] In the prior art, Chinese patent CN118446134A discloses a simulation method for a joint model of the motion of a mechanical switch arc ignition and repulsion mechanism, including the following steps: establishing a two-dimensional axisymmetric magnetohydrodynamic (MHD) arc model based on an experimental model, which includes a cup-shaped transverse and longitudinal magnetic contact copper electrode, a copper electrode, and a fluid domain; setting a flow field module, a thermal field module, an electric field module, and a magnetic field module based on the MHD arc model; setting a motion field model for the repulsion mechanism, including an electromagnetic field module and a solid mechanics field module; simulating the repulsion metal disk, the insulator tie rod spring, the armature for opening and closing, and the moving contact in the magnetohydrodynamic arc extinguishing chamber connected by the tie rod, based on the actual motion process of the mechanical switch; and performing mesh generation on the MHD arc model and the motion field model of the repulsion mechanism established in the above steps.

[0005] However, this method has the following limitations: existing technologies often only use the solder melting point temperature as the failure criterion, while ignoring the real behavior of its tensile strength, Young's modulus, etc., which decrease sharply with increasing temperature. In arc simulation, this method only considers the physical characteristics of arc plasma, without involving the mechanical degradation law of solder under TOV action, and it is difficult to reflect the essential mechanism of the disconnector disconnection time.

[0006] Therefore, developing a simulation method that can comprehensively consider material nonlinearity, multi-physics dynamic coupling, and the actual failure behavior of the weld interface, in order to accurately and efficiently predict the disconnection time of the internal release device of the SPD under TOV, has become an urgent need in the industry. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for predicting disconnection time of disconnectors based on multiphysics coupling simulation.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] This invention provides a method for predicting disconnection time of a disconnector based on multiphysics coupling simulation, comprising the following steps:

[0010] Establish a geometric model of the core moving parts of the release device. The core moving parts include a plastic base, a left copper electrode, a right copper electrode, a silver electrode, a copper electrode protrusion on the surface of the silver electrode, solder, a plastic plate, and a spring.

[0011] In the geometric model, the time-domain electric field equation of the decoupler conductor is established, and the current density and electric field strength are obtained by solving the time-domain electric field equation. The spatial loss distribution of each conductor part of the decoupler is then calculated.

[0012] The transient heat conduction equation of the deactivator is established and the boundary conditions for heat conduction, heat convection and heat radiation are set. Based on the spatial loss distribution of each conductor part, the transient temperature of each core action part of the deactivator is obtained.

[0013] Establish the finite deformation dynamic force field equation of the release device, and solve the thermal stress of each core action part of the release device based on the transient temperature of each core action part of the release device.

[0014] The displacement of each core moving part is calculated based on the thermal stress of each core moving part, combined with the electrode preload and spring force.

[0015] When the timing calculation shows that the solder displacement is greater than zero, the calculation time is the time when the disconnector disconnects.

[0016] Furthermore, in the geometric model, the right copper electrode is connected to ground potential, and the left copper electrode is the external voltage excitation terminal; the right copper electrode and the copper electrode protrusion on the surface of the silver electrode are connected by solder, and there is an electrode preload force between them in the contact direction in the initial assembly state; one end of the spring acts on the small hole at the upper end of the plastic plate, and the other end is fixed to the plastic base or a fixed support point corresponding to the plastic base. The spring is in a stretched state and applies a pulling force to the plastic plate; the plastic plate maintains close contact with the upper copper electrode under the action of the spring tension; the upper copper electrode is provided with a preset rotation axis or fulcrum relative to the plastic plate, so that when the solder connection fails, the upper copper electrode can be lifted in the direction opposite to the plastic plate under the action of the electrode preload force, and the plastic plate generates a relative displacement around the rotation axis under the action of the spring tension, thereby realizing the relative separation of the solder connection.

[0017] Furthermore, the conductor portion of the disconnector includes a left copper electrode, a right copper electrode, a silver electrode, a copper electrode bump on the surface of the silver electrode, solder, and a metal oxide varistor with nonlinear conductivity characteristics.

[0018] Furthermore, the time-domain electric field equation is:

[0019] J i =σ i E i +J e,i

[0020]

[0021] Among them, J i E i Let σ represent the current density and electric field strength of the i-th conductor portion, respectively. i J represents the conductivity of the i-th conductor portion. e,iThis represents the source of applied current density applied to the i-th conductor portion. V represents the spatial gradient operator. i This represents the electric potential of the i-th conductor section.

[0022] Furthermore, the spatial loss distribution is expressed by the following formula:

[0023] P liss,i =J i ·E i

[0024] Among them, P loss,i J represents the volumetric power dissipation density of the i-th conductor portion. i E i Let represent the current density and electric field strength of the i-th conductor section, respectively.

[0025] Furthermore, the transient heat conduction equation is as follows:

[0026]

[0027] Where, ρ i C represents the density of the i-th core action part. p,i T represents the constant-pressure heat capacity of the i-th core action part. i U represents the transient temperature of the i-th core action part, t represents time, and u v q represents the external fluid velocity vector. i This represents the heat flux vector of the i-th core action part. For the spatial gradient operator, P loss,i P represents the volumetric power dissipation density of the i-th core action part. When the core action part is not a conductor, P loss,i =0; Q ted,i This represents the external heat source term acting on the i-th core action part;

[0028] At the boundary, the heat flux satisfies both convection and radiation boundary conditions:

[0029]

[0030] Where n represents the outer boundary normal vector, k i h represents the thermal conductivity of the i-th core action part. i T represents the convective heat transfer coefficient of the i-th core action part. s,i T represents the surface temperature of the i-th core action part. a For ambient temperature, ε i σ represents the surface emissivity of the i-th core action site. sis the Stefan-Boltzmann constant.

[0031] Furthermore, the force field equations for the finite deformation dynamics are as follows:

[0032]

[0033]

[0034]

[0035]

[0036] Among them, S i S represents the thermal stress at the i-th core action part. inel,i S el,i ε represents the elastic stress component and the inelastic stress component of the i-th core action part, respectively; el,i F represents the elastic Green-Lagrange strain tensor of the i-th core action site; el,i F inel,i F th,i Let ε represent the elastic, inelastic, and thermal deformation gradient tensors of the i-th core action part, respectively; th,i Let α represent the thermal strain tensor of the i-th core action part. i T represents the linear expansion coefficient of the i-th core action part. i Let T be the transient temperature of the i-th core action part. ref Let I be the reference temperature, and F be the identity matrix. i c represents the total deformation gradient tensor of the i-th core action part. i This represents the fourth-order elastic stiffness tensor of the i-th core motion component, determined based on the Young's modulus and Poisson's ratio of the i-th core motion component. i S represents the Jacobian determinant of the i-th core moving part due to inelastic and thermal deformation. 0,i S represents the initial stress of the i-th core action part. ext,i S represents the external stress contribution of the i-th core action part. q,i This represents the other inelastic or history-dependent contributions of the i-th core action part. Let u represent the displacement gradient of the i-th core action part. i Let T represent the displacement of the i-th core action part, and T represent transpose.

[0037] Furthermore, regarding the displacement constraints and elastic / contact mechanics treatment of each core moving part, the finite deformation dynamic force field equations satisfy the following constraints and models:

[0038] Displacement constraint of plastic plate: The plastic plate moves only in the xy plane of the geometric model, and one end moves around a preset rotation axis; for this purpose, the z-direction displacement component of the plastic plate is always zero in the global rectangular coordinate system, and the radial and axial displacement components of the plastic plate are restricted to zero in the cylindrical coordinate system with the intersection of the rotation axis and the xy plane as the origin.

[0039] Plastic base and fixing area constraints: The displacement of the plastic base, plug-in guide and other fixing areas is restricted in three directions;

[0040] The penalty function constraint for the contact between the plastic plate and the upper electrode: when the contact gap is less than or equal to zero, a restoring force proportional to the penetration depth is generated; when the contact gap is greater than zero, the restoring force is zero; the contact gap is the minimum distance between the surface of the plastic plate and the surface of the upper copper electrode in the contact normal direction.

[0041] Furthermore, the electrode preload and spring force are both simulated using a spring-damping function, where the spring force is proportional to the spring elongation and the damping force is proportional to the elongation rate. The spring stiffness coefficient and damping coefficient are determined based on electrode preload experiments, steady-state simulation results, or spring parameters, respectively.

[0042] Furthermore, the displacement of each core action part is given by the following formula:

[0043]

[0044]

[0045] Where, ρ i u represents the density of the i-th core action part. i This represents the displacement of the i-th core action part. Let F represent the spatial gradient operator, t represent time, and F represent the time interval. i S represents the total deformation gradient tensor of the i-th core action part. i F represents the thermal stress at the i-th core action site. V,i The term represents the physical force acting on the i-th core action part, including electrode preload, spring force, and additional force caused by boundary conditions or external loads; I is the identity matrix, and T represents the transpose.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] (1) In the prior art, TOV tests of physical prototypes are often used to evaluate the action of the release mechanism. The test is costly, has poor repeatability, and is difficult to fully scan and iterate under different combinations of structural parameters and operating conditions. This invention establishes a multi-physics coupled numerical simulation model, which can repeatedly carry out computational experiments in a virtual environment and iterate rapidly in combination with different structural and operating parameters. This solves the problems of low efficiency and high cost of traditional tests and realizes low-cost, high-efficiency and repeatable release mechanism disconnection time prediction.

[0048] (2) To address the problem that existing release mechanism designs neglect the degradation of solder mechanical properties with temperature, this invention innovatively introduces dynamic solder parameters that vary with temperature. Traditional designs only use the solder melting point as the failure criterion, failing to consider the actual characteristics of solder parameters such as tensile strength and Young's modulus, which decrease with increasing temperature. This leads to deviations between the release mechanism's action time and the design expectation, indicating an unreasonable release mechanism structure design. This invention accurately reflects the nonlinear behavior of solder during transient temperature rises by embedding material functions calibrated through temperature rise tensile tests, making the disconnection time prediction more realistic and ensuring that the design of the release mechanism solder joints no longer solely relies on the solder melting point.

[0049] (3) Unlike existing simulations that simplify the solder surface to a fixed constraint or ideal separation, this invention constructs an adhesion-peel physical failure model, reproducing the mechanism of solder peeling in simulation for the first time. By introducing a temperature-compensated tensile strength threshold as the peeling criterion and coupling the synergistic effect of external stress (spring force, electrode preload) and thermal stress, the transient characteristics of interface stress reaching a critical state are accurately captured. This model effectively avoids prediction distortion caused by ignoring force field coupling and interface behavior, providing a highly reliable simulation tool for the structural optimization of SPD decouplers.

[0050] (4) Existing joint simulations of arc and motion mainly focus on the arc plasma process of mechanical switches, without addressing the mechanical degradation law of solder under TOV, thus failing to reflect the essential mechanism of SPD disconnection time. This invention solves the problem of the model failing to reflect the thermal-mechanical synergistic degradation of solder by coupling electro-thermal-mechanical multi-field equations and comprehensively considering the combined effects of external current-temperature rise and mechanical loads such as electrode preload and spring force, thus realizing a physical characterization of the disconnection time of the disconnector. Attached Figure Description

[0051] Figure 1 This is a flowchart of the disconnector disconnection time prediction method according to an embodiment of the present invention;

[0052] Figure 2 This is a schematic diagram of the geometric model of the SPD disconnector according to an embodiment of the present invention;

[0053] Figure 3This is a schematic diagram of the resistance-voltage curve of the MOV according to an embodiment of the present invention. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0055] Example 1:

[0056] The purpose of this invention is to solve the problem of insufficient accuracy in existing SPD disconnector disconnection time prediction methods due to neglecting material nonlinearity, multi-physics coupling effects and solder failure mechanisms. The invention provides a method for accurately predicting the solder peeling time of the SPD internal disconnector under TOV through dynamic coupling simulation of electro-thermal-mechanical fields, which significantly reduces experimental costs and improves design reliability.

[0057] This embodiment provides a method for predicting disconnector disconnection time based on multiphysics coupling simulation, such as... Figure 1 As shown, it includes the following steps:

[0058] Step S1: Establish the geometric model of the core moving parts of the release device, including the plastic base, the core moving parts including the left copper electrode, the right copper electrode, the silver electrode, the copper electrode protrusion on the surface of the silver electrode, solder, plastic plate and spring.

[0059] There's no need to model the entire SPD; you only need to build models of the core motion parts. For example... Figure 2 As shown:

[0060] The right copper electrode is grounded, and the left copper electrode is energized. The right copper electrode, after being welded to the copper electrode on the surface of the silver electrode, possesses a certain elasticity (electrode preload). One end of the spring acts at the small hole at the top of the plastic plate, connecting with the other end at the fixed point, forming the spring's direction of action as shown in the diagram. The spring is initially in a stretched state. Under normal conditions, the plastic plate is in close contact with the upper copper electrode under the spring tension. When the solder breaks due to force, the upper copper electrode rises under the preload, and the plastic plate, under the spring tension, displaces around its rotation axis, further severing the solder connection and extinguishing the arc.

[0061] Step S2: In the geometric model, establish the time-domain electric field equation for the conductor part of the decoupler, solve the time-domain electric field equation to obtain the current density and electric field strength, and calculate the spatial loss distribution of each conductor part of the decoupler.

[0062] The conductor portion of the decoupler includes a left copper electrode, a right copper electrode, a silver electrode, a copper electrode bump on the surface of the silver electrode, solder, and a metal oxide varistor with nonlinear conductivity characteristics.

[0063] Under the influence of transient overvoltage (TOV), it is necessary to calculate the electric field of the conductor portion in the SPD. This includes copper electrodes, silver electrodes, solder, and metal oxide varistors (MOVs) with nonlinear characteristics. The material parameters required for SPD electric field calculation are shown in Table 1 below.

[0064] Table 1

[0065] MOV copper electrode silver electrode solder plastic electrical conductivity <![CDATA[σ MOV ]]> <![CDATA[σ1]]> <![CDATA[σ2]]> <![CDATA[σ3]]> /

[0066] σ1, σ2, and σ3 are constants; plastic is considered an insulator and has no conductivity. MOV This is the conductivity of the MOV. σ MOV It is related to the voltage across the MOV. First, the resistance-voltage curve of the MOV is obtained through experimental data fitting, as shown below. Figure 3 As shown.

[0067] Figure 3 The following formula expresses the relationship between the resistance and voltage of an MOV, and the relationship between the conductivity and resistance of an MOV:

[0068]

[0069] Where l represents the thickness of the MOV, C represents the cross-sectional area of ​​the MOV, and R represents the resistance of the MOV, this equation combined with the resistance-voltage curve above yields the conductivity σ. MOV The relationship with voltage.

[0070] For the insulated plastic parts and the boundaries other than the voltage input terminal and the ground terminal, they are set to be electrically insulated, satisfying the following equation:

[0071] n·J=0

[0072] Where n represents the normal vector of the vertical edge, and J represents the current density.

[0073] The time-domain equations for a metal oxide varistor under a TOV voltage are expressed as follows:

[0074]

[0075] Where J represents current density; σ represents conductivity; E represents electric field strength; J e This represents an applied current density source; V represents the electric potential. This is the spatial gradient operator.

[0076] The input voltage is U TOVIts value is determined by the corresponding SPD test standard (such as GB / T 18802.11). Solving the above equations can solve for the current density and electric field strength of the SPD conductor.

[0077] The spatial loss density distribution of the SPD conductor portion is calculated based on the aforementioned electric field strength and current density, and its expression is as follows:

[0078] P loss =J·E

[0079] Among them, P loss This represents the spatial loss density distribution.

[0080] Step S3: Establish the transient heat conduction equation of the deactivator and set the boundary conditions for heat conduction, heat convection and heat radiation. Based on the spatial loss distribution of each conductor part, solve for the transient temperature of each core action part of the deactivator.

[0081] Under transient overvoltage (TOV) conditions, the primary heat-generating component in the SPD is the metal oxide varistor (MOV), which exhibits nonlinear characteristics. Other components (copper electrodes, silver electrodes, solder, and plastic) mainly function to conduct heat and exchange heat with the external environment. The MOV itself also dissipates heat to the outside through its surroundings. Therefore, the material parameters required for SPD thermal field calculations are shown in Table 2 below.

[0082] Table 2

[0083] MOV copper electrode silver electrode solder plastic density <![CDATA[ρ MOV ]]> <![CDATA[ρ1]]> <![CDATA[ρ2]]> <![CDATA[ρ3]]> <![CDATA[ρ4]]> Constant pressure heat capacity <![CDATA[Cp MOV ]]> <![CDATA[Cp1]]> <![CDATA[Cp2]]> <![CDATA[Cp3]]> <![CDATA[Cp4]]> thermal conductivity <![CDATA[k MOV ]]> <![CDATA[k1]]> <![CDATA[k2]]> <![CDATA[k3]]> <![CDATA[k4]]> Surface reflectivity <![CDATA[ε MOV ]]> <![CDATA[ε1]]> <![CDATA[ε2]]> <![CDATA[ε3]]> <![CDATA[ε4]]> coefficient of thermal expansion <![CDATA[α MOV ]]> <![CDATA[α1]]> <![CDATA[α2]]> <![CDATA[α3]]> <![CDATA[α4]]>

[0084] Constant pressure heat capacity refers to the heat absorbed or released per unit mass of material when the temperature changes under constant pressure. It is generally temperature-dependent. Since MOVs are the primary heat source and solder is the main research object, Cp is obtained using a DSC analyzer. MOV The curves showing the change of Cp3 with temperature are shown. The constant-pressure heat capacities Cp1, Cp2, and Cp4 of other materials are set as constants. In addition, the density ρ3 and thermal conductivity k3 of the solder are temperature-dependent and can be measured using standard experimental procedures. Due to the high complexity of the model, to reduce computational load, other material parameters in the table are considered temperature-independent constants. It has been verified that this simplification has a negligible impact on the results.

[0085] The transient heat conduction equation for a solid is:

[0086]

[0087] Where ρ represents the density of the solid material; C pThis refers to the heat absorbed or released per unit mass of material in a metal oxide varistor when its temperature changes under constant pressure, i.e., constant-pressure heat capacity; T represents temperature; t represents the time during which the thermal process occurs; u v This represents the velocity vector of an external fluid, such as air. P represents the net heat outflow rate caused by heat conduction. loss Represents the spatial loss density distribution; Q ted Indicates the external heat source term; This represents the temperature gradient.

[0088] In addition, the boundary conditions for thermal convection and thermal radiation on the surface of the metal oxide varistor are as follows:

[0089]

[0090] Where n represents the normal vector of the vertical edge; k represents the thermal conductivity of the solid; The temperature gradient is represented by ; h represents the convective heat transfer coefficient, which depends on the conditions of the laboratory being simulated, and h is a constant; T a Indicates ambient temperature; T s ε represents the surface temperature of the solid; ε represents the emissivity of the solid surface; σ s This represents the Stefan-Boltzmann constant.

[0091] Solving the transient heat conduction equation yields the transient temperature T of the SPD.

[0092] Step S4: Establish the finite deformation dynamic force field equation of the release device, and solve the thermal stress of each core action part of the release device based on the transient temperature of each core action part of the release device.

[0093] The material parameters required for solving the SPD force field are shown in Table 3 below:

[0094] Table 3

[0095] MOV copper electrode silver electrode solder plastic Young's modulus <![CDATA[E MOV ]]> <![CDATA[E1]]> <![CDATA[E2]]> <![CDATA[E3]]> <![CDATA[E4]]> Poisson's ratio <![CDATA[ν MOV ]]> <![CDATA[ν1]]> <![CDATA[ν2]]> <![CDATA[ν3]]> <![CDATA[ν4]]> coefficient of thermal expansion <![CDATA[α MOV ]]> <![CDATA[α1]]> <![CDATA[α2]]> <![CDATA[α3]]> <![CDATA[α4]]>

[0096] The Young's modulus E3 of solder is defined by the following formula:

[0097] E3 = 4 × 10 10 ×(1-0.003×(T solder -293.15))

[0098] In the formula, the unit of Young's modulus is Pa; T solder This indicates the temperature of the solder, measured in Kelvin (K).

[0099] All other parameters in the table can be considered constants.

[0100] In addition, to simulate the adhesion and peeling state of the solder interface, the following parameters of the solder also need to be input:

[0101] tensile strength Shear strength Stretching energy release rate Shear strength release rate Adhesion stiffness solder <![CDATA[σ t ]]> <![CDATA[σ s ]]> <![CDATA[G ct ]]> <![CDATA[G cs ]]> <![CDATA[k n ]]>

[0102] The parameters in the table will change with temperature, which can be obtained through temperature rise tensile testing of solder materials.

[0103] Step S5: Based on the thermal stress of each core moving part, combined with the electrode preload and spring force, calculate the displacement of each core moving part;

[0104] The momentum conservation equation describing the dynamic behavior of finite deformation in solid mechanics is as follows. This equation is essentially the expression of Newton's second law in a continuous medium and is applicable to solving large deformation, geometric nonlinear, and transient mechanical problems:

[0105]

[0106]

[0107] in This represents the inertial force per unit volume, where ρ is density, u is the displacement vector, and t is time; the right side includes internal force terms and volume force terms. Characterizes the contribution of internal forces caused by stress. Let S be the spatial gradient operator, where S is the total stress and the superscript T is the matrix transpose. V Describing the volume force contribution, deformation gradient tensor Through the unit tensor I and displacement gradient Describe the local deformation of a material (including tension and rotation).

[0108] The finite deformation dynamics framework is extended by the following equations to introduce inelastic behaviors such as thermal expansion of materials.

[0109] S = S ine1 +S e1

[0110]

[0111] F th =I th +∈ th

[0112] ∈ th =α(TT) ref )

[0113] S e1 =j i (F inel F th ) -1 (c:∈e1 (F) inel F th ) -T

[0114] c = c(E, v)

[0115] S ine1 =S0+S ext +S q

[0116]

[0117] The total stress S is decomposed into an elastic component S0. el Inelastic part S inel ;

[0118] Elastic stress through constitutive relation S e1 =j i (F inel F th ) -1 (c:∈ e1 (F) inel F th ) -T Calculate, where c is the fourth-order elastic stiffness tensor (defined by Young's modulus E and Poisson's ratio v), It is the elastic Green-Lagrange strain tensor and the inelastic deformation gradient F. inel F th Describes permanent deformation, where F inel F represents the gradient of the original inelastic deformation. th F represents the thermal expansion deformation gradient. th Defined as the identity tensor plus the thermal strain tensor ∈ th ,∈ th The thermal expansion coefficient function α of the material and (TT) ref The product of (TT) is determined. ref The ) indicates that the transient temperature T calculated in step 3 is relative to the reference temperature F. ref The change in (F) inel F th The inverse of the elastic deformation gradient and the total deformation gradient F together determine the elastic deformation gradient.

[0119] Inelastic stress S inel Includes initial stress S0, external contribution S ext Other contributions S q Total strain It fully represents the geometric relationships of finite deformation.

[0120] For the plastic plate (state indicator), its displacement needs to satisfy the following two constraints: (1) the plastic plate moves only in the xy plane; (2) one end moves around the rotation axis. For the first constraint, its displacement component in the z direction is always 0, i.e., u z =0 to achieve this; for the second constraint, first establish a cylindrical coordinate system with the origin at the intersection of the rotation axis and the xy plane, then specify that the displacement components of the plastic plate in this cylindrical coordinate system are 0 in the r and a directions, and the displacement in the φ direction is not restricted, i.e., u r =0 and u a =0.

[0121] For fixed areas such as the base and pluggable copper electrodes, the displacement in all directions is restricted to 0, i.e., u = 0.

[0122] For tight contact between the plastic plate (status indicator) and the upper copper electrode, a penalty function is defined to prevent geometric penetration. That is, the following formula:

[0123]

[0124] Wherein the normal contact stress T n By defining a piecewise function, when the contact gap g n ≤0 indicates contact penetration has occurred, at which point a restoring force -p is generated that is proportional to the penetration depth. n g n Its direction is perpendicular to the contact surface, and the negative sign indicates resistance to penetration; when g n >0 indicates no contact, in which case the force is zero. Penalty stiffness p n The virtual stiffness of the contact interface is characterized by the characteristic elastic modulus E. ch The minimum geometric dimension h reflects the stiffness characteristics of a material. min To ensure numerical stability, both factors together constitute a reasonable contact stiffness.

[0125] The preload of the upper electrode after welding, and the tension of the actual spring, are both simulated using a spring-damping function. The spring-damping function is as follows:

[0126]

[0127] F s =k s Δl

[0128]

[0129] Δl=l-l0

[0130] l = Px b1 -x a1 P

[0131] l0 = Pxb0 -x a0 P

[0132] x a1 =x a0

[0133] x b1 =x b0 +u dx

[0134] Where F represents the resultant force vector of the spring, which consists of the elastic force F s and damping force F d composition, This represents a unit vector along the direction of the spring. x a0 and x b0 Indicates the initial position of the spring, x a0 As the source point, x b0 x is the target point; a1 and x b1 Indicates the current position of the spring, x a1 As the source point, x b1 The target point is Δl; Δl represents the elongation, which is the difference between the current length l and the free length l0; the elastic force follows Hooke's Law and is proportional to the elongation; k s Indicates the spring stiffness coefficient (unit: N / m, controls the magnitude of the elastic force); damping force F d with elongation rate Proportional; damping coefficient c s Control of velocity-related dissipative forces, in units of N·s / m; u dx This represents the displacement vector.

[0135] To apply the preload force to the upper electrode after welding, press the upper electrode until it contacts the surface of the silver electrode, and let the midpoint of the contact line be x. a0 x a0 The corresponding point when the upper electrode is not pressed is x. b0 x a1 With x a0 Overlap, x a1 The corresponding point where the upper electrode is pressed to the welding position is x. b1 Finally, the virtual spring's k s and c s The preload can be obtained from electrode preload test experiments or steady-state simulations and then calculated. Thus, the model has an initial virtual spring force to simulate the electrode preload after electrode welding.

[0136] For the tension of a physical spring, the actual fixed end of the spring is selected as the source point x. a0 With x a1 The point of action of the spring on the plastic plate (status indicator) is taken as the target point x. b1Specify its free length l0, which can be obtained from l0 = Px b0 -x a0 P and the spring direction vector Calculate x b0 The k of the physical spring s and c s This can be obtained through manufacturer data or independent testing, thus completing the modeling of the actual spring.

[0137] Finally, the peeling conditions of the solder interface need to be defined: For the solder interface, in addition to defining the inelastic deformation behavior, additional equations are needed to define the nonlinear mechanical behavior of the bond interface:

[0138]

[0139] f2=k1u-d×k1u

[0140] d = F -1 (u max ,σ t ,σ s G ct G cs )

[0141]

[0142] Among them, the normal contact force f1 is defined by a piecewise function, when the normal traction force T n When the adhesion strength threshold p0 is exceeded, an elastic force k1 proportional to the displacement u is generated, which is the interface stiffness; otherwise, the force is 0. The displacement u is decomposed into normal components {0,0,g}. n+} and tangential components Two parts, g n+ This refers to the gap function g. n The positive part, the tangential component is passed through the rotation matrix T b The local tangential displacement g t Transform to the global coordinate system; damage evolution is described by the damage variable d, the value of which is determined by the historical maximum displacement u. max Tensile strength σ t Shear strength σ t Type I fracture energy G ct and Type II fracture energy G cs Jointly determined; the effective force after damage is f2 = k1u - d × k1u, representing the initial elastic force k1u minus the damage dissipation d × k1u; the hybrid mode failure criterion is determined by a power law. Control, where G I G represents the type I energy release rate under the current loading conditions. IIα0 represents the type II energy release rate under the current loading conditions, and α0 is an empirical index. This criterion quantifies the energy competition mechanism between tensile and shear failure.

[0143] Step S6: When the timing calculation shows that the solder displacement is greater than zero, this moment is the time when the disconnector is disconnected.

[0144] By solving the above equations, the transient displacement of the SPD as a whole under thermal and external stresses can be obtained. This includes the displacement of the welding surface. If the displacement of the welding surface is 0, the weld joint is still valid. When the welding surface is displaced, the weld joint fails.

[0145] Example 2:

[0146] This embodiment provides a disconnector disconnection time prediction system based on multiphysics coupling simulation, including:

[0147] The thermo-electric coupling simulation module is used to establish a temperature field model of metal oxide varistors (MOVs) and solder joints under transient overvoltage, and to calculate the temperature rise distribution in the solder area based on the current input.

[0148] The mechanical simulation module is used to introduce temperature-related mechanical property degradation laws on the basis of temperature rise distribution, and to calculate the stress and strain distribution of solder under the combined action of electrode preload, spring force and thermal stress.

[0149] The interface damage evolution module is used to model the adhesion-peeling process of the solder-electrode interface, and simulate the gradual degradation and failure propagation process of the solder joint under the action of tensile and shear coupling.

[0150] The kinematic analysis module is used to calculate the kinematic response of the electrode separation triggered when the solder failure criterion is met, and to calculate the disconnection behavior of the disconnector and its corresponding disconnection time.

[0151] The data processing and prediction module is used to perform statistical analysis and time extraction on the simulation results, generating predicted disconnection time data under different structural parameters and operating conditions.

[0152] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0153] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for predicting the disconnection time of a disconnector based on multiphysics coupling simulation, characterized in that, Includes the following steps: Establish a geometric model of the core moving parts of the release device. The core moving parts include a plastic base, a left copper electrode, a right copper electrode, a silver electrode, a copper electrode protrusion on the surface of the silver electrode, solder, a plastic plate, and a spring. In the geometric model, the time-domain electric field equation of the decoupler conductor is established, and the current density and electric field strength are obtained by solving the time-domain electric field equation. The spatial loss distribution of each conductor part of the decoupler is then calculated. The transient heat conduction equation of the deactivator is established and the boundary conditions for heat conduction, heat convection and heat radiation are set. Based on the spatial loss distribution of each conductor part, the transient temperature of each core action part of the deactivator is obtained. Establish the finite deformation dynamic force field equation of the release device, and solve the thermal stress of each core action part of the release device based on the transient temperature of each core action part of the release device. The displacement of each core moving part is calculated based on the thermal stress of each core moving part, combined with the electrode preload and spring force. When the timing calculation shows that the solder displacement is greater than zero, the calculation time is the time when the disconnector is disconnected.

2. The method for predicting disconnection time of a disconnector based on multiphysics coupling simulation according to claim 1, characterized in that, In the geometric model, the right copper electrode is connected to ground potential, and the left copper electrode is the external voltage excitation terminal. The right copper electrode and the copper electrode protrusion on the surface of the silver electrode are connected by solder, and there is an electrode preload force between them in the contact direction in the initial assembly state. One end of the spring acts on the small hole at the upper end of the plastic plate, and the other end is fixed to the plastic base or a fixed support point corresponding to the plastic base. The spring is under tension in the initial state and applies a pulling force to the plastic plate. Under the action of the spring tension, the plastic plate maintains close contact with the upper copper electrode. The upper copper electrode is provided with a preset rotation axis or fulcrum relative to the plastic plate, so that when the solder connection fails, the upper copper electrode can be lifted in the direction opposite to the plastic plate under the action of the electrode preload force, and the plastic plate generates a relative displacement around the rotation axis under the action of the spring tension, thereby realizing the relative separation of the solder connection.

3. The method for predicting disconnection time of a disconnector based on multiphysics coupling simulation according to claim 1, characterized in that, The conductor portion of the decoupler includes a left copper electrode, a right copper electrode, a silver electrode, a copper electrode bump on the surface of the silver electrode, solder, and a metal oxide varistor with nonlinear conductivity characteristics.

4. The method for predicting disconnection time of a disconnector based on multiphysics coupling simulation according to claim 1, characterized in that, The time-domain electric field equation is: J i =σ i AND i +J e,i Among them, J i E i Let σ represent the current density and electric field strength of the i-th conductor portion, respectively. i J represents the conductivity of the i-th conductor portion. e,i This represents the source of applied current density applied to the i-th conductor portion. V represents the spatial gradient operator. i This represents the electric potential of the i-th conductor section.

5. The method for predicting disconnection time of a disconnector based on multiphysics coupling simulation according to claim 1, characterized in that, The spatial loss distribution is formulated as follows: Q loss,i =J i ·HAVE BEEN i Among them, P loss,i J represents the volumetric power dissipation density of the i-th conductor portion. i E i Let represent the current density and electric field strength of the i-th conductor section, respectively.

6. The method for predicting disconnection time of a disconnector based on multiphysics coupling simulation according to claim 1, characterized in that, The transient heat conduction equation is as follows: Where, ρ i C represents the density of the i-th core action part. p,i T represents the constant-pressure heat capacity of the i-th core action part. i U represents the transient temperature of the i-th core action part, t represents time, and u v q represents the external fluid velocity vector. i This represents the heat flux vector of the i-th core action part. For the spatial gradient operator, P loss,i P represents the volumetric power dissipation density of the i-th core action part. When the core action part is not a conductor, P loss,i =0; Q ted,i This represents the external heat source term acting on the i-th core action part; At the boundary, the heat flux satisfies both convection and radiation boundary conditions: Where n represents the outer boundary normal vector, k i h represents the thermal conductivity of the i-th core action part. i T represents the convective heat transfer coefficient of the i-th core action part. s,i T represents the surface temperature of the i-th core action part. a For ambient temperature, ε i σ represents the surface emissivity of the i-th core action site. s is the Stefan-Boltzmann constant.

7. The method for predicting disconnection time of a disconnector based on multiphysics coupling simulation according to claim 1, characterized in that, The force field equations for the finite deformation dynamics are as follows: S i =S inel,i +S el,i F th,i =I+e th,i ,he th,i =a i (T i -T ref ) S el,i =j i (F inel,i F th,i ) -1 (c i :ε el,i )(F inel,i F th,i ) -T S inel,i =S 0,i +S ext,i +S q,i Among them, S i S represents the thermal stress at the i-th core action part. inel,i S el,i ε represents the elastic stress component and the inelastic stress component of the i-th core action part, respectively; el,i F represents the elastic Green-Lagrange strain tensor of the i-th core action site; el,i F inel,i F th,i Let ε represent the elastic, inelastic, and thermal deformation gradient tensors of the i-th core action part, respectively; tj,i Let α represent the thermal strain tensor of the i-th core action part. i T represents the linear expansion coefficient of the i-th core action part. i Let T be the transient temperature of the i-th core action part. ref Let I be the reference temperature, and F be the identity matrix. i c represents the total deformation gradient tensor of the i-th core action part. i This represents the fourth-order elastic stiffness tensor of the i-th core motion component, determined based on the Young's modulus and Poisson's ratio of the i-th core motion component. i S represents the Jacobian determinant of the i-th core moving part due to inelastic and thermal deformation. 0,i S represents the initial stress of the i-th core action part. ext,i S represents the external stress contribution of the i-th core action part. q,i This represents the other inelastic or history-dependent contributions of the i-th core action part. Let u represent the displacement gradient of the i-th core action part. i Let T represent the displacement of the i-th core action part, and T represent transpose.

8. A method for predicting disconnection time of a disconnector based on multiphysics coupling simulation according to claim 1 or 7, characterized in that, For the displacement constraints and elastic / contact mechanics treatment of each core moving part, the finite deformation dynamic force field equations satisfy the following constraints and models: Displacement constraint of plastic plate: The plastic plate moves only in the xy plane of the geometric model, and one end moves around a preset rotation axis; for this purpose, the z-direction displacement component of the plastic plate is always zero in the global rectangular coordinate system, and the radial and axial displacement components of the plastic plate are restricted to zero in the cylindrical coordinate system with the intersection of the rotation axis and the xy plane as the origin. Plastic base and fixing area constraints: The displacement of the plastic base, plug-in guide and other fixing areas is restricted in three directions; The penalty function constraint for the contact between the plastic plate and the upper electrode: when the contact gap is less than or equal to zero, a restoring force proportional to the penetration depth is generated; when the contact gap is greater than zero, the restoring force is zero; the contact gap is the minimum distance between the surface of the plastic plate and the surface of the upper copper electrode in the contact normal direction.

9. The method for predicting disconnection time of a disconnector based on multiphysics coupling simulation according to claim 1, characterized in that, The electrode preload and spring force are simulated using a spring-damping function, where the spring force is proportional to the spring elongation and the damping force is proportional to the elongation rate. The spring stiffness coefficient and damping coefficient are determined based on electrode preload experiments, steady-state simulation results, or spring parameters, respectively.

10. The method for predicting disconnection time of a disconnector based on multiphysics coupling simulation according to claim 1, characterized in that, The displacement of each core action part is given by the following formula: Where, ρ i u represents the density of the i-th core action part. i This represents the displacement of the i-th core action part. Let F represent the spatial gradient operator, t represent time, and F represent the time interval. i S represents the total deformation gradient tensor of the i-th core action part. i F represents the thermal stress at the i-th core action site. V,i The term represents the physical force acting on the i-th core action part, including electrode preload, spring force, and additional force caused by boundary conditions or external loads; I is the identity matrix, and T represents the transpose.

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