A structural mechanics reliability analysis method for container mobile laboratory

Abstract

The present invention belongs to the technical field of reliability analysis, and discloses a reliability analysis method for the structural mechanics of a container mobile laboratory; the method comprises: obtaining container load data and container basic data, and establishing a container finite element model based on the container load data and the container basic data; obtaining a unit stress field and a deformation amplitude of the container based on the container finite element model; determining a failure mode of the container finite element model based on the unit stress field and the deformation amplitude, and calculating a reliability index of the failure mode; calculating a failure probability of the failure mode based on the failure mode and its corresponding reliability index, and sending the result to a reliability analysis terminal, thereby improving the design quality, use safety and reliability of the container mobile laboratory.

Description

Technical Field

[0001] The present invention relates to the technical field of reliability analysis, and more specifically, to a structural mechanics reliability analysis method for a container mobile laboratory. Background Art

[0002] The patent application publication number CN115169020A discloses a reliability analysis method for a truss structure system based on an automatic updating model, the method comprising: establishing a truss finite element model of the truss structure to be analyzed; fitting a response surface equation based on the member stress output by the truss finite element model, and establishing a functional function for each member; establishing an optimization model based on the geometric meaning and functional function of the reliability index; calculating the reliability index of each member, and when it is determined that the reliability indexes of all members have converged using an iterative criterion, obtaining multiple failure modes for characterizing the failure of the truss structure based on the reliability index of each member, each failure mode including a failure path; calculating the reliability index and failure probability of each failure mode; using PNET to calculate the reliability index and failure probability of the truss structure, which overcomes the problem of implicit functional functions and has higher accuracy.

[0003] However, the existing analysis methods in the field of container mobile laboratories still lack specialized analysis methods for special structures. The existing general methods cannot fully consider the special working conditions and constraints of containers, and it is difficult to comprehensively evaluate their structural safety and reliability. Secondly, the existing modeling methods are too simplified and cannot accurately describe the actual state of the container, resulting in deviations between the model and the actual structure, and the analysis accuracy is not high. Furthermore, the existing analysis only considers a single or partial failure mode, and fails to comprehensively evaluate the potential failure risk of the container under complex working conditions. The analysis results lack comprehensiveness. At the same time, the uncertainty of parameters such as materials, geometry, and loads is ignored, and the actual situation is not truly reflected, resulting in deviations in the reliability evaluation results. In addition, the calculation efficiency is low, the cycle is long, and the analysis results cannot be obtained quickly, which makes it difficult to meet the actual needs of the project. The accuracy and comprehensiveness of the analysis results need to be improved.

[0004] In view of this, the present invention proposes a container mobile laboratory structural mechanics reliability analysis method to solve the above problems. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art and to achieve the above-mentioned purpose, the present invention provides the following technical solutions: A method for structural mechanics reliability analysis of a container mobile laboratory, comprising: S1, obtaining container load data and container basic data, and establishing a container finite element model based on the container load data and container basic data;

[0006] S2. Based on the container finite element model, obtain the unit stress field and deformation amplitude of the container;

[0007] S3. Based on the unit stress field and deformation amplitude, determine the failure mode of the container finite element model and calculate the reliability index of the failure mode;

[0008] S4. Based on the failure mode and its corresponding reliability index, the failure probability of the failure mode is calculated and sent to the reliability analysis terminal.

[0009] Furthermore, the container load data includes static load and dynamic load; the container basic data includes geometric dimensions and material attribute data of the container; the geometric dimensions include length, width and height; the material attribute data includes wall thickness and material type;

[0010] Static loads include instrument deadweight load data and container deadweight load data; dynamic loads include instrument inertia load data, instrument vibration load data, and instrument impact load data.

[0011] Furthermore, the method of establishing the container finite element model includes:

[0012] According to the geometric dimensions of the container, a three-dimensional geometric model of the container is established; and based on the wall thickness of the container, the three-dimensional geometric model is refined to obtain a refined geometric model;

[0013] According to the material type, the geometric model will be refined to define the corresponding material properties, including elastic modulus, Poisson's ratio and density;

[0014] The refined geometric model is divided into shell units to generate a finite element mesh model; based on the finite element mesh model, the instrument's own weight load data is applied to the corresponding instrument installation position, and the finite element mesh model is given the container's own weight load data; the instrument's inertial load data is converted into corresponding acceleration or force and applied to the instrument installation position; the instrument's vibration load data is converted into vibration excitation and applied to the corresponding instrument installation position; the instrument's impact load data is converted into impact force or acceleration time history and applied to the corresponding instrument installation position, thus completing the establishment of the container's finite element model.

[0015] Furthermore, the method of refining the three-dimensional geometric model includes:

[0016] The three-dimensional geometric model is initially divided into n grid units, and the average thickness of each grid unit is calculated; based on the average thickness of each grid unit, the n grid units are divided into n1 new grid units; recorded as n1 subdivided grid units;

[0017] Select M2 subdivided grid cells from n1 subdivided grid cells as seed cells, and build a priority queue for each seed cell; the elements in the priority queue are the neighboring cells of the seed cell;

[0018] Define the growth region, and for each seed unit, add neighboring units to the growth region in sequence according to the order in its priority queue until the stop condition is met; obtain M2 regional grids; reconstruct the topological relationship based on the M2 regional grids, and finally obtain M partitions; define the thickness value of each partition, that is, obtain a refined geometric model;

[0019] The method of defining the thickness value includes:

[0020] Define the thickness distribution function ; is the three-dimensional coordinate of the node on the three-dimensional geometric model. For each grid unit in each partition, the corresponding thickness value is obtained in the corresponding thickness distribution function according to its centroid coordinate, thus completing the definition of the thickness value.

[0021] Thickness distribution function ;in, is a constant coefficient, is the characteristic size of the container, is the elastic modulus of the material, is the section moment of inertia, is the distributed load, is the bending moment load.

[0022] Furthermore, the method of calculating the average thickness of each grid unit includes:

[0023] Define the average value on the 3D geometric model nodes, for each node , calculate its relationship with adjacent nodes The rate of change of the normal vector ,in, For Node The normal vector of For Node The normal vector of the preset change rate threshold; when the normal vector change rate When the change rate is greater than the threshold, the node is defined Located in a corner area;

[0024] For nodes defined within the corner region , giving it a thickness weight ; For nodes that are not in the corner area, assign them a thickness weight of 1;

[0025] ;in, For Node The wall thickness gradient value at and is the magnification factor, For Node The proportion of the grid cell volume occupied;

[0026] ;in, For the node The relevant volume fraction, For the The total volume of the grid cells, is the average volume of the grid cells, is the regularization parameter;

[0027] Ways to obtain include:

[0028] Find the containing node For all grid cells containing nodes A new small polyhedron is constructed so that the nodes is a vertex of the small polyhedron, and the sum of the volumes of all constructed small polyhedrons is calculated as ;

[0029] ;in, is the wall thickness at node j, is the first The wall thickness at each node is For the The basis functions of the nodes, is the basis function At the node The gradient at For the The weight coefficient of each node, For Node The total number of nodes in the neighborhood;

[0030] ;in, For Node and The distance is the influence radius parameter; then The average thickness of the grid cells .

[0031] Furthermore, the method of dividing the n grid units into n1 new grid units includes:

[0032] Get grid cells The neighborhood unit set , the neighborhood unit set Contains grid cells All adjacent grid cells that share a node or edge are recorded as neighborhood cells;

[0033] Computational Grid Cells The maximum thickness difference with its neighboring cells ;in, For grid cells The average thickness of For grid cells Neighborhood unit The average thickness of

[0034] Preset thickness difference threshold range [t_min,t_max] ;like In [t_min,t_max] , then the grid cells The average is refined into two grid cells at a time; if Greater than , then the grid cells The average is refined into four grid cells at a time;

[0035] The original grid cells are combined with the grid cells obtained by average refinement to obtain n1 new grid cells.

[0036] Furthermore, the unit stress field and deformation amplitude are obtained by:

[0037] For each shell element , based on the element shape function and material properties, the corresponding element stiffness matrix is ​​calculated ; Assemble the unit stiffness matrices of all shell elements to obtain the total stiffness matrix of the entire container finite element model ; Element stiffness matrix The displacement strain function Integrate to obtain; ,in, , is the elastic matrix; for The transpose of is the derivative of the shape function, is the coordinate Jacobian matrix;

[0038] For each shell element , calculate the corresponding unit mass matrix And assembled into the total mass matrix of the entire container finite element model ; Based on the total mass matrix And the node loads, construct the total load matrix ;

[0039] Solving Linear Equations , and obtain the node displacement matrix ; For each shell element , according to the unit shape function and the nodal displacement matrix , the corresponding shell element displacement field is calculated , for the shell element displacement field Perform differentiation operation to obtain the corresponding shell element strain field ; then the shell element The corresponding element stress field ; The deformation amplitude is the absolute value of the nodal displacement of the shell element in the nodal displacement matrix.

[0040] Furthermore, the method for determining the failure mode includes:

[0041] Based on the element stress field, each shell element is calculated The equivalent stress ;

[0042] s v _e = [ ( s x - s y) 2 + ( s y - s z) 2 + ( s z - s x) 2 +6( t xyz 2 + t yz 2 + t zx 2 )] 1 2 ;in, , and are the components of the normal stress of the shell element in the three-dimensional directions, , and They are the components of the shear stress of the shell element in the three-dimensional directions;

[0043] Preset equivalent stress threshold ; For each shell element ,like Greater than , then the shell element Add stress concentration area element set ;

[0044] For stress concentration area element sets Each shell element in , calculate the yield margin ;

[0045] ;in, is the characteristic value of the material yield strength of the shell element, is the yield strength uncertainty correction factor, is the material yield criterion index;

[0046] like , then define the shell element The failure mode is yielding;

[0047] For stress concentration area element sets Each shell element in , calculate the fracture margin ;

[0048] ;in, is the uncertainty correction factor of ultimate strength; is the strain triaxiality correction factor, is the material fracture criterion index; is the characteristic value of the material ultimate strength of the shell element;

[0049] Strain triaxiality correction factor ;in, is the equivalent Poisson's ratio; if , then define the shell element The failure mode is fracture;

[0050] Preset deformation threshold ; For all shell elements ,like Greater than , then the shell element Add deformation unit set ;

[0051] Deform the unit set Divide into K1 grid blocks, and for each grid block Perform eigenvalue analysis to obtain the block stiffness matrix KP; solve the eigenvalue of KP ;

[0052] like v is less than 0, the grid block Buckling occurs; if the shell element If the number of buckling blocks in the shell element exceeds the preset buckling threshold, the shell element The failure mode is buckling;

[0053] Get the SN curve of the material; for each shell element ; According to the stress-strain cycle amplitude and SN curve, the fatigue life cycle number is calculated ;

[0054] If all Less than the preset life cycle number Shell elements, add fatigue crack initiation set PUY;

[0055] For each shell element in PUY , a crack extension model is established, and the expression of the crack extension model is: ;in, is the crack size, is the number of cycles, and is the material constant, is the stress intensity factor range; It indicates the increment of crack size per unit number of cycles;

[0056] based on The calculation method for crack size Perform cycle expansion analysis when Reaching the preset critical size When the corresponding shell element is determined If the number of cycles when the failure is judged to be less than the failure threshold, the corresponding shell element The failure mode is fatigue crack;

[0057] All the failure modes are summarized to obtain the failure mode of the container finite element model.

[0058] Furthermore, the calculation method of the reliability index includes:

[0059] For each failure mode ; Establish the corresponding limit state equation ;in, Failure Mode The structural resistance of Failure Mode The structural effect of is the basic random variable vector;

[0060] For each elementary random variable , determine its statistical distribution type, and calculate its statistical distribution parameters;

[0061] For each failure mode The limit state equation , according to the statistical distribution parameters of the basic random variable X, calculate The corresponding mean and standard deviation ;

[0062] Failure Mode Corresponding reliability index β_ s= [ m g _s- β' × s g _ s] [ s g _ s × (1+ I will )] ;in, is the reliability index correction coefficient, is the uncertainty correction coefficient of the reliability index.

[0063] Furthermore, the method for obtaining the failure probability includes:

[0064] Failure Mode Corresponding reliability index Standardization to obtain standard normal distribution variables ; Calculate the standard normal distribution variable The corresponding probability value ; Probability value Failure Mode The corresponding failure probability.

[0065] The technical effects and advantages of the structural mechanics reliability analysis method of a container mobile laboratory of the present invention are as follows:

[0066] The present invention comprehensively, accurately and reasonably analyzes the structural safety and reliability of the container mobile laboratory; by establishing an accurate finite element model, static and dynamic loads are fully considered, and the analysis accuracy is greatly improved by accurately simulating the changes in container wall thickness, especially in stress concentration areas; and a variety of failure modes are integrated to comprehensively evaluate the potential failure risks of containers; by introducing a reliability index calculation method based on the limit state equation, the uncertainty of multiple parameters is considered to make the analysis results more in line with the actual situation; at the same time, the analysis results can be obtained quickly, which significantly improves the analysis efficiency; in addition, factors such as the spatial distribution of material properties, stress concentration effects and fatigue crack propagation are taken into account, which further improves the comprehensiveness and accuracy of the analysis; overall, the design quality, safety in use and reliability of the container mobile laboratory are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 A schematic diagram of a structural mechanics reliability analysis method for a container mobile laboratory according to the present invention;

[0068] Figure 2 The present invention is a schematic diagram of a container mobile laboratory structural mechanics reliability analysis system. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] Example 1

[0071] See also Figure 1 As shown, this embodiment provides a structural mechanics reliability analysis method for a container mobile laboratory, including:

[0072] S1. Obtain container load data and container basic data, and establish a container finite element model based on the container load data and container basic data;

[0073] S2. Based on the container finite element model, obtain the unit stress field and deformation amplitude of the container;

[0074] S3. Based on the unit stress field and deformation amplitude, determine the failure mode of the container finite element model and calculate the reliability index of the failure mode;

[0075] S4. Based on the failure mode and its corresponding reliability index, the failure probability of the failure mode is calculated and sent to the reliability analysis terminal.

[0076] Furthermore, the container load data includes static load and dynamic load; the container basic data includes the geometric dimensions and material attribute data of the container; the geometric dimensions include length, width and height; the material attribute data includes wall thickness and material type; the wall thickness collection points are sufficient at different positions of the wall panel;

[0077] Static load includes instrument deadweight load data and container deadweight load data;

[0078] Dynamic loads include instrument inertia load data, instrument vibration load data, and instrument impact load data;

[0079] It should be noted that the instrument deadweight load data and container deadweight load data refer to the gravity load of the instruments and equipment installed inside the container and the gravity load of the container itself, respectively.

[0080] The instrument inertia load data refers to the inertia force load data generated by the instruments and equipment inside the container when they are running. The instrument vibration load data refers to the vibration load data generated by the instruments and equipment inside the container when they are running, including the load data caused by the vibration frequency and amplitude.

[0081] The instrument impact load data refers to the impact load generated by the instruments and equipment inside the container during the start-up and stop processes.

[0082] Further, the methods of establishing the container finite element model include:

[0083] According to the geometric dimensions of the container, a three-dimensional geometric model of the container is established; and based on the wall thickness of the container, the three-dimensional geometric model is refined to obtain a refined geometric model;

[0084] According to the material type, the geometric model will be refined to define the corresponding material properties, including elastic modulus, Poisson's ratio and density; in this process, different materials used in different structural components are distinguished and defined;

[0085] Ways to refine a 3D geometric model include:

[0086] The three-dimensional geometric model is initially divided into n grid cells, and the average thickness of each grid cell is calculated;

[0087] Specifically, the average definition on the three-dimensional geometric model nodes, for each node , calculate its relationship with adjacent nodes The rate of change of the normal vector ,in, For Node The normal vector of For Node The normal vector of the preset change rate threshold; when the normal vector change rate When the change rate is greater than the threshold, the node is defined Located in a corner area;

[0088] For nodes defined within the corner region , giving it a thickness weight ; For nodes that are not in the corner area, assign them a thickness weight of 1;

[0089] ;in, For Node The wall thickness gradient value at and is the magnification factor, For Node The proportion of the grid cell volume occupied ;in, For the node The relevant volume fraction, For the The total volume of the grid cells (referring to the geometric volume of the grid cell itself), is the average volume of the grid cells, is a regularization parameter, usually ranging from 0.01 to 0.1;

[0090] Ways to obtain include:

[0091] Find the containing node For all grid cells containing nodes A new small polyhedron (such as a hexahedron) is constructed so that the nodes is a vertex of the small polyhedron, and the sum of the volumes of all constructed small polyhedrons is calculated as ;

[0092] ;in, is the wall thickness at node j, is the first The wall thickness at each node is For the The basis function of the nodes (the linear Lagrangian basis function is used), is the basis function At the node The gradient at (calculated by numerical integration), For the The weight coefficient of each node, For Node The total number of nodes in the neighborhood (the neighborhood obtained by the predefined neighborhood radius);

[0093] ;in, For Node and The distance To affect the radius parameter (when calculating the wall thickness gradient at a node, it is necessary to consider the wall thickness values ​​of other nodes in the neighborhood of the node, that is, to define the radius range of this neighborhood); then The average thickness of the grid cells ;

[0094] Based on the average thickness of each grid cell, n grid cells are divided into n1 new grid cells; specifically, the grid cells are obtained The neighborhood unit set , the neighborhood unit set Contains grid cells All adjacent grid cells that share a node or edge are recorded as neighborhood cells;

[0095] Computational Grid Cells The maximum thickness difference with its neighboring cells ;in, For grid cells The average thickness of For grid cells Neighborhood unit The average thickness of

[0096] Preset thickness difference threshold range [t_min,t_max] ;like In [t_min,t_max] If the grid cell is The thickness of the area varies greatly, so the grid cells need to be The average is refined into two grid cells at a time; if Greater than , then the grid cell is considered The thickness of the area varies too much, and the grid cells need to be The average is refined into four grid cells at a time;

[0097] The original grid cells are combined with the grid cells obtained by average refinement to obtain n1 new grid cells, which are recorded as n1 subdivided grid cells.

[0098] Select M2 subdivided grid cells from n1 subdivided grid cells as seed cells, and build a priority queue for each seed cell to determine its growth order; the elements in the priority queue are the neighboring cells of the seed cell; usually a similarity metric (such as thickness difference, geometric distance, etc.) is used as the basis for priority, and the higher the similarity, the higher the priority to join the growth area;

[0099] Define the growth region, for each seed unit, add neighboring units to the growth region in sequence according to the order in its priority queue until a certain stop condition is met (such as the number of units in the region reaches a preset value, the similarity is lower than a threshold, etc.); obtain M2 regional grids; reconstruct the topological relationship based on the M2 regional grids, and finally obtain M partitions;

[0100] Define the thickness value for each partition to obtain a refined geometric model;

[0101] Ways to define thickness values ​​include:

[0102] Define the thickness distribution function ; is the three-dimensional coordinate of the node on the three-dimensional geometric model. For each grid unit in each partition, the corresponding thickness value is obtained in the corresponding thickness distribution function according to its centroid coordinate, thus completing the definition of the thickness value.

[0103] Thickness distribution function ;in, is a constant coefficient, is the characteristic size of the container, is the elastic modulus of the material, is the section moment of inertia, a function of the wall thickness, is the distributed load, is the bending moment load;

[0104] It should be noted that the characteristic size of a container refers to the maximum value of the length, width or height of the container; the elastic modulus of a material indicates the proportional relationship between stress and strain during elastic deformation of the material; different materials (such as steel, aluminum alloy, etc.) have different elastic modulus values; the moment of inertia of the section is a mechanical property parameter that describes the geometric shape of the section. For a container, the moment of inertia of the section is proportional to the cube of the height of the section; the larger the moment of inertia of the section, the higher the bending stiffness of the section; the moment of inertia of the section is a function of the wall thickness, because the wall thickness determines the geometric shape of the section;

[0105] Distributed load refers to the load per unit length / area along the length, width and height of the container; moment load refers to the moment load acting on the container; the moment load will cause the container to bend and deform;

[0106] The refined geometric model is divided into shell elements (the entire structural model is discretized into multiple shell elements in the form of shell elements) to generate a finite element mesh model (containing several shell elements); based on the finite element mesh model, the instrument's deadweight load data is applied to the corresponding instrument installation position, and the finite element mesh model is given the container's deadweight load data (which can be achieved by defining gravity acceleration); the instrument's inertial load data is converted into corresponding acceleration or force and applied to the instrument installation position; the instrument's vibration load data is converted into vibration excitation and applied to the corresponding instrument installation position; the instrument's impact load data is converted into impact force or acceleration time history and applied to the corresponding instrument installation position, thus completing the establishment of the container's finite element model.

[0107] Furthermore, the unit stress field and deformation amplitude are obtained by:

[0108] For each shell element , based on the element shape function and material properties, the corresponding element stiffness matrix is ​​calculated ; Assemble the unit stiffness matrices of all shell elements to obtain the total stiffness matrix of the entire container finite element model ; Element stiffness matrix The displacement strain function Integrate to obtain; ,in, , is the elastic matrix; for The transpose of is the derivative of the shape function (the function of the polynomial interpolation of the shell element), is the coordinate Jacobian matrix;

[0109] For each shell element , calculate the corresponding unit mass matrix And assembled into the total mass matrix of the entire container finite element model ;

[0110] Specifically, according to the shape function of the shell element, the mass matrix of the shell element is obtained by integrating the material density and the volume of the shell element; finally, the mass matrix of the shell element can be obtained by superimposing and summing the mass matrices of all shell elements.

[0111] Based on the total mass matrix and nodal loads (loads applied to the nodes of the finite element model), the total load matrix is ​​constructed ;

[0112] Solving Linear Equations , and obtain the node displacement matrix ;The nodal displacement matrix is ​​the matrix composed of the nodal displacements of the shell elements;

[0113] For each shell element , according to the unit shape function (also a function of the polynomial interpolation for shell elements) and the nodal displacement matrix , the corresponding shell element displacement field is calculated , for the shell element displacement field Perform differentiation operation to obtain the corresponding shell element strain field ; then the shell element The corresponding element stress field ;

[0114] The deformation amplitude is the absolute value of the nodal displacement of the shell element in the nodal displacement matrix.

[0115] Furthermore, the failure mode can be determined by:

[0116] Based on the element stress field, each shell element is calculated The equivalent stress ;

[0117] s v _e = [ ( s x - s y) 2 + ( s y - s z) 2 + ( s z - s x) 2 +6( t xyz 2 + t yz 2 + t zx 2 )] 1 2 ;in, , and are the components of the normal stress of the shell element in the three-dimensional directions, , and They are the components of the shear stress of the shell element in the three-dimensional direction (both obtained based on the element stress field);

[0118] Preset equivalent stress threshold ; For each shell element ,like Greater than , then the shell element Add stress concentration area element set ;

[0119] For stress concentration area element sets Each shell element in , calculate the yield margin ;

[0120] ;in, is the characteristic value of the material yield strength of the shell element, is the yield strength uncertainty correction factor, usually taken as , is the material yield criterion index, usually ranging from 1.5 to 2.0;

[0121] like , then define the shell element The failure mode is yielding;

[0122] For stress concentration area element sets Each shell element in , calculate the fracture margin ;

[0123] ;in, is the uncertainty correction factor of ultimate strength, usually less than 1; is the strain triaxiality correction factor, is the material fracture criterion index (same numerical range as the material yield criterion index); is the characteristic value of the material ultimate strength of the shell element;

[0124] Strain triaxiality correction factor ;in, is the equivalent Poisson's ratio; if , then define the shell element The failure mode is fracture;

[0125] Preset deformation threshold ; For all shell elements ,like Greater than , then the shell element Add deformation unit set ;

[0126] Deform the unit set Divide into K1 grid blocks, and for each grid block Perform eigenvalue analysis and calculate the block stiffness matrix KP;

[0127] Specifically, an initial vector is selected, and a triple diagonal matrix is ​​constructed through matrix-vector product, all eigenvalues ​​and eigenvectors of the triple diagonal matrix are solved, and the eigenvalues ​​of the original matrix are approximated using the eigenvectors;

[0128] Solving for the eigenvalues ​​of KP ;like v is less than 0, the grid block Buckling occurs; if the shell element If the number of buckling blocks in the shell element exceeds the preset buckling threshold, the shell element The failure mode is buckling;

[0129] Get the SN curve (stress-cycle number curve) of the material; for each shell element ; According to the stress-strain cycle amplitude and SN curve, the fatigue life cycle number is calculated Specifically, the periodic component and amplitude of the stress-strain cycle amplitude are extracted by rain flow counting and other methods, and the amplitude is substituted into the SN curve to estimate the corresponding number of fatigue life cycles.

[0130] The stress-strain cycle amplitude is obtained by calculating the stress / strain time history response of the unit under the load history according to the finite element analysis, and extracting the periodic component from the response time history by using the fractional counting method or the rain flow counting method, and calculating the stress-strain cycle amplitude;

[0131] like Less than the preset life cycle number , then the shell element It belongs to the fatigue crack initiation danger zone; all Less than Shell elements, add fatigue crack initiation set PUY;

[0132] For each shell element in PUY , a crack extension model is established, and the expression of the crack extension model is: ;in, is the crack size, is the number of cycles (indicates the number of cycles the structure undergoes under cyclic load), and is the material constant ( It reflects the intrinsic crack growth rate of the material under specific conditions. Reflects the material sensitivity of is the stress intensity factor range; It indicates the increment of crack size per unit number of cycles;

[0133] based on The calculation method (such as finite element, boundary element, etc.) of the crack size Perform cycle expansion analysis when Reaching the preset critical size When , it is judged as failure, and the failure threshold is preset. If the number of cycles when it is judged as failure is less than the failure threshold; then the corresponding shell element The failure mode is fatigue crack;

[0134] All the failure modes are summarized to obtain the failure mode of the container finite element model.

[0135] Furthermore, the calculation method of the reliability index includes:

[0136] For each failure mode identified in the container finite element model ; Establish the corresponding limit state equation ;in, Failure Mode The structural resistance of Failure Mode The structural effect of is the basic random variable vector (including random variables such as load, material properties, geometric dimensions, etc.);

[0137] For each elementary random variable , determine its statistical distribution type (such as normal distribution, lognormal distribution, etc.), and calculate its statistical distribution parameters (such as mean, standard deviation, etc.);

[0138] For each failure mode The limit state equation , according to the statistical distribution parameters of the basic random variable X, calculate The corresponding mean and standard deviation ;

[0139] Failure Mode Corresponding reliability index β_ s= [ m g _s- β' × s g _ s] [ s g _ s × (1+ I will )] ;in, is the reliability index correction coefficient, usually 0.1-0.2, is the uncertainty correction coefficient of the reliability index, usually 0.1-0.3; The larger it is, the smaller the probability of the corresponding failure mode occurring and the higher the reliability.

[0140] Furthermore, the failure probability can be obtained by:

[0141] Failure Mode Corresponding reliability index Standardization (linear transformation obeys standard normal distribution) to obtain standard normal distribution variables ; Calculate the standard normal distribution variable The corresponding probability value ; Probability value Failure Mode The corresponding failure probability.

[0142] This embodiment comprehensively, accurately and reasonably analyzes the structural safety and reliability of the container mobile laboratory; by establishing an accurate finite element model, static and dynamic loads are fully considered, and the analysis accuracy is greatly improved by accurately simulating the changes in container wall thickness, especially in stress concentration areas; and a variety of failure modes are integrated to comprehensively evaluate the potential failure risks of the container; by introducing a reliability index calculation method based on the limit state equation, the uncertainty of multiple parameters is considered to make the analysis results more in line with the actual situation; at the same time, the analysis results can be obtained quickly, which significantly improves the analysis efficiency; in addition, factors such as the spatial distribution of material properties, stress concentration effects and fatigue crack propagation are taken into account, which further improves the comprehensiveness and accuracy of the analysis; overall, the design quality, safety in use and reliability of the container mobile laboratory are improved.

[0143] Example 2

[0144] See also Figure 2 As shown, the part not described in detail in this embodiment is described in Example 1, which provides a container mobile laboratory structural mechanics reliability analysis system, including:

[0145] A model building module, used for acquiring container load data and container basic data, and building a container finite element model based on the container load data and container basic data;

[0146] The stress-deformation fitting module obtains the unit stress field and deformation amplitude of the container based on the container finite element model;

[0147] The indicator output module determines the failure mode of the container finite element model based on the unit stress field and deformation amplitude, and calculates the reliability indicator of the failure mode;

[0148] The failure judgment module calculates the failure probability of the failure mode based on the failure mode and its corresponding reliability index, and sends it to the reliability analysis terminal; each module is connected by wired and / or wireless means to realize data transmission between modules.

[0149] Example 3

[0150] This embodiment discloses an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the operation mode of the structural mechanics reliability analysis method of a container mobile laboratory provided above is implemented.

[0151] Since the electronic device introduced in this embodiment is an electronic device used to implement a container mobile laboratory structural mechanics reliability analysis method in the embodiment of this application, based on the container mobile laboratory structural mechanics reliability analysis method introduced in the embodiment of this application, the technical personnel of this field can understand the specific implementation of the electronic device of this embodiment and its various variations, so how the electronic device implements the method in the embodiment of this application is not introduced in detail here. As long as the technical personnel of this field implement the electronic device used in the container mobile laboratory structural mechanics reliability analysis method in the embodiment of this application, it belongs to the scope of protection of this application.

[0152] The above formulas are all dimensionless and numerical calculations. The formula is a formula for the most recent real situation obtained by collecting a large amount of data and performing software simulation. The preset parameters and thresholds in the formula are set by technicians in this field according to actual conditions.

[0153] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technical users in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A structural mechanics reliability analysis method for a container mobile laboratory, characterized in that: include: S1. Obtain container load data and container basic data, and establish a container finite element model based on the container load data and container basic data; S2. Based on the container finite element model, obtain the unit stress field and deformation amplitude of the container; S3. Based on the unit stress field and deformation amplitude, determine the failure mode of the container finite element model and calculate the reliability index of the failure mode; S4. Based on the failure mode and its corresponding reliability index, the failure probability of the failure mode is calculated and sent to the reliability analysis terminal; The method of establishing the container finite element model includes: According to the geometric dimensions of the container, a three-dimensional geometric model of the container is established; and based on the wall thickness of the container, the three-dimensional geometric model is refined to obtain a refined geometric model; According to the material type, the geometric model will be refined to define the corresponding material properties, including elastic modulus, Poisson's ratio and density; Divide the refined geometric model into shell elements to generate a finite element mesh model; apply the instrument deadweight load data to the corresponding instrument installation position based on the finite element mesh model, and give the container deadweight load data to the finite element mesh model; convert the instrument inertial load data into the corresponding acceleration or force and apply it to the instrument installation position; convert the instrument vibration load data into vibration excitation and apply it to the corresponding instrument installation position; convert the instrument impact load data into impact force or acceleration time history and apply it to the corresponding instrument installation position, thus completing the establishment of the container finite element model; The method of refining the three-dimensional geometric model includes: The three-dimensional geometric model is initially divided into n grid units, and the average thickness of each grid unit is calculated; based on the average thickness of each grid unit, the n grid units are divided into n1 new grid units; recorded as n1 subdivided grid units; Select M2 subdivided grid cells from n1 subdivided grid cells as seed cells, and build a priority queue for each seed cell; the elements in the priority queue are the neighboring cells of the seed cell; Define the growth region, and for each seed unit, add neighboring units to the growth region in sequence according to the order in its priority queue until the stop condition is met; obtain M2 regional grids; reconstruct the topological relationship based on the M2 regional grids, and finally obtain M partitions; define the thickness value of each partition, that is, obtain a refined geometric model; The method of defining the thickness value includes: Define the thickness distribution function f(x, y, z); (x, y, z) is the three-dimensional coordinate of the node on the three-dimensional geometric model. For each grid unit in each partition, the corresponding thickness value is obtained in the corresponding thickness distribution function according to its centroid coordinate, thus completing the definition of the thickness value. Thickness distribution function Where C1 is a constant coefficient, LR is the characteristic size of the container, E is the elastic modulus of the material, I(x,y,z) is the section inertia moment, q(x,y,z) is the distributed load, and ML(x,y,z) is the bending moment load; The method of calculating the average thickness of each grid unit includes: Define N nodes on the 3D geometric model on average. For each node j, calculate the normal vector change rate v_j,k=1-|nj·nk| between it and the adjacent node k, where nj is the normal vector of node j, nk is the normal vector of node k, and a change rate threshold is preset; when the normal vector change rate v_j,k is greater than the change rate threshold, it is defined that node j is located in the corner area; For the node j defined as being in the corner region, a thickness weight w_j is assigned to it; for the node not in the corner region, a thickness weight of 1 is assigned to it; in, is the wall thickness gradient value at node j, β and α are the magnification coefficients, and v_j is the proportion of the grid unit volume occupied by node j; in, is the volume fraction associated with node j, V_i is the total volume of the i-th grid cell, Vavg is the average volume of the grid cell, and γ is the regularization parameter; Ways to obtain include: Find all grid cells containing node j. For each grid cell containing node j, construct a new small polyhedron so that node j is a vertex of the small polyhedron. Calculate the sum of the volumes of all constructed small polyhedrons as Among them, t_j is the wall thickness at node j, t_k is the wall thickness at the kth node in the neighborhood of node j, φk is the basis function of the kth node, is the gradient of the basis function φk at node j, W_k is the weight coefficient of the kth node, and N1 is the total number of nodes in the neighborhood of node j; Among them, r_k,j is the distance between nodes k and j, σ is the influence radius parameter; then the average thickness of the i-th grid unit The method of dividing n grid units into n1 new grid units includes: Obtain a neighborhood unit set N(K) of the grid unit K. The neighborhood unit set N(K) includes all adjacent grid units that share nodes or edges with the grid unit K and are recorded as neighborhood units. Calculate the maximum thickness difference Δt_K=max(|t_K-t_L|) between the grid cell K and its neighboring cells; where t_K is the average thickness of the grid cell K, and t_L is the average thickness of the neighboring cells L of the grid cell K; The thickness difference threshold interval [t_min, t_max] is preset; if Δt_K is within [t_min, t_max], the grid unit K is refined into two grid units at one time on average; if Δt_K is greater than t_max, the grid unit K is refined into four grid units at one time on average; The original grid cells are combined with the grid cells obtained by average refinement to obtain n1 new grid cells.

2. The structural mechanics reliability analysis method of container mobile laboratory according to claim 1 is characterized in that: The container load data includes static load and dynamic load; the container basic data includes geometric dimensions and material attribute data of the container; the geometric dimensions include length, width and height; the material attribute data includes wall thickness and material type; Static loads include instrument deadweight load data and container deadweight load data; dynamic loads include instrument inertia load data, instrument vibration load data, and instrument impact load data.

3. The structural mechanics reliability analysis method of container mobile laboratory according to claim 2 is characterized in that: The method for obtaining the unit stress field and deformation amplitude includes: For each shell element e, the corresponding element stiffness matrix k_e is calculated based on the element shape function and material properties; the element stiffness matrices of all shell elements are assembled to obtain the total stiffness matrix KL of the entire container finite element model; the element stiffness matrix k_e is obtained by integrating the displacement strain function FG; FG = Bx T′ ·DL·Bx, where Bx = B·J (-1) , DL is the elastic matrix; Bx T′ is the transpose of Bx, B is the derivative of the shape function, and J is the coordinate Jacobian matrix; For each shell element e, the corresponding element mass matrix m_e is calculated and assembled into the total mass matrix MG of the entire container finite element model; based on the total mass matrix MG and the node loads, the total load matrix FL is constructed; Solve the linear equation KL·U=FL to obtain the nodal displacement matrix U; for each shell element e, calculate the corresponding shell element displacement field u_e=NL·U according to the element shape function NL and the nodal displacement matrix U, and perform differentiation operation on the shell element displacement field u_e to obtain the corresponding shell element strain field ε_e; then the element stress field σ_e=DL·ε_e corresponding to the shell element e; the deformation amplitude is the absolute value of the nodal displacement of the shell element in the nodal displacement matrix.

4. The structural mechanics reliability analysis method of container mobile laboratory according to claim 3 is characterized in that: The failure mode is determined by: Based on the unit stress field, calculate the equivalent stress σv_e of each shell element e; Among them, σx, σy and σz are the components of the normal stress of the shell element in the three-dimensional direction, τxy, τyz and τzx are the components of the shear stress of the shell element in the three-dimensional direction; The equivalent stress threshold σth is preset; for each shell element e, if σv_e is greater than σth, the shell element e is added to the stress concentration area element set SL; For each shell element e in the stress concentration area element set SL, calculate the yield margin σy_e; Among them, σys is the characteristic value of the material yield strength of the shell element, kf is the yield strength uncertainty correction factor, and mk is the material yield criterion index; If σy_e<0, the shell element e is defined as the failure mode of yielding; For each shell element e in the stress concentration area element set SL, calculate the fracture margin δu_e; Among them, kj is the uncertainty correction coefficient of ultimate strength; εn is the strain triaxiality correction coefficient, mj is the material fracture criterion index; uts is the characteristic value of the material ultimate strength of the shell element; Strain triaxiality correction factor Where, vr is the equivalent Poisson's ratio; if δu_e<0, the shell element e is defined as the failure mode of fracture; Preset deformation threshold δth; for all shell elements e, if σv_e is greater than δth, then add the shell element e to the deformation element set UD; Divide the deformable unit set UD to obtain K1 grid blocks, perform eigenvalue analysis on each grid block v, and obtain the block stiffness matrix KP; solve the eigenvalue γ_v of KP; If γ_v is less than 0, the grid block v buckles; if the number of buckled grid blocks in the shell element e is greater than the preset buckling threshold, the shell element e is in the buckling failure mode; Obtain the SN curve of the material; for each shell element e; calculate the number of fatigue life cycles Nf_e according to the stress-strain cycle amplitude and the SN curve; If all shell elements whose Nf_e is less than the preset number of life cycles Nd are added to the fatigue crack initiation set PUY; For each shell element e in PUY, a crack extension model is established, and the expression of the crack extension model is: Where a1 is the crack size, N4 is the number of cycles, C′ and m′ are material constants, and ΔK is the range of stress intensity factors; It indicates the increment of crack size per unit number of cycles; Based on the calculation method of ΔK, the crack size a1 is analyzed for periodic expansion. When a1 reaches the preset critical size ac, the corresponding shell element e is judged to be failed. The failure threshold is preset. If the number of cycles when it is judged to be failed is less than the failure threshold, the corresponding shell element e is in the failure mode of fatigue crack. All the failure modes are summarized to obtain the failure mode of the container finite element model.

5. The structural mechanics reliability analysis method of container mobile laboratory according to claim 4 is characterized in that: The calculation method of the reliability index includes: For each failure mode s, the corresponding limit state equation g_s(X)=RA_s-SA_s is established; where RA_s is the structural resistance of failure mode s, SA_s is the structural effect of failure mode s; X is the basic random variable vector; For each basic random variable X, determine its statistical distribution type and calculate its statistical distribution parameters; For each limit state equation g_s(X) of failure mode s, calculate the mean μg_s and standard deviation σg_s corresponding to g_s(X) according to the statistical distribution parameters of the basic random variable X; Then the reliability index corresponding to failure mode s is Among them, β′ is the reliability index correction coefficient, and θ′ is the reliability index uncertainty correction coefficient.

6. The structural mechanics reliability analysis method of container mobile laboratory according to claim 5 is characterized in that: The method for obtaining the failure probability includes: Standardize the reliability index β_s corresponding to the failure mode s to obtain the standard normal distribution variable β′_s; calculate the probability value corresponding to the standard normal distribution variable β′_s The probability value PF_s is the failure probability corresponding to failure mode s.

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