CN-121997665-A - Method for identifying aluminum bar welding failure in EOL expansion stage of battery pack

CN121997665ACN 121997665 ACN121997665 ACN 121997665ACN-121997665-A

Abstract

The invention relates to an aluminum bar welding failure recognition method in an EOL expansion stage of a battery pack, which comprises the steps of obtaining actual measurement data of aluminum bar welding tension through a horizontal drawing test, taking the minimum tension as a failure judgment threshold value, obtaining a module three-dimensional model and a welding track file, establishing a finite element model through geometric preprocessing and differential grid division, endowing an aluminum bar with material properties of a stress-strain curve, establishing Tie binding connection, applying end plate constraint and EOL equivalent expansion force load through explicit dynamic analysis, extracting section tension of an aluminum bar welding area after simulation, comparing the section tension with the threshold value, and judging failure risk, and positioning failure causes and giving an optimization direction based on tension discreteness. The invention realizes quantitative identification of welding failure risk, gives consideration to simulation precision and efficiency, can pre-judge risk in advance, shortens research and development period, and provides technical support for battery pack safety.

Inventors

MAO KAI
He Mengda
XIONG XIAOPENG

Assignees

孝感楚能新能源创新科技有限公司

Dates

Publication Date: 20260508
Application Date: 20260128

Claims (10)

1. The method for identifying the aluminum bar welding failure in the EOL expansion stage of the battery pack is characterized by comprising the following steps of: obtaining measured data of the aluminum bar welding tension, and determining a failure judgment threshold value of the aluminum bar welding tension based on the measured data; Acquiring a three-dimensional data model of a battery pack, performing geometric pretreatment and grid division on the three-dimensional data model of the battery pack, and establishing a finite element model of the battery pack; corresponding material properties are given to each part of the battery pack finite element model, and a binding connection relation between an aluminum bar welding area and the battery core electrode column is established according to an actual welding track of the aluminum bar; Importing the finite element model of the battery pack into simulation software, setting an analysis step, applying load setting and boundary conditions for simulating the expansion of the battery cell to an EOL state in the analysis step, and submitting simulation calculation; After simulation calculation is completed, the section tension of each aluminum bar welding area in the finite element model is extracted and compared with the failure judgment threshold value, and if the section tension of any aluminum bar welding area exceeds the failure judgment threshold value, the risk of welding failure of the aluminum bar is judged.
2. The method for identifying aluminum bar welding failure at the EOL expansion stage of a battery pack according to claim 1, wherein the method further comprises analyzing the cause of the aluminum bar welding failure based on the measured data of the aluminum bar welding tension of the sample, specifically comprising the following steps: if the difference value between the maximum welding tension and the minimum welding tension in the measured data of the aluminum bar welding tension of the sample is larger than a preset first threshold value, judging that the welding failure is caused by unstable welding process, and improving the welding process in the direction of optimizing the welding process; If the difference value between the maximum welding tension and the minimum welding tension in the measured data of the aluminum bar welding tension of the sample is smaller than or equal to a preset first threshold value, judging that the welding failure is due to the aluminum bar structural design, and improving the aluminum bar structural optimization.
3. The method for identifying the failure of the aluminum bar welding in the EOL expansion stage of the battery pack is characterized in that the measured data of the welding tension of the aluminum bar are obtained by selecting a battery cell and an aluminum bar sample from a batch to be evaluated, performing a horizontal drawing force test on the welded sample, and when the welding point between the aluminum bar and the battery cell terminal is pulled to be failed, recording the maximum tension value, namely the measured data of the welding tension of a single sample, selecting the minimum value from the measured data to be determined as the failure judgment threshold value, wherein the welding parameters are set to be 0.5-2.0mm of welding penetration and 2.0-4.0mm of welding fusion width.
4. The method for identifying aluminum bar welding failure in EOL expansion stage of battery pack according to claim 1, wherein the steps of obtaining a three-dimensional data model of the battery pack, performing geometric preprocessing and grid division on the three-dimensional data model of the battery pack, and establishing a finite element model of the battery pack comprise the following steps: acquiring a battery pack three-dimensional data model comprising 3D digital-analog information of a battery cell, aluminum bars, foam cells between the battery cells and end plates at two sides, and importing the battery pack three-dimensional data model into finite element software; acquiring actual welding track parameters of the aluminum bar, and performing intervention refinement on the geometry of the aluminum bar in simulation software according to the actual welding track parameters of the aluminum bar to create a geometrical surface on which the welding overlap of the aluminum bar and the battery cell pole is generated; the method comprises the steps of dividing a battery cell and an aluminum bar into different grid sizes, wherein the grid size of the aluminum bar is smaller than that of the battery cell, the aluminum bar is divided into multiple layers of solid grids along the thickness direction, and a welding area and a base material area of the aluminum bar are divided into different assemblies.
5. The method for identifying aluminum bar welding failure in EOL expansion stage of battery pack according to claim 4, wherein the battery cells and the aluminum bars are divided into different grid sizes, wherein the grid size of the aluminum bars is smaller than that of the battery cells, the aluminum bars are divided into multiple layers of solid grids along the thickness direction, and the welding area and the base material area of the aluminum bars are divided into different components, specifically comprising the following steps: The overall basic grid size is 5mm, the grid of the battery cell is divided into 10mm, and the grid of the aluminum bar is thinned into 3mm; In the unit type, the cell shell is modeled by adopting a shell unit, the cell cover plate is modeled by adopting a hexahedral solid unit, the cell cover plate and the peripheral grid of the cell shell are processed in a joint mode, the whole aluminum bar is divided by adopting the hexahedral solid unit and is divided into three layers of grids along the thickness direction of the aluminum bar, and a welding area and a base material area of the aluminum bar are divided into different assemblies.
6. The method for identifying aluminum bar welding failure in an EOL expansion stage of a battery pack according to claim 4, wherein the step of assigning corresponding material properties to each part of the finite element model of the battery pack and establishing a binding connection relationship between an aluminum bar welding area and a cell terminal according to an actual welding track of the aluminum bar comprises the steps of: Creating an aluminum bar material card in simulation software, inputting the density, the elastic modulus and the poisson ratio of aluminum bar, selecting plastic options and inputting a stress-strain curve to finish the attribute giving of the section of the aluminum bar material; Creating a master surface and a slave surface according to the actual welding track of the aluminum bar, and selecting the contact surface of the electrode column or the cover plate of the battery cell and the welding of the aluminum bar as a main surface, wherein the geometric surface of the welding overlap of the aluminum bar and the electrode column of the battery cell is a slave surface; Binding the aluminum bar welding area with the battery core pole by a Tie binding command, and simulating the welding relationship of the aluminum bar welding area and the battery core pole.
7. The method for identifying aluminum bar welding failure in EOL expansion phase of battery pack according to claim 1, wherein the step of importing the finite element model of the battery pack into simulation software and performing analysis step setting, applying load setting and boundary conditions for simulating the expansion of the battery cell to EOL state in the analysis step, submitting simulation calculation, and comprising: Creating an explicit dynamics analysis step for the finite element model in simulation software, simulating large deformation and complex contact behaviors in the process of expanding the battery cell, activating a node force output option in field output request setting of the analysis step, and recording node force data for subsequently extracting welding tension; In the analysis step, six degrees of freedom of fixed connection parts of end plates at two sides of the constraint module simulate the actual fixed installation state of the battery module in the battery pack; And in the analysis step, a temperature rise load simulating the expansion of the battery cell to a life end state is applied to a coil core node set in the battery cell, and after the setting is completed, the finite element model is submitted to calculate until the simulation reaches the set life end expansion state of the battery cell.
8. An aluminum bar welding failure recognition system for an EOL expansion stage of a battery pack, comprising: The failure judgment threshold generation module is used for acquiring actual measurement data of the aluminum bar welding tension and determining a failure judgment threshold of the aluminum bar welding tension based on the actual measurement data; the finite element model construction module is used for acquiring a battery pack three-dimensional data model, performing geometric pretreatment and grid division on the battery pack three-dimensional data model, and establishing a battery pack finite element model; The material and connection relation giving module is used for giving corresponding material properties to each part of the battery pack finite element model and establishing a binding connection relation between an aluminum bar welding area and the battery core electrode column according to an actual welding track of the aluminum bar; The simulation analysis module is used for importing the finite element model of the battery pack into simulation software and setting an analysis step, applying load setting and boundary conditions for simulating the expansion of the battery cell to an EOL state in the analysis step, and submitting simulation calculation; And the risk identification module is used for extracting the section tension of each aluminum bar welding area in the finite element model after the simulation calculation is completed, comparing the section tension with the failure judgment threshold value, and judging that the welding failure risk exists in the aluminum bar if the section tension of any aluminum bar welding area exceeds the failure judgment threshold value.
9. A computer storage medium storing a computer program which, when executed by a processor, implements the steps of the battery pack EOL expansion stage aluminium bar welding failure identification method of any one of claims 1-7.
10. An electronic device comprising a memory for storing computer executable instructions and a processor for executing the computer executable instructions, which when executed by the processor, perform the steps of the battery pack EOL expansion phase aluminum bar weld failure identification method of any of claims 1-7.

Description

Method for identifying aluminum bar welding failure in EOL expansion stage of battery pack Technical Field The invention relates to the technical field of batteries, in particular to a method for identifying aluminum bar welding failure in an EOL expansion stage of a battery pack. Background With the rapid development of the electrochemical energy storage industry, the safety and durability of a high-capacity energy storage battery pack are important points for core research and development. In the long-term charge-discharge cycle of the lithium ion battery, continuous expansion force is generated due to the growth of an SEI film, the internal gas production and the volume change of an active material, the expansion force is gradually increased along with the attenuation of the health state of the battery, the expansion force reaches a peak value at the end of a life cycle (EOL), and the expansion force of the energy storage battery core at the EOL stage can reach 20000N-50000N. The aluminum bar is used as a key component for electric energy transmission and structural connection between the electric cores, and the welding part of the aluminum bar and the electric core polar column is easy to fail under the effect of EOL peak expansion force, so that serious safety accidents such as out-of-control battery Bao Re, fire explosion and the like are caused. Therefore, a technical solution for accurately identifying the risk of aluminum bar welding failure in the EOL expansion stage is needed, and support is provided for aluminum bar structural design and welding process optimization. In the prior art, related researches on the expansion force of a battery module are mainly focused on structural member strength test and general expansion simulation, and obvious limitations exist in that most expansion force simulation methods are used for simulating the stress strain state of a module fixing member such as an end plate, a bolt, a binding belt and the like by calculating the stress of the end plate or applying the expansion coefficient, and not paying attention to a core failure risk point of aluminum bar welding, for example, the invention application with the publication number of CN117330407A discloses a battery module structural member expansion force resistance test method, a failure judgment method and a device, which attempt to improve simulation precision in a mode of applying resistance force and expansion thrust step by step, but a test object is focused on a module fixing member and not related to a welding area of aluminum bars and polar posts among electric cores, failure judgment basis is a macroscopic parameter such as the stress strain state, the length change quantity of the structural member, and the like, a special judgment standard for a welding part is not established, and the scheme is used for applying resistance force and expansion force by theoretical calculation, and not combining measured welding tension data to calibrate a simulation model, so that the recognition precision of the welding failure risk is insufficient, and a definite direction cannot be provided for optimizing an aluminum bar welding process. Disclosure of Invention In order to solve the defects of the prior art, the application aims to provide an aluminum bar welding failure recognition method in an EOL expansion stage of a battery pack, which comprises the steps of firstly obtaining actual welding tension data of an aluminum bar through a horizontal drawing test, taking the minimum welding tension as a failure judgment standard to ensure judgment according to the actual bonding engineering, then carrying out grid refinement treatment on an aluminum bar welding area through finite element software, accurately building a Tie binding relation of a welding part, and finally adopting dynamic explicit analysis to simulate the actual expansion force in the EOL stage, extracting the tension of the welding area and comparing with an actual measurement threshold value to realize the accurate recognition of failure risk. The application fills the blank in the field of aluminum bar welding failure recognition in the EOL expansion stage in the prior art, and provides high-efficiency and accurate technical support for the safety design of the battery pack. The scheme for solving the technical problems is as follows, the method for identifying the aluminum bar welding failure in the EOL expansion stage of the battery pack comprises the following steps: obtaining measured data of the aluminum bar welding tension, and determining a failure judgment threshold value of the aluminum bar welding tension based on the measured data; Acquiring a three-dimensional data model of a battery pack, performing geometric pretreatment and grid division on the three-dimensional data model of the battery pack, and establishing a finite element model of the battery pack; corresponding material properties are given to each part of the battery pack finite