Weld joint reliability evaluation method and device and computer equipment

Abstract

According to the welding seam reliability evaluation method and device and the computer equipment provided by the invention, when the welding seam reliability of the target lithium battery is evaluated, the static fatigue strength and the dynamic fatigue strength of the target lithium battery are determined according to the expansive force data of the target lithium battery and the area of the battery shell; dynamic and static fatigue damage of the battery in the target service cycle is predicted in advance; for example, the static fatigue strength and the target service cycle are predicted through the static fatigue damage model to obtain the reduction amount of the blasting strength, and the dynamic fatigue strength, the target service cycle and the initial blasting strength are predicted through the dynamic residual strength model to obtain the dynamic residual blasting strength. Therefore, the method can determine the final residual bursting strength of the target lithium battery after the target service period through the dynamic and static fatigue damage predicted by the two models, and then carries out reliability evaluation on the battery welding seam, so that the accuracy of an evaluation result can be remarkably improved.

Description

Technical Field

[0001] The present application relates to the field of lithium battery technology, and in particular to a weld reliability assessment method, device and computer equipment. Background Art

[0002] In the structure and operation mechanism of lithium batteries, the weld is a key part connecting the outer shell and the cover plate, and its reliability is directly related to the overall performance and safety of the battery. During the charge and discharge cycle of lithium batteries, the pole piece inside the winding core will undergo periodic changes of thickening and recovery, causing the outer shell, especially the surface parallel to the pole piece, to swell and recover repeatedly, and then produce dynamic mechanical fatigue damage at the weld position. At the same time, during the long-term storage and shelving of the battery, side reactions will still occur inside the battery. The occurrence of side reactions will produce gas, which will increase the internal air pressure of the battery and exert a certain pulling force on the weld. At the same time, the stable shape of the pole piece will also exert a continuous static resistance force on the weld, causing static fatigue damage to the weld. Therefore, during the actual service process, the battery weld is affected by both dynamic damage and static damage.

[0003] Since the reliability of welds is directly related to whether the battery will experience electrolyte leakage, performance degradation, or even safety accidents, it is particularly important to conduct accurate and reliable evaluation of welds. Through the reliability evaluation of welds, the life performance of welds under different working conditions can be predicted, potential safety hazards can be discovered in time, and a scientific basis can be provided for battery design optimization. However, the current weld reliability evaluation lacks research on dynamic and static fatigue damage of lithium batteries, resulting in low accuracy of the evaluation results. Summary of the invention

[0004] The purpose of this application is to solve at least one of the above-mentioned technical defects, especially the technical defect that the weld reliability assessment in the prior art lacks exploration of dynamic and static fatigue damage of lithium batteries, resulting in low accuracy of the assessment results.

[0005] The present application provides a weld reliability assessment method, the method comprising:

[0006] Acquire a target lithium battery, and determine expansion force data, battery housing area, and initial burst strength of the target lithium battery, so as to determine static fatigue strength and dynamic fatigue strength of the target lithium battery within a target service cycle based on the expansion force data and the battery housing area;

[0007] Inputting the static fatigue strength and the target service cycle into a preset static fatigue damage model to obtain a burst strength reduction output by the static fatigue damage model;

[0008] Determine the fatigue ratio of the target lithium battery based on the target service cycle and the dynamic fatigue strength, and use a preset dynamic residual strength model to estimate the residual strength of the dynamic fatigue strength, the fatigue ratio and the initial burst strength to obtain the dynamic residual burst strength of the target lithium battery;

[0009] The final residual burst strength of the target lithium battery is determined according to the burst strength reduction and the dynamic residual burst strength, and the weld reliability of the target lithium battery is evaluated based on the final residual burst strength.

[0010] Optionally, the expansion force data includes full-charge expansion force, storage expansion force and full-discharge expansion force;

[0011] The determining the static fatigue strength and the dynamic fatigue strength of the target lithium battery within a target service cycle based on the expansion force data and the battery housing area includes:

[0012] Determine the preload force of the target lithium battery, and calculate the full charge expansion force, the storage expansion force, the preload force and the battery housing area using a static fatigue strength algorithm to obtain the static fatigue strength of the target lithium battery within a target service cycle;

[0013] The full charge expansion force, the full discharge expansion force and the battery housing area are calculated using a dynamic fatigue strength algorithm to obtain the dynamic fatigue strength of the target lithium battery within the target service cycle.

[0014] Optionally, the static fatigue strength algorithm includes:

[0015]

[0016] In the formula, Indicates static fatigue strength; Indicates full expansion force; Indicates the storage expansion force; Indicates preload; Indicates the battery casing area.

[0017] Optionally, the dynamic fatigue strength algorithm includes:

[0018]

[0019] In the formula, Indicates full expansion force; Indicates full expansion force; Indicates the battery casing area.

[0020] Optionally, the expression of the static fatigue damage model includes:

[0021]

[0022] In the formula, represents the burst strength reduction output by the static fatigue damage model; represents the ambient temperature; Pt represents the static fatigue strength, which characterizes the holding pressure; t represents the holding time of the target lithium battery within the target service cycle.

[0023] Optionally, determining the fatigue ratio of the target lithium battery based on the target service cycle and the dynamic fatigue strength includes:

[0024] Determine the weld fatigue life corresponding to the dynamic fatigue strength according to a preset SN curve, and determine the weld fatigue times of the target lithium battery according to the target service cycle;

[0025] The ratio of the weld fatigue times to the weld fatigue life is calculated to obtain the fatigue ratio of the target lithium battery.

[0026] Optionally, the expression of the dynamic residual strength model includes:

[0027]

[0028] In the formula, represents the dynamic residual blasting strength output by the dynamic residual strength model; Indicates the initial burst intensity; Indicates dynamic fatigue strength; Indicates the fatigue percentage.

[0029] Optionally, evaluating the weld reliability of the target lithium battery based on the final residual burst strength includes:

[0030] Determining whether the final residual blasting strength is greater than the static fatigue strength and the dynamic fatigue strength;

[0031] If yes, it is confirmed that the weld of the target lithium battery is reliable within the target service period;

[0032] If not, it is confirmed that the weld of the target lithium battery is unreliable within the target service cycle.

[0033] The present application also provides a weld reliability assessment device, comprising:

[0034] A fatigue strength determination module, used to obtain a target lithium battery, and determine the expansion force data, battery shell area and initial burst strength of the target lithium battery, so as to determine the static fatigue strength and dynamic fatigue strength of the target lithium battery within a target service cycle based on the expansion force data and the battery shell area;

[0035] A strength reduction prediction module, used for inputting the static fatigue strength and the target service cycle into a preset static fatigue damage model to obtain a burst strength reduction output by the static fatigue damage model;

[0036] A residual strength prediction module, used to determine the fatigue ratio of the target lithium battery based on the target service cycle and the dynamic fatigue strength, and to estimate the residual strength of the dynamic fatigue strength, the fatigue ratio and the initial burst strength using a preset dynamic residual strength model to obtain the dynamic residual burst strength of the target lithium battery;

[0037] A reliability evaluation module is used to determine the final residual burst strength of the target lithium battery according to the burst strength reduction and the dynamic residual burst strength, and to obtain the weld reliability of the target lithium battery based on the final residual burst strength evaluation.

[0038] The present application also provides a computer device, comprising: one or more processors, and a memory;

[0039] The memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the steps of the weld reliability assessment method described in any one of the above embodiments are performed.

[0040] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0041] The weld reliability assessment method, device and computer equipment provided in the present application can first determine the expansion force data, battery shell area and initial burst strength of the target lithium battery when conducting weld reliability assessment on the target lithium battery, so as to determine the static fatigue strength and dynamic fatigue strength of the target lithium battery according to the expansion force data and the battery shell area, as the basic data for dynamic and static fatigue strength damage prediction, and then the static fatigue strength and the target service cycle can be input into a preset static fatigue damage model to obtain the burst strength reduction output by the static fatigue damage model, so as to predict in advance the static fatigue damage of the target lithium battery weld within the target service cycle; at the same time, the present application can also determine the fatigue proportion of the target lithium battery based on the target service cycle and the dynamic fatigue strength, and use the preset dynamic residual strength model to estimate the residual strength of the dynamic fatigue strength, fatigue proportion and initial burst strength to obtain the dynamic residual burst strength, so as to achieve the early prediction of the dynamic fatigue damage of the target lithium battery weld within the target service cycle; finally, the final residual burst strength can be determined according to the burst strength reduction and the dynamic residual burst strength, and the weld reliability of the target lithium battery can be obtained based on the final residual burst strength assessment. Through this method, the present application can predict in advance the dynamic and static fatigue damage of the target lithium battery within the target service cycle through the static fatigue damage model and the dynamic residual strength model, and use it to perform reliability assessment on the battery welds, thereby significantly improving the accuracy of the assessment results. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0043] Figure 1 A schematic diagram of a process flow of a weld reliability assessment method provided in an embodiment of the present application;

[0044] Figure 2 A schematic diagram of a curve showing the change of expansion force during a cycle provided in an embodiment of the present application;

[0045] Figure 3 A schematic diagram of the relationship between battery expansion force and battery cycle number provided in an embodiment of the present application;

[0046] Figure 4 A schematic diagram of a curve showing the change in expansion force during a storage process provided in an embodiment of the present application;

[0047] Figure 5A schematic diagram of the relationship between ambient temperature and blasting strength provided in an embodiment of the present application;

[0048] Figure 6 A schematic diagram of the relationship between the pressure holding strength and the bursting strength provided in an embodiment of the present application;

[0049] Figure 7 A schematic diagram of the relationship between the pressure holding time and the burst strength provided in an embodiment of the present application;

[0050] Figure 8 A schematic diagram of the relationship between fatigue ratio and dynamic residual blasting strength provided in an embodiment of the present application;

[0051] Fig. 9 A schematic diagram of a curve showing the change in static fatigue strength of a battery during service provided in an embodiment of the present application;

[0052] Fig.10 A schematic diagram of a curve showing the change in dynamic fatigue strength of a battery during service provided in an embodiment of the present application;

[0053] Fig.11 A schematic diagram of the structure of an SN curve provided in an embodiment of the present application;

[0054] Fig.12 A schematic diagram of the structure of a weld reliability assessment device provided in an embodiment of the present application;

[0055] Fig.13 A schematic diagram of the internal structure of a computer device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0057] Since the reliability of welds is directly related to whether the battery will experience electrolyte leakage, performance degradation, or even safety accidents, it is particularly important to conduct accurate and reliable evaluation of welds. Through the reliability evaluation of welds, the life performance of welds under different working conditions can be predicted, potential safety hazards can be discovered in time, and a scientific basis can be provided for battery design optimization. However, the current weld reliability evaluation lacks research on dynamic and static fatigue damage of lithium batteries, resulting in low accuracy of the evaluation results.

[0058] Based on this, this application proposes the following technical solutions, see below for details:

[0059] In one embodiment, Figure 1 As shown, Figure 1 A schematic diagram of a process flow of a weld reliability assessment method provided in an embodiment of the present application; the present application provides a weld reliability assessment method, which specifically includes the following:

[0060] S110: Acquire a target lithium battery, and determine the expansion force data, battery shell area, and initial burst strength of the target lithium battery, so as to determine the static fatigue strength and dynamic fatigue strength of the target lithium battery within a target service cycle based on the expansion force data and the battery shell area.

[0061] In this step, when the computer equipment performs weld reliability assessment on the target lithium battery, it can first determine the expansion force data, battery shell area and initial burst strength of the target lithium battery, and then determine the static fatigue strength and dynamic fatigue strength of the target lithium battery within the target service cycle based on the expansion force data and battery shell area, and use them as basic data for dynamic and static fatigue strength damage prediction.

[0062] Among them, the expansion force data refers to the force generated by the volume expansion caused by the electrochemical reaction during the charging and discharging process of the lithium battery. The expansion force changes continuously with the different stages of the charging and discharging process. Therefore, the expansion force data can include the expansion force of different stages such as full charge expansion force, full discharge expansion force and storage expansion force. Specifically, the expansion force data can be the change data of the full charge expansion force, full discharge expansion force and storage expansion force during the service cycle, that is, the relationship curve with the service cycle as the independent variable and the full charge expansion force, full discharge expansion force and storage expansion force as the dependent variable, respectively, through which the relationship reflects the expansion force size in the battery shell. In addition, the battery shell area of ​​the present application refers to the area of ​​the lithium battery shell parallel to the larger side of the pole piece. For example, for a square shell lithium battery, the battery shell area can be the area of ​​the largest side of the shell; the initial burst strength refers to the tensile or shear strength of the weld when it is just produced, which is the basic indicator for evaluating the quality of the weld; and the target service cycle refers to the expected working time or number of charge and discharge cycles of the lithium battery in actual use. It should be noted that the method for obtaining the initial bursting strength is to ventilate the battery so that the air pressure inside the battery gradually increases. When cracks and air leaks appear in the weld, the air pressure inside the battery is the bursting strength of the weld.

[0063] It is understandable that when a lithium battery is just produced, the weld will have an initial burst strength. When the weld is kept at a certain temperature and pressure for a period of time, static fatigue damage will occur, resulting in a decrease in weld strength. After the lithium battery is put into use, during the charging and discharging process, the pole pieces that make up the core of the lithium battery will thicken during the charging stage, and the pole pieces that make up the core will recover a little during the discharging stage. The change in the thickness of the pole pieces during this process will cause the battery shell parallel to the pole pieces to bulge outward and then recover, bulge outward and then recover again, similar to the cyclical changes of breathing, resulting in dynamic fatigue damage to the welding position between the shell and the cover plate in the lithium battery. Based on this, the computer equipment can obtain the expansion force data, battery shell area and initial burst strength of the target lithium battery as the basic data for fatigue strength prediction, and then can predict in advance the static fatigue strength and dynamic fatigue strength of the target lithium battery within the target service cycle.

[0064] Specifically, the computer equipment can directly measure and obtain the battery shell area and initial burst strength, and the expansion force data can be obtained through the single battery staged charge and discharge cycle test and monitoring. In a specific implementation, the computer equipment can use 166Ah lithium iron phosphate batteries to form a battery pack, and place the battery pack in a 25°C constant temperature room of the energy storage station; the specific charge and discharge process of the battery pack is as follows:

[0065] Step 1: Use 1C constant current to discharge the battery pack to a voltage of 2.5V, and the discharge time is about 1 hour;

[0066] Step 2: Leave the discharged battery pack for 30 minutes;

[0067] Step 3: Perform step charging on the battery pack until the voltage reaches 3.65V, and the charging time is about 1 hour; wherein, the step charging includes: 1.5C constant current charging for 12 minutes, 1C constant current charging for 30 minutes, 0.5C constant current charging for 12 minutes, and 0.33C constant current charging to 3.65V;

[0068] Step 4: Leave the fully charged battery pack for 30 minutes.

[0069] In the above implementation, C represents the rate, 1C=166A; when the battery pack completes the process from step 1 to step 4, it means that the battery has cycled once. It should be noted that as the service time of the battery increases, the battery performance decreases. Therefore, under the same state during the charge and discharge process, the expansion force of the battery will gradually increase over time, and the overall change trend of the expansion force during the charge and discharge process is consistent.

[0070] Indicatively, Figure 2 and Figure 3 As shown, Figure 2 A schematic diagram of a curve showing the change of expansion force during a cycle provided in an embodiment of the present application, Figure 3 A schematic diagram of the relationship between battery expansion force and battery cycle number provided in an embodiment of the present application; in detail, Figure 2 Take two cycles of the battery, that is, two charge and discharge cycles, and draw a curve of the expansion force and the charge and discharge rate to observe the actual change of the expansion force; where a negative rate indicates discharge, a rate of 0 indicates standstill, and a positive rate indicates charging. Figure 2 It can be seen that during the charging process, the expansion force of the battery tends to increase; during the storage process, the expansion force remains basically unchanged; and during the discharge process, the expansion force tends to decrease. Figure 3 Take the maximum and minimum values ​​of each charge and discharge process during the service cycle; the maximum value is the expansion force after the battery is charged, that is, the full charge expansion force, and the minimum value is the expansion force after the battery is discharged, that is, the full discharge expansion force. Assuming that the target service cycle of this application is 10 years, with charging and discharging once a day, and the rest of the time is the storage time of the battery, then the relationship curve between the full charge expansion force and the full discharge expansion force of the target lithium battery during the service cycle and the time change is as follows: Figure 3 As shown, the solid line is the full-charge expansion force curve, and the dotted line is the full-charge expansion force curve.

[0071] In addition, if Figure 4 As shown, Figure 4 A curve diagram of the change of expansion force during a storage process provided in an embodiment of the present application can be obtained through actual measurement; Figure 4 The example is the change in expansion force of a 166Ah single-cell target lithium battery during storage at 25°C and 100% SOC, that is, the relationship between the storage expansion force of the target lithium battery and time during its service cycle. Specifically, during the storage time of the target lithium battery during its service cycle, due to the interaction between internal materials such as positive and negative electrode materials, electrolytes, etc. and external environments such as temperature and humidity, as well as the slow chemical reactions that may occur inside the battery, the overall size of the winding core inside the battery shell will change slightly, thereby generating storage expansion force, which will also affect the stability and actual service cycle of the target lithium battery.

[0072] S120: Inputting the static fatigue strength and the target service cycle into a preset static fatigue damage model to obtain a burst strength reduction output by the static fatigue damage model.

[0073] In this step, after the static fatigue strength of the target lithium battery is determined through step 110, the computer device can obtain a pre-built static fatigue damage model, and then input the static fatigue strength and the target service cycle into the static fatigue damage model to obtain the bursting strength reduction output by the static fatigue damage model, thereby achieving early prediction of the static fatigue damage of the target lithium battery within the target service cycle.

[0074] Specifically, the static fatigue damage model of the present application is constructed by designing experiments to describe the relationship between the burst strength drop of the lithium battery weld, the ambient temperature, the holding pressure (static fatigue strength) and the holding time. The specific experimental design process is as follows:

[0075] Step 1: Determine the burst strength of the lithium battery weld in its initial state.

[0076] In this step, multiple welds between the battery casing and the battery cover are selected, where the number of welds selected can be 10. Then the bursting strength of each weld can be tested in turn, and then the welds corresponding to the abnormal values ​​in the test results are removed, and the average bursting strength of the remaining welds is calculated as the bursting strength of the lithium battery weld in the initial state.

[0077] Step 2: Determine the relationship between temperature and burst strength of lithium battery welds.

[0078] In this step, the weldment is placed in different ambient temperatures for a fixed time, and then the bursting strength of the weld of the weldment is tested, and then the relationship between the decrease in bursting strength and the ambient temperature is analyzed. The ambient temperature can be set according to a certain gradient, such as 25°C, 60°C, 100°C, 140°C, 180°C, and 220°C; then multiple samples are placed at each ambient temperature and left for one hour. The number of samples placed here can be 3 or 5, and there is no limit. After the experiment, the bursting strength of the welds of each weldment can be measured again, and the decrease in bursting strength can be calculated. The decrease in bursting strength is equal to the bursting strength of the weld in the initial state minus the bursting strength after being left at a certain temperature. Finally, the relationship between the decrease in bursting strength of the weld and the ambient temperature can be analyzed based on the measurement results. Schematically, as Figure 5 As shown, Figure 5 A schematic diagram of the relationship between ambient temperature and blasting intensity provided in an embodiment of the present application; Figure 5 It can be seen that there is a linear relationship between the decrease in burst strength of lithium battery welds and the ambient temperature.

[0079] Step 3: Determine the relationship between the holding pressure and the burst strength of the lithium battery weld.

[0080] In this step, the weld is sealed, and a certain air pressure is introduced into the outer shell and the cover plate so that the weld is subjected to a certain pressure, namely the holding pressure, and then placed at a certain ambient temperature for a fixed time; wherein, the holding pressure can be set according to a certain gradient, such as 0.2Mpa, 0.4MPa, 0.6MPa, 0.8MPa, 1MPa, 1.2MPa, 3-5 samples are placed under each holding pressure, the ambient temperature can be 60°C, and the holding time can be 1 hour. After the experiment, the bursting strength of the weld is tested, and then the relationship between the decrease in bursting strength and the holding pressure is analyzed based on the test results. Schematically, as Figure 6 As shown, Figure 6 A schematic diagram of the relationship between the pressure holding strength and the bursting strength provided in an embodiment of the present application; Figure 6 It can be seen that there is an exponential relationship between the decrease in burst strength of lithium battery welds and the holding pressure.

[0081] Step 4: Determine the relationship between the pressure holding time and the burst strength of the lithium battery weld.

[0082] In this step, the weld is sealed and the weld is placed under a certain ambient temperature and a certain holding pressure for different periods of time. The time under a certain pressure is called the holding time. The holding time can be set according to a certain gradient, such as 1h, 2h, 3h, 4h, 5h, 6h. 3-5 samples are placed at each holding time. The holding pressure can be 0.6MPa or half of the bursting strength in the initial state, and the ambient temperature can be 60°C. After the experiment, the bursting strength of the weld is tested, and the relationship between the decrease in bursting strength and the holding time is analyzed based on the test results. Schematically, as shown in Figure 7 As shown, Figure 7 A schematic diagram of the relationship between the pressure holding time and the burst strength provided in the embodiment of the present application; Figure 7 It can be seen that there is a logarithmic relationship between the decrease in burst strength of lithium battery welds and the pressure holding time.

[0083] Based on the above experimental results, the computer equipment can build a static fatigue damage model based on the relationship between the ambient temperature, holding pressure (static fatigue strength), holding time and the decrease in burst strength of the lithium battery weld. Therefore, the computer equipment inputs the static fatigue strength and the target service cycle into the static fatigue damage model, and can directly obtain the decrease in burst strength output by the static fatigue damage model. Among them, the holding time of the target lithium battery can be calculated through the target service cycle, that is, the shelf time of the target lithium battery in the target service cycle.

[0084] S130: Determine the fatigue ratio of the target lithium battery based on the target service cycle and the dynamic fatigue strength, and use a preset dynamic residual strength model to estimate the residual strength of the dynamic fatigue strength, fatigue ratio and initial burst strength to obtain the dynamic residual burst strength of the target lithium battery.

[0085] In this step, after determining the dynamic fatigue strength of the target lithium battery through step S110, the computer device can determine the fatigue ratio of the target lithium battery based on the target service cycle and the dynamic fatigue strength, and obtain a pre-built dynamic residual strength model, and then input the dynamic fatigue strength, fatigue ratio and initial burst strength into the dynamic residual strength model to obtain the dynamic residual burst strength output by the dynamic residual strength model, so as to achieve early prediction of static fatigue damage of the target lithium battery within the target service cycle.

[0086] Among them, fatigue ratio refers to the ratio of the fatigue load that the weld has borne relative to its design life at the target strength level. It is used to convert the complex fatigue damage process of the weld into quantifiable and intuitively understandable parameters. It can be calculated based on the target service cycle and dynamic fatigue strength.

[0087] Specifically, the dynamic residual strength model of the present application is obtained by designing an experiment to describe the relationship between the fatigue ratio and the dynamic residual blasting strength of the lithium battery weld. During the experiment, welded parts with different dynamic fatigue strengths and different fatigue ratios can be selected, and then the welds can be blasted directly, and the dynamic residual blasting strength of the welded parts can be recorded. According to the experimental results, the computer equipment can statistically obtain the relationship between the fatigue ratio and the dynamic residual blasting strength. The experimental design here can be shown in the following table:

[0088]

[0089] Indicatively, Figure 8 As shown, Figure 8 A schematic diagram of the relationship between fatigue ratio and dynamic residual blasting strength provided in an embodiment of the present application; Figure 8 The example shows the experimental results obtained by blasting the weld for the experimental design in the above table. After determining the residual blasting strength corresponding to different fatigue proportions in weldments with dynamic fatigue strength of 0.3 MPa and 0.26 MPa, the computer equipment can also perform curve fitting on the blasting data of the two dynamic fatigue strengths respectively, and determine the relationship between the fatigue proportion and the dynamic residual blasting strength based on the fitting results.

[0090] Based on the above experimental results, the computer equipment can build a dynamic residual strength model based on the relationship between the fatigue ratio of the lithium battery weld and the dynamic residual burst strength. Therefore, after the computer equipment inputs the dynamic fatigue strength, fatigue ratio and initial burst strength into the dynamic residual strength model, the dynamic residual burst strength output by the dynamic residual strength model can be directly obtained.

[0091] S140: determining a final residual burst strength of the target lithium battery according to the burst strength reduction amount and the dynamic residual burst strength, and evaluating the weld reliability of the target lithium battery based on the final residual burst strength.

[0092] In this step, the bursting strength reduction and the dynamic residual bursting strength of the target lithium battery are obtained through step S120 and step S130. The computer device can calculate the final residual bursting strength of the target lithium battery based on the bursting strength reduction and the dynamic residual bursting strength, and then the weld reliability of the target lithium battery can be evaluated based on the final residual bursting strength.

[0093] It is understandable that the decrease in burst strength reflects the attenuation of the anti-destructive ability of the lithium battery weld during the battery storage process. It is an important parameter for evaluating the fatigue damage degree of the weld and can reflect the attenuation of the weld in a static environment. The dynamic residual burst strength is the residual strength value of the weld during the fatigue cycle, which can reflect the actual load-bearing capacity of the weld in a dynamic environment. Therefore, through these two parameters, the computer equipment can accurately calculate the final residual burst strength of the target lithium battery and use it as a basic indicator for evaluating the reliability of the target lithium battery weld.

[0094] Specifically, the final residual burst strength can directly reflect the ultimate destructive force that the weld can withstand after experiencing cumulative fatigue damage, and can provide a scientific basis for predicting the reliability and remaining service life of the weld. Among them, when the final residual burst strength is high, it means that the lithium battery weld is less damaged and has higher reliability; conversely, when the final residual burst strength is low, it means that the lithium battery weld is more damaged and there is a risk of weld failure, so measures such as maintenance or replacement are needed.

[0095] In the above embodiment, when evaluating the weld reliability of the target lithium battery, the expansion force data, battery shell area and initial burst strength of the target lithium battery can be determined first, so as to determine the static fatigue strength and dynamic fatigue strength of the target lithium battery according to the expansion force data and the battery shell area, as the basic data for dynamic and static fatigue strength damage prediction, and then the static fatigue strength and the target service cycle can be input into a preset static fatigue damage model to obtain the burst strength reduction output by the static fatigue damage model, so as to predict in advance the static fatigue damage of the weld of the target lithium battery within the target service cycle; at the same time, the present application can also determine the fatigue proportion of the target lithium battery based on the target service cycle and the dynamic fatigue strength, and use the preset dynamic residual strength model to estimate the residual strength of the dynamic fatigue strength, fatigue proportion and initial burst strength to obtain the dynamic residual burst strength, so as to achieve the early prediction of the dynamic fatigue damage of the weld of the target lithium battery within the target service cycle; finally, the final residual burst strength can be determined according to the burst strength reduction and the dynamic residual burst strength, and the weld reliability of the target lithium battery can be evaluated based on the final residual burst strength. Through this method, the present application can predict in advance the dynamic and static fatigue damage of the target lithium battery within the target service cycle through the static fatigue damage model and the dynamic residual strength model, and use it to perform reliability assessment on the battery welds, thereby significantly improving the accuracy of the assessment results.

[0096] In one embodiment, the expansion force data in step S110 may include full charge expansion force, storage expansion force, and full discharge expansion force; wherein the process of determining the static fatigue strength and dynamic fatigue strength of the target lithium battery within the target service cycle based on the expansion force data and the battery housing area may include:

[0097] S111: Determine the preload force of the target lithium battery, and use a static fatigue strength algorithm to calculate the full charge expansion force, storage expansion force, preload force and battery shell area to obtain the static fatigue strength of the target lithium battery within the target service cycle.

[0098] S112: Calculate the full charge expansion force, the full discharge expansion force and the battery shell area using a dynamic fatigue strength algorithm to obtain the dynamic fatigue strength of the target lithium battery within a target service cycle.

[0099] In this embodiment, when calculating the static and dynamic fatigue strength, the computer device can first obtain the full charge expansion force, storage expansion force and full discharge expansion force in the expansion force data, and determine the preload force of the target lithium battery, so that the static fatigue strength algorithm can be used to calculate the full charge expansion force, storage expansion force, preload force and battery shell area to obtain the static fatigue strength of the target lithium battery within the target service cycle; at the same time, the computer device can also use the dynamic fatigue strength algorithm to calculate the full charge expansion force, full discharge expansion force and battery shell area to obtain the dynamic fatigue strength of the target lithium battery within the target service cycle.

[0100] It should be noted that during the charging and discharging process of the lithium battery, a clamp needs to be put on and a certain force needs to be applied to the clamp so that the clamp produces a certain squeezing force on the lithium battery. The squeezing force here is the preload force.

[0101] It can be understood that the static fatigue strength algorithm is mainly used to evaluate the fatigue strength of the target lithium battery under a constant load, that is, the fatigue strength generated during the storage process; since the batteries in the target lithium battery are stored after being fully charged, they are only affected by the full charge expansion force, storage expansion force and preload force. Therefore, the computer equipment can directly calculate the full charge expansion force, storage expansion force and warning force and the battery shell area through the static fatigue strength algorithm to obtain the static fatigue strength of the target lithium battery within the target service cycle.

[0102] In addition, the dynamic fatigue strength algorithm is mainly used to evaluate the fatigue strength of the target lithium battery under repeated or rapidly changing loads, that is, the dynamically changing fatigue strength generated during the charge and discharge cycle. Therefore, the computer equipment can directly calculate the full charge expansion force, full discharge expansion force and battery shell area through the static fatigue strength algorithm to obtain the dynamic fatigue strength of the target lithium battery within the target service cycle.

[0103] It should be noted that since the dynamic fatigue strength changes continuously during the battery cycle, after the computer calculates the dynamic fatigue strength of the target lithium battery within the target service cycle, it can also calculate the average value and use the calculated average value as the basic data for subsequent fatigue damage prediction.

[0104] In one embodiment, the static fatigue strength algorithm in step S111 may include:

[0105]

[0106] In the formula, Indicates static fatigue strength; Indicates full expansion force; Indicates the storage expansion force; Indicates preload; Indicates the battery casing area.

[0107] In this embodiment, from Figure 2 It can be seen from the data of the change in expansion force during the cycle that the expansion force of the 166Ah single battery is the largest when fully charged, and the target lithium battery used for energy storage is stored and shelved after being fully charged, that is, the expansion force of the target lithium battery during storage and shelving is the sum of the single battery full charge expansion force and the single battery storage expansion force; and the static fatigue strength of the lithium battery weld is the pressure exerted on the weld when the battery is stored and shelved. Therefore, when the computer equipment calculates the static fatigue strength of the target lithium battery, it can use the sum of the full charge expansion force and the storage expansion force minus the preload force before the single battery test, and then divide it by the battery shell area. The result is the static fatigue strength. It should be noted that the addition of the full charge expansion force and the storage expansion force will increase the part corresponding to the storage expansion force during the charging and discharging process, which can increase calculation redundancy and improve data reliability. The specific calculation results can be shown as follows Fig. 9 As shown, Fig. 9 A curve diagram of the change in static fatigue strength of a battery during service provided in an embodiment of the present application; wherein the preload force of the target lithium battery is 283 kgf.

[0108] In one embodiment, the dynamic fatigue strength algorithm in step S112 may include:

[0109]

[0110] In the formula, Indicates full expansion force; Indicates full expansion force; Represents the battery housing area. Through the above algorithm, the amplitude similar to breathing can be represented to simulate the source of fatigue damage through periodic amplitude changes.

[0111] In this embodiment, because the force on the weld changes dynamically during the battery cycle, the pressure on the weld also changes dynamically. Therefore, the dynamic fatigue strength of the weld is the pressure value. Therefore, its dynamic fatigue strength is the difference between the full charge expansion force and the full discharge expansion force divided by the battery shell area. The specific calculation results can be as follows Fig.10 As shown, Fig.10 A schematic diagram of a curve showing the change in dynamic fatigue strength of a battery during service provided in an embodiment of the present application. After determining the target service cycle, the curve can be integrated within the target service cycle and then divided by the target service cycle to obtain the average value to determine the dynamic fatigue strength of the surface service cycle, so as to improve the accuracy of the dynamic fatigue strength and avoid errors caused by data anomalies.

[0112] In one embodiment, the expression of the static fatigue damage model in step S120 may include:

[0113]

[0114] In the formula, represents the burst strength reduction output by the static fatigue damage model; represents the ambient temperature; Pt represents the static fatigue strength, which characterizes the holding pressure; t represents the holding time of the target lithium battery within the target service cycle.

[0115] In a specific implementation, the target lithium battery works in a constant temperature room at 25°C, that is, T=25°C; since the target lithium battery is charged and discharged once a day during the target service life of 10 years, the remaining time is all storage time, that is, t=21.5h, and according to Fig. 9 The holding pressure of the target lithium battery can be determined, that is, Pt= By inputting these data into the static fatigue damage model, the decrease in burst strength of the target lithium battery in the target service cycle can be obtained. =0.035MPa.

[0116] In one embodiment, the process of determining the fatigue ratio of the target lithium battery based on the target service cycle and the dynamic fatigue strength in step S130 may include:

[0117] S141: Determine the weld fatigue life corresponding to the dynamic fatigue strength according to a preset SN curve, and determine the weld fatigue times of the target lithium battery according to the target service cycle.

[0118] S142: Calculate the ratio of the number of weld fatigue times to the weld fatigue life to obtain the fatigue ratio of the target lithium battery.

[0119] In this embodiment, when determining the fatigue ratio of the target lithium battery, the computer device can first determine the weld fatigue life corresponding to the dynamic fatigue strength according to the preset SN curve, and determine the number of weld fatigue times of the target lithium battery according to the target service cycle, and then calculate the ratio of the weld fatigue times and the weld fatigue life to obtain the fatigue ratio of the target lithium battery.

[0120] It can be understood that the SN curve refers to the relationship curve between dynamic fatigue strength and weld fatigue life. To elaborate, when constructing the SN curve, the computer equipment can apply a periodically changing dynamic fatigue strength to the lithium battery weld. The frequency of change of the dynamic fatigue strength is fixed, and the maximum value is called S; then record the number of times the dynamic fatigue strength changes periodically when the weld cracks and leaks. N is also called the fatigue life of the weld under fatigue strength S. Different fatigue strength S values ​​can be set here to obtain fatigue life N values ​​corresponding to different fatigue strengths S, and establish an SN curve. That is, for each S value set, the computer equipment can measure the N value corresponding to the S weld rupture, thereby obtaining different S1, N1, S2, N2..., and draw the generated SN curve. Each N value represents the maximum number of battery cycles under the dynamic fatigue strength S.

[0121] The frequency of change of dynamic fatigue strength can be reduced in proportion to the charge and discharge frequency of the single battery. In order to increase the efficiency of subsequent experiments, this application can be combined with Figure 2 The expansion force data of the cycle is used to proportionally reduce the change of the expansion force over time and divide it into 4 stages, as shown below:

[0122] Stage 1: 0-10s, the expansion force gradually increases, which is equivalent to the battery charging process of the target lithium battery, and the expansion force gradually increases. Specifically, the expansion force can increase from zero to the maximum value;

[0123] Stage 2: 10-15s, the expansion force remains unchanged, which is equivalent to the battery storage process of the target lithium battery, and the expansion force remains unchanged;

[0124] Stage 3: 15-20s, the expansion force gradually decreases, which is equivalent to the battery discharge process of the target lithium battery, and the expansion force gradually decreases. Specifically, the expansion force can decrease from the maximum value to zero;

[0125] Stage 4: 25-30s, the expansion force remains unchanged, which is equivalent to the battery storage process of the target lithium battery, and the expansion force remains unchanged.

[0126] The time of expansion force change in each stage is proportional to the battery cycle time of the target lithium battery; and due to the dynamic fatigue strength , therefore, the frequency of change of dynamic fatigue strength is the same as the frequency of change of expansion force.

[0127] In a specific implementation, the computer equipment can pass a certain amount of gas at a certain frequency, so that the weld is subjected to a certain pressure, even if the weld reaches a certain fatigue strength. Specifically, take a semi-finished battery without electrolyte, connect a hose to the battery injection hole, and then use AB glue to seal the contact position between the hose and the injection hole to ensure the sealing of the battery; in order to ensure that other weak areas of the battery will not crack before the weld during the experiment and affect the experimental results, AB glue can be applied to other weak areas of the battery, such as explosion-proof valves; then the battery is clamped, the hose is connected to the ventilation device, and the ventilation device is connected to the gas source. Here, the ventilation device can automatically control the amount of gas introduced into the battery and the ventilation frequency, which is consistent with the frequency of change of the expansion force in the above four stages; when the battery weld cracks, the battery will leak. At this time, the ventilation device cannot raise the air pressure in the battery to the set value within the set time, and the ventilation device will stop ventilation and record its weld fatigue life.

[0128] Indicatively, if Fig.11 As shown, Fig.11 A schematic diagram of the structure of an SN curve provided in an embodiment of the present application; Fig.11 In the experiment, the fatigue strengths S used were 0.3MPa, 0.25MPa, 0.2MPa, and 0.15MPa, respectively. Then, the battery was ventilated according to the preset expansion force change frequency, and the corresponding weld fatigue life N under each dynamic fatigue strength S was obtained, and then the SN curve was drawn: N*S^3.289=5.864, where =0.993, indicating a good fit.

[0129] Therefore, through the SN curve, the computer equipment can directly determine the fatigue life of the weld corresponding to the dynamic fatigue strength. Fig.10 , when the dynamic fatigue strength of the target lithium battery's target service cycle is averaged and the obtained dynamic fatigue strength S=0.132MPa, according to the SN curve, its corresponding weld fatigue life N=13771. In addition, since the target lithium battery is charged and discharged once a day, when its target service cycle is 10 years, the target lithium battery needs to be charged and discharged 3650 times, that is, the number of weld fatigue times =3650.

[0130] In one embodiment, the expression of the dynamic residual strength model in step S130 may include:

[0131]

[0132] In the formula, represents the dynamic residual blasting strength output by the dynamic residual strength model; Indicates the initial burst intensity; Indicates dynamic fatigue strength; Indicates the fatigue percentage.

[0133] In a specific implementation, the dynamic fatigue strength of the target lithium battery is determined according to the target service cycle. =0.132MPa, and then according to the SN curve, the weld fatigue life N=13771, the weld fatigue times =3650, which is the fatigue ratio = / N=3650 / 13771=0.265. The computer equipment inputs these data into the dynamic residual strength model to obtain the dynamic residual burst strength of the target lithium battery in the target service cycle. =1.179MPa.

[0134] In one embodiment, the process of evaluating the weld reliability of the target lithium battery based on the final residual burst strength in step S140 may include:

[0135] S141: Determine whether the final residual blasting strength is greater than the static fatigue strength and the dynamic fatigue strength.

[0136] S142: If yes, confirm that the weld of the target lithium battery is reliable within the target service life.

[0137] S143: If not, it is determined that the weld of the target lithium battery is unreliable within the target service life.

[0138] In this embodiment, when evaluating the weld reliability of the target lithium battery, the computer device can determine whether the final residual burst strength is greater than the static fatigue strength and the dynamic fatigue strength. If so, the computer device can confirm that the weld of the target lithium battery is reliable within the target service cycle; if not, the computer device can confirm that the weld of the target lithium battery is unreliable within the target service cycle.

[0139] It is understandable that if the final residual burst strength is greater than the static fatigue strength and the dynamic fatigue strength, it indicates that the lithium battery weld can withstand the stress load under static and dynamic conditions within the target service cycle and has not reached a failure state. Therefore, the computer equipment can confirm that the weld of the target lithium battery is reliable and can meet the design requirements and safe operation needs. On the contrary, if the final residual burst strength is less than the static fatigue strength or the dynamic fatigue strength, it means that the lithium battery weld has been subjected to stress beyond its capacity range, and there may be crack propagation, material degradation or other damage accumulation phenomena, and normal operation cannot be guaranteed within the target service cycle. Therefore, the computer equipment can confirm that the weld of the target lithium battery is unreliable, and repair or replacement measures need to be taken to ensure the safety of the target lithium battery.

[0140] The weld reliability device provided in the embodiment of the present application is described below. The weld reliability device described below and the weld reliability method described above can be referenced to each other.

[0141] In one embodiment, Fig.12 As shown, Fig.12 A structural schematic diagram of a weld reliability assessment device provided in an embodiment of the present application; the present application also provides a weld reliability assessment device, including a fatigue strength determination module 210, a strength drop prediction module 220, a residual strength prediction module 230 and a reliability assessment module 240, specifically including the following:

[0142] The fatigue strength determination module 210 is used to obtain a target lithium battery and determine the expansion force data, battery shell area and initial burst strength of the target lithium battery, so as to determine the static fatigue strength and dynamic fatigue strength of the target lithium battery within a target service cycle based on the expansion force data and the battery shell area.

[0143] The strength reduction prediction module 220 is used to input the static fatigue strength and the target service cycle into a preset static fatigue damage model to obtain the burst strength reduction output by the static fatigue damage model.

[0144] The residual strength prediction module 230 is used to determine the fatigue ratio of the target lithium battery based on the target service cycle and dynamic fatigue strength, and use a preset dynamic residual strength model to estimate the residual strength of the dynamic fatigue strength, fatigue ratio and initial burst strength to obtain the dynamic residual burst strength of the target lithium battery.

[0145] The reliability evaluation module 240 is used to determine the final residual burst strength of the target lithium battery according to the burst strength reduction and the dynamic residual burst strength, and obtain the weld reliability of the target lithium battery based on the final residual burst strength evaluation.

[0146] In the above embodiment, when evaluating the weld reliability of the target lithium battery, the expansion force data, battery shell area and initial burst strength of the target lithium battery can be determined first, so as to determine the static fatigue strength and dynamic fatigue strength of the target lithium battery according to the expansion force data and the battery shell area, as the basic data for dynamic and static fatigue strength damage prediction, and then the static fatigue strength and the target service cycle can be input into a preset static fatigue damage model to obtain the burst strength reduction output by the static fatigue damage model, so as to predict in advance the static fatigue damage of the weld of the target lithium battery within the target service cycle; at the same time, the present application can also determine the fatigue proportion of the target lithium battery based on the target service cycle and the dynamic fatigue strength, and use the preset dynamic residual strength model to estimate the residual strength of the dynamic fatigue strength, fatigue proportion and initial burst strength to obtain the dynamic residual burst strength, so as to achieve the early prediction of the dynamic fatigue damage of the weld of the target lithium battery within the target service cycle; finally, the final residual burst strength can be determined according to the burst strength reduction and the dynamic residual burst strength, and the weld reliability of the target lithium battery can be evaluated based on the final residual burst strength. Through this method, the present application can predict in advance the dynamic and static fatigue damage of the target lithium battery within the target service cycle through the static fatigue damage model and the dynamic residual strength model, and use it to perform reliability assessment on the battery welds, thereby significantly improving the accuracy of the assessment results.

[0147] In one embodiment, the expansion force data in the fatigue strength determination module 210 includes full charge expansion force, storage expansion force and full discharge expansion force; the fatigue strength determination module 210 may also include:

[0148] The static fatigue damage calculation submodule is used to determine the preload force of the target lithium battery, and uses the static fatigue strength algorithm to calculate the full charge expansion force, storage expansion force, preload force and battery shell area to obtain the static fatigue strength of the target lithium battery within the target service cycle.

[0149] The dynamic fatigue damage calculation submodule is used to calculate the full charge expansion force, full discharge expansion force and battery shell area using a dynamic fatigue strength algorithm to obtain the dynamic fatigue strength of the target lithium battery within the target service cycle.

[0150] In one embodiment, the static fatigue strength algorithm used in the static fatigue damage calculation submodule may include:

[0151]

[0152] In the formula, Indicates static fatigue strength; Indicates full expansion force; Indicates the storage expansion force; Indicates preload; Indicates the battery casing area.

[0153] In one embodiment, the dynamic fatigue strength algorithm used in the dynamic fatigue damage calculation submodule may include:

[0154]

[0155] In the formula, Indicates full expansion force; Indicates full expansion force; Indicates the battery casing area.

[0156] In one embodiment, the expression of the static fatigue damage model used in the strength reduction prediction module 220 may include:

[0157]

[0158] In the formula, represents the burst strength reduction output by the static fatigue damage model; represents the ambient temperature; Pt represents the static fatigue strength, which characterizes the holding pressure; t represents the holding time of the target lithium battery within the target service cycle.

[0159] In one embodiment, the remaining strength prediction module 230 may include:

[0160] The data determination submodule is used to determine the weld fatigue life corresponding to the dynamic fatigue strength according to a preset SN curve, and to determine the number of weld fatigue times of the target lithium battery according to the target service cycle.

[0161] The fatigue ratio calculation submodule is used to calculate the ratio of the number of weld fatigue times and the weld fatigue life to obtain the fatigue ratio of the target lithium battery.

[0162] In one embodiment, the expression of the dynamic residual strength model used in the residual strength prediction module 230 may include:

[0163]

[0164] In the formula, represents the dynamic residual blasting strength output by the dynamic residual strength model; Indicates the initial burst intensity; Indicates dynamic fatigue strength; Indicates the fatigue percentage.

[0165] In one embodiment, the process of evaluating the weld reliability of the target lithium battery based on the final residual burst strength in step S140 may include:

[0166] The strength judgment submodule is used to judge whether the final residual blasting strength is greater than the static fatigue strength and the dynamic fatigue strength.

[0167] The first result confirmation submodule is used to confirm that the weld of the target lithium battery is reliable within the target service period when it is determined that the final residual burst strength is greater than the static fatigue strength and the dynamic fatigue strength.

[0168] The second result confirmation submodule is used to confirm that the weld of the target lithium battery is unreliable within the target service period when it is determined that the final residual burst strength is not greater than the static fatigue strength and the dynamic fatigue strength.

[0169] In one embodiment, the present application also provides a computer device having computer-readable instructions stored therein. When the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the weld reliability assessment method as described in any one of the above embodiments.

[0170] Indicatively, if Fig.13 As shown, Fig.13 This is a schematic diagram of the internal structure of a computer device provided in an embodiment of the present application. The computer device 300 may be provided as a server. Fig.13 The computer device 300 includes a processing component 302, which further includes one or more processors, and a memory resource represented by a memory 301 for storing instructions executable by the processing component 302, such as an application. The application stored in the memory 301 may include one or more modules, each corresponding to a set of instructions. In addition, the processing component 302 is configured to execute instructions to perform the weld reliability assessment method of any of the above embodiments.

[0171] The computer device 300 may further include a power supply component 303 configured to perform power management of the computer device 300, a wired or wireless network interface 304 configured to connect the computer device 300 to a network, and an input / output (I / O) interface 305. The computer device 300 may operate based on an operating system stored in the memory 301, such as Windows Server TM, Mac OS X TM, Unix TM, Linux TM, Free BSD TM, or the like.

[0172] Those skilled in the art will understand that Fig.13 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0173] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0174] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can refer to each other.

[0175] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A weld reliability assessment method, characterized in that: The method comprises: Acquire a target lithium battery, and determine expansion force data, battery housing area, and initial burst strength of the target lithium battery, so as to determine static fatigue strength and dynamic fatigue strength of the target lithium battery within a target service cycle based on the expansion force data and the battery housing area; Inputting the static fatigue strength and the target service cycle into a preset static fatigue damage model to obtain a burst strength reduction output by the static fatigue damage model; Determine the fatigue ratio of the target lithium battery based on the target service cycle and the dynamic fatigue strength, and use a preset dynamic residual strength model to estimate the residual strength of the dynamic fatigue strength, the fatigue ratio and the initial burst strength to obtain the dynamic residual burst strength of the target lithium battery; The final residual burst strength of the target lithium battery is determined according to the burst strength reduction and the dynamic residual burst strength, and the weld reliability of the target lithium battery is evaluated based on the final residual burst strength.

2. The weld reliability assessment method according to claim 1, characterized in that: The expansion force data includes full charge expansion force, storage expansion force and full discharge expansion force; The determining the static fatigue strength and the dynamic fatigue strength of the target lithium battery within a target service cycle based on the expansion force data and the battery housing area includes: Determine the preload force of the target lithium battery, and calculate the full charge expansion force, the storage expansion force, the preload force and the battery housing area using a static fatigue strength algorithm to obtain the static fatigue strength of the target lithium battery within a target service cycle; The full charge expansion force, the full discharge expansion force and the battery housing area are calculated using a dynamic fatigue strength algorithm to obtain the dynamic fatigue strength of the target lithium battery within the target service cycle.

3. The weld reliability assessment method according to claim 2, characterized in that: The static fatigue strength algorithm includes: In the formula, Indicates static fatigue strength; Indicates full expansion force; Indicates the storage expansion force; Indicates preload; Indicates the battery casing area.

4. The weld reliability assessment method according to claim 2, characterized in that: The dynamic fatigue strength algorithm includes: In the formula, Indicates full expansion force; Indicates full expansion force; Indicates the battery casing area.

5. The weld reliability assessment method according to claim 1, characterized in that: The expression of the static fatigue damage model includes: In the formula, represents the burst strength reduction output by the static fatigue damage model; represents the ambient temperature; Pt represents the static fatigue strength, which characterizes the holding pressure; t represents the holding time of the target lithium battery within the target service cycle.

6. The weld reliability assessment method according to claim 1, characterized in that: The determining the fatigue ratio of the target lithium battery based on the target service cycle and the dynamic fatigue strength includes: Determine the weld fatigue life corresponding to the dynamic fatigue strength according to a preset SN curve, and determine the weld fatigue times of the target lithium battery according to the target service cycle; The ratio of the weld fatigue times to the weld fatigue life is calculated to obtain the fatigue ratio of the target lithium battery.

7. The weld reliability assessment method according to claim 1, characterized in that: The expression of the dynamic residual strength model includes: In the formula, represents the dynamic residual blasting strength output by the dynamic residual strength model; Indicates the initial burst intensity; Indicates dynamic fatigue strength; Indicates the fatigue percentage.

8. The weld reliability assessment method according to claim 1, characterized in that: The evaluating the weld reliability of the target lithium battery based on the final residual burst strength includes: Determining whether the final residual blasting strength is greater than the static fatigue strength and the dynamic fatigue strength; If yes, it is confirmed that the weld of the target lithium battery is reliable within the target service period; If not, it is confirmed that the weld of the target lithium battery is unreliable within the target service cycle.

9. A weld reliability assessment device, characterized in that: include: A fatigue strength determination module, used to obtain a target lithium battery, and determine the expansion force data, battery shell area and initial burst strength of the target lithium battery, so as to determine the static fatigue strength and dynamic fatigue strength of the target lithium battery within a target service cycle based on the expansion force data and the battery shell area; A strength reduction prediction module, used for inputting the static fatigue strength and the target service cycle into a preset static fatigue damage model to obtain a burst strength reduction output by the static fatigue damage model; A residual strength prediction module, used to determine the fatigue ratio of the target lithium battery based on the target service cycle and the dynamic fatigue strength, and to estimate the residual strength of the dynamic fatigue strength, the fatigue ratio and the initial burst strength using a preset dynamic residual strength model to obtain the dynamic residual burst strength of the target lithium battery; A reliability evaluation module is used to determine the final residual burst strength of the target lithium battery according to the burst strength reduction and the dynamic residual burst strength, and to obtain the weld reliability of the target lithium battery based on the final residual burst strength evaluation.

10. A computer device, characterized in that: include: one or more processors, and memory; The memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the steps of the weld reliability assessment method according to any one of claims 1 to 8 are performed.

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