Method and system for testing the structural integrity of metal joints

Abstract

To provide a method for testing the structural integrity of a metal joint such as a weld.SOLUTION: The method includes applying stress to a weld (12a, 12b), and measuring a resistance of a circuit including the weld during application of the stress to the weld. The structural integrity of the weld is determined by comparing the measured resistance with a baseline resistance. The resistance may be measured using four-terminal (4T) sensing. The measured and baseline resistances may be respectively obtained from a real part of a measured complex impedance of the weld under stress and a real part of a measured complex impedance of the weld not under stress.SELECTED DRAWING: Figure 2

Description

[Background technology]

[0001] Various techniques for nondestructive testing of welds are commonly known. Each of these techniques has certain drawbacks. For example, visual inspection (or image recognition-based inspection) offers high throughput and repeatability, but does not provide information about the interior of the weld. Visual inspection requires that the weld not be obscured by packaging. X-ray inspection also allows for high throughput and reveals the interior of the weld, but requires expensive equipment and radiation shielding. Ultrasonic inspection requires the direct application of a probe or scanning head to all relevant welds, which poses a significant challenge for automation when many small, individual welds per product must be inspected. Similarly, eddy current inspection requires local, direct contact and requires significant mechanical automation. Penetrant testing and magnetic particle testing are also known, but these require the application of a working medium or particles, which is generally too burdensome for high-throughput manufacturing of relatively inexpensive products such as batteries. Summary of the Invention [Problem to be solved by the invention]

[0002] Thus, existing non-destructive techniques for testing welds either do not provide access to the interior of the weld, require expensive equipment, or require multiple mechanical contacts per manufactured item. [Means for solving the problem]

[0003] In accordance with one aspect of the inventive concept, there is provided a method for testing the structural integrity or integrity of a metal bond, the method comprising applying a stress to the metal bond, measuring the resistance of a circuit including the metal bond while the metal bond is being stressed, and determining the structural integrity of the metal bond according to the magnitude of the difference between the measured resistance and a baseline resistance.

[0004] The metal joint may be a weld, such as a battery weld.

[0005] The resistance can be measured using four-terminal (4T) sensing, and the measured resistance and baseline resistance can be obtained from the real part of the measured complex impedance of the stressed metal joint and the real part of the measured complex impedance of the unstressed metal joint, respectively.

[0006] The stress can be at least one of a mechanical stress, a thermal stress, an acoustic stress, and an electrical stress. The stress can be applied by driving a current through the metallurgical joint, such as a pulsed DC current through the metallurgical joint, or by a mechanical actuator.

[0007] The method may further include obtaining a baseline resistance by measuring the resistance of the metallurgical joint with no stress applied to the metallurgical joint.

[0008] In accordance with another aspect of the inventive concept, there is provided a system for testing the structural integrity of a metallic joint, the system comprising: a stimulation device configured to apply a stress to the metallic joint; a resistance measurement device configured to measure the resistance of the metallic joint while the metallic joint is stressed by the stimulation device; and a test automation platform, the test automation platform comprising a memory storing executable instructions and a processor configured to execute instructions retrieved from the memory that, when executed, cause the processor to determine the structural integrity of the metallic joint based on a comparison between the measured resistance and a baseline resistance.

[0009] The stimulation device and the resistance measurement device may operate under the control of a test automation platform.

[0010] The resistance measuring device can be configured to measure the complex impedance of the metallurgical joint while the metallurgical joint is under stress, and the instructions, when executed, can cause the processor to determine the difference between the real component of the measured impedance and a baseline resistance.

[0011] The stress can be at least one of a mechanical stress, a thermal stress, an acoustic stress, and an electrical stress. The stimulation device can include a mechanical actuator configured to apply a mechanical stress to the metal junction, or can include a current source configured to apply a pulsed DC current across the metal junction.

[0012] The metallurgical joint may be a weld.

[0013] In accordance with another aspect of the inventive concept, there is provided a method for testing the structural integrity of a metallic joint, the method including measuring the resistance of the metallic joint to obtain a baseline impedance of the metallic joint, applying a stress to the metallic joint, measuring the resistance of the metallic joint while stressing the metallic joint to obtain a stressed resistance of the weld, determining a tested difference between the baseline resistance of the metallic joint and the stressed resistance of the metallic joint, and comparing the tested difference to a threshold value, where a test result of lack of structural integrity is determined when the tested difference exceeds the threshold value.

[0014] The metallurgical joint may be a weld and the stress may be at least one of a mechanical stress, a thermal stress, an acoustic stress, and an electrical stress.

[0015] These and other aspects and features of the inventive concepts will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0016] [Figure 1A] FIG. 1 is a schematic diagram of a pouch cell battery that constitutes an example of an article of manufacture having metal joints to be tested. [Figure 1B] FIG. 1 is a schematic diagram of a pouch cell battery that constitutes an example of an article of manufacture having metal joints to be tested. [Figure 2] FIG. 1 is a schematic diagram of a test apparatus for testing pouch cell battery welds according to one embodiment. [Figure 3] FIG. 3 is a circuit diagram of a test apparatus for testing the welds of the pouch cell battery of FIG. 2. [Figure 4A] FIG. 10 is a schematic diagram of a test apparatus for testing welds in a pouch cell battery according to another embodiment. [Figure 4B] FIG. 10 is a schematic diagram of a test apparatus for testing welds in a pouch cell battery according to another embodiment. [Figure 5] 1 is a flowchart referenced in describing a method for testing a metal bond according to one embodiment. [Figure 6] 10 is a flowchart referred to in describing a method for testing a metal bond according to another embodiment. [Figure 7] 10 is a flowchart that is referred to in describing a method for testing a metal bond according to another embodiment. [Figure 8] 1 is a graph showing impedance measurements of a stressed metal joint. [Figure 9] FIG. 1 is a simplified block diagram of a test automation platform (TAP) operably coupled to stimulus and measurement equipment in accordance with a representative embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] The method and system for testing the structural integrity of metal joints of the present inventive concept is based on impedance (or resistance) measurements that require the establishment of only two electrical contacts. These contacts do not require a high degree of repeatability because the focus is on observing induced changes in impedance (or resistance) rather than absolute impedance (or resistance) values. This allows for a reduction in the requirements for mechanical automation needed to establish the contacts, thereby increasing throughput and repeatability while reducing costs.

[0018] Furthermore, the method and system of the present inventive concept classifies metal joints directly based on their electrical properties, which are of primary concern in battery manufacturing and contact welding (rather than, for example, mechanical load-bearing capacity), allowing for a more direct assessment of relevant quality aspects than existing approaches that measure other aspects of the weld, such as visual uniformity.

[0019] The following description presents, as an example, the testing of welds in pouch cell batteries. However, the inventive concepts are in no way limited to a particular type of metal joint (e.g., a weld) being tested, nor are they in any way limited to the article of manufacture (e.g., a battery) that contains the metal joint. By way of example, other types of metal joints that can be tested in accordance with the inventive concepts include solder joints and brazed joints.

[0020] Furthermore, in the case of welded joints, the inventive concepts are not limited by the type of welding process. By way of example, the processes used to form the welded joints under test can be MIG (Gas Metal Arc Welding) (GMAW), TIG (Gas Tungsten Arc Welding) (GTAW), Stick-Shielded Metal Arc Welding (SMAW), Flux-Cored Arc Welding (FCAW), Energy Beam Welding (EBW), Atomic Hydrogen Welding (AHW), Gas Tungsten Arc Welding, and Plasma Arc Welding. Similarly, the inventive concepts are not limited by the type of welded joint. By way of example, the types of welded joints can be lap joints, butt joints, corner joints, T-joints, and edge joints.

[0021] FIG. 1A is a schematic top view of a pouch cell battery 100, and FIG. 1B is a partial cutaway side view of the pouch cell battery of FIG. 1A. Referring to FIGS. 1A and 1B together, the pouch cell battery 100 includes an outer casing or pouch 10 and external electrodes 11 a and 11 b. Within the pouch 10 are one or more battery cells (not shown) electrically connected to the external electrodes 11 a and 11 b. In this example, the battery cells are connected to the external electrodes 11 a and 11 b by welding an internal electrode foil 13 to the external electrodes 11 a and 11 b. The resulting welds are shown in FIGS. 1A and 1B as 12 a and 12 b. As best seen in FIG. 1B, the welds 12 a and 12 b are enclosed within the pouch 10 and are therefore invisible to both the naked eye and an image recognition camera.

[0022] A method for testing the structural integrity of the welds 12a and 12b of the pouch cell battery 100 of FIGS. 1A and 1B in accordance with one embodiment of the inventive concept will now be described with reference to FIG.

[0023] This and other embodiments described herein include "stimulation" and "readout" components, but are not intended to be limited by the terminology.

[0024] The stimulus component is characterized by providing a disturbance or stress to the metal joint under test. By way of example, the stress can take the form of mechanical, thermal, acoustic, and electrical stress. One example of mechanical stress is the application of a compressive force to the metal joint from a mechanical actuator. On the other hand, thermal stress can be applied to the metal joint by, for example, localized infrared heating or a laser. One example of electrical stress is a relatively strong DC current or a relatively strong pulsed DC current applied across the metal joint. Acoustic stress can take the form of, for example, sound waves that induce vibrations in the metal joint.

[0025] The readout component is characterized by measuring the resistance (or impedance) across the metallic junction under test while the metallic junction is subjected to the stress of the stimulating component. This stress-induced resistance measurement is compared to a baseline resistance that represents the resistance of the metallic junction while unstressed. The baseline resistance can be determined in advance or simultaneously with the stress-induced resistance measurement. As previously mentioned, the focus is on the change in resistance from a non-stressed state to a stressed state, rather than the absolute value of the measurement itself. Without being bound by theory, the inventors hypothesize that metallic junctions with relatively low structural integrity will exhibit greater instability, i.e., greater fluctuations in resistance or impedance, when stressed than metallic junctions with higher structural integrity.

[0026] 2, the stimulation component is achieved by applying a pulsed DC current across external electrodes 11a and 11b using wired electrodes 13a and 13b. By way of non-limiting example, the pulsed DC current can have an amplitude in the range of 1 ampere to 100 amperes (e.g., 30 amperes) and a pulse width in the range of 1 second to 60 seconds (e.g., 5 seconds).

[0027] The readout component of the embodiment of Figure 2 is achieved by four-terminal (4T) sensing, that is, 4T sensing is characterized by separate pairs of current-carrying electrodes 14 (as force) and voltage-sensing electrodes 15 (as sense), as shown in Figure 2. However, the inventive concept is not limited to 4T sensing of impedance, and other impedance or resistance measurement techniques may also be employed.

[0028] Figure 3 is a circuit diagram representing the electrical device of the test setup of Figure 2. In Figure 3, Zcell represents the impedance of the cells and connections in the pouch-cell battery 100 of Figure 2, and Rweld represents the resistance of the welds 12a and 12b of Figure 2. Rweld can change with the application of a stimulus.

[0029] 3, reference numeral 19 denotes a pulsed current source including a DC voltage source 15, a switch 16, and a resistance component 17. The pulsed current source 19 is operable to apply a pulsed DC test current across an electrical circuit including Rweld, Zcell, and Rweld.

[0030] The electrical setup is configured to measure the change in weld impedance in response to stress applied by a pulsed DC current source 16. The physical quantity measured is Rweld. That is, the real part of the weld impedance has empirically higher diagnostic relevance than the imaginary part. Therefore, it may be desirable to select a measurement frequency for the impedance measurement that cancels out the background capacitance and inductance of the battery cell. The frequency used for the impedance measurement should also preferably allow for fast measurements. In combination with the above criteria, a frequency of approximately 1 kHz may be a good choice. Alternatively, the stimulus itself can be modulated to increase the signal-to-noise (S / N) ratio of the measurement.

[0031] As shown in FIG. 3, the 4T impedance measuring method includes an AC current source 20 as the force and a phase sensitive voltmeter 21 as the sense.

[0032] Figures 4A and 4B are schematic diagrams to which reference will be made in describing another embodiment of the inventive concept. Again, the example given relates to testing welds contained within a pouch cell battery 100, with like reference numerals indicating similar elements to those described with respect to Figures 2 and 3. However, here the stimulus component is a mechanical stress applied to the welds of the pouch cell battery 100.

[0033] As in the previous embodiment, impedance measurements are performed by 4T sensing, and therefore the configuration includes separate pairs of current-carrying electrodes 14 (as force) and voltage-sensing electrodes 15 (as sense), as shown in Figure 4B.

[0034] The stimulus in this embodiment is provided by a mechanical actuator 23 that applies a downward, compressive, bending, or torque force to welds 12a and 12b. When the mechanical actuator is engaged with welds 12a and 12b, the welds are considered to be in a stressed state and impedance measurements are taken using 4T sensing. Similar to the pulsed DC current applied as the stimulus in the embodiments of Figures 2 and 3, the mechanical actuator can be moved up and down cyclically to apply a pulsed mechanical stress.

[0035] FIG. 5 is a flow chart that is referred to in describing a method for testing the structural integrity of a metallic joint in accordance with an embodiment of the inventive concept.

[0036] First, stress is applied to a metal joint in step 501. As previously mentioned, the metal joint may be, by way of example, a welded joint, a soldered joint, or a brazed joint, and the stress may take various forms, such as mechanical, thermal, acoustic, and electrical stress.

[0037] Next, in step 502, the resistance of the conductive circuit including the metal junction is measured. The circuit may be made solely of the metal junction (i.e., the measurement may be made directly across the metal junction). Alternatively, the practicality of the product or package containing the metal junction may dictate that the circuit include other components. See, for example, FIG. 3 above, where the circuit includes a Zcell.

[0038] In step 503, the measured resistance is compared to a baseline resistance to determine the difference, ΔR, between the two. The baseline resistance may be derived, for example, from previous resistance measurements of an unstressed metal joint similarly constructed and known to have acceptable structural integrity. Alternatively, the baseline resistance may be obtained by measuring the resistance of the metal joint under test in an unstressed state. If the difference between the baseline resistance and the measured resistance exceeds a predetermined threshold, ΔR, the metal joint is deemed to have a defect (or insufficient structural integrity). This predetermined threshold, ΔR, may be determined from data derived from previous measurements of an unstressed metal joint similarly constructed and known to have acceptable structural integrity, and previous resistance measurements of the same metal joint that has been stressed.

[0039] FIG. 6 is a flow chart that is referred to in describing a method for testing the structural integrity of a metallic joint in accordance with another embodiment of the inventive concept.

[0040] First, a resistance measurement device is electrically connected across the metal junction in step 601. As previously mentioned, this connection can be made directly across the metal junction, or the connection can be made across the metal junction in electrical contact with another component.

[0041] Next, in step 602, the resistance across the metallurgical junction is observed using the equipment connected in step 601. This measurement is taken to confirm that contact has been successfully established and to obtain a baseline resistance against which subsequent measurements are compared.

[0042] In step 603, one or several external stimuli are applied to the cell, particularly to portions of the cell in close proximity to the weld being inspected. As previously mentioned, these stimuli can take several forms. Examples include pulsed electrical current, mechanical stress by an actuator, localized heating (e.g., by a heating element, infrared radiation, or laser), and ultrasound or generally vibration by direct contact or through the air.

[0043] In step 604, the resistance across the stressed metal junction is measured using the equipment connected in step 601 to obtain the stressed resistance.

[0044] In step 605, the difference AR between the stressed resistance and the baseline resistance is determined.

[0045] A determination is then made in step 606 as to whether the difference ΔR exceeds a threshold difference ΔRth. If the difference ΔR exceeds the threshold difference ΔRth, the metal contact is deemed to be defective in step 608. Otherwise, the metal contact is deemed not to be defective in step 607. This threshold difference ΔRth may be determined from data derived from previous measurements of unstressed metal joints similarly constructed and known to have acceptable structural integrity, and previous resistance measurements of the same metal joints that have been stressed.

[0046] FIG. 7 is a flow chart that is referred to in describing a method for testing the structural integrity of a metallic joint in accordance with another embodiment of the inventive concept.

[0047] First, a resistance measurement device is electrically connected across the metal junction in step 701. As previously mentioned, this connection can be made directly across the metal junction, or the connection can be made across the metal junction in electrical contact with another component.

[0048] Next, in step 702, the resistance across the metallurgical junction is observed using the equipment connected in step 701. This measurement is taken to confirm that contact has been successfully established and to obtain a baseline resistance against which subsequent measurements are compared.

[0049] In step 703, one or several external stimuli are applied to the cell, particularly to portions of the cell in close proximity to the weld under inspection. As previously mentioned, these stimuli can take several forms. Examples include pulsed electrical current, mechanical stress by an actuator, localized heating (e.g., by a heating element, infrared radiation, or laser), and ultrasound or vibration in general, by direct contact or through the air.

[0050] In step 704, the resistance across the stressed metal junction is measured using the equipment connected in step 701 to obtain the stressed resistance.

[0051] The embodiment of Figure 7 is characterized, at least in part, by taking multiple (N) measurements of the stressed resistor. Thus, if the number n of a given "nth" measurement is less than the number (N+1) of the (N+1)th measurements, the stress is temporarily removed in step 705, and n becomes n+1 in step 706. In step 703, the stress is reapplied to the metallurgical junction, and in step 704, the stressed resistor is observed and another stressed resistor measurement is taken. Measurements continue in this manner until n = N+1, thus taking N stressed resistor measurements.

[0052] A statistical representation of the N stressed resistance measurements is determined in step 707. In this example embodiment, this statistical representation is the average of the N stressed resistance measurements.

[0053] In step 708, the difference AR between a statistical representation (eg, average) of the N stressed resistance measurements and the baseline resistance is determined.

[0054] A determination is then made in step 709 as to whether the difference ΔR exceeds a threshold difference ΔRth. If the difference ΔR exceeds the threshold difference ΔRth, the metal contact is deemed to be defective in step 608. Otherwise, the metal contact is deemed not to be defective in step 607. This threshold difference ΔRth may be determined from data derived from previous measurements of unstressed metal joints similarly constructed and known to have acceptable structural integrity, and previous resistance measurements of the same metal joints that have been stressed.

[0055] Figure 8 is a graph of impedance and resistance measurements derived from a preliminary experiment conducted on metal pieces contacted by soldering. In this experiment, a DC current pulse stimulus was applied. Initially, the resistance of the solder joint was on the order of 90+ microohms during the first pulse duration of approximately 1 second. Next, a screwdriver was used to intentionally damage the solder joint, causing the resistance to increase to approximately 120 microohms. It can be easily seen that the damaged joint responded with a decrease in resistance when stressed by the DC current pulse.

[0056] FIG. 9 is a simplified block diagram of a test automation platform (TAP) 900 operatively coupled to a stimulus and measurement device 1000 according to a representative embodiment.

[0057] The TAP 900 comprises a processor 901, a memory 902, a database 903, a test module 904, and a user interface 905. The test automation platform 900 communicates with various components, including the stimulus and measurement equipment 1000, using a communication bus 906.

[0058] Processor 901 may be any hardware device capable of executing instructions stored in memory 902 in accordance with test module 904. Processor 901 may execute these instructions to perform some or all of the methods described herein. Additionally, processor 901 may be distributed among multiple devices, for example, to accommodate methods that must be performed in a distributed fashion requiring multiple sets of memory / processor combinations.

[0059] The processor 901 is tangible and non-transitory and represents one or more processors. The term "non-transitory," as used herein, should not be construed as a permanent characteristic of a state, but as a characteristic of a state that lasts for a period of time. The term "non-transitory" specifically negates transient characteristics, such as characteristics of a carrier wave or signal, or other form of thing that exists only temporarily at any time and in any place. A processor is a manufactured and / or mechanical component. The processor 901 of the TAP 900 is configured to execute software instructions to perform functions as described in various embodiments herein. The processor 901 may be a general-purpose processor or may be part of an application-specific integrated circuit (ASIC). The processor 901 may be (or include) a microprocessor, microcomputer, processor chip, controller, microcontroller, digital signal processor (DSP), state machine, or programmable logic device. Processor 901 may be (or may include) logic circuitry, including a programmable gate array (PGA), such as a field programmable gate array (FPGA), or another type of circuitry including discrete gate and / or transistor logic. Processor 901 may be a central processing unit (CPU), a graphics processing unit (GPU), or both. Additionally, any processor described herein may include multiple processors, parallel processors, or both. Multiple processors may be included in or coupled to a single device or multiple devices.

[0060] The memory 902 and the database 903 may include various memories, such as, for example, cache memory or system memory, etc. Thus, the memory 902 and the database 903 may include static random-access memory (SRAM), dynamic RAM (DRAM), flash memory, read only memory (ROM), or other similar memory devices.

[0061] Memory 902 may include various modules, each of which includes a set of related processor-executable instructions that correspond to a particular function of TAP 800.

[0062] Database 903 can include a library of measured resistances of various types of metallic joints, including data derived from previous measurements of unstressed metallic joints similarly constructed and known to have acceptable structural integrity, and previous resistance measurements of the same metallic joints that have been stressed. Database 903 can include one or more machine-readable non-transitory storage media, such as read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, or similar storage media. In various embodiments, database 903 can store instructions to be executed by processor 901 or data that can be used by processor 901 in operating (alone or in conjunction with memory 902 and test module 904).

[0063] Test module 904 is a software module executed by processor 901 that controls stimulus and measurement equipment to perform testing of metal joints according to the above embodiments and receive measurement data and results for storage in database 903 and / or display on user interface 905.

[0064] The user interface 905 can include one or more devices that enable communication with a user. The user interface 905 comprises a graphical user interface (GUI) and an application programming interface (API). The GUI allows the user to interact with the TAP 900 through a graphical representation of the system configuration and settings. The API allows the user to interact with the TAP 900 through a programmable command set. Thus, the API provides a programming interface that allows the user to integrate the solution into their environment and also allows the integration of customer-specific metallurgical joint profiles and libraries. This interface can also be used to extend the system for future protocols, both wired and wireless.

[0065] While the present disclosure refers to exemplary embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present teachings. Accordingly, it should be understood that the above-described embodiments are illustrative rather than limiting. The claims as originally filed are as follows: Claim 1: 1. A system for testing the structural integrity of a metallurgical joint, comprising: a stimulation device configured to apply stress to the metallurgical joint; a resistance measuring device configured to measure the resistance of the metallurgical junction while the metallurgical junction is stressed by the stimulation device; a test automation platform (900) comprising a memory (902) storing executable instructions and a processor (901) configured to execute the instructions retrieved from the memory (902); Equipped with The instructions, when executed, cause the processor (901) to determine the structural integrity of the metallurgical joint based on a comparison between the measured resistance and a baseline resistance. Claim 2: The system of claim 1 , wherein the stimulation device and the resistance measuring device operate under the control of the test automation platform (900). Claim 3: the resistance measurement device is configured to measure a complex impedance of the metallurgical joint while the metallurgical joint is under stress; The system of claim 1 , wherein the instructions, when executed, cause the processor to determine a difference between a real component of the measured impedance and the baseline resistance. Claim 4: The system of claim 1 , wherein the stress is at least one of a mechanical stress, a thermal stress, an acoustic stress, and an electrical stress. Claim 5: The system of claim 1 , wherein the stimulation device includes a mechanical actuator (23) configured to apply a mechanical stress to the metal junction. Claim 6: 10. The system of claim 1, wherein the stimulation device includes a current source configured to apply a pulsed DC current across the metallic junction. Claim 7: The system of claim 1 , wherein the metal joint is a weld. Claim 8: 1. A method for testing the structural integrity of a metallurgical joint, comprising: measuring the resistance of the metallurgical joint to obtain a baseline impedance of the metallurgical joint; applying stress to the metal bond; measuring the resistance of the metal joint while applying the stress to the metal joint to obtain a stressed resistance of the weld; determining a measured difference between the baseline resistance of the metallurgical joint and the stressed resistance of the metallurgical joint; comparing the measured difference to a threshold; Including, When the measured difference exceeds the threshold, the test result is a lack of structural integrity. Claim 9: The method of claim 8 , wherein the metal joint is a weld. Claim 10: The method of claim 8 , wherein the stress is at least one of a mechanical stress, a thermal stress, an acoustic stress, and an electrical stress.

Claims

1. 1. A system for testing the structural integrity of a metallurgical joint, comprising: a stimulation device configured to apply stress to the metallurgical joint; a resistance measuring device configured to measure the resistance of the metallic junction while the metallic junction is stressed by the stimulation device, wherein the resistance is measured using a four-terminal (4T) sensing method comprising a pair of current-carrying electrodes and a pair of voltage-sensing electrodes; a test automation platform (900) comprising a memory (902) storing executable instructions and a processor (901) configured to execute the instructions retrieved from the memory (902); Equipped with The instructions, when executed, cause the processor (901) to determine the structural integrity of the metal joint based on a comparison between the measured resistance and a baseline resistance, the resistance measuring device is configured to measure a complex impedance of the metal joint while the metal joint is subjected to the stress, and the instructions, when executed by the processor, cause the processor (901) to determine the difference between the real component of the measured impedance and the baseline resistance.

2. The system of claim 1 , wherein the stimulation device and the resistance measuring device operate under the control of the test automation platform (900).

3. The system of claim 1 , wherein the stress is at least one of a mechanical stress, a thermal stress, an acoustic stress, and an electrical stress.

4. The system of claim 1 , wherein the stimulation device includes a mechanical actuator (23) configured to apply a mechanical stress to the metallurgical joint.

5. The system of claim 1 , wherein the stimulation device includes a current source configured to apply a pulsed DC current across the metallic junction.

6. The system of claim 1 , wherein the metal joint is a weld.

7. 1. A method for testing the structural integrity of a metallurgical joint, comprising: measuring the resistance of the metallurgical joint to obtain a baseline resistance of the metallurgical joint; applying stress to the metal bond; measuring the resistance of the metallurgical junction by using a four-terminal (4T) sensing method comprising a pair of current-carrying electrodes and a pair of voltage-sensing electrodes while applying the stress to the metallurgical junction to obtain a stressed resistance of the metallurgical junction; determining a measured difference between the baseline resistance of the metallurgical joint and the stressed resistance of the metallurgical joint; comparing the measured difference to a threshold; Including, If the measured difference exceeds the threshold, the test results in a lack of structural integrity. wherein the measured stressed resistance and the baseline resistance are obtained from the real part of the measured complex impedance of the stressed metallurgical joint and the real part of the measured complex impedance of the unstressed metallurgical joint, respectively.

8. The method of claim 7 , wherein the metallurgical joint is a weld.

9. The method of claim 7 , wherein the stress is at least one of a mechanical stress, a thermal stress, an acoustic stress, and an electrical stress.

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