Resistance spot welding quality online detection method and system based on in-situ tempering

Abstract

The invention provides a resistance spot welding quality online detection method and system based on in-situ tempering, and the method comprises the steps: carrying out the resistance spot welding of a plate, collecting and recording a current signal and a dynamic signal in the resistance spot welding process in real time, and extracting the characteristic quantity of the dynamic signal; performing segmentation processing on the dynamic signals according to the relation between the dynamic signals collected in real time and time change; judging a resistance spot welding dynamic signal feature point according to the feature quantity; performing power-on welding at the feature points to obtain resistance statistics; and calculating the diameter of the resistance spot welding nugget through the resistance statistics, thereby realizing the online detection of the resistance spot welding quality. On-line monitoring and real-time feedback in the resistance spot welding process are achieved, on-line monitoring can be conducted on the resistance spot welding quality on the premise that a sample is not damaged, and the welding quality detection efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of resistance spot welding, and in particular to an online detection method and system for resistance spot welding quality based on in-situ tempering. Background Art

[0002] Resistance welding is a common metal welding method widely used in the manufacturing industry. Due to the influence of various factors, the resistance spot welding process is prone to cracks, shrinkage holes, lack of fusion and other defects in the nugget area. The quality of the weld spot directly affects the service life of the welded parts, so defect detection and quality assessment of the weld spot are very important.

[0003] The existing technology mainly involves manual post-weld sampling and offline adjustment, which is unable to realize online non-destructive testing, and has low testing efficiency and high cost.

[0004] Patent document CN115128130A is a system and method for online assessment of resistance spot welding quality based on dynamic resistance signals, which synchronously collects welding current and electrode voltage. Based on the equivalent circuit of the spot welding machine, the dynamic resistance of the AC spot welding process is calculated using Hilbert transform. Eight feature points are extracted from the time domain of the dynamic resistance, and the correlation between the extracted features and the joint strength of the resistance spot welding spot is discussed. Finally, an artificial neural network is used to establish a relationship model between the feature points and the joint strength of the resistance spot welding spot, which is used for the detection of the quality of the resistance spot welding spot.

[0005] However, the black box model in patent document CN115128130A has the disadvantages of poor physical interpretability, unclear meaning of the evaluation results, and inability to give a specific value of the nugget diameter.

[0006] Therefore, there is a need in the market for an online detection method and system for resistance spot welding quality that can monitor the quality of resistance spot welding online without destroying the sample.

[0007] The present invention utilizes electrode displacement signals to extract characteristic quantities and determine characteristic points. Since the material resistivity at the characteristic point is a fixed value for determining the plate, a welding current pulse is applied at the characteristic point, and a sensor is used to collect dynamic signals generated by the pulse to obtain resistance statistics. Finally, the obtained resistance statistics are input into a calculation and analysis module to obtain the diameter of the weld nugget, thereby avoiding the previous method of needing to destroy the sample to measure the diameter of the weld nugget, improving the efficiency of welding quality detection, and providing technical support for real-time feedback and online monitoring of subsequent resistance spot welding processes. Summary of the invention

[0008] In view of the defects in the prior art, the object of the present invention is to provide a method and system for online detection of resistance spot welding quality based on in-situ tempering.

[0009] According to the present invention, a method for online detection of resistance spot welding quality based on in-situ tempering is provided, comprising:

[0010] Step S1: performing resistance spot welding on the plate, and collecting and recording the current signal and dynamic signal during the resistance spot welding process in real time;

[0011] Step S2: According to the relationship between the real-time collected dynamic signal and the time change, the dynamic signal is processed in sections;

[0012] Step S3: extracting the characteristic quantity of the dynamic signal in the post-weld pressure holding stage after segmentation, and determining the characteristic point of the electrode displacement signal in the resistance spot welding dynamic signal according to the characteristic quantity;

[0013] Step S4: performing power-on tempering treatment at the characteristic point, collecting and recording the dynamic signal of the tempering treatment stage in real time, and obtaining dynamic signal statistics;

[0014] Step S5: Calculate the diameter of the resistance spot welding nugget through the resistance statistics to achieve online detection of the resistance spot welding quality.

[0015] Preferably, the dynamic signal includes a dynamic resistance signal and an electrode displacement signal;

[0016] The first-order differential of the electrode displacement signal with respect to time obtains a first-order differential curve of the electrode displacement signal with respect to time, that is, a differential curve of the electrode displacement signal. The first-order differential of the electrode displacement signal with respect to time is the characteristic quantity of the electrode displacement signal.

[0017] Preferably, according to the relationship between the dynamic signal acquired in real time and the time during the resistance spot welding process, the dynamic signal is divided into three stages according to the conduction and termination of the welding current, namely, the pre-welding pre-pressure stage T1, the power-on welding stage T2 and the post-welding pressure holding stage T3.

[0018] Preferably, the characteristic point of the dynamic signal is determined according to the differential curve of the electrode displacement signal, and the characteristic signal threshold ΔS is set. * , the time t corresponding to when the characteristic signal is greater than the threshold for the first time and less than the threshold again * That is the feature point.

[0019] Preferably, step S4 comprises: applying a welding current pulse I with a duration of Δt starting from the characteristic point. h ;

[0020] The obtaining of resistance statistics includes collecting dynamic signals within a time Δt, namely, dynamic resistance signals and electrode displacement signals, and obtaining statistics, wherein the statistics include average values, maximum values, and minimum values ​​of the dynamic resistance signals and electrode displacement signals.

[0021] Preferably, the step S5 comprises: calculating the diameter size of the resistance spot welding nugget using a nugget diameter calculation formula, the calculation formula being as follows:

[0022]

[0023] Among them, ρ h represents the resistivity of the characteristic point, L represents the thickness of the plate, S h Represents the electrode displacement of the characteristic point, R h Indicates the dynamic resistance of the characteristic point.

[0024] According to the present invention, a resistance spot welding quality online detection system based on in-situ tempering is provided, comprising:

[0025] Module M1: Perform resistance spot welding on the plate, collect and record the current signal and dynamic signal in the process of resistance spot welding in real time;

[0026] Module M2: According to the relationship between the real-time collected dynamic signal and the time change, the dynamic signal is processed in segments;

[0027] Module M3: extracting the characteristic quantity of the dynamic signal in the post-weld pressure holding stage after segmentation, and determining the characteristic point of the electrode displacement signal in the resistance spot welding dynamic signal according to the characteristic quantity;

[0028] Module M4: Performing power-on tempering treatment at the characteristic points, collecting and recording dynamic signals in the tempering treatment stage in real time, and obtaining dynamic signal statistics;

[0029] Module M5: The diameter size of the resistance spot welding nugget is calculated by the resistance statistics to realize online detection of the resistance spot welding quality.

[0030] Preferably, the dynamic signal includes a dynamic resistance signal and an electrode displacement signal;

[0031] The first-order differential of the electrode displacement signal with respect to time obtains a first-order differential curve of the electrode displacement signal with respect to time, that is, a differential curve of the electrode displacement signal. The first-order differential of the electrode displacement signal with respect to time is the characteristic quantity of the electrode displacement signal.

[0032] Preferably, according to the relationship between the dynamic signal acquired in real time and the time during the resistance spot welding process, the dynamic signal is divided into three stages according to the conduction and termination of the welding current, namely, the pre-welding pre-pressure stage T1, the power-on welding stage T2 and the post-welding pressure holding stage T3.

[0033] Preferably, the characteristic point of the dynamic signal is determined according to the differential curve of the electrode displacement signal, and the characteristic signal threshold ΔS is set. * , the time t corresponding to when the characteristic signal is greater than the set threshold for the first time and then less than the threshold again *It is the feature point;

[0034] Module M4 includes: applying a welding current pulse I with a duration of Δt starting from the characteristic point h ;

[0035] The obtaining of resistance statistics includes collecting dynamic signals within a time Δt, namely, dynamic resistance signals and electrode displacement signals, and obtaining statistics, wherein the statistics include average values, maximum values, and minimum values ​​of the dynamic resistance signals and electrode displacement signals;

[0036] Module M5 includes: using the calculation formula of the diameter of the weld nugget to calculate the diameter size of the resistance spot welding weld nugget, the calculation formula is as follows:

[0037]

[0038] Among them, ρ h represents the resistivity of the characteristic point, L represents the plate thickness at the characteristic point, S h represents the characteristic point electrode displacement, R h Represents the dynamic resistance of the characteristic point.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The present invention uses the electrode displacement signal measured by the sensor to determine the characteristic point, then applies the welding current pulse at the characteristic point, and finally uses the dynamic signal generated by the welding current pulse to obtain the resistance statistics, and calculates the diameter of the weld nugget of the resistance spot welding according to the resistance statistics, thereby realizing online monitoring and real-time feedback during the resistance spot welding process, and being able to monitor the quality of the resistance spot welding online without destroying the sample, thereby improving the efficiency of welding quality detection;

[0041] 2. The present invention is obtained by using basic physical laws and phenomena and has good explainability;

[0042] 3. The nugget diameter calculated by the present invention for resistance spot welding is a specific value of the nugget diameter, so that the welding quality detection result is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0044] Figure 1 It is a schematic diagram of the working method of the present invention;

[0045] Figure 2 It is a schematic diagram of the system composition block diagram of the present invention;

[0046] Figure 3 It is a schematic diagram of segmented processing of dynamic signals of resistance spot welding in the present invention;

[0047] Figure 4 It is a schematic diagram of the extraction of dynamic signal feature quantities and the determination of feature points in the pressure holding stage of the present invention;

[0048] Figure 5 Schematic diagram of threshold value evaluation of characteristic points in the pressure holding stage of the present invention;

[0049] Figure 6 A schematic diagram of resistance statistics obtained by applying welding current pulses during the pressure holding stage of the present invention;

[0050] Figure 7 It is a scatter plot of the actual value and predicted value of the nugget diameter of Example 1;

[0051] Figure 8 It is a scatter plot of the actual value and predicted value of the nugget diameter of Example 2;

[0052] Table 1 is a recommended table of tempering pulse parameters for different plate combinations of the present invention;

[0053] Among them, the figure markings are: 1. electrode cap, 2. upper electrode rod, 3. lower electrode rod, 4. current sensor, 5. upper electrode dynamic signal sensor, 6. lower electrode dynamic signal sensor, 7. workpiece to be measured, 8. dynamic signal acquisition module, 9. current signal acquisition module, 10. calculation and analysis module. DETAILED DESCRIPTION

[0054] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0055] The present invention utilizes electrode displacement signals to extract characteristic quantities and determine characteristic points. Since the material resistivity at the characteristic point is a fixed value for determining the plate, a welding current pulse is applied at the characteristic point, and a sensor is used to collect dynamic signals generated by the pulse to obtain resistance statistics. Finally, the obtained resistance statistics are input into a calculation and analysis module to obtain the diameter of the weld nugget, thereby avoiding the previous method of needing to destroy the sample to measure the diameter of the weld nugget, improving the efficiency of welding quality detection, and providing technical support for real-time feedback and online monitoring of subsequent resistance spot welding processes.

[0056] Embodiment 1

[0057] According to the present invention, a method for online detection of resistance spot welding quality based on in-situ tempering is provided, such as Figure 1 As shown, including:

[0058] Step S1: resistance spot welding is performed on the plate, and the current signal and dynamic signal during the resistance spot welding process are collected and recorded in real time. By collecting and recording the current signal during the resistance spot welding process in real time, the welding process can be monitored to ensure the consistency of the current during the pressure holding stage. The dynamic signal includes a dynamic resistance signal and an electrode displacement signal.

[0059] Step S2: According to the relationship between the real-time collected dynamic signal and the time change, the dynamic signal is processed in segments. The segment processing can clarify the time corresponding to the characteristic point, which is convenient for re-energizing at the characteristic point. Figure 3 As shown, according to the relationship between the dynamic signal acquired in real time during the resistance spot welding process and the time change, the dynamic signal is divided into three stages according to the conduction and termination of the welding current, namely the pre-welding pre-pressure stage T1, the power-on welding stage T2 and the post-welding pressure-maintaining stage T3. Among them, the pre-welding pre-pressure stage T1 refers to the stage from the electrode closing and clamping the workpiece 4 to be tested until the welding current is turned on, the power-on welding stage T2 refers to the stage from the welding current being turned on to the welding current being turned off, and the post-welding pressure-maintaining stage T3 refers to the stage from the welding current being turned off to the electrode opening.

[0060] Step S3: extract the characteristic quantity of the dynamic signal in the post-weld pressure holding stage after segmentation, and determine the characteristic point of the electrode displacement signal in the resistance spot welding dynamic signal according to the characteristic quantity. Determine the characteristic point of the dynamic signal according to the dynamic signal characteristic quantity extraction schematic diagram, that is, determine the characteristic point of the dynamic signal according to the electrode displacement signal differential curve diagram, wherein the extracted characteristic quantity is at the time t of the post-weld pressure holding stage * Produce changes, such as Figure 5 As shown in the figure, when the differential curve of the electrode displacement signal is greater than the characteristic signal threshold ΔS for the first time in the post-welding pressure holding stage * and is again less than the threshold at the time t * That is, the characteristic point. The characteristic resistivity at the characteristic point is a fixed value. For example, the characteristic signal threshold is set to -2×10 -3 m / s. Extracting the characteristic quantity of the dynamic signal refers to extracting the characteristic quantity of the electrode displacement signal. Specifically, the first-order differential of the electrode displacement signal with respect to time is obtained to obtain a first-order differential curve of the electrode displacement signal with respect to time, such as Figure 4 The electrode displacement signal acquisition curve is first differentiated to obtain the slope of the electrode displacement signal curve, and the slope is the characteristic value.

[0061] Step S4: Perform power-on tempering at the characteristic point, collect and record the dynamic signal of the tempering stage in real time, and obtain dynamic signal statistics. Apply a welding current pulse I with a duration of Δt from the characteristic point as the starting point. h .like Figure 6 As shown in the figure, △t represents the duration of the welding current pulse application, I hRepresents the amplitude of the welding current pulse, R h Indicates the dynamic resistance signal corresponding to the characteristic point, S h The acquisition of resistance statistics includes collecting dynamic signals within a time period of Δt, namely, dynamic resistance signals and electrode displacement signals, and obtaining statistics. The statistics refer to the average values ​​of the dynamic resistance signals and electrode displacement signals, respectively, which are recorded as R A , S A , also includes the maximum and minimum values ​​of the dynamic resistance signal and the electrode displacement signal.

[0062] Step S5: Calculate the diameter of the resistance spot welding nugget through the resistance statistics to achieve online detection of the resistance spot welding quality. Figure 7 As shown. Use the calculation formula of the nugget diameter, the calculation formula is as follows:

[0063]

[0064] Among them, ρ h It represents the resistivity of the characteristic point, which is a fixed value for a certain plate; L represents the plate thickness, which is the sum of the thickness of the resistance spot welding plate, that is, L = h1 + h2; S A Indicates that from time t * The average value of electrode displacement from the beginning to the end of the welding current pulse; R A Indicates that from time t * The average value of dynamic resistance from the beginning to the end of welding current pulse. Substituting the above data into the calculation formula of weld core diameter can obtain the weld core diameter of plate resistance spot welding, and realize the online quality detection of resistance spot welding process.

[0065] Further, the online detection method of resistance spot welding quality based on in-situ tempering of the present invention is specifically described as follows by taking examples:

[0066] like Figure 2 As shown, the welding workpiece 7 used in this example is 2mm 5182 aluminum alloy plate + 2mm 5182 aluminum alloy plate, and the detection steps are as follows:

[0067] First, resistance spot welding is performed on the plate, with a welding current of 8kA, a welding pressure of 3.7kN, and a power-on time of 200ms, and the current signal and dynamic signal during the resistance spot welding process are collected and recorded in real time. The dynamic signal includes a dynamic resistance signal and an electrode displacement signal.

[0068] Then, according to the relationship between the real-time collected dynamic signal and the time change, the dynamic signal is processed in segments. Figure 3As shown, according to the relationship between the dynamic signal acquired in real time during the resistance spot welding process and the time change, the dynamic signal is divided into three stages according to the conduction and termination of the welding current, namely the pre-welding pre-pressure stage T1, the power-on welding stage T2 and the post-welding pressure-maintaining stage T3. Among them, the pre-welding pre-pressure stage T1 refers to the stage from the electrode closing and clamping the workpiece 4 to be tested until the welding current is turned on, the power-on welding stage T2 refers to the stage from the welding current being turned on to the welding current being turned off, and the post-welding pressure-maintaining stage T3 refers to the stage from the welding current being turned off to the electrode opening.

[0069] Next, the characteristic quantity of the dynamic signal is extracted in the post-weld pressure holding stage after segmentation, and the characteristic point of the resistance spot welding dynamic signal is determined according to the characteristic quantity. The characteristic point of the dynamic signal is determined according to the dynamic signal characteristic quantity extraction schematic diagram, that is, the characteristic point of the dynamic signal is determined according to the electrode displacement signal differential curve diagram, and the characteristic signal threshold ΔS* is set. For example, the characteristic signal threshold is set to -2×10 -3 m / s, the time t corresponding to when the characteristic signal is greater than the threshold for the first time and then less than the threshold again * The extracted characteristic quantity is at the time t of the post-welding pressure holding stage. * Produce changes, such as Figure 5 As shown in the figure, when the differential curve of the electrode displacement signal is greater than the characteristic signal threshold ΔS* for the first time and then less than the threshold again in the post-welding pressure holding stage, the moment t * When extracting the characteristic quantity of the dynamic signal, the characteristic quantity of the electrode displacement signal is extracted, that is, the first-order differential of the electrode displacement signal with respect to time, and a first-order differential curve of the electrode displacement signal with respect to time is obtained, such as Figure 4 In this embodiment, the characteristic resistivity of the aluminum alloy at the characteristic point is a fixed value of 3×10 -8 Ω·m.

[0070] Next, the electrical annealing treatment is performed at the characteristic point to obtain resistance statistics. Taking the characteristic point as the starting point, as shown in Table 1, the application time Δt = 20ms, I h =3kA welding current pulse;

[0071] Table 1 Recommended tempering pulse parameters for different plate combinations

[0072]

[0073] like Figure 6 As shown in the figure, △t represents the duration of the welding current pulse application, I h Represents the welding current pulse, R h Indicates the dynamic resistance signal corresponding to the characteristic point, S hThe acquisition of resistance statistics includes collecting dynamic signals within a time period of Δt, namely, dynamic resistance signals and electrode displacement signals, and obtaining statistics. The statistics refer to the average values ​​of the dynamic resistance signals and electrode displacement signals, respectively, and are recorded as R A , S A .

[0074] Finally, the diameter of the resistance spot welding nugget is calculated by the resistance statistics, so as to realize the online detection of the resistance spot welding quality. The calculation formula of the nugget diameter is as follows: Among them, ρ h Represents the characteristic resistivity. In this embodiment, the characteristic resistivity ρ at the characteristic point h A fixed value of 3×10 -8 Ω·m; L represents the plate thickness, which is the sum of the thickness of the aluminum alloy plate, that is, L = h1 + h2 = 2mm + 2mm = 4mm; S A Indicates that from time t * The average value of electrode displacement from the beginning to the end of the welding current pulse; R A Indicates that from time t * The average value of dynamic resistance from the beginning to the end of welding current pulse. Substituting the above data into the calculation formula of weld core diameter can obtain the weld core diameter of plate resistance spot welding.

[0075] like Figure 7 As shown, it is a scatter plot of the actual value and predicted value of the weld core diameter of this embodiment. It can be seen from the figure that there is a good linear correlation between the predicted value and the actual value of the weld core diameter, the determination coefficient is 0.9526, the root mean square error is 0.8mm, the prediction accuracy is high, and the online quality detection of the resistance spot welding process is realized.

[0076] Embodiment 2

[0077] Compared with the first embodiment, the workpieces to be welded in this embodiment are 1mm DP590 steel plate + 1mm DP590 steel plate, the welding current is 9kA, the welding pressure is 3kN, the power-on welding time is 300ms, and the resistance spot welding quality is monitored online in the same steps.

[0078] In this embodiment, the characteristic resistivity ρ of the steel at the characteristic point h A fixed value of 1×10 -7 Ω·m.

[0079] In this embodiment, the characteristic signal threshold ΔS* is set to -3×10 -3 m / s.

[0080] In this embodiment, the characteristic point is taken as the starting point, as shown in Table 1 above, the application time Δt=30ms, I h=4kA current pulse.

[0081] The statistics in this embodiment refer to taking the maximum values ​​of the dynamic resistance signal and the electrode displacement signal, which are respectively recorded as R max , S max .

[0082] This embodiment uses the calculation formula for the diameter of the weld core to calculate the diameter of the weld core: Among them, the characteristic resistivity ρ h A fixed value of 1×10 -7 Ω·m; L is the sum of the thickness of the steel plate, that is, L=h1+h2=1mm+1mm=2mm; S max From time t * The maximum value of electrode displacement from the beginning to the end of the welding current pulse; R h From time t * The maximum value of the dynamic resistance from the beginning to the end of the welding current pulse.

[0083] like Figure 8 As shown, it is a scatter plot of the actual value and predicted value of the weld core diameter of this embodiment. It can be seen from the figure that there is a good linear correlation between the predicted value and the actual value of the weld core diameter, the determination coefficient is 0.9702, the root mean square error is 0.5mm, the prediction accuracy is high, and the online quality detection of the resistance spot welding process is realized.

[0084] Embodiment 3

[0085] The present invention also provides an online detection system for resistance spot welding quality based on in-situ tempering. A person skilled in the art can implement the online detection system for resistance spot welding quality based on in-situ tempering by executing the step flow of the online detection method for resistance spot welding quality based on in-situ tempering, that is, the online detection method for resistance spot welding quality based on in-situ tempering can be understood as a preferred implementation of the online detection system for resistance spot welding quality based on in-situ tempering.

[0086] According to the present invention, a resistance spot welding quality online detection system based on in-situ tempering is provided. Figure 2 As shown, including:

[0087] Module M1: Perform resistance spot welding on the plate, collect and record the current signal and dynamic signal in the resistance spot welding process in real time. This module M1 includes Figure 2 The current signal acquisition module and the dynamic signal acquisition module shown in the figure, wherein the current signal acquisition module is connected to the current sensor arranged on the electrode and collects the current signal, and the dynamic signal acquisition module is respectively connected to a pair of dynamic signal sensors installed on the two electrodes to collect the dynamic signal during the welding process. The dynamic signal includes a dynamic resistance signal and an electrode displacement signal.

[0088] Module M2: According to the relationship between the real-time collected dynamic signal and the time change, the dynamic signal is processed in segments. According to the relationship between the dynamic signal collected in real time and the time change during the resistance spot welding process, the dynamic signal is divided into three stages based on the conduction and termination of the welding current, namely the pre-welding pre-pressure stage T1, the power-on welding stage T2, and the post-welding pressure holding stage T3.

[0089] Module M3: Extract the characteristic value of the dynamic signal in the post-weld pressure holding stage after segmentation, and determine the characteristic point of the electrode displacement signal in the resistance spot welding dynamic signal according to the characteristic value. Determine the characteristic point of the dynamic signal according to the differential curve of the electrode displacement signal. Set the characteristic signal threshold ΔS * , when the electrode displacement signal differential curve exceeds the characteristic signal threshold ΔS for the first time in the post-weld pressure holding stage * and is again less than the threshold at the time t * It is a characteristic point. The characteristic resistivity at the characteristic point is a fixed value. Extracting the characteristic quantity of the dynamic signal refers to extracting the characteristic quantity of the electrode displacement signal. Specifically, the first-order differential of the electrode displacement signal with respect to time is obtained, and the first-order differential of the electrode displacement signal with respect to time is the characteristic quantity of the electrode displacement signal.

[0090] Module M4: Perform power-on tempering treatment at the characteristic point, collect and record the dynamic signals of the tempering treatment stage in real time, and obtain dynamic signal statistics. Module M4 includes: applying a welding current pulse I with a duration of Δt starting from the characteristic point h The acquisition of resistance statistics includes collecting dynamic signals within a time Δt, namely, dynamic resistance signals and electrode displacement signals, and obtaining statistics. The statistics refer to the average values ​​of the dynamic resistance signals and electrode displacement signals, which are recorded as R A , S A , also includes the maximum and minimum values ​​of the dynamic resistance signal and the electrode displacement signal.

[0091] Module M5: The diameter size of the resistance spot welding nugget is calculated by the resistance statistics to realize the online detection of the resistance spot welding quality. Module M5 includes: calculating the diameter size of the resistance spot welding nugget using the nugget diameter calculation formula, and the calculation formula is as follows:

[0092]

[0093] Among them, ρ h represents the resistivity of the characteristic point, L represents the plate thickness at the characteristic point, S h represents the characteristic point electrode displacement, R h Represents the dynamic resistance of the characteristic point.

[0094] The module M5 is Figure 2The calculation and analysis module in the welding controller inputs the obtained resistance statistics into the calculation and analysis module for calculation.

[0095] The online detection system of resistance spot welding quality based on in-situ tempering also includes resistance spot welding quality detection devices, such as Figure 2 As shown, the device includes an electrode cap 1, an upper electrode rod 2, a lower electrode rod 3, a current sensor 4, an upper electrode dynamic signal sensor 5, a lower electrode dynamic signal sensor 6, and a workpiece to be measured 7. An upper electrode dynamic signal sensor 5 is installed at one end of the upper electrode rod 2, and an electrode cap 1 is installed at the other end. Similarly, a lower electrode dynamic signal sensor 6 is installed at one end of the lower electrode rod 3, and an electrode cap 1 is installed at the other end. The workpiece to be measured 7 is placed between the two electrode caps for detection, and the current sensor 4 is installed on the lower electrode rod 3.

[0096] The dynamic signal acquisition module is connected to the upper electrode dynamic signal sensor 5 and the lower electrode dynamic signal sensor 6, and the current signal acquisition module is connected to the current sensor 4. The collected dynamic signals and current signals are input to the calculation and analysis module for calculation and analysis.

[0097] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0098] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for online detection of resistance spot welding quality based on in-situ tempering, characterized in that: include: Step S1: performing resistance spot welding on the plate, and collecting and recording the current signal and dynamic signal during the resistance spot welding process in real time; Step S2: According to the relationship between the real-time collected dynamic signal and the time change, the dynamic signal is processed in sections; Step S3: extracting the characteristic quantity of the dynamic signal in the post-weld pressure holding stage after segmentation, and determining the characteristic point of the electrode displacement signal in the resistance spot welding dynamic signal according to the characteristic quantity; Step S4: performing power-on tempering treatment at the characteristic point, collecting and recording the dynamic signal of the tempering treatment stage in real time, and obtaining dynamic signal statistics; Step S5: Calculate the diameter of the resistance spot welding nugget through the resistance statistics to achieve online detection of the resistance spot welding quality.

2. The method for online detection of resistance spot welding quality based on in-situ tempering according to claim 1 is characterized in that: The dynamic signal includes a dynamic resistance signal and an electrode displacement signal; The extracting the characteristic quantity of the dynamic signal refers to extracting the characteristic quantity of the electrode displacement signal; The first-order differential of the electrode displacement signal with respect to time obtains a first-order differential curve of the electrode displacement signal with respect to time, that is, a differential curve of the electrode displacement signal. The first-order differential of the electrode displacement signal with respect to time is the characteristic quantity of the electrode displacement signal.

3. The online detection method for resistance spot welding quality based on in-situ tempering according to claim 1 is characterized in that: According to the relationship between the dynamic signal acquired in real time and the time change during the resistance spot welding process, the dynamic signal is divided into three stages according to the conduction and termination of the welding current, namely the pre-welding pre-pressure stage T1, the power-on welding stage T2 and the post-welding pressure holding stage T3.

4. The method for online detection of resistance spot welding quality based on in-situ tempering according to claim 2 is characterized in that: Determine the characteristic points of the dynamic signal based on the differential curve of the electrode displacement signal and set the characteristic signal threshold ΔS * , the time t corresponding to when the characteristic signal is greater than the set threshold for the first time and then less than the threshold again * That is the feature point.

5. The method for online detection of resistance spot welding quality based on in-situ tempering according to claim 1, characterized in that: Step S4 includes: starting from the characteristic point, applying a welding current pulse I with a duration of Δt h； The obtaining of resistance statistics includes collecting dynamic signals within a time Δt, namely, dynamic resistance signals and electrode displacement signals, and obtaining statistics, wherein the statistics include average values, maximum values, and minimum values ​​of the dynamic resistance signals and electrode displacement signals.

6. The method for online detection of resistance spot welding quality based on in-situ tempering according to claim 1, characterized in that: The step S5 includes: calculating the diameter of the resistance spot welding nugget using a nugget diameter calculation formula, the calculation formula is as follows: Among them, ρ h represents the resistivity of the characteristic point, L represents the thickness of the plate, S h represents the characteristic point electrode displacement, R h Represents the dynamic resistance of the characteristic point.

7. An online detection system for resistance spot welding quality based on in-situ tempering, characterized in that: include: Module M1: Perform resistance spot welding on the plate, collect and record the current signal and dynamic signal in the process of resistance spot welding in real time; Module M2: According to the relationship between the real-time collected dynamic signal and the time change, the dynamic signal is processed in segments; Module M3: extracting the characteristic quantity of the dynamic signal in the post-weld pressure holding stage after segmentation, and determining the characteristic point of the electrode displacement signal in the resistance spot welding dynamic signal according to the characteristic quantity; Module M4: Performing power-on tempering treatment at the characteristic points, collecting and recording dynamic signals in the tempering treatment stage in real time, and obtaining dynamic signal statistics; Module M5: The diameter size of the resistance spot welding nugget is calculated by the resistance statistics to realize online detection of the resistance spot welding quality.

8. The online detection system for resistance spot welding quality based on in-situ tempering according to claim 7 is characterized in that: The dynamic signal includes a dynamic resistance signal and an electrode displacement signal; Extracting the characteristic quantity of the dynamic signal refers to extracting the characteristic quantity of the electrode displacement signal; The first-order differential of the electrode displacement signal with respect to time obtains a first-order differential curve of the electrode displacement signal with respect to time, that is, a differential curve of the electrode displacement signal. The first-order differential of the electrode displacement signal with respect to time is the characteristic quantity of the electrode displacement signal.

9. The online detection system for resistance spot welding quality based on in-situ tempering according to claim 7 is characterized in that: According to the relationship between the dynamic signal acquired in real time and the time change during the resistance spot welding process, the dynamic signal is divided into three stages according to the conduction and termination of the welding current, namely the pre-welding pre-pressure stage T1, the power-on welding stage T2 and the post-welding pressure holding stage T3.

10. The online detection system for resistance spot welding quality based on in-situ tempering according to claim 8, characterized in that: Determine the characteristic points of the dynamic signal based on the differential curve of the electrode displacement signal and set the characteristic signal threshold ΔS * , the time t corresponding to when the characteristic signal is greater than the set threshold for the first time and then less than the threshold again * It is the feature point; Module M4 includes: starting from the characteristic point, applying a welding current pulse I with a duration of Δt h； The obtaining of resistance statistics includes collecting dynamic signals within a time Δt, namely, dynamic resistance signals and electrode displacement signals, and obtaining statistics, wherein the statistics include average values, maximum values, and minimum values ​​of the dynamic resistance signals and electrode displacement signals; Module M5 includes: using the calculation formula of the diameter of the weld nugget to calculate the diameter size of the resistance spot welding weld nugget, the calculation formula is as follows: Among them, ρ h represents the resistivity of the characteristic point, L represents the plate thickness at the characteristic point, S h represents the characteristic point electrode displacement, R h Represents the dynamic resistance of the characteristic point.

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