CN115070251B - Friction stir welding surface welding quality detection method - Google Patents
Friction stir welding surface welding quality detection method Download PDFInfo
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- CN115070251B CN115070251B CN202210742311.XA CN202210742311A CN115070251B CN 115070251 B CN115070251 B CN 115070251B CN 202210742311 A CN202210742311 A CN 202210742311A CN 115070251 B CN115070251 B CN 115070251B
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- 238000003466 welding Methods 0.000 title claims abstract description 98
- 238000003756 stirring Methods 0.000 title claims abstract description 30
- 238000001514 detection method Methods 0.000 title claims abstract description 19
- 238000000034 method Methods 0.000 claims description 32
- 230000007547 defect Effects 0.000 claims description 8
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K31/00—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups
- B23K31/12—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups relating to investigating the properties, e.g. the weldability, of materials
- B23K31/125—Weld quality monitoring
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/12—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding
- B23K20/122—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding using a non-consumable tool, e.g. friction stir welding
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Abstract
The invention discloses a friction stir welding surface welding quality detection method, which comprises the following steps: (1) acquiring continuous weld surface depth images, intercepting the weld surface depth images with proper step length, dividing the intercepted weld surface depth images into areas to obtain a front side reference area, a thinning area and a rear side reference area, judging whether the flatness of the front side reference area is smaller than a threshold value, if so, taking the front side reference area height as the latest reference height, if not, judging whether the flatness of the rear side reference area is smaller than the threshold value, if so, taking the rear side reference area height as the latest reference height, if not, taking the reference height of the front section depth image as the latest reference height, and taking the latest reference height as the difference between the average height of the thinning area at the moment and the latest reference height to obtain the thinning amount.
Description
Technical Field
The invention relates to the technical field of friction stir welding seam detection, in particular to a method for detecting welding quality of a friction stir welding surface.
Background
The friction stir welding technology proposed by the British welding technology research in 1991 is a typical novel green welding technology, smoke dust and arc light are not generated in the welding process, gas protection and filling of other materials are not needed, and the friction stir welding technology has great advantages especially when aiming at aluminum alloy welding, so that the friction stir welding technology is widely applied to manufacturing various aluminum alloy structural members in the fields of aerospace, automobiles, ships, rail transit vehicles and the like.
The working principle of friction stir welding is as follows: the stirring head rotating at high speed is pricked into a workpiece, friction heat is generated at a contact position, so that a plastic softening layer is formed on metal, upsetting force is applied to a welding material through a shaft shoulder of a stirring pin, and therefore the rear material is extruded to fill a cavity, but in the welding process, the pressing amount, the rotating speed of a main shaft, the feeding speed and the like usually need to be regulated and controlled manually, and welding defects, overlarge thinning amount, flash and the like can occur at a welding seam. At present, defects such as welded grooves are detected mainly through a manual identification mode. In the aspect of detecting the thinning amount, after welding is finished, the welding material is detached from the tool, and then the acoustic thickness gauge is used for detecting the thickness of the welding line, so that labor is consumed, and if a problem is found, the tool is very difficult to reset. The flash is not effectively detected, but is directly removed by adopting a mode of manually shoveling or post-welding milling by a pneumatic flat shovel. The friction stir welding speed is generally 0.4m/min to 2m/min, belongs to automatic high-speed welding, is difficult to adapt to the speed range by only adopting a manual detection mode for the final welding quality, and limits the production efficiency to a great extent.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method for detecting the welding quality of a friction stir welding surface.
In order to achieve the above object, an embodiment of the present invention provides the following technical solution:
a friction stir welding surface welding quality detection method comprises the following steps:
(1) Acquiring continuous weld surface depth images;
(2) Intercepting a welding seam surface depth image with a proper step length, dividing the intercepted welding seam surface depth image into areas, and obtaining a front side reference area, a thinning area and a rear side reference area;
(3) Judging whether the flatness of the front side reference area is smaller than a threshold value, if so, taking the front side reference area height at the moment as the latest reference height; if not, judging whether the flatness of the rear side reference area is smaller than a threshold value, and if so, taking the height of the rear side reference area at the moment as the latest reference height; if not, taking the reference height of the previous section of depth image as the latest reference height;
(4) The latest reference height is different from the average height of the thinning area at this time to obtain the thinning amount.
As a further improvement of the present invention, in the step (3), if the flatness of the front reference area is smaller than the threshold value, a fitting plane of the front reference area is obtained by using a least square method, and a normal vector of the fitting plane is rotated to a direction parallel to the depth direction.
As a further improvement of the present invention, in the step (3), if the flatness of the rear reference area is smaller than the threshold value, a fitting plane of the rear reference area is obtained by using a least square method, and a normal vector of the fitting plane is rotated to a direction parallel to the depth direction.
As a further improvement of the invention, the method also comprises the steps of identifying the groove defect of the thinning area, judging whether the groove exists or not, and accumulating the lengths of the grooves if the groove exists; if not, the groove is ended, and the length information is returned.
As a further improvement of the present invention, whether or not a groove is present is determined by calculating the degree of fluctuation of the weld surface depth image of the thinned region or comparing the depth of the weld surface depth image of the thinned region with a reference height.
The invention further improves the method, which comprises the steps of dividing the intercepted depth image of the weld surface into a front-side flash area and a rear-side flash area, wherein the front-side flash area is positioned between a front-side reference area and a thinning area, the rear-side flash area is positioned between the rear-side reference area and the thinning area, and whether the front-side flash area and the rear-side flash area have flash or not is respectively judged.
As a further improvement of the present invention, the flatness of the front side reference area and the rear side reference area is judged, and the flash reference height is obtained, and whether the difference between the maximum height value of the front side flash area and the flash reference height is greater than a threshold value or not and whether the difference between the maximum height value of the rear side flash area and the flash reference height is greater than a threshold value or not are respectively judged;
if the difference between the maximum height value of the front-side flash area and the flash reference height is larger than a threshold value, binarizing the front-side flash area to obtain a front-side flash width, calculating the front-side flash height, judging whether at least one of the front-side flash width and the front-side flash height is larger than a corresponding threshold value, if so, increasing the front-side flash by one step length, and recording the front-side flash area width and the front-side flash area height;
if the difference between the maximum depth value of the front-side flash area and the flash reference height is not greater than the threshold value, the flash judgment of the front-side flash area is finished;
if the difference between the maximum height value of the rear burr area and the burr standard height is larger than a threshold value, binarizing the rear burr area to obtain rear burr width, calculating rear burr height, judging whether at least one of the rear burr width and the rear burr height is larger than a corresponding threshold value, if so, adding a step length to the rear burr, and recording the rear burr area width and the rear burr area height;
if the difference between the maximum height value of the rear burr region and the burr reference height is not greater than the threshold value, the burr determination of the rear burr region is ended.
As a further improvement of the present invention, binarizing is performed on the front-side flash region, and the minimum bounding rectangle of the obtained region of interest is fitted, the width of the minimum bounding rectangle is taken as the front-side flash width, and the difference between the maximum height value of the front-side flash region and the flash reference height is calculated as the front-side flash height, respectively.
As a further improvement of the present invention, binarizing is performed on the rear-side flash region, and the minimum bounding rectangle of the obtained region of interest is fitted, the width of the minimum bounding rectangle is taken as the rear-side flash width, and the difference between the maximum height value of the rear-side flash region and the flash reference height is calculated as the rear-side flash height, respectively.
As a further improvement of the present invention, when the flatness of only the front side reference area is smaller than the threshold value, the average height of the front side reference area is calculated as the burr reference height; when the flatness of the rear side reference area is smaller than the threshold value, calculating the average height of the rear side reference area as the flash reference height; when the flatness of the front side reference area and the flatness of the rear side reference area are smaller than the threshold value, calculating the average heights of the front side reference area and the rear side reference area, and taking the average heights as the flash reference heights; and when the flatness of the front side reference area and the flatness of the rear side reference area are both larger than the threshold value, taking the latest reference height calculated before as the flash reference height.
The beneficial effects of the invention are as follows:
according to the invention, in the friction stir welding process, the depth image of the surface of the friction stir welding seam is obtained through laser scanning, the thinning amount, the surface groove and the flash of the friction stir welding seam with the surface appearance of a complex curved surface can be detected on-line under the condition that the welding piece is slightly deformed due to stress and heating, the automation degree is high, the reference height can be updated in real time when the phenomenon of plate upwarp and local inclination occurs to the welding object which is deformed due to stress and heating, particularly to the thin plate welding piece, the calculation of the reference height of the thinning beam is avoided, the detection result of the thinning amount is relatively accurate, meanwhile, the judgment of the groove and the flash is fast and accurate, the reference is provided for the later processing through feeding back the relevant accurate welding quality information, the production efficiency and the welding quality can be further improved, the welding speed of 0.4m/min to 2m/min can be adapted, and the effect of real-time detection is achieved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings may be obtained according to the drawings without inventive effort to those skilled in the art.
FIG. 1 is a schematic diagram of a detection system according to a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram of the structure of a line laser scanner, machine tool C-axis and X-axis grating mounting according to a preferred embodiment of the present invention;
FIG. 3 is a cross-sectional view of a friction stir weld of a preferred embodiment of the present invention;
FIG. 4 is a flow chart of the detection of thinning and trench defects according to a preferred embodiment of the present invention:
FIG. 5 is a flow chart of a determination of flash on both sides of a weld in accordance with a preferred embodiment of the present invention;
FIG. 6 is a schematic view showing the raising of the judgment reference when the heights of the two side references are different in the preferred embodiment of the present invention;
in the figure: 1. the device comprises an industrial personal computer, 2, an Ethernet switch, 3, a controller, 4, a PLC,5, a line laser scanner, 501, line laser, 6, a numerical control machine tool, 601, a C axis, 602, a stirring needle, 7, an X axis grating, 701, an X axis direction incremental grating scale, 702, an X axis direction reading head, 801, a Y axis direction incremental grating scale, 802, a Y axis direction reading head, 9, an exclusive-or operation and amplification circuit, 10, a welding seam, 11 and an air nozzle.
Detailed Description
In order to make the technical solution of the present invention better understood by those skilled in the art, the technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
Fig. 1 is a block diagram of a detection system for detecting welding quality, which comprises an industrial personal computer 1, an ethernet switch 2, a controller 3, a PLC4, a line laser scanner 5, and a numerical control machine 6. The industrial personal computer 1 is connected with the Ethernet switch 2, the Ethernet switch 2 is respectively connected with the controller 3 and the PLC4, and the controller 3 is connected with the line laser scanner 5. If the line laser scanner 5 adopts an encoder triggering mode to collect data, the line laser scanner further comprises an X-axis grating 7 and a Y-axis grating 8, wherein the X-axis grating 7 and the Y-axis grating 8 are respectively arranged in the X-axis direction and the Y-axis direction of the numerical control machine tool 6, pulse signals are generated when the welding direction is along the X-axis direction or the Y-axis direction, and the combined pulse signals are connected to the controller 3 after being combined through the exclusive OR operation and amplification circuit 9. The X-axis grating 7 includes an X-axis direction incremental grating scale 701 and an X-axis direction reading head 702, and the Y-axis grating 8 includes a Y-axis direction incremental grating scale 801 and a Y-axis direction reading head 802. It will be appreciated that the line laser scanner 5 may also perform data acquisition in a continuous triggering manner matched to the welding speed, i.e. the welding speed is required to be matched to the scanning frequency for scanning at a fixed frequency, and the X-axis grating 7 and the Y-axis grating 8 are not required to be provided.
Referring to fig. 2, the line laser scanner 5 is installed at the rear side of the C-axis 601 of the numerically controlled machine tool 6 in the movement direction, so as to ensure safety, reduce the interference of flying chips during welding, and simultaneously make the line laser 501 of the line laser scanner 5 irradiate on the friction stir welding seam 10 during welding, and the welding direction is vertically bisected to the line laser 501. The X-axis direction incremental grating scale 701 and the X-axis direction reading head 702 of the X-axis grating 7 are respectively mounted on the stage and the base of the numerical control machine 6, and the Y-axis direction incremental grating scale 801 and the Y-axis direction reading head 802 of the Y-axis grating 8 are respectively mounted on the stage and the base of the numerical control machine 6. The X-axis incremental grating ruler 701 and the Y-axis incremental grating ruler 801 remain stationary, and the X-axis directional reading head 702 and the Y-axis directional reading head 802 can move, so that a pulse signal is generated by the relative movement, and is used as a trigger signal for the line laser scanner 5 in the welding process.
In order to continuously jet air in the welding process so as to remove flying chips generated in the welding process, an air jet 11 is arranged beside a stirring needle 602 of the C-axis 601 so as to reduce interference of the flying chips on the depth image.
Because a certain distance is reserved between the line laser 501 of the line laser scanner 5 and the stirring pin 602, and the measuring range of the laser is limited, in order to ensure that the acquisition of the depth image of the welding seam surface is not interfered by the rotation of the C axis 601 of the numerical control machine tool 6 in the welding process, the embodiment of the invention mainly aims at detecting the linear welding seam. During the welding process, the line laser scanner 5 moves in the weld direction at the same time, and continuously acquires depth information of the weld surface.
The welding motion starts, the X-axis grating 7 and the Y-axis grating 8 generate pulses, the pulses are input to the controller 3, the controller 3 receives the pulses and counts, the control line laser scanner 5 scans the welding line 10 to obtain images, and the Ethernet switch 2 can connect the controller 3, the industrial personal computer 1 and the PLC4 for communication.
In order to quickly and relatively accurately realize quick detection of the surface welding quality, the invention preferably uses a line laser scanning mode to acquire a surface depth image of the friction stir welding seam 10, and performs calculation of thinning amount, and feature extraction of defects such as grooves, flash and the like based on the image.
The embodiment of the invention discloses a friction stir welding surface welding quality detection method, which comprises the following steps:
(1) Acquiring continuous weld surface depth images;
(2) Intercepting a welding seam surface depth image at a proper step length;
(3) Dividing the intercepted depth image of the surface of the welding seam into areas to obtain a front side reference area, a thinning area and a rear side reference area;
(4) Calculating the flatness of the front side reference area and the rear side reference area, judging whether the flatness of the front side reference area is smaller than a threshold value, and if yes, taking the height of the front side reference area at the moment as the latest reference height; if not, judging whether the flatness of the rear side reference area is smaller than a threshold value, and if so, taking the height of the rear side reference area at the moment as the latest reference height; if not, taking the reference height of the previous section of depth image as the latest reference height;
(5) The latest reference height is different from the average height of the thinning area at this time to obtain the thinning amount.
Preferably, the weld surface depth image is truncated at equal intervals in a suitable step length, which is the length along the length of the weld. The step length is a fixed value which is set and can be 1mm, and when the welding line is thinner and shorter, the step length can take a value smaller than 1 mm; when the weld is wider and longer, it can take a value greater than 1 mm. The scanning depth image and the intercepting image processing are carried out simultaneously, when the scanned image can reach the step length, the intercepting image can be intercepted for processing, when the intercepting image processing is completed, the newly scanned image is waited for, and the newly scanned image can be processed immediately as long as the newly scanned image reaches the step length.
The thinning amount is one of important detection indexes, and as soon as the thinning amount is large, it is indicated that a certain part of a welding piece becomes very thin, and the welding quality and the rigidity of materials are affected by the thinning, so that the thinning amount needs to be detected. Because the plate is deformed in the process of welding the thin plate, the reference is changed, the depth image of the surface of the welding seam is cut into small sections at equal intervals according to the step length, the reference and the thinning area are respectively differed in the small sections, the thinning amount of the small sections is obtained, and then each thinning amount is recorded in sequence, so that the thinning amount of one welding seam is obtained.
The cross section of the weld 10 is shown in fig. 3. The amount of thinning per step and the method of detecting the trench are described below as shown in fig. 4.
First, the flatness of the front side reference region and the rear side reference region is determined. The images on two sides of the depth image of each step length are selected to be respectively used as a front reference area and a rear reference area, the two sides refer to parts at the connection positions of the two plates respectively, the standard deviation of pixel values of the front reference area and the rear reference area is calculated respectively, and if the standard deviation of the pixel values is smaller, the relative flatness is indicated. And if the flatness of the front side reference area is smaller than the threshold value, obtaining a fitting plane of the front side reference area by adopting a least square method, and rotating the normal vector of the fitting plane to a direction parallel to the depth direction. That is, a fixed column number area in the front edge of the depth image is selected as a reference area, a plane is fitted by using a least square method to the area, a normal vector of the plane can be obtained, and then the normal vector is rotated to a direction parallel to the depth direction, which means that the reference is horizontal, the depth image of the step is not inclined any more, and the depth direction is perpendicular to the reference plane. The pixel average value of the depth image of the front-side reference region is obtained as the front-side reference region height. The front side reference area height at this time is used as the latest reference height, and the reference height is different from the average height of the thinning area as the thinning amount value. If the flatness of the front side reference area is not smaller than the threshold value, judging whether the flatness of the rear side reference area is smaller than the threshold value, and if the flatness of the rear side reference area is smaller than the threshold value, obtaining a fitting plane of the rear side reference area by adopting a least square method, and rotating a normal vector of the fitting plane to a direction parallel to the depth direction. That is, a fixed column number area in the rear side edge of the depth image is selected as a reference area, a plane is fitted by the area by adopting a least square method, a normal vector of the plane can be obtained, and then the normal vector is rotated to a direction parallel to a depth direction, which means that the reference is horizontal, the depth image of the step is not inclined any more, and the depth direction is perpendicular to the reference plane. The pixel average value of the depth image of the rear side reference region is obtained as the rear side reference region height. The reference height is set to the latest reference height, and the difference between the reference height and the average height of the thinned region is set to the thinned value. If the flatness of the front side reference area and the flatness of the rear side reference area are both larger than the flatness threshold value, the reference height of the depth image of the surface of the welding seam of the previous section is used as the reference height of the calculated thinning amount. The average height of the thinned region refers to the pixel average of the thinned region. By the method, the influence of weldment deformation on calculation of the thinning amount can be reduced to a great extent, and the corresponding relation between the thinning amount and the welding stroke can be obtained. Through showing the reduction of welding seam 10 along length direction, can obtain the corresponding position of this reduction moreover, whether the value of knowing the reduction is too big directly perceivedly, if the reduction is too big indicates that welded volume of pushing down is too big, through the welding volume of pushing down to this position in time adjustment, avoid influencing welding quality.
If a groove exists at the welding line, the welding piece is easy to corrode or break, so that the method further comprises identifying the groove defect of the thinning area, judging whether the groove exists or not, and if yes, accumulating the lengths of the grooves; if not, the groove is ended, and the length information is returned. In detecting the groove on the surface of the weld joint, whether the groove exists or not is judged by calculating the fluctuation degree of the depth image of the thinned area or comparing the depth of the thinned area with the reference height. Wherein calculating the degree of fluctuation of the thinned region depth image refers to: if the welding quality is good, the thinned area is relatively flat, the standard deviation of the depth value of the thinned area is taken as a judgment basis, and if the standard deviation is large, the uneven thinned area is indicated to have grooves. Comparing the depth of the thinned region with a reference height means: the pixel value in the depth image may also be called a depth value, that is, if there is a trench, the depth value in the thinned region image may be smaller, and the depth value is compared with the pixel average value of the "reference" region (the region of the image with a fixed column number of the edge of the set depth image), that is, the reference height, and if the two values are greatly different, the trench is indicated. If the groove exists, the groove is a continuous section, and the detection is calculated by adopting a smaller step length, so that the method is equivalent to cutting the groove of one section into a plurality of small sections in sequence along the length direction, if the groove exists, the situation that a plurality of small sections are provided with grooves continuously occurs, and the lengths of the small sections are accumulated in sequence, namely the lengths of the grooves.
The method comprises the steps of dividing the intercepted depth image of the welding seam surface into a front-side flash area and a rear-side flash area, wherein the front-side flash area is positioned between the front-side reference area and the thinning area, the rear-side flash area is positioned between the rear-side reference area and the thinning area, and whether the front-side flash area and the rear-side flash area have flash or not is respectively judged. FIG. 5 is a flowchart of a determination of flash on both sides of a weld using the same step size image as the calculated amount of thinning. The two sides of the welding seam are provided with burrs, the front side burrs and the rear side burrs are separately detected, the detection processes of the front side burrs and the rear side burrs are independent, and the adopted detection steps are the same.
Firstly, judging the flatness of a front side reference area and a rear side reference area, and obtaining a flash reference height, and respectively judging whether the difference between the maximum height value of the front side flash area and the flash reference height is larger than a threshold value and whether the difference between the maximum height value of the rear side flash area and the flash reference height is larger than the threshold value;
if the difference between the maximum height value of the front-side flash area and the flash reference height is larger than a threshold value, binarizing the front-side flash area to obtain a front-side flash width, calculating the front-side flash height, judging whether at least one of the front-side flash width and the front-side flash height is larger than a corresponding threshold value, if so, increasing the front-side flash by one step length, and recording the front-side flash area width and the front-side flash area height;
if the maximum height value of the front-side flash area and the flash reference height are not greater than the height threshold value, the flash judgment of the front-side flash area is finished;
if the difference between the maximum height value of the rear burr area and the burr standard height is larger than a threshold value, binarizing the rear burr area to obtain rear burr width, calculating rear burr height, judging whether at least one of the rear burr width and the rear burr height is larger than a corresponding threshold value, if so, adding a step length to the rear burr, and recording the rear burr area width and the rear burr area height;
if the difference between the maximum height value of the rear burr region and the burr reference height is not greater than the threshold value, the burr determination of the rear burr region is ended.
After the flatness of the front side reference area and the rear side reference area is judged, the flatness is judged in four cases, and then the flash reference height t is obtained. When the flatness of the front side reference area is smaller than the threshold value, calculating the average height of the front side reference area as the flash reference height t; when the flatness of the rear side reference area is smaller than the threshold value, calculating the average height of the rear side reference area as the flash reference height t; when the flatness of the front side reference area and the flatness of the rear side reference area are smaller than the threshold value, calculating the average heights of the front side reference area and the rear side reference area, and taking the average heights as the flash reference height t; when the flatness of the front side reference area and the flatness of the rear side reference area are both larger than the threshold value, the latest reference height calculated before is taken as the flash reference height t, and the latest reference height is selected as the reference height of the previous section of image, namely, when the references at the moment are shielded, the reference height of the previous section of image is closest to the position of the depth image at the moment on the welding line, so that the deformation interference can be reduced to the greatest extent. Wherein the average height of the front side reference region refers to the pixel average value of the front side reference region, and the average height of the rear side reference region refers to the pixel average value of the rear side reference region. The average heights of the front and rear reference regions refer to the pixel average values of the front and rear reference regions.
A smaller threshold m is set.
If the maximum height t1 of the front burr area is greater than the threshold value m and the heights of the two plates are not identical, the heights of the two plates are different, namely, the burrs are misplaced, and if the average value of the two sides, namely, t, is taken, erroneous judgment of the burrs is caused by the misplacement, namely, the judgment of the burrs which are not originally the burrs is easily judged as the burrs, so that the t is increased by one epsilon, and the judgment standard is raised, as shown in fig. 6, so that the erroneous judgment is avoided. The front-side flash region is binarized using a threshold section [ t+ε, t1] larger than the flash reference height t, and a minimum bounding rectangle of the obtained region of interest (ROI) is fitted, the width of the minimum bounding rectangle is taken as the width d1 of the front-side flash region, and the difference between the maximum height value t1 of the front-side flash region and the flash reference height t is calculated as the front-side flash height h1. If the width D1 exceeds the threshold value D1 or the height H1 exceeds the threshold value H1, it is determined that the burr exists, the burr length information of the front burr area is increased by one step, and the width D1 and the height H1 of the front burr area are recorded. If the difference between the maximum height value t1 of the front burr region and the burr reference height is not greater than the threshold value m, it is determined that the burr of the front burr region is finished.
If the maximum height t2 of the rear flashing area and the reference height t of the flashing are greater than the threshold value m, when the heights of the two plates are inconsistent, the heights of the two references are different, namely the two references are in a staggered state, in this case, if the average value of the two sides, namely t, is taken, the false judgment of the flashing is caused by the staggered side, so that the t is increased by epsilon, the judgment reference is raised, as shown in fig. 6, and the false judgment is avoided. The rear-side flash region is binarized by using a threshold section [ t+epsilon, t2] larger than the flash reference height t, a minimum circumscribed rectangle of the obtained region of interest (ROI) is fitted, the width of the minimum circumscribed rectangle is taken as the width d2 of the rear-side flash region, and the difference between the maximum height value t2 of the rear-side flash region and the flash reference height t is calculated as the height h2 of the rear-side flash region. If the width D2 exceeds the threshold D2 or the height H2 exceeds the threshold H2, it is determined that the burr exists, the length information of the rear burr area is increased by one step, and the width D2 and the height H2 of the rear burr area are recorded. If the difference between the maximum height value t2 of the rear burr area and the burr reference height t is not greater than the threshold value m, the end of the burr of the rear burr area is judged.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.
Claims (8)
1. The method for detecting the welding quality of the friction stir welding surface is characterized by comprising the following steps of:
(1) Acquiring continuous weld surface depth images;
(2) Intercepting a welding seam surface depth image with proper step length, dividing the intercepted welding seam surface depth image into areas, and selecting the areas on two sides of the depth image of each step length as a front side reference area and a rear side reference area respectively, wherein the front side and the rear side refer to the parts at the connection positions of the front side and the rear side respectively with two plates to obtain a front side reference area, a thinning area and a rear side reference area;
(3) Judging whether the flatness of the front reference area is smaller than a threshold value, if the flatness of the front reference area is smaller than the threshold value, obtaining a fitting plane of the front reference area by adopting a least square method, rotating a normal vector of the fitting plane to a direction parallel to a depth direction, and obtaining a pixel average value of a depth image of the front reference area as the front reference area height, wherein the front reference area height at the moment is used as the latest reference height; if not, judging whether the flatness of the rear reference area is smaller than a threshold value, if so, obtaining a fitting plane of the rear reference area by adopting a least square method, rotating a normal vector of the fitting plane to a direction parallel to the depth direction, and obtaining a pixel average value of a depth image of the rear reference area as the height of the rear reference area, wherein the height of the rear reference area at the moment is taken as the latest reference height; if not, taking the reference height of the previous section of depth image as the latest reference height;
(4) The latest reference height is different from the average height of the thinning area at this time to obtain the thinning amount.
2. The method for detecting the welding quality of a friction stir welding surface according to claim 1, further comprising identifying a groove defect in the thinned area, judging whether a groove exists, and if so, accumulating the lengths of the grooves; if not, the groove is ended, and the length information is returned.
3. The friction stir welding surface welding quality detecting method according to claim 2, wherein whether or not a groove is present is determined by calculating a fluctuation degree of a weld surface depth image of a thinned region or comparing a depth of the weld surface depth image of the thinned region with a reference height.
4. The friction stir welding surface welding quality detection method according to claim 1, further comprising dividing the truncated weld surface depth image into a front flash region and a rear flash region, wherein the front flash region is located between the front side flash region and the thinned region, and the rear flash region is located between the rear side flash region and the thinned region, and determining whether the front flash region and the rear flash region are flash or not, respectively.
5. The friction stir welding surface welding quality detection method according to claim 4, wherein flatness of the front side reference area and the rear side reference area is judged, and a burr reference height is obtained, and whether a difference between a maximum height value of the front side burr area and the burr reference height is larger than a threshold value and a difference between a maximum height value of the rear side burr area and the burr reference height is larger than a threshold value are respectively judged;
if the difference between the maximum height value of the front-side flash area and the flash reference height is larger than a threshold value, binarizing the front-side flash area to obtain a front-side flash width, calculating the front-side flash height, judging whether at least one of the front-side flash width and the front-side flash height is larger than a corresponding threshold value, if so, increasing the front-side flash by one step length, and recording the front-side flash area width and the front-side flash area height;
if the difference between the maximum height value of the front-side flash area and the flash reference height is not greater than the threshold value, the flash judgment of the front-side flash area is finished;
if the difference between the maximum height value of the rear burr area and the burr standard height is larger than a threshold value, binarizing the rear burr area to obtain rear burr width, calculating rear burr height, judging whether at least one of the rear burr width and the rear burr height is larger than a corresponding threshold value, if so, adding a step length to the rear burr, and recording the rear burr area width and the rear burr area height;
if the difference between the maximum height value of the rear burr region and the burr reference height is not greater than the threshold value, the burr determination of the rear burr region is ended.
6. The method according to claim 5, wherein if the difference between the maximum height value of the front burr region and the burr reference height is greater than a threshold value, binarizing the front burr region, fitting a minimum bounding rectangle of the obtained region of interest, taking the width of the minimum bounding rectangle as the front burr width, and calculating the difference between the maximum height value of the front burr region and the burr reference height as the front burr height.
7. The method according to claim 5, wherein if the difference between the maximum height value of the rear burr region and the burr reference height is greater than a threshold value, the rear burr region is binarized, a minimum bounding rectangle of the obtained region of interest is fitted, the width of the minimum bounding rectangle is taken as the rear burr width, and the difference between the maximum height value of the rear burr region and the burr reference height is calculated as the rear burr height.
8. The friction stir welding surface welding quality detection method according to claim 5, wherein after the flatness of the front side reference area and the rear side reference area is judged, the flatness is classified into four cases, then a flash reference height is obtained, and when the flatness of only the front side reference area is smaller than a threshold value, the average height of the front side reference area is calculated as the flash reference height; when the flatness of the rear side reference area is smaller than the threshold value, calculating the average height of the rear side reference area as the flash reference height; when the flatness of the front side reference area and the flatness of the rear side reference area are smaller than the threshold value, calculating the average heights of the front side reference area and the rear side reference area, and taking the average heights as the flash reference heights; and when the flatness of the front side reference area and the flatness of the rear side reference area are both larger than the threshold value, taking the latest reference height calculated before as the flash reference height.
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| US18/036,880 US11878364B2 (en) | 2022-06-27 | 2022-10-26 | Method for detecting surface welding quality of friction stir welding |
| PCT/CN2022/127634 WO2024000953A1 (en) | 2022-06-21 | 2022-10-26 | Testing method for welding quality of friction stir welded surface |
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| CN115070251B (en) * | 2022-06-21 | 2024-01-05 | 苏州大学 | Friction stir welding surface welding quality detection method |
| US11878364B2 (en) | 2022-06-27 | 2024-01-23 | Soochow University | Method for detecting surface welding quality of friction stir welding |
| CN115345878B (en) * | 2022-10-18 | 2023-01-31 | 广州市易鸿智能装备有限公司 | High-precision method and device for detecting distance between nickel sheet and bus sheet of lithium battery |
| CN116228640B (en) * | 2022-12-14 | 2024-04-12 | 广州市斯睿特智能科技有限公司 | Depth image-based weld joint detection method, system, device and storage medium |
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