WO2024000953A1 - 搅拌摩擦焊表面焊接质量检测方法 - Google Patents

搅拌摩擦焊表面焊接质量检测方法 Download PDF

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Publication number
WO2024000953A1
WO2024000953A1 PCT/CN2022/127634 CN2022127634W WO2024000953A1 WO 2024000953 A1 WO2024000953 A1 WO 2024000953A1 CN 2022127634 W CN2022127634 W CN 2022127634W WO 2024000953 A1 WO2024000953 A1 WO 2024000953A1
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Prior art keywords
area
flash
height
front side
threshold
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PCT/CN2022/127634
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English (en)
French (fr)
Inventor
陈立国
徐雨生
张雯霞
林永勇
王阳俊
张华德
薛立伟
杨国舜
孙立宁
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苏州大学
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Priority to US18/036,880 priority Critical patent/US11878364B2/en
Publication of WO2024000953A1 publication Critical patent/WO2024000953A1/zh

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Classifications

    • 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
    • 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

Definitions

  • the invention relates to the technical field of friction stir weld detection, and in particular to a friction stir welding surface welding quality detection method.
  • Friction stir welding technology proposed by the British Welding Technology Institute in 1991 is a typical new green welding technology.
  • the welding process does not produce smoke, arc light, and does not require gas protection and other material filling, especially when welding aluminum alloys. Its very large advantages have made it widely used in the manufacturing of various aluminum alloy structural parts in aerospace, automobiles, ships, rail transit vehicles and other fields.
  • the working principle of friction stir welding is as follows: the high-speed rotating stirring head penetrates into the workpiece, generating frictional heat at the contact part, causing the metal to form a plastic softening layer.
  • the upsetting force is exerted on the welding material through the shoulder of the stirring needle, thereby squeezing the rear material.
  • the pressing amount, spindle speed, feed speed, etc. usually need to be manually controlled. Welding defects, excessive thinning, flash, etc. may occur at the weld.
  • defects such as welding grooves are mainly detected through manual identification.
  • the detection of thinning usually after welding is completed, the welding material is removed from the tooling and then an acoustic thickness gauge is used to detect the thickness of the weld seam. This is not only labor-intensive, but also very difficult to reset the tooling if a problem is discovered.
  • There is no effective detection method for flash but it is directly removed by manual shoveling with a pneumatic flat shovel or post-weld milling.
  • the friction stir welding speed is generally 0.4m/min to 2m/min, which is an automated high-speed welding.
  • the final welding quality is only manually inspected, which is difficult to adapt to this speed range and greatly limits production efficiency.
  • the purpose of the present invention is to provide a friction stir welding surface welding quality detection method.
  • a friction stir welding surface welding quality inspection method includes the following steps:
  • the present invention obtains the surface depth image of the friction stir weld seam through laser scanning, and can reduce the friction stir weld seam whose surface morphology is a complex curved surface when the welding part is slightly deformed due to stress and heating.
  • On-machine inspection of thin parts, surface grooves, and flash edges with a high degree of automation.
  • the benchmark can be updated in real time height to avoid large fluctuations in the calculation of the reference height of the thinned beam.
  • the detection results of the thinning amount are relatively accurate.
  • the determination of grooves and flash edges is fast and accurate. By feeding back relevant and accurate welding quality information, it provides the basis for later processing.
  • Providing reference can further improve production efficiency and welding quality, and can adapt to welding speeds from 0.4m/min to 2m/min, with real-time detection effects.
  • Figure 1 is a schematic structural diagram of a detection system according to a preferred embodiment of the present invention.
  • Figure 2 is a schematic structural diagram of the C-axis and X-axis grating installation of the line laser scanner and the machine tool according to the preferred embodiment of the present invention
  • Figure 3 is a cross-sectional view of a friction stir weld according to a preferred embodiment of the present invention.
  • Figure 4 is a flow chart for detecting thinning amount and groove defects according to the preferred embodiment of the present invention:
  • Figure 5 is a flow chart for determining flash on both sides of the weld according to the preferred embodiment of the present invention.
  • Figure 6 is a schematic diagram of raising the judgment standard when the reference heights on both sides are different according to the preferred embodiment of the present invention.
  • FIG. 1 is a structural diagram of a detection system for detecting welding quality according to the present invention, including an industrial computer 1, an Ethernet switch 2, a controller 3, a PLC 4, a line laser scanner 5, and a CNC machine tool 6.
  • the industrial computer 1 is connected to the Ethernet switch 2
  • the Ethernet switch 2 is connected to the controller 3 and PLC4 respectively
  • the controller 3 is connected to the line laser scanner 5.
  • the line laser scanner 5 uses an encoder triggering method to collect data, it also includes an X-axis grating 7 and a Y-axis grating 8.
  • the X-axis grating 7 and the Y-axis grating 8 are respectively installed on the X-axis and Y-axis of the CNC machine tool 6.
  • the X-axis grating 7 includes an X-axis incremental grating ruler 701 and an X-axis direction reading head 702, and the Y-axis grating 8 includes a Y-axis direction incremental grating ruler 801 and a Y-axis direction reading head 802.
  • the line laser scanner 5 can also use a continuous triggering method that matches the welding speed to collect data. That is, to obtain continuous images, the welding speed needs to correspond to the scanning frequency and scan at a fixed frequency. At this time, there is no need to X-axis grating 7 and Y-axis grating 8 need to be set.
  • the line laser scanner 5 is installed on the back side of the movement direction of the C-axis 601 of the CNC machine tool 6 to ensure safety and reduce the interference of flying chips during the welding process.
  • the line laser scanner 5 is
  • the laser 501 is irradiated on the friction stir weld 10, and the welding direction is perpendicularly bisected by the line laser 501.
  • the X-axis direction incremental grating ruler 701 and the X-axis direction reading head 702 of the X-axis grating 7 are installed on the stage and the base of the CNC machine tool 6 respectively.
  • the Y-axis direction incremental grating ruler 801 of the Y-axis grating 8 and Y-axis direction reading heads 802 are respectively installed on the stage and base of the CNC machine tool 6 .
  • the X-axis direction incremental grating ruler 701 and the Y-axis direction incremental grating ruler 801 remain stationary, and the X-axis direction reading head 702 and the Y-axis direction reading head 802 can move, thereby causing relative movement to generate pulse signals as a welding process. Trigger signal for centerline laser scanner 5.
  • an air injection port 11 is provided next to the stirring needle 602 of the C-axis 601 to reduce the interference of the flying debris on the depth image.
  • the embodiment of the present invention mainly detects linear welds. During the welding process, the line laser scanner 5 simultaneously moves along the direction of the weld and continuously obtains depth information on the surface of the weld.
  • the welding movement starts, the X-axis grating 7 and the Y-axis grating 8 generate pulses and input them to the controller 3.
  • the controller 3 receives the pulses and counts them.
  • the control line laser scanner 5 scans the weld seam 10 to obtain the image.
  • the Ethernet switch 2 can Controller 3, industrial computer 1, and PLC4 are connected for communication.
  • the present invention preferably uses line laser scanning to obtain the surface depth image of the friction stir weld 10, and calculates the amount of thinning, grooves, flash, etc. based on the image. Defect feature extraction.
  • the embodiment of the present invention discloses a friction stir welding surface welding quality detection method, which includes the following steps:
  • the depth image of the weld seam surface is intercepted at equal intervals as a unit length with an appropriate step size, which is the length along the length direction of the weld seam.
  • the step length is a set fixed value, which can be 1mm.
  • the welding seam is thin and short, it can take a value smaller than 1mm; when the welding seam is wide and long, it can take a value larger than 1mm.
  • the scanning depth image and intercepted image processing are performed at the same time. When the scanned image can reach the step size, the image can be intercepted for processing. When the intercepted image processing is completed, just wait for the newly scanned image. As long as the newly scanned image reaches the step size, Processed immediately.
  • the amount of thinning is one of the important detection indicators. Because a large amount of thinning indicates that a certain part of the weldment has become very thin. If it is thinner, it will affect the welding quality and the stiffness of the material. Therefore, the amount of thinning needs to be detected. . Since the plate will deform during the welding process of the thin plate, the "datum” is changing. By cutting the weld surface depth image into small segments at equal intervals according to the step size, within this segment, the "datum” and “datum” are respectively Make a difference between "thinning area", find the thinning amount of this small section, and then record each thinning amount in sequence, which is the thinning amount of a weld.
  • the flatness of the front reference area and the rear reference area By selecting the images on both sides of the depth image of each step as the front reference area and the rear reference area respectively, the two sides refer to the parts connected to the two plates respectively, and the front reference area and the rear reference area are obtained respectively.
  • the standard deviation of the pixel value If the standard deviation of the pixel value is relatively small, it means it is relatively flat. If the flatness of the front reference area is less than the threshold, the least squares method is used to obtain the fitting plane of the front reference area, and the normal vector of the fitting plane is rotated to a direction parallel to the depth direction.
  • the reference area selects the area with a fixed number of columns in the front edge of the depth image as the reference area, use the least squares method to fit a plane in this area, and get the normal vector of this plane, and then rotate this normal vector to be parallel to the depth direction.
  • the direction means that the "base” is horizontal, the depth image of this step is no longer tilted, and the depth direction is perpendicular to the "base” plane.
  • the average pixel value of the depth image of the front reference area is obtained as the height of the front reference area.
  • the height of the front side reference area at this time is used as the latest reference height, and the difference between the reference height and the average height of the thinning area is used as the value of the thinning amount.
  • the flatness of the front reference area is not less than the threshold, then determine whether the flatness of the rear reference area is less than the threshold. If the flatness of the rear reference area is less than the threshold, use the least squares method to obtain the fitting plane of the rear reference area. Rotate the normal vector of the fitting plane to a direction parallel to the depth direction. That is to say, the area with a fixed number of columns in the back edge of the depth image is selected as the "reference" area, and the least squares method is used to fit a plane in this area.
  • the normal vector of the plane can be obtained, and then the normal vector is rotated to be consistent with "
  • the "depth direction” is parallel to the direction, which means that the "base” is horizontal, the depth image of this step is no longer tilted, and the depth direction is perpendicular to the "base” plane.
  • the average pixel value of the depth image of the rear reference area is obtained as the height of the rear reference area.
  • the height of the rear side reference area is used as the latest reference height, and the difference between the reference height and the average height of the thinning area is used as the value of the thinning amount.
  • the reference height of the previous weld surface depth image will be used as the reference height for this calculation of the thinning amount.
  • the average height of the thinned area refers to the average pixel value of the thinned area.
  • the weldment If there is a groove at the weld, it is easy for the weldment to corrode or break. Therefore, it also includes identifying the groove defects in the thinned area and determining whether there is a groove. If so, the length of the groove is accumulated; if not, This section of groove ends and the length information is returned. In terms of detecting grooves on the weld surface, the presence of grooves is determined 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.
  • the calculation of the fluctuation degree of the depth image of the thinned area refers to: if the welding quality is good, the thinned area is relatively flat, and the standard deviation of the depth value of the thinned area is used as the basis for judgment. If the standard deviation is large, it means that the thinned area is thinned. The area is uneven and grooved. Comparing the depth of the thinned area with the reference height refers to: the pixel value in the depth image can also be called the depth value. That is, if there are grooves, the depth value in the thinned area image will be smaller, then the pixel value in the depth image will be smaller.
  • the depth value is compared with the pixel average of the "base” area (the image area with a fixed number of columns on the edge of the depth image set), which is the base height. If the difference between the two is large, it means there is a groove. If there is a groove, it is a continuous section, and the detection is calculated using a smaller "step size", so it is equivalent to cutting a section of the groove into several small sections in sequence along the length direction. If there is a groove, Then there will be several "small sections” with grooves in succession. Add up the lengths of the "small sections” in order to get the length of the groove.
  • FIG. 5 is a flow chart for determining the flash on both sides of the weld, using images with the same step size as the calculation of the thinning amount. There is flash on both sides of the weld. The front flash and the rear flash are detected separately. The two detection processes are independent and the same detection steps are used.
  • the front side flash area is binarized to obtain the front side flash width, and the front side flash height is calculated to determine the front side Whether at least one of the flash width and the front flash height is greater than the corresponding threshold, if so, the front flash increases by one step, and the front flash area width and front flash area height are recorded;
  • the flash determination of the front flash area ends;
  • the rear side flash area is binarized to obtain the rear side flash width, and the rear side flash height is calculated to determine the rear side Whether at least one of the flash width and the rear flash height is greater than the corresponding threshold, if so, increase the rear flash by one step, and record the width of the rear flash area and the height of the rear flash area;
  • the burr determination of the rear burr area ends.
  • the judgment is divided into four situations, and then the flash reference height t is obtained.
  • the flatness of only the front reference area is less than the threshold, calculate the average height of the front reference area as the flash reference height t;
  • the flatness of only the rear reference area is less than the threshold, calculate the average height of the rear reference area as Flash reference height t;
  • the flatness of the front reference area and the rear reference area are both less than the threshold, calculate the average height of the front reference area and the rear reference area as the flash reference height t;
  • front reference When the flatness of the area and the flatness of the rear reference area are both greater than the threshold, the latest reference height calculated previously is used as the flash reference height t.
  • the latest reference height is selected as the reference height of the previous image, that is, It is said that when the reference at this time is blocked, the reference height of the previous image is closest to the position of the depth image at this time on the weld, which can minimize the interference of deformation.
  • the average height of the front reference area refers to the average pixel value of the front reference area
  • the average height of the rear reference area refers to the average pixel value of the rear reference area.
  • the average height of the front reference area and the rear reference area refers to the average pixel value of the front reference area and the rear reference area.
  • a threshold interval [t+ ⁇ , t1] that is larger than the flash reference height t to binarize the front side flash area, and fit the minimum circumscribed rectangle of the resulting region of interest (ROI), and divide the minimum circumscribed rectangle into
  • the width of the front side burr area is taken as the width d1 of the front side burr area, and the difference between the maximum height value t1 of the front side burr area and the burr reference height t is calculated as the front side burr height h1. If the width d1 exceeds the threshold D1 or the height h1 exceeds the threshold H1, it is determined that flash exists, and the flash length information of the front flash area is increased by one step, and the width d1 and height h1 of the front flash area are recorded. If the difference between the maximum height value t1 of the front burr area and the burr reference height is not greater than the threshold m, it is determined that the burrs of the front burr area have ended.
  • the width of the rear burr area is taken as the width d2 of the rear side burr area, and the difference between the maximum height value t2 of the rear side burr area and the burr reference height t is calculated as the height h2 of the rear side burr area. If the width d2 exceeds the threshold D2 or the height h2 exceeds the threshold H2, it is determined that flash exists, and the length information of the rear flash area is increased by one step, and the width d2 and height h2 of the rear flash area are recorded. If the difference between the maximum height value t2 of the rear side burr area and the burr reference height t is not greater than the threshold m, it is determined that the burring of the rear side burr area has ended.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Quality & Reliability (AREA)
  • Pressure Welding/Diffusion-Bonding (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)

Abstract

一种搅拌摩擦焊表面焊接质量检测方法，包括以下步骤：获取连续的焊缝表面深度图像；以适当的步长截取焊缝表面深度图像，将截取的焊缝表面深度图像划分区域，得到前侧基准区域、减薄区域和后侧基准区域；判断前侧基准区域的平整度是否小于阈值，若是，则以此时的前侧基准区域高度作为最新的基准高度；若否，则判断后侧基准区域的平整度是否小于阈值，若是，则以此时的后侧基准区域高度作为最新的基准高度；若否，则以前一段深度图像的基准高度作为最新的基准高度；将最新的基准高度与此时的减薄区域的平均高度作差，得到减薄量。该检测方法自动化程度高，检测结果准确，为后期处理提供参考，提高生产效率和焊接质量。

Description

搅拌摩擦焊表面焊接质量检测方法 技术领域
本发明涉及搅拌摩擦焊缝检测技术领域，尤其涉及一种搅拌摩擦焊表面焊接质量检测方法。
 背景技术
1991年由英国焊接技术研究所提出的搅拌摩擦焊接技术是一种典型的新型绿色焊接技术，其焊接过程不会产生烟尘、弧光，无需气体保护和其它材料填充，尤其在针对铝合金焊接时具有非常大的优势，使得其在航空航天、汽车、船舶、轨道交通车辆等领域的各类铝合金结构件制造方面得到了广泛地应用。
搅拌摩擦焊的工作原理为：高速旋转的搅拌头扎入工件，在接触部位产生摩擦热，使金属形成塑性软化层，通过搅拌针轴肩对焊接材料施加顶锻力，从而挤压后部材料填补空腔，但在焊接过程中，下压量、主轴转速、进给速度等通常需要人为调控，焊缝处可能会出现焊接缺陷、减薄量过大、飞边等情况。
 技术问题
目前主要通过人工识别的方式检测焊接的沟槽等缺陷。而减薄量的检测方面，通常为焊接完成后，将焊接材料从工装拆下再使用声学测厚仪检测焊缝厚度，不仅需耗费人力，若发现问题后重新复位工装非常困难。对于飞边并没有有效的检测手段，而是采用气动扁铲手动铲除或焊后铣削的方式直接去除。搅拌摩擦焊接速度一般为0.4m/min到2m/min，属于自动化高速焊接，对最终的焊接质量仅采用人工检测的方式进行，难以适应这一速度范围，很大程度上限制了生产效率。
 技术解决方案
针对现有技术不足，本发明的目的在于提供一种搅拌摩擦焊表面焊接质量检测方法。
为了实现上述目的，本发明一实施例提供的技术方案如下：
一种搅拌摩擦焊表面焊接质量检测方法，包括以下步骤：
（1）获取连续的焊缝表面深度图像；
（2）以适当的步长截取焊缝表面深度图像，将截取的焊缝表面深度图像划分区域，得到前侧基准区域、减薄区域和后侧基准区域；
（3）判断前侧基准区域的平整度是否小于阈值，若是，则以此时的前侧基准区域高度作为最新的基准高度；若否，则判断后侧基准区域的平整度是否小于阈值，若是，则以此时的后侧基准区域高度作为最新的基准高度；若否，则以前一段深度图像的基准高度作为最新的基准高度；
（4）将最新的基准高度与此时的减薄区域的平均高度作差，得到减薄量。
 有益效果
本发明在搅拌摩擦焊接过程中，通过激光扫描获取搅拌摩擦焊缝表面深度图像，可在焊接件因受力受热产生轻微变形的情况下，对表面形貌为复杂曲面的搅拌摩擦焊缝的减薄量、表面沟槽、飞边进行在机检测，自动化程度高，针对会因受力受热产生形变的焊接对象尤其是薄板焊件，在出现板材上翘以及局部倾斜现象时，能够实时更新基准高度，避免计算减薄梁的基准高度产生很大波动，减薄量的检测结果相对准确，同时对沟槽以及飞边的判定快速且准确，通过反馈相关准确的焊接质量信息，为后期的处理提供参考，可以进一步提高生产效率和焊接质量，且可以适应0.4m/min到2m/min的焊接速度，具有实时检测的效果。
 附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍。
图1为本发明的优选实施例的检测系统的结构示意图；
图2 为本发明的优选实施例的线激光扫描仪、机床的C轴以及X轴光栅安装的结构示意图；
图3为本发明的优选实施例的搅拌摩擦焊缝的截面图；
图4为本发明的优选实施例对减薄量和沟槽缺陷的检测流程图：
图5为本发明的优选实施例的焊缝两侧飞边的判定流程图；
图6为本发明的优选实施例的两边基准高度不同时将判断基准抬高的示意图；
图中：1、工控机，2、以太网交换机，3、控制器，4、PLC，5、线激光扫描仪，501、线激光，6、数控机床，601、C轴，602、搅拌针，7、X轴光栅，701、X轴方向增量式光栅尺，702、X轴方向读数头，801、Y轴方向增量式光栅尺，802、Y轴方向读数头，9、异或运算与放大电路，10、焊缝，11、喷气口。
 本发明的实施方式
为了使本技术领域的人员更好地理解本发明中的技术方案，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述。
图1 为本发明用于检测焊接质量的检测系统的结构图，包括工控机1、以太网交换机2、控制器3、PLC4、线激光扫描仪5、数控机床6。其中，工控机1与以太网交换机2相连接，以太网交换机2分别与控制器3、PLC4相连接，控制器3与线激光扫描仪5相连接。若线激光扫描仪5采用编码器触发的方式进行数据采集，则还包括X轴光栅7和Y轴光栅8，X轴光栅7和Y轴光栅8分别安装在数控机床6的X轴向和Y轴向，当焊接方向沿X轴向或Y轴向时，均会产生脉冲信号，通过异或运算与放大电路9进行脉冲信号的合并后接入控制器3。X轴光栅7包括X轴方向增量式光栅尺701和X轴方向读数头702，Y轴光栅8包括Y轴方向增量式光栅尺801和Y轴方向读数头802。可以理解的是，线激光扫描仪5也可以采用与焊接速度相匹配的连续触发方式进行数据采集，也就是获取连续的图像需要焊接速度与扫描频率对应起来，以固定频率扫描，此时就不需要设置X轴光栅7和Y轴光栅8。
请参阅图2，线激光扫描仪5安装于数控机床6的C轴601运动方向的后侧，确保安全，减小焊接过程中飞屑的干扰，同时使得在焊接过程中线激光扫描仪5的线激光501照射于搅拌摩擦焊缝10上，且焊接方向垂直平分于线激光501。 X轴光栅7的X轴方向增量式光栅尺701和X轴方向读数头702分别安装于数控机床6的载物台和基座上，Y轴光栅8的Y轴方向增量式光栅尺801和Y轴方向读数头802分别安装于数控机床6的载物台和基座上。X轴方向增量式光栅尺701和Y轴方向增量式光栅尺801保持不动，X轴方向读数头702和Y轴方向读数头802能够移动，从而有相对移动产生脉冲信号，作为焊接过程中线激光扫描仪5的触发信号。
为了在焊接过程中持续喷气，以去除焊接过程产生的飞屑，在C轴601的搅拌针602旁设置有喷气口11，以减少飞屑对深度图像产生的干扰。
由于线激光扫描仪5的线激光501与搅拌针602之间具有一定距离，且激光的测量范围有限，为保证焊接过程中焊缝表面深度图像的获取不受数控机床6的C轴601旋转的干扰，本发明实施例主要针对直线焊缝进行检测。在焊接的过程中，线激光扫描仪5同时沿焊缝方向运动，并持续获取焊缝表面的深度信息。
焊接运动开始，X轴光栅7和Y轴光栅8产生脉冲，输入给控制器3，该控制器3接收脉冲并计数，控制线激光扫描仪5扫描焊缝10获得图像，以太网交换机2能够将控制器3、工控机1、PLC4连接起来进行通讯。
为了快速且相对准确地实现表面焊接质量的快速检测，本发明优选使用线激光扫描的方式，获取搅拌摩擦焊缝10表面深度图像，基于该图像进行减薄量的计算、沟槽、飞边等缺陷的特征提取。
本发明实施例公开了一种搅拌摩擦焊表面焊接质量检测方法，包括以下步骤：
（1）获取连续的焊缝表面深度图像；
（2）以适当的步长截取焊缝表面深度图像；
（3）将截取的焊缝表面深度图像划分区域，得到前侧基准区域、减薄区域和后侧基准区域；
（4）计算前侧基准区域与后侧基准区域的平整度，判断前侧基准区域的平整度是否小于阈值，若是，则以此时的前侧基准区域高度作为最新的基准高度；若否，则判断后侧基准区域的平整度是否小于阈值，若是，则以此时的后侧基准区域高度作为最新的基准高度；若否，则以前一段深度图像的基准高度作为最新的基准高度；
（5）将最新的基准高度与此时的减薄区域的平均高度作差，得到减薄量。
优选地，以适当的步长作为一个单位长度等间隔截取焊缝表面深度图像，步长是沿着焊缝长度方向的长度。步长是设定的固定值，可以为1mm，当焊缝较细较短，可以取比1mm更小的值；当焊缝较宽较长，可以取比1mm大的值。将扫描深度图像与截取图像处理同时进行，当扫描的图像能够达到步长就可以截取图像进行处理，当截取的图像处理完成，等待新扫描的图像即可，只要新扫描的图像达到步长就即刻处理。
减薄量是重要检测指标之一，因为减薄量一大，说明焊接件的某一部位变得很薄了，薄了就会影响焊接质量和材料的刚度，因此需要对减薄量进行检测。由于在焊接薄板的过程中，板材是会变形的，所以这个“基准”在变化，通过将焊缝表面深度图像按照步长等间距截成小段，在这一小段内分别将“基准”与“减薄区域”做差，求出这一小段的减薄量，然后将每个减薄量按顺序记录，即为一条焊缝的减薄量。
焊缝10的截面如图3所示。下面说明每一步长的减薄量和沟槽的检测方法，如图4所示。
首先，判断前侧基准区域与后侧基准区域的平整度。通过选取每一步长的深度图像两侧的图像分别作为前侧基准区域、后侧基准区域，两侧指的是分别与两个板材连接处的部分，分别求前侧基准区域、后侧基准区域的像素值标准差，若像素值标准差比较小则说明相对平整。若前侧基准区域的平整度小于阈值，采用最小二乘法得到前侧基准区域的拟合平面，将拟合平面的法向量旋转至与深度方向平行的方向。也就是说选择深度图像前侧边缘中固定列数的区域作为基准区域，以该区域采用最小二乘法拟合一个平面，可得到这个平面的法向量，然后将这个法向量旋转到与深度方向平行的方向，就意味着，“基准”水平了，该段步长的深度图像不再倾斜，深度方向与“基准”平面垂直。求取前侧基准区域的深度图像的像素平均值作为前侧基准区域高度。以此时的前侧基准区域高度作为最新的基准高度，将基准高度与减薄区域的平均高度作差，作为减薄量的值。若前侧基准区域的平整度不小于阈值，则判断后侧基准区域的平整度是否小于阈值，若后侧基准区域的平整度小于阈值，采用最小二乘法得到后侧基准区域的拟合平面，将拟合平面的法向量旋转至与深度方向平行的方向。也就是说选择深度图像后侧边缘中固定列数的区域作为“基准”区域，以该区域采用最小二乘法拟合一个平面，可得到这个平面的法向量，然后将这个法向量旋转到与“深度方向”平行的方向，就意味着，“基准”水平了，该段步长的深度图像不再倾斜，深度方向与“基准”平面垂直。求取后侧基准区域的深度图像的像素平均值作为后侧基准区域高度。以后侧基准区域高度作为最新的基准高度，将基准高度与减薄区域的平均高度作差，作为减薄量的值。若前侧基准区域的平整度与后侧基准区域的平整度均大于平整度阈值，则以前一段焊缝表面深度图像的基准高度作为此次计算减薄量的基准高度。减薄区域的平均高度指的是减薄区域的像素平均值。通过这种方式可以很大程度上减小因焊件形变对减薄量的计算造成的影响，且可获得减薄量与焊接行程的对应关系。通过将焊缝10沿长度方向的减薄量显示出来，而且可以得到该减薄量的对应位置，直观知道减薄量的值是否过大，若减薄量太大说明焊接的下压量太大，通过对该位置的焊接下压量及时调整，避免影响焊接质量。
若焊缝处存在沟槽，容易使焊件易腐蚀或者易断裂，因此，还包括识别减薄区域的沟槽缺陷，判断是否存在沟槽，若是，则沟槽的长度进行累加；若否，此段沟槽结束，返回长度信息。在检测焊缝表面沟槽方面，通过计算减薄区域深度图像的波动程度或将该减薄区域的深度与基准高度进行比较来判断是否存在沟槽。其中计算减薄区域深度图像的波动程度指的是：如果焊接质量较好，则减薄区域相对平整，取该减薄区域深度值的标准差作为判断依据，如果标准差大，则说明减薄区域不平整，有沟槽。将该减薄区域的深度与基准高度进行比较指的是：深度图像里的像素值也可以叫深度值，就是要是有沟槽，则减薄区域图像里的深度值会较小，则将该深度值与“基准”区域（设置的深度图像边缘固定列数的图像区域）的像素平均值也就是基准高度作比较，若两者相差很大，说明有沟槽。如果有沟槽则是连续的一段，而检测时是采用较小的“步长”来计算的，所以相当于是将一段沟槽沿长度方向，按顺序截成了若干小段，若有沟槽，则会连续出现几个“小段”有沟槽的情况，将“小段”的长度按顺序累加起来，就是沟槽的长度了。
还包括将截取的焊缝表面深度图像划分区域得到前侧飞边区域、后侧飞边区域，前侧飞边区域位于前侧基准区域与减薄区域之间，后侧飞边区域位于后侧基准区域与减薄区域之间，分别判断前侧飞边区域和后侧飞边区域是否存在飞边。图5为焊缝两侧飞边的判定流程图，使用与计算减薄量相同步长的图像。焊缝的两侧都有飞边，前侧飞边与后侧飞边是分开检测的，两者检测过程是独立的，采用的检测步骤相同。
首先，判断前侧基准区域与后侧基准区域的平整度，并得到飞边基准高度，分别判断前侧飞边区域的最大高度值与飞边基准高度的差是否大于阈值、后侧飞边区域的最大高度值与飞边基准高度的差是否大于阈值；
若前侧飞边区域的最大高度值与飞边基准高度的差大于阈值，则对前侧飞边区域进行二值化，得到前侧飞边宽度，并计算前侧飞边高度，判断前侧飞边宽度、前侧飞边高度中的至少一个是否大于对应的阈值，若是，则前侧飞边增加一个步长，并记录前侧飞边区域宽度、前侧飞边区域高度；
若前侧飞边区域的最大高度值与飞边基准高度的不大于高度阈值，则前侧飞边区域的飞边判定结束；
若后侧飞边区域的最大高度值与飞边基准高度的差大于阈值，则对后侧飞边区域进行二值化，得到后侧飞边宽度，并计算后侧飞边高度，判断后侧飞边宽度、后侧飞边高度中的至少一个是否大于对应的阈值，若是，则后侧飞边增加一个步长，并记录后侧飞边区域宽度、后侧飞边区域高度；
若后侧飞边区域的最大高度值与飞边基准高度的差不大于阈值，则后侧飞边区域的飞边判定结束。
判断前侧基准区域与后侧基准区域的平整度后，分为四种情况进行判断，然后得到飞边基准高度t。当仅前侧基准区域的平整度小于阈值时，计算前侧基准区域的平均高度作为飞边基准高度t；当仅后侧基准区域的平整度小于阈值时，计算后侧基准区域的平均高度作为飞边基准高度t；当前侧基准区域的平整度和后侧基准区域的平整度均小于阈值时，计算前侧基准区域和后侧基准区域的平均高度，作为飞边基准高度t；当前侧基准区域的平整度和后侧基准区域的平整度均大于阈值时，取之前计算所得的最新的基准高度作为飞边基准高度t，此时最新的基准高度选取为前一段图像的基准高度，也就是说当此时的基准都被遮挡的情况下，前一段图像的基准高度在焊缝上距离此时深度图像位置最近，能够最大程度上减少变形的干扰。其中，前侧基准区域的平均高度指的是前侧基准区域的像素平均值，后侧基准区域的平均高度指的是后侧基准区域的像素平均值。前侧基准区域和后侧基准区域的平均高度指的是前侧基准区域与后侧基准区域的像素平均值。
设置一较小的阈值m。
若前侧飞边区域的最大高度值t1与飞边基准高度t大于阈值m，当两块板材高度不一致，则两边的基准存在高度不同的情况，即错边，这种情况下，如果取两边的平均值即t，会因为错边造成飞边的误判，也就是说容易把本来不是飞边的判定为飞边，因此将t增加一个ε，将判断基准抬高，如图6所示，避免误判。使用比飞边基准高度t较大的阈值区间[t+ε，t1]对前侧飞边区域进行二值化，并拟合所得感兴趣区（ROI）的最小外接矩形，将该最小外接矩形的宽度作为前侧飞边区域的宽度d1，并计算前侧飞边区域的最大高度值t1与飞边基准高度t的差作为前侧飞边高度h1。若宽度d1超过阈值D1或者高度h1超过阈值H1则判定存在飞边，前侧飞边区域的飞边长度信息增加一个步长，并记录前侧飞边区域的宽度d1和高度h1。若前侧飞边区域的最大高度值t1与飞边基准高度的差不大于阈值m，则判定前侧飞边区域的飞边结束。
若后侧飞边区域的最大高度值t2与飞边基准高度t大于阈值m，当两块板材高度不一致，则两边的基准存在高度不同的情况，即错边，这种情况下，如果取两边的平均值即t，会因为错边造成飞边的误判，因此将t增加一个ε，将判断基准抬高，如图6所示，避免误判。使用比飞边基准高度t较大的阈值区间[t+ε，t2]对后侧飞边区域进行二值化，并拟合所得感兴趣区（ROI）的最小外接矩形，将该最小外接矩形的宽度作为后侧飞边区域的宽度d2，并计算后侧飞边区域的最大高度值t2与飞边基准高度t的差作为后侧飞边区域的高度h2。若宽度d2超过阈值D2或者高度h2超过阈值H2则判定存在飞边，后侧飞边区域的长度信息增加一个步长，并记录后侧飞边区域的宽度d2和高度h2。若后侧飞边区域的最大高度值t2与飞边基准高度t的差不大于阈值m，则判定后侧飞边区域的飞边结束。
对于本领域技术人员而言，显然本发明不限于上述示范性实施例的细节，而且在不背离本发明的精神或基本特征的情况下，能够以其他的具体形式实现本发明。因此，无论从哪一点来看，均应将实施例看作是示范性的，而且是非限制性的，本发明的范围由所附权利要求而不是上述说明限定，因此旨在将落在权利要求的等同要件的含义和范围内的所有变化囊括在本发明内。不应将权利要求中的任何附图标记视为限制所涉及的权利要求。
此外，应当理解，虽然本说明书按照实施方式加以描述，但并非每个实施方式仅包含一个独立的技术方案，说明书的这种叙述方式仅仅是为清楚起见，本领域技术人员应当将说明书作为一个整体，各实施例中的技术方案也可以经适当组合，形成本领域技术人员可以理解的其他实施方式。

Claims (10)

  1. 一种搅拌摩擦焊表面焊接质量检测方法，其特征在于，包括以下步骤：
    （1）获取连续的焊缝表面深度图像；
    （2）以适当的步长截取焊缝表面深度图像，将截取的焊缝表面深度图像划分区域，得到前侧基准区域、减薄区域和后侧基准区域；
    （3）判断前侧基准区域的平整度是否小于阈值，若是，则以此时的前侧基准区域高度作为最新的基准高度；若否，则判断后侧基准区域的平整度是否小于阈值，若是，则以此时的后侧基准区域高度作为最新的基准高度；若否，则以前一段深度图像的基准高度作为最新的基准高度；
    （4）将最新的基准高度与此时的减薄区域的平均高度作差，得到减薄量。
  2. 根据权利要求1所述的搅拌摩擦焊表面焊接质量检测方法，其特征在于，所述步骤（3）中，若前侧基准区域的平整度小于阈值，采用最小二乘法得到前侧基准区域的拟合平面，将拟合平面的法向量旋转至与深度方向平行的方向。
  3. 根据权利要求1所述的搅拌摩擦焊表面焊接质量检测方法，其特征在于，所述步骤（3）中，若后侧基准区域的平整度小于阈值，采用最小二乘法得到后侧基准区域的拟合平面，将拟合平面的法向量旋转至与深度方向平行的方向。
  4. 根据权利要求1所述的搅拌摩擦焊表面焊接质量检测方法，其特征在于，还包括识别减薄区域的沟槽缺陷，判断是否存在沟槽，若是，则沟槽的长度进行累加；若否，此段沟槽结束，返回长度信息。
  5. 根据权利要求4所述的搅拌摩擦焊表面焊接质量检测方法，其特征在于，通过计算减薄区域的焊缝表面深度图像的波动程度或将该减薄区域的焊缝表面深度图像的深度与基准高度进行比较来判断是否存在沟槽。
  6. 根据权利要求1所述的搅拌摩擦焊表面焊接质量检测方法，其特征在于，还包括将截取的焊缝表面深度图像划分区域得到前侧飞边区域、后侧飞边区域，所述前侧飞边区域位于前侧基准区域与减薄区域之间，所述后侧飞边区域位于所述后侧基准区域与减薄区域之间，分别判断前侧飞边区域和后侧飞边区域是否存在飞边。
  7. 根据权利要求6所述的搅拌摩擦焊表面焊接质量检测方法，其特征在于，判断前侧基准区域与后侧基准区域的平整度，并得到飞边基准高度，分别判断前侧飞边区域的最大高度值与飞边基准高度的差是否大于阈值、后侧飞边区域的最大高度值与飞边基准高度的差是否大于阈值；
    若前侧飞边区域的最大高度值与飞边基准高度的差大于阈值，则对前侧飞边区域进行二值化，得到前侧飞边宽度，并计算前侧飞边高度，判断前侧飞边宽度、前侧飞边高度中的至少一个是否大于对应的阈值，若是，则前侧飞边增加一个步长，并记录前侧飞边区域宽度、前侧飞边区域高度；
    若前侧飞边区域的最大深度值与飞边基准高度的差不大于阈值，则前侧飞边区域的飞边判定结束；
    若后侧飞边区域的最大高度值与飞边基准高度的差大于阈值，则对后侧飞边区域进行二值化，得到后侧飞边宽度，并计算后侧飞边高度，判断后侧飞边宽度、后侧飞边高度中的至少一个是否大于对应的阈值，若是，则后侧飞边增加一个步长，并记录后侧飞边区域宽度、后侧飞边区域高度；
    若后侧飞边区域的最大高度值与飞边基准高度的差不大于阈值，则后侧飞边区域的飞边判定结束。
  8. 根据权利要求7所述的搅拌摩擦焊表面焊接质量检测方法，其特征在于，对前侧飞边区域进行二值化，并拟合所得感兴趣区的最小外接矩形，将该最小外接矩形的宽度作为前侧飞边宽度，并分别计算前侧飞边区域的最大高度值与飞边基准高度的差作为前侧飞边高度。
  9. 根据权利要求7所述的搅拌摩擦焊表面焊接质量检测方法，其特征在于，对后侧飞边区域进行二值化，并拟合所得感兴趣区的最小外接矩形，将该最小外接矩形的宽度作为后侧飞边宽度，并分别计算后侧飞边区域的最大高度值与飞边基准高度的差作为后侧飞边高度。
  10. 根据权利要求7所述的搅拌摩擦焊表面焊接质量检测方法，其特征在于，当仅前侧基准区域的平整度小于阈值时，计算前侧基准区域的平均高度作为飞边基准高度；当仅后侧基准区域的平整度小于阈值时，计算后侧基准区域的平均高度作为飞边基准高度；当前侧基准区域的平整度和后侧基准区域的平整度均小于阈值时，计算前侧基准区域和后侧基准区域的平均高度，作为飞边基准高度；当前侧基准区域的平整度和后侧基准区域的平整度均大于阈值时，取之前计算所得的最新的基准高度作为飞边基准高度。
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