Deadband inspection using ultrasonic testing using signal integration

Abstract

The present disclosure relates to dead zone inspection using ultrasonic testing using signal integration. Specifically, it relates to an ultrasonic inspection system, method and software. In one embodiment, the ultrasonic inspection system includes an ultrasonic probe that introduces ultrasonic waves into a structure from a front wall and receives reflected waves to generate a response signal. The system also includes a processor that rectifies the response signal to generate a rectified signal, integrates a portion of the rectified signal within a detection time window to determine an energy sum, and generates an output based on the energy sum. The detection time window is defined as a front wall reflection and at least a portion of a near-surface dead zone after the front wall reflection.

Description

Technical Field

[0001] The present disclosure relates to the field of non-destructive inspection or evaluation of structures. Background Art

[0002] Non-destructive inspection (NDI) involves inspecting a structure without damaging, destroying or physically changing the structure in a permanent manner. For example, a special application of NDI is in the aircraft industry to inspect the structure for damage or defects (flaws) during the manufacture of the aircraft structure and / or after the structure is put into service. Ultrasonic testing is a type of NDI technology. In the pulse-echo mode of ultrasonic testing, a probe transmits ultrasonic waves into the structure and detects the reflection or echo of the ultrasonic waves off a reflector (e.g., a front wall, a rear wall, an anomaly or defect within the structure, etc.). The time elapsed between the emission of the ultrasonic wave and the receipt of the reflection at the probe indicates the depth of the reflector. A typical probe has a piezoelectric component (i.e., a transducer) that acts as a transmitter and a receiver. The piezoelectric component oscillates in response to an excitation pulse when acting as a transmitter that transmits ultrasonic waves, and oscillates in response to a reflection when acting as a receiver that generates a response signal. After the initial oscillation, the piezoelectric component will continue to reverberate for a certain time interval, which is called ringdown. The ringing of the piezoelectric element creates a dead zone below the front wall of the structure, referred to herein as the near-surface dead zone. Effective detection of anomalies or defects below the front wall of a structure within the near-surface dead zone remains a problem in ultrasonic testing. Summary of the invention

[0003] This article describes an improved ultrasonic testing technique that enables inspections in near-surface dead zones. As an overview, a probe transmits ultrasonic waves into a structure and captures reflections to generate a response signal. The response signal from the probe (after rectification) includes pulses representing reflections leaving the front wall of the structure. A portion of the response signal is integrated within a detection time window covering the front wall reflection to measure the energy of the response signal in the detection time window. Reflections of anomalies or defects leaving just below the front wall may be superimposed on the front wall reflection, or may be captured as one or more pulses in the response signal after the front wall reflection. By summing the energy of the response signal within the detection time window, anomalies or defects can be detected in near-surface dead zones. A technical benefit is that ultrasonic testing can be improved by detecting anomalies or defects just below the front wall of the structure, which were previously undetectable in ultrasonic testing.

[0004] One embodiment includes an ultrasound inspection system. The ultrasound inspection system includes an ultrasound probe configured to introduce ultrasound waves into a structure from a front wall and receive reflected waves to generate a response signal. The ultrasound inspection system also includes a processor configured to rectify the response signal to generate a rectified signal, integrate a portion of the rectified signal within a detection time window to determine an energy sum, and generate an output based on the energy sum. The detection time window is defined as a front wall reflection and at least a portion of a near-surface dead zone after the front wall reflection.

[0005] In another embodiment, the processor is configured to negatively half-wave rectify and invert the response signal to generate a rectified signal.

[0006] In another embodiment, the processor is configured to perform positive half-wave rectification on the response signal to generate a rectified signal.

[0007] In another embodiment, the processor is configured to full-wave rectify the response signal to generate a rectified signal.

[0008] In another embodiment, the processor is configured to define a null gate before the front wall reflection and to make the rectified signal zero within the null gate.

[0009] In another embodiment, the processor is configured to generate C-scan data of the structure based on the energy and .

[0010] In another embodiment, the ultrasound inspection system further includes a robotic arm configured to move the ultrasound probe over the structure; and a position sensor configured to determine position data of the ultrasound probe.

[0011] In another embodiment, the processor is configured to trigger a warning when the energy sum exceeds a threshold.

[0012] In another embodiment, the structure includes a composite part.

[0013] In another embodiment, an opaque layer is disposed on a front wall of the composite part; and a detection time window is provided based on a depth of a resin pool below the front wall.

[0014] In another embodiment, the structure comprises a part of an aircraft.

[0015] Another embodiment includes a method of inspecting a structure. The method includes the steps of directing ultrasonic waves into the structure from a front wall, receiving reflected waves to generate a response signal, rectifying the response signal to generate a rectified signal, integrating a portion of the rectified signal within a detection time window to determine an energy sum, and generating an output based on the energy sum. The detection time window is defined as a front wall reflection and at least a portion of a near-surface dead zone after the front wall reflection.

[0016] Another embodiment includes a non-transitory computer readable medium embodying programming instructions executed by a processor, the instructions directing the processor to implement a method of inspecting a structure. The method includes the steps of introducing ultrasonic waves into the structure from a front wall, receiving reflected waves to generate a response signal, rectifying the response signal to generate a rectified signal, integrating a portion of the rectified signal within a detection time window to determine an energy sum, and generating an output based on the energy sum. The detection time window is defined as a front wall reflection and at least a portion of a near-surface dead zone after the front wall reflection.

[0017] The features, functions, and advantages that have been discussed may be achieved independently in different embodiments or may be combined in yet other embodiments, and further details of these features, functions, and advantages may be seen with reference to the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Now, with reference to the drawings, some embodiments of the present invention will be described by way of example only. On all drawings, the same reference numbers represent the same element or the same type of element.

[0019] Figure 1 is a block diagram of an ultrasound inspection system in an exemplary embodiment.

[0020] Figure 2 is a magnified view of the ultrasound probe and the anterior wall of the structure.

[0021] Figure 3 is a graph illustrating a portion of a response signal.

[0022] Figure 4 is a flow chart illustrating a method of inspecting a structure in an exemplary embodiment.

[0023] Figure 5 is a graph showing a response signal in an exemplary embodiment.

[0024] Figure 6 is a graph showing a rectified signal in an exemplary embodiment.

[0025] Figure 7is a graph showing a rectified signal in an exemplary embodiment.

[0026] Figure 8 is a graph showing a rectified signal in an exemplary embodiment.

[0027] Fig. 9 is a graph illustrating a detection time window in an exemplary embodiment.

[0028] Fig.10 is another block diagram of an ultrasound inspection system in an exemplary embodiment.

[0029] Fig.11 is a cross-sectional view of a composite part in an exemplary embodiment.

[0030] Fig.12 is a flow chart illustrating a method of inspecting a structure in an exemplary embodiment.

[0031] Fig.13 An ultrasonic inspection system is illustrated as being positioned proximate to a composite part in an exemplary embodiment.

[0032] Fig.14 is a graph showing a response signal in an exemplary embodiment.

[0033] Fig.15 is a graph showing a rectified signal in an exemplary embodiment.

[0034] Fig.16 is a graph illustrating an empty gate in an exemplary embodiment.

[0035] Fig.17 is a graph illustrating a detection time window in an exemplary embodiment.

[0036] Fig.18 is a C-scan representation of C-scan data in an exemplary embodiment.

[0037] Fig.19 is a flow chart illustrating an aircraft manufacturing and service method in an illustrative embodiment.

[0038] Fig. 20 is a schematic diagram of an aircraft in accordance with an exemplary embodiment. DETAILED DESCRIPTION

[0039] The accompanying drawings and the following description illustrate specific exemplary embodiments. It should be appreciated that, although not explicitly described or shown herein, those skilled in the art will be able to design various arrangements that specifically implement the principles described herein and are included within the intended scope of the claims that follow this description. Moreover, any examples described herein are intended to aid in understanding the principles of the present disclosure and should be interpreted as not limiting. As a result, the present disclosure is not limited to the specific embodiments or examples described below, but is limited by the claims and their equivalents.

[0040] Figure 1 1 is a block diagram of an ultrasonic inspection system 100 in an exemplary embodiment. The ultrasonic inspection system 100 includes a collection of devices or apparatuses, mechanisms or subsystems configured to perform ultrasonic testing (UT) on a structure or test sample. The ultrasonic inspection system 100 can be used to inspect any number of structures in various industries (such as aircraft, automobiles or construction industries) where it is desired to detect flaws or defects in the structure. In this embodiment, the ultrasonic inspection system 100 includes the following subsystems: an ultrasonic probe 102 and a controller 104. The ultrasonic probe 102 (also known as an ultrasonic sensor) is a device or component that sends or transmits ultrasonic waves and captures or receives reflections or echoes. The ultrasonic probe 102 may include: a single piezoelectric element (PZT: piezoelectric element) 110 or transducer that acts as a transmitter and a receiver. The controller 104 includes circuits, logic, hardware, devices, etc., which are configured to provide an excitation signal (i.e., an excitation pulse) to the ultrasonic probe 102, process the response signal from the ultrasonic probe 102, and perform other actions for ultrasonic measurement. Controller 104 may be implemented on a hardware platform consisting of analog and / or digital circuits. Controller 104 may be implemented on a processor 105 executing instructions 107 stored in memory 106 (eg, Figure 1 107). The processor 105 includes an integrated hardware circuit configured to execute instructions 107, and the memory 106 is a non-transitory computer-readable storage medium for data, instructions 107, etc. and is accessible by the processor 105. The ultrasound inspection system 100 may include Figure 1 For example, the ultrasound inspection system 100 may include: a power supply, a network interface, a user interface, etc.

[0041] In this embodiment, the ultrasonic inspection system 100 is illustrated as performing an inspection on a structure 120. The term "structure" is not intended to be limiting, as the ultrasonic inspection system 100 can be used to inspect any number of parts or structures having different shapes and sizes, such as machined forgings, castings, or composite plates or parts. The inspection can be performed on newly manufactured structures or existing structures being inspected for preventive maintenance purposes. In addition, the structure 120 can be any number of materials. For example, the structure 120 can be a metallic material (e.g., aluminum), a composite material, etc.

[0042] The structure 120 includes a front wall 122 (also referred to as a front surface or front face) and a rear wall 124 (also referred to as a rear surface or rear face). The ultrasound probe 102 is positioned adjacent to the front wall 122 so as to introduce ultrasound waves 130 from the front wall 122 into the structure 120 in a pulse-echo mode. The ultrasound probe 102 may be in contact with the front wall 122, or may be separated from the front wall 122 using a delay line. Furthermore, a coupling agent 112 (e.g., water or another fluid) may be disposed between the front wall 122 and the ultrasound probe 102. The coupling agent 112 is a material that facilitates the transmission of ultrasound waves 130 from the ultrasound probe 102 into the structure 120. As the ultrasound waves 130 reflect off reflectors in the structure 120, the ultrasound probe 102 also receives reflected waves 132 (also referred to as reflections, echoes, or echoes). The ultrasound probe 102 converts the reflected waves 132 into a response signal 108, which is stored or buffered in the memory 106.

[0043] Figure 2 1 is an enlarged view of the ultrasonic probe 102 and the front wall 122 of the structure 120. When the ultrasonic probe 102 transmits an ultrasonic wave 130 that is introduced into the structure 120, a portion of the ultrasonic wave 130 will be reflected by the front wall 122 and captured by the ultrasonic probe 102 to generate a response signal 108. Typically, there is a dead zone detection gap 210 below the front wall 122, where anomalies or defects cannot be detected traditionally due to the ringing of the ultrasonic probe 102. The depth 212 of the dead zone detection gap 210 can vary depending on the frequency of the ultrasonic wave 130, the type of material being inspected, etc. For example, for a 5 MHz signal in a composite material, the depth 212 can be less than 0.100 inches below the front wall 122. After the ringing of the ultrasonic probe 102 (i.e., the ringing caused by the reflection off the front wall 122), the depth below the dead zone detection gap 210 can be inspected. Therefore, the depth directly below the dead zone detection gap 210 is referred to as the closest inspectable depth 214 behind the front wall 122.

[0044] Figure 33 is a graph 300 illustrating a portion of the response signal 108. Note that the excitation or initial pulse applied to the ultrasound probe 102 is omitted from the graph 300. This portion (e.g., A-scan) of the response signal 108 shows a front wall reflection 302 (also referred to as a front surface reflection), and a time interval following the front wall reflection 302. The front wall reflection 302 represents a reflection of the ultrasound wave 130 off the front wall 122 of the structure 120 (see FIG. Figure 2 ). The piezoelectric element 110 in the ultrasonic probe 102 oscillates upon receiving the front wall reflection 302 to generate Figure 3 The illustrated response signal 108 continues to reverberate for a certain time interval after receiving the front wall reflection 302 (ringing). This creates a dead zone after the front wall reflection 302, which is referred to herein as a near-surface dead zone 304. The near-surface dead zone 304 is a time interval after a reflection (e.g., the front wall reflection 302) during which the ultrasonic probe 102 reverberates or vibrates due to the reflection. For example, depending on the damping characteristics of the ultrasonic probe 102, the near-surface dead zone 304 may be one cycle, two cycles, three cycles, etc. of the response signal 108. The time 306 after the near-surface dead zone 304 represents the closest inspectable depth 214 below the front wall 122 (see Figure 2 ).

[0045] In the implementations described herein, the ultrasonic inspection system 100 is capable of detecting anomalies or defects in the near-surface dead zone 304 . Figure 4 is a flow chart illustrating a method 400 of inspecting a structure 120 in an exemplary embodiment. Figure 1 The steps of method 400 are described with reference to the ultrasonic inspection system 100 of FIG. 4 , but it should be understood by those skilled in the art that the methods described herein may be performed by other systems or devices. The steps of the methods described herein are not all inclusive and may include other steps not shown. The steps of the flowcharts shown herein may also be performed in an alternative order.

[0046] First, if Figure 1As shown, the ultrasonic probe 102 is positioned adjacent to the front wall 122 of the structure 120 and operated in a pulse-echo mode to inspect the structure 120 at that location. In the pulse-echo mode, the ultrasonic probe 102 converts electrical pulses into mechanical vibrations. Therefore, the controller 104 (e.g., via a pulse generator) provides an excitation pulse to the ultrasonic probe 102. In response to the excitation pulse, the ultrasonic probe 102 emits, transmits, or otherwise introduces an ultrasonic wave 130 from the front wall 122 into the structure 120 (step 402). The ultrasonic wave 130 reflected from the structure 120 returns to the ultrasonic probe 102 and is converted into a response signal 108. Therefore, the ultrasonic probe 102 receives or captures one or more reflected waves 132 to generate a response signal 108 (step 404). The time-sequential recording of the amplitude of the response signal 108 can be graphically imaged as A-scan data, such as Figure 3 shown.

[0047] The controller 104 receives the response signal 108 from the ultrasound probe 102 and stores or buffers the response signal 108 . Figure 5 Graph 500 illustrates response signal 108 in an exemplary embodiment. Graph 500 illustrates front wall reflection 302 and back wall reflection 504, which represent reflections of ultrasound wave 130 off front wall 122 and back wall 124, respectively. Figure 4 , the controller 104 then processes the response signal 108 as follows. The controller 104 rectifies the response signal 108 to generate a rectified signal or a processed signal (step 406). The rectified signal can be in the positive domain or the negative domain as desired. In one embodiment, the controller 104 performs negative half-wave rectification and inversion on the response signal 108 in the positive domain to generate a negative half-wave rectified signal (optional step 420). Figure 6 6 is a graph 600 showing a rectified signal 602 in an exemplary embodiment. In this embodiment, the response signal 108 is negatively half-wave rectified and inverted to generate the rectified signal 602. The rectified signal 602 includes a series of pulses. The pulse with the first highest peak 610 in the rectified signal 602 represents the front wall reflection 302 and can be referred to as the front wall pulse 606.

[0048] In another embodiment, the controller 104 performs positive half-wave rectification on the response signal 108 to generate a rectified signal 602 ( Figure 4 Optional step 422). Figure 77 is a graph 700 showing the rectified signal 602 in an exemplary embodiment. In this embodiment, the response signal 108 is positively half-wave rectified to generate the rectified signal 602. Again, the rectified signal 602 includes a series of pulses, and the pulse with the first highest peak 610 (i.e., the front wall pulse 606) represents the front wall reflection 302.

[0049] In another embodiment, the controller 104 performs full-wave rectification on the response signal 108 to generate a rectified signal 602 ( Figure 4 Optional step 424). Figure 8 8 is a graph 800 showing the rectified signal 602 in an exemplary embodiment. In this embodiment, the response signal 108 is full-wave rectified to generate the rectified signal 602. In the full-wave rectified signal 602, the front wall reflection 302 is represented by the following two pulses: the pulse with the first highest peak 610 (i.e., the front wall pulse 606), and the following pulse 806 in the rectified signal 602.

[0050] exist Figure 4 In step 408 , the controller 104 integrates a portion of the rectified signal 602 within a detection time window defined as the front wall reflection 302 and at least a portion of the near-surface dead zone 304 after the front wall reflection 302 . Fig. 99 is a graph 900 illustrating a detection time window 901 in an exemplary embodiment. Graph 900 illustrates a rectified signal 602 generated by performing negative half-wave rectification (and inverting) of the response signal 108, but a similar process may be performed on a rectified signal 602 generated by performing positive half-wave rectification or full-wave rectification. Different time points along the rectified signal 602 correspond to different depths within the structure 120. A detection time window 910 (also referred to as a detection gate) is limited or defined to the front wall 122 and the detection gap 210 below the front wall 122. In one embodiment, the controller 104 defines the detection time window 910 to start at the front wall reflection 302 (i.e., at the front wall pulse 606). For example, when operating in the positive domain, the detection time window 910 may start at the rising edge 920 of the front wall reflection 302, or where the rising edge 920 of the front wall reflection 302 exceeds a threshold voltage (e.g., 0.4 volts). The detection time window 910 ends at a fixed time after the rising edge 920. Therefore, the detection time window 910 specifically covers the front wall reflection 302 and the near-surface dead zone 304 after the front wall reflection 302. For example, the detection time window 910 can be set or defined to end one cycle after the front wall reflection 302, two cycles after the front wall reflection 302, three cycles after the front wall reflection 302, or some other time. The size (in units of time) of the detection time window 910 can be provided based on the frequency of the ultrasonic wave 130, the material used for the structure 120, the ringing time of the ultrasonic probe 102, the estimated depth of the anomaly or defect below the front wall 122, etc. The detection time window 910 is set so that the portion of the rectified signal 602 being integrated is limited to the front wall 122 of the structure 120 and at least a portion of the detection gap 210 below the front wall 122 (e.g., below the front wall 122 to the nearest inspectable depth 214), and does not include other anomalies or the back wall 124 at a depth below the detection gap 210.

[0051] By integrating in this manner, the controller 104 determines the energy sum of the portion of the rectified signal 602 that is within the detection time window 910. The energy sum can be used to indicate an anomaly or defect in the detection gap 210 below the front wall 122. Reflections of anomalies or defects leaving below the front wall 122 can be superimposed on the front wall reflection 302, which can cause the front wall pulse 606 to have a higher peak. Reflections of anomalies or defects leaving below the front wall 122 can additionally or alternatively cause one or more additional pulses after the front wall pulse 606. Accumulating energy within the detection time window 910 has the following technical benefits: these reflections of anomalies or defects leaving below the front wall 122 are captured in the near-surface dead zone 304 so that the anomalies or defects can be detected.

[0052] exist Figure 4 In step 410, the controller 104 generates an output 150 based on the energy sum, which is also Figure 1 exemplified. In one embodiment, the controller 104 compares the energy sum to a threshold value and triggers a warning 152 or alarm when the energy sum exceeds the threshold value (optional step 426). The warning 152 may include: an audible warning, a visual warning, or another type of warning. In another embodiment, the controller 104 generates C-scan data 154 of the structure 120 based on the energy sum (optional step 428). A C-scan refers to an image generated when data collected from an ultrasound examination is plotted as a plan view of the structure 120. Therefore, the C-scan data 154 generated by the controller 104 may include data points on a C-scan image of the structure 120. Then, the ultrasound probe 102 is moved to another position relative to the front wall 122 of the structure 120 (step 412), and the method 400 may be repeated at the new position.

[0053] The ultrasound probe 102 may be manually moved by an operator to inspect the structure 120 as described above. In another embodiment, the ultrasound inspection system 100 may be automated to move the ultrasound probe 102 for inspection. Fig.10 1 is another block diagram of an ultrasound inspection system 100 in an exemplary embodiment. In this embodiment, the ultrasound inspection system 100 also includes a positioning system 1002 configured to move the ultrasound probe 102 to different positions along the front wall 122 of the structure 120. In this embodiment, the positioning system 1002 includes a robotic arm 1004 and a position sensor 1006 (or multiple position sensors). The ultrasound probe 102 is mounted or attached to the robotic arm 1004 on an end effector or the like. As the robotic arm 1004 moves or scans the ultrasound probe 102 along the structure 120, data is sent to the controller 104 for processing. Based on commands from the controller 104, the robotic arm 1004 is automatically controlled to move the ultrasound probe 102 adjacent to the structure 120. The robotic arm 1004 typically includes multi-axis movement capabilities and uses software support to generate a three-dimensional profile to be used for measurement and inspection of the structure 120. The position sensor 1006 is configured to determine position data 1010 of the ultrasound probe 102 in a coordinate system (eg, X, Y, and Z in three-dimensional space) of the structure 120. The robotic arm 1004 and the position sensor 1006 may communicate with the controller 104 via a wired or wireless connection.

[0054] In operation, the robotic arm 1004 moves the ultrasound probe 102 to a first position relative to the front wall 122 of the structure 120. At the first position, the ultrasound probe 102 and the controller 104 perform the checks described in the method 400 to determine the energy sum of the rectified signal 602 at the first position. For example, when generating the C-scan data 154, the controller 104 converts the energy sum of the first position into a display value, such as a grayscale or color value. The controller 104 also receives position data 1010 of the first position from the position sensor 1006 and associates the position data 1010 of the first position with the display value. The controller 104 can store this information as the C-scan data 154. Then, the robotic arm 1004 moves the ultrasound probe 102 to a second position relative to the front wall 122 of the structure 120. At the second position, the ultrasound probe 102 and the controller 104 perform the checks described in the method 400 to determine the energy sum of the rectified signal 602 at the second position. Controller 104 converts the energy sum at the second location into a display value, receives position data 1010 for the second location from position sensor 1006, and associates the position data 1010 for the second location with the display value. This process is repeated for multiple locations to generate C-scan data 154 for structure 120.

[0055] In another embodiment, the ultrasound examination system 100 may also include a network interface 1020 and / or a user interface 1022. The network interface 1020 is a hardware component configured to communicate with a remote device via a network using a wired or wireless connection. The controller 104 can use the network interface 1020 to transmit the C-scan data 154 to the remote device via the network. The user interface 1022 is a hardware component that interacts with an end user or operator. For example, the user interface 1022 may include: a screen or touch screen (e.g., a liquid crystal display (LCD), a light emitting diode (LED) display, etc.), a keyboard or keypad, a tracking device (e.g., a trackball or touchpad), a speaker, and a microphone. The controller 104 can display the C-scan data 154 to the operator through the user interface 1022.

[0056] Figures 11 to 18 An example of ultrasonic testing in another embodiment is provided. Fig.11is a cross-sectional view of a composite part 1100 in an illustrative embodiment, which is an example of the structure 120 discussed above. The composite part 1100 is a laminated structure consisting of multiple layers of material (e.g., carbon fiber reinforced polymer (CFRP)) sandwiched together. The individual fibers within the layers of the laminated structure can be aligned parallel to each other, but different layers can exhibit different fiber orientations to increase the strength of the resulting composite part along different dimensions. The laminated structure also includes a resin (e.g., a thermosetting or thermoplastic) that cures and hardens the layers of the laminated structure into the composite part 1100. Like the structure 120, the composite part 1100 includes a front wall 122 and a rear wall 124. In this example, an opaque layer 1102 is applied or disposed on the front wall 122. For example, the opaque layer 1102 can be an opaque primer, paint, coating, surface film, etc. The opaque layer 1102 can be cured together with the composite part 1100. Fig.11 Also illustrated is a resin pool 1104 below the front wall 122 that is not visible in the visual inspection method due to the opaque layer 1102. The resin pool 1104 represents an anomaly or defect below the front wall 122, which may have a negative impact on the integrity of the composite part 1100 because it may represent a potential crack initiation site. The resin pool 1104 is illustrated as having a depth 1112 below the front wall 122. Because the resin pool 1104 is in close proximity to the front wall 122, it may be located in the near-surface dead zone 304 and cannot be detected using traditional inspection techniques. However, the resin pool 1104 can be detected using the inspection method initiated herein.

[0057] Fig.12 1 is a flow chart illustrating a method 1200 of inspecting a structure, such as composite part 1100, in an exemplary embodiment. However, it should be understood that method 1200 may be used to inspect other types of structures. Method 1200 may include steps similar to those described above for method 400, and those steps are labeled with the same reference numbers.

[0058] First, ultrasonic probe 102 is positioned adjacent to front wall 122 of composite part 1100 (see Fig.13 ), and operates in pulse echo mode to inspect composite part 1100 at this location. Ultrasonic probe 102 introduces ultrasonic waves 130 into composite part 1100 from front wall 122 (see Fig.12 The ultrasonic wave 130 is reflected back to the ultrasonic probe 102 and converted into a response signal 108. Therefore, the ultrasonic probe 102 receives one or more reflected waves 132 to generate a response signal 108 (step 404). The controller 104 receives the response signal 108 from the ultrasonic probe 102 and stores or buffers the response signal 108. Fig.14 1 is a graph 1400 illustrating response signal 108 in an exemplary embodiment. Graph 1400 illustrates front wall reflection 302 and back wall reflection 504, which represent reflections of ultrasound wave 130 off front wall 122 and back wall 124, respectively. Response signal 108 represents raw A-scan data of composite part 1100 at this location.

[0059] exist Fig.12 , the controller 104 processes the response signal 108 as follows: The controller 104 rectifies the response signal 108 by negative half-wave rectifying and inverting the response signal 108 to generate a rectified signal (step 420). Fig.15 1 is a graph 1500 showing a rectified signal 602 in an exemplary embodiment. The rectified signal 602 includes a series of pulses. The pulse with the first highest peak 610 in the rectified signal 602 (i.e., the front wall pulse 606) represents the front wall reflection 302. Although negative half-wave rectification is used in this embodiment, as described above, other types of rectification may be used.

[0060] exist Fig.12 In step 1204, the controller 104 defines a null gate before the front wall reflection 302 in the rectified signal 602 (step 1202), and makes the rectified signal 602 within the null gate zero (step 1204). Fig.16 1 is a graph 1600 illustrating a null gate 1602 in an exemplary embodiment. The null gate 1602 is used to "zero-out" a portion of the rectified signal that is in the time interval before the front wall reflection 302. Thus, the null gate 1602 begins at a time before the front wall reflection 302 and ends where the front wall reflection 302 begins. For example, the controller 104 can define the end of the null gate 1602 as at the rising edge 920 of the front wall reflection 302 (i.e., at the front wall pulse 606), or where the rising edge 920 of the front wall reflection 302 exceeds a threshold voltage (e.g., 0.4 volts). The controller 104 can also define the start of the null gate 1602 as a number of samples before the rising edge 920 (e.g., 150 samples). The portion of the rectified signal 602 that is within the null gate 1602 is taken to a baseline voltage (eg, zero volts) so that any pulses preceding the front wall reflection 302 are not falsely triggered as the front wall reflection 302 in the rectified signal 602 .

[0061] exist Fig.12 , the controller 104 defines a detection time window 910 or a detection gate (step 1206). Fig.1717 is a graph 1700 showing a detection time window 901 in an exemplary embodiment. As described above, the detection time window 910 is limited or defined to the front wall 122 and the detection gap 210 below the front wall 122. In this embodiment, the controller 104 defines the detection time window 910 to start at the front wall reflection 302 (i.e., at the front wall pulse 606). For example, the detection time window 910 may start at the rising edge 920 of the front wall reflection 302, or where the rising edge 920 of the front wall reflection 302 exceeds a threshold voltage (e.g., 0.4 volts). The detection time window 910 ends at a fixed time after the rising edge 920. Therefore, the detection time window 910 specifically covers the front wall reflection 302 and the near-surface dead zone 304 after the front wall reflection 302. The size of the detection time window 910 in this embodiment can be provided based on the estimated depth 1112 of the resin pool 1104 below the front wall 122. Note that the detection time window 910 may begin before the front wall reflection 302 when the portion of the rectified signal 602 that precedes the front wall reflection 302 is zeroed, as shown in step 1204. Regardless of where the detection time window 910 begins, the detection time window 910 ends at or before the nearest inspectable depth 214 so that only the front wall 122 and the detection gap 210 directly below the front wall 122 are considered.

[0062] exist Fig.12 , controller 104 integrates a portion of rectified signal 602 that is within detection time window 910 (step 408). By integrating within detection time window 910, controller 104 determines an energy sum of the portion of rectified signal 602 that is within detection time window 910. Controller 104 then generates C-scan data 154 based on the energy sum (step 428). For example, controller 104 converts the energy sum at the position into a display value and associates the position data 1010 with the display value. Then, ultrasonic probe 102 is moved to another position relative to front wall 122 of composite part 1100 (step 412), and method 1200 is repeated at the new position.

[0063] After scanning composite part 1100 or at least a portion of composite part 1100 , controller 104 may send C-scan data 154 to a remote device via network interface 1020 for display by the remote device (Step 414 ) or may display C-scan data 154 via user interface 1022 (Step 414 ). Fig.181 is a C-scan presentation 1800 of C-scan data 154 in an exemplary embodiment. C-scan presentation 1800 provides a plan view of composite part 1100 via a point cloud. Because controller 104 integrates a portion of rectified signal 602 within detection signal window 910 at various locations along composite part 1100, C-scan presentation 1800 indicates an anomaly or defect directly below front wall 122 within near-surface dead zone 304. Fig.18 , the darker area illustrates resin pool 1104 below front wall 122. One technical benefit is that even though resin pool 1104 is not visible due to opaque layer 1102 on front wall 122, an operator is able to detect where resin pool 1104 exists in composite part 1100. Another benefit is that because resin pool 1104 can be detected, opaque layer 1102 can be co-cured with composite part 1100 to save manufacturing time.

[0064] Again, although the method 1200 is used to describe the inspection of the composite part 1100, the method can be used to inspect other types of structures. For example, the method 1200 can be used to detect inclusions or voids under the front wall of a metal part.

[0065] The embodiments of the present disclosure may be Fig.19 Aircraft manufacturing and maintenance method 1900 as shown and as Fig. 20 1 and 2. The exemplary method 1900 is described in the context of the illustrated aircraft 2000. During pre-production, exemplary method 1900 may include specification and design 1904 of the aircraft 2000 and material procurement 1906. During production, component and subassembly manufacturing 1908 and system integration 1910 of the aircraft 2000 may occur. Thereafter, the aircraft 2000 may undergo certification and delivery 1912 for placement into service 1914. While in service with a customer, routine maintenance and service 1916 is scheduled for the aircraft 2000 (which may also include modification, reconfiguration, refurbishment, etc.).

[0066] Each of these processes of method 1900 may be performed or implemented by a system integrator, a third party, and / or an operator (e.g., a customer). For the purposes of this description, a system integrator may include, but is not limited to, any number of aircraft manufacturers and main system subcontractors; a third party may include, without limitation, any number of manufacturers, subcontractors, and suppliers; and an operator may be an airline, a leasing company, a military entity, a service organization, and the like.

[0067] like Fig. 20As shown, aircraft 200 produced according to exemplary method 1900 may include fuselage 2002 having multiple systems 2004 and interior 2006. Examples of high-level systems 2004 include one or more of propulsion system 2008, electrical system 2010, hydraulic system 2012, and environmental system 2014. Any number of other systems may be included. Although an aerospace example is shown, the principles described in this specification may be applied to other industries such as the automotive industry.

[0068] During any one or more of these stages of production and maintenance method 1900, apparatus and methods embodied herein may be employed. For example, components or subassemblies corresponding to production process 1908 may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft 2000 is in service. Moreover, during production stages 1908 and 1910, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized, for example, by significantly speeding up assembly of aircraft 2000 or reducing the cost of the aircraft. Similarly, while aircraft 200 is in service, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized, for example and without limitation, to perform maintenance and service 1916.

[0069] Clause 1. An ultrasound inspection system (100), the ultrasound inspection system (100) comprising:

[0070] an ultrasonic probe (102) configured to introduce ultrasonic waves (130) from the front wall (122) into the structure (120) and receive reflected waves (132) to generate a response signal (108); and

[0071] a processor (105) configured to rectify the response signal to generate a rectified signal (602), integrate a portion of the rectified signal within a detection time window (910) to determine an energy sum, and generate an output (150) based on the energy sum;

[0072] The detection time window is defined as a front wall reflection (302) and at least a portion of a near-surface dead zone (304) after the front wall reflection.

[0073] Clause 2. The ultrasound inspection system (100) of clause 1, wherein:

[0074] The processor is configured to negatively half-wave rectify and invert the response signal to generate the rectified signal.

[0075] Clause 3. The ultrasound inspection system (100) of clause 1 or 2, wherein:

[0076] The processor is configured to perform positive half-wave rectification on the response signal to generate the rectified signal.

[0077] Clause 4. The ultrasound inspection system (100) of clause 1, 2 or 3, wherein:

[0078] The processor is configured to full-wave rectify the response signal to generate the rectified signal.

[0079] Clause 5. The ultrasound inspection system (100) of any one of clauses 1 to 4, wherein:

[0080] The processor is configured to define a null gate (1602) before the front wall reflection and to make the rectified signal zero within the null gate.

[0081] Clause 6. The ultrasound inspection system (100) of any one of clauses 1 to 5, wherein:

[0082] The processor is configured to generate C-scan data (154) of the structure based on the energy sum.

[0083] Clause 7. The ultrasound inspection system (100) according to Clause 6, further comprising:

[0084] a robotic arm (1004) configured to move the ultrasound probe over the structure; and

[0085] A position sensor is configured to determine position data of the ultrasound probe.

[0086] Clause 8. The ultrasound inspection system (100) of any one of clauses 1 to 7, wherein:

[0087] The processor is configured to trigger a warning (152) when the energy sum exceeds a threshold.

[0088] Clause 9. The ultrasound inspection system (100) of any one of clauses 1 to 8, wherein:

[0089] The structure includes a composite part (1100).

[0090] Clause 10. The ultrasound inspection system (100) of clause 9, wherein:

[0091] An opaque layer (1102) is disposed on a front wall of the composite part; and

[0092] The detection time window is provided based on the depth (1112) of the resin pool (1104) below the front wall.

[0093] Clause 11. The ultrasound inspection system (100) of any one of clauses 1 to 10, wherein:

[0094] The structure comprises a part of an aircraft (2000).

[0095] Clause 12. A method (400) of inspecting a structure, the method comprising the steps of:

[0096] introducing (402) ultrasonic waves into the structure from the front wall;

[0097] receiving (404) the reflected wave to generate a response signal;

[0098] rectifying (406) the response signal to generate a rectified signal;

[0099] integrating (408) a portion of the rectified signal within a detection time window to determine an energy sum; and

[0100] generating (410) an output based on the energy sum;

[0101] The detection time window is defined as a front wall reflection and at least a portion of a near-surface dead zone after the front wall reflection.

[0102] Clause 13. The method (400) of clause 12, wherein the step of rectifying the response signal comprises:

[0103] The response signal is negatively half-wave rectified and inverted (420) to generate the rectified signal.

[0104] Clause 14. The method (400) of clause 12 or 13, wherein the step of generating an output based on the energy sum comprises:

[0105] C-scan data for the structure is generated (428) based on the energy sum.

[0106] Clause 15. The method (400) of clause 12, 13 or 14, wherein the step of generating an output based on the energy sum comprises:

[0107] When the energy sum exceeds a threshold, a warning is triggered (426).

[0108] Clause 16. The method (400) of any one of clauses 12 to 15, wherein:

[0109] The structure includes composite parts;

[0110] an opaque layer is disposed on the front wall of the composite part; and

[0111] The detection time window is provided based on the depth of the resin pool below the front wall.

[0112] Clause 17. A non-transitory computer-readable medium (106) embodying programming instructions (107) for execution by a processor (105), wherein the instructions direct the processor to implement a method of inspecting a structure (120), the method comprising the steps of:

[0113] introducing ultrasonic waves (130) into the structure from the front wall (122);

[0114] receiving the reflected wave (132) to generate a response signal (108);

[0115] rectifying the response signal to generate a rectified signal (602);

[0116] integrating a portion of the rectified signal within a detection time window (910) to determine an energy sum; and

[0117] generating an output based on the energy sum (150);

[0118] The detection time window is defined as a front wall reflection (302) and at least a portion of a near-surface dead zone (304) after the front wall reflection.

[0119] Clause 18. The computer-readable medium (106) of clause 17, wherein the step of rectifying the response signal comprises:

[0120] The response signal is negatively half-wave rectified and inverted to generate the rectified signal.

[0121] Clause 19. The computer-readable medium (106) of clause 17 or 18, wherein the step of generating an output based on the energy sum comprises:

[0122] C-scan data (154) of the structure is generated based on the energy sum.

[0123] Clause 20. The computer-readable medium (106) of clause 17, 18, or 19, wherein generating an output based on the energy sum comprises:

[0124] When the energy sum exceeds a threshold, an alarm is triggered (152).

[0125] Any element in the various elements shown in the figure or described herein can be implemented as hardware, software, firmware or a certain combination of these.For example, the element can be implemented as special hardware.The special hardware element can be referred to as "processor", "controller" or a similar term.When provided by a processor, the function can be provided by a single special processor, by a single shared processor or by a plurality of separate processors, and some of the separate processors in the plurality of separate processors can be shared.In addition, the term "processor" or "controller" used explicitly should not be interpreted as referring specifically to hardware capable of executing software, but can implicitly include and be not limited to digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC) or other circuit, field programmable gate array (FPGA), read-only memory (ROM) storing software, random access memory (RAM), non-volatile storage device, logic or some other physical hardware component or module.

[0126] Furthermore, an element may be implemented as instructions executable by a processor or computer to perform the function of the element. Some examples of instructions are software, program code, and firmware. The instructions are operable when executed by a processor to direct the processor to perform the function of the element. The instructions may be stored on a storage device that can be read by the processor. Some examples of storage devices are digital or solid-state memory, magnetic storage media such as disks and tapes, hard drives, or optically readable digital data storage media.

[0127] Although specific embodiments are described herein, the scope is not limited to those specific embodiments. Rather, the scope is defined by the following claims and any equivalents thereof.

Claims

1. An ultrasonic inspection system (100), the ultrasonic inspection system (100) comprising: an ultrasonic probe (102) configured to introduce ultrasonic waves (130) from the front wall (122) into the structure (120) and receive reflected waves (132) to generate a response signal (108); and a processor (105) configured to rectify the response signal to generate a rectified signal (602), integrate a portion of the rectified signal within a detection time window (910) to determine an energy sum, and generate an output based on the energy sum; The detection time window is defined as a front wall reflection (302) and at least a portion of a near-surface dead zone (304) after the front wall reflection, wherein the near-surface dead zone (304) is a dead zone generated below the front wall (122) by ringing of a piezoelectric component of the ultrasound probe (102).

2. The ultrasound inspection system (100) according to claim 1, wherein: The processor is configured to negatively half-wave rectify and invert the response signal to generate the rectified signal.

3. The ultrasound inspection system (100) according to claim 1, wherein: The processor is configured to perform positive half-wave rectification on the response signal to generate the rectified signal.

4. The ultrasound inspection system (100) according to claim 1, wherein: The processor is configured to full-wave rectify the response signal to generate the rectified signal.

5. The ultrasonic inspection system (100) according to claim 1 or 2, wherein: The processor is configured to define a null gate before the front wall reflection (1602) and to make the rectified signal zero within the null gate.

6. The ultrasonic inspection system (100) according to claim 1 or 2, wherein: The processor is configured to generate C-scan data of the structure based on the energy sum.

7. The ultrasound inspection system (100) according to claim 6, further comprising: a robotic arm (1004) configured to move the ultrasound probe over the structure; as well as A position sensor is configured to determine position data of the ultrasound probe.

8. The ultrasonic inspection system (100) according to claim 1 or 2, wherein: The processor is configured to trigger a warning when the energy sum exceeds a threshold.

9. The ultrasonic inspection system (100) according to claim 1 or 2, wherein: The structure includes a composite part (1100).

10. The ultrasound inspection system (100) according to claim 9, wherein: An opaque layer (1102) is disposed on a front wall of the composite part; and The detection time window is provided based on the depth (1112) of the resin pool (1104) below the front wall.

11. The ultrasound inspection system (100) according to claim 1 or 2, wherein: The structure comprises a part of an aircraft (2000).

12. A method for inspecting a structure, the method comprising the steps of: directing ultrasonic waves into the structure from the front wall; receiving the reflected wave to generate a response signal; rectifying the response signal to generate a rectified signal; integrating a portion of the rectified signal within a detection time window to determine an energy sum; as well as generating an output based on the energy sum; The detection time window is defined as a front wall reflection and at least a portion of a near-surface dead zone after the front wall reflection, wherein the near-surface dead zone is a dead zone generated below the front wall by ringing of a piezoelectric component of the ultrasound probe.

13. The method according to claim 12, wherein: The step of rectifying the response signal comprises: The response signal is negatively half-wave rectified and inverted to generate the rectified signal.

14. The method according to claim 12 or 13, wherein: The step of generating an output based on the energy sum comprises: C-scan data of the structure is generated based on the energy sum.

15. The method according to claim 12 or 13, wherein: The step of generating an output based on the energy sum comprises: When the energy sum exceeds a threshold, a warning is triggered.

16. The method according to claim 12 or 13, wherein: The structure includes composite parts; an opaque layer is disposed on the front wall of the composite part; and The detection time window is provided based on the depth of the resin pool below the front wall.

17. A non-transitory computer readable medium (106) embodying programming instructions (107) for execution by a processor (105), wherein: The instructions instruct the processor to implement a method for checking a structure (120), the method comprising the following steps: introducing ultrasonic waves (130) into the structure from the front wall (122); receiving the reflected wave (132) to generate a response signal (108); rectifying the response signal to generate a rectified signal (602); integrating a portion of the rectified signal within a detection time window (910) to determine an energy sum; and generating an output based on the energy sum; The detection time window is defined as a front wall reflection (302) and at least a portion of a near-surface dead zone (304) after the front wall reflection, wherein the near-surface dead zone (304) is a dead zone generated below the front wall (122) by ringing of a piezoelectric component of the ultrasound probe.

18. The computer readable medium (106) of claim 17, wherein: The step of rectifying the response signal comprises: The response signal is negatively half-wave rectified and inverted to generate the rectified signal.

19. The computer readable medium (106) of claim 17 or 18, wherein: The step of generating an output based on the energy sum comprises: C-scan data of the structure is generated based on the energy sum.

20. The computer readable medium (106) of claim 17 or 18, wherein: The step of generating an output based on the energy sum comprises: A warning is triggered when the energy sum exceeds a threshold value.

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