Patent Publication Number: US-9885628-B2

Title: Radiographic method and apparatus for detection of cracks, defects, or leak pathways in materials and assemblies

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present disclosure is a continuation of U.S. patent application Ser. No. 15/062,166, filed on Mar. 6, 2016, the entire contents of which are herein incorporated by reference. 
    
    
     FIELD 
     The present disclosure relates generally to radiographic systems and methods for inspecting materials and assemblies, and more particularly, to radiographic systems and methods for detecting voids, cracks, or other defects in materials and assemblies. 
     BACKGROUND 
     Proof testing is a nondestructive testing technique for verifying that a part, component, or assembly is suitable to withstand the conditions in which the part, component, or assembly was designed to operate. By way of example, proof testing may involve subjecting a part to twice the part&#39;s maximum design load and observing whether the part is damaged in any way. Manufacturers in many industries use proof testing as way to screen a part for manufacturing anomalies before the part is allowed to pass “inspection” and enter service. Similarly, proof testing may also be used to verify that an old part is still functioning properly and is fit for additional service. 
     In some examples, a part may “pass” proof testing but nevertheless include one or more latent defects. For instance, the proof test might not detect an inconsistency that could cause the part to not be able to sustain a particular design load. Such latent defects may take the form of internal voids, cracks, or other defects that might not be observable from viewing the part&#39;s surface. Further, a latent defect might not be detectable using x-ray or ultrasound inspection either. For example, due to the geometry or variable density of the part, x-ray inspection might not be able to detect or reveal a crack in the part. Additionally, x-ray inspection might not be able to detect a crack that is oriented orthogonal to an x-ray detector array. As another example, geometric/material inhomogeneity or latent defects may create additional echoes or shadows, making ultrasound or x-ray data expensive to analyze and making detection of inconsistencies/defects difficult. 
     SUMMARY 
     In one example, a method for testing a part is provided. The method includes exposing the part to a radioactive or isotope-labeled fluid under pressure, and, after exposing the part to the radioactive or isotope-labeled fluid under pressure, detecting a presence or absence of radioactivity or the isotope-labeled fluid entrained in the part. 
     In another example, a system for testing a part is provided. The system comprises a chamber configured to accept the part. The system further comprises a vacuum source connected to the chamber. The system also comprises a fluid source connected to the chamber and configured to provide a radioactive or isotope-labeled fluid to the chamber. Additionally, the system comprises a detector configured to detect a presence or absence of radioactivity or the isotope-labeled fluid in the part. 
     In still another example, a controller is provided. The controller comprises a processor and a computer-readable medium having stored therein instructions that are executable to cause the controller to perform functions. The functions include causing a vacuum source to reduce a pressure in a chamber, with a part located in the chamber. The functions also include causing a fluid source connected to the chamber to provide a radioactive or isotope-labeled fluid to the chamber. The functions further include causing a fluid reclamation container to remove the radioactive or isotope-labeled fluid from the chamber. And the functions include causing a detector to detect a presence or absence of radioactivity or the isotope-labeled fluid in the part. 
     The features, functions, and advantages that have been discussed can be achieved independently in various examples or may be combined in yet other examples further details of which can be seen with reference to the following description and figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The novel features believed characteristic of the illustrative examples are set forth in the appended claims. The illustrative examples, however, as well as a preferred mode of use, further objectives and descriptions thereof, will best be understood by reference to the following detailed description of an illustrative example of the present disclosure when read in conjunction with the accompanying figures, wherein: 
         FIG. 1  is a schematic diagram of an example system according to the disclosure. 
         FIG. 2  is a schematic diagram of an example controller according to the disclosure. 
         FIG. 3  is a flowchart of an example method for testing a part according to the disclosure. 
         FIG. 4  is a flowchart of another example method for testing a part according to the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed examples will now be described more fully hereinafter with reference to the accompanying figures, in which some, but not all of the disclosed examples are shown. Indeed, several different examples may be provided and should not be construed as limited to the examples set forth herein. Rather, these examples are provided so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art. 
     Within examples, radiographic systems and methods for inspecting materials and assemblies are provided. For instance, the systems and methods may facilitate detecting voids, cracks, or other defects in materials and assemblies. As described herein, the systems and methods leverage the ability of a radioactive or isotope-labeled fluid to permeate through a material or assembly in order to detect the presence or absence of internal defects in the material or assembly. The systems and methods described herein may facilitate detecting defects, such as cracks or voids in parts with complex shape geometries or multiple density/inhomogeneous constituents. 
     Advantageously, the systems and methods may detect the presence or absence of internal defects without applying loads or pressure (beyond the design loads) on the materials or assemblies. The systems and methods provide an alternative to proof testing. Further, the systems and methods may also facilitate detecting internal cracks or voids that might not otherwise be detectable using other or cost-effective detection techniques. For example, the systems and methods may facilitate detecting latent defects in a part that might not be visible with x-ray inspection due to the orientation of the defect with respect to the detector array or the size and shape of the defect. As another example, the systems and methods may facilitate detecting latent defects in a part that might not be observable with ultrasonic inspection due to the inability of a part to withstand exposure to ultrasound techniques or due to uninterpretable ultrasonic echoes or shadows caused by the geometry or material(s) of the part. 
     In accordance with examples disclosed herein, an example system includes a chamber, a vacuum source, a fluid source, and a detector. The chamber may be configured to accept a part. For example, the chamber may be an autoclave. The vacuum source may be connected to the chamber and may be configured to remove gas molecules from the chamber and create a partial vacuum in the chamber. The fluid source may also be connected to the chamber and configured to provide a radioactive or isotope-labeled fluid to the chamber. By way of example, after creating a partial vacuum in the chamber and while the part is in the chamber, the fluid source may provide the radioactive or isotope-labeled fluid to the chamber. 
     Within the chamber, the radioactive or isotope-labeled fluid may then permeate through the part. For instance, the part may have a permeable surface or the part may be a polymeric composite or polymeric part, thereby being permeable to the radioactive or isotope-labeled fluid, which can permeate through the part. If the part includes any internal cracks or voids, the radioactive or isotope-labeled fluid may then permeate into the cracks or voids and become entrained or trapped within the defects. The presence of the entrained fluid may then detectable by an x-ray detector, for instance. 
     The detector may then be used to detect a presence or absence of radioactivity or the isotope-labeled fluid in the part. By way of example, if the part was exposed to a radioactive fluid, the detector may be configured to detect the presence or absence of radioactivity entrained in the part. On the other hand, if the part was exposed to an isotope-labeled fluid, the detector may be configured to detect the presence or absence of the isotope-labeled fluid entrained in the part. In one example, the detector may be connected to the chamber and configured to detect the presence or absence of radioactivity or the isotope-labeled fluid after removal of the radioactive or isotope-labeled fluid from the chamber. Alternatively, the detector may be separate from the chamber and the part may be removed from the chamber to a location of the detector. In one example, the detector may be an x-ray detector. 
     If the detector detects the presence of radioactivity or the isotope-labeled fluid (e.g., more than a threshold detectable amount of radioactivity or more than a threshold amount of isotope-labeled fluid), the presence of the radioactivity or the isotope-labeled fluid may be interpreted to mean that the part potentially contains a latent defect. For example, the detector may detect radioactivity or isotope-labeled fluid entrained within the part or emanating from a void or crack within the part. On the other hand, if the detector detects an absence of radioactivity or absence of the isotope-labeled fluid (e.g., less than a threshold concentration), the absence of the radioactivity or isotope-labeled fluid may be interpreted to mean that the part does not include any significant latent defects. 
     Various other features of the example system discussed above, as well as methods for testing a part using these systems, are also described hereinafter with reference to the accompanying figures. 
     Referring to the figures,  FIG. 1  is a schematic diagram of an example system  100 . In line with the discussion above, the example system  100  may be used to test a part. As shown in  FIG. 1 , the example system  100  includes a chamber  102 , a vacuum source  104 , a fluid source  106 , a fluid reclamation container  108 , a detector  110 , a controller  112 , and an indicator  114 . 
     As shown in  FIG. 1 , the controller  112  may be coupled to the vacuum source  104 , fluid source  106 , fluid reclamation container  108 , detector  110 , and indicator  114  via one or more wired or wireless links, system buses, networks, or other connection mechanisms  116 . In addition, each of the vacuum source  104 , fluid source  106 , and fluid reclamation container  108  may be coupled to the chamber via fluid pathways  118 ,  120 ,  122 . Further, the fluid source  106  may be coupled to the fluid reclamation container  108  via a fluid pathway  124 . 
     The chamber  102  may be configured to accept a part. In one example, the chamber  102  may be an autoclave. More generally, the chamber  102  may be any cavity or space that may enclose a part and be sealed for a period of time. For example, the chamber  102  may have a pressure-tight lid or door that may be opened to insert a part and closed to facilitate exposing the part to a radioactive or isotope-labeled fluid under pressure. 
     The vacuum source  104  may be connected to the chamber  102  and configured to regulate the pressure in the chamber  102 . In particular, the vacuum source  104  may be configured to create a partial vacuum in the chamber  102  by removing gas molecules from the chamber  102 . By way of example, the vacuum source  104  may be a vacuum pump. In an example in which the chamber  102  is an autoclave, the vacuum source  104  may be an integrated component of the autoclave. 
     The fluid source  106  may be configured to provide a radioactive or isotope-labeled fluid to the chamber  102 . In one example, the fluid source  106  may store the radioactive or isotope-labeled fluid and include a valve for releasing the radioactive or isotope-labeled fluid into the chamber  102  via the fluid pathway  120 . The radioactive or isotope-labeled fluid may take any of a variety of forms, depending on the desired configuration. The fluid source  106  may provide a radioactive gas, such as radon, radioactive helium, or radioactive xenon. Alternatively, the fluid source  106  may provide a radioactive liquid. The isotope-labeled fluid may be radioactive or non-radioactive. Further the isotope-labeled fluid may be a liquid (e.g., deuterated water) or a gas (e.g., deuterated methane or helium-3). 
     Once the fluid source  106  provides the radioactive or isotope-labeled fluid to the chamber  102 , the radioactive or isotope-labeled fluid may permeate into the part. The amount of time that the part is exposed to the radioactive or isotope-labeled fluid in the chamber may vary, depending on the desired configuration. In practice, the permeation of the radioactive or isotope-labeled fluid is related to the concentration gradient of the radioactive or isotope-labeled gas, the location of the defect, and the part&#39;s intrinsic permeability. The permeation of the fluid through the part could be modeled using Fick&#39;s laws of diffusion, and exposure times may be calculated accordingly. Deviations from obedience to Fick&#39;s law may be an indication of the location of defects in the part. 
     The fluid reclamation container  108  may be configured to remove the radioactive or isotope-labeled fluid from the chamber after the permeation. By way of example, the fluid reclamation container  108  may include a vacuum pump and cooler configured to reclaim the radioactive or isotope-labeled fluid from the chamber  102  and a storage container configured to store the radioactive or isotope-labeled fluid. The fluid reclamation container  108  may take other forms as well. 
     In some instances, the radioactive or isotope-labeled fluid may be recycled for use in subsequent testing. For example, the fluid reclamation container  108  may collect the radioactive or isotope-labeled fluid, and during a subsequent test, the fluid source  106  may provide the collected radioactive or isotope-labeled to the chamber  102  via the pathways  120  and  124 . In other instances, the radioactive or isotope-labeled fluid reclaimed by the reclamation container  108  may be discarded and might not be reused. 
     The detector  110  may be configured to detect a presence or absence of radioactivity or isotope-labeled fluid in the part. By way of example, if the part was exposed to a radioactive fluid, the detector may be configured to detect a presence or absence of radioactivity entrained in the part. On the other hand, if the part was exposed to an isotope-labeled fluid, the detector may be configured to detect a presence or absence of the isotope-labeled fluid entrained in the part. The detector may be an x-ray detector (e.g., a digital x-ray detector or a Geiger counter). 
     The detector may be connected to the chamber and configured to detect the presence or absence of radioactivity or the isotope-labeled fluid entrained in the part after removal of the radioactive or isotope-labeled fluid from the chamber. The detector may be separate from the chamber (not shown) and configured to detect the presence or absence of the radioactivity or isotope-labeled fluid entrained in the part after removal of the part from the chamber 
     The controller  112  may be configured to control one or more of the vacuum source  104 , fluid source  106 , fluid reclamation container  108 , detector  110 , and indicator  114  in order to carry out testing of a part in accordance with the methods described herein. By way of example, the controller  112  may be configured to send instructions to the vacuum source  104  causing the vacuum source to create a partial vacuum in the chamber  102 . The controller may also be configured to send instructions to the fluid source  106  causing the fluid source  106  to provide a radioactive or isotope-labeled fluid to the chamber  102 . Additionally, the controller may be configured to send instructions to the fluid reclamation container  108  causing the fluid reclamation container  108  to reclaim the radioactive or isotope-labeled fluid from the chamber  102 . The controller  112  may also be configured to send instructions to the detector  110  causing the detector to detect a presence or absence of radioactivity or isotope-labeled fluid entrained in the part. 
     One or more of the vacuum source  104 , fluid source  106 , fluid reclamation container  108 , and detector  110  may be controlled manually (e.g., by an operator) without being controlled by the controller  112 . Alternatively, the controller  112  and the indicator  114  may be omitted from the system  100  altogether (not shown). 
     In some examples, the controller  112  may be configured to receive data from the detector  110  indicating a presence or absence of radioactivity or isotope-labeled fluid, and send instructions to the indicator  114  causing the indicator  114  to provide an indication of the presence or absence of the radioactivity or isotope-labeled fluid in the part. 
     The indicator  114  may function to provide an output that is indicative of the presence or absence of radioactivity or isotope-labeled fluid in a part. As such, the indicator  114  may comprise a light source (e.g., a light emitting diode) that is configured to provide a green or red light, depending on whether the radioactivity or isotope-labeled fluid is present. Alternatively, the indicator  114  may comprise an electroacoustic transducer (e.g., a speaker) that is configured to provide an audible noise or alarm when radioactivity or isotope-labeled fluid is present. The indicator  114  may take other forms as well. The indicator  114  may be an integrated component of the controller  112 . 
       FIG. 2  is a schematic diagram of an example controller  200 . The controller  200  in  FIG. 2  may represent the controller  112  (see  FIG. 1 ). The controller  200  may be or include a computer, mobile device, or similar device that may be configured to perform the functions described herein. 
     As shown in  FIG. 2 , the controller  200  may include one or more processors  202 , a memory  204 , a communication interface  206 , a display  208 , and one or more input devices  210 . Components illustrated in  FIG. 2  may be linked together by a system bus, network, or other connection mechanism  212 . The controller  200  may also include hardware to enable communication within the controller  200  and between the controller  200  and one or more other devices, such as any of the components of the system  100  (see  FIG. 1 ). The hardware may include transmitters, receivers, and antennas, for example. 
     The one or more processors  202  may be any type of processor, such as a microprocessor, digital signal processor, multicore processor, etc., coupled to the memory  204 . The memory  204  may be any type of memory, such as volatile memory like random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), or non-volatile memory like read-only memory (ROM), flash memory, magnetic or optical disks, or compact-disc read-only memory (CD-ROM), among other devices used to store data or programs on a temporary or permanent basis. 
     Additionally, the memory  204  may be configured to store program instructions  214 . The program instructions  214  may be executable by the one or more processors  202 . For instance, the program instructions  214  may be executable to cause a vacuum source to reduce a pressure in a chamber, cause a fluid source connected to the chamber to provide a radioactive or isotope-labeled fluid to the chamber, cause a fluid reclamation container to remove the radioactive or isotope-labeled fluid from the chamber, and/or cause a detector to detect a presence or absence of radioactivity or isotope-labeled fluid in a part. The program instructions  214  may also be executable to cause the one or more processors  202  to perform other functions, such as any of the functions described herein. 
     The communication interface  206  may be configured to facilitate communication with one or more other devices, in accordance with one or more wired or wireless communication protocols. For example, the communication interface  206  may be configured to facilitate wireless data communication for the controller  200  according to one or more wireless communication standards, such as one or more IEEE 802.11 standards, ZigBee standards, Bluetooth standards, etc. As another example, the communication interface  206  may be configured to facilitate wired data communication with one or more other devices. 
     The display  208  may be any type of display component configured to display data. As one example, the display  208  may include a touchscreen display. As another example, the display may include a flat-panel display, such as a liquid-crystal display (LCD) or a light-emitting diode (LED) display. 
     The one or more input devices  210  may include one or more pieces of hardware equipment used to provide data and control signals to the controller  200 . For instance, the one or more input devices  210  may include a mouse or pointing device, a keyboard or keypad, a microphone, a touchpad, or a touchscreen, among other possible types of input devices. 
       FIG. 3  is a flowchart of an example method for testing a part. Method  300  shown in  FIG. 3  presents a method that, for example, could be used with the system  100  (see  FIG. 1 ), or any of the systems disclosed herein. Example devices or systems may be used or configured to perform logical functions presented in  FIG. 3 . In some instances, components of the devices and/or systems may be configured to perform the functions such that the components are actually configured and structured (with hardware and/or software) to enable such performance. In other examples, components of the devices and/or systems may be arranged to be adapted to, capable of, or suited for performing the functions. Method  300  may include one or more operations, functions, or actions as illustrated by one or more of blocks  302 - 310 . Although these blocks are illustrated in a sequential order, these blocks may also be performed in parallel, and/or in a different order than those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or removed based upon the desired implementation. 
     It should be understood that for this and other processes and methods disclosed herein, flowcharts show functionality and operation of one possible implementation of present disclosure. In this regard, each block may represent a module, a segment, or a portion of program code, which includes one or more instructions executable by a processor for implementing specific logical functions or steps in the process. The program code may be stored on any type of computer readable medium or data storage, for example, such as a storage device including a disk or hard drive. The computer readable medium may include non-transitory computer readable medium or memory, for example, such as computer readable media that stores data for short periods of time like register memory, processor cache, and RAM. The computer readable media may also be any other volatile or non-volatile storage systems. The computer readable medium may be considered a tangible computer readable storage medium, for example. 
     In addition, each block in  FIG. 3  may represent circuitry that is wired to perform the specific logical functions in the process. Alternative implementations are included within the scope of the examples of the present disclosure in which functions may be executed out of order from that shown or discussed, including substantially concurrent or in reverse order, depending on the functionality involved. 
     Initially, at block  302 , the method  300  includes exposing a part to a vacuum. In line with the discussion above, the part may be placed in a chamber, and a vacuum source may create a partial vacuum in the chamber. The part may be exposed to a vacuum in an autoclave. 
     At block  304 , the method  300  includes exposing the part to a radioactive or isotope-labeled fluid under pressure. As discussed above, a fluid source may provide the radioactive or isotope-labeled fluid to a chamber in which the part is located. The radioactive or isotope-labeled fluid may be a gas or a liquid. Within the chamber, the radioactive or isotope-labeled fluid may then permeate into any cracks or voids within the part. The pressure within the voids or cracks may be less than the pressure within the chamber. Thus, the radioactive or isotope-labeled fluid may tend to permeate be retained in the voids or cracks. 
     At block  306 , the method  300  includes reclaiming the radioactive or isotope-labeled fluid from the chamber. In line with the discussion above, the radioactive or isotope-labeled fluid may be removed from the chamber and collected. Optionally, the radioactive or isotope-labeled fluid may be recycled and used again during subsequent testing. 
     At block  308 , the method  300  includes detecting a presence or absence of radioactivity or the isotope-labeled fluid entrained in the part. By way of example, if the part was exposed to a radioactive fluid at block  304 , then the detector may be configured to detect a presence or absence of radioactivity entrained in the part. On the other hand, if the part was exposed to an isotope-labeled fluid at block  304 , then the detector may be configured to detect a presence or absence of the isotope-labeled fluid entrained in the part. The detector may detect a concentration of radioactivity or isotope-labeled fluid. For instance, a Geiger counter may determine the concentration. The detector or a separate controller may then determine whether the concentration satisfies a predetermined criterion. For instance, the detector or controller may compare the detected concentration to a threshold concentration. 
     In another example, a digital x-ray detector may generate an image of the part. If there is any radioactivity or isotope-labeled fluid entrained in the part, the radioactivity or isotope-labeled fluid may be observable in the image. The digital x-ray detector may generate the image without using an x-ray source. The digital x-ray detector or a separate controller may then analyze the image to determine whether the image is indicative of the presence of radioactive or isotope-labeled fluid in the part. Alternatively, a technician may review the image to determine whether the image is indicative of the presence of radioactivity or isotope-labeled fluid in the part. 
     At block  310 , the method  300  includes providing an indication of the presence or absence of the radioactivity or the isotope-labeled fluid entrained in the part. For example, if the detector is configured to detect a presence or absence of radioactivity, an indicator may provide a green indication indicating the absence of radioactivity and that the part does not appear to include any latent defects. Alternatively, the indicator may provide a red indication indicating the presence of radioactivity and that the part appears to have a sub-surface latent defect. Similarly, if the detector is configured to detect a presence or absence of isotope-labeled fluid, an indicator may provide a green indication indicating the absence of isotope-labeled fluid (e.g., less than a threshold detectable concentration), or provide an indication indicating the presence of the isotope-labeled fluid. 
     In response to detecting the presence of radioactivity or isotope-labeled fluid, the method  300  may further include testing the part using a secondary inspection technique. Examples of secondary inspection techniques include x-ray detection, magnetic resonance imaging (MRI), and computerized axial tomography (CAT) scanning, among others. The secondary inspection technique may be used to visualize any latent defects within the part. 
       FIG. 4  is a flowchart of another example method for evaluating a surface of an object. Method  400  may include one or more operations, functions, or actions as illustrated by blocks  402 - 416  of the flowchart. Although the blocks are illustrated in a sequential order, these blocks may also be performed in parallel, and/or in a different order than those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or removed from the flowchart, based upon the desired implementation of the method  400 . Each block may represent a module, segment, or a portion of program code, which includes one or more instructions executable by a processor for implementing specific logical functions or steps in the process. In addition, each block in  FIG. 4  may represent circuitry that is wired to perform the specific logical functions in the process. 
     Initially, at block  402 , the method  400  involves exposing a part to a vacuum in a chamber. At block  404 , the method  400  involves exposing the part to a radioactive or isotope-labeled fluid in the chamber. At block  406 , the method  400  involves reclaiming the radioactive or isotope-labeled fluid from the chamber. 
     Further, at block  408 , the method  400  involves detecting a presence or absence of radioactivity or the isotope-labeled fluid entrained in the part. If radioactivity or isotope-labeled fluid is present, then at block  412 , the method  400  involves providing a presence indication, and, at block  414 , the method  400  involves testing the part using a secondary inspection technique. Whereas, if radioactivity or isotope-labeled fluid is absent, then, at block  416 , the method  400  involves providing an absence indication, and an operator may then proceed to testing another part. 
     The description of the different advantageous arrangements has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the examples in the form disclosed. After reviewing and understanding the foregoing disclosure, many modifications and variations will be apparent to those of ordinary skill in the art. Further, different examples may provide different advantages as compared to other examples. The example or examples selected are chosen and described in order to best explain the principles, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various examples with various modifications as are suited to the particular use contemplated.