Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2003-07-16
2004-04-20
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C073S639000, C073S643000, C073S644000
Reexamination Certificate
active
06722202
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an apparatus and method for inspecting a structure and, more particularly, to an apparatus and method for inspecting a structure that utilizes a driven probe proximate one surface of the structure and a tracking probe proximate the opposed surface of the structure with the driven and tracking probes being magnetically attracted to one another through the structure such that the tracking probe moves in concert with the driven probe as the driven probe is advanced over the structure.
BACKGROUND OF THE INVENTION
Non-destructive inspection of structures involves thoroughly examining a structure without harming the structure or requiring significant disassembly of the structure. Non-destructive inspection is advantageous for many applications in which a thorough inspection of the exterior and/or interior of a structure is required. For example, non-destructive inspection is commonly utilized in the aircraft industry to inspect aircraft structures for any type of internal or external damage to the structure.
Among the structures that are routinely non-destructively tested are composite structures. In this regard, composite structures are commonly used throughout industry because of their engineering qualities, design flexibility and low weight. As such, it is frequently desirable to inspect composite structures to identify any flaws, such as cracks, voids or porosity, which could adversely affect the performance of the composite structure.
Various types of sensors may be utilized to perform non-destructive inspection. One or more sensors may move over the portion of the structure to be examined, and receive data regarding the structure. For example, a pulse-echo, thru-transmission, or shear wave sensor may be utilized to obtain ultrasonic data, such as thickness gauging, detection of laminar defects and porosity, and/or crack detection in the structure. Resonance, pulse echo or mechanical impedance sensors may be utilized to provide indications of voids or porosity, such as in adhesive bondlines of the structure. The data acquired by the sensors is typically processed by a processing, element, and the processed data may be presented to a user via a display.
The non-destructive inspection may be performed manually by technicians who typically move an appropriate sensor over the structure. The manual scanning generally consists of a trained technician holding a sensor and moving the sensor along the structure to ensure the sensor is capable of testing all desired portions of the structure. In many situations, the technician must repeatedly move the sensor side-to-side in one direction while simultaneously indexing the sensor in another direction. For a technician standing beside a structure, the technician may repeatedly move the sensor right and left, and back again, while indexing the sensor between each pass. In addition, because the sensors typically do not associate location information with the acquired data, the same technician who is manually scanning the structure must also watch the sensor display while scanning the structure to determine where the defects, if any, are located in the structure. The quality of the inspection, therefore, depends in large part upon the technician's performance, not only regarding the motion of the sensor, but also the attentiveness of the technician in interpreting the displayed data. Thus, manual scanning-of structures is time-consuming, labor-intensive, and prone to human error.
Automated inspection systems have been developed to overcome the myriad of shortcomings with manual inspection techniques, but the automated systems may sometimes be too expensive, too bulky and/or require access to portions of a structure that are difficult, if not impossible, to access. For example, the AUSS system is a complex mechanical scanning system that employs through-transmission ultrasonic inspection. The AUSS system can also perform pulse echo inspections, and simultaneous dual frequency inspections. The AUSS system has robotically conrtrolled probe arms that must be positioned proximate the opposed surfaces of the structure undergoing inspection with one probe arm moving an ultrasonic transmitter along one surface of the structure, and the other probe arm correspondingly moving an ultrasonic receiver along the opposed surface of the structure. As will be apparent, conventional automated scanning systems, such as the AUSS system, therefore require access to both sides or surfaces of a structure which, at least in some circumstances, will be problematic, if not impossible. In order to maintain the ultrasonic transmitter and receiver in proper alignment and spacing with one another and with the structure undergoing inspection, the AUSS system has a complex positioning system that provides motion control in ten axes. As will be recognized, this requirement that the orientation and spacing of the ultrasonic transmitter and receiver be invariant with respect to one another and with respect to the structure undergoing inspection is especially difficult in conjunction with the inspection of curved structures.
In order to increase the rate or speed at which the inspection of a structure is conducted, the scanning system may include ultrasonic probes that have arrays of ultrasonic transmitters and receivers. As such, the inspection of the structure can proceed more rapidly and efficiently, thereby reducing the costs associated with the inspection. Unfortunately, the use of arrays of ultrasonic transmitters and receivers is generally impractical during the scanning of curved structures, such as large-scale curved composite structures. In this regard, conventional ultrasonic scanning systems for inspecting large-scale curved composite parts utilize water jets to provide water between the surface of the structure undergoing inspection and the ultrasonic transmitter or receiver in order to effectively couple ultrasonic signals into and out of the structure. In instances in which the ultrasonic probes include an array of ultrasonic transmitters or receivers, it has been difficult to design a corresponding water jet array that does not produce significant interference or crosstalk between the elements of the array.
BRIEF SUMMARY OF THE INVENTION
In light of the foregoing background, an improved apparatus and method for inspecting a structure, such as a composite structure and, in particular, a curved composite structure, are provided according to the various embodiments of the present invention. Although the method and apparatus of the present invention utilize probes including respective sensing elements, such as respective ultrasonic transducers, that are disposed proximate the opposed surfaces of a structure, only one of the probes need be driven, such as by means of a robotic arm or the like. Thus, the method and apparatus of the present invention are advantageously adapted to inspect structures in which a surface of the structure is relatively inaccessible, at least for a robotic arm or the like. Additionally, embodiments of the method and apparatus of the present invention are capable of operating in an ultrasonic array mode, even in conjunction with the inspection of curved structures, thereby increasing the speed and efficiency with which such structures may be inspected and correspondingly reducing the cost associated with the inspection. Further, embodiments of the method and apparatus of the present invention permit the probes to contact and ride along the respective surfaces of the structure, thereby reducing the necessary sophistication of the motion control system that is otherwise required by conventional scanning systems in order to maintain the ultrasonic probes in a predefined orientation and at a predefined spacing from the respective surface of a structure undergoing inspection.
The apparatus of the present invention includes a driven probe disposed proximate a first surface of the structure and a tracking probe disposed proximate an opposed second surface of the structure. The dr
Kennedy James C.
Mares Christopher L.
Negley Mark A.
Saint-Surin Jacques M.
The Boeing Company
Williams Hezron
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