The present invention relates to field of non-destructive ultrasonic testing and, more particularly, to devices used to control such testing.
Because of their lighter weight, composite materials, such as epoxy resins, are replacing aluminum as material for use in manufacturing aircraft parts and other equipment. Parts made of such composite materials, however, require careful inspection before installation in an aircraft. Ultrasonics is a widely used method of non-destructive inspection of such parts.
Because every portion of a part must be examined, ultrasonic inspection systems require a large number of transducers in order to keep the inspection time per unit at an acceptable value. Depending on the part being inspected, different modes of ultrasonic inspection may be required. For example, with through transmission ultrasonics (TTU), one transducer transmits ultrasonic energy through a part and another transducer receives and converts the portion of that energy that is not reflected by the part. If there is no defect in the interior of the part, then the magnitude of ultrasonic energy received in a time window corresponding to the part thickness will exceed a preset threshold value. If the magnitude of the received energy is too low, then a defect was present in the interior of the part.
Another ultrasonic inspection mode is the pulse echo (PE) technique. For this technique, a single transducer both transmits ultrasonic energy to the part under test and receives reflections of that energy from the part. By examining the magnitude of reflections during a time period when reflections from the interior of the part under investigation are received (i.e., a time window), one can determine whether there is a reflection defect (a reflection magnitude above a threshold), or whether there is no defect (a reflection magnitude below the threshold).
A variation on the PE mode is the loss-of-back (LOB) mode. As in the PE mode, the LOB mode uses a single transducer to transmit and receive ultrasonic energy. In this case, however, the time window is set to receive reflections from the rear surface. When defects are present in the interior of the part they reflect much of the ultrasonic energy, causing the magnitude of the reflections from the rear surface to be below a threshold. The LOB detecting apparatus thus indicates the presence of a defect. By the same token, if the magnitude of rear surface reflections exceeds the threshold, then the LOB detecting apparatus indicates no defects.
In conventional ultrasonic control systems, each transducer channel requires a separate gate for processing. As used in this specification, a "transducer channel" refers to a single transmission path to and from one or more transducers which cooperate with each other in ultrasonic detection. For example, in the PE or LOB modes, a transducer channel would correspond to a single transducer, whereas in the TTU mode, a transducer channel would correspond to both the transmitting and receiving transducers. The term "gate" as used in this specification specifies a subsystem which processes ultrasonic signals received via a transducer channel. For example, TTU, PE or LOB gates process the corresponding ultrasonic signals in accordance with the TTU, PE, or LOB modes, respectively.
Conventional ultrasonic testing systems require a gate for each channel, and are thus not only very complex, but become very large and expensive when several transducers are used, such as in testing large and complicated aircraft parts. Furthermore, conventional systems require a complete reconfiguration when the ultrasonic testing requirements change.
One object of this invention is to simplify ultrasonic testing equipment by allowing relatively few gates to service several transducer channels.
Another object of this invention is a simple and relatively inexpensive means of reconfiguring an ultrasonic test system.
Additional objects and advantages of the present invention will be set forth in part in the description which follows and in part will be obvious from that description or may be learned by the practice of the invention. The objects and advantages of the invention may be realized and attained by the methods and apparatus defined in the appended claims.