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Ultrasonic inspection refers to some sort of nondestructive screening technique which inspects any work piece and resources by ultrasonic and the help of an ultrasonic designed detector. When these kinds of ultrasonic waves which are inside the materials to be inspected meet the defects, a part of the waves will mirror, then this receptor analyzes all the reflection waves thus finding out the present defects. All the present defects are detected precisely.
This method can also screen the placement and dimensions of defects within, or be used to find out the thickness of supplies. The benefits of this method are apparent. The penetrating capability of the technique is fantastic. And also, the flaw inspection sensitivity is large, especially for plane kind defects including, cracks, sandwich and different others.
Automated systems can either be squirter systems or submerged reflector plate systems. Squirter systems, the most frequently used in production, are usually large gantry systems with as much as a 7 axis scanning bridge. They are computer controlled to track the contour of the part and keep the transducers normal to the surface. They also index at the end of each scan pass.
During the process, carbon or epoxy laminates are usually scanned at around 5 MHz while honeycomb assemblies require lower frequencies (1 or 2.25 MHz) to penetrate the thicker structure. Foam filled structures require even lower frequencies with 250 kHz, 500 kHz or 1 MHz being typical.
There are also special units for cylindrical parts that contain turntables that rotate during the scanning operation. The output from these automated units is displayed as a C-scan, which is a planar map of the part, where light (white) areas indicate less sound attenuation and are of higher quality than darker areas (gray to black) that indicate more sound attenuation and are of lower quality. The darker the area, the more severe sound attenuation is and the poorer the quality of the part.
In the entire transmission method, a transmitting transducer generates a longitudinal ultrasonic wave that travels through the laminate. It is then received by a receiving transducer placed on the opposite side of any part. If the part contains a defect, such as porosity or a delamination, some or all of the sound will be either absorbed or scattered so that some or all of the sound is not received by the receiving transducer.
Laser heating at the surface causes a temperature increase and a resultant local expansion of the material. If the laser pulses are short (10-100 ns), the expansion will create a wave in the 1-10 MHz range. The receiving laser detects light scattered off the surface that is analyzed by a Fabry-Perot interferometer to extract the its signal. In this process, it is important to generate as much ultrasound as possible without causing heat damage to the composite surface.
Surface temperatures are normally restricted to a given temperature. An additional benefit of laser ultrasonic inspection is that the ultrasound propagates perpendicular to the surface somewhat independent of the laser angle of incidence. The transmitters and receivers can be off axis to normal at a specified angle without loss of performance. However, since the part must have a thin layer of resin on the surface for effective sound generation, resin starved or machined surfaces may limit the success of the technique.
This method can also screen the placement and dimensions of defects within, or be used to find out the thickness of supplies. The benefits of this method are apparent. The penetrating capability of the technique is fantastic. And also, the flaw inspection sensitivity is large, especially for plane kind defects including, cracks, sandwich and different others.
Automated systems can either be squirter systems or submerged reflector plate systems. Squirter systems, the most frequently used in production, are usually large gantry systems with as much as a 7 axis scanning bridge. They are computer controlled to track the contour of the part and keep the transducers normal to the surface. They also index at the end of each scan pass.
During the process, carbon or epoxy laminates are usually scanned at around 5 MHz while honeycomb assemblies require lower frequencies (1 or 2.25 MHz) to penetrate the thicker structure. Foam filled structures require even lower frequencies with 250 kHz, 500 kHz or 1 MHz being typical.
There are also special units for cylindrical parts that contain turntables that rotate during the scanning operation. The output from these automated units is displayed as a C-scan, which is a planar map of the part, where light (white) areas indicate less sound attenuation and are of higher quality than darker areas (gray to black) that indicate more sound attenuation and are of lower quality. The darker the area, the more severe sound attenuation is and the poorer the quality of the part.
In the entire transmission method, a transmitting transducer generates a longitudinal ultrasonic wave that travels through the laminate. It is then received by a receiving transducer placed on the opposite side of any part. If the part contains a defect, such as porosity or a delamination, some or all of the sound will be either absorbed or scattered so that some or all of the sound is not received by the receiving transducer.
Laser heating at the surface causes a temperature increase and a resultant local expansion of the material. If the laser pulses are short (10-100 ns), the expansion will create a wave in the 1-10 MHz range. The receiving laser detects light scattered off the surface that is analyzed by a Fabry-Perot interferometer to extract the its signal. In this process, it is important to generate as much ultrasound as possible without causing heat damage to the composite surface.
Surface temperatures are normally restricted to a given temperature. An additional benefit of laser ultrasonic inspection is that the ultrasound propagates perpendicular to the surface somewhat independent of the laser angle of incidence. The transmitters and receivers can be off axis to normal at a specified angle without loss of performance. However, since the part must have a thin layer of resin on the surface for effective sound generation, resin starved or machined surfaces may limit the success of the technique.
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