Practical Applications Page
VN Instruments has sold ultrasonics equipment into a very wide range of industries and applications. To give an idea of how the technology is used we list some of the applications in use today. If you have any questions about these applications, or think perhaps you have another application to look at, please contact us.
Sample Application: Heat Seal Inspection
Lets look at a specific application, heat seals in food packaging. Food products are now commonly packed in heat sealed pouches. If the heat seal is not properly formed then the contents of the pouch may become contaminated.
So how can a heat seal be inspected using ultrasonics? In this application an air coupled ultrasonic wave is passed through the heat seal region as the food package moves past an industrial sensor head. The SIA-7 system is connected to air coupled transducers on either side of the heat seal. A focused ultrasonic beam passes through the heat seal to measure integrity of the seal. If the bond is secure then the signal can pass through the seal cleanly. Anywhere there is a gap the SIA-7 records a large drop in the signal. Whenever the unit detects a large loss of signal the pouch is rejected. No mess, no fuss! Incidentally this application is currently in use by food packaging facilities around the globe. (www.ptiusa.com)
Solid Fat Content Ultrasonic waves can be used to detect the phase of liquid/solid mixtures of various fats and oils. The methods generally rely on the enormous dynamic range and broad spectral response of the system. As a fat material solidifies the attenuation per unit length tends to increase very rapidly. For conventional ultrasonic gear the limits are quickly reached and so the range of measurements is nearly useless. With our SIA-7 the dynamic range and signal to noise ratio is so great that even at high solid fat contents the system is easily able to make fast and accurate measurements of solid fat content in real time over large distances. This application also applies to the growing area of Biodiesel production.
Level Fill in Aluminium Cans Air coupled ultrasonics has been used to demonstrate a practical and reliable method of doing gross level fill in aluminium beverage cans. The method can scan several thousand cans per minute and requires no harmful X-ray or gamma ray sources.
Delamination in Carbon Composites More and more aircraft manufacturers and even auto makers are using carbon composite materials to create very strong and light weight parts with highly engineered properties. Inspection of carbon composite parts is still a problem especially in post manufacturing and field applications. How is an aircraft wing or car frame inspected if the part has undergone a mechanical shock or stress? The best options are to look for cracks or delaminations in the complex structures by using ultrasonic signals as probes. If the composite structure is properly formed and bonded, the ultrasonic waves pass easily through the material. If the internal joints or structures are weakened then the ultrasonic signals will be strongly attenuated. The SIA-7 system is used to inspect various aerospace components including Carbon Composite Rocket motor nozzles used by IHI (the Japanese equivalent of NASA in the United States).
Crack Detection Crack detection is one of the simplest and best applications for air coupled ultrasonics. In most applications a part of interest is scanned using an XY scanning frame. In ultrasonics such a scan is called a C-Scan. The SIA-7 can be linked directly to an off the shelf scanning system. The unit directly controls the scanning frame and acquires two dimensional image data. Defects in parts are easily detected by simple inspection of the image.
Flow Metering The SIA-7 has been used for several flow meter applications ranging from simple single phase flow in plastic pipes to multiphase flow in a strap on configuration in steel pipes. The SIA-7 can easily be configured to perform Doppler measurements as well as cross correlated results based on signal traveling in opposite directions. A number of different methods and techniques have been successfully implemented. The system has even been used to detect radial vortex flow on the inlet of a working jet engine.
Powder coat thickness Air coupled ultrasonics have been used to measure powder coat thickness on hard substrates. The application uses a single air coupled ultrasonic transducer to parametrically relate powder coat thickness to a measured signal. The method is fast, accurate and suitable for on-line inspection.
Cell Structure in Foam Materials An SIA-7 is used to send a broad spectrum signal through a foam material. The signal gets attenuated as it moves through the foam. The rate at which the signal decays depends on the cell size of the foam and the frequency of the wave. We measure the ultrasonic absorption as a function of frequency. The attenuation as a function of frequency provides immediate feedback regarding cell size and structure.
Thin Films on Aluminium Surface waves launched in thin aluminium have been used to detect the presence or absence of thin coatings on the surfaces over very large distances. The presence of even small amounts of liquid on the surface of the material are easily detectable using air coupled ultrasonics.
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