Miscellaneous Ultrasonic Applications

Background:
While a majority of the applications for ultrasonic nondestructive testing fall into a few well-known categories, the range of possibilities for the technology is large and new tests are constantly being developed and implemented. The applications section of the Olympus website is meant to cover a cross-section of the most common uses for ultrasonic thickness gaging, flaw detection, and material analysis. However, there are also many specialized or unusual applications that fall outside the traditional mainstream areas of weld and structural inspection, corrosion survey, and precision thickness gaging. This application note provides a brief summary of some of the other less common tests that can be performed with our standard commercial equipment. These notes are intended only as a brief introduction to some of the possibilities. For further details about any of the tests that are listed here, including recommended instruments and procedures, please contact us.
 

Animals

One of the earliest "unconventional" applications for ultrasonic thickness gaging, first reported more than forty years ago, was measuring fat and lean meat thickness in living hogs to assess readiness for market. It also readily possible to measure meat thickness in beef cattle and breast meat thickness in poultry using standard instruments with appropriate transducers and setups. In a research environment, marine mammal specialists have used Panametrics-NDT flaw detectors to measure blubber thickness in whales.

Concrete

Testing concrete from one side in a pulse/echo mode usually requires highly specialized, very low frequency ultrasonic or impact/echo equipment that is outside the scope of the Olympus product line. However if access to both sides is available, then conventional flaw detectors and high gain pulser/receivers can be used for through transmission testing to track curing and monitor mechanical properties such as compressive strength. Through transmission penetration through several hundred millimeters of concrete is usually possible.

Cure Rate

Materials like epoxies, adhesives, and the resins used as binders in fiberglass and composites exhibit a significant change in sound velocity as the make the transition between their liquid and solid states. Thus, sound velocity measurement by means of a thickness gage or flaw detector can be used to monitor cure or hardening rate once a calibration curve has been established for a particular material.

Ice

It is possible to measure the thickness of ice from one side using appropriate transducers and instruments, either thickness gages or flaw detectors. Applications have included studies of ice buildup on aircraft wings under laboratory conditions, measurement of ice thickness on ponds and lakes, studies of ice buildup in coolers and other industrial processes, and research analysis of elastic modulus and other material properties in glacial core samples. The limitations on ice measurement are typically surface smoothness and the concentration of air bubbles or cracking within the ice. The latter often presents a significant restriction when measuring thick ice buildups, particularly in nature.

Liquid to Liquid Interfaces

It is possible to ultrasonically measure the depth of one immiscible liquid floating over another, such as a layer of oil over water in a petroleum processing operation. This is normally done with either a thickness gage or a flaw detector, measuring from the echo representing the liquid-to-liquid interface to the air interface above. As with any ultrasonic liquid level measurement the liquid surfaces must be still and free of waves or excessive air bubbles.

Material Analysis

Measurement of sound velocity and attenuation can be used to calculate material properties such as elastic modulus and density variations, as well as grain structure or particle distribution. Degree of modularity in cast iron, polymerization in plastics, moisture content in plastics, mix ratios of liquids, and many other physical properties and process parameters can all be inferred ultrasonically. For further information on this subject, see this paper, An Introduction to Ultrasonic Material Analysis.

Medical and Biological Research Applications

While the industrial ultrasonic products offered by Olympus are not appropriate for medical diagnosis or other clinical uses, our pulser/receivers, transducers, and thickness gages have been employed in a wide variety of biomedical research applications involving both soft and hard tissue. These have included thickness measurements of skin layers, muscle and fat, and corneal tissue, as well as sound velocity measurements that can be related to the integrity of bone. In a manufacturing environment, ultrasonic thickness gages and flaw detectors can be used to help insure quality control of medical devices such as catheter tubing, pacemaker cases, and prostheses and implants, to ensure that dimensions are within critical tolerances.

Minerals, Rocks, Sand, Soil

Research studies into the mechanical properties of geological materials have utilized ultrasonic properties to measure physical parameters such as hardness, elasticity, and grain structure, as well as compaction of soil or sand under laboratory conditions. Prepared specimens are always required, using through-transmission techniques with low frequency transducers and high-gain pulser/receivers. Field tests are normally performed at seismic frequencies well below the ultrasonic range.

Mix Ratio

The mix ratio of two miscible liquids that have dissimilar sound velocities, or the percentage of a solid dissolved in a liquid, can often be correlated to the sound velocity of the resulting solution. The exact correlation in a given case must be determined by testing reference solutions of known composition. Any ultrasonic instrument that is capable of measuring sound velocity across a fixed path can potentially be used. A closely related test involves quantifying the percentage of particulates suspended in a liquid, which may involve attenuation or backscatter measurements as well as sound velocity.

Silicon Wafers

Microelectronics manufacturers have used precision gages such as the Panametrics-NDT Model 35DL for precise thickness measurements on the silicon wafers used in integrated circuit production. It is also possible to find very small cracks in the parts with high resolution acoustic imaging.

Surface Profile/Distance

This application involves precisely measuring the water path from a fixtured transducer to a very small point on the surface of the part. Small changes in the length of the water path indicate changes in the profile of the surface. Depending on the degree of resolution and the data output speed required, this may be done with either a thickness gage or a flaw detector. Complex geometries will typically require automated multi-axis scanning systems for contour-following transducer positioning. A related application, proximity sensing in industrial environments, is normally performed with airborne low frequency sound waves using equipment that is outside the scope of the Olympus product line.

Underwater Measurements

Both thickness gaging and flaw detection can be performed underwater using special waterproof transducers and long cables with standard instruments that remain on deck or on land. Typical applications involve inspections of ship hulls and oil platform supports, or measuring wall thickness of underwater pipelines to check for corrosion. Surface cleaning is required in cases where marine growth is present.

Wood Products

Ultrasonic testing of wood and wood products normally requires low frequency and high power, and is usually performed in a through transmission mode. Applications include detection of hidden internal rot in support pilings and utility poles, verifying bonding in laminated plywood and particle board, and measurement of elastic properties.



For further information on these tests or any other ultrasonic test application, contact us .