Ultrasonic Testing Services

Ultrasonic testing is often performed on steel and other metals and alloys, though it can also be used on concrete, wood, and composites, albeit with less resolution. It is used in many industries including steel and aluminum construction, metallurgy, manufacturing, aerospace, automotive, and other transportation sectors.
Ultrasonic methods of NDT use beams of mechanical waves (vibrations) of short wavelength and high-frequency, transmitted from a small probe and detected by the same or other probes. Such mechanical waves can travel large distances in fine-grain metal, in the form of a divergent wave with progressive attenuation. The frequency is in the range of 0.1 to 20 MHz and the wavelength in the range 1 to 10mm. The velocity depends on the material and is in the range of 1000-6000 m/s.In ultrasonic testing, an ultrasound transducer connected to a diagnostic machine is passed over the object being inspected. The transducer is typically separated from the test object by a Couplant (such as oil) or by water, as in immersion testing. However, when ultrasonic testing is conducted with an Electromagnetic Acoustic Transducer the use of Couplant is not required.The technique detects internal, hidden discontinuities that may be deep below the surface. Transducers and coupling wedges are available to generate waves of several types, including longitudinal, shear, and surface waves. Applications range from thickness measurements of thin steel plates to internal testing of large turbine rotors.Most non-porous, resilient materials used for structural purposes (steel, aluminum, titanium, magnesium, and ceramics) can be penetrated. Even large cross-sections can be tested successfully for minute discontinuities.Ultrasonic testing techniques are widely accepted for quality control and materials testing in many industries, including electric power generation, production of steel, aluminum, and titanium, in the fabrication of airframes, jet engine manufacture, and shipbuilding.Usually, pulsed beams of ultrasound are used and in the simplest instruments a single probe, hand-held, is placed on the specimen surface. An oscilloscope display with a time-base shows the time that it takes for an ultrasonic pulse to travel to a reflector (a flaw, the back surface, or another free surface) in terms of the distance across the oscilloscope screen – the so-called A-scan display. The height of the reflected pulse is related to the flaw size as seen from the transmitter probe. The relationships of flaw size, flaw distance, and flaw reflectivity are complex and considerable skill is required to interpret the display.Complex multiprobe systems are also used with mechanical probe movement and digitization of the signals, followed by computer storage; methods of computer interpretation are developing rapidly.There are several forms of mechanical vibration, depending on the direction of particle movement in the wave motion, and so there are several forms of ultrasonic waves, the most widely used in NDT being Longitudinal and transverse (shear) waves.By suitable design of probe, ultrasonic beams can be introduced into solid material at almost any angle.Longitudinal waves will also travel through liquids and a common technique is to immerse the specimen in a large tank and use a stand-off probe with a mechanized movement. With such equipment, alternative methods of displaying the signals are possible and a two-dimensional ultrasonic image can be produced (B-scan and C- scan displays). Generally, a single probe acts as both transmitter and receiver, so that inspection can be done from one side only of the specimen. Large-grain materials such as austenitic steel welding, copper castings, etc produce severe attenuation and scattering and are at present difficult to inspect with ultrasound,