Ultrasonic testing is a form of nondestructive testing. Ultrasonic testing uses special equipment to send high frequency sound waves to penetrate a material's thickness. Other special equipment is then used to receive these sound waves. Determinations about material condition and discontinuities can be made based on how the high frequency sound waves are returned to the recording equipment.Ultrasonic testing can be used to detect a variety of discontinuities. Material thickness checks can be done to determine the extent of corrosion a component has undergone. This is especially useful when only one side of the component is accessible. Ultrasonic testing can also be used to detect flaws that radiographic inspection may not be able to detect.
NDT Equipment Sales is a leading NDT supplier of non destructive testing and inspection equipment. With over 26 years in business we have built strong and lasting relationships with our clients and suppliers, leading to the introduction of new and innovative products into the NDT and Security markets.
Discontinuities such as laminations, when observed perpendicular to the plane of the lamination, are not easily detectable by X-ray; ultrasonic testing is better suited for detecting this flaw. Nearly all forms of ultrasonic testing have the same few basic components.
The transducer in an ultrasonic testing system is the origin point of the high frequency waves. It projects these waves through the material. The energy that is bounced back by geometric irregularities, such as discontinuities or edges, is picked up by the transducer. Once received by the transducer, it is interpreted by a computer that then graphs and displays these signals. A trained operator then reads these graphs and displays.Ultrasonic testing uses high frequency sound waves to penetrate materials. These sound waves typically have a wavelength of 0.5 MHz and 25 MHz.
When shorter wavelengths are used, smaller discontinuities and defects can be detected. Longer wavelengths lead to lower detection sensitivity. The proper wavelength depends on the material type, material crystalline structure and probable defect shapes and sizes.
Ultrasonic Pulse Velocity (UPV) is an effective non-destructive testing (NDT) method for quality control of concrete materials, and detecting damages in structural components. The UPV methods have traditionally been used for the quality control of materials, mostly homogeneous materials such as metals and welded connections. With the recent advancement in transducer technology, the test has been widely accepted in testing concrete materials. Ultrasonic testing of concrete is an effective way for quality assessment and uniformity, and crack depth estimation.
The test procedure has been standardized as “Standard Test Method for Pulse Velocity through Concrete”. Ultrasonic Testing of Concrete - How it works?The concept behind the technology is measuring the travel time of acoustic waves in a medium, and correlating them to the elastic properties and density of the material. Travel time of ultrasonic waves reflects internal condition of test area. In general, for a given trajectory, higher travel time is correlated to low quality concrete with more anomalies and deficiencies, while lower travel time is correlated to high quality concrete with fewer anomalies. Once ultrasonic wave spreads within the test area, the wave is reflected in boundary of anomalies resulting in higher travel time. This results in higher transmission time (lower wave speeds) in poor quality concrete and lower transmission time (higher wave speed) in good quality concrete.Different configurations of transducers can be used to perform a UPV test. This includes direct transmission, semi-direct transmission, and indirect (surface) transmission.
Figure above shows different configurations of transducer based on the access to the surface of test area. The ultrasonic velocity is prone to signal travel trajectory that is defined by the transducer configurations. Figure below is a representation of the effect of concrete anomalies and deficiencies on the acoustic wave travel time and the corresponding velocity throughout a given trajectory (ACI 228.2R, 2013). Couplant Concrete-Transducer contactThe UPV transducers must be in full contact with the concrete surface; otherwise the air pocket between the transducer and concrete may result in measurement error (i.e. Inacurate measurement of transit time). One reason is that only negligible amount of wave energy will be transmitted in a poor contact.
Different couplants can be used to eliminate air pockets and to assure good contact (e.g. Petroleum jelly, grease, liquid soap, and kaolin-glycerol paste). It is recommended to make the couplant layer as thin as possible. Applications of UPV Testing for ConcreteSeveral researchers and engineers have studied the use of ultrasonic testing of concrete in different engineering projects:1- Pulse Velocity Determination2- Concrete Quality Assessment 3- Establishing Homogenity and Uniformity of Concrete4- Measurement of Surface Crack Depth 5- Prediction of Compressive Strength of Concrete UPV - Influencing ParametersIn order to conduct a reliable ultrasonic testing of concrete, the surface of concrete should be clean, and free of dust. A suitable couplant is needed to establish an ideal connection between concrete and UPV transducers.
Special attention should be given to rebar in concrete, since the wave travel speed in metal is much higher than in concrete. The interpretation of test results in heavily reinforced concrete is somewhat difficult.
The direct configuration is the most ideal for getting reliable readings; however, the use of this configuration is mainly limited to laboratory. In summary, the following issues should be addressed before, during, and after performing the test:1- Concrete Properties (aggregate size, type, and content)2- Transducer Contact/couplant material3- Presence of Rebar4- Sensor Configuration. Hi guys,I am an ultrasonic level II technician for steel and have 40 years + experience in the trade. I was, however, contacted by a company here to try and sort out their CONCRETE UT MACHINE!! I am honest if I say that I do not know anything about concrete testing but would really like to help them out as they do not have a clue how to operate the machine and the job was dumped on them.
My company do the NDT on the pipe work and they must do the concrete testing. Is it possible somebody that is willing to guide me through the calibration process of the machine with some hintsThanks a million in advanceJohan Gous.