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NON DESTRUCTIVE TEST METHODS
State-of-the-Art Techniques List of Selected Projects |
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 Impact-Echo In this technique, mechanical energy in the form of a short pulse is introduced into a member under investigation. Reflected stress waves are monitored by a sensor and are transformed into a frequency domain using a Fast Fourier Transform method. The resulting amplitude spectrum is used to determine condition of the member. click here for more... |
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 Radar This system consists of an antenna housing and a control unit. The antenna housing contains both the transmitting and receiving antennas. The high frequency radio waves are reflected from the subsurface features and are stored by the digital control unit. As the antenna is moved along the surface, echos are plotted to form a pattern which is used for interpretation. click here for more... |
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 Pulse-Echo Pulse-echo method is useful in determining the depth of piles , drilled shafts or caissons. The method can also be used to determine concrete quality if the depth of the pile is known. The method is performed by impacting the top surface of the pile near a sensor. The impact creates a compression wave which is reflected at the bottom of the pile and it is received by the sensor. By using the waveform analyzer, arrival time of the reflected wave is calculated to determine the depth of the pile. |
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 Impulse Resopnse Impulse Resonse (IR) is a nondestructive testing technique in which "mobility" of the structure under investigation is determined. Mobility is a complex ratio of particle velocity and the applied force. The test involves striking the surface of the structure with an instrumented hammer and measuring vibrations of the structure. click here for more... |
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 Pulse Velocity A pair of piezoelectric sensors are placed at opposite ends of the test member. In one of the sensors, electronic pulses are generated and the time it takes for the pulse to propagate through the concrete is measured by the other sensor. Knowing the distance traveled, propagation velocity is calculated and based on the velocity, condition of the concrete is determined. Depending on the locations of the sensors, the procedure is divided in to three categories: direct (sensors at opposite ends), indirect (sensors on the same sides), and semi-direct (sensors at right angles) transmission. The method is useful in determining presence of cracks or voids and overall quality of the concrete. click here for more... |
