Materials evaluation 

About: Materials evaluation is an academic journal published by American Society for Nondestructive Testing. The journal publishes majorly in the area(s): Nondestructive testing & Ultrasonic sensor. It has an ISSN identifier of 0025-5327. Over the lifetime, 1603 publications have been published receiving 14196 citations. The journal is also known as: ME.

Practical long range guided wave testing: applications to pipes and rails

Abstract: The testing of large structures using conventional ultrasonic bulk wave techniques is slow because the test region is limited to the area immediately surrounding the transducer. Therefore, scanning is required if the whole structure is to be tested. Ultrasonic guided waves potentially provide an attractive solution to this problem because they can be excited at one location on the structure and will propagate many meters, returning echoes indicating the presence of corrosion or other discontinuities. However, guided wave testing is complicated by the presence of many possible wave modes, most of which are dispersive. These guided wave characteristics offer a wealth of opportunities for the extraction of information about the structure, but it is crucial to manage this complexity if the test is to be useable in industrial practice. Guided waves can be used in three regimes, which have been researched extensively by many authors: short range (« 1 m [39 in.], for example leaky lamb wave testing of composite materials and high frequency surface wave scanning), medium range (up to about 5 m [16.4 ft], for example shear horizontal and lamb waves in the 250 kHz to 1 MHz frequency range for plate and tube testing) and long range (up to 100 m [328 ft], for example the testing of pipelines). This paper concentrates on long range testing using frequencies below 100 kHz. The progress from research work to a robust, commercial pipe testing system is described, together with the more recent development of a test for rail. Future directions for guided wave testing are then discussed.

Long range propagation of Lamb waves in chemical plant pipework

Abstract: Site trials ofa dry coupled piezoelectric transducer system designed to detect corrosion in chemical plant pipework using cylindrical Lamb waves are described. The L(0,2) Lamb mode has been successfully propagated over distances approaching 50 m (160 ft; equivalent to 100 m [320 ft] round trip in pulse echo mode) in 152 mm (6 in.) diameter steel pipes in operating chemical plants. An excitation and reception system has also been developed which gives uni-directional propagation of the L(0,2) mode. The effect of welds, flanges and pipe supports was similar to that seen in earlier laboratory studies. The system was used successfully on painted and insulated pipes carrying both gases and low viscosity liquids.

Advanced waveform-based acoustic emission detection of matrix cracking in composites

Abstract: An advanced, waveform based acoustic emission system was used to study the initiation of transverse matrix cracking in cross-ply graphite/epoxy composites. The acoustic emission signals were detected with broad band, high fidelity sensors, and digitized for analysis. Plate wave propagation analysis was used to discriminate noise signals from those generated by cracks. The noise signals were confirmed to have originated in the specimen grip region by a new, highly accurate form of location analysis which was independent f threshold setting. Six different specimen thicknesses ([0{sub n}, 90{sub n}, 0{sub n}], n = 1 to 6) were tested under stroke controlled, quasi-static tensile loading. The presence and location of the cracks were confirmed post test by microscopy. Back scatter ultrasonics, penetrant enhanced X-ray techniques, and in limited cases, destructive sectioning and microscopy were also used to determine the length of the cracks. The average absolute value of the difference between the microscopy determined crack location and the acoustic emission crack location was 3.2 mm (0.125 in.) for a nominal sensor gage length of 152 mm (6 in.). For all cracks, the location of the crack initiation site was at one of the edges of the specimen.