Through transmission testing

In this paper we propose a multivariable regression approach for estimating ultrasound attenuation in composite materials by means of pulse-echo measurements, thus overcoming the problems with limited access that is the main drawback of through-transmission testing. 

One obvious disadvantage with both the approaches mentioned above is that the attenuation measurements are based on through-transmission, TT, testing which means that we need access to both sides of the specimen and this cannot be guaranteed for many of the complex geometries found, e.g., in the aircraft industry. 

The common civil engineering seismic testing techniques work on the principles of ultrasonic through transmission (UPV), transient stress wave propagation and reflection (Impact Echo), Ultrasonic Pulse Echo (UPE) and Spectral Analysis of Surface Waves (SASW). 

Permeability of an FML is evaluated using the Water Vapor Transmission test.28 A sample of the membrane is placed on top of a small aluminum cup containing a small amount of water. The cup is then placed in a controlled humidity and temperature chamber. The humidity in the chamber is typically 20% relative humidity, while the humidity in the cup is 100%. Thus, a concentration gradient is set up across the membrane. Moisture diffuses through the membrane, and with time the liquid level in the cup is reduced. The rate at which moisture is moving through the membrane is measured. From that rate, the permeability of the membrane is calculated with the simple diffusion equation (Fick s first law). It is important to remember that even if a liner is installed correctly with no holes, penetrations, punctures, or defects, liquid will still diffuse through the membrane. 

As indicated by Fig. 2, there are several testing modes (1) pulse-echo mode, (2) through-transmission mode, (3) reflector-plate mode, and (4) angle-beam mode. 

A major hydraulic fracturing experiment was performed in September and October 1993 at Soultz-sous-Forets. In the September test, 25,000 m of fresh water were injected between 2850-3350 m at progressively higher rates to 40 1/s and pressures of up to 10 MPa over a 17 day period. In October, a further 20,000 m of water were injected at up to 50 l/s into the entire open hole section. Through the test, it was demonstrated that the fracture network in the basement rock was well developed, with enhanced permeability and a substantial increase in transmissivity (Baria et al., 1999 Evans, 2000). 

FIGURE 15.6 Scheme for the glucose transmission test of immature IJE in Caco-2 cells. Caco-2 cells were precultured for 2 weeks to cover the membrane filter as an experimental model for intestinal epithelia in vitro. Completion of the cell monolayer was detected by TEER measurement (Millicell-ERS). The transport of glucose from the upper cavity (apical site) to the lower cavity (basal site) through glucose transporters was evaluated by measuring both glucose concentrations for constant periods. 

Thermal waves have relatively shallow penetration into a material surface flaws tend to cause heat to diffuse at a different rate from that of the surrounding material [68]. In thermographic testing, two techniques exist, the single-sided technique and the through-transmission or double-sided test. In the former, which is more sensitive to flaw depth indication, only the test area scanned is heated (Eig. 4), while the double-sided technique uses the transmission characteristics of a heat pulse passing through a thin section of composite material [64], Temperature patterns at the surface of a composite arc produced... 

The two major techniques in ultrasonic testing arc the pulse-echo mode and the through-transmission mode. In pulse-echo mode, the same transducer is used to emit and receive ultrasonic waves and requires access to only one side of the structure inspected (Fig. 12). The pulse-echo technique is effective on the near side skin laminate only, and the sensitivity decreases as a function of depth [29]. With the through-transmission mode, access to both sides of a structure is required as an emitter probe is placed on one side and a receiver on the other (Fig. 13). This technique measures the signal amplitude of ultrasonic waves transmitted through the material tested and is more sensitive to small defects than the pulse-echo mode. The detection of flaws throughout the whole depth of a... 

Rose, J.L. and J.J. Ditri, Pulse-echo and through transmission Lamb wave techniques for adhesive bond inspection. British Journal of NOT, 34(12), 1992. GogUo, L. and M. Rossetto, Ultrasonic testing of adhesive bonds of thin metal sheets. NDT E International, 32 323-331,1999. 

Sound transmission loss refers to the response of specimens exposed to a diffuse incident sound field. The test results are therefore most directly relevant to the performance of similar specimens exposed to similar sound fields. They provide, however, a useful general measure of performance for the variety of sound fields to which a partition or element may typically be exposed. In laboratories designed to satisfy the requirements of this test method, the intent is that only significant path for sound transmission between the rooms is through the test specimen. Laboratories are designed so the test specimen constitutes the primary sound transmission path between the two test rooms and so approximately diffuse sound fields exist in the rooms. 

Acoustic transmission measurements were made on a Norton-supplied tensile bar in the molded state. Because this material had not been tested acoustically, there was uncertainty as to the value of its properties, particularly attenuation. PAD found that at 5 MHz, attenuation was sufficiently low that a through transmission signal was easily obtained through the length of the sample. This may allow conducting velocity measurements across the samples at frequencies as high as 20 to 50 MHz, yielding measurement accuracy considerably better than 1%. The velocity and impedance obtained for this sample were 2.3 mm/sec and 5.3 MR, respectively. 

The study was set up to go through four test phases, each looking at critical metrics such as start-up time, time to full load and overall reliability. The four phases after installation, initial testing of safety systems, calibration and testing of the remote transmission of data were ... 

Sound is introduced into one of the rooms, referred to as the source room, and part of the sound energy is transmitted through the test partition into the second room, referred to as the receiver room. The resulting mean space average sound pressure levels in the source and receiver rooms are measured and the difference in levels, called the noise reduction, NR, is determined. The random incidence transmission loss can be obtained by ... 

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