Reflected echoes

Up to now the Reference Block Method and the DGS-Method are world wide the most important techniques for evaluating defect signals in manual Ultrasonic Testing. Even today, individual national standards refer to either one of these two echo evaluation techniques. However, both reflected echo signals from natural defects are compared with an echo from a known reference reflector at the same distance. The result of the evaluation is either... 

Second, the target should rather be a large surface, homothetic to the probe shape, producing the strongest back-reflected echo with no front wave distortion and with the same time of flight for all the elements. 

Once the probe is set into the target, the acquisitions consist of the peak to peak amplitude, the time of flight and the frequency response of the back-reflected echo. 

Fig.3 shows the defect position on the bonding interface and the model of the reflective echo. The defects are exists on each bonding surface as(ii) (iv), is no exist as (i). 

The reflective echo on the bonding interface of similar materials is caused only by the defect. On the other hand, the... 

This study was in real time measured that the reflective echo height of the bonding interface in the solid phase diffused bonding process of carbon steel and titanium using ultrasonic testing method. As a result, the following were made discernment. 

Fig.4 shows the relation of the reflectional echo height F/B of the ultrasonic wave and... 

F — B ) is the ratio of the reflective echo height F from the contact surface to the standard reflective echo height B on the bottom of the upper specimen. Hereafter, F/B is called the echo height. Moreover, the contact surface of this lower specimen have no V defect. In the frequency, O is... 

Fig.4 Relation of reflective echo height F/B and axial compressive stress a (pseudo-bonding)...

Fig.7 shows the relation of the F/B, the temperature T and the time t as the retio of contact surface area Sa /So=50%. O mark is the B echo on the bottom of the upper specimen A mark is the F echo on the bonding interface. The B echo has changed in the changing temperature T. Therefore, the really reflective echo height F/B on... 

At first a calibration measurement is necessary. The container is filled with water and the amplitude of the reflected echo of the steel plate is measured. This value is measured at the end... 

However, with ultrasonic technique the signal level of the reflected echo pattern is also influenced by the geometrical shape, and misalignment between measuring direction and radial direction. Therefore, the practical demand for guidance must be found by experiments. 

Pulse inversion sonography (also called second harmonic) is a technique that works by sending two separate pulses, 180° out of phase, and summing the reflected echoes to form the final sonographic signal. 

The technique involves evaluating reflection (echo) and transmission characteristics of an ultrasound radiation, when crossing layers of different density, which present different acoustic impedance. Illumination intensity of different zones using echography is proportional to the density of the crossed structures, thus, the technique detects the presence... 

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