Entri blur ...

Semenjak dua menjak dapat job ni aku dah jadi burung hantu. Tidur sejam dua siang masa tidurkan Ali, pastu berjaga sepanjang malam sampai tiba masa nak sediakan sahur. Sangat memenatkan dan memblurkan! Bukan setakat menterjemah tapi perlu retype the whole document sebab pemiliknya tiada salinan yang tersimpan dalam komputer. Semua lecture note dia dalam bentuk buku atau salinan fotostat yang dikhuatiri akan 'hilang' jika tidak preserve dalam komputer. So, it's a 2 in 1 job.

Mari belajar pasal Ultrasonic.

..... In Fig. 2.2 (a), the white areas show the areas of high sound intensity and the dark areas the low or zero intensity areas. The highest sound intensity is shown as a very white area on the beam axis some distance from the transducer. This is the ‘Main Beam’ of the sound field generated by the transducer and is in the form of a cone with an origin at the center of the transducer face and spreading out from the transducer depending in the distance of travel. The angle between the beam axis and the edge of the cone is called the ‘Angle of Beam Spread’ and is given by the following equation.

Øo = Sin -¹ 1.22 λ ~ 70
D

where Øo = angle of beam spread in degrees
λ = wave length
D = active tranducer diameter
C= sound velocity in the test object
F = sound wave frequency (Hz = 1/sec)

From Equation (2.1) it can be seen that the larger the diameter of the transducer and the higher the frequency the smaller the angle of beam spread.

(1) Near Zone and Far Zone
In Fig. 2.2 (a) it can be seen that sound intensity is not always highest on the beam axis. Strong and weak intensity areas alternate both transversely and longitudinally throughout what is called the Near Zone or Fresnel Zone of the beam. Beyond the Near Zone the sound intensity gradually weakens with beam path distance due to beam spread. In this area termed the Far Zone sound propagates as a cone shaped beam as if it emits from the center of the transducer. The sound intensity on the beam axis reaches a maximum at several points in the Near Zone, as shown in Fig. 2.2 (b) and the last peak is the boundary between the Near Zone and the Far Zone. The length of the Near Zone, Xo, is a function of the transducer diameter, D, and the wavelength, λ,

Xo = D (2.2)

It follows from the equation that the larger the transducer diameter and the higher the frequency, the larger the Near Zone, Xo can be used as a parameter to express beam path distance as a function of transducer diameter and frequency (This will be discussed later in Section 3.1.5 – DGS Diagram).
Fig. 2.3 shows three theoretical sound beams calculated from Equations (2.1) and (2.2) for the following three transducers.
5Q20N : 5MHz, Quartz, 20mm diameter normal beam
2Q20N : 2MHz, Quartz, 20mm diameter normal beam

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Kepala otak aku penuh dengan segalanya ultrasonic, beam, transducer, axis, quartz, flaws .. bla bla bla bla bla blurrrrrrr .....

.... nak sambung berultrasonic .... blurrrrrr ....