Ultrasound is sound waves of identical nature to sound waves, differing such that its frequency range is located in the audible. This method is a major non-testing methods destructive, for quality control and evaluation of materials in the industry today. Its application allows to know the integrity of material thickness and detect discontinuities internal not visible on the surface of the welding. In addition to determining differences in the structure of the material and physical properties.
Materials and equipment to be used.
• Ultrasonic equipment generator signals of 2.25 MHz with an element of Lucita 6 mm * 6 mm (1 / 4 "* 1 / 4"). It recommends the following equipment:
Krautkramer 6 MHZ, USL-32 model.
Krautkramer 2.2 MHZ, USN-52 model.
• Probes of incidence angle 60th issue specifically.
• Coupling: oil.
• Cleaning cloths.
Surface Preparation.
It recommends a manual cleaning entire area of the weld and its surroundings, In order to remove all traces of dirt present in the sample. The surface must be free of dirt and completely dry. It calibrate the equipment to a nominal frequency of 4 MHZ.
Procedure.
• After cleaning the surface shall be the application of coupling, in this case oil.
• If the ultrasonic beam is sufficiently divergent, they cover the height or thickness
union without moving the probe moving back and forth between the distances d and d / 2 as shown in Figure 2.1
•If the sample is thick and narrow beam, a Once the probe oriented at an angle Straight with the solder joint, we must move according to Figure 2.2.
• Following a reciprocating action, among mentioned distances d and d / 2, so
explore the entire section of the union, and a little more to take into account the width of cord.
• For higher security recommended to repeat the test from the other side of the junction (direction 2), because some heterogeneities are best detected in a in the other direction.
• Should combine reciprocating between d and d / 2, with a slight rotation probe to one side to another address perpendicular to the union in order to detect most favorable angles heterogeneities slopes.
•To detect transverse cracks, apply two probes as (a) and (2) Figure 2.2 (C), connected in parallel
Morphology of the heterogeneity.
Interpretation of the signs.
The presentation of results is the type A-Scan in which the height of the echoes of indication or "peaks" represent the beam intensity reflected ultrasound. The horizontal base line indicates the time or distance of travel, vertically while the amplitude is observed signal. The shape of the indication of the echo can
provide some information about morphology heterogeneity.
If the indication of the echo reaches a total height with few steps (high frequency nodes) usually it comes from a flat reflector irradiated in address next perpendicular to the plane, Figure 2.3 (a). On the contrary if the heterogeneity is not flat or is irregular or is flat or rough does not radiate perpendicular, rising indication Echo is usually more gradual, resulting therefore wider, Figure 2.3 (b).
Here are some figures in the which give some general criteria angular probe testing, which can help classify the heterogeneity within one of three simple forms.
• Flat (Fig. 2.4)
•Cylindrical (Fig. 2.5)
• Spherical (Fig. 2.6)
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