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61 Distance amplitude curve of a 2 mm - disk reflectorįig.
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This does not normally apply to the near-field of the sound beam! Here, the test results show that the echo heights within the focus reach their highest amplitude and are reduced again at shorter distances, Fig. With accurate tests using flat-bottom holes at different depths a simple law can be found, at least in the far field of the applied sound beam: However, if the echoes from two drill holes at different depths are compared then an additional distance dependence of the echo heights is established, Fig. The echo heights are proportional to their area or The echo heights are proportional to the square of their diameter.Įxample: The flat-bottom hole with a diameter of 2 mm has an echo which is 4 times that of a 1 mm flat-bottom hole because the area has quadrupled. drill holes with flat bottoms and at equal depths, this law can be confirmed: 60 Reflectors at different depths and their echoes 59 Reflectors with different areas and their echoesįig. This feasible behavior can be used on small reflectors: their echo heights increase with their areas, Fig. We have noticed previously that the height of a reflector echo will become greater the larger the sound beam area is which covers the reflector. If such a reflector is evaluated by scanning then it is not the size of the reflector which is obtained as a result but the diameter of the sound beam! Therefore, the scanning method is not practical in this case. TR probes are especially suited which have a hose-shaped sound beam with a small diameter (1 - 3 mm) at their most sensitive depth range.Ī reflector which is completely contained within the sound beam is regarded as a small reflector. Therefore, if the reflector extension is to be exactly measured it is recommended that a probe be selected which has its focal point at the same distance as the reflector. Location of the reflector boundry becomes more exact the smaller the diameter of the sound beam is at the reflector position. The probe position is marked and the operator determines further boundry points until a contour of the discontinuity is formed by joining the marked points together, Fig. This means that the acoustic axis is exactly on the boundary of the discontinuity. 58b Top view with reflector for extension. 58a Straight beam probe on the reflector boundryįig. 57 A large reflector in the sound beamįig. The probe position on the test object at which the echo drops by exactly half indicates that the discontinuity is only being hit by half the sound beam, Fig. The ultrasonic operator normally observes the height of the discontinuity echo. By scanning the boundaries of the discontinuity, reliable information can be obtained about its extension. The discontinuity then reflects the complete impacting energy back, Fig. In ultrasonic evaluation one is frequently able to come near to the true reflector size as long as the discontinuity is large compared to the diameter of the sound field.
#Recording audio in reflector 3 manual
In fact, the echo height plays the decisive part when evaluating discontinuities during manual Ultrasonic Testing. However, due to the fact that on the display only the echo can be interpreted, this means the reflected sound coming from the discontinuity, it is very often difficult, and in some cases even impossible, to reliably assert the size of the reflector. The operator's wish to accurately know the "real reflector size" is understandable therefore it is expected that an nondestructive testing method, such as ultrasonic testing, give this information. Of course, a discontinuity is best evaluated when its size (extension) is known. Method of testing and instrument technologyĦ.2 Evaluation of small discontinuities: The DGS method Why use ultrasonics for nondestructive material testing?Ĥ. Introduction to the Basic Principles - TABLE OF CONTENTS Introductionġ. Nondestructive Material Testing with Ultrasonics Introduction to the Basic Principles NDT.net - September 2000, Vol. Nondestructive Material Testing with Ultrasonics.