Standard No.:	GB/T 18852-2002
Chinese Name:	无损检测 超声检验 测量接触探头声束特性的参考试块和方法
English Name:	Ultrasonic non-destructive testing--Reference blocks and test procedures for the characterization of contact search unit beam profiles
Professional Classification:	J04 Basic standards and general methods
Professional Classification:	GB National Standard
ICS Classification:	19.100
Issued by:
Issued on:	2002-10-11
Implemented on:	2003-05-01
Status:	VALID
Language:	English
File Format:	PDF
Word Count:
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This Standard introduces two metal reference blocks, the hemi-step (HS) and the side-drilled-hole (SDH) blocks. This Standard establishes procedures for measuring the sound field or beam profiles produced by search units in contact tests. The search units include straight beam, angle beam (refracted compressional and refracted shear), focused beam and dual element search units. The diameter or the side dimension of the search unit shall be no greater than 25 mm. The methodology of this Standard provides guidelines for search units to be used for different metals including forged or rolled steel, aluminum or titanium alloy products. The frequency range of the search units used in this Standard extends from 1 MHz to 15 MHz, where 1 MHz to 5 MHz is best suited for steels and 5 MHz to 15 MHz is best for fine grain structured alloys such as aluminum products. If this Standard is to be used for material other than steels, users should be aware of the fact that the wave velocities in these materials may be different from that of steels and the angle beam search units are normally designed based on the steel applications. Snell’s law of refraction is described in this Standard so that correct refraction angles in other materials can be calculated. This Standard applies to angle beam search units of all practical angles (0° to 70°), and to focused and dual element search units. This Standard does not address the use of surface (Rayleigh) wave search units.
The procedures in this Standard can be used in whole, or in part, with other standards. For testing materials which are very thick or very thin, the present reference blocks may be made proportionally larger or smaller to accommodate different search unit beam sizes. This Standard does not address the estimation of equivalent defect sizes which will require reference blocks with flat-bottom-holes. This Standard establishes no acceptance criteria; but does establish the technical basis for criteria that may be defined by user parties.