AS ISO 16809 pdf download

AS ISO 16809 pdf download.Non-destructive testing — Ultrasonic thickness measurement
1  Scope
This document specifies the principles for ultrasonic thickness measurement of metallic and non- metallic materials by direct contact, based on measurement of time of flight of ultrasonic pulses only.
2  Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 5577, Non-destructive testing — Ultrasonic testing — Vocabulary
3  Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5577 apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https:// www .iso .org/ obp — IEC Electropedia: available at http:// www .electropedia .org/
4  Measurement modes
The thickness of a part or structure is determined by accurately measuring the time required for a short ultrasonic pulse generated by a transducer to travel through the thickness of the material once, twice or several times. The material thickness is calculated by multiplying the known sound velocity of the material with the transit time and dividing by the number of times the pulse transits the material wall. This principle can be accomplished by applying one of the following modes, see Figure 1. 1) Mode 1: Measure the transit time from an initial excitation pulse to a first returning echo, minus a zero correction to account for the thickness of the probe’s wear plate and the couplant layer (single-echo mode). 2) Mode 2: Measure the transit time from the end of a delay line to the first back wall echo (single- echo delay line mode). 3) Mode 3: Measure the transit time between back wall echoes (multiple-echo mode).
5  General requirements
5.1  Instruments The following types of instruments shall be used to achieve thickness measurement: a) dedicated ultrasonic thickness measurement instruments with numerical display showing the measured value; b) dedicated ultrasonic thickness measurement instruments with numerical display showing the measured value and A-scan presentation (waveform display); c) instruments designed primarily for the detection of discontinuities with A-scan presentation of signals. This type of instrument can also include numerical display of thickness values. See 6.4. 5.2  Probes The following types of probes shall be used; these are generally longitudinal wave probes: — dual-element probes; — single-element probes. See 6.3. 5.3  Couplant Acoustic contact between probe (probes) and material shall be provided, normally by application of a fluid or gel. The couplant shall not have any adverse effect on the test object, the equipment or represent a health hazard to the operator. For the use of the couplant in special measuring conditions, see 6.6. The coupling medium should be chosen to suit the surface conditions and the irregularities of the surface to ensure adequate coupling. 5.4  Reference blocks The measuring system shall be calibrated on one or more samples or reference blocks representative of the object to be measured, i.e. having comparable dimensions, material and structure. The thickness of the blocks or the steps should cover the range of thickness to be measured. Either the thickness or the sound velocity of the reference blocks shall be known. 5.5  Test objects The object to be measured shall allow for ultrasonic wave propagation. There shall be free access to each individual area to be measured. The surface of the area to be measured shall be free of all dirt, grease, lint, scale, welding flux and spatter, oil or other extraneous matter that could interfere with the testing. If the surface is coated, the coating shall have good adhesion to the material.