The standard sample СО-2 is a sample of a special form with control holes made in it and used in ultrasonic inspection. The linear dimensions of the sample, as well as the size and location of the control holes are regulated by GOST 14782-86. This sample allows you to determine such important characteristics of the piezoelectric transducer as the angle of entry of the ultrasonic beam, the conditional and ultimate sensitivity, the width of the main lobe of the radiation pattern , the pulse conversion coefficient (when controlling welded joints from low-carbon and low - alloy steels, and also check the correspondence of its dead zone value. Standard СО-2 is a part of the Set of control samples KOU-2 .
Content
- 1 Manufacturing requirements
- 2 Methods of measuring characteristics
- 3 Metrological status of samples for ultrasonic testing
- 4 Regulatory and technical documentation
- 5 notes
Manufacturing Requirements
The sample must be made of fine-grained steel grade 20 according to GOST 1050-74 (not valid since 1081, instead of it - GOST 1050-2013), or grade 3 steel according to GOST 14637-79. In this case, the longitudinal wave propagation velocity at a temperature of (20 ± 5) ° C should be equal to (5900 ± 59) m / s. The measured value of the speed with an accuracy of ± 0.5% should be indicated in the passport for the sample. In the case when the acoustic properties of the material of the controlled object, for example aluminum, differ from the acoustic properties of mild and low alloy steel, it is necessary to produce a sample of СО-2А from an identical material in full accordance with the drawing for a sample of СО-2.
On one side of the sample is a calibration scale for the input angle. The scale is applied in accordance with the formula
Where - the distance from zero of the scale to the mark corresponding to the determined value, - the depth of the hole ⌀6 mm relative to the plane for which the calibration scale is determined, - the value of the input angle for which the position of the mark on the scale of the sample is determined.
The zero of the scale (and, accordingly, the input angle of 0 °) should coincide with the center of the hole ⌀6 mm on the sample with an accuracy of ± 0.1 mm. Due to the increased requirements for the accuracy of applying the scale, it is applied only on one side of the sample, because otherwise the scales may not coincide with each other and, accordingly, the parameters measured on these scales may also differ. Through holes ⌀6mm and ⌀2mm must be made after applying the scale to the sample.
Performance Measurement Methods
Metrological status of samples for ultrasonic testing
Until recently, the metrological status of samples from the KOU-2 set was not clearly defined [1] . The expired GOST 14782-86 , valid on the territory of the Russian Federation until July 1, 2015, gave an ambiguous definition, which required repeated interpretation by authorized metrological institutes.
GOST 55724-2013 "Non-destructive testing. Welded joints. Ultrasonic methods ”, introduced on the territory of the Russian Federation from 07/01/2015 (instead of GOST 14782-86), officially assigned the status of measures (calibration samples) with standard equipment samples with metrological support in accordance with applicable law. The definitions given in the new GOST 55724-2013 with reference to the international standards GOST R ISO 5577-2009 (ISO 5577: 2009) and GOST R 53697-2009 (ISO / TS 18173: 2005) are contained in clauses 3.1.9 and 3.1. eleven
From the samples not covered by the new GOST R 55724-2013, but for all the signs that fall under his definition of “measure”, in addition to СО-2 and СО-3, a sample can be distinguished for tuning flaw detectors on a phased array, in accordance with the recently adopted ISO / DIS 19675: 2017.
Regulatory and technical documentation
GOST 14782-86 Non-destructive testing. Welded joints. Ultrasound methods.