GB/T 18852-2020 in English
VALIDNon-destructive testing—Ultrasonic testing—Reference blocks and test procedures for the characterization of contact probe sound beams
- Issued on:2020-11-19
- Implemented on:2021-06-01
- File Format:PDF
- Delivery:Via email within 5 business days
$359.00
《GB/T 18852-2020无损检测 超声检测 测量接触探头声束特性的参考试块和方法》由TC56（全国无损检测标准化技术委员会）归口，主管部门为国家标准化管理委员会。
Introduction
Interpretation of the core content of the standard
GB/T 18852-2020 is equivalent to the ISO 12715:2014 international standard, which specifies the measurement method of the acoustic field characteristics of the contact ultrasonic probe in the workpiece. The standard is applicable to straight probes, oblique probes (0°-70°), focused probes and dual crystal probes with a chip size of ≤25mm and a frequency of 1-15MHz.
Key Technical Points
| Measurement Dimensions | Reference Test Block | Key Parameters | Applicable Probe Types |
|---|---|---|---|
| Longitudinal Beam Characteristics | SDH Test Block | Axis of Sound, -6dB Beam Width | All Types |
| Cross-Sectional Beam Characteristics | HS Test Block | Skew Angle, Focus Parameters | Angle Probe/Focused Probe |
| Time Base Characteristics | HS Test Block | Sound Path Calibration, Delay Time | Angle Probe |
Reference Test Block Specifications
Semi-Circular Step Test Block (HS)
A sectioned cylinder with a step radius of 20-100mm is used, and the surface of each step needs to be finely machined to Ra≤3.2μm. A 2mm groove is set on the 91mm step for time base calibration, and the measurement error should be controlled within ±0.1mm.
Side Hole Test Block (SDH)
Contains 8 φ1.5mm side holes, with the hole center 2-60mm from the detection surface. The SDH456 hole is positioned in three-dimensional coordinates (B surface 40mm/R surface 50mm/T surface 60mm) to verify the three-dimensional sound beam characteristics of the probe.
Typical measurement process
- Instrument calibration:Use the HS test block to adjust the time baseline so that the 20mm and 40mm step echoes are aligned with the screen scale
- Amplitude measurement:Scan each horizontal hole on the SDH test block and record the -6dB point position
- Focus calculation:For the focused probe, the focal length (FD), focal length (FL) and focal width (FW) need to be measured
- Deflection angle verification:Determine the deviation angle of the sound beam center through the HS test block groove echo
Technology evolution analysis
Compared with the 2002 version of the standard, the main improvements of the 2020 version include: ①Adding dual crystal probe measurement method; ②Introducing the concept of time-of-flight (TOF) characteristic curve; ③Refining the definition of focused probe parameters; ④Clarifying the coordinate marking system of the cross-hole test block. These revisions make the standard more in line with the technical requirements of modern phased array ultrasonic testing.
Implementation suggestions
- For new material testing, the refraction angle needs to be corrected by Snell's law
- It is recommended to verify the probe time base linearity with HS test blocks every 3 months
- The thickness of the coupling agent should be kept consistent when measuring with a focused probe (recommended 0.05-0.1mm)
- The influence of the temperature coefficient of the velocity of sound needs to be considered for testing in high temperature environments
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