GB/T 32073-2015 English PDF (GBT32073-2015)

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GB/T 32073-2015: Non-destructive testing -- Test method for measuring residual stress using ultrasonic critical refracted longitudinal wave
GB/T 32073-2015
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 19.100
J 04
Non-destructive Testing - Test Method for Measuring
Residual Stress Using Ultrasonic Critical Refracted
Longitudinal Wave
ISSUED ON: OCTOBER 9, 2015
IMPLEMENTED ON: JUNE 1, 2016
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of the People’s Republic of China;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Terms and Definitions ... 4
4 Personnel Requirements ... 5
5 Method Summary ... 5
6 Testing System ... 6
7 Testing ... 8
8 Temperature Compensation and Correction ... 10
9 Test Report ... 11
Bibliography ... 12
Non-destructive Testing - Test Method for Measuring
Residual Stress Using Ultrasonic Critical Refracted
Longitudinal Wave
1 Scope
This Standard specifies the non-destructive testing method based on ultrasonic critical refracted
longitudinal wave (creeping wave) to measure residual stress.
This Standard is applicable to the testing of residual stress and load stress in metal and non-
metal solid materials and / or components with good sound permeability.
2 Normative References
The following documents are indispensable to the application of this document. In terms of
references with a specified date, only versions with a specified date are applicable to this
document. In terms of references without a specified date, the latest version (including all the
modifications) is applicable to this document.
GB/T 228.1 Metallic Materials - Tensile Testing - Part 1: Method of Test at Room Temperature
GB/T 11345-2013 Non-destructive Testing of Welds - Ultrasonic Testing - Techniques, Testing
Levels, and Assessment
GB/T 12604.1 Non-destructive Testing - Terminology - Ultrasonic Testing
GB/T 16923 Normalizing and Annealing of Steel Parts
GB/T 18852 Non-destructive Testing - Ultrasonic Testing - Reference Blocks and Test
Procedures for the Characterization of Contact Probe Sound Beams
GB/T 25712 Vibratory Stress Relief Technology - Parameter Selection and Effect Evaluation
Methods
3 Terms and Definitions
The terms and definitions defined in GB/T 12604.1 are applicable to this document.
4 Personnel Requirements
Personnel performing testing in accordance with this Standard shall pass special training in the
non-destructive testing of residual stress using ultrasonic critical refracted longitudinal wave.
5 Method Summary
When the ultrasonic longitudinal wave excited by the transmitting transducer is obliquely
incident on the surface of the object being tested at the first critical angle, in accordance with
the Snell law, the ultrasonic critical refracted longitudinal wave can be generated inside the
material of the object being tested, and can be received by the receiving transducer, as it is
shown in Figure 1. In accordance with the principle of acoustic elasticity, the residual stress in
the material will affect the propagation speed of ultrasonic longitudinal wave. When the
direction of residual stress is consistent with the direction of the longitudinal wave, the tensile
stress will slow down the propagation of ultrasonic longitudinal wave or prolong the
propagation time t, and the compressive stress will accelerate the propagation of ultrasonic
longitudinal wave or shorten the propagation time t. Therefore, under the condition that the
distance between the excitation and receiving transducers (probe spacing) remains unchanged,
if the ultrasonic propagation time t0 corresponding to zero stress σ0 and the ultrasonic
propagation time t corresponding to the stress σ of the object being tested are measured, in
accordance with the time difference, Formula (1) or Formula (2), the absolute value of residual
stress σ in the object being tested can be obtained, namely:
Or
Where,
σ---the variation (stress difference) of the residual stress, σ = σ  σ0;
t---the variation (acoustic time difference) of the propagation time, t = t  t0;
K---the stress coefficient, which is related to the material of the object being tested and the
probe spacing, can be obtained through tensile test calibration (see 7.3).
confirm the accuracy of its detection value. Calibration intervals shall not exceed a maximum
of one year.
6.2 Probes
6.2.1 They shall be able to realize the emission and reception of ultrasonic critical refracted
longitudinal waves.
6.2.2 The probe used for testing (including at least two transducers) shall be tested in
accordance with the method specified in GB/T 18852, and its performance parameters shall be
the same.
6.2.3 The probe used for testing shall be the probe used for stress coefficient calibration and
zero stress calibration.
6.2.4 The contact surface of the probe and the surface of the object being tested shall be well
coupled. If the surface of the object being tested is curved, the coupling state shall comply with
the stipulations of 6.3.4 in GB/T 11345-2013.
6.3 Coupling Agent
Appropriate coupling agent shall be used to ensure stable and reliable ultrasonic coupling
between the probe and the surface of the object being tested within the operating temperature
range. The same coupling agent shall be used in the process of stress coefficient acquisition,
zero stress calibration and testing, and the same coupling state shall be maintained.
6.4 Zero Stress Test Block
6.4.1 Material
The material with the same metallographic structure and surface roughness as the material of
the object being tested shall be used.
6.4.2 Shape and dimensions
The shape of the test block is shown in Figure 2. The range of dimensions is shown in Table 1,
and the allowable error is  0.1 mm. The surface roughness Ra of the calibration area shall be
less than 10 m.
W of the testing area is the width or diameter of the transducer chip (which is generally 5 mm
~ 30 mm); the depth D of the testing area is determined by the frequency, see Formula (3):
Where,
D---the depth of the testing area, expressed in (mm);
f---the frequency of the probe center, expressed in (MHz);
α---the testing depth correction coefficient, expressed in (mm/ns). The reference value of
commonly used metal materials: steel 5.98, aluminum 6.40, copper 4.81.
The size of the testing area shall be greater than or equal to the range covered by the probe size,
or as agreed in the contract.
7.1.2 Probe arrangement plan
In accordance with the testing area determined through 7.1.1, design the probe arrangement
plan and clarify the testing position of the probe.
7.1.3 Surface preparation
The surface roughness Ra of the testing position shall be less than or equal to 10 m.
7.2 Adjustment and Setting of Testing Instrument
In accordance with the instruction manual, adjust the residual stress ultrasonic testing
instrument to the normal operating state.
In accordance with the determined testing area (7.1.1), set the testing parameters, such as:
testing frequency, filter bandwidth, ultrasonic excitation voltage, ultrasonic receiving gain,
probe spacing and position, etc.
7.3 Stress Coefficient Calibration
In accordance with 7.2, adjust and set the testing instrument; firmly couple the probe in the
calibration area of the zero stress test block (6.4); in accordance with the method specified in
GB/T 228.1, at room temperature (22  2) C, conduct a tensile test on the zero stress test block
(6.4)...