ASTM E3045-22

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Designation: E3045 − 21 E3045 − 22
Standard Practice for
Crack Detection Using Vibroacoustic Thermography
This standard is issued under the fixed designation E3045; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 Purpose—This practice covers procedures required to conduct an examination of components using vibroacoustic
thermography.
1.2 Application—The vibroacoustic thermography process has been used for component inspections in the aircraft, power
generation, automotive, and other industries for testing new and serviced components, both coated and uncoated. Current
applications are mostly targeting metallic components, but composite and ceramic component applications are under development
(1).
1.3 Background—Vibroacoustic thermography is a new technique within the area of active thermography. an active thermography
technique that falls under the category of Infrared Thermography Testing (IRT). The technique was first published by Henneke,
et al. in 1979 (2) and has been expanded on and popularized by Favro, et al. (3). During the test, a defect thermal response resulting
from a short burst of ultrasonic energy typically in the range of 15 kHz to 40 kHz is detected by an infrared camera. The ultrasound
coupled into the component being tested can activate a thermal response in defects with contact areas that can move against each
other, that is, cracks and delamination. There are different energizing and coupling techniques that are commonly used depending
on the needs and capabilities. These variations and the down selection process are not included in the procedure and should be
developed/optimized by experimentation for each new component application.
NOTE 1—Vibroacoustic thermography is typically sensitive to tight planar defects (4). Volumetric defects such as porosity, inclusions, open ruptures, or
cracks in wide-open areas, will not typically result in an indication. Therefore, an augmenting method should be conducted to detect volumetric defects.
(See Terminology E1316.)
NOTE 2—Vibroacoustic thermography is a surface examination but has demonstrated detection sensitivity for subsurface defects including back wall
defects for thin components (5), (6). Care should be taken when developing vibroacoustic thermography for the detection of subsurface defects.
1.4 Warnings:
1.4.1 Warning—Vibroacoustic thermography requires the energization of the test article with vibrational energy. During
energization, the complete component may be excited with vibroacoustic (vibration) energy for as long as several seconds. The
development of this test for a new application requires special measurements, precautions, and attention to component response.
The component design engineer and the NDE engineering specialist knowledgeable of this technique should be satisfied that the
test will not cause damage or reduction of service life.
1.4.2 Warning—Vibroacoustic thermography, like any other NDT technology, requires thorough development and testing for
This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.10 on Specialized NDT
Methods.
Current edition approved Dec. 1, 2021July 1, 2022. Published January 2022July 2022. Originally approved in 2016. Last previous edition approved in 20162021 as
E3045 – 16.E3045 – 21. DOI: 10.1520/E3045-21.10.1520/E3045-22.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3045 − 22
each application, including clear definition of the inspection objective, as well as development of objective means to distinguish
between rejectable indications and conditions that should not be cause for rejection. Incomplete development and application will
result in high incidence of improper rejections and high incidence of defect "misses." The images produced by many vibroacoustic
thermography inspections can otherwise lead to inspector fatigue and ineffective evaluations.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E168 Practices for General Techniques of Infrared Quantitative Analysis
E1213 Practice for Minimum Resolvable Temperature Difference for Thermal Imaging Systems
E1252 Practice for General Techniques for Obtaining Infrared Spectra for Qualitative Analysis
E1311 Practice for Minimum Detectable Temperature Difference for Thermal Imaging Systems
E1316 Terminology for Nondestructive Examinations
E1933 Practice for Measuring and Compensating for Emissivity Using Infrared Imaging Radiometers
E2585 Practice for Thermal Diffusivity by the Flash Method
2.2 ASNT Standards:
SNT-TC-1A Recommended Practice, Personnel Qualification and Certification in Nondestructive Testing
ANSI/ASNT CP-189-2001 Standard for Qualification and Certification of Nondestructive Testing Personnel
2.3 ATA Standard:
ATA-105 Guidelines for Training and Qualifying Personnel in Nondestructive Testing
2.4 U.S. Publication:
MIL-HDBK-1823A Department of Defense Handbook: Nondestructive Evaluation System Reliability Assessment
3. Terminology
3.1 Abbreviations:
3.1.1 ANSI—American National Standards Institute
3.1.2 ASNT—American Society for Nondestructive Testing
3.1.3 ATA—Air Transport Association
3.1.4 CCD—Charge Couple Device
3.1.5 FOV—Field of View
3.1.6 IR—Infrared
3.1.7 IRT—Infrared Thermography Testing
3.1.8 LWIR—Long-Wave Infrared
3.1.9 MWIR—Mid-Wave Infrared
3.1.10 NDE—Non-destructive Examination
Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Available from Air Transport Association (ATA), 1301 Pennsylvania Avenue, Suite 1100, Washington, DC 20004–1707.
Available from IHS Markit, https://global.ihs.com/.
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3.1.11 NETD—Noise Equivalent Temperature Difference
3.1.12 POD—Probability of Detection
3.1.13 ROI—Region of Interest
3.1.14 SDS—Safety Data Sheets
3.1.15 SPDS—Safe Practice Data Sheets
3.1.16 TBC—Thermal Barrier Coating
4. Summary of Practice
4.1 Personnel Qualification/Certification—Vibroacoustic thermography is a new active thermography technique within the
method of infrared and thermal testing (see Practices E168). As the technique develops, it is expected that several sub-techniques
for energizing will be developed, refined, and documented. The current energizing variations require competence in areas of
materials, mechanics, and heat transfer. Therefore, early users are expected to be well versed in these areas to ensure conservative
applications. Because there is no existing single NDE method that matches all of the necessary skills, this first procedure requires
the responsible control of a certified Level III in the method of infrared and thermal testing in accordance with ANSI/ASNT
CP-189 or ASNT, SNTTC-1A. It is recommended that the Level III, under consultation with the responsible component engineer,
develop the necessary supplemental training requirements for Level I and Level II personnel. Inspections shall be conducted by
NDE Level I or Level II inspection personnel certified in accordance with ANSI/ASNT CP-189 or ASNT, SNTTC-1A. The NDE
Level I should be qualified to properly perform specific calibrations, specific NDE, specific evaluations and record results
according to written instructions. The NDE Level II should be qualified to set up and calibrate equipment, to interpret and evaluate
results with respect to applicable codes, standards and specifications and to organize and report the results of NDE.
4.2 Vibroacoustic Thermography Test System—The system consists of an ultrasonic exciter, an infrared camera, and operating
software to sequence the test and capture the result. The exciter is an ultrasonic piezoelectric transducer stack that may commonly
be used for ultrasonic welding (plastics industry) or vibrations testing. Depending on the specific method of energization, a booster
(amplifier) or a horn may also be used to augment, phase, couple, or focus the ultrasonic energy. Energization occurs for the first
0 - 8 seconds of test again depending on the energization method. During this time, the IR camera is triggered to capture resulting
active heating of the component defects. The images are labeled and stored for slow motion play back of the simple vibroacoustic
thermography movie, or for further analysis.
4.2.1 Ultrasonic System—Includes power supply and component fixture. Examples of these systems include a piezoeletric shaker,
or ultrasonic welder system. Specific power ratings (watts) and frequency (kHz) for the power supply and the converter are
essential to the vibroacoustic thermography inspection process and shall not be changed or modified without contacting system
manufacturer. Typical power ratings for a piezoeletric shaker system range from 800W - 4000W with typical frequencies ranging
from 14 000 Hz - 100 000 Hz. For ultrasonic welder systems, booster gain ratio, horn shape and horn material also are essential
to the vibroacoustic thermography inspection process and shall not be changed or modified without contacting system
manufacturer.
4.2.2 Infrared Thermal Camera—Thermal camera must have the sensitivity to achieve the required defect Probability of Detection
(POD) (7,), (8,), (9). Cooled MWIR (InSb) thermal cameras usually provide the best sensitivity (around 20 mK or better), whereas
LWIR microbolometer are generally less sensitive but may be adequate in many applications. Frame rates ≥30 Hz are generally
sufficient for vibroacoustic thermography measurements. Any resolution is adequate so long as the camera is close enough to the
specimen to resolve defect indications as in Practice E2585, subsection 6.1. This can be determined prior to test by use of a setup
specimen having a defect in it of similar thermal signal to that of the defects of interest in the inspected parts. (See Practice E1252.)
4.2.3 Minimum Software Requirements—The software should provide a method for triggering the excitation of the part and
recording the part response. The software should also provide a method for reviewing and analyzing the results.
4.3 System Calibration:
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4.3.1 If detection of certain critical defects is an engineering requirement, then a rigorous evaluation of capability and reliability
is required, including a proper POD study. Such an evaluation would consider process variability due to excitation, vibration, crack
location and orientation, crack closure, crack thermal response variability, non-uniformity of thermal camera field, and infrared
detection. General principles and guidelines for POD evaluation can be found in MIL-HDBK-1823A.
4.3.2 If there is no engineering requirement on defect detection, system capability can be estimated from samples with relevant
defects or samples with similar simulated defects, called reference standards or reference components. Use of these samples can
help confirm that the relevant defects are within the usual resolution and sensitivity limits of the IR NDE system.
4.3.3 Once reference standards or reference components have been established, the same sample(s) can be retested later to help
confirm proper system operation. Although it is not possible to define a universal reference standard, the following guidelines for
development of reference and calibration standards will apply to most commonly encountered NDE situations:
4.3.3.1 The reference sample should be constructed of similar material as the actual part.
4.3.3.2 The reference sample should have similar surface preparation as the actual part.
4.3.3.3 The reference sample should contain real or simulated defects which correspond to worst and best case defect scenarios,
with a reasonable range of severity, depth, and/or size or size, or a combination thereof, between these limits.
4.4 Development of Evaluation Criteria—A basis for accept/reject decisions must be developed. Procedures should be developed
by various engineering department representatives in harmony with certified Level III personnel, who are familiar with the
thermographic inspection equipment to be used, as well as the part to be inspected, its function, composition, and defect and failure
modes.
5. Specific Practices
5.1 Cleaning and Surface Preparation:
5.1.1 The cleaning and surfaces preparation process should be determined in conjunction with the creation of the inspection
process specification for the specific part and should be used to remove or limit the false indications that may arise from foreign
objects or contamination. The following is a description of the minimum recommended cleaning and surface preparation
requirements.
5.1.2 Visually inspect the examination area for defects that vibroacoustic thermography is not specifically designed to detect. This
may include dents, gouges, and other open indications where vibro-acoustically excited features will not interact to generate heat.
Remove foreign objects, or contamination that could interfere with the inspection. This includes any loose debris that may move
on the surface. Excess grease or oil should be wiped away. (See Terminology E1316.)
5.1.3 In rare cases, the emissivity of the surface may be low enough to reduce thermal emission from relevant indications. In this
case, the surface emissivity may be increased by application of a suitable coating. An example process for applying a coating to
improve surface emissivity of a part is described in Appendix X1. (See Practice E1933.)
5.2 Reference Standards:
5.2.1 There are two types of reference standards currently used for vibroacoustic thermography: cracked standards and
thermoelastic standards. Cracked standards require real cracks to cause a repeatable indication for standardization or reference.
Thermoelastic standards are typically attached polymers that heat up characteristically upon energization. Any of the following
standards may be used for the purpose of assuring a proper energization/ imaging energization/imaging process as well as
establishing a level of confidence for defect detection.
5.3 Reference Component—A component(s) having a known natural or fabricated defect in it may be used for a reference standard.
The reference standard should contain at least one defect of current and specific concern. A permanent record of a detailed defect
map of the reference component shall be maintained. This record shall include defect location, length, and orientation. The original
indication response shall be stored for reference. Additionally, an indication response for the reference component shall be included
in the inspection report for each heat or batch of components and for every shift or work per inspection station.
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5.4 Quality Indicator—A quality indicator is a simple and cost effective polymer tape consisting of an adhesive poster strip
attached to the test article (that is, 3M Command Poster Strips). The reference standard should always be used with an attached
quality indicator in the ROI. Quality indicators heat up upon energization of the test article to verify system operation. It is
recommended that quality indicators be used on every component of the testing cycle.
5.5 Examination Coverage—As with all image based NDE, the detection capability is limited by the spatial resolution of the
acquired image. In cases where the instantaneous field of view is insufficient to resolve the indication (that is, measured millimetres
per pixel times 2-5 pixel safety factor is less than the indication size), a special qualification should be conducted to demonstrate
adequate detection of relevant indications. The nature of the examination allows for repeat magnified examinations to zoom in on
an indication for characterization and orientation details. The following are requirements for image and coverage of the
examination.
5.5.1 Image Area Covered for Each Energization Cycle—It is recommended that the field of view (FOV) be sized to assure that
the reportable or rejectable defect dimension is no smaller than 2-5 pixels of Camera CCD element coverage for each image. For
large components where the ROI could be larger than the camera field of view, multiple examinations shall be needed. (See
Practice E1252.)
NOTE 3—For detection, the defect need not be spatially resolved, since the thermal diffusion broadens the detectable indication. If needed for
characterization, additional views with a closer camera or telephoto lenses may be used.
5.5.2 Camera Focus—It is recommended that the entire camera FOV be in focus during the vibroacoustic thermography test. The
camera is considered to be in focus if the required spatial resolution to detect the smallest indication of interest is maintained across
the camera FOV. In cases where this cannot be achieved (that is, because of part geometry or camera optics), the camera FOV shall
be considered reduced to the region of the CCD that is considered in focus. (See Practice E1252.)
5.5.3 Angle of Incidence—The entire ROI shall be imaged from an angle of incidence of less than 45 degrees f
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