Overview
ISO 22290:2020 - "Non‑destructive testing - Infrared thermographic testing - General principles for thermoelastic stress measuring method" defines general principles for using thermoelastic effects in infrared thermography to measure surface stress distributions in industrial NDT. The standard describes personnel qualifications, test environment and equipment requirements, signal‑processing techniques, load and imaging methods, calibration, and reporting essentials for reliable thermoelastic stress measurements.
Key topics and technical requirements
- Scope & terminology: Applies to thermoelastic stress measuring as a full‑field, noncontact method for mapping surface principal stresses. Terminology aligns with ISO 10878.
- Personnel: Operators must meet qualification and certification requirements referenced in ISO 9712 and training syllabuses in ISO/TS 25107.
- Test environment: Control temperature, humidity and atmosphere per ISO 10880; avoid condensation, vibration‑induced blur and air currents that alter surface temperature.
- Equipment configuration: Typical setup includes a material testing machine, test object, infrared camera, reference load/displacement signal and a computer with signal processing (schematic in the standard).
- Infrared camera:
- Recommended spectral bands: about 3–5 µm or 8–14 µm to detect very small temperature changes.
- Frame rate must provide sufficient frames per load cycle.
- Spatial resolution determined by lens view angle, pixel count and camera distance.
- Temperature resolution guidance: ~0.001 K needed to resolve 1 MPa in steel; NETD on the order of 0.03 K can be improved with image processing.
- Surface preparation: Uniform, high emissivity (close to 1.0) surfaces are required. A thin matte black coating (emissivity > 0.95; optimal thickness 20–30 µm) or sanded polymer surfaces are recommended.
- Signal processing & imaging: Use temperature‑difference imaging, lock‑in techniques, or equivalent methods synchronized to a reference signal (load, displacement, or strain gauge) to extract thermoelastic temperature changes.
- Load conditions: Apply sinusoidal cyclic loading with controlled average, amplitude and frequency; preliminary tests to choose ranges where normalized temperature change is stable.
- Calibration, implementation & reporting: Procedures for stress calibration, detailed recording of test conditions, and structured reporting are specified.
Applications and users
ISO 22290:2020 is intended for engineers and technicians in:
- Aerospace and aviation structural testing
- Automotive component validation
- Electronics and medical device stress analysis
- Materials testing laboratories and R&D groups
- NDT service providers implementing infrared thermoelastic measurements
This standard helps practitioners design experiments, select suitable infrared cameras and processing methods, prepare specimens, and produce traceable stress maps for inspection, failure analysis and product development.
Related standards
- ISO 10878 - Infrared thermography vocabulary
- ISO 10880 - Infrared thermographic testing - General principles
- ISO 9712 - NDT personnel qualification and certification
- ISO/TS 25107 - NDT training syllabuses
Keywords: ISO 22290:2020, thermoelastic stress measuring, infrared thermography, NDT, lock‑in technique, temperature resolution, emissivity, NETD, infrared camera.
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