Overview
ISO/TR 13115:2011 provides standardized procedures for the absolute calibration of acoustic emission transducers using the reciprocity technique. The Technical Report describes three complementary calibration methods - three‑transducer calibration, two‑transducer calibration, and impulse response calibration - to determine frequency and impulse responses (absolute sensitivity) of acoustic emission sensors for both Rayleigh surface waves and longitudinal waves. The report also specifies how to prepare the transfer medium, mount transducers, select calibration signals, and represent calibration results.
Key topics and technical requirements
- Reciprocity technique: Primary method where three reversible transducers of the same kind form three independent transmit/receive pairs on a solid transfer medium. Absolute sensitivity is derived from electrical measurements of transmission current and reception voltage.
- Three‑transducer calibration: Determines amplitude frequency responses of reception voltage sensitivity and transmission current response for each reversible transducer.
- Two‑transducer calibration: Uses one previously calibrated transducer (from the three‑transducer method) to determine reception sensitivity of an optional (not necessarily reversible) transducer.
- Impulse response calibration: Measures complex frequency responses (amplitude and phase) via reciprocity and obtains impulse responses through inverse Fourier transform; uses Hanning windows for time‑domain processing.
- Transfer medium and material: Carbon/forged steel is recommended; the medium must be ultrasonically tested (2–5 MHz) to ensure no flaws producing reflections greater than 10% of the first back‑wall reflection. Surfaces for longitudinal calibration should be parallel within 0.2°.
- Mounting and coupling: Contact surface pressure should be at least 0.1 MPa; appropriate couplant (e.g., machine oil on steel) and controlled surface roughness are required.
- Calibration signals: Tone burst signals and squared‑cosine envelopes are used for frequency calibration; period selection and signal design account for wave propagation and separation of direct vs. spurious waves.
Practical applications
- Establishing traceable, repeatable sensor sensitivity for acoustic emission (AE) inspections.
- Creating consistent AE datasets for structural health monitoring, materials testing, and failure analysis.
- Supporting manufacturers of AE transducers with acceptance testing and characterization.
- Enabling calibration laboratories and NDT (non‑destructive testing) service providers to certify sensor performance for Rayleigh and longitudinal wave detection.
Who should use this standard
- Calibration laboratories performing primary or secondary calibration of AE sensors
- NDT engineers and technicians responsible for acoustic emission inspection quality control
- AE transducer manufacturers and R&D teams characterizing sensor frequency and impulse responses
- Researchers and metrology organizations seeking standardized reciprocity‑based calibration methods
Related topics / keywords
Non‑destructive testing, acoustic emission, reciprocity technique, three‑transducer calibration, two‑transducer calibration, impulse response, absolute sensitivity, transfer medium, Rayleigh waves, longitudinal waves, sensor calibration, calibration laboratory.