Pulse compression thermography for defect detection in CFRP

Roy, Deboshree; Indian Institute of Technology; India

Roy, D.; CARE, IIT Delhi; India
Tuli, S.; Bennet University; India

ID: ECNDT-0549-2018
Session: Thermography and Thermosonics Techniques 1
Room: H1
Date: 2018-06-15
Time: 10:00 - 10:20

The concept of pulse compression in thermography is an extension of the frequency modulated technique, where the chirped response of the sample is correlated with a reference signal to generate a pulse compression output. A relatively recent technique, it has certain advantages over conventional techniques like lock-in thermography, pulse and pulse-phase thermography. This paper introduces pulse compression and details the experimental setup used for thermal non-destructive testing (TNDT). The experimental set-up comprises of a low power LED excitation source along with ldr based reference acquisition system. Furthermore, an algorithm for removal of non-uniformity in heating for LED source is discussed in the paper. A novel pulse compression algorithm is described here. The excitation signal is a chirp that comprises of a band of frequencies. The novelty in algorithm lies in the removal of out of band noise with a filter. Results are provided for defect detection in CFRP which is widely used in industry. The sample is 7-mm thick with 4 and 6 mm defect diameter, and defect depth varying from 0.25 to 2.5 mm in 0.25 mm increment. The sample also has an impact damage.