The intensity of the infrared radiation emitted by objects is mainly a function of their temperature. In infrared thermography, this feature is used for multiple purposes: as a health indicator in medical applications, as a sign of malfunction in mechanical and electrical maintenance or as an indicator of heat loss in buildings. This paper presents a review of infrared thermography especially focused on two applications: temperature measurement and non-destructive testing, two of the main fields where infrared thermography-based sensors are used. A general introduction to infrared thermography and the common procedures for temperature measurement and non-destructive testing are presented. Furthermore, developments in these fields and recent advances are reviewed.

/pdf/infrared-thermography-for-temperature-measurement-and-non-2r2amijcr4.pdf

Infrared thermography for temperature measurement and non-destructive testing.

A review of ultrasonic testing applications in additive manufacturing: Defect evaluation, material characterization, and process control.

Actively modulated acoustic nondestructive evaluation of concrete

Since concrete members with fiber-reinforced polymer (FRP) reinforcement are not as ductile as conventional structures, and since concrete in retrofitted members is often covered and not readily available for visual inspection, development of nonintrusive and nondestructive damage assessment tools is essential. Ultra- sonic pulse velocity (UPV) can provide such an assessment tool, and help quantify the extent and progression of damage in concrete. Continuous UPV monitoring of a number of concrete cylinders and concrete-filled FRP tubes showed the concrete-filled tubes to have higher sensitivity at lower stress ratios as compared to plain concrete. When compared with the axial strain energy, the UPV damage index has a much better resolution for stress ratios up to about 50% of ultimate strength. This ratio depends on the thickness of the jacket. It was also shown that the UPV has a strong correlation with volumetric strains after confinement is activated. Therefore, at high levels of axial loads when the confining pressure of the jacket results in volumetric compaction, the UPV increases by about 6% of the initial pulse velocity. Repeated loading generally induces the same rate of change of UPV damage index as that of the initial loading on the virgin specimen. This phenomenon occurs irrespective of the stress ratio at which the specimen is unloaded or reloaded. A comparison of the UPV damage index with the normalized acoustic emission counts reveals that the two methods have different sensitivities at different stages of loading and could potentially complement each other as a hybrid damage assessment tool.

Damage assessment of frp-encased concrete using ultrasonic pulse velocity

Characterization of thermally damaged concrete using a nonlinear ultrasonic method

In recent years, the ultrasonic signal-processing technique, which has been enormously successful in material testing, has found few applications in the analysis of concrete damage because of the heterogeneous nature of this material. In the present study, frequency-domain analysis of the ultrasonic signals, based on the Segmented Chirp Z-Transform, has been used to both detect and monitor the crack growth in structural materials. In comparison with the usual methods of pulse velocity or attenuation measurement, a very sensitive and accurate testing method was obtained. The experimental setup is described and the preliminary results, relating to uniaxial compression tests carried out on cubic concrete specimens and bricks, discussed. >

Ultrasonic signal-processing techniques for the measurement of damage growth in structural materials

The frequency-domain analysis of ultrasonic signals was used to detect and to monitor crack growth in structural materials. A testing technique that is very sensitive and accurate in comparison with usual methods of pulse velocity or attenuation measurement was obtained. The experimental setup is described, and results are discussed in relation to uniaxial compression tests made on concrete cubic specimens or on bricks. >

R.S. Olivito

Papers

Ultrasonic signal-processing techniques for the measurement of damage growth in structural materials

Frequency-domain analysis of ultrasonic pulses for the measure of damage growth in structural materials

Metodi ultrasonici per il rilevamento del danno nel calcestruzzo: analisi nel dominio del tempo e della frequenza