A. O. Chulkov

Water detection in honeycomb composite structures using terahertz thermography

Experimental results on the detection of latent water in a honeycomb fiberglass structure using terahertz thermography are presented. These data are compared with data that were obtained using active infrared thermography.

Detecting corrosion in thick metals by applying active IR thermography

Both theoretical and experimental results obtained by applying active infrared thermography to the inspection of hidden corrosion in 1-10 mm thick steel samples are presented. The emphasis is put on the comparison of heating and data processing techniques.

IR thermographic characterization of low energy impact damage in carbon/carbon composite by applying optical and ultrasonic stimulation

This study is intended to establish quantitative relationships between impact damage energy and some thermal NDT parameters in application to carbon/carbon composites. When applying uniform optical stimulation, the used approach involves the synthesis of effusivity/diffusivity images respectively in one- and two-sided test procedures. Ultrasonic stimulation of composites has also proven to be attractive due to its special applicability to detect micro-cracks. However, quantitative relationships between temperature signals and impact energy are still to be studied.

An apparatus for the active thermal testing of corrosion in steel cylindrical containers and test results

An apparatus that works on the thermal-testing principle involving infrared thermal imagers of different types and optical and convective heating devices is described. The main purpose of the apparatus is to detect hidden corrosion in 1- to 2-mm-thick steel containers that are intended for temporary storage of radioactive wastes.

Active thermal testing of hyperthermoconductive panels

Application of active infrared thermography to assessing the internal structure and functioning of hyperthermoconductive panels used in on-board electronics is described. Effective thermal- diffusivity maps of hyperthermoconductive panels, obtained using the pulsed Parker method, are presented. The peculiarities of heat transfer in hyperthermoconductive panels are illustrated using experimental modeling in which a local thermal-load source is placed on the surface of hyperthermoconductive panels.

A LED-based thermal detector of hidden corrosion flaws

Results of using powerful LED matrices to inspect metal articles for hidden corrosion by active thermal-wave method are described. The effect of the color of paint-and-lacquer coating on the efficiency of heating with LED and halogen emitters is analyzed. The possibility of using powerful LED panels as thermal stimulation sources in portable flaw detectors is described.

Inspecting aviation composites at the stage of airplane manufacturing by applying 'classical' active thermal NDT, ultrasonic IR hermography and laser vibrometry

The results of applying three nondestructive testing techniques to the inspection of parts of a new Russian TVS-2DTS airplane made of carbon fiber reinforced plastic are presented. A basic technique implemented in workshop conditions implements optical stimulation of inspected parts. The usefulness of ultrasonic infrared thermography combined with laser vibrometry in the evaluation of parts with complicated geometry is illustrated. Samples with artificial and real defects have been tested in workshop conditions.

An Automated Practical Flaw-Identification Algorithm for Active Thermal Testing Procedures

Results of analyzing the infrared thermograms of flawed carbon-, glass-fiber reinforced composites steel, and aluminum samples obtained in active thermal-testing procedures are described. The reproducibility of the results of testing conducted by thermography operators using manual and automated image-processing procedures has been evaluated. The advantage of an automated thermogram-analysis algorithm that halves the spread in informative parameters over manual data processing has been demonstrated.

Quantitative evaluation of water content in composite honeycomb structures by using one-sided IR thermography: is there any promise?

The problem of moisture accumulation in airplane honeycomb panels is so serious that perspective aviation constructions could become monolithic or filled in with special foam. However, the number of airplanes with plentiful honeycombs under exploitation will keep very high in the few next decades. Therefore, quantitative water detection remains an actual task in aviation. The qualitative aspect of this problem can be solved by using the remote and fast technique of infrared thermography. Hidden water can be detected for a certain period of time after landing, or some stimulation heat sources can be used to enhance water visibility in honeycomb panels. However, quantitative evaluation of moisture content is typically achieved by applying a point-by-point ultrasonic technique which allows measuring the height of the water bar in single cells thus compiling maps of water distribution. This technique is contact and can be enough informative when applied to the water which is in contact with the panel skin because of gravitation. The use of solely infrared thermography for evaluating accumulated water mass based on the analysis of temperature patterns is difficult. Recently we found that there is a certain promise in the thermographic determination of water content, but the question is how precise (or how approximate) can be such estimates. The paper contains modeling and experimental results obtained in this direction.

Estimating the humidity of wood by terahertz infrared thermography

The usage of terahertz infrared thermography for assessing the humidity of wooden samples is described. Terahertz radiation transmitted through a sample is imaged by means of a tera-thermoconverter. The temperature field of the converter is analyzed with an infrared imager. The possibility of using the technique for testing the nonuniformity of drying of timber is illustrated.