Srećko Švaić

Determination of the defect parameters in a specimen by means of thermography and numerical methods

Applying thermography in thermal non destructive testing (TNDT) gives the new possibilities in detection and defining of the defects in material. Because the temperature distribution on the material surface reflects the situation of its inside structure (including possible defects) each disturbances of temperature field can be used for estimation of the material homogeneity. Numerical methods enables the simulation of unsteady heat transfer through the material, giving the surface temperature distribution for various defects in material. Therefore they help a lot in TNDT research. The paper presents the results of the research carried out on the specimen having different defects under material surface, by means of both mentioned methods.

Evaluation of cutaneous flap survival by IR thermography

There are plenty of recent studies showing the influence of different drugs on the survival of the cutaneous flap. The effects of a topically applied capsaicin, methylprednisolon, mitomycin and gastric pentadecapeptide BPC-157 in improving skin vitality and preventing distal flap necrosis were tested in a random-pattern dorsal skin flap model. Wistar rats were randomized into five groups, four experimental groups and a control group. A standardized full thickness dorsal random-pattern skin flap was raised on each rat and sutured back into place. A gelatin sponge was placed before suturing between the flap and its recipient bed, with 0.9% saline in the control group and with capsaicin, methylprednisolon, mitomycin and pentadecapeptide BPC157 in the experimental groups. The flap survival was judged one

Characterization of subsurface defects by means of thermography and 3D numerical model

The paper presents the method for determining the subsurface defects in material by means of active thermography and 3D numerical non-stationary heat conduction model. Determination of the subsurface defects by Thermal Non- Destructive Testing means the description of the defects dimensions and its location. The method is tested on the samples made of metal and composite materials having known subsurface defects. The results obtained are discussed from the point of view of influence of the neighboring defects on the current contrast curve and possibilities of predicting the behavior of the composite material by estimation of their thermal properties. The software developed enables the calculation of the temperature distribution through the sample versus time and location of the defect by means of inverse method involving experimentally obtained thermogram.

Heat treatment of metals optimized by numerical simulation based on infrared thermographic measurement

The analysis of complex probe geometry heating and cooling was done with the aim to find the temperature distribution inside the probe versus time. An infrared thermography was used to measure surface temperatures while temperatures in control points inside the probe were measured with thermocouples. The results obtained by numerical model based on the control volume approach, where thermographic measurements were the input parameters, show good mutual accordance with those measured by thermocouple at referent points of the probe. Applied on heat treatment of metals, this method provides a possibility to monitor temperature change for each single point inside the probe in a way which will guarantee that the desired microstructure is obtained. The local and average heat transfer coefficients have also been calculated by means of a numerical model. Based on the data, it is possible to simulate similar processes without providing measurements for all possible setups of the furnace parameters. Additional optimization is possible when experimental rig for real time calculation of temperature fields (measurement and calculation at the same time) will be realized.

Mathematical models for simulation of cooling processes using infrared surface-temperature measurement

Mathematical models developed for the simulation of cooling processes are presented in the paper. The input parameters for the models are the data obtained by IR surface temperature measurement. The models enable the calculation of the temperature distribution inside the probe versus time, as well as the calculation of the local heat transfer coefficients. Also they can be used for the simulation of the cooling process. The developed software is given as an integral package intended for the analysis of quenching processes.