Detection of Defects in Geomembranes Using Quasi-Active Infrared Thermography

High-density polyethylene geomembranes are employed as covers for the sewage treatment lagoons at Melbourne Water Corporation’s Western Treatment Plant, to harvest the biogas produced during anaerobic degradation, which is then used to generate electricity. Due to its size, inspecting the cover for defects, particularly subsurface defects, can be challenging, as well as the potential for the underside of the membrane to come into contact with different substrates, viz. liquid sewage, scum (consolidated solid matter), and biogas. This paper presents the application of a novel quasi-active thermography inspection method for subsurface defect detection in the geomembrane. The proposed approach utilises ambient sunlight as the input thermal energy and cloud shading as the trigger for thermal transients. Outdoor laboratory-scale experiments were conducted to study the proposed inspection technique. A pyranometer was used to measure the intensity of solar radiation, and an infrared thermal camera was used to measure the surface temperature of the geomembrane. The measured temperature profile was analysed using three different algorithms for thermal transient analysis, based on (i) the cooling constant from Newton’s law of cooling, (ii) the peak value of the logarithmic second derivative, and (iii) a frame subtraction method. The outcomes from each algorithm were examined and compared. The results show that, while each algorithm has some limitations, when used in combination the three algorithms could be used to distinguish between different substrates and to determine the presence of subsurface defects.

Numerical studies on damage of carbon/epoxy composites exposed to lightning strike

Lighter carbon fiber/epoxy composites are replacing metals in wind turbines blades, aircraft structures, marine structures, automotive skins & other applications. Lightning strike damage is a real threat to these materials during service life. Along with experimental studies, their damage predictions by numerical methods are being attempted by various researchers. The numerical simulation of this damage by coupled thermal–electric (transient) analysis and thermal transient analysis is presented in this article. In this study, damage predictions based on thermal profiles are carried out, and suitable validations with earlier published work are discussed.

Skorohod-Olevsky viscous sintering model sensitivity to temperature distribution during the sintering process

This paper investigates the influence of temperature field non-uniformity on sintering simulation results using the Skorohod-Olevsky viscous sintering model. As a difference to previous studies, here a thermal transient analysis is performed to provide a detailed temperature field over the component within sintering time. Results obtained using uniform temperature distribution are compared to those obtained using a nonuniform distribution derived from a transient thermal analysis. Results are compared for different geometry sizes, that lead to different temperature non-uniformity levels. The study has shown that the temperature nonuniformity cannot always be neglected and should be considered as a possible source of modeling error.

Analysis of the distribution of temperature fields in the braked railway wheel

The article deals with detection of reduced stress in a braked railway wheel, based on thermal transient analysis on virtual models, which influence the characteristics of the railway wheels. Structural analysis was performed by means of the ANSYS Multiphysics program system package. Thermal transient analysis deals with detection of temperature fields which are a result of braking by brake block. The applied heat flux represents the heat generated by friction of brake block. It is applied to a quarter model of the wheel to speed up the calculation. This analysis simulates two braking processes with subsequent cooling. Distribution of the equivalent stress was detected in the railway wheel cross section, at selected points. The input parameters were taken from the thermal transient analysis. These equivalent stresses result from thermal load.