In Japan it happens that concrete parts suddenly collapse to create obstacles to the traffic in tunnels, on highways and bridges. Thus, the safety issue has become a serious social problem. Therefore, the detection of hidden defects in concrete building constructions in order to prevent an accidental damage is the important application area for nondestructive testing (NDT) techniques. Until now, the inspection is typically performed by using a hammer that is subjective and takes too much time. Infrared thermography is a promising NDT technique that might help in the fast detection of invisible (hidden) defects. Transient, or active, thermal NDT requires external thermal stimulation of the objects under test by warming up or cooling down the object surface. However, low-power and long heating is significantly affected by environmental conditions. Recent Japanese research in this area has been rather qualitative, i.e. without putting the accent on evaluating parameters of hidden defects. In this study, the experimental results are modeled and processed by using the thermal NDT software package developed at the Tomsk Institute of Introscopy. This has allowed not only optimizing test parameters but also obtaining reasonable estimates of defect parameters for air-filled voids and inclusions in concrete. It is shown that MRTD values measured by ourselves for the first time are of a little help while evaluating detection limit.
An experimental study of detecting a spot temperature of the dry friction interface was conducted by means of infrared radiometry. The radiation temperature distribution of the plastic dry friction interface was displayed on the CRT of the infrared radiometer (IR). The radiation temperature distribution of the reciprocating interface T, and the friction coefficient Il were continuously measured. The thermal behavior of the excess hot-spot temperature area of the friction interface under heavy wear condition showed that the time-dependent fluctuation of the temperature and friction coefficient was caused by the generation process of the deposited wear powder in the interface.
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