Applied Engineering Letters

115-123

Authors: L. Ramesh, P. Srinivasa Rao

In this paper, a new modal parameters-based damage detection method has been proposed for accurate characterization of single and multi-surface cracks in beam-like structure. The advantage of this method is undamaged mode profiles from the damaged mode profiles of beam structure. For that, curve fitting (CF) analysis was used to extract the undamaged mode profiles from damaged one. Discrete Wavelet transformation (DWT) method is presented to demonstrate effectiveness of the proposed approach without use of base line data as a reference. To illustration of this method, numerical and experimental modal analysis is performed on two aluminum cantilever beams containing single and double cracks to examine the location and quantification of different damage scenarios. First five modal frequencies and mode profiles are employed to assess the effectiveness of the proposed method. Moreover, to validate the accuracy of the proposed approach in damage identification, established results have been balanced with other experimental based results, which were found in the literature. From the results, it can be seen that damage scenarios of the two beams are quite different the chosen methods precisely identify the location and quantification of the damage in beam structures. It is concluded that composed mode profiles by the proposed approach can be conveniently used as reference data for the damage identification purpose.

129-134

Authors: J. Skerlic, D. Nikolic, D. Cvetkovic, A. Miškovic

Solar energy is the most abundant, inexhaustible and clean of all the renewable energy resources till today. Solar energy has received much more attention in building energy systems in recent years. During the first years of the twenty-first century, extensive efforts have been undertaken to alleviate global warming of the earth caused by emission of CO2 in atmosphere. These emissions are generated by intensive burning of fossil fuels to satisfy the growing energy needs of humanity. The emissions may be mitigated when part of energy needs is satisfied by using non-polluting energy sources such as solar energy, instead of fossil fuels. In households, customary is to use electricity for heating of DHW. Most of electricity is produced by using coal with high greenhouse emission. Accordingly, worldwide, the most rewarding application of solar energy is when it replaces electrical energy for heating of DHW in households. The solar collector has to take the optimal position that will guarantee the highest generation of heat. Optimal positioning must be based on rigorous calculations and not on the basis of experience. Such calculations lead to the improvement of the operation of solar energy systems. This paper gives a review of research with the objective of presenting, classifying and analysing the different criteria by which the authors observed an optimal position of the solar collector. In addition, it is important to have a high efficiency of conversion of solar energy to heat. Then, the highest amount of avoided primary energy, avoided electrical energy, avoided exergy, and decrease in CO2 emissions may be expected.