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The paper aims to report preliminary researches towards to development of new hybrid welding system by coupling a microwave beam with a TIG torch. The main research was focused on the designing of hybrid system as well as to establish the heating/welding mechanism by coupling two different thermal sources. Therefore, a specific welding chamber was designed taking into consideration the limitations provided by microwave waveguide technical specs, geometrical shape and dimensions of the TIG torch as well as the temperature monitoring during welding process and video surveillance for data recording. A microwave generator with adjustable power from 0 to 1250 W was coupled with a TIG torch and welding power source in order to establish the main parameters for hybrid system. The preliminary researches reported that the MW-TIG hybrid welding could be applied to eutectic joining of materials using low power (up to 600 W) injected from microwave generator as well as low welding current (up to 20 A). The flow of shielding gas have been established initially to 2 l/m. The research related to stabilization of MW-WIG plasma arc have been studied by increasing the flow of shielding gas up to 10 l/m. The results have shown that the microwave generator and TIG torch can be coupled to obtain hybrid-welding process without any matching tuning devices but with risks for damaging the microwave generator. Further researches will be done in order to design auxiliary devices to optimize the hybrid-welding process and to avoid any unwanted plasma arc discharge from welded base materials to microwave generator. In terms of temperature monitoring, an infrared pyrometer has been used. The IR pyrometer was targeted to the base materials in order to be able to measure their temperature without any influences from plasma arc. The results obtained have shown a stable plasma at average microwave power around 400 W even without any TIG current.

Developing a non-destructive method which delivers fast, accurate and non-invasive results regarding the concrete compressive strength, is an important issue, currently investigated by many researchers all over the world. Different methodologies, like using the simple non-destructive testing (NDT) or the fusion of different techniques approach, were taken into consideration in order to find the optimal, most suitable method. The purpose of this paper is to present a new approach in this direction. The methodology consists in predicting the concrete compressive strength through ultrasonic testing, for non-destructive determination of the dynamic and static moduli of elasticity. One important, basic assumption of the proposed methodology considers values provided by technical literature for concrete dynamic Poisson’s coefficient. The air-dry density was experimentally determined on concrete cores. The dynamic modulus of elasticity was also experimentally determined by using the ultrasonic pulse velocity (UPV) method on concrete cores. Further on, the static modulus of elasticity and the concrete compressive strength can be mathematically calculated, by using the previously mentioned parameters. The experimental procedures were performed on concrete specimens, namely concrete cores extracted from the raft foundation of a multistorey building; initially they were subjected to the specific NDT, namely ultrasonic testing, and the validation of the results and the proposed methodology derives from the destructive testing of the specimens. The destructive testing is generally recognized as the most trustable method. The precision of the proposed method, established with respect to the destructive testing, revealed a high level of confidence, exceeding 90% (as mean value). It was noticed that even the cores with compressive strength outside of mean range interval (minimum and maximum values) presented high rate of precision, not influencing the overall result. The high rate of accuracy makes this method a suitable research background for further investigations, in order to establish a reliable NDT methodology which could substitute the very invasive and less convenient, destructive method.