No abstract

The work is devoted to energy saving during arc manual welding operations. Power sources for arc manual welding are rectifiers with slow or steeply falling current-voltage characteristics. The paper considers two ways of energy saving during arc welding operations. The first way is to increase the efficiency of welding by replacing the ballast rheostat with a special electronic device that regulates the welding current instead of the ballast rheostat. The second way is to increase the efficiency of the welding equipment by replacing a traditional one-bridge rectifier with the two-bridge economical rectifier. An approximate calculation of the annual economic effect from the replacement of a ballast rheostat by the electronic regulating device is given on the example of welding operations in a typical assembly shop.

Destruction processes of composite materials under lightning stroke effect have been studied. The results of characteristic damages of samples have been presented upon a series of tests conducted with standard lightning currents and those ones whose shape is close to actual lightning stroke. There have been exhibited distinctions between the levels of sample damages: in the second case significant damages of composite matrix external layers have been shown, among which multiple destructions of bundles of carbon fibers at a depth of several layers, layer delamination and cavities formed inside sample. There have been described the results of generalized analysis of damages obtained by applying nondestructive inspection methods: stereoscopic microscope investigation and X-ray microtomography. The mechanism of damages has been presented on the basis of obtained data. The results of testing electrical, mechanical, thermal properties of composite samples have been given upon a set of experiments for lightning current resistance.