In order to obtain ultrafine grained structure, commercially pure aluminium (Al 1050) plates were subjected up to 8 passes of Incremental Equal Channel Angular Pressing (IECAP) following route C. Plates in different stages of IECAP were joined using Friction Stir Welding (FSW). All welded samples were investigated to determine their mechanical properties and structure evolution in the joint zone. The joining process reduced mechanical strength of material in the nugget zone, which was explained by the grain growth resulting from temperature rise during FSW. Nevertheless, the obtained results are promising in comparison to other methods of joining aluminium
In this study, an Al-Mg-Si alloy was processed using via incremental equal channel angular pressing (I-ECAP) in order to obtain homogenous, ultrafine-grained plates with low anisotropy of the mechanical properties. This was the first attempt to process an Al-Mg-Si alloy using this technique. Samples in the form of 3 mm-thick square plates were subjected to I-ECAP with the 90 deg rotation around the axis normal to the surface of the plate between passes. Samples were investigated first in their initial state, then after a single pass of I-ECAP, and finally after four such passes. Analyses of the microstructure and mechanical properties demonstrated that the I-ECAP method can be successfully applied in Al-Mg-Si alloys. The average grain size decreased from 15 to 19 lm in the initial state to below 1 lm after four I-ECAP passes. The fraction of high-angle grain boundaries in the sample subjected to four I-ECAP passes lay within 53 to 57 pct depending on the examined plane. The mechanism of grain refinement in Al-Mg-Si alloy was found to be distinctly different from that in pure aluminum with the grain rotation being more prominent than the grain subdivision, which was attributed to lower stacking fault energy and the reduced mobility of dislocations in the alloy. The ultimate tensile strength increased more than twice, whereas the yield strength was more than threefold. Additionally, the plates processed by I-ECAP exhibited low anisotropy of mechanical properties (in plane and across the thickness) in comparison to other SPD processing methods, which makes them attractive for further processing and applications.
Statistical properties of Trichel pulses with AC voltages are studied, measuring simultaneously the frequency distributions of the apparent charge q and of the light intensity qL. The occurrence of quasi-Trichel pulses and negative streamers, in addition to regular Trichel pulses, is observed. It is established that, along with the normal conditions necessary for the occurrence of regular Trichel pulses, a sufficiently intense Malter emission of electrons is essential. If this intensity is insufficient quasi-Trichel pulses appear and if there is no emission negative streamers appear. The above types of partial discharge differ in certain properties, namely the range of values of q; the values of the ratio q/qL; the stability of the pulses with time and the spread of the times of occurrence on the negative half-cycle of the applied voltage.
StreszczenieMetoda bezotworowego nitowania blach swój rozwój zawdzięcza głównie zmieniającym się wymaganiom w przemyśle motoryzacyjnym ze względu na zastosowanie nowych materiałów, zwłaszcza na elementy karoserii, i konieczności ich efektywnego łączenia. Obserwowane tendencje do stosowania w konstrukcjach elementów lekkich, a przy tym wytrzymałych, wykonanych ze stopów aluminium, kompozytów, tworzyw sztucznych itd., są tego przykładem. W referacie zaprezentowano wybrane aspekty prób zastosowania procesu nitowania bezotworowego do łączenia blach miedzianych. Zastosowano opracowaną wcześniej procedurę modelowania numerycznego procesu tworzenia połączenia i jego obciążania. Analizy numeryczne zostały zweryfikowane eksperymentalnie przy wykorzystaniu przemysłowego stanowiska badawczego wykorzystującego specjalny przyrząd wyposażony w zaprojektowany tor pomiarowy. Do symulacji wykorzystano komercyjne oprogramowanie ogólne-go przeznaczenia MSC.Marc, służące m.in. do modelowania zjawisk o charakterze nieliniowym. Zaprezentowane wyniki mają charakter jakościowy i stanowią początek działań podejmowanych w ramach współpracy z firmą produkcyjną, mającej na celu optymalizację oraz opracowanie wewnętrznych wytycznych do projektowania połączeń blach miedzianych.Słowa kluczowe: nitowanie bezotworowe; łacznie miechaniczne; modelowanie numeryczne
AbstractThe self-piercing riveting -SPR -for sheet metal joining owes its development mainly to the changing requirements of the automotive industry due to the use of new materials, especially for the body parts, and the need for their efficient joining. The observed trends to use for the structural components lightweight, yet durable, aluminum alloys, composites, plastics, etc., are examples of this tendency. The paper presents selected aspects of the attempts to use the SPR method for joining copper sheets. A numerical modeling of the process of joint formation and its loading was introduced. These analysis were verified experimentally using an industrial set-up consisting of a mobile unit for riveting equipped with a specially designed components for a measuring track settting. Simulation were carried out with commercial software based on the finite element method MSC.Marc, dedicated for the nonlinear analysis. The presented results are of a qualitative nature and are the beginning of activities undertaken in cooperation with the production company, aimed at optimizing and developing internal guidelines for the design of copper sheet joints.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.