The Influence of Process Parameters on Microstructure and Mechanical Properties of Friction Stir Welded Al 5083 Alloy Lap Joint

Abstract Recently the aircraft and military industries widely have been using aluminum alloys particularly because of their fine strength to weight ratio. However in compare with steels they represent welding difficulties and also lower ductility. In last years it has been observed that Friction Stir Welding (FSW) method represents better microstructure and mechanical properties than conventional methods in welding aluminum alloys. In this study experiments were performed to investigate the effects of FSW process parameters including rotational and welding speed on the microstructure and mechanical properties of aluminum 5083 alloy in lap joint welding and different joint defects were analyzed. It was observed that the nugget area had the best grain size and also higher hardness in compare with the other welding areas. Also the best joint properties were achieved at the rotational speed of 825rpm and welding speed of 32mm/min

Spatial Aspects of Public Areas Affecting the Researchers Creativity and Innovation in an Architecture and Urban Design Research Center Print

Nowadays، creativity and innovation، particularly in the field of research، are of an extreme importance. Group activities have a key role in this area. Accordingly، and owing to the effect of spaces on human beings، this paper has focused on the identification of space aspects that increase the researchers’ creativity and innovation in an “architecture and urban design research center”. To achieve a set of desirable architectural attributes of the center’s public areas، four factors influencing creativity and innovation were taken into account which includes tranquility/physical comfort، motivation، creative thinking، and communication. Also، four spatial aspects، which affect these factors، were considered as privacy، beauty، spatial diversity/flexibility، andproximity/visibility. On the basis of the aforementioned factors and spatial aspects، a four-point Likert scale questionnaire was prepared to gather the researchers’ opinions. The statistical approach of Repeated Measure Analysis of Variance (RM-ANOVA) in the environment of SPSS software was employed to assess the questionnaires’ data. The rankings of factors influencing on the innovation and creativity، from the perspective of being affected by spatial aspects، were accordingly extracte

Badania eksperymentalne rozkładu temperatury i mikrostruktury materiału w etapie zagłębiania procesu spawania tarciowego z przemieszaniem z wykorzystaniem narzędzia o trójkątnym trzpieniu

Considering the developing role of the friction stir welding in manufacturing industry, a complete study on the process is necessary. Studies on each stage of the process in particular, provide a better understanding of friction stir welding, and specially friction stir spot welding. In this study, plunge stage has been studied by experimental methods for investigating the temperature distribution around the tool during the plunge stage and microstructure changes of the workpiece. Experiments were performed on aluminium 7050 plates with coincident measurement of temperature. In the study, the tool which has a triangle pin is used. The results of this study are used as initial conditions for theoretical analysis of welding process. The results show that the temperature distribution around the tool is quite asymmetric. The asymmetric distribution of temperature is due to nonuniform load distribution underneath the tool and tilt angle of it. The temperatures of the points behind the tool are higher compared with points located forward the tool. Microstructural studies showed that four regions with different microstructures are formed around the tool during the process. These areas were separated based on differences in grain size and elongations. Grains near the tool are elongated in a particular direction that show the material flow direction.Z uwagi na rozwojową rolę spawania tarciowego z przemieszaniem w przemyśle wytwórczym niezbędne jest całościowe badanie tego procesu. W szczególności, badania poszczególnych etapów procesu umożliwiają lepsze zrozumienie właściwości spawania tarciowego, zwłaszcza punktowego spawania tarciowego z przemieszaniem. W pracy badano metodami eksperymentalnymi etap zagłębiania w celu wyznaczenia rozkładu temperatury wokół narzędzia i zmian w mikrostrukturze elementu spawanego. Eksperymenty przeprowadzono na płytach z aluminium 7050, wykonując jednoczesne pomiary temperatury. W badaniach użyto narzędzia o trójkątnym trzpieniu. Wyniki badań są wykorzystane jako warunki początkowe dla teoretycznej analizy procesu spawania. Wyniki pokazują, że rozkład temperatury wokół narzędzia jest wyraźnie asymetryczny. Asymetria ta jest wynikiem nierównomiernego rozkładu nacisku pod narzędziem oraz pochylenia narzędzia pod określonym kątem. Temperatury w punktach poza narzędziem były wyższe niż te w punktach przed nim. Badania mikrostruktury ujawniły istnienie czterech obszarów, o różnych mikrostrukturach, które formują się wokół narzędzia w trakcie procesu. Obszary te wyróżniają się rozmiarami i kształtem ziaren. Ziarna w pobliżu narzędzia są wydłużone w określonym kierunku, który wskazuje kierunek płynięcia materiału

Morphology, Optical and AC Electrical Properties of Copper Phthalocyanine Thin Films

AC electrical properties of sandwich devices composed of thermally evaporated thin films of copper phthalocyanine (CuPc) with aluminum and gold electrodes (Al/CuPc/Au) are investigated over frequency (f) range of $10^2 - 10^5$ Hz and temperature range of 293-453 K. Morphology of the samples was studied via field emission scanning electron microscope images and X-ray diffraction micrographs. The X-ray diffraction micrograph indicates the configuration of α-CuPc with the (510) plane as the preferred orientation. UV-Vis absorption spectrum was analyzed and the optical band-gap energy of CuPc thin film was determined to be 2.81 ± 0.01 eV. Capacitance increased with increasing temperature especially for $f = 10^2$ Hz. Loss factor decreased considerably with increasing frequency to a minimum value at about $f = 10^4$ Hz and increased afterwards. Capacitance is generally independent of frequency for T ≤ 413 K; however it decreases remarkably with increasing frequency for T > 413 K. The conductivity increases quite noticeably with increasing frequency particularly for T ≤ 413 K. The AC electrical characteristics are in good agreement with Goswami and Goswami model. According to our data, at high temperatures, the band theory is applicable in describing the conduction process, whereas hopping mechanism is dominant at low temperatures