One of the friction-stir welding (FSW) limitations is joining thin sheets in sheet-metal manufacturing. To solve this limitation, thicker sheets can be welded with FSW and then rolled to a thinner ...thickness. This can improve the mechanical properties and save the weld zone soundly. In this work, 3-mm aluminum sheets were joined with FSW. The microstructure and mechanical properties of the samples were assessed at various rotational speeds (w) and travel speeds (v). Then, the welded samples were cold worked (CW) by rolling them at different percentages so that the samples were 2 mm and 1 mm thick. The effects of welding and post rolling on the mechanical properties and a failure analysis were deliberated. It was shown that welding reduces the transverse ultimate tensile strength (UTS) of FSWed samples by up to 29 % compared to the UTS of the base metal (BM), while rolling FSWed samples increased the UTS of the cold-worked FSWed samples by up to 94.7 % in comparison to the UTS of FSWed samples. Also, during the tensile test of the specimens FSWed at a lower travel speed, a fracture occurred at the stir zone (SZ)/thermo-mechanically affected zone (TMAZ) interface, on the advancing part; however, at a higher travel speed, it occurred at the interface of the heat-affected zone (HAZ) and TMAZ, on the retreating part. Moreover, during the tensile test of the cold-worked FSWed samples, the failure took place at the HAZ and the interface of the SZ and TMAZ, respectively. The UTS was risen by increasing the cold work. The UTS of a specimen FSWed at 50 mm/min and 1200 min–1 went up from 76 MPa to 124 MPa due to 33-% cold work and to 148 MPa due to 66-% cold work; meanwhile, the fracture occurred at the SZ/TMAZ interface or TMAZ of most of the post-rolled FSWed samples.
In this present work friction stir welding of Al6061-annealed pure copper dissimilar metals with square wave pattern tool pin movementwas investigated. The aim of this experiment is to identify the ...significance square wave tool movement on friction stir welding process along with three different tool pin profiles. Different tool pin profiles of square, round and hexaspiral shapes were selected and their significant outcomes were unveiled. Friction stir welding process parameters of 1500 and 2000rpm & tool pin movement step size of 1.0mm and 2.0mm & weaving rate of 100mm/min and 150mm/min were selected. The advantages of tool movement pattern and tool pin profile shape wereexamined by mechanical testing, microstructure analysis. The mechanical results were showed that process parameter of 1500 rpm, 1.0mm step size, weldingrate of 150mm/min and square tool pin profile combination gives better mechanical properties. Micro structural results unveiled achievement of better grain refinement and uniform dispersion of micro constituents by implementation of square wave tool pin movement pattern along with square tool pin profile.The EDAX report confirms that the weld nugget contains both aluminum and copper as equal percentage, which indicates fine mixing of two parent metals.
In this paper we will describe the process of the deposition of thick layers of VPS-Ti coating, which is used as a bonding layer for the upper porous Ti coatings on implant substrates. In order to ...deposit the powder, we used HÖGANÄS Ti powder labelled as AMPERIT 154.086 -63 µm. In order to test the mechanical properties and microstructure of the VPS-Ti coating, the powder was deposited on Č.4171 (X15Cr13 EN10027) steel substrates. Mechanical tests of the microhardness of the coating were performed by the Vickers hardness test method (HV0.3) and tensile strength by measuring the force per unit area (MPa). The microhardness of the coating is 159 HV0.3, which is consistent with the microstructure. The coating was found to have a good bond strength of 68 MPa. The morphology of the powder particles was examined on a scanning electron microscope. The microstructure of the coating, both when deposited and etched, was examined with an optical microscope and a scanning electron microscope. By etching the coating layers, it was found that the structure is homogeneous and that it consists of a mixture of low-temperature and high-temperature titanium phases (α-Ti + β-Ti). Our tests have shown that the deposited layers of Ti coating can be used as a bonding layer for porous Ti coatings in the production of implants.
W artykule przedstawiono trzy metody badań nieniszczących: metodę magnetycznej pamięci metalu, szumu Barkhausena i niskoczęstotliwościowej impedancji. Zwrócono uwagę na niejawny, nieliniowy związek ...istniejący pomiędzy parametrami mechanicznymi i elektromagnetycznymi materiału, a stanem jego wytężenia i degradacji. Omawianą tematykę zobrazowano przykładami, na podstawie których wykazano celowość uwzględnienia charakterystyk częstotliwościowych parametrów elektromagnetycznych materiału w opisie symptomów diagnostycznych metody magnetycznej pamięci metalu i szumu Barkhausena. Comparison of diagnostic capabilities of metal magnetic memory method, Barkhausen noise method and low-frequency impedance spectroscopy method Abstract This paper presents three NDT method: Magnetic Metal Memory Method, Barkhausen noise method and LFIS method. The attention has been drawn to the implicit and non-linear relationship that exists between the mechanical and electromagnetic parameters of the material and the degree of effort and degradation of the structure. Presented topic has been illustrated by examples, on the basis of which demonstrated purposefulness of taking in the account frequency characteristics of electromagnetic parameters of the material in the describtion of diagnostic symptoms of Metal Magnetic Memory method and Barkhausen noise.
Ispitivan je način priprave fotokatalitički aktivnog ZnO sloja taloženjem iz otopine. Slojevi bazičnog cinkova acetata (LBZA) uspješno su naneseni na podloge različitih morfologija, a prethodna ...hidroliza podloge pogoduje dobivanju debljih i čvršće vezanih slojeva. No postupak priprave znatno je osjetljiv na varijacije u uvjetima što čini prevlačenje većih površina zahtjevnijim. Reproducibilnost fotokatalitičke aktivnosti ZnO slojeva dobivenih žarenjem LBZA slaba je i varira do 50 %, bez jasne pravilnosti.
Preparation of photocatalytically active ZnO layer by chemical bath deposition was investigated. Layers of layered basic zinc acetate (LBZA) were successfully deposited on substrates of varying morphologies, and the substrate hydrolysis led to formation of thicker and better adhering layers. However, the process was quite sensitive to variations in conditions, which makes coating of larger surfaces more challenging. Photocatalytic activity of ZnO layers obtained from LBZA by calcining had poor reproducibility, varying up to 50 % without obvious regularity.
Bulk metallic glasses are a new emerging field of materials with many desirable and unique properties, such as high strength, good hardness, good wear resistance, and high corrosion resistance that ...can be produced in near net shape components. These amorphous materials have many diverse applications from structural applications to biomedical implants. A complete overview of bulk metallic glasses is presented: the principles of alloy design, glass formation, processing, atomistic modeling, computer simulations, mechanical properties and microstructures.
U ovom su radu prikazani rezultati ispitivanja mikrostrukture kotača dizalice, kao i procedura navarivanja koja je uporabljena za popravak. Reparaturno navarivanje se sastojalo iz dodavanja navarenog ...sloja na kotač dizalice, koji je prethodno pretrpio oštećenja uslijed habanja. Detaljna analiza kontakta između tračnice i kotača provedena je za realne uvjete opterećenja, kao i pomoću numeričke simulacije, a na osnovu mehaničkih i kemjskih karakteristika materijala uporabljenih za izradu kotača, kao i za reparaturno navarivanje. Numeričke su simulacije provedene primjenom metode konačnih elemenata. Za potrebe analize, vrijednosti kontaktnih naprezanja između kotača dizalice i tračnice određene su prema Hertz-ovoj teoriji. Svi numerički modeli su rabljeni za analizu naprezanja za slučajeve s i bez pukotine u cilju određivanja utjecaja pukotine na integritet kotača dizalice, a dobiveni rezultati su upoređeni s teorijskim vrijednostima. Također, u obzir je uzeta i simetrija kontaktnog područka između kotača i tračnice, tj. napravljeni su numerički modeli sa simetričnom i asimetričnom pozicijom kontakta.
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