Određivanje naprezanja tečenja hidrauličnim pokusom dubokog izvlačenja

In sheet metal forming operations the mechanical properties of the sheet metal (stress-strain curve, flow stress) greatly influence metal flow and product quality. Accurate determination of the stress-strain relationship is important in process simulation by finite element method. In this paper the sheet thickness gradation in different points of the hemisphere formed in the bulge test is analysed, both theoretically and experimentally. A precise determination of sheet thickness at the pole is very important in the precise determination of stress-strain relationship. The use of the hydraulic bulge test for estimation of flow stress under biaxial stress-strain state is discussed.U oblikovanju trake mehanička svojstva trake (σ–ε dijagram, naprezanje tečenjem) značajno utječu na tečenje i kakvoću proizvoda. Točno određivanje odnosa naprezanje-istezanje je važno u procesu simulacije metodom konačnih elemenata. Na pokusu dobivenim dubokim izvlačenjem analiziralo se i teoretski i eksperimentalno, po debljini trake i polukugli. Precizno određivanje po debljini trake je važno za odnos naprezanje-istezanje. Raspravljeno je rabljenje hidrauličkog pokusa dubokog izvlačenja za procjenu naprezanja tečenja za dvoosno stanje naprezanje-istezanje

Change of ears creation of AHSS steels after heat treatment of zinc coating

The article deals with the normal anisotropy, the earring evaluation of deep-drawing steels DC06, micro-alloyed steel H220 and steel with transformation induced plasticity TRIP RAK 40/70 and deals with the influence of annealing temperature to ears creation of H220 steel and TRIP RAK 40/70 steel. The evaluation of normal anisotropy has been made by tensile test on TIRA test 2300 according standards STN EN 10002-1+AC1 and STN 42 0321. The evaluation of earring degree has been carried out on the cups, which have been drawn on a hydraulic press Fritz Muller 100

Assessment of properties thermal sprayed coatings realised using cermet blend powder

The article deals with the assessment of selected properties of plasma sprayed coatings based on ZrSiO₄ doped with different volume fractions of metal dopant (Ni). Mixed powders are cermet blends. Aim of the work consists of verificating the possibility to replace the application of Ni interlayer by adding Ni directly to the ceramic powder and apply them together in a single technological operation. The coatings were studied from point of view of their structure, porosity, adhesion of the coatings in relation to the volume of dopant added and wear resistance. The best properties reached composite coating doped with 12 % Ni

The Influence of Tandem Mill Reduction on Double Reduced (DR) Tinplates Anisotropy

In this paper, influence of tandem mill reduction on double reduced tinplates anisotropy is presented. In order to achieve favourable anisotropy properties (deformation texture) of tinplates for deep drawing operations, optimal percentage reduction on tandem mill is important. The experiment was carried out in laboratory conditions and three sorts of materials (T 57, T 61 and T 65) were used. The anisotropy was classified by earing test determining the ear height of tinplate after deep drawing by measuring the height of any ear. Percentage reduction on tandem mill and final earing relationships of tinplates are researched

Usporedba oblikovno - graničnog dijagrama (FLD) modela izvlačenja čeličnih limova

U ovom radu je provedeno usporedno ispitivanje tri matematička modela (model Marciniak - Kuczynskog, Hill-Swiftov i Sing-Rao) kao i empirijskih modela kojeg je predložila Sjeverno američka grupa za istraživanje dubokog izvlačenja (NADDRG). Granični kriterij (1993.) koji je nedavno predložio Hill koristi se za izračun graničnih deformacija u vezi s Swiftovim uvjetom nestabilnosti difuzije pri sužavanju i korištenjem analize Marciniak - Kuczynski. Naglasak ovog istraživanja je u različitim pristupima predmnjevanja FLD. Dobiveni su eksperimentalni rezultati za različite niskougljične čelične limove za izvlačenje u kakvoći limova FeP06 G i ZStE 220P kao i refosforiziranih i mikrolegiranih čelika. Usporedbom, teorijski model je bio u dobroj podudarnosti s praksom.In this paper a comparative investigation of three mathematical models (Marciniak - Kuczynski model, Hill - Swift model and Sing - Rao model) as well as an empirical model proposed by the North American Deep Drawing Research Group (NADDRG) has been carried out. The yield criterion (1993), recently proposed by Hill, is used for the calculation of the limit strains in connection with the Swift’s instability condition for diffuse necking and with the Marciniak - Kuczynski analysis. The emphasis of this investigation is to consider these different approaches to predicting the FLD. Experimental results have been obtained for different low carbon steel sheets of drawing quality - FeP06 G and ZStE 220P as well as rephosphorised and micro-alloyed steel. It was compared, which theoretical model showing good correlation with experiment is suitable for materials mentioned above

Finite Element Calculation of Clinching with Rigid Die of Three Steel Sheets

The clinching joining of three steel sheets (DC06, DX53D, and H220PD type) was studied by utilization of the finite element method. Clinched joints were also prepared experimentally by joining the above-mentioned steels with the thickness of 0.8 mm (DC06 and DX53D) and 1.0 mm (H220PD). The experimental tool works as single stroke tool, while prepared joints have circular axisymmetric shape, and the rigid die has no flexible segments. Finite element calculations were carried out in ANSYS software under simplified-axisymmetric conditions. Metallographic sections were also prepared from experimentally developed joints to make possible to directly compare the results of simulated and experimental approach. The results of computational approach are discussed and compared to the experimental ones.Методом конечных элементов рассчитано заклепочное соединение листов из трех сталей (типа DC06, DX53D и H220PD). Клепаные соединения были получены также экспериментально посредством соединения сталей DC06 и DX53D толщиной 0,8 мм и H220PD толщиной 1,0 мм. С помощью экспериментального приспособления, которое работает как однопроходное устройство, изготовлены соединения круглой и осесимметричной формы; штамп не содержит гибких элементов (жесткий штамп). Расчеты методом конечных элементов выполнены с помощью программы ANSYS при упрощенном осесимметричном режиме. Из полученных соединений были изготовлены металлографические шлифы для сравнения результатов моделирования с экспериментом. Представленные результаты вычислений обсуждаются и сравниваются с экспериментальными данными

Analysis of Cutting Surface During Cutting of Electric Sheets

The contribution evaluates the influence of the size of the cutting gap on the quality of the cutting surface during the cutting process. Four types of electrical sheets were evaluated. Examined sheet types have the nominal thickness of 0.65 and 0.5 mm. Sheets differ in mechanical properties (yield strength, ultimate tensile strength, and elongation). For the impact analysis, four values of the 0.02, 0.05, 0.1, and 0.2 mm cutting gap were used.Анализируется влияние величины зазора резки на качество поверхности реза при обработке резанием. Исследовались четыре типа электротехнических листов с номинальной толщиной 0,65 и 0,5 мм и различными механическими характеристиками (предел текучести, предел прочности при растяжении и относительное удлинение). Для анализа влияния указанных факторов использовались четыре значения зазора резки: 0,02; 0,05; 0,1 и 0,2 мм

FEM Analysis of Clinching Tool Load in a Joint of Dual-Phase Steels

The clinching tool with a die of 5 mm diameter with a specially formed gap and a punch of 3.6 mm diameter were used for mechanical joining of dual-phase steel sheets DP600 with the pressing force of 30 kN. The punch and die were deposited by PVD coating of CrN type with LARC technology. The coating state of each 50th manufactured join was evaluated by SEM. Cracks in the area of punch’s radius were detected. The finite element method was applied for the assessment of punch load in the joining process

Crystallographic structure of ultrathin Fe films on Cu(100)

We report bcc-like crystal structures in 2-4 ML Fe films grown on fcc Cu(100) using scanning tunneling microscopy. The local bcc structure provides a straightforward explanation for their frequently reported outstanding magnetic properties, i.e., ferromagnetic ordering in all layers with a Curie temperature above 300 K. The non-pseudomorphic structure, which becomes pseudomorphic above 4 ML film thickness is unexpected in terms of conventional rules of thin film growth and stresses the importance of finite thickness effects in ferromagnetic ultrathin films.Comment: 4 pages, 3 figures, RevTeX/LaTeX2.0

Magnetic phenomena in 5d transition metal nanowires

We have carried out fully relativistic full-potential, spin-polarized, all-electron density-functional calculations for straight, monatomic nanowires of the 5d transition and noble metals Os, Ir, Pt and Au. We find that, of these metal nanowires, Os and Pt have mean-field magnetic moments for values of the bond length at equilibrium. In the case of Au and Ir, the wires need to be slightly stretched in order to spin polarize. An analysis of the band structures of the wires indicate that the superparamagnetic state that our calculations suggest will affect the conductance through the wires -- though not by a large amount -- at least in the absence of magnetic domain walls. It should thus lead to a characteristic temperature- and field dependent conductance, and may also cause a significant spin polarization of the transmitted current.Comment: 7 pages, 5 figure