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

Influence of plastic deformation inhomogeneity on corrosion resistance of TIN plates

Thin steel sheets are used in the production of food packaging, especially for long-term storage. Reducing the thickness of steel sheets and increasing the speed of the drawing process in the manufacture of packaging often decrements its plastic deformation stability. These changes bring about the need to use evaluation methods able to determine mechanical and plastic properties of steel sheets quickly and at a low cost. Two types of tin-plated steel sheets were used for experimental research into the influence of plastic deformation on their corrosion resistance. The paper compares the results of the uniaxial tension test and the biaxial tension test of tin-plated sheet properties

Operation of Multiple Reservoir Systems: A Case Study of the Upper Vistula System (An Introduction)

Water resource systems have been an important part of resources and environment related research at IIASA since its inception. As demands for water increase relative to supply, the intensity and efficiency of water resources management must be developed further. This in turn requires an increase in the degree of detail and sophistication of the analysis, including economic, social and environmental evaluation of water resources development alternatives aided by application of mathematical modeling techniques, to generate inputs for planning, design, and operational decisions. During the year of 1978 it was decided that parallel to the continuation of demand studies, an attempt would be made to integrate the results of our studies on water demands with water supply considerations. This new task was named "Regional Water Management" (Task 1, Resources and Environment Area). This paper is concerned with operational decision-making in the existing multiple reservoir systems. Following a short description of the case system, three different approaches to optimization of the system's operation are presented. First, the three-step stochastic implicit approach; second, the simulation approach; and third, the approach based on the concepts of hierarchical control systems. Distinction is made between the long-term reservoir operation rules and the short-term operational decisions using the real-time forecasts of reservoir inflows and water demands. The paper is part of a collaborative study on the operation of the Upper Vistula multiple reservoir system in Poland, carried out by the Institute for Meteorology and Water Management, Warsaw, Poland and IIASA

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

Advanced Material Models for Stamping of AW 5754 Aluminum Alloy

Predictions by numerical simulations are strongly influenced by availability and reliability of input data. In the most used computational models, the material behavior during deformation is described only by static tensile test in combination with Lankford coefficients of anisotropy. However, for some specific materials like highly anisotropic aluminum alloys, such description of material behavior is insufficient and, in many cases, the calculated results are not in good agreement with the measured ones. In this paper, the implementation of advanced material model for deep-drawing process to explicit FE code and the procedure of measurement of the most important input material data for calculations on the aluminum alloy AW 5754 are discussed. Results of the numerical simulation are compared with the experimental ones and exhibit a close correlation

An indoor test methodology for solar-powered wireless sensor networks

Repeatable and accurate tests are important when designing hardware and algorithms for solar-powered wireless sensor networks (WSNs). Since no two days are exactly alike with regard to energy harvesting, tests must be carried out indoors. Solar simulators are traditionally used in replicating the effects of sunlight indoors - however, solar simulators are expensive, have lighting elements that have short lifetimes, and are usually not designed to carry out the types of tests that hardware and algorithm designers require. As a result, hardware and algorithm designers use tests that are inaccurate and not repeatable (both for others and also for the designers themselves). In this article we propose an indoor test methodology which does not rely on solar simulators. The test methodology has its basis in astronomy and photovoltaic (PV) cell design. We present a generic design for a test apparatus which can be used in carrying out the test methodology. We also present a specific design which we use in implementing an actual test apparatus. We test the efficacy of our test apparatus and, to demonstrate the usefulness of the test methodology, perform experiments akin to those required in projects involving solar-powered WSNs. Results of the said tests and experiments demonstrate that the test methodology is an invaluable tool for hardware and algorithm designers working with solar-powered WSNs

Forgetting in Answer Set Programming with Anonymous Cycles

FORGET (PTDC/CCI-INF/32219/2017). NOVA LINCS (UID/CEC/04516/2019).It is now widely accepted that the operation of forgetting in the context of Answer Set Programming [10, 18] is best characterized by the so-called strong persistence, a property that requires that all existing relations between the atoms not to be forgotten be preserved. However, it has been shown that strong persistence cannot always be satisfied. What happens if we must nevertheless forget? One possibility that has been explored before is to consider weaker versions of strong persistence, although not without a cost: some relations between the atoms not to be forgotten are broken in the process. A different alternative is to enhance the logical language so that all such relations can be maintained after the forgetting operation. In this paper, we borrow from the recently introduced notion of fork [1] – a conservative extension of Equilibrium Logic and its monotonic basis, the logic of Here-and-There – which has been shown to be sufficient to overcome the problems related to satisfying strong persistence. We map this notion into the language of logic programs, enhancing it with so-called anonymous cycles, and we introduce a concrete syntactical forgetting operator over this enhanced language that we show to always obey strong persistence.publishe

Experimental and Numerical Analysis of Springback Behavior of Aluminum Alloys

Presented work deals with springback behavior of two different aluminum alloys, one falling into 5th series (AW-5754 H22) with a thickness of 0.8 mm and other from 6th series (AW-6082 T6) with 1.0 mm thickness. These materials are used for their various applications and hardening process. The springback behavior was investigated by U-bending test. Bending tool was graduated jig with rollers and experiment was performed on R11 and R17 radii. The first series of specimens were oriented in a parallel direction and the other in a direction perpendicular to the rolling direction. Experimental results were measured with MATLAB measuring method and compared with finite element calculation carried out in PAM-STAMP. Influence of different yield functions was also examined.Рассматривается характеристика упругой отдачи двух различных алюминиевых сплавов: AW-5754 H22 толщиной 0,8 мм, принадлежащего к 5-й серии, и AW-6082 T6 толщиной 1,0 мм, принадлежащего к 6-й серии. Эти материалы используются для разнообразного применения, включая процесс упрочнения. Характеристика упругой отдачи исследовалась при испытаниях на U-образный изгиб. В качестве гибочного инструмента использовалось приспособление с роликами, и эксперимент проводился на радиусах R11 и R17. Одна группа образцов была ориентирована в направлении, параллельном направлению прокатки, другая в перпендикулярном. Экспериментальные результаты, полученные с использованием программного комплекса MAТLAB, сравнивались с расчетом методом конечных элементов с помощью программы PAM-STAMP. Исследовалось также влияние различных функций текучести