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1

Investigations of the Effect of Heat Treatment and Plastic Deformation Parameters on the Formability and Microstructure of AZ91 Alloy Castings

Majerski Krzysztof, Siemionek Ewa, Szucki Michał, Surdacki Piotr

Advances in Science and Technology. Research Journal

|

2024

|

Vol. 18, no 1

1--9

EN

The article discusses the influence of heat treatment and metal forming parameters on formability and the structure of the AZ91 cast magnesium alloy. The aim of the article is to determine the optimal parameters of homogenization and plastic deformation of sand castings made of the AZ91 alloy in order to improve their properties and structure. In this study, sand castings made from the AZ91 alloy were examined. In the first stage, the castings were homogenized at: 385°C, 400°C, 415°C and 430°C with argon as a shielding gas for 24 hours and then quenched. Subsequently the upsetting tests were conducted at 380 C; 400 C; 420 C; 440 C for two deformation values: ε=0.7 and ε=1.1. After upsetting, the samples were water- and air-cooled. At this stage, a visual assessment was made and samples without cracks were subjected supersaturation at 415 C for 6 h, and artificial aging at 175 C for 24 h. Vickers microhardness tests and microstructure assessment were carried out, at individual stages of testing. Based on the results obtained from the upsetting, structure and hardness tests, the most favorable homogenisation and plastic deformation conditions were determined for AZ91 alloy sand castings. The best results are achieved by homogenizing sand castings at 415 °C for 24 h. Among the tested parameters for conducting metal forming processing in the range of 380-440 °C and deformation values: ε=0.7 and ε=1.1, forging of sand-cast AZ91 magnesium alloy at 420 °C and deformation of ε=0.7 with water cooling seems to be the most favourable. The final heat treatment applied after the deformation process consists of supersaturation at 415 °C for 6 hours water quenching as artificial aging at 175 °C for 24. This combination of heat and plastic treatment parameters of castings allows for improvement of the structure and properties of sand castings made of the AZ91 alloy.

2

Ductility and formability of Al-Mn ultrafine-grained plates processed by incremental equal channel angular pressing

Ciemiorek Marta, Goliński Jacek, Majchrowicz Kamil, Lewandowska Małgorzata

Archives of Civil and Mechanical Engineering

|

2022

|

Vol. 22, no. 4

art. no. e169, 2022

EN

The article discusses the ductility and formability of ultrafine-grained 3003 aluminum alloy plates processed using incremental equal channel angular pressing. The influence of temperature and strain rate is evaluated by means of tensile tests and cupping tests under various conditions. It is reported that tensile elongation increases two-fold at elevated temperature, without excessive grain growth. With the right selection of processing conditions, the formability of the plate, expressed as cup height deformed in a cupping test, can be enhanced—as much as 62% compared with room temperature when the processing takes place at 150 °C. The improvement in ductility was attributed to a reduced apparent activation volume due to grain refinement, which translated into improved strain rate sensitivity.

3

Fracture limit analysis of DP590 steel using single point incremental forming: experimental approach, theoretical modeling and microstructural evolution

Pandre Sandeep, Morchhale Ayush, Mahalle Gauri, Kotkunde Nitin, Suresh Kurra, Singh Swadesh Kumar

Archives of Civil and Mechanical Engineering

|

2021

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Vol. 21, no. 3

138--157

EN

The single point incremental forming (SPIF) process is gaining special attention in the aerospace, biomedical and manufacturing industries for making intricate asymmetric components. In the present study, SPIF process has been performed for forming varied wall angle conical and pyramidal frustums using DP590 steel. Initially, the conventional stretch forming process has been performed for finding the fracture forming limit diagram (FFLD). Further, it has been validated with the limiting strains found using SPIF process. The conical and pyramidal frustums deformed near to the plane strain and biaxial region, respectively. The theoretical FFLD has been predicted using seven different ductile damage models. The effect of sheet anisotropy while predicting the fracture strains has been included using Hill 1948 and Barlat 1989 yielding functions. Among the used damage models, the Bao-Wierzbicki (BW) model along with Barlat 1989 yield criterion displayed the least error of 2.92% while predicting the fracture locus. The stress triaxiality in the different forming region has been thoroughly investigated and it has been found that the higher triaxiality value reveals high rate of accumulated damage which lead to early failure of the material in the respective region. The stress triaxiality and effective fracture strains have also been found to be significantly affected by the anisotropy. The micro-textural studies have also been performed and it has been found that the increase in local misorientations and shift in the textural components from γ-fiber to ε-fiber in the corner region of the frustums worked towards limiting the formability of material and ultimately leading towards the fracture of frustums.

4

Delamination analysis in single-point incremental forming of steel/steel bi-layer sheet metal

Hassan M., Hussain G., Ilyas M., Ali A.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 2

124--137

EN

Layered metallic materials (LMMs) offer superior properties in comparison to their counterpart monolithic sheets. Single-point incremental forming (SPIF) has emerged as an economical solution to produce LMM parts. However, delamination can limit the formability of such parts. In this study, the delamination analysis during SPIF of layered sheets was performed. Steel/steel bi-layer sheets were fabricated by roll bonding. These sheets were produced at thickness reduction ratios of 47%, 58% and 70%. The bond strength and fracture toughness in mode I and mode II were determined by T-peel and tensile shear tests, respectively. When the thickness reduction ratio was increased from 47 to 70%, an increase in bond strength was observed with 572% increase in mode I and 15.6% in mode II, respectively. On the other hand, with the same percent increase in thickness reduction, the critical strain energy release showed an increase of 3992% in mode I and 20% decrease in mode II. Surface-based cohesive zone model was used to define the interface between layers during numerical simulation of SPIF for delamination analysis. To validate the numerical results, SPIF of given bi-layer sheet was performed experimentally and a good agreement between the numerical and experimental results was observed.

5

Strefowa obróbka cieplna taśm stalowych tłoczonych na gorąco

Grajcar Adam, Kozłowska Aleksandra, Morawiec Mateusz

Stal, Metale & Nowe Technologie

|

2019

|

nr 3-4

14--21

PL

Rosnące zapotrzebowanie przemysłu motoryzacyjnego na elementy charakteryzujące się wysoką wytrzymałością oraz skomplikowanym kształtem doprowadziło do opracowania nowoczesnych technik kształtowania taśm na gorąco. Do tej grupy metod zaliczany jest proces strefowej obróbki cieplnej, który jest realizowany podczas tłoczenia. Pozwala on na uzyskanie elementów o skomplikowanym kształcie, charakteryzujących się strefowo zróżnicowanymi własnościami mechanicznymi.

EN

The growing demand of the automotive industry for elements characterized by high strength and complicated shape has led to the development of new techniques of steel sheets forming. This group of methods includes the tailored heat treatment process, which is carried out during stamping. It allows obtaining elements characterized by the complicated shape and tailored mechanical properties. The special dies used in the hot forming process and controlled cooling to obtain more favorable mechanical properties compared to cold-formed elements. The tailored hot stamping enables to reduce the thickness of elements responsible for the passenger passive safety leading to the reduction of vehicle total weight.

6

Research of the dual phase steel DP450 properties from the forming aspects

Bilik Jozef, Tittel Viktor, Sobota Robert, Suba Roland

Hutnik, Wiadomości Hutnicze

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2019

|

Vol. 86, nr 1

14--17

EN

The paper is focused on study of plasticity and formability of dual phase steel DP 450, which is used in automotive industry. The paper shows results from tensile test for plasticity determination and also results of technological tests for complex evaluation of formability. These consisted from Erichsen cup test, Fukui test and Schmidt test. The paper shows also results of microhardness measurement.

PL

Artykuł koncentruje się na badaniu plastyczności i odkształcalności stali dwufazowej DP 450, która jest stosowana w przemyśle motoryzacyjnym. W pracy przedstawiono wyniki prób rozciągania dla określenia plastyczności, a także wyniki testów technologicznych dla kompleksowej oceny odkształcalności. Składały się one z testu pucharowego Erichsena, testu Fukui i testu Schmidta. W pracy przedstawiono również wyniki pomiaru mikrotwardości.

7

Single point incremental forming of Cu-Al composite sheets: A comprehensive study on deformation behaviors

Liu Zhaobing, Li Guohao

Archives of Civil and Mechanical Engineering

|

2019

|

Vol. 19, no. 2

484--502

EN

Compared with monolithic metal sheet, Single Point Incremental Forming (SPIF) of bimetal composite sheet has attracted increasing attention, as it takes advantages of materials with different superior properties, such as high strength, low density, and good corrosion resistance. However, deformation behaviors of bimetal composite sheet in SPIF may differ from the single-layer sheet, which depends on the layer arrangements and mechanical properties of each layer. In this regard, a comprehensive study was conducted to investigate the deformation behaviors of roll-bonded Cu-Al composite sheets in SPIF through predictive modeling, including analytical, empirical as well as numerical approaches, and extensive experimental work taking into consideration effects of key process parameters. It was demonstrated that overall, the formability, surface roughness, thickness variation and forming force in different layer arrangements, in terms of various process parameters, follow the similar trends to single-layer sheets. However, it was further revealed that deformation mode of layer-up sheet tends to a compression state and that of layer-down sheet tends to a stretching state. This leads to higher formability and larger forming force in Al/Cu layer arrangement compared to Cu/Al layer arrangement, as the exterior thinner but stronger Cu layer could endure more stretching deformation.

8

Prediction of average surface roughness and formability in single point incremental forming using artificial neural network

Mulay Amrut, Ben B. Satish, Ismail Syed, Kocanda Andrzej

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 4

1135--1149

EN

Single point incremental forming (SPIF) is a flexible, innovative, and cheap process for rapidmanufacturing of complex sheet metal parts. It is a crucial task for engineers to predict aprocess when many independent parameters are affecting simultaneously its performance.An artificial neural network (ANN) based prediction model was developed to evaluateaverage surface roughness (Ra) and maximum forming angle (Ømax) while SPIF forming ofAA5052-H32 material. A feedforward backpropagation network with Levenberg–Marquardtalgorithm was employed to build ANN model. The ANNs (4-n-1, 4-n-2) were generated byintroducing different combinations of transfer functions and a number of neurons. Theconfirmation runs were performed to verify the agreement between the ANN predicted andthe experimental results. The developed ANN model (4-n-1) was capable of predicting theprocess response with an excellent accuracy and resulted in overall R-value, MSE, and MAPEof 0.99807, 0.0209, and 5.96% for Ra0.99913, 0.0281, and 0.003 for Ømax. The optimum 4-n-2model was built with overall R-value, MSE of 0.99999 and 0.057194, respectively. Hence, itwas found that the engineering efforts may be reduced in the SPIF process with successfulANN model implementation.

9

Strefowa obróbka cieplna taśm stalowych tłoczonych na gorąco

Grajcar A., Kozłowska A., Morawiec M.

Stal, Metale & Nowe Technologie

|

2018

|

nr 11-12

58--62

PL

Rosnące zapotrzebowanie przemysłu motoryzacyjnego na elementy charakteryzujące się wysoką wytrzymałością oraz skomplikowanym kształtem doprowadziło do opracowania nowoczesnych technik kształtowania taśm na gorąco. Do tej grupy metod zaliczany jest proces strefowej obróbki cieplnej, który jest realizowany podczas tłoczenia. Pozwala on na uzyskanie elementów o skomplikowanym kształcie, charakteryzujących się strefowo zróżnicowanymi własnościami mechanicznymi. Zastosowanie specjalnych matryc do kształtowania na gorąco oraz kontrolowanego chłodzenia pozwala na uzyskanie bardziej korzystnych własności mechanicznych w porównaniu do elementów kształtowanych na zimno. Zastosowanie tej technologii pozwala na redukcję grubości ścianek elementów odpowiadających za bezpieczeństwo bierne pasażerów, prowadząc jednocześnie do redukcji masy całkowitej pojazdu.

EN

The growing demand of the automotive industry for elements characterised by high strength and complicated shape has led to the development of new techniques of steel sheets forming. This group of methods includes the tailored heat treatment process, which is carried out during stamping. It enables obtaining elements characterised by complicated shape and tailored mechanical properties. Special dies used in the hot forming process and controlled cooling enable obtaining more favorable mechanical properties as compared to cold-formed elements. Tailored hot stamping enables to reduce the thickness of elements responsible for passenger passive safety, which leads to the reduction of the vehicle total weight.

10

The effect of laser welding on properties of stainless steel and prediction its formability by numerical simulation

Evin E., Tomas M.

Hutnik, Wiadomości Hutnicze

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2018

|

Vol. 85, nr 10

341--343

EN

The paper deals with laser welding and its influence on the strength and plastic properties of stainless steel AISI 304 and AISI 430. The microstructure of samples laser welded by solid state fiber laser YLS-5000, made of stainless steel sheets with thickness 0,7 mm were researched. The effect of laser power and welding speed on the mechanical properties were measured by tensile test on specimens with weld in longitudinal direction. Microstructure of laser weld, heat affected zone and base material was analysed on perpendicular direction to laser weld by light microscopy. As it has been found, only the minor effect of laser welding on the mechanical properties of the stainless steel AISI 304 was found. Otherwise, the major effect of laser welding on the mechanical properties of the stainless steel AISI 430has been recorded. Applied formability of stainless steels was researched by numerical simulation of hydroforming of fuel tank.

PL

Artykuł dotyczy spawania laserowego i jego wpływu na wytrzymałość i właściwości plastyczne stali nierdzewnej AISI 304 i AISI 430. Dokonano analizy mikrostruktury próbek zgrzewanych laserem włókna stałego YLS-5000 wykonanego z blach ze stali nierdzewnej o grubości 0,7 mm. Wpływ mocy lasera i szybkości spawania na właściwości mechaniczne mierzono w próbach rozciągania na próbkach ze spoiną w kierunku wzdłużnym. Mikrostrukturę połączenia laserowego, strefy wpływu ciepła i materiału podstawowy analizowano w kierunku prostopadłym do spawania za pomocą mikroskopu świetlnego. Stwierdzono jedynie niewielki wpływ spawania laserowego na właściwości mechaniczne stali nierdzewnej AISI 304. Natomiast odnotowano znaczący wpływ spawania laserowego na właściwości mechaniczne stali AISI 430. Odkształcalność stali nierdzewnej zbadano za pomocą numerycznej symulacji hydroformowania.

11

Effects of the process parameters on the formability of the intermetallic zone in two-layer Mg/Al materials

Mola R., Mroz S., Szota P.

Archives of Civil and Mechanical Engineering

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2018

|

Vol. 18, no. 4

1401--1409

EN

This paper discusses experimental results concerning the plastic deformation of the bonding zone in a two-layer AZ31/Al material subjected to compression loads. The specimens were fabricated by diffusion bonding method. The 50 μm thick transition zone at the AZ31/Al interface contained Mg–Al intermetallic phases. The physical modelling of the deformation behaviour of the intermetallic zone was performed using a Gleeble 3800 system. The compression tests were carried out at two temperatures (300 and 400 °C), two strain rates (0.1 and 1.0 s−1) and a true strain of 0.15 applied in one or two stages. The metallographic examinations and microhardness measurements were performed to assess the influence of the selected process parameters on the forming behaviour of the intermetallic zone. The experiments revealed that the main factors affecting the formability of the intermetallic zone in the two-layer AZ31/Al material were the strain rate and the temperature. It was found that when the deformation occurred at a strain rate of 0.1 s−1 and a temperature of 400 °C, there was no loss of continuity of the intermetallic transition zone; such conditions induced its plasticization.

12

Detection of strain localization in numerical simulation of sheet metal forming

Lumelskyj D., Rojek J., Tkocz M.

Archives of Civil and Mechanical Engineering

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2018

|

Vol. 18, no. 2

490--499

EN

This paper presents an investigation on the detection of strain localization in numerical simulation of sheet metal forming. Two methods to determine the onset of localized necking have been compared. The first criterion, newly implemented in this work, is based on the analysis of the through-thickness thinning (through-thickness strain) and its first time derivative in the most strained zone. The limit strain in the second method, studied in the authors’ earlier works, is determined by the maximum of the strain acceleration. The limit strains have been determined for different specimens undergoing deformation at different strain paths covering the whole range of the strain paths typical for sheet forming processes. This has allowed to construct numerical forming limit curves (FLCs). The numerical FLCs have been compared with the experimental one. Mesh sensitivity analysis for these criteria has been performed for the selected specimens. It has been shown that the numerical FLC obtained with the new criterion predicts formability limits close to the experimental results so this method can be used as a potential alternative tool to determine formability in standard finite element simulations of sheet forming processes.

13

High strength steels and aluminium alloys in lightweight body manufacturing

Tisza M.

Archives of Materials Science and Engineering

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2017

|

Vol. 88, nr 2

68--74

EN

Purpose: of this paper: The main objectives of this paper are to give an overview about the application of various kinds of high strength steels and aluminium alloys in the automotive industry to produce lightweight car body elements to achieve significant reductions in harmful emissions to provide more environmental friendly vehicles which simultaneously fulfils the increased safety requirements, too. In these respects, both high strength automotive steels (e.g. DP, TRIP, TWIP and HPF steels), as well as high strength aluminium alloys (e.g. AA6082, AA7075, etc.) are more and more widely applied in the vehicle manufacturing. Design/methodology/approach: The contradiction between the increased strength and lower formability of these high strength metallic materials is one of the main issues in their application in the automotive industry. Therefore, in this paper primary focus will be placed on the formability properties of these materials, concerning first of all the limits of formability in various cold and hot forming conditions. To fully utilize the potentials of these materials in forming processes the numerical modelling of forming with FEM simulation is of utmost importance. Findings: Recently in the automotive industry the Hot Press Forming of high strength boron-alloyed manganese steels become an industrially established process, while the Hot Forming and Quenching (HFQ) of artificially ageing high strength aluminium alloys now become the focus of scientific research. The paper will analyse the main process parameters and gives comparisons of automotive applications. Research limitations/implications: There are still certain shortages of industrial applications, namely the limits of economic cycle times for economical mass production which needs further research activities in these fields. Practical implications: Since both the materials mentioned above and the forming processes usually applied, furthermore the available benefits are extremely important for the automotive industry these results have significant practical involvement. Originality/value: The applied research methods and the introduced new findings will show the originality of the paper.

14

Problemy oceny tłoczności materiałów metalicznych

Hyrcza-Michalska M.

Hutnik, Wiadomości Hutnicze

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2016

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Vol. 83, nr 9

398--400

PL

W artykule przedstawiono problemy oceny tłoczności materiałów metalicznych, których odkształcalność jest ograniczona. Zdefiniowano pojęcie trudno odkształcalnych wsadów do tłoczenia dzięki zestawieniu i usystematyzowaniu przyczyn ograniczających tłoczność. Zaproponowano wytyczne postępowania przy ocenie tłoczności dla tego typu trudno odkształcalnych wsadów. Stosowana metodyka badawcza opiera się o wykorzystanie metod fizycznego i numerycznego modelowania proceu tłoczenia. W badaniach zastosowano systemy automatycznego analizatora odkształceń Auto Grid, a do modelowania numerycznego oprogramowanie ETA/Dynaform. Praca stanowi przekrojową analizę szeregu badań prowadzonych przez autorkę w zespole badaczym Instytutu Technologii Metali Politechniki Śląskiej przez ostatnich kilka lat.

EN

The article presents the drawability evaluation problems of metallic materials, which deformability is limited. There is defined the concept of hard deformable charges for pressing through the statement and systematize the reasons for restricting their drawability. The guidelines for the drawability assessment for such type difficult charges are proposed. The research methodology is based on the use of methods of physical and numerical modeling of the stamping process. Presented study used the automatic strains analyzer Auto Grid and numerical modeling software ETA / Dynaform. This work is a cross-sectional analysis of a series of studies conducted by the author in the research team of the Institute of Metal Technology Silesian University of Technology in the past few years.

15

Formability of thin sheets from aluminum alloys

Spišák E., Majerníková J., Kaščák L.

Advances in Science and Technology. Research Journal

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2016

|

Vol. 10, nr 32

248--253

EN

In this contribution there have been evaluated properties of four types of sheets made from aluminium alloys. In the case of each of the examined sheets there has been checked its shearing ability via the influence of punch-die clearance change on the quality of blanking edge. Quality of blanking edge is characterized by a ratio of plastic zone height to the total thickness of the sheared material. Formability during the drawing process was measured with earring test. Results are presented by the earring coefficient (unequal height) of the cups.

16

Kształtowanie wysokowytrzymałych blach stalowych przy zastosowaniu technologii tailored blanks

Grajcar A.

Stal, Metale & Nowe Technologie

|

2015

|

nr 1-2

80--83

PL

Redukcja masy samochodu jest możliwa jedynie dzięki kompleksowemu podejściu obejmującemu zastosowanie wysokowytrzymałych blach stalowych o strukturze wielofazowej oraz nowoczesnych technik łączenia i kształtowania. Coraz większe znaczenie zyskuje technologia tłoczenia wsadów spawanych laserowo typu tailored welded blanks, a także jej odmiany: tailored welded coils i tailored welded tubes. Metody te umożliwiają optymalizację tłoczenia blach na liczne elementy karoserii, co skutkuje obniżeniem masy pojazdu, zmniejszeniem liczby odpadów, części, wzmocnień, a w konsekwencji prowadzi do obniżenia kosztów wytwarzania.

EN

The reduction of a car’s weight is only possible due to a complex approach including the application of high-strength sheet steels with multiphase microstructures and modern joining and forming techniques. More and more attention is paid on stamping of laser-welded sheets using the tailored-welded blank technology and its modifications: tailored-welded coils and tailored-welded tubes. These methods enable the optimization of sheet stamping used for numerous elements of a body-in-white. It results in the reduction of a vehicle’s weight, the reduction of a number of scrap, parts, reinforcements and finally it reduces the manufacturing costs.

17

Hartowanie tłoczonych na gorąco wysokowytrzymałych blach stalowych dla motoryzacji

Grajcar A.

Stal, Metale & Nowe Technologie

|

2015

|

nr 9-10

72--75

PL

Rozwój wysokowytrzymałych stali dla motoryzacji doprowadził do opracowania nowoczesnych technik kształtowania na zimno. Zastosowanie wysokowytrzymałych blach stalowych umożliwia redukcję grubości elementów, a nowe technologie formowania umożliwiają uzyskanie elementów o skomplikowanym kształcie. Wiąże się to jednak z dużymi oporami kształtowania na zimno i licznymi problemami, do których należy m.in. sprężynowanie. Zastosowanie technologii hartowania w prasie dla elementów tłoczonych na gorąco pozwala uniknąć wielu problemów technologicznych i obniżyć koszty poprzez zastosowanie tanich stali niestopowych.

EN

The development of high-strength steels for automotive industry has led to the elaboration of advanced cold-forming technologies. The application of high-strength steel sheets enables to reduce elements’ thickness whereas modern forming technologies make it possible to obtain elements of a complicated shape. However, it requires high cold forming forces and results in many problems, including springback. The use of press hardening for hot-stamped elements enables to avoid numerous technological problems and to reduce costs due to using inexpensive unalloyed steels.

18

The study of TRIP effect in an austenitic stainless steel AISI 304

Lischka F. T., de Oliveira C. A. S.

Journal of Achievements in Materials and Manufacturing Engineering

|

2015

|

Vol. 71, nr 1

34--38

EN

Purpose: This study investigated the deformation effect in variation of α′-martensite volume fraction and its microstructural characteristics in an austenitic stainless steel AISI 304. Design/methodology/approach: The study was fulfilled through magnetic analysis with Vibrating Sample Magnetometer (VSM) and transmission electron microscopy (TEM). Findings: The presence of austenite, ε-martensite and α′, and that the nucleation of ε-martensite occurs in stacking faults, grain boundaries and accumulated dislocations in grain boundaries. Already α′-martensite nucleates in stacking faults, twinning edges, deformation bands and mechanical twinning. In addition, the magnetic martensite takes shape directly from the austenite. Research limitations/implications: A suggestion for future research is to increase the number of samples for deformations larger than 0.30 equivalent strain, due to the significative percentage of α′-martensite from this strain. Practical implications: A crescent parabolic behavior in relation between percentage of α′-martensite and equivalent deformation was observed by VSM. The increase of equivalent deformation increases the austenite transformation in α′-martensite. Originality/value: The behavior in relation between percentage of α′-martensite and equivalent deformation, and the study of α′-martensite nucleation.

19

Possibilities of Application Methods Drece in Forming of Non-Ferrous Metals

Rusz S., Kłyszewski A., Salajka M., Hilser O., Cizek L., Klos M.

Archives of Metallurgy and Materials

|

2015

|

Vol. 60, iss. 4

3011--3016

EN

Device “DRECE - Dual Rolls Equal Channel Extrusion” is used for production of metallic materials with very fine grain size (UFG). During the actual forming process the principle of severe plastic deformation is used. Metallic strip with dimensions 57×2×1000 mm is inserted into the device. During the forming process the main cylinder in synergy with the pressure roller extrude the material through the forming tool without any change of cross section of the strip. In this way a significant refinement of grain is achieved by severe plastic deformation. This method is used for various types of metallic materials, non-ferrous metals and their alloys. The DRECE device is also being verified from the viewpoint of achievement of a UFG structure in a blank of circular cross-section (wire) with diameter of ϕ 8 mm × 1000 mm.

PL

Urządzenie „DRECE - Dual Rolls Equal Channel Extrusion” znajduje swoje zastosowanie do wytwarzania metali o strukturze ultradrobnoziarnistej (UFG). W trakcie procesu wytwarzania stosuje się metodę wielokrotnej deformacji. W urządzeniu założona jest metalowa taśma o wymiarach 57×2×1000 mm. Podczas procesu formowania, główny cylinder we współdziałaniu z dociskowym wałkiem wytłaczającym odkształca materiał bez zmiany wymiaru przekroju poprzecznego taśmy. W ten sposób uzyskuje się znaczne rozdrobnienie ziarna przez wielokrotne odkształcenie plastyczne. Metoda ta jest wykorzystywana do różnego rodzaju materiałów metalowych, metali nieżelaznych i ich stopów. Urządzenie DRE CE jest również testowane pod kątem osiągnięcia struktury UFG w materiale o przekroju okrągłym (drut) o średnicy ϕ8 mm i długości 1000 mm.

20

Experimental and Theoretical Determination of Forming Limit Curve

Adamus J., Dyja K., Motyka M.

Archives of Metallurgy and Materials

|

2015

|

Vol. 60, iss. 3A

1881--1885

EN

The paper presents a method for determining forming limit curves based on a combination of experiments with finite element analysis. In the experiment a set of 6 samples with different geometries underwent plastic deformation in stretch forming till the appearance of fracture. The heights of the stamped parts at fracture moment were measured. The sheet - metal forming process for each sample was numerically simulated using Finite Element Analysis (FEA). The values of the calculated plastic strains at the moment when the simulated cup reaches the height of the real cup at fracture initiation were marked on the FLC. FLCs for stainless steel sheets: ASM 5504, 5596 and 5599 have been determined. The resultant FLCs are then used in the numerical simulations of sheet - metal forming. A comparison between the strains in the numerically simulated drawn - parts and limit strains gives the information if the sheet - metal forming process was designed properly.

PL

Duże znaczenie procesów tłoczenia blach w przemyśle wynika z faktu, że umożliwiają one produkcję różnych elementów od drobnej galanterii metalowej po duże elementy karoserii samochodowych i poszyciowe elementy samolotów. Ze wzrostem zapotrzebowania na wyroby tłoczone rośnie znaczenie umiejętności przewidywania zachowania się blachy podczas procesu kształtowania. W tym celu wykorzystuje się krzywe odkształceń granicznych, które stanowią granicę, powyżej której następuje pękanie wytłoczek. Najczęściej, mimo wielu trudności, krzywe odkształceń granicznych wyznacza się doświadczalnie poprzez pomiar odkształcenia materiału blachy. Chociaż dzisiaj są dostępne nowoczesne, optyczne systemy pomiarowe, to wyznaczanie krzywych odkształceń granicznych dla niektórych materiałów, takich jak: wysokowytrzymałe stopy tytanu czy analizowane w pracy wysokowytrzymałe i odporne na korozję stale stosowane w przemyśle lotniczym, nadal stanowi problem. Dlatego autorzy pracy w celu wyznaczenia KOG dla blach stalowych ASM 5504, 5596 i 5599 zdecydowali się na połączenie badań eksperymentalnych z analizą elementów skończonych. W tym celu zestaw 6 wykrojek o zróżnicowanej geometrii poddano tłoczeniu za pomocą sztywnego, półkulistego stempla aż do pojawienia się pęknięcia wytłoczek. W momencie pękania rejestrowano głębokość wytłoczenia. Następnie modelowano proces kształtowania tych wytłoczek przy użyciu metody elementów skończonych. Obliczone wartości odkształceń w momencie, gdy symulowane wytłoczki osiągały głębokość wytłoczek rzeczywistych w momencie ich pękania naniesiono na wykres odkształceń granicznych w układzie maksymalnych (oś Y) i minimalnych (oś X) odkształceń głównych. Tak wyznaczone krzywe odkształceń granicznych służą ocenie przydatności blachy do procesów tłoczenia.