Tailor-welded blanks (TWB) of materials with different stress-strain properties are characterised by uneven plastic flow in deep drawing process which results in unequal transfer of technology (blankholder) forces on the functional parts of the forming tool. These phenomena occur most significantly during drawing of blanks with a combination of sheet parts with a different formability or different thicknesses. Observing the behaviour of these blanks in the forming process is relevant to the final functional and appearance quality of the drawn parts. The combination of materials which is widely used for the production of bodyworks structure was chosen for this analysis. The experiments were performed on a laboratory instrument with an elastic blankholder for the deep drawing of a rectangular-footprint part. TWB formability was investigated in terms of the size and layout blankholder forces after setting a constant blankholder pressure before the drawing process. Zespawane metodą spawania na styk półfabrykaty(TWB) z materiałów o różnych właściwościach naprężeniowo-odkształcających charakteryzują się nierównym płynięciem plastycznym w procesie głębokiego tłoczenia, które skutkuje nierównym przeniesieniem technologicznym sił dociskacza na funkcjonalne elementy narzędzia tłoczącego. Zjawiska takie występują głównie podczas tłoczenia półfabrykatów zawierających kombinację arkuszy o różnej odkształcalności oraz o różnej grubości. Obserwacja zachowania tych półfabrykatów w procesie kształtowania jest istotna dla końcowego funkcjonowania i jakości wyglądu zewnętrznego tłoczonych elementów. Kombinacja różnych materiałów powszechnie używanych w produkcji struktur nadwozi została wybrana do analizy. Eksperymenty przeprowadzono w na urządzeniach laboratoryjnych z użyciem elastycznego dociskacza do głębokiego tłoczenia z prostokątną częścią odciskającą. Odkształcalność materiałów typu TWB została zbadana pod względem rozmiaru i rozkładu sił dociskacza po u[...]

  Uneven plastic flow and weld line instability in deep drawing process characterises sheet metal forming of tailor-welded blanks (TWBs) of materials with different stress-strain properties. Such behaviour is visible mainly during drawing of TWB with a combination of sheet parts with different thicknesses or formability. Researching these phenomena in the forming process is important in relation to the final functional and visual properties of the drawn parts. In our analysis, the combination of materials widely used in automotive industry for the production of bodyworks structure was chosen. The testing was prepared using a laboratory instrument with an elastic blankholder for the deep drawing of a rectangular-footprint part. TWB formability was researched in relation to the shape and earing of the part and its dependence on the orientation of weld line to part footprint and its positioning after drawing. Nierówne płynięcie plastyczne i niestabilna linia wtopienia w procesie głębokiego tłoczenia charakteryzuje kształtowanie materiałów zespawanych na styk półfabrykatów (TWB) mających różne właściwości naprężeniowo-odkształcające. Takie zachowanie materiału jest głównie obserwowane w przypadku materiałów TWB kiedy łączone są powierzchnie o różnej grubości i odkształcalności. Badanie tych zjawisk w procesie formowania jest ważne w odniesieniu do końcowych właściwości funkcjonalnych i wizualnych tłoczonych części. W niniejszej analizie wybrano typową dla budowy nadwozia kombinację materiałów szeroko stosowanych w przemyśle samochodowym. Badania zostały przygotowane z użyciem przyrządów laboratoryjnych z wykorzystaniem elastycznego dociskacza do głębokiego tłoczenia z częścią odciskową w kształcie prostokąta. Odkształcalność materiałów TWB została zbadana pod względem kształtu i tworzenia się uch na obrzeżu wytłoczki danej części, a także po[...]

  Introduction. Reduction of both vehicle weight and fuel consumption has been a constant demand in automotive in dustry without compromising other attributes such as safety, performance, recyclability and manufacturing costs. A prom ising opportunity to meet these requirements is using of tai lor welded blanks (TWBs) consisting of high strength steels. A car body manufactured using TWBs and high strength steels can achieve a 25% weight reduction. TWBs are blanks where multiple sheets of material are welded together prior to the forming process. The differences in the material within a TWB can be in the thickness, grade or coating of the mate rial [1-3]. Important advantage of using TWBs is to reduce the amount of scrap due to the odd shapes of the blanks. Smaller pieces of metals can be nested easily for better mate rial utilization. Another main advantage of using TWBs is specific characteristics at distinct parts of the TWB to reduce the material weight and cost. Certain sections of the TWB can be made from a thicker or high strength material to in crease stiffness while having a thinner material at other sec tions. The sections of the TWB can be made of coated steel to increase the resistance to corrosion while having bare steel at other sections too [3-5]. An example of using TWB consisting of sheets with different thicknesses is the reinforcement of longitudinal beam in car body structure. The reinforcement is produced by deep drawing process and three steps of its manufactur ing are documented in fig. 1 to 3. The TWB for symmetric deep drawing is in fig. 1. It consists of sheets with different thicknesses and different materials which were laser weld ed before deep drawing process. Two drawn part are deep drawn in one tool. Both right and left deep drawn part of reinforcements are in fig. 2. The position of right reinforce[...]

  Introduction. Tailor welded blanks (TWBs) were deve􀀐 loped mainly for automotive applications. They are semi-fi􀀐 nished parts that usually consist of materials with different stress strain properties, but they can be made of materials with different thicknesses or coatings too [1-3]. Several grades of steel such as deep drawing steels, interstitial free steels, high strength low alloy steels, bake hardening steels, dual phase steels, complex phase steels, TRIP steels, mar􀀐 tensitic steels and TWIP steels are used in TWBs design. Using of various steels in TWBs design enables to achieve the different stress strain characteristic in certain sections of the drawn parts [4, 5]. The individual steel sheets used in TWBs are joined by welding with concentrated energy sources such as laser or plasma welding. Minimal deformation of TWBs because of small heat affected zones together with high welding speed and large flexibility are the main advantages of these we􀀐 lding methods. The ability of welded joints to support of load are controlled by some basic mechanical testing me􀀐 thods such as tensile test, Erichsen deep drawing test, three point bending test, etc. [6-8]. Apart from the weldability, the formability is the most important property of TWBs. The formability is influenced by different stress and strain properties of particular sheets from the view of planar and normal anisotropy. The signi􀀐 ficant differences of these properties give higher require􀀐 ment on formability evaluation and measuring of stress strain parameters. These are used for boundary conditions at simulation of drawing processes and they are defined by proof strength, tensile strength, ductility, planar anisotropy coefficient, true stress versus true strain curve, deformation strengthening coefficient and forming limit diagram [7-9]. Experiment. The aim of the work was to compare si􀀐 mula[...]

  In the study tailor welded blanks were prepared by solid laser welding. They consisted of same dual-phase steel HCT600X of equal thick- ness but different rolling directions and planar anisotropy. The influence of planar anisotropy on formability of tailor welded blanks were investigated. Major part of the research was made virtually by FEM using appropriate material model with accurate description of planar anisotropy. The aim was to observe plastic material flow and ear formation at the edge of the deep drawn part. These results were verified by real experiments. W artykule przedstawiono wyniki badań, w których zastosowano wykrojkę łączoną typu "tailored blank", gdzie połączenie uzyskano poprzez spawanie laserowe. Wykrojka składa się blach o tej samej grubości, wykonanych ze stali dwufazowej w gatunku HCT600X, ale o różnej względnej orientacji kierunku walcowania oraz różnej anizotropii płaskiej. Przebadano wpływ anizotropii płaskiej na zdolność odkształceń (na przykładzie wytłaczania) tak przygotowanej wykrojki. Badania bazują na symulacji numerycznej MES, gdzie zastosowano model materiałowy uwzględniający dokładny opis anizotropii płaskiej blachy. Celem było zaobserwowanie plastycznego płynięcia materiału oraz kształtowanie się tzw. "uch" na krawędzi wytłoczki prostokątnej. Wyniki symulacji zostały zweryfikowane doświadczalnie. Key word: Tailor-welded blank, FEM, dual-phase steel, anisotropy Słowa kluczowe: wykrojka łączona spawaniem, wytłaczanie, MES, stal dwufazowa, anizotropia.1. Introduction. High strength sheet steels have been developed predominantly for automotive applications. Various new grades of steels have been developed which show excellent formability and are able to meet the most automotive requirements. The most popular grades of automotive steels are dual-phase grade. Weldability and formability belong to the most important properties of automotive steels, because of increasing use of tailor-welded blanks (TWB). They usua[...]

  Introduction. Tailor welded blanks (TWBs) have been found the most application in automotive industry. The sheets used in TWBs are often made of materials with different stress-strain characteristics [1]. Many material combinations have been used in design of TWBs such as conventional deep-drawing steels of grades DC01 to DC05 with conventional high strength steels IF-HS, HSLA, BH and IS or ultra-high strength steels DP, CP, TRIP, MART and TWIP [2]. The sheets have been joined by concentrated power source by laser or plasma welding process. The main function of welded joints is transfer of forming forces dur ing drawing and bending processes [3]. This ability can be verified by the static tensile test according to ISO 6892-1, by Erichsen cupping test according to ISO 20482:2014-05 and by three-point bending [4]. Except experimental methods, the simulation software for example AutoForm, Pam-Stamp and Dynaform have been used at the evaluation of TWBs forming with different stress-strain characteristics. The softwares are equipped with stress-strain characteristics of majority materials used in TWBs design and they determine the border conditions for forming process simulations. It´s very important to ob tain topical parameters of technological properties, to edit them manually into software and to get more accurate re sults comparable with real state [5, 6]. Among them belong proof strength, tensile strength, percentage elongation after fracture and percentage reduction of area (ISO 6892-1), coefficients of normal and planar anisotropy (ISO 10113), work hardening coefficient (ISO 10275), flow curve and forming limit diagram. The considerable differences betwe en measured material parameters and parameters declared by t[...]

  Introduction. The rods, profiles and tubes bending is specific technology which is characteristics by complicated combination of stress states [1, 2] characterised by a spatial 3D bending in formed material [3, 4]. An extremely small bending radius of tubes results in the danger of formed material overstrength in outer bending location [5], a large wall thickness increasing in inner bending location and undesirable ovality creating [6]. These all facts, besides required geometry, are affected also by suitable construction and material of forming tool. The closed area of heat exchanger cramped because it hasn’t been assumed any another change. It was necessary to increase size of heat transfer area by means of exchanger tube bodies number increasing because of efficiency improving. This enlarging has been possible to obtain by bending radius minimization of anguineform tube exchanger system. Required tube bending radius has been possible to gain by choice of suitable tube material and forming tool adjustment by a bending rail change. These changes affected to a coefficient friction during bending process. Problem characteristics. The heat exchanger is compound of casing and anguineformly arranged tube system according to Fig. 1. For the area enlarging of heat-delivery surface water heater, the anguine seamless tubes with changed bending radius have been designed in such a way that it has been possible to give more pieces of anguine tubes into the original heater area. The bending radius up to the neutral axis of anguine tubes has been reduced to R = 40 mm. The designed heavy-wall seamless tubes in sizes 38 × 5 mm made of material 1.0345 (P235GH) with chemical composition according to table 1. It is a carbon plain heat resistant steel suitable for pressure vessels and Fig. 1. The scheme of re-designed heat exchanger internal arrangement Rys. 1. Schemat budowy wewnętrznych układów przeprojektowanego wymiennika ciepła T[...]

  Introduction. The forming tools construction and technological processes design are based many times on the empirical evidences. However, the numerical simulations progress allows in high accurary rate the objective determination of forming, stresses and strains distribution and wall thickness of drawn part during single stages of techmological processes and number of attempts decreasing at production technology design [1, 2]. The numerical simulation and experimental adjusting of square box deep drawing provide many information about strain characteristics of process. The forming of two flat sides and their transition on the corner of an axially symmetric drawn cup is possible to analyse as three independet remoulded areas [3, 4]. The drawn cup corner with intensive thickness increasing of material is a problem area especially during deep drawing of galvanized highstrength steels [5]. This effect influences on friction rate under a blankholder and on drawing edge, surface quality and galvanized layer compactibility of drawn cup in exposed sites. The analyzed model example is possible to generalize for deep drawing of ground complex shaped drawn cups. The aim was to determine through simulation and experiments of square box deep drawing from sheet metals of highstrength steel TRIP: - appropriate drawing gap geometry of experimental tool, - stress-strain material characteristics of blank used for experiments for simulation enter data optimization, - non-st[...]