Wyniki wyszukiwania - BazTech

1

Prediction of forming limits and microstructural evolution during warm stretch forming of DP590 steel

Pandre Sandeep, Morchhale Ayush, Kotkunde Nitin, Singh Swadesh Kumar, Ravindran Sujith

Archives of Civil and Mechanical Engineering

|

2021

|

Vol. 21, no. 3

397--419

EN

Dual-phase (DP) steel has an excellent blend of various mechanical properties; hence it is used immensely in the automotive industries. It is challenging to form high strength DP steel into desirable complex shapes because of their limited formability at room temperature conditions. One of the proven alternatives is warm/hot forming. In-detail investigation of forming limits over DP590 steel has been carried out in present work. Firstly, various constitutive models and yield criteria have been formulated for DP steel at different temperatures and strain rates. The modified Arrhenius (m-A) constitutive model and Barlat 1989 yielding function displayed the best prediction of flow stress and anisotropic yielding behavior, respectively. The experimental forming limits (FLD) were evaluated at 300, 473 and 673 K temperatures using Nakazima tests. The forming limits of the material are improved by approximately 24% on increasing the temperature from 300 to 673 K. The textural analysis of the deformed surface has been done using electron back scattered diffraction (EBSD) studies, and γ fibers are found to be responsible for improvement in the formability of the material. Additionally, Marciniak and Kuczynski (MK) model was used to predict the theoretical FLD using all the possible combinations of constitutive models and yield criteria. Finally, the m-A constitutive model, along with Barlat 1989 yielding function has shown the best prediction for forming limits at all the temperatures. The finite element study has also been performed using mentioned material models for accurate prediction of dome height, surface strain and thickness distribution across the specimens.

2

Optimization of deep drawing process forming parameters for magnesium

Watiti V. B., Labeas G. N.

Computer Methods in Materials Science

|

2010

|

Vol. 10, No. 2

87-96

EN

Formability of Magnesium alloys is limited especially at room temperature due to their hexagonal close packed (HCP) structure. At room temperature (RT), the critical resolved shear stress for non basal slip systems is much greater than those for basal slips. As only basal systems may contribute to plastic deformation, magnesium alloys have limited formability at RT. However, increased formability is observed at higher temperatures ranging between 1500C and 3000C due to the activation of additional slip planes. Additionally, it has been observed that the formability is very sensitive to strain rates. In this paper experimental and Finite Element (FE) analysis are applied for the development of a methodology based on strain energy density for determination of the forming limits of magnesium alloys AZ31 and WE43. Based on the developed methodology optimal forming parameters in a deep drawing forming process, namely punch radius, temperature, profile radius and forming depth are determined.

PL

Odkształcalność stopów magnezu jest ograniczona, szczególnie w temperaturze otoczenia, ze względu na ich heksagonalną upakowaną strukturę krystalograficzną (HPC - ang. hexagonal close packed). W temperaturze otoczenia, w sieci heksagonalnej działa tylko jedna płaszczyzną poślizgu - płaszczyzna podstawy. Z uwagi na znacznie większe ścinające naprężenia krytyczne inne systemy poślizgu nie działają,. Ponieważ odkształcenie plastyczne zachodzi na skutek działania tylko jednej płaszczyzny podstawy łatwo następuje utrata stateczności materiału i dochodzi do jego pęknięcia. Powoduje to znaczne ograniczenia w przeróbce plastycznej stopów magnezu na zimno. Z drugiej strony, wzrost odkształcalności wynikający z aktywowania dodatkowych systemów poślizgu jest obserwowany w temperaturach 1500°C - 3000°C. Dodatkowo zaobserwowano, że odkształcalność badanych stopów jest wrażliwa na prędkość odkształcenia. W niniejszym artykule, metody doświadczalne i symulacje metodą elementów skończonych zastosowano do opracowania metodyki określania zakresów odkształcalności stopów magnezu AZ31 i WE43. Zaproponowana metodyka opiera się na teorii gęstości energii odkształcenia. Na podstawie opracowanej metodyki wyznaczono optymalne parametry procesu głębokiego tłoczenia, takie jak promień stempla, temperatura, promil profilu i głębokość formowania.

3

On the forming and fracture limits of sheet metals

Korhonen A. S., Manninen T., Yoon J. W.

Computer Methods in Materials Science

|

2009

|

Vol. 9, No. 1

143-147

EN

It became apparent in the late 1980 that all manufacturing processes in the future would be first simulated before industrial implementation. Sheet metal forming was one of the most important applications where this technology could be applied. One of the issues was to represent the plastic behavior of sheet materials. For accurate numerical simulations information is needed on the initial yielding, subsequent work-hardening and final localization of plastic flow and/or fracture. The forming limits have been studied since the mid-1940s, when Gensamer and Lankford and coworkers carried out their tests with steel and aluminum. In this work we discuss the forming and fracture limits of low carbon steel, stainless steel and aluminum. Experimental results on stretch forming, deep drawing and tensile testing will be presented. Hydraulic bulge testing is employed in the stretch forming experiments. Marciniak-type in-plane tests are carried out to study the limit strains in deep drawing. Laser marked grids are used to measure the surface strains and scanning electron microscopy is employed to measure the thickness strains and to study the fracture surfaces.

PL

Badaniom poddane zostały ograniczenia możliwości odkształcania i pojawianie się pęknięć w blachach ze stali nierdzewnej i aluminium. Test hydraulicznego wybrzuszenia został przeprowadzony w procesie formowania z rozciąganiem. Test typu Marciniaka oraz testy rozciągania zostały przeprowadzone w celu zbadania granicznej odkształcalności. Siatka naniesiona metodą sitodruku i laserem została użyta do pomiaru odkształceń powierzchni próbki. Ponadto, użyto mikroskopu skaningowego do pomiaru odkształceń na grubości i badania powierzchni pęknięć.