Klaus Drotleff

Universität Stuttgart · Institute for Metal Forming Technology

The aim of present work is to examine D-Bressan mathematical model to accurately predict the surface limit strains by the critical fast shear stress criterion of conventional AA6014 aluminium alloy sheets, after loading with non-linear strain paths at room temperature. Two kinds of limit strain curves can be plotted in the Map of Principal Surface...

For meeting time, cost and quality targets in industrial sheet metal forming processes, correct formability prediction in a very early project stage has become a crucial factor. It is well known that the conventional Forming Limit Curve (FLC), which is most commonly used for this purpose, is only valid for linear strain paths. Yet, in most industri...

Prediction of localised necking is crucial for cost, time and material efficient production of sheet metal components. Especially in multi-step forming operations, nonlinear strain paths occur due to complex part and tool geometry as well as changing loading conditions during the forming process. Today, prediction of localised necking for such comp...

Forming limit strain curves of conventional aluminium alloy AA6014 sheets after loading with non-linear strain paths are presented and compared with D-Bressan macroscopic model of sheet metal rupture by critical shear stress criterion. AA6014 exhibits good formability at room temperature and, thus, is mainly employed in car body external parts by m...

Rising customer expectations regarding design complexity and weight reduction of sheet metal components alongside with further reduced time to market implicate increased demand for process validation using numerical forming simulation. Formability prediction though often is still based on the forming limit diagram first presented in the 1960s. Desp...

In this work, the experimental and numerical formability analysis of stamping " Mini-Tunnel " was studied using nonlinear strain path forming limits. Forming Limit Curves (FLC) of the standard and pre-stretched Advanced High Strength (AHS) steel grade DP600 were obtained. These FLCs were conducted in a standard Nakajima testing device at the Instit...

Conventional forming limit curves (FLCs) are inappropriate for describing formability for advanced high strength (AHS) steel sheets, since such steel grades experience fracture without localized necking occurrence. The aim of this work was to develop a fracture curve (FC) for the AHS steel grade DP980. The FC was determined by means of the Nakajima...

The press formability of the automotive materials such as aluminum alloys, magnesium alloys and steels is influenced by forming temperatures. While adjusting the temperature level of die, punch and binder, the lightweight materials can successfully be formed, especially for complex automotive body parts. The objective of this case study is to deter...

Forming limit curve is a tool to predict formability of sheet metals during forming operations. The conventional FLCs proposed by Keeler and Goodwin are applicable only for linear strain paths. They fail to predict true formability in case of non-linear strain paths which occur frequently in complex sheet metal operations. Hence, in order to predic...

The forming limit curve (FLC) is a common method to assess material formability in sheet metal forming processes. It is determined with the Nakajima or Marciniak test according to ISO 12004-2 [1]. The disadvantage of these test procedures is that the results are only valid for linear strain paths. In most real sheet metal forming processes, like de...