Investigation on the influence of combined shear loads on the forming limit for high strength steels

Held, Christian; Schleich, Ralf; Sindel, M.; Liewald, Mathias

doi:10.1007/s12289-009-0581-y

Cited by 8 publications

(5 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, as is shown in Figure 1, the standard methods for testing FLD are mainly used to characterise formability under certain in-plane load conditions from uniaxial tension, through plane-strain to biaxial stretching. But in industrial forming processes not only in-plane loads, but a mixture of in-plane, pure-shear and combined shear-and tension loads can also be observed [8,10]. Today there is still a lack in testing equipment for those combined load conditions because with conventional testing set-ups no superposed shear rates can be realized.…”

Section: Introduction Of Theoretical Models and Experimental Methods mentioning

confidence: 99%

See 1 more Smart Citation

Determination of instability of a DP 980 steel sheet under different stress states based on experiment and theoretical models

et al. 2016

View full text Add to dashboard Cite

Abstract. It is generally accepted that the formability of sheet metal is limited by the onset of instability which can be described by forming limit diagram (FLD) in ε1-ε2 space. Common tests for FLD data usually cover strain ratio range from uniaxial to equal biaxial stretching, −1/2 ≤ ε2/ε1 ≤ 1. In this paper a new design of cruciform type specimen for uniaxial stretching is proposed to test formability with strain ratios in the range from shear to tension, −1 ≤ ε2/ε1 ≤ -1/2 which can be controlled by the geometry parameters. The forming limit of a DP 980 steel sheet was determined using both conventional method and proposed specimen with strain ratios from −1 ≤ ε2/ε1 ≤ 1. Then the experimental results were drawn in both ε1-ε2 and εeq-σm/σeq spaces, and the predicted results based on Hill, Swift, M-K, and Hora instability models were compared with the experimental ones. The formability features of the studied steel in whole strain ratio range and differences among the investigated theoretical models were finally discussed. The results indicate that the M-K instability model shows better prediction of the studied steel compared to the other models investigated in this research.

show abstract

Section: Introduction Of Theoretical Models and Experimental Methods mentioning

confidence: 99%

“…Recently, Shouler et al [8] and Held et al [10] proposed similar type of samples for characterising material formability under shear-tension loads with relatively simple set-up. However, the obtained strain paths are almost pure shear, which not easily occur during forming process.…”

Section: Introduction Of Theoretical Models and Experimental Methods mentioning

confidence: 99%

Determination of instability of a DP 980 steel sheet under different stress states based on experiment and theoretical models

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Another way is to take the cutting process into account. The strain on the roll-in side of the blank was measured close to the cut-edge after cutting with an Aramis system [82]. The maximum strain value (close to the cut-edge) was treaded as consumed and therefore subtracted from the forming limit curve.…”

Section: Prediction Of Edge-cracking In a Forming Simulationmentioning

confidence: 99%

“…The maximum strain value (close to the cut-edge) was treaded as consumed and therefore subtracted from the forming limit curve. The result is called FLC-Edge (FLC-E) [83].…”

Section: Prediction Of Edge-cracking In a Forming Simulationmentioning

confidence: 99%

Overview and comparison of various test methods to determine formability of a sheet metal cut‐edge and approaches to the test results application in forming analysis

Schneider

Geffert

Peshekhodov

et al. 2015

Materialwissenschaft Werkst

View full text Add to dashboard Cite

This paper presents an overview of published test methods for determination of formability of a sheet metal cut-edge. The presented test methods were developed to evaluate formability of a sheet metal edge that was produced by shear cutting. Due to high local strains, hardening, or even microcracks, the cut-edge might have less formability than the base material. The presentation of the tests is structured according to the three steps each test can be divided into: cutting, forming and evaluation. Similarities and differences concerning these steps were worked out. Additionally, a classification of the tests is made regarding their strain gradients in the vicinity of the cut-edge. For this, finite element models of exemplary tests were built up using LS-DYNA explicit and analyzed accordingly. Evaluation approaches that go beyond the common hole expansion ratio (HER) from the hole expansion test (HET) standardized in the ISO 16630 are also described. The tests can be used not only for a quantitative comparison of materials and cutting processes with regard to the cut-edge formability but to determine input data for the finite element analysis (FEA) of forming processes to allow a simulation based cut-edge failure prediction. The paper also presents appropriate procedures on the transfer of the test results into the FEA of forming of a workpiece with a cut-edge.

show abstract

“…Also influence of through thickness shear has been analysed regarding incremental sheet forming processes [9]. A new testing procedure for characterising formability under pure-shear (in plane) and shear tensions loads was published in [11,10]. Three novel shear sample geometries have been presented in [10] to adjust external load application to different shear proportions in testing region of specimen.…”

Section: Introductionmentioning

confidence: 99%

Novel Semi-Empirical Model for Forming Limit Prediction of Sheet Metal Material with Regard on Effects of Shear-Tension Loads

2010

Self Cite

View full text Add to dashboard Cite

The use of lightweight materials offers substantial strength and weight advantages in car body design. For characterization of capability of sheet material dedicated to deep drawing processes in the automotive industry, mainly Forming Limit Diagrams (FLD) are used. However, investigations conducted at the Institute for Metal Forming Technology using new specimen geometries have shown that formability of High Strength Steel Sheet Material changes by superposing shearing on in-plane tension loads. Hence, these mixed stress and strain conditions including shearing effects can occur in deep-drawing processes of complex car body parts. But these changes in materials formability nowadays cannot be described sufficiently by using conventional FLC-criterion. Considering such aspects in defining suitable failure criterions a new semi-empirical model has been developed considering the effect of shearing in sheet metals formability. This novel model is capable to separate shear and in-plane tension loads by using a special strain definition. For experimental calibration of so called Shear Forming Limit Curve (SFLC) several standardized and enhanced material testing procedures with novel specimen geometries are necessary. In this contribution firstly the need of enhanced material description and additionally the theory SFLC-Model is presented. For experimentally calibration required input parameters are determined by special specimen geometries.

show abstract

Investigation on the influence of combined shear loads on the forming limit for high strength steels

Cited by 8 publications

References 1 publication

Determination of instability of a DP 980 steel sheet under different stress states based on experiment and theoretical models

Determination of instability of a DP 980 steel sheet under different stress states based on experiment and theoretical models

Overview and comparison of various test methods to determine formability of a sheet metal cut‐edge and approaches to the test results application in forming analysis

Novel Semi-Empirical Model for Forming Limit Prediction of Sheet Metal Material with Regard on Effects of Shear-Tension Loads

Contact Info

Product

Resources

About