Impact of optical strain rate controlling on the determination of mechanical sheet metal properties

Naumann D, Merklein M (2024)

Publication Language: English

Publication Type: Conference contribution, Conference Contribution

Publication year: 2024

Event location: Hohenkammer DE


A key aspect of state of the art part, tool and process
development is the prediction quality of numerical simu-
lations. Costs and time in the design process can be
reduced only with sufficiently reliable results. To obtain
meaningful results, precise material data is an important
input variable. In the state of the art material characteri-
zation with universal testing machines, material beha-
vior is either determined at constant crosshead speed or
at constant strain rates, only in the elastic region, accor-
ding to ISO 6892-1 for tensile tests. Due to the fact, that
commercial simulation software expects strain
hardening data at constant strain rates, an error is made
with current characterization tests at non-constant strain
rates, due to the strain rate sensitivity that most metals
exhibit. To obtain constant strain rate material data,
optical controlled characterization tests can be
In the scope of this research, an optical strain rate con-
trolled tensile testing method was developed for and ap-
plied to uniaxial tensile tests to investigate its influence
on the measurement of mechanical properties of typical
drawing grade steels. Therefore, displacement strain
rate controlled (DSRC) and optical strain rate controlled
(OSRC) tensile tests at room temperature with a nomi-
nal strain rate of 0.004 1/s were conducted and evalua-
ted. Flat specimens according to ISO 6892-1 with a
gauge length of 80 mm were used. The tests were per-
formed with a universal testing machine (ZwickRoell
GmbH & Co. KG.) and the strain was measured and
controlled with a 3D DIC System (GOM ARAMIS 12M
SRX). The both commercial common steels DP600
(CR330Y590T-DH) and DC05 (CR4) at a nominal
thickness of 1.2 mm were analyzed regarding strain rate
evolution during tensile testing and how OSRC
influences the strain rate development.
The OSRC-method shows the potential to obtain materi-
al data in material testing at constant strain rates over
the complete tensile testing trial from the elastic area to

the failure of the specimen. For both investigated steels
DP600 and DC05, the influence of the testing method is
negligibly small. The root mean squared error of the av-
eraged strain rates for DP600 and DC05 was decreased
from 0.011 respectively 0.012 to 2.4·10-5 respectively
5.6·10-5 with the OSRC-method. In future work, an
adaptive strain rate controlling will be developed, to
obtain material data to higher strains in the area of dif-
fuse necking. This can be applied to testing at elevated
temperatures with e.g. electrically conductive specimen
heating, where necking starts at an early stage due to
inhomogeneous specimen temperatures.

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Naumann, D., & Merklein, M. (2024). Impact of optical strain rate controlling on the determination of mechanical sheet metal properties. In Proceedings of the 6th MATFEM Conference. Hohenkammer, DE.


Naumann, David, and Marion Merklein. "Impact of optical strain rate controlling on the determination of mechanical sheet metal properties." Proceedings of the 6th MATFEM Conference, Hohenkammer 2024.

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