High Speed Tensile Test
For the design of a magnesium alloy component in the automotive industry the knowledge of material properties is very important - especially with varying temperature, wall thickness, and deformation speed and other parameters of the production process. Crash simulations require precise information about characteristic values at high deformation rates.
High speed tensile tests were carried out to determine the deformation behaviour of the materials under test.
The specimens were made from the magnesium alloy AZ91HP and AM50HP having a thickness of 2 mm. 15 specimens of each alloy were used for the experiments. The figures below shows the dimensions of the specimen.
A high speed testing machine HTM5008 (Roell Amsler, F max = 50 kN, v max = 8 m/s) was used for the experiment. The specimens were strained with a traverse speed of 8 m/s until rupture.
For contact free strain measurement a
Laser Doppler Extensometer (LDE) with a variable
measuring length was used. The LDE is based on a laser optical speed
measurement with a differential doppler principle. The motion of the specimen's
surface is recorded at two observation points which are fixed in space.
The
strain is calculated from the difference of the two motions.
The measuring
length was 50 mm.
The load acquisition was done with wire strain gauges of the type LY 13 1,5/120 (Fa. Hottinger Baldwin Messtechnik) which were attached to the gripping section of the specimens.
The figures below show a selection of
stress-strain-curves from both alloys. In the beginning the curves are close
together with a strain up to a maximum of 4 %. The alloy AZ91HP has a
breaking strain of 7,2 %. The tensile strength is between 260 and
340 MPa.
The alloy AM50HP has an essentially higher tensile strength of 13,1 %.
The curves with a higher tensile strength show a curved course for both alloys.
Stress-Strain-Diagram of AM50HP
Stress-Strain-Diagram of AZ91HP