Introduction
New in Situ Biaxial Testing Apparatus
Design Concept
Weight | 2.3 kg |
Dimensions | 190 mm × 200 mm × 73.2 mm |
Travel range per actuator | 10 mm |
Maximum force per actuator | 44 N |
Minimum step size per actuator | 10 nm |
Stiffness actuators | 16 N/μm |
Resolution nano sensors | 1 nm |
Installation in a Scanning Electron Microscope
Installation at the Synchrotron
Specimen Geometry
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At the centre the sample should not be thicker than a few tens of micrometres, in order to work in transmission with medium energy (5–25 keV) X-ray beams. This strongly depends on the absorption and scattering cross-section of the material used.
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The sample needs to be robust enough so that it can be handled and mounted in the test rig without affecting the local microstructure.
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The stress state should be homogeneous within a central area with a diameter of ~0.1 mm.
Specimen Fabrication Procedure
Application of the New Testing Setup
Machine Characterization
Machine compliance
Sample - grip alignment
Mechanical Tests
Element | Al | Mg | Mn | Fe | Si | Others |
---|---|---|---|---|---|---|
wt% | 94.3 | 5.33 | 0.16 | 0.12 | 0.07 | 0.02 |
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With decreasing thickness of the sample the amount of applied strain increases, as is witnessed by the larger deformation of the inner circle. However, the deformation outside the inner circle cannot be neglected.
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The ratio between the strain along the minor and major axis is relatively large ( −0.63 for the inner circle at the end of the test). This is clearly larger than the expected plastic Poisson’s ratio and is the related to the ring effect, as discussed earlier in the section on Sample Geometry.
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The sample exhibits strain bursts characterized by sudden increases in strain along both major and minor axis (indicated by the arrows in Fig. 9), which can be related to the PLC effect.