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NCAL: Forming Limit Press
A forming limit press is available in the NIST Center for Automotive Lightweighting. This machine has been designed based on a modified Marciniak punch stretching geometry. Since the sheet sample is being stretched in conjunction with a driver sheet, there are unquantifiable friction stresses between the counter slipping sheets and between the sheets and the tooling. Thus, X-ray diffraction is used to measure the stress in situ in the sheet and, along with strains measured using DIC, form the multiaxial stress-strain curve. The flow stresses in the tensile principle stress quadrant can be mapped from initial yield through ultimate failure.
In addition to the test machine capabilities listed below, the default configuration includes:
- A stereo Digital Image Correlation (DIC) strain mapping system
- An X-ray diffraction (XRD) system to measure lattice strains and macroscopic stresses in situ
[Currently offline for repairs and upgrades]
Specifications/Capabilities
Testing Machine Capabilities:
- Two hydraulic axial actuators
- 500 kN max. punch force
- 500 kN max. hold down force
- Punch travel ±25 mm
- Force or displacement control
- Marciniak or Nakajima punch shape
- 100 mm (4 inch) and 200 mm (8 inch) dies are available
The instrument pages for NCAL DIC Measurement Systems and NCAL Diffraction Stress Measurement Systems include details of the DIC and XRD systems that can be used on this frame