Measuring forming limits
The AutoGrid® product family enables strain analysis on sheet metal parts and is well-stablished in sheet metal forming industry world‑wide.
The outstanding advantage of the AutoGrid® family is the fixed 4-camera approach used for both, specimens in material testing and stamped components in the press shop. That way, respective data sets can be well compared with best practise confidence.
While AutoGrid® comsmart is designed for shop floor measurements of stamped parts, provides AutoGrid® in-process the ideal solution for the materials lab where it is attached to a sheet metal testing machine. Typical use cases include FLC measurement by Nakazima test, bulge tests as well as tensile, and hole expansion tests.
The AutoGrid® in-process device measures the specimen while it is being test loaded, i.e. the system supports the recording of deformations and strains during a forming process. For the measurement of forming limit curves (FLC) the measuring head is mounted on a sheet metal testing machine (Erichsen, Zwick, Interlaken or others). Four cameras observe the specimen from different perspective views. They are exactly synchronized and image sequences are recorded with a rate of up to 200 x 4 frames per second. Any blur or disturbances due to the object’s motion are avoided by fully exploiting the potential of the IEEE1394b cameras. AutoGrid® in-process meets the requirement of testing new sheet metal materials at higher testing velocity.
The maximum frame rate of 200 image sets per second allows a punch velocity up to 20mm/s. Directly connected to the testing machine, the AutoGrid® in-process system captures additional data, e.g. punch stroke and drawing force which can be used to trigger the recording. Measuring time for one specimen is 3-5 minutes.
Current PC memory capacity secures appropriate length of image sequences and allows complete recording of the test. The evaluation of image sequences by the AutoGrid® in-process software is a user-friendly solution that automatically yields a time sequence of strain fields developing during specimen’s load cycle. The high precision image processing results in 0.1 mm punch depth resolution at punch speed of 25 mm/s.
The AutoGrid® post-processing includes a fast and accurate tool for the determination of the forming limit. The data analysis provides precise access to the maximum strain value just before necking and subsequent cracking occurs.
Powerful, convenient functions allow to create FLCs from a set of specimens very effectively and independent of operator skills. Polygon or spline functions can be used for the FLC interpolation. Data export is given in ASCII format, for example.
Users appreciate the unsurpassed performance for mate-rials testing and component analysis with one methodolo-gy, which makes the AutoGrid® in-process and comsmart devices the ideal solution for quality assurance purposes in sheet metal industry.