Material Tester Sheet Metal Testing – Quick Test Deep-drawn Sheets
with force-displacement diagram
Problem + Solution Sheet Metal Testing Machine Sheet Metal Testing
In the production of deep-drawn parts are sent to the deep-drawn sheet sometimes extreme requirements are placed on them: high or extreme elongation, good cold formability, uniform thinning, fine grain to avoid cracking ...
If a sheet metal coil is fed into the production process without being checked, considerable damage can occur (if the quality is not sufficient). If a material defect is only discovered at the end of the process, not only is setup time lost, but valuable production capacity is wasted. Added to this are complaints to the supplier, disposal of defective parts and new production (hopefully with suitable sheet metal...).
This can be avoided by checking the sheet metal before production begins (ideally when the coil is still loaded on the delivery truck).
The FRAUNHOFER Institute IWU in Chemnitz has developed an intelligent quick test for this. Based on the standardized ERICHSEN cupping test, a force measuring cell and a high-resolution displacement measuring system were integrated into a specially developed tool. Using intelligent, self-learning evaluation software, it is possible to make a statement about the suitability of the sheet within a few minutes: Use a grinder/portable nibbler to remove a piece of sheet, place it in the cupping tool and start the test. Using the stored library, the FRAUNHOFER evaluation software determines the suitability of the sheet for your deep-drawing process within just around 3 minutes.
Sheet metal testing machine reinvented:
To learn more about this topic and the possible extension of the hole expansion test (hole extension test) please send us a short initial E-mail.
Research topic and project idea for sheet metal testing
Material Tester – Sheet Metal Testing Machine 2.0
The timely qualification of sheet metal batches for forming saves costs and production downtime if the following questions can be clarified in advance:
- Does the delivery quality correspond to the standard?
- If the deep drawing process fails during forming / subsequent process steps
Previous qualifications:
- material property determination via tensile tests
- tensile specimen production (punching and grinding)
- Tensile test execution + evaluation
- Conventional evaluation by tensile test is complex and expensive
Nevertheless, exact conclusions about formability based on tensile tests are often not possible
- Elongation at break + tensile strength are determined from only uniaxial test
- R+N value determination does not always correlate with the deep drawing requirements
- The material characteristics are often only of limited significance for e.g. drawn parts
How can a rational statement be made about the depth capability?
- Determination of pseudo-material parameters
- the test is similar to the ERICHSEN cupping
- The test simulates a forming load condition
- Determination of process-specific parameters through tool-integrated miniature experiments
Prediction using ML-based methods (machine learning):
- Qualitative statement (tears / does not tear)
- In addition to the cupping capacity, quantitative parameters may also be obtained (Rp0,2, Rm, A…)
- Fast incoming goods inspection / detection of rejects
- Can also be used by semi-skilled employees (no material tester required)
Miniature experiments enable simulation tailored to your production conditions
- Laboratory system with measuring tools and hydraulic press (mobile on request)
- available at IWU from autumn 2021
- Various test geometries according to your requirements are possible / design according to load condition required
- Future perspective: Integrated as an inline solution in your forming tool (Industry 4.0)
- Integrated in the forming tool / on the blank shear
- Test geometry in the waste area (pulling system)
- Use of existing form elements (screw-on domes, pull-throughs...)
ML-Based Evaluation of ERICHSEN Cupping (Machine Learning)
Recording of the force-displacement curves during the cupping test
Teaching the models in the training phase:
- Instead of the maximum values of a tensile test (Rp02 / Rm / A), the test curves are used as the basis for the evaluation
- The test also provides a statement on suitability (finished part quality as well as derived parameters)
A prediction of the target values for production is made: - An estimate "Good" or "committee"
- In addition, the material properties are shown as an estimate
