1 / 27

A new System for Single Particle Strength Testing of Grinding Powders

A new System for Single Particle Strength Testing of Grinding Powders. Einar List Joerg Frenzel Heiner Vollstaedt. AfraTest – not only for diamond. A brasive Powders Fra cture Strength Test er. Content. The specimen General machine layout Find, measure and pick the particle

swain
Download Presentation

A new System for Single Particle Strength Testing of Grinding Powders

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A new System for Single Particle Strength Testing of Grinding Powders Einar List Joerg Frenzel Heiner Vollstaedt

  2. AfraTest – not only for diamond • Abrasive • Powders • Fracture • Strength • Tester

  3. Content • The specimen • General machine layout • Find, measure and pick the particle • Place and crush the particle • Interpretation of the force / time plot • Results • Outlook

  4. Small and tough – a challenge • Sizes from 1000 µm down to 46 µm • Extremely wide fracture strength range • Automatic handling, new anvil for every particle

  5. AfraTest structure

  6. Digital image processing • Particle size (whatever this means) • Particle Shape • Position • Proximity to neighbours?

  7. Particle size • Minimum feret diameter

  8. Particle size • Minimum feret diameter • Maximum feret diameter

  9. Particle size • Minimum feret diameter • Maximum feret diameter • Area

  10. Particle size • Minimum feret diameter • Maximum feret diameter • Area • Area equivalent circle diameter

  11. Shape • Compactness calculated from Perimeter and Area

  12. Shape • Roughness • Convex Outline

  13. Position • Centre of gravity • Surrounding box • Surrounding box + safety distance must be empty

  14. Shape • Moments of inertia • Minimum and maximum moment of inertia • Ellipticity

  15. Images ready for processing 1.2 µm per pixel 4.5 µm per pixel

  16. Find and pick the particle • Particles on a glass plate • Monochromatic lighting • Autofocus optics • Sample holder mounted on a planar drive

  17. Place and crush the particle • 300 mm moveable anvil bars • 2000 N and 200 N range • 16 bit force resolution • 10,000 samples/s • Offset and excitation compensation

  18. Crushing a blocky diamond 159.2

  19. Crushing corundum

  20. Which fracture force? ?

  21. Which fracture force? For now we take the first fracture.

  22. Influence of the anvils • Indentation of the anvil • Lower anvil hardness causes higher fracture forces of the particles • Usage of different anvils for the same powder? Footprints of 55µm diamonds on WC anvils (z~10 µm)

  23. Fracture forces vs. size

  24. Do we know the fracture stress? The true Area A under stress is unknown! We don´t know the true stress! As imperfect as it is:we calculate CFS using the particle cross section area or the area of the inscribed circle

  25. Particle „strength“ vs. size

  26. Conclusions and outlook • AfraTest can handle the size range from fine powder to coarse grit • The measuring range allows for testing superabrasives as well as conventional abrasives • The first fracture is suitable for comparing materials. • A compressive fracture strength can be derived, making different assumptions for the loaded area. • AfraTest produces results on a common scale for abrasives and superabrasives.

  27. Thank you!

More Related