Test Specimen for Strength Testing of Additive Manufactured Ceramics by the VPP Process: the CharAM-Specimen
Description
The strength of additively manufactured ceramics may depend on the orientation of the direction in which tensile stresses act during testing with respect to the building direction (z). This may be due to ─ specific properties of the interfaces between the deposited layers ─ aliasing effects on surfaces ─ others In order to addresses this characteristic together with other aspects relevant to ceramics and the additive manufacturing process we aim at: ─ providing a test piece geometry with dimensions relevant to a specific ceramic AM method that can be manufactured in different orientations with respect to the building direction z. ─ providing 30+ individual test pieces for a statistical strength analysis produced in a time efficient single print job ─ providing test pieces with prospective tensile loaded faces that are neither the faces attached to the building platform during manufacturing nor the last printed layer ─ providing test pieces with prospective tensile loaded faces that are not in contact with kiln furniture during thermal processing A test specimens suitable for strength testing of additive manufactured ceramics is presented. A specimen consists of 48 test pieces in the form of carefully designed constant moment cantilever beams which are attached to a baseplate. The baseplate is formed by two connected solid plates with a specified angle (ꞵ) in between. By variation of this angle, different orientations of the cantilever axis (prospective tensile loaded face) with respect to the building direction of the AM process can be achieved. *.stl files for specimens with three different orientations/configurations are provided. Strength testing is performed by loading each cantilever at a pre-defined loading point (A) to failure. A description of the testing method as well as a detailed error analysis is provided in https://doi.org/10.1016/j.oceram.2023.100410 An example on how this specimen can be used to evaluate the strength of LCM ceramics can be found in https://doi.org/10.1016/j.oceram.2024.100557
Files
Steps to reproduce
*.stl files are provided for three different orientations. Each of the 48 cantilevers is identified by a binary code. A definition of the geometric parameters is given in the attached file "Description.pdf". All 48 cantilevers on a base plate are identical and have the same pixel arrangement. The *.stl files are suitable to be used on LCM/DLP printers with a pixel size of 40 µm × 40 µm or 60 µm × 60 µm. The *.stl files are scaled up to take into account a shrinkage factor of 1.22 in x, y direction and 1.28 in z direction which is suitable for Lithalox 350® (https://lithoz.com/de/materialien/lithalox-350/). These factors apply if the thermal processing steps recommend by the slurry provider are applied. On Lithoz CeraFab 7500 or CeraFab 8500 printer two of such test specimens can be produced in one print job. Two possible set-ups for the execution of the fracture tests are sketched in "Description.pdf". The tests can be performed using a universal testing machine or by using a shear tester. Suitable clamping devices and loading pins have to be used. Only cantilevers which fractured within the "test region" are valid fractures. This can be verified by measuring the length of the loose fractured cantilever pieces or by measuring the height of the stumps remaining on the base plate. The geometry parameters h and α which are necessary to calculate the fracture strength should be determined for each cantilever.
Institutions
Categories
Funding
Österreichische Forschungsförderungsgesellschaft
877684
AiF Projekt
ZF4076461LT9 (Fraunhofer IKTS), ZF4778001LT9 (Gramm GmbH)