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Mechanical strength testing is known as one of the key methods to understand failure behavior of ceramics. Therefore, a wide number of tests have been developed throughout the last century. The most common testing methods are usually some types of uniaxial tensile or compressive tests, uniaxial bending tests and biaxial bending tests. Within biaxial testing, both the Ring-on-Ring- (RoR) as well as the Ball-on-Three-Balls-test (B3B) have proven to be the most common methods. That is why a comparison of these two methods, allowing to convert results from one method to the other, is of importance. While this topic was the focus of my previous research, my doctoral thesis is focused on the B3B-test as well as mechanical testing of 3D-printed ceramics.

For the B3B -test, non-linear effects are currently not considered when calculating the stress in a specimen. Some of these effects are large specimen deformations, plastic deformation of the balls, friction, or a change in contact-area between the balls and the specimen. These aspects will be investigated using Finite-Element-Analysis as well as empirical results. The goal is to ease the evaluation of the B3B -test while simultaneously increasing accuracy.

On the other hand, we are investigating the influence of small-scale surface structures on the measured strength in the collaborative research project CharAM. 3D-printed specimens often exhibit surfaces with distinct structures as a consequence of the additive manufacturing process. We are focused on the stereolithographic printing process, where the structure’s geometry and periodicity depend on the printing direction, e.g. the angle between the building direction and the specimen’s surface. Again, Finite-Element-Analysis and printing/testing in-house manufactured specimens will be the foundation of this research. Here, the aim is to predict the change in strength due to different printing directions in order to aid efficient component design.

„Left: Finite-Element-Analysis Model of the B3B-test to study the influence of friction

Right: Modelling of observed surface-structures with Finite-Element-Analysis and stress-distribution at the specimen’s surface “

Maximilian Staudacher

Department of Materials Science, Chair of Structural- and Functional Ceramics

Montanuniversitaet Leoben

Franz-Josef-Straße 18

A-8700 Leoben

Austria

maximilian.staudacher@unileoben.ac.at

https://isfk.unileoben.ac.at/