✍ Scribed by Jürgen Lenz; Siegmund Schwarz; Hans Schwickerath; Dr. Franz Sperner; Astrid Schäfer
No coin nor oath required. For personal study only.
This study deals with a three-point flexure test for the metal-ceramic bond involving geometrically simple specimens (alloy strips partly coated with ceramic) that can be fabricated with reasonable expenditure and sufficient reproducibility. The calculation of the stress distribution in such specimens with the aid of the finite-element method (FEM) is presented. The aim of this numerical analysis is: to investigate the stress distribution in a ceramometallic specimen with dimensions that, in a large number of experiments, have proven to lead to debonding at one end of the ceramic veneer instead of a crack in the middle of the veneer; and to assign a bond strength to the measured critical bending force that takes into account the influence of the Young's modulus of the alloy as well as a possible deviation of the thickness of the metal substrate from the standard value. Bond strength values of a variety of metal-ceramic combinations are demonstrated. These experimental results demonstrate the reproducibility of the test method as well as its sensitivity to diverse parameters. The presented method is proposed as an alternative to another flexure bond test nominated for international standard. In this test ceramometallic strips are bent over a rod to a 90" angle of the specimen ends, subsequently flattened, and the fracture surface visually inspected for adherence of the ceramic to the alloy substrate along the predominant part of the middle third of the specimen. It is clear that such a test can at most deliver qualitative results.
📜 SIMILAR VOLUMES
Strength data are presented on totally new room temperature setting cements in CaO-SiO2-P2Os-I-I20 system. These compositions lie in the range of CAO:45-65, P2Os:29-5ff, SiO-2:4-20 (wt.%) and were prepared by sol-gel techniques ufmgcalcium nitrate and lactate, phosphoric acid and Ludox as precursors