Lenz J, Schwarz S, Schwickerath H, Sperner F, Schäfer A
Institut für Theoretische Mechanik, Universität Karlsruhe, Germany.
J Appl Biomater. 1995 Spring;6(1):55-64. doi: 10.1002/jab.770060108.
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 degrees 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.
本研究涉及一种针对金属 - 陶瓷结合的三点弯曲试验，该试验使用几何形状简单的试样（部分涂覆陶瓷的合金条），这种试样能够以合理的成本制造出来，并且具有足够的可重复性。文中介绍了借助有限元方法（FEM）计算此类试样中应力分布的过程。该数值分析的目的是：研究在大量实验中已证明会导致陶瓷贴面一端脱粘而非贴面中间出现裂纹的特定尺寸的金属陶瓷试样中的应力分布；并根据测量的临界弯曲力确定结合强度，其中要考虑合金杨氏模量的影响以及金属基底厚度与标准值可能存在的偏差。展示了多种金属 - 陶瓷组合的结合强度值。这些实验结果证明了该测试方法的可重复性及其对各种参数的敏感性。所提出的方法被提议作为另一种被提名作为国际标准的弯曲结合试验的替代方法。在该试验中，将金属陶瓷条在一根杆上弯曲，使试样端部成90度角，随后将其弄平，并目视检查断裂表面，看陶瓷在试样中间三分之一的主要部分是否与合金基底粘附。显然，这样的测试最多只能给出定性结果。
