Fracture toughness (KIc) of a dental porcelain determined by fractographic analysis
Fracture toughness (KIc) of a dental porcelain determined by fractographic analysis
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DOI：
10.1016/s0109-5641(99)00055-x
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发表时间：
1999-09-01
期刊：
影响因子：
5
通讯作者：
Xu, K
中科院分区：
文献类型：
--
作者：
Scherrer, SS;Kelly, JR;Xu, K
目标：在弯曲测试后进行压痕裂纹的断口分析，作为先进陶瓷中断裂韧性 K-Ic 测定的 ASTM (1999) 标准的一部分。该方法取决于材料对断口解释的有利程度。本研究的目的是评估断口法在长石牙瓷断裂韧性方法中的应用，其中使用两种受控缺陷梁弯曲技术对 K-Ic 进行断口测量和数值测量。 方法：将以下 K-Ic 测定方法应用于白榴石体积分数为 15-20% 的牙瓷： (1) 弯曲表面裂纹 (SCF)（取决于断口分析）； (2) 压痕载荷为 9.8 和 19.6 N 时的压痕强度 (IS)（应用标准数值计算和断口分析）。测试环境为 (1) 环境空气（IS 和 SCF）和 (2) 流动干燥氮气 (SCF)。 结果：在环境空气中的两种压痕载荷（9.8 和 19.6 N）下，IS 技术的数值 K-Ic 值和断口 K-Ic 值之间没有发现显着差异，尽管 K-Ic 值对压痕载荷敏感。由于残余应力的存在，在所有 IS 样本中均观察到稳定的裂纹扩展，初始裂纹尺寸 (a(initial)) 和临界裂纹尺寸 (a(critical)) 之间的差异证明了这一点。对于 SCF 方法，在空气中测试的样品与在干燥氮气中测试的样品之间的韧性存在显着差异，但没有观察到化学辅助缓慢裂纹扩展 (SCG) 的断口证据。 意义：ASTM 标准描述的 SCF 方法适用于长石瓷，并产生与 IS 程序的数值韧性计算非常相似的结果。然而，与多晶陶瓷相比，这种玻璃陶瓷的表面裂纹的断口分析有些困难。在通过检查断裂表面的缺陷尺寸来估计韧性时，有关稳定裂纹扩展或缓慢裂纹扩展及其断口外观的知识至关重要，因为如果不考虑这些影响，可能会出现较大的计算误差。 (C) 1999 年牙科材料学院。由爱思唯尔科学有限公司出版。保留所有权利。
Objectives: Fractographic analysis of indentation cracks is performed following flexure testing as pare of the ASTM (1999) standard for fracture toughness, K-Ic, determination in advanced ceramics. This method depends on the conduciveness of the material towards fractographic interpretation. The purpose of this study was to evaluate the use of fractography in fracture toughness methods with a feldspathic dental porcelain, in which K-Ic was measured fractographically as well as numerically using two controlled-flaw beam bending techniques.Methods: The following methods for K-Ic determination were applied to a dental porcelain containing a leucite volume fraction of 15-20%: (1) surface crack in flexure (SCF) (dependent upon fractographic analysis); and (2) indentation strength (IS) at indentation loads of 9.8 and 19.6 N (applying both standard numeric calculations and fractographic analysis). The testing environments were (1) ambient air (IS and SCF) and (2) flowing dry nitrogen (SCF).Results: No significant differences were found between numeric and fractographic K-Ic values for the IS technique at both indentation loads (9.8 and 19.6 N) in ambient air, although K-Ic values were sensitive to indentation load. Due to the presence of residual stresses, stable crack extension was observed fractographically in all IS specimens, as evidenced by differences between initial (a(initial)) and critical (a(critical)) crack dimensions. For the SCF method, there was a significant difference in toughness between specimens tested in air versus dry nitrogen, however no fractographic evidence for chemically assisted slow crack growth (SCG) was observed.Significance: The SCF method as described by the ASTM standard was applicable to the feldspathic porcelain and produced very comparable results with the numeric toughness calculations of the IS procedure. However, fractographic analysis of the surface crack was somewhat difficult for this glassy ceramic compared with polycrystalline ceramics. Knowledge about stable crack extension or slow crack growth and its fractographic appearance is essential when estimating the toughness from examination of flaw dimensions on fractured surfaces since large calculation errors may occur if these effects are not taken into account. (C) 1999 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.