Determination of fracture toughness of fine ceramic materials
According to user requirements, various mechanical properties of non-metallic materials can be measured, including maximum strength, elastic modulus (E), constant compressive strength, constant load elongation, and yield strength. For metallic materials, properties such as yield strength, non-proportional strength, total compressive strength, tensile or compressive strength, and elongation can be determined.
Standards for evaluating the fracture toughness, flexural strength, and elastic modulus of fine ceramic materials include GB/T 10700-2006, GB/T 6569-2006, GB/T 23806-2009, and others. Fine ceramics, such as silicon nitride and aluminum nitride, are known for their excellent acid and alkali resistance, high insulation performance, and ability to function in extreme environments. However, they suffer from high brittleness, poor impact resistance, and a tendency to fracture suddenly. Therefore, improving and accurately measuring their fracture toughness is crucial for broader industrial applications.
There are multiple theoretical methods for measuring fracture toughness, such as the single-edge notched beam three-point or four-point bending method, the tension method, and the indentation method. The choice of test method typically depends on the material's brittleness. After analyzing and comparing these methods, this paper suggests that the micro-indentation method is more suitable for measuring the fracture toughness of fine ceramics due to its precision and reliability.
From the experimental results, it is evident that the applied load significantly affects the deviation in the final measurements. When the load is in the kilogram range, the crack length fluctuates considerably, leading to larger relative errors. For silicon nitride, the relative error in crack length is relatively high, while for nitrogen carbide, the error exceeds acceptable limits. However, when the load is increased, the crack length becomes smaller under the same loading conditions, and the relative errors for both silicon nitride and nitrogen carbide fall within acceptable ranges. Due to the inherent brittleness of silicon nitride, cracks tend to propagate unpredictably, resulting in higher relative errors. In contrast, nitrogen carbide exhibits more consistent crack propagation, leading to lower variability in measurement results.
For further understanding, you can refer to the article: Determination of Fracture Toughness of Fine Ceramic Materials.
Editor: Hardware Business Network Information Center.
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