Creep Fracture toughness

Excellent high temperature properties [1] Strength, creep, fracture toughness, hardness, corrosion/erosion resistance, good thermal schock resistance make silicon nitride ceramics ideal materials for highly stressed structural applications at high temperatures such as internal combustion engines and gas turbines [2,3]. 

Mechanical Modulus Yield and tensile strength Hardness Fracture toughness Fatigue strength Creep strength Damping... 

Answers Structure-sensitive properties yield strength, hardness, tensile strength, ductility, fracture toughness, fatigue strength, creep strength, corrosion resistance. 

Tensile properties Compression strength Fracture toughness Creep resistance... 

Fig. 2.3 Elevated fracture toughness of alumina/20 vol.% SiC whisker composite showing a linear response up to temperatures of 1000°C. At temperatures 1100°C, creep damage results in apparent increases in toughness.

In this paper, the importance of particle and whisker reinforcement to creep and creep rupture behavior of ceramics is discussed. Particle and whisker additions generally increase both the fracture toughness and creep resistance of structural ceramics. These additions also act as nucleation sites for cavities. Cavities form preferentially in tensile specimens. This results in a creep asymmetry, in which composites creep faster in tension than in compression. As a consequence of cavitation, the stress exponent for creep in tension 6-10,... 

Silicon nitride ceramics should have high flexural strength and fracture toughness at room temperature and good creep resistance at elevated temperatures. Because these properties are determined by the microstructure of these ceramics, further improvement of these ceramics is possible through alloy design. The following sections will be devoted to micro-... 

Elastic modulus Bulk modulus Poisson s ratio Tensile strength Compressive strength Modulus of rupture Fracture toughness Hardness Fatigue Creep... 

Key words lattice structure, bonding energy, elasticity, strength, creep resistance, fracture toughness... 

The quantities N, M, A, a, and G are determined independently from uniaxial deformation tests, and Kc is determined from fracture toughness tests. The process zone size dr may be estimated metallographically from polished or fractured specimens. In other words, no empirical fitting parameters are involved in this relationship between crack growth and creep deformation rates. 

Figure 17. Fracture toughness, tensile strength, and tensile elongation at room temperature, and reciprocal secondary creep rate measuring the creep resistance as a function of microstructure (schematic) for two-phase TiAl alloys (Kim and Dimiduk, 1991).

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