Probabilistic Design and Reliability of Silicon Carbide Ceramics

1982 ◽  
Vol 104 (3) ◽  
pp. 635-642 ◽  
Author(s):  
M. Srinivasan ◽  
S. G. Seshadri
Keyword(s):  
Silicon Carbide ◽  
Crack Growth ◽  
Elevated Temperatures ◽  
Ceramic Materials ◽  
Material Behavior ◽  
Evaluation Methodology ◽  
Probabilistic Design ◽  
Proof Testing ◽  
Risk Of Rupture ◽  
Silicon Carbide Ceramics

Ceramic materials generally lack ductility and toughness, and exhibit variability in properties. In order to design with ceramic materials, the variation in material properties, especially strength, has to be statistically analyzed for reliability. Conventional design can be done with calculations utilizing safety factors. However, modern design aspects include proof testing and appropriate nondestructive evaluation methodology. Possible microstructural changes which occur during proof testing may influence subsequent material behavior and must be included in the design methodology. The temperature dependence of flexural strength of two engineering structural ceramics—single-phase sintered alpha silicon carbide and two-phase fine grain reaction-bonded silicon carbide—are examined. Using Weibull statistics, the risk of rupture for various stress levels has been derived from flexural versus tensile strength relationships. Ceramic life prediction considers subcritical crack growth and strength degradation in service environments. The slow crack growth possibilities at elevated temperatures for sintered alpha silicon carbide are examined in dynamic stressing rate and stress rupture experiments. Crack arrest and crack propagation resistance during proof testing and their implications in the probabilistic design with ceramics are analyzed.

On the Role of Grain-Boundary Films in Optimizing the Mechanical Properties of Silicon Carbide Ceramics

2004 ◽  
Vol 818 ◽  
Author(s):  
R. O. Ritchie ◽  
X.-F. Zhang ◽  
L. C. De Jonghe
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
Silicon Carbide ◽  
Grain Boundary ◽  
Elevated Temperatures ◽  
Boundary Structure ◽  
Intergranular Films ◽  
Grain Boundary Structure ◽  
Silicon Carbide Ceramics

AbstractThrough control of the grain-boundary structure, principally in the nature of the nanoscale intergranular films, a silicon carbide with a fracture toughness as high as 9.1 MPa.m1/2 has been developed by hot pressing β-SiC powder with aluminum, boron, and carbon additions (ABC-SiC). Central in this material development has been systematic transmission electron microscopy (TEM) and mechanical characterizations. In particular, atomic-resolution electron microscopy and nanoprobe composition quantification were combined in analyzing grain boundary structure and nanoscale structural features. Elongated SiC grains with 1 nm-wide amorphous intergranular films were believed to be responsible for the in situ toughening of this material, specifically by mechanisms of crack deflection and grain bridging. Two methods were found to be effective in modifying microstructure and optimizing mechanical performance. First, prescribed post-annealing treatments at temperatures between 1100 and 1500°C were seen to cause full crystallization of the amorphous intergranular films and to introduce uniformly dispersed nanoprecipitates within SiC matrix grains; in addition, lattice diffusion of aluminum at elevated temperatures was seen to alter grain-boundary composition. Second, adjusting the nominal content of sintering additives was also observed to change the grain morphology, the grain-boundary structure, and the phase composition of the ABC-SiC. In this regard, the roles of individual additives in developing boundary microstructures were identified; this was demonstrated to be critical in optimizing the mechanical properties, including fracture toughness and fatigue resistance at ambient and elevated temperatures, flexural strength, wear resistance, and creep resistance.

Slow crack growth in ceramic materials at elevated temperatures

1975 ◽  
Vol 6 (4) ◽  
pp. 707-716 ◽  
Author(s):  
A. G. Evans ◽  
L. R. Russell ◽  
D. W. Richerson
Keyword(s):  
Crack Growth ◽  
Elevated Temperatures ◽  
Slow Crack Growth ◽  
Ceramic Materials

Microwave Curing of Silicon Carbide Ceramics from a Polycarbosilane Precursor

1994 ◽  
Vol 347 ◽  
Author(s):  
Tzyy-Heng Alex Shan ◽  
Robert Cozzens
Keyword(s):  
Silicon Carbide ◽  
Thermal Processing ◽  
Ceramic Materials ◽  
Sole Source ◽  
Curing Temperature ◽  
Polymeric Precursor ◽  
Microwave Curing ◽  
Silicon Carbide Ceramic ◽  
Carbide Ceramics ◽  
Silicon Carbide Ceramics

ABSTRACTSilicon carbide ceramic materials have been successfully formed from commercially available polycarbosilane using microwave radiation as the sole source of heat. Conventional thermal processing of the same polymeric precursor was also studied for comparison with microwave processing. Microwave heating enhances crystallinity at much lower curing temperature and within shorter times. Possible explanations for microwave enhanced processing are proposed.

Production of Porous Silicon Carbide Ceramics by Starch Consolidation Technique

2012 ◽  
Vol 727-728 ◽  
pp. 821-825 ◽  
Author(s):  
Rodrigo Mende Mesquita ◽  
Ana Helena de Almeida Bressiani
Keyword(s):  
Silicon Carbide ◽  
Porous Silicon ◽  
Chemical Properties ◽  
Ceramic Materials ◽  
Structural Ceramic ◽  
Porous Silicon Carbide ◽  
Carbide Ceramics ◽  
Silicon Carbide Ceramics ◽  
Starch Consolidation ◽  
And Chemical Properties

Silicon carbide is used to produce abrasive and high-temperature structural ceramic materials due to its mechanical and chemical properties. The possible applications of porous silicon carbide ceramics are diesel engines catalysers and molten metal filters. In the last years the starch gained importance as a pore-forming and consolidation agent, due to it is environmental friendly and easily processing. The current work uses starch (corn, rice and potato) as pore forming and consolidation agent. The samples sintered at different sintering times were characterized by density and microstructure (XRD, SEM). The results show that the samples presented porosity between 20 and 40% and the microstructures obtained is homogeneous with a pore size similar to the starch particle added.

Evaluation of slow crack growth parameters for silicon carbide ceramics

1982 ◽  
Vol 17 (5) ◽  
pp. 1297-1302 ◽  
Author(s):  
S. G. Seshadri ◽  
M. Srinivasan ◽  
G. W. Weber
Keyword(s):  
Silicon Carbide ◽  
Crack Growth ◽  
Growth Parameters ◽  
Slow Crack Growth ◽  
Carbide Ceramics ◽  
Silicon Carbide Ceramics

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

Fatigue Investigation of Elastomeric Structures

2010 ◽  
Vol 38 (3) ◽  
pp. 194-212 ◽  
Author(s):  
Bastian Näser ◽  
Michael Kaliske ◽  
Will V. Mars
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Material Behavior ◽  
Period Effect ◽  
Numerical Representation ◽  
Material Force ◽  
Strain Behavior ◽  
Dissipative Effects ◽  
Elastomeric Materials

Abstract Fatigue crack growth can occur in elastomeric structures whenever cyclic loading is applied. In order to design robust products, sensitivity to fatigue crack growth must be investigated and minimized. The task has two basic components: (1) to define the material behavior through measurements showing how the crack growth rate depends on conditions that drive the crack, and (2) to compute the conditions experienced by the crack. Important features relevant to the analysis of structures include time-dependent aspects of rubber’s stress-strain behavior (as recently demonstrated via the dwell period effect observed by Harbour et al.), and strain induced crystallization. For the numerical representation, classical fracture mechanical concepts are reviewed and the novel material force approach is introduced. With the material force approach at hand, even dissipative effects of elastomeric materials can be investigated. These complex properties of fatigue crack behavior are illustrated in the context of tire durability simulations as an important field of application.

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