Ceramic fracture, fatigue

As high performance ceramic matrix composite systems, such as Melt Infiltrated (MI) SiC/SiC, are being considered for advanced gas turbine engine applications, the characterization of the material becomes more important. A series of tests were conducted where Pt and Ni sheathed Pt thermocouples were used to monitor temperature for short and long duration fast fracture, fatigue and creep tests. While it is known that Si forms eutectics with Pt and Ni, this was initially not considered an issue. But since Ml SiC/SiC composite achieves much of its performance from the infiltrated phase of Silicon (for high conductivity and low porosity), it was felt that further study of possible interactions of the Si phase has to be considered. 

O. M. Jadaan, andN. N. Nemeth, Transient Reliability of Ceramic Structures, Fatigue Fracture of Engineering Materials and Structures, Vol. 24, 2001, pp. 475 487. 

Ceramic-matrix fiber composites, 26 775 Ceramics mechanical properties, 5 613-638 cyclic fatigue, 5 633-634 elastic behavior, 5 613-615 fracture analysis, 5 634-635 fracture toughness, 5 619-623 hardness, 5 626-628 impact and erosion, 5 630 plasticity, 5 623-626 strength, 5 615-619 subcritical crack growth, 5 628—630 thermal stress and thermal shock, 5 632-633... 

Brittle erosion is the loss of material from a solid surface due to fatigue cracking and brittle cracking caused by the normal collisional force Fn. Materials with very limited capacity for elastic and plastic deformation, such as ceramics and glass, respond to particle impacts by fracturing. The yield stress for brittle failure Fb for normal impacts is about... 

S. Suresh and E. K. Tschegg, Combined Mode I-Mode III Fracture of Fatigue Precracked Alumina, Journal of the American Ceramic Society, 70[10] 726-733 (1987). 

Approaches to characterizing the creep-fatigue fracture of ceramic composites. 

Differences in the macroscopic and microscopic fatigue fracture behavior of ceramic composites under static and cyclic loading at high temperatures. 

Early work (e.g., Refs. 44 and 45) on silicon nitride ceramics for a limited range of high temperature cyclic loading conditions led to the hypothesis that the mechanisms of cyclic and static fracture at elevated temperature are identical, and that the cyclic crack growth rates can be predicted on the basis of static fracture data. One of the techniques commonly used to derive cyclic crack growth rates solely on the basis of static load fracture data involves integration of the relationship in Eqn. (13) over the duration of the fatigue cycle such that... 

Materials science associated with fracture mechanics has mainly been confined to composite materials such as concrete, ceramics and metals. Much of the emphasis of the research has been on preventing fatigue and failure rather than designing for it to occur. The way a structure deforms and breaks under stress is crucial for properties such as flow and fracture behaviour, sensory perception of structure, water release and the mobility and release of active compounds. In the case of foods, the ability to break down and interact with the mouth surfaces provides texture and taste attributes. The crack propagation in a complex supramolecular structure is highly dependent on the continuous matrix, interfacial properties and defects and the heterogeneity of the structure. Previous structure-fracture work has dealt with cellular plant foods, and it has been demonstrated that the fracture path differs between fresh and boiled carrots due to cellular adhesion and cell wall strength as well as cell wall porosity and fluid transport (Thiel and Donald 1998 Stoke and Donald 2000 Lillford 2000). 

This book contains papers from the Fourth International Conference on Computational Methods and Experiments in Materials Characterisation which brought researchers who use computational methods, those who perform experiments, and of course those who do both, in all areas of materials characterisation, to discuss their recent results and ideas, in order to foster the multidisciplinary approach that has become necessary for the study of complex phenomena. The papers in the book cover the follow topics Advances in Composites Ceramics and Advanced Materials Alloys Cements Biomaterials Thin Films and Coatings Imaging and Image Analysis Thermal Analysis New Methods Surface Chemistry Nano Materials Damage Mechanics Fatigue and Fracture Innovative Computational Techniques Computational Models and Experiments Mechanical Characterisation and Testing. 

R. Ritchie and R. Daukardt, Cyclic Fatigue of Ceramics A Fracture Mechanism... 

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