scholarly journals Fracture Toughness and Frontal Process Zone Size of Ceramics

2004 ◽  
Vol 53 (9) ◽  
pp. 1012-1018 ◽  
Author(s):  
Hideo AWAJI ◽  
Seong Min CHOI ◽  
Chun Hong CHEN ◽  
Nobuyuki KISHI
Keyword(s):  
Fracture Toughness ◽  
Process Zone ◽  
Zone Size ◽  
Frontal Process

Novel Estimation of Critical Frontal Process Zone of Ceramics by a Single-Edge V-Notched-Beam Technique

2007 ◽  
Vol 280-283 ◽  
pp. 1745-1750
Author(s):  
Chun Hong Chen ◽  
Hideo Awaji
Keyword(s):  
Fracture Toughness ◽  
Flexural Strength ◽  
Critical Size ◽  
Process Zone ◽  
Porous Alumina ◽  
Local Stress ◽  
Zone Size ◽  
Single Edge ◽  
Frontal Process ◽  
Notch Tip

A novel estimation for the critical size of the frontal process zone of ceramics is proposed using a single-edge V-notched beam (SEVNB) technique. A three-point flexure test is carried out on aluminum titanate ceramics containing a sharp V-shaped notch with different depth. An exact solution of the critical local stress is analyzed at a critical distance from the notch tip. The critical frontal process zone size is determined as the distance between the notch tip and the point where the critical local stress equals the flexural strength of specimens without notches, based on the local fracture criterion and the Griffith-Irwin criterion. The critical size of the frontal process zone, the fracture toughness and the flexural strength were also estimated for several materials, such as, alumina, porous alumina, and alumina-based nanocomposites. The relationship between these mechanical properties indicated that there was an almost linear relationship between the fracture toughness and the resultant of strength and square root of the critical frontal process zone size, and that both of them must be increased to improve the fracture toughness of ceramics.

scholarly journals Relation between Strength, Fracture Toughness, and Critical Frontal Process Zone Size in Ceramics

2006 ◽  
Vol 47 (6) ◽  
pp. 1532-1539 ◽  
Author(s):  
Hideo Awaji ◽  
Takuya Matsunaga ◽  
Seong-Min Choi
Keyword(s):  
Fracture Toughness ◽  
Process Zone ◽  
Zone Size ◽  
Frontal Process

Critical Frontal Process Zone Size and R-Curve Behavior of Porous Ceramics

2006 ◽  
Vol 317-318 ◽  
pp. 281-284 ◽  
Author(s):  
Hideo Awaji ◽  
Chun Hong Chen ◽  
Nobuyuki Kishi
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Silicon Carbide ◽  
Porous Silicon ◽  
Crack Extension ◽  
Process Zone ◽  
Porous Ceramics ◽  
Zone Size ◽  
Frontal Process ◽  
Materials Used

Although porous ceramics are materials with high potential for helping conserve the environment, the characteristics of pore-related mechanical properties have not yet been examined sufficiently. The R-curve behavior of porous ceramics was estimated using the crack stabilizer technique developed by Nojima et al. Also, the critical frontal process zone (CFPZ) size for porous ceramics was estimated from the strength and fracture toughness of the materials used. The results revealed that the R-curve behavior was almost flat in porous ceramics, in contrast with a steeply rising R-curve behavior for porous silicon carbide observed previously, and that the CFPZ size of porous ceramics was larger than that of dense ceramics. A schematic explanation for the crack extension in porous materials was presented to discuss the R-curve behavior of porous ceramics.

Nanocomposites – Toughened Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 2242-2246
Author(s):  
Hideo Awaji ◽  
Takuya Matsunaga ◽  
Seong Min Choi
Keyword(s):  
Fracture Toughness ◽  
Process Zone ◽  
Nano Particles ◽  
Nano Structure ◽  
Metallic Particles ◽  
Dispersed Particles ◽  
The Matrix ◽  
Frontal Process ◽  
Improve Fracture Toughness ◽  
Pulse Electric

In order to improve fracture toughness of ceramics, an intrinsically small frontal process zone (FPZ) size must be expanded. An intra-type nano-structure, where nano-particles are embedded within matrix grains, yields dislocations around the dispersed particles due to residual stresses. These dislocations become sessile dislocations at room temperature, operate as origins of small stress concentration in the matrix, and create nano-cracks in the FPZ. To produce the intra-type nano-structure, we developed a soaking method. This method makes it possible to produce nano-sized metallic particles dispersed within ceramic powders. In this research, alumina-nickel nanocomposite powder was obtained using the soaking method. The powder mixed with α-alumina as a seed was sintered using a pulse electric current sintering technique. The sintered nanocomposites are then annealed to disperse dislocations around the nanoparticles into alumina grains. Results showed that the maximum fracture toughness was 7.6 MPam1/2, which was two times higher than that of alumina.

scholarly journals Toughening mechanism and frontal process zone size of ceramics

2009 ◽  
Vol 117 (1365) ◽  
pp. 623-629 ◽  
Author(s):  
Hideo AWAJI ◽  
Yoshitaka NISHIMURA ◽  
Seong-Min CHOI ◽  
Yoshikazu TAKAHASHI ◽  
Tomoaki GOTO ◽  
...  
Keyword(s):  
Process Zone ◽  
Zone Size ◽  
Toughening Mechanism ◽  
Frontal Process
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