Fracture toughness measurements of ceramics by V notch technique

Araki, Hideo; Watanabe, Tadao; Sakaida, Yoshihisa; Nakagawa, Heisaburo

doi:10.1016/0272-8842(92)90056-j

Cited by 32 publications

(22 citation statements)

References 17 publications

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“…For a crack in an infinite plate under mode I loading, the exact solution of the stress on the r-axis (ahead of the crack plane) is expressed as 14) y…”

Section: Criteria For Crack Extensionmentioning

confidence: 99%

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

2006

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In order to improve the fracture toughness of inherently brittle ceramics, a new material design concept must be developed. One suitable concept involves the use of dislocation activities. Intra-type ceramic-based nanocomposites use dislocation activities to enhance strength and fracture toughness. The dislocations are generated by residual stresses induced during sintering process around the second-phase nanoparticles dispersed within the matrix grains. In this paper, first, we proposed an indirect technique for estimating a critical frontal process zone (CFPZ) size for ceramics and clarified the relation between the strength, fracture toughness, and CFPZ size. The fracture toughness of ceramics is closely related to the CFPZ size because ceramics with larger CFPZ size consume higher fracture energy during crack extension and consequently have higher fracture toughness. Second, we fabricated toughened alumina-nickel nanocomposites using a soaking method to construct an intra-type nanostructure, and found that the appropriate annealing conditions after sintering could achieve toughened nanocomposites. Finally, we discussed the relation between the experimentally obtained fracture toughness and the CFPZ size of monolithic alumina, as-sintered nanocomposites, and annealed nanocomposites. The results revealed that nanocomposites showed the largest CFPZ size and the highest fracture toughness after appropriate annealing: the sessile dislocations ahead of a crack tip in a nanocomposite are thought to serve as stress concentration, create many nanocracks in the CFPZ, and expand the CFPZ size.

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“…For a crack in an infinite plate under mode I loading, the exact solution of the stress on the r-axis (ahead of the crack plane) is expressed as 14) y…”

Section: Criteria For Crack Extensionmentioning

confidence: 99%

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

2006

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“…The method applied in this study is the single edge v-notched beam (SEVNB) method, as pioneered by Awaji et al [29]. This method is a slight modification of the ASTM standard method E-399 in which the fatigue pre-crack at the end of the machined notch is replaced with a sharp notch.…”

Section: Single Edge V-notched Beam Fracture Toughness Testingmentioning

confidence: 99%

“…The fracture toughness of the cermet was evaluated for both the as-received and post-HIP condition utilizing the equation developed by Wakai et al [29] :…”

Section: Single Edge V-notched Beam Fracture Toughness Testingmentioning

confidence: 99%

Characterization of a Ti(Mo)C-Ni Cermet for Use in Impact Resistant Sandwich Panels

Keene¹

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The deflection of edge-clamped plates during out of plane impulsive loading is proportional to a merit index given by the square root of the ratio of the plate material strength to its density [1]. Even smaller deflections can be achieved if sandwich panels with cellular cores can be made from these high specific strength materials. Ti(Mo)C-Ni based cermets have been identified as a potentially superior material for this application since their compressive strength is typically 2-3 GPa and their density is in the 5,500 kg/m 3 range. The merit index of this cermet exceeds that of all known metallic systems. Although the toughness of cermets generally exceeds that of ceramics, they have low fracture toughness relative to many metals and this will inhibit their suitability for some applications.A comprehensive characterization of the mechanical properties of Ti(Mo)C-Ni cermets has been conducted in order to determine if it is a viable candidate for use in truss core sandwich panels. Additionally, the lack of well-established fabrication and joining techniques needed to fabricate sandwich panels is also a concern. The feasibility of using a transient liquid phase bonding (brazing) technique to fabricate a cellular structure was also therefore investigated.The cermet system investigated here is found to have a density of 5,520 kg/m 3 in its asreceived condition. Using image analysis and quantitative x-ray diffraction-based phase identification, it was determined to consist of approximately 83 vol % TiC ceramic with 15 vol% of the nickel binder, and an average porosity of 1.6 vol%. Chemical analysis via inductively coupled optical emission and energy dispersive x-ray spectroscopy indicate the ceramic phase has a metal composition of 88% Ti, 11% Mo, and <1% Ni. Similar analysis of the binder gives a composition of 94% Ni, 5% Ti, and <1% Mo, respectively. The elastic modulus of the system ii was determined to be 380 GPa via pulse-echo ultrasonic technique. The cermets measured compressive strength was 2.7 GPa but its bending strength was only 520 MPa, which is likely reconciled in terms of the characteristic flaws within the material.The density and elastic moduli are well estimated by a rule of mixtures of the ceramic hard phase and the metallic binder properties. A computation of the theoretical density of the individual phases permits a calculation of the aggregate porosity level from the independently measured phase fractions. The elastic modulus of the cermet is nearly equivalent to that upper bound prediction computed based upon the moduli of pure TiC and Ni phases, but this may be a consequence of force chain formation.The as-received cermet was discovered to undergo cracking during electro-discharge machining (EDM) of truss core shapes. X-ray diffraction measurements showed that a significant level of residual stress of 165 ± 15 MPa was present in the TiC phase. Stress-relief annealing at 900˚ C with a subsequent cooling rate of 15˚ C/min was observed to relieve the stress to a value lower than the exper...

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“…Os principais métodos existentes atualmente para a determinação de K Ic são listados a seguir: IF (Indentation Fracture -fratura por indentação) (72)(73)(74)(75)(76)(77)(78)(79)(80)(81)(82)(83)(84)(85)(86) , IS (Indentation Strength -resistência à indentação) (74,78,79,83,87) , CNB (Chevron Notch Beam -barra entalhada Chevron) (78,79,84,(87)(88)(89)(90)(91) , SCF (Surface Crack in Flexure -superfície da trinca em flexão) (78,79,83,84,88,89,91) , SEPB (Single Edge…”

Section: Tenacidade à Fraturaunclassified

“…Observa-se que, logo no início de desenvolvimento do método SEVNB, o entalhe era produzido com um disco de diamante de formato em V mais agudo, mantendo a singularidade de raiz quadrada na ponta quando o ângulo é inferior que 30° (99) .…”

Section: Tenacidade à Fraturaunclassified

Sinterização e caracterização mecânica e microestrutural de cerâmicas de SiC aditivadas com misturas de AIN/Dy2O3 e AIN/Yb2O3

Santos¹

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Fracture toughness measurements of ceramics by V notch technique

Cited by 32 publications

References 17 publications

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

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

Characterization of a Ti(Mo)C-Ni Cermet for Use in Impact Resistant Sandwich Panels

Sinterização e caracterização mecânica e microestrutural de cerâmicas de SiC aditivadas com misturas de AIN/Dy2O3 e AIN/Yb2O3

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