scholarly journals Investigation of Indentation Fracture Toughness (KIC) and Weibull Parameters of 0.25Li2O.2SiO2-0.75BaO.2SiO2 Glass-Ceramic

2017 ◽  
Vol 62 (4) ◽  
pp. 1963-1968 ◽  
Author(s):  
B. Ertuğ ◽  
B. Nilgün Çetiner ◽  
H. Gökçe ◽  
Z. Engin Erkmen ◽  
M. Lütfi Öveçoğlu
Keyword(s):  
Fracture Toughness ◽  
Glass Ceramic ◽  
Scale Parameter ◽  
Indentation Test ◽  
Indentation Fracture ◽  
Indentation Fracture Toughness ◽  
Crystallization Heat ◽  
Probability Of Fracture ◽  
Measured Hardness ◽  
Distribution Equation

AbstractIn the present study, mechanical properties of 0.25Li2O.2SiO2-0.75BaO.2SiO2glass-ceramic were investigated. The trans-formations‘ temperatures were determined by DTA instrument. The optimum nucleation temperature was found to be 540°C. This suggested the crystallization temperatures as 675, 720 and 800°C. After carrying out crystallization heat treatments, Vickers indentation test was applied. In order to determine the indentation fracture toughness (KIC), crack half-length ‚c‘ of the samples was measured. To calculateKIC, Young’s modulus,Eand the measured hardness,Hvwere used. UsingKICand probability of fracture ‚P‘, ln ln[1/(1 −P)] – lnKICgraph was drawn based on the Weibull distribution equation. Consequently, Weibull modulus, ‚m‘ and scale parameter, ‚K0‘ were determined and compared with each other.

Fracture Toughness of HVOF Sprayed Cermet Coatings Measured by Vickers Indentation

2011 ◽  
Vol 465 ◽  
pp. 475-478 ◽  
Author(s):  
Šárka Houdková ◽  
František Zahálka ◽  
Michaela Kašparová
Keyword(s):  
Fracture Toughness ◽  
Indentation Test ◽  
Vickers Indentation ◽  
Indentation Fracture ◽  
Cermet Coatings ◽  
Indentation Fracture Toughness ◽  
Cracking Mode

In the paper, the indentation fracture toughness of the HVOF sprayed WC-12%Co coatings is determined by the Vickers indentation test in dependence on used load. The relations, proposed by Chicot, were used to calculate the value of KIc at condition of the Palmqvist, Intermediate and Radial-median cracking mode. The applicability of using different equations is discussed with respect to the size indentation effect of IFT.

Ball Indentation Technique to Estimate Fracture Toughness of High-Strength Rail Steels

2018 ◽  
Author(s):  
Feng Yu ◽  
P. Y. Ben Jar ◽  
Michael T. Hendry
Keyword(s):  
Fracture Toughness ◽  
Indentation Test ◽  
High Strength ◽  
Damage Parameter ◽  
Indentation Fracture ◽  
Indentation Technique ◽  
Contact Depth ◽  
Ball Indentation ◽  
Indentation Fracture Toughness ◽  
Critical Damage

In this work, the non-destructive ball indentation technique is applied to estimate fracture toughness for three types of high-strength rail steels based on continuum damage mechanics. Damage parameter, in terms of the deterioration of elastic modulus, is measured for three rail steels using the loading-unloading smooth tensile test, based on which a ductile damage model is calibrated to determine the critical damage parameter at the onset of fracture. Meanwhile, an instrumented ball indentation test is conducted on the three rail steels to generate damage as a function of contact depth under indentation compression. The critical damage parameter from the smooth specimen is then applied to the indentation test to determine the critical contact depth for calculating the indentation fracture toughness based on the concept of indentation energy to fracture. Results show that although the magnitude of the so-determined indentation fracture toughness is greater than that of the corresponding mode I critical stress intensity factor (KIc) measured using the pre-cracked single-edge-notched bend (SENB) specimen, the former can well predict the ranking order of the KIc values among the three rail steels.

scholarly journals Hardness and Indentation Fracture Toughness of Slip Cast Alumina and Alumina-Zirconia Ceramics

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 122 ◽  
Author(s):  
Irena Žmak ◽  
Danko Ćorić ◽  
Vilko Mandić ◽  
Lidija Ćurković
Keyword(s):  
Fracture Toughness ◽  
Slip Casting ◽  
Indentation Test ◽  
Brittleness Index ◽  
Vickers Indentation ◽  
Indentation Fracture ◽  
Concentrated Suspensions ◽  
Zro2 Content ◽  
Indentation Fracture Toughness ◽  
Crystallite Sizes

Alumina (Al2O3) and zirconia (ZrO2) have good overall properties and thus are widely used oxide technical ceramics. The biggest drawback of Al2O3 is its low fracture toughness. In contrast, ZrO2 is relatively tough, but is also much more expensive. In order to improve the alumina toughness, composite ceramics are being developed. Slip casting technology has economic advantages over the conventional hot isostatic pressure technology, but problems may arise when preparing stable highly-concentrated suspensions (slip) for filling the mold. The purpose of this study is to prepare aqueous suspensions using 70 wt. % α-Al2O3, with 0, 1, 5 and 10 wt. % of added t-ZrO2. Suspensions were electrosterically stabilized using the ammonium salt of polymethylacrylic acid, an alkali-free anionic polyelectrolyte dispersant. Also, magnesium oxide in form of magnesium aluminate spinel (MgAl2O4) was used to inhibit the abnormal alumina grain growth during the sintering process. Minimum viscosities were used as stability estimators, where an increase in ZrO2 content required adding more dispersant. After sintering, the Vickers indentation test was used to determine the hardness and the indentation fracture toughness from the measurement of the crack length. Also, the brittleness index (Bi, μm−1/2) was calculated from values of Vickers hardness and the Vickers indentation fracture toughness. It was found that with increasing ZrO2 content the fracture toughness increased, while the hardness as well as the brittleness index decreased. Zirconia loading reduces the crystallite sizes of alumina, as confirmed by the X-ray diffraction analysis. SEM/EDS analysis showed that ZrO2 grains are distributed in the Al2O3 matrix, forming some agglomerates of ZrO2 and some pores, with ZrO2 having a smaller grain size than Al2O3.

A Transparent and Tough β-Si3N4 Ceramic with a Whiskery Microstructure

2015 ◽  
Vol 655 ◽  
pp. 1-5
Author(s):  
Peng Xi Li ◽  
Hong Qiang Wang ◽  
Liu Cheng Gui ◽  
Jun Li ◽  
Hai Long Zhang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Amorphous Phase ◽  
Hot Pressing ◽  
High Density ◽  
Indentation Fracture ◽  
Indentation Fracture Toughness ◽  
Resultant Material

The transparent β-Si3N4ceramic with a whisker-like microstructure was prepared by hot-pressing at 2000 °C for 26 h, with MgSiN2as an additive. The resultant material achieves the maximum transmittance of 70 % at the wavelength of about 2.5 μm and the transmittance value keeps higher than 60 % in the range of 700-4500 nm wavelength, which is attributed to the very small amount of the intergranular amorphous phase along with high density. The present transparent β-Si3N4ceramic exhibits an indentation fracture toughness of 7.2±0.3 MPa m1/2.

Pulsed Electric Current Sintered Cr2O3-rGO Composites

2016 ◽  
Vol 721 ◽  
pp. 419-424
Author(s):  
M. Erkin Cura ◽  
Vivek Kumar Singh ◽  
Panu Viitaharju ◽  
Joonas Lehtonen ◽  
Simo Pekka Hannula
Keyword(s):  
Fracture Toughness ◽  
Graphene Oxide ◽  
Electric Current ◽  
Chromium Oxide ◽  
High Hardness ◽  
High Wear Resistance ◽  
Carbide Formation ◽  
Indentation Fracture ◽  
Pulsed Electric Current ◽  
Indentation Fracture Toughness

Chromium oxide is a promising material for applications where excellent corrosion resistance, high hardness, and high wear resistance are needed. However, its use is limited because of low fracture toughness. Improvement of fracture toughness of chromium oxide while maintaining its afore mentioned key properties is therefore of high interest. In this communication we study the possibility of increasing the toughness of pulsed electric current sintered (PECS) chromium oxide by the addition of graphene oxide (GO). The indentation fracture toughness was improved markedly with the addition of graphene oxide. Materials prepared by direct chemical homogenization had better fracture toughness. In composites with 10 vol.% GO piling of thin graphene oxide layers resulted in the formation of graphite layers between Cr2O3 and in carbide formation, which were observed to be the main reasons for the degradation of the mechanical properties. The distribution of graphene oxide was more homogeneous, when the GO amount was 0.1 vol.% and the formation of graphitic layers were avoided due to lesser amount of GO as well as ultrasonic treatment following the ball milling.

Structure and Properties of Single Crystal Al2O3 Implanted with Chromium and Zirconium

1981 ◽  
Vol 7 ◽  
Author(s):  
C. J. Mchargue ◽  
H. Naramoto ◽  
B. R. Appleton ◽  
C. W. White ◽  
J. M. Williams
Keyword(s):  
Fracture Toughness ◽  
Single Crystal ◽  
Single Crystals ◽  
Solid Solutions ◽  
Rutherford Backscattering ◽  
Structure And Properties ◽  
Indentation Fracture ◽  
Surface Layers ◽  
Indentation Fracture Toughness

ABSTRACTSingle crystals of Al2O3 were implanted with chromium and zirconium to fluences of 1 × 1016 to 1 × 1017 ions cm−2. Rutherford backscattering-channeling studies showed the surface layers to be damaged but crystalline with the implanted ions randomly distributed. The microhardness and indentation fracture toughness were higher for the random solutions than for conventionally formed solid solutions. Changes in structure and properties caused by annealing in air at temperatures up to 1800°C were studied.

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