Micro-indentation method for evaluation of fracture toughness and thermal residual stresses of SiC coating on carbon/carbon composite

2003 ◽  
Vol 12 (2-3) ◽  
pp. 155-169 ◽  
Author(s):  
Hiroshi Hatta ◽  
Masayuki Mizoguchi ◽  
Masashi Koyama ◽  
Yuko Furukawa ◽  
Toshio Sugibayashi
Keyword(s):  
Fracture Toughness ◽  
Residual Stresses ◽  
Carbon Composite ◽  
Indentation Method ◽  
Thermal Residual Stresses ◽  
Micro Indentation

Measuring Residual Stress with the Indentation Method in Struc­tural Ceramics

2005 ◽  
Vol 297-300 ◽  
pp. 515-520
Author(s):  
Tarou Tokuda ◽  
Rong Gang Wang ◽  
Mitsuo Kido ◽  
Gonojo Katayama
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Phase Transformation ◽  
Residual Stresses ◽  
Treatment Method ◽  
Indentation Load ◽  
X Rays ◽  
Ray Method ◽  
Indentation Method ◽  
X Ray

This study deals with the indentation method of measuring residual stress in structural ceramics. First we investigate the appropriate pretreatment for measuring fracture toughness (basis value, KC) while avoiding any influence from residual stress, which is important when estimating residual stress using the indentation method. Based on the fracture toughness value, the residual stresses in Al2O3, Si3N4 and ZrO2 ceramics are estimated using the indentation method. Phase transformation is a problem when estimating residual stress using the indentation method with ZrO2 ceramics. Residual stresses in Al2O3 and Si3N4 can be largely eliminated by annealing the specimen after hand grinding. Consequently, it is thought that this treatment method is effective for determining the basis value KC. The estimated residual stress values in Al2O3 and Si3N4 obtained by the indentation method at 98 N corresponded closely to the values obtained wih X-rays. The residual stress value obtained by the indentation method for ZrO2 was close to the value obtained through the X-ray method, when the indentation load was 294 N. When estimating the residual stress in ZrO2 using the indentation method, the influence of the phase transformation caused by the indentation is added onto the original residual stress, when the indentation is small. The influence becomes smaller when the indentation load is large. If the applied indentation load is between 294 N and 490 N, the indentation method is effective for estimating the residual stresses in Al2O3, Si3N4 and ZrO2 ceramics.

HVOF Coating of Metallic Surfaces Using Different Powders: Fracture Toughness Measurement of Resulting Surfaces

2012 ◽  
Vol 445 ◽  
pp. 621-626 ◽  
Author(s):  
Y.A. Al-Shehri ◽  
M.S.J. Hashmi ◽  
Bekir Sami Yilbas
Keyword(s):  
Fracture Toughness ◽  
Microstructural Analysis ◽  
Metallic Surfaces ◽  
Indentation Method ◽  
Hvof Coatings ◽  
Fracture Toughness Measurement ◽  
Coated Surface ◽  
Coating Layers ◽  
Micro Indentation ◽  
Toughness Measurement

In the present study, two layer HVOF coatings of carbon steel is carried out. The microstructural changes in the coating layers and fracture toughness of the coated surface are examined. The micro indentation method is incorporated for the fracture toughness measurements, while optical and scanning electron microscopy are used for the microstructural analysis. It is found that the fracture toughness of the coating surface produced by the tungsten carbide blended powders is less than that of the coating produced by corrosion resistance powders. Key words: HVOF, Diamalloy 2002, Diamalloy 4010, Fracture toughness.

Modeling of electromechanical response and fracture resistance of multilayer piezoelectric energy harvester with residual stresses

2020 ◽  
Vol 31 (19) ◽  
pp. 2261-2287
Author(s):  
Zdeněk Machů ◽  
Oldřich Ševeček ◽  
Zdeněk Hadaš ◽  
Michal Kotoul
Keyword(s):  
Fracture Toughness ◽  
Residual Stresses ◽  
Fracture Resistance ◽  
Energy Harvester ◽  
Beam Theory ◽  
Vibration Energy Harvester ◽  
Layered Architecture ◽  
Thermal Residual Stresses ◽  
Apparent Fracture Toughness ◽  
Piezoelectric Energy

The article focuses on a modeling and subsequent optimization of a novel layered architecture of the vibration piezoceramic energy harvester composed of ZrO2/Al2O3/BaTiO3 layers and containing thermal residual stresses. The developed analytical/numerical model allows to determine the complete electromechanical response and the apparent fracture toughness of the multilayer vibration energy harvester, upon consideration of thermal residual stresses and time-harmonic kinematic excitation. The derived model uses the Euler–Bernoulli beam theory, Hamilton’s variational principle, and a classical laminate theory to determine the first natural frequency, steady-state electromechanical response of the beam upon harmonic vibrations, and also the mechanical stresses within particular layers of the harvester. The laminate apparent fracture toughness is computed by means of the weight function approach. A crucial point is the further optimization of the layered architecture from both the electromechanical response and the fracture resistance point of view. Maximal allowable excitation acceleration of the harvester upon which the piezoelectric layer will not fail is determined. It makes possible to better use the harvester’s capabilities in a given application and simultaneously guarantee its safe operation. Outputs of the derived analytical model were validated with finite element method simulations and available experimental results, and a good agreement between all approaches was obtained.

Laser Nitriding of Titanium Alloy and Fracture Toughness Measurement of Resulting Surface

2012 ◽  
Vol 445 ◽  
pp. 615-620 ◽  
Author(s):  
O. Al-Mana ◽  
M.S.J. Hashmi ◽  
Bekir Sami Yilbas
Keyword(s):  
Fracture Toughness ◽  
Titanium Alloy ◽  
Surface Region ◽  
Alloy Surface ◽  
Indentation Method ◽  
Laser Nitriding ◽  
Fracture Toughness Measurement ◽  
High Cooling Rates ◽  
Micro Indentation ◽  
Toughness Measurement

In the present study laser nitriding of titanium alloy surface is carried out and fracture toughness of the resulting surface is measured using the micro-indentation method. The fracture toughness is then related to the microstructure of the laser treated surface. It is found that laser gas assisted nitriding lowers the fracture toughness of the surface due to the micro-stress formed at the surface region during the high cooling rates.

Titanium Effect on Microstructure and Fracture toughness of Al2O3-BASED Composites

2011 ◽  
Vol 691 ◽  
pp. 32-36
Author(s):  
José G. Miranda-Hernández ◽  
Elizabeth Refugio-García ◽  
Eduardo Térres-Rojas ◽  
Enrique Rocha-Rangel
Keyword(s):  
Electron Microscopy ◽  
Fracture Toughness ◽  
Scanning Electron Microscopy ◽  
Fine Particles ◽  
Ceramic Matrix ◽  
High Energy ◽  
Titanium Content ◽  
Indentation Method ◽  
Sintered Temperature ◽  
Scanning Electron

The effect of different titanium additions (0.5, 1, 2, 3 and 10 vol. %), milling intensity (4 and 8 h) and sintered temperature (1500 and 1600 °C) on microstructure and fracture toughness of Al2O3-based composites was analyzed in this study. After high energy milling of a titanium and Al2O3mixtures, powder mixture presents fine distribution and good homogenization between ceramic and metal. After milling powders during 8 h they were obtained very fine particles with 200 nm average sizes. Microstructures of the sintered bodies were analyzed with a scanning electron microscopy, where it was observed that the microstructure presents the formation of a small and fine metallic net inside the ceramic matrix. From fracture toughness measurements realized by the fracture indentation method, it had that when titanium content in the composite increases, fracture toughness is enhanced until 83% with respect to the fracture toughness of pure Al2O3. This behavior is due to the formation of metallic bridges by titanium in the Al2O3matrix.

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