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Bending Tests

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Yichun Zhou – One of the best experts on this subject based on the ideXlab platform.

  • fracture characteristics of thermal barrier coatings after tensile and Bending Tests
    Surface & Coatings Technology, 2002
    Co-Authors: Yichun Zhou, Tetsuro Tonomori, A Yoshida, Lihui Liu, G Bignall, Toshiyuki Hashida

    Abstract:

    Uniaxial tension and four-point Bending Tests were conducted on two-layer (non-functionally graded material) plasma-sprayed rectangular specimens, boasting a new, functionally graded material (FGM) layer. The top coat layer was composed of stabilized yttria-zirconia (YSZ), and the bond coat layer was NiCrAlY. The FGM was composed of five layers: 100% YSZ; 80% YSZ+20% NiCrAlY; 60% YSZ+40% NiCrAlY; 40% YSZ+60% NiCrAlY; and 20% YSZ+80% NiCrAlY. Fracture in the thermal barrier coating (TBC) system was examined by scanning electron microscopy (SEM), which showed that vertical multiple cracking first occurred in the top coat, followed by propagation of interface cracking between the top and bond coats. Spallation of non-FGM coatings occurred in tensile/Bending experiments, but not for the FGM-coated specimens, with only localized delamination observed along the interface between FGM layers and the substrate. For specimens prepared with a gun–substrate distance of approximately 120 mm and gun operating power of approximately 32.5 kW, the interface fracture toughness, evaluated by a shear lag model for the uniaxial tensile test, was 0.94 and 0.67 MPa m1/2 for type-A and -B coatings, respectively. Here, types A and B correspond to an average roughness of the bond coat surface of 12.8 μm and 6.8 μm, respectively. The interface fracture toughness evaluated by the Suo–Hutchinson model was 1.05–1.27 and 1.0–1.17 MPa m1/2 for type-A and -B coatings, respectively. The results are very close to data obtained by the blister test method. For specimens prepared with a gun–substrate distance of 125–130 mm and gun operating power of approximately 38.5 kW, the interface fracture toughness, evaluated by the Suo–Hutchinson model for four-point Bending, was 4.26–7.21 MPa m1/2.

Marco Tatullo – One of the best experts on this subject based on the ideXlab platform.

  • Three-Point Bending Tests of Zirconia Core/Veneer Ceramics for Dental Restorations
    International Journal of Dentistry, 2013
    Co-Authors: Massimo Marrelli, Carmine Maletta, Francesco Inchingolo, Marco Alfano, Marco Tatullo

    Abstract:

    Introduction. The mechanical strength and the surface hardness of commercially available yttrium-doped zirconia were investigated. Furthermore, a comparative study of eight different ceramic veneers, to be used for the production of two-layered all-ceramic restorative systems, was carried out. Materials and Methods. Four types of zirconia specimens were analyzed, according to a standard ISO procedure (ISO 6872). Besides, two-layered zirconia-veneer specimens were prepared for three-point Bending Tests. Results. A strong effect of the surface roughness on the mechanical strength of zirconia specimens was observed. Finally, a comparative study of eight commercially available veneering ceramics shows different modes of failure between the selected veneers. Conclusion. The results indicate that close attention should be paid to the preparation of zirconia-based crowns and bridges by CAD/CAM process, because surface roughness has an important effect on the mechanical strength of the material. Finally, the results of the mechanical Tests on two-layered specimens represent an important support to the choice of the veneering ceramic.

  • three point Bending Tests of zirconia core veneer ceramics for dental restorations
    International Journal of Dentistry, 2013
    Co-Authors: Massimo Marrelli, Carmine Maletta, Francesco Inchingolo, Marco Alfano, Marco Tatullo

    Abstract:

    Introduction. The mechanical strength and the surface hardness of commercially available yttrium-doped zirconia were investigated. Furthermore, a comparative study of eight different ceramic veneers, to be used for the production of two-layered all-ceramic restorative systems, was carried out. Materials and Methods. Four types of zirconia specimens were analyzed, according to a standard ISO procedure (ISO 6872). Besides, two-layered zirconia-veneer specimens were prepared for three-point Bending Tests. Results. A strong effect of the surface roughness on the mechanical strength of zirconia specimens was observed. Finally, a comparative study of eight commercially available veneering ceramics shows different modes of failure between the selected veneers. Conclusion. The results indicate that close attention should be paid to the preparation of zirconia-based crowns and bridges by CAD/CAM process, because surface roughness has an important effect on the mechanical strength of the material. Finally, the results of the mechanical Tests on two-layered specimens represent an important support to the choice of the veneering ceramic.

Toshiyuki Hashida – One of the best experts on this subject based on the ideXlab platform.

  • fracture characteristics of thermal barrier coatings after tensile and Bending Tests
    Surface & Coatings Technology, 2002
    Co-Authors: Yichun Zhou, Tetsuro Tonomori, A Yoshida, Lihui Liu, G Bignall, Toshiyuki Hashida

    Abstract:

    Uniaxial tension and four-point Bending Tests were conducted on two-layer (non-functionally graded material) plasma-sprayed rectangular specimens, boasting a new, functionally graded material (FGM) layer. The top coat layer was composed of stabilized yttria-zirconia (YSZ), and the bond coat layer was NiCrAlY. The FGM was composed of five layers: 100% YSZ; 80% YSZ+20% NiCrAlY; 60% YSZ+40% NiCrAlY; 40% YSZ+60% NiCrAlY; and 20% YSZ+80% NiCrAlY. Fracture in the thermal barrier coating (TBC) system was examined by scanning electron microscopy (SEM), which showed that vertical multiple cracking first occurred in the top coat, followed by propagation of interface cracking between the top and bond coats. Spallation of non-FGM coatings occurred in tensile/Bending experiments, but not for the FGM-coated specimens, with only localized delamination observed along the interface between FGM layers and the substrate. For specimens prepared with a gun–substrate distance of approximately 120 mm and gun operating power of approximately 32.5 kW, the interface fracture toughness, evaluated by a shear lag model for the uniaxial tensile test, was 0.94 and 0.67 MPa m1/2 for type-A and -B coatings, respectively. Here, types A and B correspond to an average roughness of the bond coat surface of 12.8 μm and 6.8 μm, respectively. The interface fracture toughness evaluated by the Suo–Hutchinson model was 1.05–1.27 and 1.0–1.17 MPa m1/2 for type-A and -B coatings, respectively. The results are very close to data obtained by the blister test method. For specimens prepared with a gun–substrate distance of 125–130 mm and gun operating power of approximately 38.5 kW, the interface fracture toughness, evaluated by the Suo–Hutchinson model for four-point Bending, was 4.26–7.21 MPa m1/2.