scholarly journals Improvement of the Contact Strength of Al2O3/SiC by a Combination of Shot Peening and Crack-Healing

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Tomoya Oki ◽  
Hiroki Yamamoto ◽  
Toshio Osada ◽  
Koji Takahashi
Keyword(s):  
Fracture Toughness ◽  
Shot Peening ◽  
Zirconium Oxide ◽  
Surface Cracks ◽  
Contact Strength ◽  
Crack Healing ◽  
Composite Ceramics ◽  
Apparent Fracture Toughness ◽  
Heat Treated ◽  
High Crack

Al2O3/SiC composite ceramics with high crack-healing ability were subjected to shot peening (SP) using zirconium oxide shots with several peening pressures and shot diameters. Specimens subjected to SP were heat-treated in air to heal the surface cracks induced by SP. The residual stress, the apparent fracture toughness, and the Weibull distribution of the contact strength were investigated, revealing that the combination of SP and crack-healing is effective for increasing the contact strength and decreasing the scatter of the contact strength of Al2O3/SiC.

Improvement of Contact Strength of Si3N4/SiC by Combination of Shot Peening and Self-Crack Healing

2011 ◽  
Author(s):  
Koji Takahashi
Keyword(s):  
Weibull Distribution ◽  
Shot Peening ◽  
Surface Cracks ◽  
Contact Strength ◽  
Crack Healing ◽  
Composite Ceramics ◽  
Combination Effects ◽  
Heat Treated ◽  
Indentation Tests ◽  
High Crack

In this study the combination effects of shot peening (SP) and crack-healing on the contact strength of ceramics were examined. Si3N4/SiC composite ceramics with high crack-healing ability were used and the specimens were subjected to shot peening with several peening pressures and shot diameters. Then, some specimens subjected to SP were heat-treated in air to heal surface cracks introduced by shot peening. Sphere indentation tests were carried out on the specimens and investigated the Weibull distribution of the contact strength. As a result, it is found that the combination of shot peening and crack-healing is effective to increase contact strength and decrease the scatter of the contact strength.

Effect of SiC Shape on The Crack-Healing Mechanism of Alumina/SiC Composite

2005 ◽  
Vol 888 ◽  
Author(s):  
Wataru Nakao ◽  
Toshio Osada ◽  
Kazuya Yamane ◽  
Masahiro Yokouchi ◽  
Koji Takahashi ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Crack Size ◽  
Surface Cracks ◽  
Crack Healing ◽  
Weak Point ◽  
Strength Recovery ◽  
Sic Particles ◽  
Sic Whiskers ◽  
Monolithic Alumina ◽  
Surface Length

ABSTRACTCrack-healing of structural ceramics is a most valuable technique to overcome their weak point such as surface cracks. Crack-healing ability appeared by admixing SiC to ceramics, because this function is to use the oxidation of SiC. Endowment of crack-healing ability as well as improvement in fracture toughness was expected to be achieved by compositing SiC whiskers. For this purpose, alumina / 30 vol% SiC whiskers and alumina/ 20vol% SiC whiskers/ 10 vol% SiC particles multi-composites were developed. Crack-healing ability and fracture toughness of these composites were investigated. Alumina/ 20 vol% SiC whiskers/ 10 vol% SiC particles multi-composite and alumina/ 30vol% SiC whiskers composite were found to have 1.43 times and 1.65 times higher fracture toughness than monolithic alumina, respectively. From the results of the strength recovery by crack-healing, alumina/ 20 vol% SiC whiskers/ 10 vol% SiC particles multi-composite and alumina / 30vol% SiC whiskers composite were found to be able to heal the pre-crack below 0.250 μm and 0.200 μm in surface length, respectively. In spite of the same SiC content, SiC particles and SiC whiskers multi-compositing enlarged the limit crack size to be able to crack-heal. On the other hand, increasing SiC whiskers content enhanced strength recovery of the specimen with the large crack above limit crack-size.

Threshold Stress for Crack-Healing of Silicon Nitride Ceramics

2004 ◽  
Author(s):  
Koji Takahashi ◽  
Kotoji Ando ◽  
Shoko Yoshida ◽  
Shinji Saito
Keyword(s):  
Fatigue Strength ◽  
Threshold Stress ◽  
Bending Strength ◽  
Surface Cracks ◽  
Bending Stress ◽  
Crack Healing ◽  
Composite Ceramics ◽  
Nitride Ceramics ◽  
Cracked Specimens ◽  
Surface Length

Si3N4/SiC composite ceramics were hot-pressed in order to investigate the crack-healing behavior under stress. Semi-elliptical surface cracks of 100 μm in surface length were introduced on each specimen. The pre-cracked specimens were crack-healed under cyclic or constant bending stress of 5 Hz at healing temperatures of 1000° and 1200°C and the resultant bending strength and fatigue strength were studied. The threshold stress for crack-healing, below which the pre-cracked specimens recovered their bending strength, was investigated. The mechanisms of crack-healing in Si3N4/SiC under stress were also discussed.

scholarly journals Effect of the different debonding strength of metal and ceramic brackets on the degree of enamel microcrack healing

2021 ◽  
Vol 26 (3) ◽  
Author(s):  
Piyaphong NIMPLOD ◽  
Ratchawan TANSALARAK ◽  
Tanapon SORNSUWAN
Keyword(s):  
Fracture Toughness ◽  
Testing Machine ◽  
Crack Healing ◽  
Apparent Fracture Toughness ◽  
Adhesive Remnant Index ◽  
Significant Difference ◽  
Final Measurement ◽  
Ceramic Brackets ◽  
Group 5 ◽  
Corner Cracks

ABSTRACT Objective: This study aims to determine shear debonding strength of metal and ceramic brackets, and the degree of enamel crack healing. Material and Methods: Extracted human maxillary premolars were flattened on the buccal surface, and randomly separated into five groups (n = 15). In control groups (groups 1 and 2), metal and ceramic brackets were bonded on flat polished enamel, while in experimental groups (groups 3 and 4), metal and ceramic brackets were bonded on the surface with boundary where corner cracks were created. Additionally, fifteen specimens (group 5) were also prepared for an indentation procedure with no bracket installation. The degree of crack healing was measured. All brackets were detached with a universal testing machine, and the adhesive remnant index (ARI) was also identified. Healing degree and apparent fracture toughness were then calculated. Results: Between groups with similar bracket types, there was no statistically significant difference in debonding strength. Regarding bracket types, ceramic brackets provided significantly higher debonding strength than metal brackets. There was a significant difference in ARI scores between metal and ceramic brackets. The corner cracks showed signs of healing in both horizontal and vertical directions. No statistically significant difference in the healing rates among the groups was found and the apparent fracture toughness increased from the initial to the final measurement. Conclusions: Within the limitations of this study, even though ceramic brackets required significantly higher debonding force compared to metal brackets, debonding stress was limited to the bonding site and did not affect the surrounding cracks on enamel.

scholarly journals Improvement in Contact Strength of Si3N4/SiC Composite by Crack Healing

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Koji Takahashi ◽  
Keita Takahashi ◽  
Kotoji Ando
Keyword(s):  
Acoustic Emission ◽  
Cutting Tool ◽  
Indentation Test ◽  
Machining Process ◽  
Surface Cracks ◽  
Contact Strength ◽  
Crack Healing ◽  
Machining Processes ◽  
Contact Loading ◽  
Ceramic Components

Ceramics have been used as bearing and cutting tool components, which are subjected to contact loading during their operation. The presence of surface cracks on these components decreases their contact strength. Thus, the reliability of ceramic components can be increased by improving their contact strength through crack healing. In the present study, the effects of crack healing on the contact strength of a silicon carbide-(SiC-) reinforced silicon nitride (Si3N4) composite subjected to various machining processes were investigated. The contact strength of this composite was evaluated using a sphere indentation test in which acoustic emission was used. The results showed that the contact strength of the composite improved when it was subjected to crack healing in combination with rapping; this was true even when the composite had cracks due to a heavy machining process.

UNS A03560

Alloy Digest ◽  
1986 ◽  
Vol 35 (12) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
High Strength ◽  
Heat Treating ◽  
Casting Alloy ◽  
Aluminum Casting ◽  
Good Resistance ◽  
Aluminum Casting Alloy ◽  
Temperature Performance ◽  
Heat Treated

Abstract UNS No. A03560 is a heat-treatable aluminum casting alloy. Normally it is used only when heat-treated (aged) strengths are required. It is recommended for high-strength, pressure-tight castings, intricate shapes and where good resistance to corrosion is needed. Its many applications include crank cases, gear cases, oil pans, airframe fittings and instrument housings. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on high temperature performance and corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: Al-274. Producer or source: Various aluminum companies.

FEDERATED F401.5Ni

Alloy Digest ◽  
1974 ◽  
Vol 23 (12) ◽  
Keyword(s):  
Fracture Toughness ◽  
Elevated Temperatures ◽  
High Strength ◽  
Heat Treating ◽  
Casting Alloy ◽  
Aluminum Casting ◽  
Aluminum Casting Alloy ◽  
Treated Condition ◽  
Heat Treated ◽  
Heat Treated Condition

Abstract FEDERATED F401.5Ni is a heat-treatable aluminum casting alloy with high strength and good wear resistance in the fully heat-treated condition. It is recommended for castings requiring good strength at elevated temperatures. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: Al-212. Producer or source: Federated Metals Corporation, ASARCO Inc..

UNS A02080

Alloy Digest ◽  
1988 ◽  
Vol 37 (1) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Shear Strength ◽  
Physical Properties ◽  
Tensile Properties ◽  
Heat Treating ◽  
General Purpose ◽  
Sand Casting ◽  
Casting Alloy ◽  
Heat Treated

Abstract UNS No. A02080 is a heat-treatable casting alloy characterized by good castability, machinability and resistance to corrosion. It is produced by sand casting and is a general-purpose alloy recommended in both the as-cast and heat-treated conditions. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and compressive and shear strength as well as fracture toughness and fatigue. It also includes information on corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: Al-286. Producer or source: Various aluminum companies.

ZIRCAR ZIRCONIA POWDER TYPE ZYP-4.5

Alloy Digest ◽  
1989 ◽  
Vol 38 (3) ◽  
Keyword(s):  
Fracture Toughness ◽  
Physical Properties ◽  
Yttrium Oxide ◽  
Zirconium Oxide ◽  
Raw Material ◽  
Bend Strength ◽  
Powder Metal ◽  
Zirconia Powder ◽  
Tetragonal Crystal ◽  
Powder Type

Abstract ZIRCAR ZIRCONIA POWDER TYPEZYP-4.5 is a highly reactive form of zirconium oxide stabilized in the tetragonal crystal state with added yttrium oxide. It is an excellent raw material for producing dense structural and wear resistant parts. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, and bend strength as well as fracture toughness. It also includes information on powder metal forms. Filing Code: Cer-1. Producer or source: Zircar Products Inc..

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