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RISS 인기검색어
- 검색키워드
- 저자 : Cho-Pei Jiang (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Cho-Pei Jiang,Han-Jan Hsu,Shyh-Yuan Lee 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
Zirconia dental coping (ZDC) has an obvious aesthetic advantage over titanium implants, in that it is pure white, which makes itindistinguishable from the material of natural teeth. Conventional fabrication of ZDC uses CAD/CAM, but surface defects and microcrackscan result in a decrease in the ultimate strength and compressive resistance. This study proposes the use of mask-less projectionslurry stereolithography (MPSS) to fabricate the proposed benchmarks, such as 2.5D model with varying angles and ZDC, and usestwo-stage sintering to obtain the sintered parts. The experimental results show that the effective exposure time for the proposed slurrywith a minimum particle size of 1.1 μm is 5 seconds, which gives a curing depth of 23.4 μm. The maximum tolerance of the fabricatedgreen body is about 20 μm and linear shrinkage rate, after sintering, is 23.5%. SEM images show that no delamination occurs onthe surface of the green body and no cracks are found on sintered parts. The flexural strength and the hardness of the zirconia sinteredparts are 539.1 MPa and 13.02 GPa, respectively. Using this MPSS, it is also possible to construct green bodies for customizedzirconia dental restoration, as an alternative to CAD/CAM machining.
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Cho-Pei Jiang,Yo-Yu Chen 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
Most bone scaffolds made of single biomaterial resulting in limited compressive strength and single property of cell adhesive. In thisstudy, sandwich structures of the bone scaffold with different biomaterials are fabricated to mimic the mechanical properties of humanbone. The fabricated scaffolds are also evaluated the cellular efficacy by cell culturing. In this study, biopolymer (mPEG-PCL-mPEG)is synthesized. Biocomposite is made of blending biopolymer with nano-hydroxyapatite (nHA). Both biomaterials are used to form thebone scaffolds with average pore size of 300μm using the developed dual-nozzle bioplotter system. Hybrid scaffolds with sandwichstructures are proposed and fabricated. All scaffolds are underwent the compressive and microhardness test for comparing themechanical properties with human bone. Furthermore, a mouse pre-osteoblast MC3T3-E1cell line is seeded onto fabricated scaffoldsand cultured for 28 days for validating the biocompatibility and evaluating the cellular efficacy using methylthiazol tetrazolium (MTT)assay. Biocomposite scaffold has the highest ultimate compressive strength and microhardenss among the others. Ultimatecompressive strength and microhardness of fabricated scaffold in vertical build plane are higher than those in horizontal build plane. Sandwich architecture of hybrid bone scaffold with biocomposite outer layer and biopolymer inner layer can improve cell adhesiveand cellular efficacy.
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Cho-Pei Jiang 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
This study determines the effect of grain size on the mechanical properties and the deformability of titanium bar in a direct extrusionprocess. The specimen of commercially pure grade 2 (CP2) with a diameter of 5 mm is annealed at various temperatures, to obtaindifferent grain sizes, and extruded with die angles of 5, 10 and 15º. The results show that the initial grain size of α-phasemicrostructure is in the range of 59.7 to 122.1. The strength coefficient, yielding stress and hardness of the annealed specimen withan α-phase microstructure decreases as the grain size increases. β-phase microstructure forms when the annealing temperatureexceeds 800ºC, which leads to a reduction in the ductility and extrusion deformability, but an increase in the hardness. The grainevolution sequences are coarse columnar, thin columnar and refined grain. The initial grain size has no significant effect on extrusionforce. The hardness of the refined grains is close to that of the initial grains.
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Cho-Pei Jiang 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
The aims of this study were to investigate the effect of initial grain size on mechanical properties of thin stainless steel sheet (SUS304) with an initial thickness of 1 mm underwent varying reduction ratios by roll forming and to analyze the effect of grain refinement on springback behavior in micro V-bending process. Specimens were carried out the annealing treatment to obtain different initial grain sizes in a range of 15.1 to 30.2 mm. The annealed specimens were rolled with varying reduction ratios. All specimens were conducted the tensile test for measuring the Young’s modulus, strength coefficient and strain-hardening exponent. The rolled specimens with varying reduction ratio were carried out V-bending with an angle of 90o. Furthermore, the springback behavior was simulated using finite element method and compared the springback amount with that of the experimental result. Consequently, larger initial grain size induced higher ductility but decreased ultimate tensile strength and lower yielding strength. Although grain refinement induced brittle behavior with higher elastic modulus and smaller plasticity, high elastic modulus may contribute the higher springback amount.
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Tsung-Han Huang,Cho-Pei Jiang,Fedor V. Grechnikov 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.10
This study investigates the effect of grain size on the deformability of CP2 Titanium to form the mini spur gear in hot squeezing forming process. Experimental specimens are rods with a diameter of 5 mm and annealed with temperature in a range of 500 to 1000°C to precipitate the different initial grain sizes individually. The mechanical properties and hardness of annealed specimens are measured. A mini spur gear die with a modulus of 0.915 and 8 teeth, made of H13 steel, is prepared. The annealed specimens are inserted in die and hot squeezed to form mini spur gear with a temperature of 500°C. The experimental results show that the α-phase microstructure precipitates when the annealing temperature and holding time are 700°C and 3 hours. The specimen with average initial grain size of 154.59 μm results in the maximal elongation and die cavity-filling rate. Harnesses of addendum and dedendum circle are about 215 and 180 MPa that are higher than that of initial grain (107 MPa). The β-phase microstructure precipitates when annealing temperature reaches to 900°C resulting in brittle behavior.
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