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You searched for +publisher:"NSYSU" +contributor:("H. K. Lin"). Showing records 1 – 2 of 2 total matches.

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NSYSU

1. Kuan, Sheng-Yao. Mechanical Behaviors and Shear Band Deformation Mechanisms in Thin Film Metallic Glasses and Composites.

Degree: PhD, Materials and Optoelectronic Science, 2013, NSYSU

Metallic glasses have attracted considerable attention because of their excellent mechanical properties such as high strength and hardness. Moreover, many researchers note the potential applications in terms of biodegradable and micro-electro-mechanical systems (MEMS) due to the lack of periodic atomic packing, indicating that there is no defect such as grain boundary, dislocation, or plane defect in amorphous alloys. However, the high strength of metallic glasses is often accompanied by a virtually zero plastic strain and can fail in a catastrophic manner. Plastic deformation of metallic glasses is highly localized in shear bands, which usually propagate rapidly through the sample. The brittle problem limits the application of thin film metallic glasses (TFMGs) for MEMS devices. To improve the brittle problem, this study has used two types of improvement methods, namely, the multilayered thin film metallic glasses and thin film metallic glass composites. For multilayered thin film metallic glasses, ZrCuTi (ZCT) 50 nm / PdCuSi (PCS) 50 nm TFMGs and ZrCuTi (ZCT) 50 nm / ZrCuTiTa (ZCTTa) 50 nm TFMGs are prepared by sputtering. The mechanical properties and the deformation characteristics of TFMGs are investigated by using expanding cavity model and nanoindentation testing. Utilizing the multilayered structure, the as-formed shear bands can be easily detected by scanning electron microscopy (SEM) and cross section transmission electron microscopy (XTEM). Two kinds of shear bands (radius shear bands and semi-circular shear bands) are observed by XTEM. Comparing the results of deformed microstructure and the load-displacement curves, a transition point from the radius type to semi-circular type of shear band can be found. The deflection phenomenon has been found by microcompression. In addition, the yield strength is enhanced by the multilayered structure. For improving the ductility of bulk metallic glasses (BMGs), nanocrystals within the amorphous matrix have been frequently and intentionally added. Similarly, to reduce the brittle problem of TFMGs, the MgCuZr TFMGs, with a positive mixing heat between Mg and Zr, are fabricated via co-sputtering, in an attempt to separate the pure Mg nano-particles from the amorphous ZrCu matrix. The nanocrystalline Mg particles are expected to hinder the propagation of shear bands and to affect the mechanical characteristics of TFMGs. The structures of sputtered MgCuZr thin films are found to depend on the composition of Mg. For MgCuZr thin films with Mg content from 48 to 73 at%, the structure is the amorphous matrix with discontinuous Mg particles, and the Mg particle size in these TGMGs is all about 20-50 nm, as measured by TEM. The effects of different microstructures of Mg on mechanical response are investigated and discussed. From the nanoindentation load-displacement curves, the Mg-based metallic glass composites exhibit smoother nature. It implies that the Mg nano-particle can stop the propagation of shear bands under nanoindentation loading. Meanwhile, the microcompression… Advisors/Committee Members: H. K. Lin (chair), Cheng-Tang Pan (chair), Shian-Ching Jang (chair), J. C. Huang (committee member), Shin-Pon Ju (chair).

Subjects/Keywords: Microcompresion; Metallic glasses; Thin film; Nanoindentation; Mechanical properties

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APA (6th Edition):

Kuan, S. (2013). Mechanical Behaviors and Shear Band Deformation Mechanisms in Thin Film Metallic Glasses and Composites. (Doctoral Dissertation). NSYSU. Retrieved from http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1117113-140223

Chicago Manual of Style (16th Edition):

Kuan, Sheng-Yao. “Mechanical Behaviors and Shear Band Deformation Mechanisms in Thin Film Metallic Glasses and Composites.” 2013. Doctoral Dissertation, NSYSU. Accessed March 24, 2019. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1117113-140223.

MLA Handbook (7th Edition):

Kuan, Sheng-Yao. “Mechanical Behaviors and Shear Band Deformation Mechanisms in Thin Film Metallic Glasses and Composites.” 2013. Web. 24 Mar 2019.

Vancouver:

Kuan S. Mechanical Behaviors and Shear Band Deformation Mechanisms in Thin Film Metallic Glasses and Composites. [Internet] [Doctoral dissertation]. NSYSU; 2013. [cited 2019 Mar 24]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1117113-140223.

Council of Science Editors:

Kuan S. Mechanical Behaviors and Shear Band Deformation Mechanisms in Thin Film Metallic Glasses and Composites. [Doctoral Dissertation]. NSYSU; 2013. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-1117113-140223


NSYSU

2. Chen, Sheng-Yu. Microstructure and mechanical properties of porous Ti-6Al-4V alloys for bone implants fabricated by additive manufacturing.

Degree: PhD, Materials and Optoelectronic Science, 2018, NSYSU

In recent years, additive manufacture (AM), or called as rapid prototyping or 3D printing, has become a flourishing industry suitable to fabricate bio-implants, due to the benefits such as the reduction in process steps, complexity of parts, and customization. Among of them, the application of human bone has been most widely studied. However, the bone is a porous structure, subjected to wide variations as a result of human movement and inevitable changes with age, sex, and location. Therefore, it is important to study the relationship between the porous structure and mechanical properties of various bionic implants. In this study, we used the selective laser melting (SLM) and electron beam melting (EBM) methods to produce porous structures of bone bio-implants. The highly biocompatible Ti-6Al-4V alloy was applied as experimental. For the first part, using Ti-6Al-4V alloy powders, the Ti-6Al-4V porous samples were fabricated by SLM, with the help from computer-aided design (CAD) for different porosities. Compared with the CAD models and porous samples fabricated by SLM, the relevant relationships are characterized with morphology, physical properties and mechanical properties. The difference between the CAD model and porous SLM parts leads to the larger ligament widths and smaller pore sizes for SLM parts, due to the laser beam broadening and laser melting edge effects. Due to the higher porosity samples with a higher pore number density, this difference between the CAD model and porous SLM parts could be more obvious, so that the designed porosity will be greater than that of the actual porosity of porous samples. The difference can be reduced by decreasing the size of laser beam and the used powders. The structure of Ti-6Al-4V prepared by SLM was seen to possess higher hardness favorable for wear resistance and beneficial for the application of human bone implant. The mechanical properties (elastic modulus and yield strength) of porous SLM parts decrease with increasing porosity, matching well with the human bone. In terms of the matched elastic modulus, it can avoid the risk of stress shielding effect. By applying the Gibson and Ashby model, the relationship between porosity and mechanical properties of SLM porous foams can be described and predicted. According to many previous studies, the porous samples with high porosity can effectively reduce the stress shielding problem, but mechanical strength would also be reduced. For the second part, the high porosity of porous Ti-6Al-4V samples are fabricated by EBM, and the physical and mechanical properties are characterized. The results indicate that the porosity of porous parts can be as high as near 80% by increasing the ligament and pore size. The elastic modulus of such EBM porous Ti-6Al-4V structure with high porosity is found to match well with that of the human cancellous bone. However, it can obviously be seen that the higher ligament width of porous samples will enhance the endurance to fracture. Therefore, the relationship between the ligament width and work… Advisors/Committee Members: C. H. Lin (chair), J. S. C. Jang (chair), C. T. Pan (chair), H. K. Lin (chair), J. C. Huang (committee member).

Subjects/Keywords: additive manufacturing; porosity; mechanical property; Ti alloy; selective laser melting; electron beam melting

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Chen, S. (2018). Microstructure and mechanical properties of porous Ti-6Al-4V alloys for bone implants fabricated by additive manufacturing. (Doctoral Dissertation). NSYSU. Retrieved from http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0521118-112626

Chicago Manual of Style (16th Edition):

Chen, Sheng-Yu. “Microstructure and mechanical properties of porous Ti-6Al-4V alloys for bone implants fabricated by additive manufacturing.” 2018. Doctoral Dissertation, NSYSU. Accessed March 24, 2019. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0521118-112626.

MLA Handbook (7th Edition):

Chen, Sheng-Yu. “Microstructure and mechanical properties of porous Ti-6Al-4V alloys for bone implants fabricated by additive manufacturing.” 2018. Web. 24 Mar 2019.

Vancouver:

Chen S. Microstructure and mechanical properties of porous Ti-6Al-4V alloys for bone implants fabricated by additive manufacturing. [Internet] [Doctoral dissertation]. NSYSU; 2018. [cited 2019 Mar 24]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0521118-112626.

Council of Science Editors:

Chen S. Microstructure and mechanical properties of porous Ti-6Al-4V alloys for bone implants fabricated by additive manufacturing. [Doctoral Dissertation]. NSYSU; 2018. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0521118-112626

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