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Green Micromachining of Ceramics: Feasibility and Machinability
Başlık:
Green Micromachining of Ceramics: Feasibility and Machinability
Yazar:
Onler, Recep, author.
ISBN:
9780355987690
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (165 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Advisors: O. Burak Ozdoganlar Committee members: Sundar V. Atre; C. Fred Higgs, III; Rahul Panat.
Özet:
Ceramics offer many unique mechanical, thermal, electrical and chemical properties that make them ideal materials for a broad range of applications. However, the same properties that make ceramics attractive materials also bring strict limitation to their manufacturability. The manufacturability limitations are further exacerbated at the microscale: although there are many potential applications for micro-scale features, components, and devices made from ceramics, those applications cannot be realized without effective approaches for micro-manufacturing of ceramics.
Towards addressing the challenge of micromanufacturing of ceramics, in this thesis, we are proposing an approach referred to as green micromachining. Green micromachining involves fabricating micro-scale features green-state ceramics using mechanical micromachining, and subsequently debinding their binder and sintering them to obtain solid ceramics with micro-scale features. Since the strong bonds between the ceramic particles are not generated in the green state, mechanics of material removal is dominated by the binder, and thus, becomes significantly easier---producing considerably lower forces and tool wear. If done effectively, the GMM approach promises significant advantages in geometric and shape capabilities, and in both lead time and cost of fabrication.
This doctoral research investigates the feasibility of green micromachining to fabricate micro-scale features in various ceramics. The overarching research objective of this doctoral thesis is to determine the effect of GMM parameters on process forces, microtool wear, and resulting quality of the fabricated micro-scale features on ceramics. The specific objectives of this work are to (1) analyze green micromachinability of ceramics through experimental analyses; (2) characterize micromachining mechanics and forces via orthogonal machining; (3) develop a mechanistic model for forces arising from GMM; (4) characterize the wear of microtools under different process conditions and for different tool materials and coatings; and (5) evaluate geometric and shape characteristics of features fabricated through GMM on sintered ceramics.
Toward addressing the research objectives, first, GMM of ceramics is experimentally investigated. Similar to other manufacturing processes, there is a strong correlation between process conditions and output quality in GMM. To quantify the effect of process parameters and material conditions on green micromachining outputs, various powder/binder combinations of two important ceramics are green micromachined using a design of experiments approach. The resulting surface roughness, cutting forces, specific energies, burr formation, and tool wear are qualitatively or quantitatively evaluated.
Second, process mechanics and the associated process forces during GMM are analyzed. Forces measured during micromachining reveal essential characteristics of the process from material removal mechanisms to tool wear. Due to the complexity of cutting geometry and kinematics of the process, micro-endmilling does not provide a clear connection between machining forces and process inputs. To better understand the nature of process mechanics and the associated forces, orthogonal machining experiments are conducted. The relationship between machining parameters and GMM forces are explored for both a rounded tool and a sharp tool.
Third, a mechanistic force model for GMM is developed and experimentally validated. Micromachining forces are also critical to avoid tool breakage, excessive tool deflection, and damage to the miniature machine tool system used for GMM. As such, it is critical to predicting the effect of process parameters on GMM forces. To predict the uncut chip thicknesses accurately, a comprehensive chip thickness model considering process kinematics, workpiece elastic recovery, and tool-trajectory errors is developed. Next, a calibration approach is developed: the approach requires a minimum number of micromachining experiments and uses a genetic algorithm approach to identify the calibration parameters from the experimental forces.
Fourth, an investigation of micro-tool wear during GMM is performed. Understanding tool wear mechanism and its progression is critical towards assessing the feasibility of GMM. The objective of this work is to observe the wear mechanism and measure the wear progression during GMM using coated and uncoated microtools. For this purpose, the tool wear during GMM of SiC and AlN is evaluated to identify the wear characteristics when micromachining workpieces with different powder and binder combinations. The change in specific energies and burr formation with wear progression is explored. Subsequently, a comprehensive investigation of micro-tool wear on green SiC is conducted.
Fifth, a study on GMM-based micro-manufacturing of Zirconia is presented. The purpose of this study is to demonstrate the entire process flow, including the fabrication of the green blanks through die pressing of powdered Zirconia, GMM, debinding, and sintering, resulting in micro-scale ceramic features. Although optimization of sintering temperature profile is beyond the scope of this work, a favorable temperature profile that results in crack-free samples with uniform shrinkage is identified and used during sintering. (Abstract shortened by ProQuest.).
Notlar:
School code: 0041
Konu Başlığı:
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(681802.1) | 681802-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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