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Articles 1 - 8 of 8
Full-Text Articles in Mechanical Engineering
Size Scaling Of Strength And Toughness For 3d Printed Polymer Specimens, Darren Thomas Bell
Size Scaling Of Strength And Toughness For 3d Printed Polymer Specimens, Darren Thomas Bell
Open Access Theses
To find material systems that offer low density and high strength, stiffness or toughness, hierarchically designed material systems have provided a promising research area. This thesis lays the groundwork for designing efficient micro-architectured material systems by characterizing size effects for 3d printed polymer parts. Two methods were used to analyze data from 3-point bend tests for specimens of varying size: the load-separation method was used for finding the point of crack growth initiation and Bazant’s method was used to find shape independent strength at failure. The strength values were used as inputs for finding size independent material constants within a …
Passive Thermal Management Using Phase Change Materials, Yash Yogesh Ganatra
Passive Thermal Management Using Phase Change Materials, Yash Yogesh Ganatra
Open Access Theses
The trend of enhanced functionality and reducing thickness of mobile devices has led to a rapid increase in power density and a potential thermal bottleneck since thermal limits of components remain unchanged. Active cooling mechanisms are not feasible due to size, weight and cost constraints. This work explores the feasibility of a passive cooling system based on Phase Change Materials (PCMs) for thermal management of mobile devices. PCMs stabilize temperatures due to the latent heat of phase change thus increasing the operating time of the device before threshold temperatures are exceeded. The primary contribution of this work is the identification …
Machining As A Mechanical Property Test Revisited, David L. Smith
Machining As A Mechanical Property Test Revisited, David L. Smith
Open Access Theses
There is much need for data on mechanical behavior of metals at high strains and strain rates. This need is dictated by modeling of processes like forming and machining, wherein the material in the deformation zone is subjected to severe deformation conditions atypical of conventional material property tests such as tension and torsion. Accurate flow stress data is an essential input for robust prediction of process outputs. Similar requirements arise from applications in high speed ballistic penetration and design of materials for armor. Since the deformation zone in cutting of metals is characterized by unique and extreme combinations of strain, …
Delamination Of C/Pekk I-Beam Using Virtual Crack Closure Technique And Cohesive Zone Method, Greeshma Ramakrishna
Delamination Of C/Pekk I-Beam Using Virtual Crack Closure Technique And Cohesive Zone Method, Greeshma Ramakrishna
Open Access Theses
A damage study is conducted on a carbon epoxy/PEKK (poly-ether-ketone-ketone) thermoplastic composite I-Beam, with a pre crack of 100 mm modeled between the top flange and the filler (butt joint between filler and web). This project is in collaboration with Fokker Aerostructures, Netherlands and is part of the Thermoplastic Primary Aircraft Structure innovation program (TAPAS). The C/PEKK I-Beam is modeled after a section of the Gulfstream G650 aircraft's centre beam, which was previously a carbon fiber/epoxy hat-stiffened skin construction. The objective of the thesis is to identify if the crack propagates in the I-Beam within the load range that act …
Investigation Of Microstructural Alterations In M50 And 52100 Steel Using Nanoindentation, Kristin R. Paulson
Investigation Of Microstructural Alterations In M50 And 52100 Steel Using Nanoindentation, Kristin R. Paulson
Open Access Theses
Bearing steels are used in rolling elements and are designed to withstand heavy loads for an extended period of time. At the end of life, microstructural alterations within the material have been observed and are linked to failure. In this study, a three ball-on-rod fatigue tester was used to test M50 and 52100 steel cylindrical rods at differing loads of 4.0 GPa, 4.5 GPa, and 5.0 GPa and in lubricated and unlubricated conditions to 10 8 cycles in an attempt to produce microstructural alterations. Microstructural alterations characterized as butterflies were observed and investigated further in two M50 samples that were …
Measurement Of The Responses Of Polyurethane And Confortm Foams And The Development Of A System Identification Technique To Estimate Polyurethane Foam Parameters From Experimental Impulse Responses, Vaidyanadan Sundaram
Measurement Of The Responses Of Polyurethane And Confortm Foams And The Development Of A System Identification Technique To Estimate Polyurethane Foam Parameters From Experimental Impulse Responses, Vaidyanadan Sundaram
Open Access Theses
Flexible polyurethane foam is the main cushioning element used in car seats. Optimization of an occupied seat's static and dynamic behavior requires models of foam that are accurate over a wide range of excitation and pre-compression conditions. Experiments were conducted to measure the response of foam over a wide range of excitation which include slowly varying uniaxial compression tests on a 3 inch cube foam sample, base excitation and impulse excitation test on a foam-mass system. The foam used was the same in all of the experiments, thus obtaining all the responses on the same foam sample which helps eliminate …
Dissolution Rate And Mechanism Of Metals In Molten Aluminum Alloy A380, Hengyu Zhu
Dissolution Rate And Mechanism Of Metals In Molten Aluminum Alloy A380, Hengyu Zhu
Open Access Theses
Shot sleeve is a very easily worn out part in a high-pressure die-casting machine due to serious dissolution of the area underneath the pouring hole. It is because during a normal pouring process, the high temperature molten aluminum will impact and dissolve that area of the shot sleeve by complex chemical and physical process. Rotation experiment was carried out to H13 and four kinds of refractory metal samples. SEM and EDS pictures were taken in order to investigate the microstructure and the dissolution mechanism of these materials. This suggests a high strength niobium is an ideal material for that area …
Synthesis And Characterization Of Bulk Metallic Glasses Prepared By Laser Direct Deposition, Xiaoyang Ye
Synthesis And Characterization Of Bulk Metallic Glasses Prepared By Laser Direct Deposition, Xiaoyang Ye
Open Access Theses
Fe-based and Zr-based metallic glasses have attracted extensive interest for structural applications due to their excellent glass forming ability, superior mechanical properties, unique thermal and corrosion properties. In this study, the feasibility of synthesizing metallic glasses with good ductility by laser direct deposition is explored. Both in-situ synthesis with elemental powder mixture and ex-situ synthesis with prealloyed powder are discussed. Microstructure and properties of laser direct deposited metallic glass composites are analyzed.^ Synthesis of Fe-Cr-Mo-W-Mn-C-Si-B metallic glass composite with a large fraction of amorphous phase was accomplished using laser direct deposition. X-ray diffraction (XRD) and transmission electron microscopy investigations revealed …