Browsing by Author "Zhou, Yingge (TTU)"
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Item Energy consumption and saving analysis for laser engineered net shaping of metal powders(2016) Liu, Zhichao (TTU); Ning, Fuda (TTU); Cong, Weilong (TTU); Jiang, Qiuhong (TTU); Li, Tao; Zhang, Hongchao (TTU); Zhou, Yingge (TTU)With the increasing awareness of environmental protection and sustainable manufacturing, the environmental impact of laser additive manufacturing (LAM) technology has been attracting more and more attention. Aiming to quantitatively analyze the energy consumption and extract possible ways to save energy during the LAM process, this investigation studies the effects of input variables including laser power, scanning speed, and powder feed rate on the overall energy consumption during the laser deposition processes. Considering microhardness as a standard quality, the energy consumption of unit deposition volume (ECUDV, in J/mm3) is proposed as a measure for the average applied energy of the fabricated metal part. The potential energy-saving benefits of the ultrasonic vibration-assisted laser engineering net shaping (LENS) process are also examined in this paper. The experimental results suggest that the theoretical and actual values of the energy consumption present different trends along with the same input variables. It is possible to reduce the energy consumption and, at the same time, maintain a good part quality and the optimal combination of the parameters referring to Inconel 718 as a material is laser power of 300 W, scanning speed of 8.47 mm/s and powder feed rate of 4 rpm. When the geometry shaping and microhardness are selected as evaluating criterions, American Iron and Steel Institute (AISI) 4140 powder will cause the largest energy consumption per unit volume. The ultrasonic vibration-assisted LENS process cannot only improve the clad quality, but can also decrease the energy consumption to a considerable extent.Item Fabrication of nanofiber mats with microstructure gradient by cone electrospinning(2017) Zhou, Yingge (TTU); Tan, George Z. (TTU)As a versatile nanofiber manufacturing technique, electrospinning has been widely used for tissue engineering scaffold fabrication. However, it remains challenging to create scaffolds with anisotropic microstructure close to native tissues. This article presented a novel electrospinning configuration to generate fibrous mat with microstructure gradient. A series of proof-of-concept tests were performed to investigate the effects of process parameters on the gradient of nanofiber morphology and mat attributes. The technique developed in this study showed great potentials as a fabrication platform for heterogenous nanofiber products.Item Feasibility Exploration of Superalloys for AISI 4140 Steel Repairing using Laser Engineered Net Shaping(2017) Liu, Zhichao (TTU); Cong, Weilong (TTU); Kim, Hoyeol (TTU); Ning, Fuda (TTU); Jiang, Qiuhong (TTU); Li, Tao; Zhang, Hong-chao (TTU); Zhou, Yingge (TTU)Due to high strength and ductility, AISI 4141 alloy steel is widely used in many industrial applications, such as gears and blades. When it is composed to harsh working environment, severe mechanical failures may happen. In order to save the high added value of the components, necessary repairing techniques are required to recover their functionality. Laser Engineered Net Shaping (LENS) is an innovative technology for metal parts repairing and rebuilding due to its metallurgical bonding and exhibit heat affected zone (HAZ). Compared to other repairing processes, LENS cannot only reduce the manufacturing time and cost, increase material utilization, but also provide an outstanding as-fabricated mechanical properties. Considering the compatibility and availability of powder materials, the selection of to-be-fabricated materials are important and decisive to the mechanical properties and the quality of the deposits. In this investigation, nickel-based and cobalt based superalloys are deposited onto AISI 4140 steel substrate using laser engineered net shaping (LENS) process to verify the feasibility of these superalloys for repairing of AISI 4140 workpieces. The micro-hardness, tensile strength, fracture and wear resistance are analyzed to testify the resistance of deformation, tension and anti-friction performance of deposited materials.Item Tunable 3D Nanofiber Architecture of Polycaprolactone by Divergence Electrospinning for Potential Tissue Engineering Applications(2018) Tan, George Z. (TTU); Zhou, Yingge (TTU)The creation of biomimetic cell environments with micro and nanoscale topographical features resembling native tissues is critical for tissue engineering. To address this challenge, this study focuses on an innovative electrospinning strategy that adopts a symmetrically divergent electric field to induce rapid self-assembly of aligned polycaprolactone (PCL) nanofibers into a centimeter-scale architecture between separately grounded bevels. The 3D microstructures of the nanofiber scaffolds were characterized through a series of sectioning in both vertical and horizontal directions. PCL/collagen (type I) nanofiber scaffolds with different density gradients were incorporated in sodium alginate hydrogels and subjected to elemental analysis. Human fibroblasts were seeded onto the scaffolds and cultured for 7 days. Our studies showed that the inclination angle of the collector had significant effects on nanofiber attributes, including the mean diameter, density gradient, and alignment gradient. The fiber density and alignment at the peripheral area of the 45°-collector decreased by 21% and 55%, respectively, along the z-axis, while those of the 60°-collector decreased by 71% and 60%, respectively. By altering the geometry of the conductive areas on the collecting bevels, polyhedral and cylindrical scaffolds composed of aligned fibers were directly fabricated. By using a four-bevel collector, the nanofibers formed a matrix of microgrids with a density of 11%. The gradient of nitrogen-to-carbon ratio in the scaffold-incorporated hydrogel was consistent with the nanofiber density gradient. The scaffolds provided biophysical stimuli to facilitate cell adhesion, proliferation, and morphogenesis in 3D.