IU Indianapolis ScholarWorks :: Browsing by Author "Koo, Dan Daehyun"

Browsing by Author "Koo, Dan Daehyun"

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Analysis of the Flow Performance of the Complex Cross-Section Module to Reduce the Sedimentation in a Combined Sewer Pipe
(MDPI, 2020-11) Ji, Hyon Wook; Yoo, Sung Soo; Koo, Dan Daehyun; Kang, Jeong-Hee; Engineering Technology, School of Engineering and Technology
The difference in the amount of stormwater and sewage in a combined sewer system is significantly large in areas where heavy rainfall is concentrated. This leads to a low water level and slow flow velocity inside the pipes, which causes sedimentation and odor on non-rainy days. A complex cross-section module increases the flow velocity by creating a small waterway inside the pipe for sewage to flow on non-rainy days. While considering Manning’s equation, we applied the principle where the flow velocity is proportional to two-thirds of the power of the hydraulic radius. The flow velocity of a circular pipe with a diameter of 450 mm and the corresponding complex cross-section module was analyzed by applying Manning’s equation and numerical modeling to show the effects of the complex cross-section module. The tractive force was compared based on a lab-scale experiment. When all conditions were identical except for the cross-sectional shape, the average flow velocity of the complex cross-section module was 14% higher while the size of the transported sand grains was up to 0.5 mm larger. This increase in flow velocity can be even higher if the roughness coefficient of aging pipes can be decreased.
Determination of Internal Elevation Fluctuation from CCTV Footage of Sanitary Sewers Using Deep Learning
(MDPI, 2021) Ji, Hyon Wook; Yoo, Sung Soo; Koo, Dan Daehyun; Kang, Jeong-Hee; Engineering Technology, School of Engineering and Technology
The slope of sewer pipes is a major factor for transporting sewage at designed flow rates. However, the gradient inside the sewer pipe changes locally for various reasons after construction. This causes flow disturbances requiring investigation and appropriate maintenance. This study extracted the internal elevation fluctuation from closed-circuit television investigation footage, which is required for sanitary sewers. The principle that a change in water level in sewer pipes indirectly indicates a change in elevation was applied. The sewage area was detected using a convolutional neural network, a type of deep learning technique, and the water level was calculated using the geometric principles of circles and proportions. The training accuracy was 98%, and the water level accuracy compared to random sampling was 90.4%. Lateral connections, joints, and outliers were removed, and a smoothing method was applied to reduce data fluctuations. Because the target sewer pipes are 2.5 m concrete reinforced pipes, the joint elevation was determined every 2.5 m so that the internal slope of the sewer pipe would consist of 2.5 m linear slopes. The investigative method proposed in this study is effective with high economic feasibility and sufficient accuracy compared to the existing sensor-based methods of internal gradient investigation.
Finite Element Modeling of Coating Thickness Using Heat Transfer Method
(Elsevier, 2021-01) Li, Yafeng; Dhulipalla, Anvesh; Zhang, Jian; Park, Hye-Yeong; Jung, Yeon-Gil; Koo, Dan Daehyun; Zhang, Jing; Mechanical and Energy Engineering, School of Engineering and Technology
A new heat transfer based finite element model is proposed to simulate coating thickness in the electron-beam physical vapor deposition (EB-PVD) process. The major advantage of the proposed model is that it is much computationally efficient than the traditional ray-tracing based model by about two orders of magnitude. This is because the Gaussian distribution heating source has the same profile as the cosine relation used in the ray-tracing method. Firstly, the model simulates the temperature profile of a metal substrate heated by a heating source with a Gaussian distribution. Then using a calibrated conversion process, the temperature profile is converted to corresponding coating thickness. The model is successfully demonstrated by three validation cases, including a stationary disk, a stationary cylinder, and a rotary three-pin component. The predicted coating thicknesses in the validation cases are in good agreement with either the ray-tracing based analytical solution or experimental data. After its validation, the model is applied to a rotary turbine blade to predict its coating thickness distribution. In summary, the model is capable to simulate coating thickness in complex shaped parts.
Gap Analysis Based Decision Support Methodology to Improve Level of Service of Water Services
(MDPI, 2017-09-05) Han, Sangjong; Koo, Dan Daehyun; Kim, Youngkyung; Kim, Seonghoon; Park, Joonhong; Engineering Technology, School of Engineering and Technology
One of water utility’s managerial challenges is to make a balance in between two distinctive managerial goals, cost-effective provision of water service and improving customer satisfaction of water service. As management priorities of the water utility perspective do not reconcile from the customer’s perspective, this gap challenges the sustainable provision of water service. In this study, the new methodology based on a gap analysis was proposed to improve the Overall Level of Service (O-LOS) of water service. Two new indexes (Gap Index [GI] and the Efficiency Index [EI]) were developed to improve the O-LOS and minimize the gap between the customers and the service providers. The methodology proposed in this study is effective in supporting the water utility decisions on budget allocation to make a balance in between the customers’ demand and the service providers’ needs.
High Performance Thermal Barrier Coatings on Additively Manufactured Nickel Base Superalloy Substrates
(2023-08) Dube, Tejesh Charles; Zhang, Jing; Jones, Alan S.; Koo, Dan Daehyun; Yang, Shengfeng
Thermal barrier coatings (TBCs) made of low-thermal-conductivity ceramic topcoat, metallic bond coat and metallic substrate, have been extensively used in gas turbine engines for thermal protection. Recently, additive manufacturing (AM) or 3D printing techniques have emerged as promising manufacturing techniques to fabricate engine components. The motivation of the thesis is that currently, application of TBCs on AM’ed metallic substrate is still in its infancy, which hinders the realization of its full potential. The goal of this thesis is to understand the processing-structure-property relationship in thermal barrier coating deposited on AM’ed superalloys. The APS method is used to deposit 7YSZ as the topcoat and NiCrAlY as the bond coat on TruForm 718 substrates fabricated using the direct metal laser sintering (DMLS) method. For comparison, another TBC system with the same topcoat and bond coat is deposited using APS on wrought 718 substrates. For thermomechanical property characterizations, thermal cycling, thermal shock (TS) and jet engine thermal shock (JETS) tests are performed for both TBC systems to evaluate thermal durability. Microhardness and elastic modulus at each layer and respective interfaces are also evaluated for both systems. Additionally, the microstructure and elemental composition are thoroughly studied to understand the cause for better performance of one system over the other. Both TBC systems showed similar performance during the thermal cycling and JETS test but TBC systems with AM substrates showed enhanced thermal durability especially in the case of the more aggressive thermal shock test. The TBC sample with AM substrate failed after 105 thermal shock cycles whereas the one with wrought substrate endured a maximum of 85 cycles after which it suffered topcoat delamination. The AM substrates also demonstrated an overall higher microhardness and elastic modulus except for post thermal cycling condition where it slightly underperformed. This study successfully demonstrated the use of AM built substrates for an improved TBC system and validated the enhanced thermal durability and mechanical properties of such a system. A modified YSZ TBC architecture with an intermediate Ti3C2 MXene layer is proposed to improve the interfacial adhesion at the topcoat/bond coat interface to improve the thermal durability of YSZ TBC systems. First principles calculations are conducted to study the interfacial adhesion energy in the modified and conventional YSZ TBC systems. The results show enhanced adhesion at the bond coat/MXene interface. At the topcoat/MXene interface, the adhesion energy is similar to the adhesion energy between the topcoat and bond coat in a conventional YSZ TBC system. An alternative route is proposed for the fabrication of YSZ TBC on nickel base superalloy substrates by using the SPS technology. SPS offers a one-step fabrication process with faster production time and reduced production cost since all the layers of the TBC system are fabricated simultaneously. Two different TBC systems are processed using the same heating protocol. The first system is a conventional TBC system with 8YSZ topcoat, NiCoCrAlY bond coat and nickel base superalloy substrate. The second system is similar to the first but with an addition of Ti3C2 MXene layer between the topcoat and the bond coat. Based on the first principles study, addition of Ti3C2 layer enhances the adhesion strength of the topcoat/bond coat interface, an area which is highly susceptible to spallation. Further tests such as thermal cycling and thermal shock along with the evaluation of mechanical properties would be carried out for these samples in future studies to support our hypothesis.
Hydraulic and Structural Analysis of Complex Cross-Section Reinforced Concrete Pipes to Improve Sewage Flow in a Combined Sewer System
(MDPI, 2021-11) Ji, Hyon Wook; Kang, Jeong-Hee; Koo, Dan Daehyun; Yoo, Sung Soo; Engineering Technology, School of Engineering and Technology
A complex cross-section reinforced concrete pipe that combines a sub-pipe for the flow of sewage in dry weather and a main pipe for the flow of rainwater was developed to reduce sedimentation of the combined sewer system in dry weather. The sub-pipe was designed, considering the flow velocity, constructability, and maintenance. By fitting the sewage data in the dry weather to the normal distribution, the ratio of the cross-sectional area of sewage flow to that of the pipe was determined to be approximately 0.418, which could cover 99.85% of the sewage volume of the target site. Based on this ratio, the diameter of the sub-pipe corresponding to the combined sewer system with a pipe diameter between 450 and 1300 mm was determined. The hydraulic performance analysis results showed that the flow velocity increased by 11 to 12% compared to the circular pipe based on the full sub-pipe and by more than 15% depending on the water level. The shear stress increased by more than 16.5%, and higher tractive force was observed. Structural safety was determined as the crack load and failure load far exceeded the minimum criteria, thereby verifying the feasibility and field applicability of the complex cross-section reinforced concrete pipe.
Measurement of Wastewater Discharge in Sewer Pipes Using Image Analysis
(MDPI, 2020-06) Ji, Hyon Wook; Yoo, Sung Soo; Lee, Bong-Jae; Koo, Dan Daehyun; Kang, Jeong-Hee; Engineering Technology, School of Engineering and Technology
Generally, the amount of wastewater in sewerage pipes is measured using sensor-based devices such as submerged area velocity flow meters or non-contact flow meters. However, these flow meters do not provide accurate measurements because of impurities, corrosion, and measurement instability due to high turbidity. However, cameras have advantages such as their low cost, easy service, and convenient operation compared to the sensors. Therefore, in this study, we examined the following three methods for measuring the flow rate by capturing images inside of a sewer pipe using a camera and analyzing the images to calculate the water level: direct visual inspection and recording, image processing, and deep learning. The MATLAB image processing toolbox was used for analysis. The image processing found the boundary line by adjusting the contrast of the image or removing noise; a network to find the boundary line between wastewater and sewer pipe was created after training the image segmentation results and placing them into three categories using deep learning. From the recognized water levels, geometrical features were used to identify the boundary lines, and flow velocities and flow rates were calculated from Manning’s equation. Using direct inspection and image-processing techniques, boundary lines in images were detected at rates of 12% and 53%, respectively. Although the deep-learning model required training, it demonstrated 100% water-level detection, thereby proving to be the most advantageous method. Moreover, there is enough potential to increase the accuracy of deep learning, and it can be a possible replacement for existing flow measurement sensors.
The Mechanical Properties of High Strength Reinforced Cured-in-Place Pipe (CIPP) Liner Composites for Urban Water Infrastructure Rehabilitation
(MDPI, 2018-08) Ji, Hyun Wook; Yoo, Sung Soo; Kim, Jonghoon; Koo, Dan Daehyun; Engineering Technology, School of Engineering and Technology
Most urban areas in the world have water infrastructure systems, including the buried sewer and water pipelines, which are assessed as in need of extensive rehabilitation. Deterioration by many other factors affects structural integrity. Trenchless technologies such as Cured-in-Place Pipe (CIPP) are now applied in numerous projects while minimizing disturbance in an urban environment. The main purpose of this study is to develop a high strength CIPP material using various composite materials (e.g., glass fiber, carbon fiber, polyester felt, unsaturated polyester resin, and others). Composite samples were made of the materials and tested using three-point bend apparatus to find mechanical properties, which include the flexural modulus, strength, and deflection. A composite combination with glass fibers with thin felt layers shows the best results in mechanical properties. Flexural modulus is a key factor for CIPP liner thickness design. Glass fiber composite yields between four and nine times higher values than the minimum value specified in the American Society for Testing and Materials (ASTM) F1216. This study provides a fundamental baseline for high strength CIPP liners that are capable of using conventional curing technologies.
Modeling of machining process of EB-PVD ceramic coatings using discrete element method
(Elsevier, 2022-08) Zhang, Jian; Sagar, Sugrim; Dube, Tejsh; Yang, Xuehui; Choi, Hyunhee; Jung, Yeon-Gil; Koo, Dan Daehyun; Zhang, Jing; Mechanical and Energy Engineering, School of Engineering and Technology
In this work, a new discrete element model (DEM) for simulating the machining process of thermal barrier coatings is presented. The effects of cutting processing parameters, including cutting depth and cutting speed, on the cutting force and chip morphology are studied. In the model, a columnar grain microstructure mimicking the electron-beam physical vapor deposition (EB-PVD) coating is used. The results show that, as the cutting depth increases, the cutting chip morphology changes from fine powder form (ductile mode) to large chuck pieces (brittle mode). The transition depth or the critical cutting depth is determined based on the Griffith fracture criterion. The transition is also illustrated using the numbers of broken bonds and cutting energy changes in the DEM model. In the ductile mode, the number of broken bonds is increased gradually. In contrast, at larger cutting depths, the brittle mode causes a step-wise increase. Moreover, the maximum cutting force is found correlated to the cutting depth, which agrees well with an analytical solution based on fracture mechanics principles. The period in the cutting force is consistent with the diameter of the column grain. Finally, the cutting speed has little effect on the cutting force and chip morphology due to no strain rate sensitivity.
Molecular dynamics modeling of mechanical and tribological properties of additively manufactured AlCoCrFe high entropy alloy coating on aluminum substrate
(Elsevier, 2021-04-15) Yang, Xuehui; Zhang, Jian; Sagar, Sugrim; Dube, Tejesh; Kim, Bong-Gu; Jung, Yeon-Gil; Koo, Dan Daehyun; Jones, Alan; Zhang, Jing; Mechanical and Energy Engineering, School of Engineering and Technology
In this work, an improved molecular dynamics (MD) model is developed to simulate the nanoindentation and tribological tests of additively manufactured high entropy alloys (HEA) AlCoCrFe coated on an aluminum substrate. The model shows that in the interface region between the HEA coating and Al substrate, as the laser heating temperature increases during the HEA coating additive manufacturing process, more Al in the substrate is melted to react with other elements in the coating layer, which is qualitatively in agreement with experiment in literature. Using the simulated nanoindentation tests, the calculated Young's modulus of pure Al and Al with HEA coating is 79.93 GPa and 119.30 GPa, respectively. In both our simulations and the experimental results in the literature, the hardness of Al with the HEA coating layer is about 10 times higher than the Al hardness, indicating that HEA can significantly improve the hardness of the metallic substrate. Using the simulated tribological scratch tests, the computed wear tracks are qualitatively in agreement with experimental images in literature. Both our model and experiment show that the Al with HEA coating has a much smaller wear track than that of Al, due to less plastic deformation, confirmed by a dislocation analysis. The computed average coefficient of friction of Al is 0.62 and Al with HEA coating is 0.14. This work demonstrates that the HEA coating significantly improves the mechanical and tribology properties, which are in excellent agreement with the experiments reported in the literature.

Browsing by Author "Koo, Dan Daehyun"

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