Browsing by Author "Sung, Myung Kyun"
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Item DESIGN METHODOLOGY FOR MULTIFUNCTIONAL STRESS/STRAIN PERFORMANCES OF MULTI-LOADING SENSORS USING TOPOLOGY OPTIMIZATION(2022-01-01) Sung, Myung Kyun; Lee, Soobum; Mechanical Engineering; Engineering, MechanicalIn this thesis, topology optimization formulations for multi-component force transducers are proposed. The multi-component sensor structure requires to the transducer to respond to a specific force component by decoupling the responses by the other force components. topology optimization is a method that generates an optimal concept design of a structure without preliminary knowledge and design experience. This thesis suggests topology optimization formulations to develop a new conceptual design of the axial section of a internal wind tunnel balance which is one type of multi-component force sensor. Strain gauges are used in the sensor structure to measure the local stress/strain and connected to Wheatstone bridge circuit, so the design problem should be formulated considering local stress (maybe note that stress and strain will be used interchangeably given that we are operating in the elastic range of the material) responses. In the design formulation, three stress requirements are formulated: (1) substantial sensor reading by axial force; (2) suppressed sensor reading by the other forces; and (3) maximum von-Mises stress criterion by the combined loading for structural safety. Sensor performances are measured using directional stress under corresponding loading components and the maximum von Mises stress of the structure is evaluated using normalized P-norm stress to assure structural safety. The manufacturability of the topology optimized designs are improved using the robust approach that helps to remove the grey area and provides a blue-print design. Three different design formulations are proposed for the wind tunnel balance. First, a horizontal symmetry plane is introduced within the topology optimization formulation to utilize the cancellation effect of the Wheatstone bridge circuit. The sensor performances under the axial load and structural safety are formulated for the design condition. Second, asymmetric design condition is considered for the wind tunnel balance. Since asymmetric condition does not guarantee cancellation effect under the normal loading, optimization formulation considers restriction of sensor reading under the normal and pitching moment. To secure the gauge length, passive element setup is applied to the design condition. Supplementary optimization is performed to obtain joints geometry information from topology optimized results. Experimental validation results show acceptable agreement with the finite element analysis results. Lastly, different polarities of normal and pitching moment are considered in the design formulation and aa vertical symmetry plane is introduced within the topology optimization formulation to make the design inherently more robust to the polarity changes. Different sensor locations are investigated and classified into three categories based on the working mechanism.Item Influence of topology optimization parameters on the mechanical response of an additively manufactured test structure(Elsevier, 2023-04-12) Sung, Myung Kyun; Schwerin, Matthew; Badhe, Yutika; Porter, DanielTopology Optimization (TO) determines a material distribution within a domain under given conditions and design constraints, and generally generates complex geometries as a result. Complementary to TO, Additive Manufacturing (AM) offers the ability to fabricate complex geometries which may be difficult to manufacture using traditional techniques such as milling. AM has been used in multiple industries including the medical devices area. Hence, TO may be used to create patient-matched devices where the mechanical response is catered to a particular patient. However, during a medical device regulatory 510(k) pathway, demonstrating that worst-cases are known and tested is critical to the review process. Using TO and AM to predict worst-case designs for subsequent performance testing may be challenging and does not appear to have been thoroughly explored. Investigating the effects of TO input parameters when AM is employed may be the first step in determining the feasibility of predicting these worst-cases. In this paper, the effect of selected TO parameters on the resulting mechanical response and geometries of an AM pipe flange structure are investigated. Four different input parameters were chosen in the TO formulation: (1) penalty factor, (2) volume fraction, (3) element size, and (4) density threshold. Topology optimized designs were fabricated using PA2200 polyamide and the mechanical responses (reaction force, stress, and strain) were observed through experiments (universal testing machine and 3D Digital Image Correlation) and in silico environments (finite element analysis). In addition, 3D scanning and mass measurement were performed to inspect the geometric fidelity of the AM structures. A sensitivity analysis is performed to examine the effect of each TO parameters. The sensitivity analysis revealed mechanical responses can have non-monotonic and non-linear relationships between each tested parameter.