DESIGN METHODOLOGY FOR MULTIFUNCTIONAL STRESS/STRAIN PERFORMANCES OF MULTI-LOADING SENSORS USING TOPOLOGY OPTIMIZATION
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Date
2022-01-01
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Department
Mechanical Engineering
Program
Engineering, Mechanical
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Distribution Rights granted to UMBC by the author.
Access limited to the UMBC community. Item may possibly be obtained via Interlibrary Loan thorugh a local library, pending author/copyright holder's permission.
Abstract
In 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.