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Energy Harvesting & Design Optimization Lab. |
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University
of Maryland Baltimore County, Dept. of Mechanical Engineering |
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Current Topics
2. Topology/Shape Optimization:
Topology/shape optimization is an important problem in most engineering systems for lightweight, performance enhancement, and cost reduction. EDLab is conducting researches on topology/shape optimization on structural system (e.g. civil structures, aircraft), multiphysical system (e.g. energy harvesting devices). 2.1. Aircraft wing system design: The
proposed research aims at founding a design framework for aircraft subsystem
layout using design optimization methodologies. An aircraft system is very
complex with its various subsystems: control system (flight control, engine
control), fuel system, hydraulic system, and structural system. An advanced
systematic design approach is needed for effective packaging of multiple
subsystems while satisfying load-carrying performance and minimizing weight
for energy efficiency. The proposed design framework provides multiple Pareto
solutions by performing the consecutive two design steps: (i) subsystem allocation, and (ii) structural topology
optimization. In the first step the design problem to allocate each subsystem
is solved considering weight balance and subsystem proximity for the
improvement of system performances such as dynamic stability and operation
costs. Non-intuitive design results can be expected by adapting global
optimization algorithms such as genetic algorithm. Handling multiobjectives, multiple solutions can be obtained in
this step. Topology optimization for structural robustness is performed in
the second step for each solution found in the first step. The design
optimization for the determination of aircraft frame structures is formulated
as compliance minimization problem subject to volume constraint. The
subsystems layout found in the first step provide loading and boundary
conditions and no frame structure is placed in them. Additional constraint on
maintaining the weight balance is included and the corresponding design
sensitivity is formulated. The proposed design framework, the sequential
combination of subsystem layout design and frame structure design, will
provide innovative design insight for complex modern aircraft system. A
design case study for a commercial aircraft wing will be presented.
2.2. Loadpath Design: Many failures in load-carrying structures occur due to error in calculating load path. For example, the certification failure in Boeing 787 assembly was caused by error in estimating load distribution between upper and lower fasteners of the center wingbox. It was also reported that two thirds of missed steady state and dynamic loads cases in Boeing for last 30 years were caused by inadequate load analysis. Even if the external limit loads and design loads are well defined, it is difficult to analyze/evaluate accurate internal loads that are applied various joints of complex systems, which can cause overload and early joint failure. Instead of trying to analyze internal load for a given joint configuration, the main objective of this paper is to design/control internal load path of load-carrying structures using a new topology optimization strategy. A new topology optimization formulation with a local control of interface load is formulated, to minimize the structural volume subject to constraints on the ratio of multiple internal interface loads (or joint loads). The sensitivity analysis on local interface load is performed using the adjoint method. Material penalization is done using the SIMP approach and MMA is used for optimization algorithm. Multiple case studies successfully demonstrated excellent control of local load path for advanced design of aircraft structural systems.
. Sponsors:
2.3. Null balance design: A well designed high precision module makes it possible to estimate the weight in a high resolution. Most of the formerly developed and patented module mechanisms use combination of lever systems to amplify the displacement output and reduce the output force. Former module designs are largely based on experience, and their design optimality has not been guaranteed in terms of kinematic synthesis in the design domain. In this research, we suggest topological formulations for the high precision null balancing module. Object function, constraints and the corresponding sensitivities are formulated for topology optimization. Topological optimal designs are post-processed and its realistic performance is verified.
Sponsors:
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Energy Harvesting & Design Optimization
Lab. University of Maryland Baltimore County,
Dept. of Mechanical Engineering 1000 Hilltop Circle, Baltimore, MD, 21250 © 2013 |
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