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This work is focused on the structural topology optimization methods related to dynamic responses under harmonic base acceleration excitations. The uniform acceleration input model is chosen to be the input form of base excitations. In the dynamic response analysis, we propose using the large mass method (LMM) in which artificial large mass values are attributed to each driven nodal degree of freedom (DOF), which can thus transform the base acceleration excitations into force excitations. Mode displacement method (MDM) and mode acceleration method (MAM) are then used to calculate the harmonic responses and the design sensitivities due to their balances between computing efficiency and accuracy especially when frequency bands are taken into account. A density based topology optimization method of minimizing dynamic responses is then formulated based on the integration of LMM and MDM or MAM. Moreover, some particular appearances such as the precision of response analysis using MDM or MAM, and the duplicated frequencies are briefly discussed. Numerical examples are finally tested to verify the accuracy of the proposed schemes in dynamic response analysis and the quality of the optimized design in improving dynamic performances. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a Kreisselmeier–Steinhauser (KS) function based adaptive constraint aggregation approach. It is implemented within the integrated layout and topology optimization of multi-component structure systems to avoid using large numbers of non-overlapping constraints defined by means of the previously proposed finite circle method (FCM). An improved adaptive approach is then put forward to obtain proper aggregation parameters for the KS function based constraint aggregation, contributing to less numerical difficulties while meeting the same aggregation precision compared with the existing adaptive approach. Furthermore, the complex step derivative approximation is utilized to yield better sensitivities for the aggregated constraint functions with high nonlinearity. Moreover, during the integrated layout and topology optimization, multi-point constraints (MPC) are applied to establish the interconnections between movable components and supporting structures, which can use fixed finite element meshes and analytical sensitivities. Finally, some numerical examples are tested to demonstrate the validity and effectiveness of the proposed formulation. [ABSTRACT FROM AUTHOR]

Abstract: This paper demonstrates a topology optimization method for the large scale stretch-forming die design. The implementation of the topology optimization depends on the surface loads obtained from the numerical simulation of the sheet metal stretch-forming process. Typically, the design variables are defined based on a linear interpolation to generate directional structures satisfying the manufacturing requirement. To further validate the design procedure, mathematical derivations have proved that the design sensitivities are strictly continuous. More explanations and numerical tests are presented to show the variation of the surface loads versus the stiffness of the die. A stretch-forming die design example is solved on account of gravity and surface loads. The final solution is compared with the traditional design. The numerical results have shown that the topology design can improve the stiffness and strength of the stretch-forming die significantly. [Copyright &y& Elsevier]

This work is focused on the topology optimization of structures that are subjected to harmonic force excitation with prescribed frequency and amplitude. As an important objective of such a design problem, the natural resonance frequency of the structure is driven far away from the prescribed excitation frequency for the purpose of avoiding resonance and reducing the vibration level. Therefore when the excitation frequency is higher than the natural resonance frequency of the structure, the natural resonance frequency will decrease, then the optimum topology configuration will be distorted with large amount of gray elements. A MAC (Modal Assurance Criteria) based excitation frequency increasing method is proposed to obtain a desired configuration. MAC is adopted here to track the natural resonance frequency which can provide the baseline reference for the current excitation frequency during the optimum iterative procedure. Then the excitation frequency increases progressively up to its originally prescribed value. By means of numerical examples, the proposed formulation can generate effective topology configurations which can avoid resonance.

This paper addresses a structure design competition based on topology optimization and 3D Printing, and proposes an experimental approach to efficiently and quickly measure the mechanical performance of the structures designed using topology optimization. Since the topology optimized structure designs are prone to be geometrically complex, it is extremely inconvenient to fabricate these designs with traditional machining. In this study, we not only fabricated the topology optimized structure designs using one kind of 3D Printing technology known as stereolithography (SLA), but also tested the mechanical performance of the produced prototype parts. The finite element method is used to analyze the structure responses, and the consistent results of the numerical simulations and structure experiments prove the validity of this new structure testing approach. This new approach will not only provide a rapid access to topology optimized structure designs verifying, but also cut the turnaround time of structure design significantly.

The purpose of this paper is to give an overall introduction of the structural optimization research works in ESAC group in 2011. Four main topics are involved, i.e. 1) topology optimization with multiphase materials, 2) integrated layout and topology optimization, 3) prediction of effective material properties and 4) composite design. More detailed techniques and some numerical results are also presented and discussed here.

The ceramic-resin composite structure has broad prospects in many fields like rapid casting and thermal protection. Due to the coefficient of thermal expansion (CTE) of resin is about 10 times higher than that of ceramic, the excessive thermal expansion of the resin pattern will lead to the undesirable crack of the ceramic shell during the heating procedure. The proposed approach is to find a reasonable resin configuration minimizing the thermal stress in the ceramic shell. Simultaneously, the mechanical stiffness of the whole structure should be maintained at a certain level to resist the pressure applied on the ceramic shell. In the actual production, the periodic resin configurations are more operable than the disordered configuration, so finding reasonable periodic resin configurations for ceramic-resin composite structure has lots of significance. The purpose of this paper is to introduce the topology optimization method into the periodic resin configuration design for ceramic-resin composite structure. A structural topology optimization procedure in combination with thermo-mechanical finite element analysis has been developed. A single-layer periodic model and a double-layer periodic model are optimized and respective CAD models are rebuilt according to the optimal results. By comparing with the existing hexagonal honeycomb configuration, two optimal designs have shown better performances both in reducing the thermal stress in the ceramic shell and maintaining the stiffness of the whole structure.

The primary purpose of this paper was to present an efficient method to implement the layout design of multi-component systems. In this study, two kinds of design variables: topology variables and geometry variables are simultaneously optimized to maximize the structure stiffness. The multi-point constraints (MPC) are used to simulate the connection behavior between these movable components and supporting structure. So during the optimization iterations, mesh regeneration caused by moving components is avoided compared to the linkage of nodal coincidence. At the same time, the precise geometry shapes and properties of components are maintained to reduce the model building error. At the last of the paper, the numerical example is presented to show the validity of this method.