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Topology Optimization Method of Structures with Surface Corrosion Considered

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Acta Mechanica Solida Sinica 2023年第2期36卷 241-253页

作者： Ran Li shutian liu State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116024China

Engineering equipment served in harsh environments for a long time will inevitably corrode,resulting in a loss of mechanical performance and a reduction in a lifetime,and even threatening production *** conventional post-treatment anti-corrosion technologies can slow down the corrosion rate,it is important to consider the corrosion effect on the structural performance in *** paper proposes a topology optimization method with prior consideration of structural corrosion resistance during the design phase,so the structures designed by the approach can have excellent corrosion resistance,considerably reducing the cost of post-treatment anti-corrosion ***,an erosion-based method is utilized to identify the structural surface *** the procedure,the initial structure is eroded to generate a reduced-scale eroded structure,and then,the eroded regions are specified as the surface ***,dual-material interpolation is used to create the corrosion model by modifying the material properties of elements on the structural surface layer,which is set to 0 to simulate uniform ***,the topology optimization method with structural surface corrosion considered is enforced through a two-step filtering/projection *** the entire lifetime corrosion analysis,various numerical examples indicate that the structural performance of the proposed method is superior to that of the standard method(SIMP interpolation)without considering the influence of corrosion,demonstrating the effectiveness of the proposed method.

关键词： Topology optimization Corrosion resistance Surface layer identification Surface corrosion

TOPOLOGY DESCRIPTION FUNCTION BASED METHOD FOR MATERIAL DESIGN

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Acta Mechanica Solida Sinica 2006年第2期19卷 95-102页

作者： Cao Xianfan liu shutian State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanics Dalian University of Technology Dalian 116024 China

The purpose of this paper is to investigate the application of topology description function （TDF） in material design. Using TDF to describe the topology of the microstructure, the formulation and the solving technique of the design problem of materials with prescribed mechanical properties are presented. By presenting the TDF as the sum of a series of basis functions determined by parameters, the topology optimization of material microstructure is formulated as a size optimization problem whose design variables are parameters of TDF basis functions and independent of the mesh of the design domain. By this method, high quality topologies for describing the distribution of constituent material in design domain can be obtained and checkerboard problem often met in the variable density method is avoided. Compared with the conventional level set method, the optimization problem can be solved simply by existing optimization techniques without the process to solve the ＇Hamilton-Jacobi-type＇ equation by the difference method. The method proposed is illustrated with two 2D examples. One gives the unit cell with positive Poisson＇s ratio, the other with negative Poisson＇s ratio. The examples show the method based on TDF is effective for material design.

关键词： topology optimization topology description function material design

Topology Optimization Method for Microscale Structures Described with Integral Nonlocal Theory

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Acta Mechanica Solida Sinica 2024年第1期37卷 63-71页

作者： Jiayu Li Quhao Li shutian liu State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDalian University of TechnologyDalian 116024China

The integration of additive manufacturing and topology optimization makes it possible to fabricate complex configurations,especially for microscale structures,which can guarantee the realization of high-performance structural ***,topology results often contain microstructures(several multicellular scales)similar to the characteristic length of local macrostructures,leading to errors in structural performance analysis based on classical ***,it is necessary to consider the size effect in topology *** this paper,we establish a novel topology optimization model utilizing the integral nonlocal theory to account for the size *** approach consists of an integral constitutive model that incorporates a kernel function,enabling the description of stress at a specific point in relation to strain in a distant *** optimization structures based on nonlocal theory are presented for some benchmark examples,and the results are compared with those based on classical medium *** material layout exhibits significant differences between the two approaches,highlighting the necessity of topology optimization based on nonlocal theory and the effectiveness of the proposed method.

关键词： Topology optimization Microstructures Integral nonlocal theory Size effect

Enhanced Natural Convection for Accelerating Melting of Phase Change Material in Cellular Structure through Inserting Fin

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Journal of Thermal Science 2024年第2期33卷 548-563页

作者： KONG Dekui ZHANG Yongcun liu shutian State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDalian University of TechnologyDalian116024China

The design of thermal conductivity enhancers(TCE) is quite critical to overcoming the disadvantage of the poor thermal conductivity of phase change materials(PCM).The main contribution of this study is firstly to discuss how to actively enhance natural convection of the melted PCM in cellular structure by the fin formed in the structure under the condition of the same metal mass,apart from simultaneously improving heat conduction,which can boost the heat transfer ***,a tailored hybrid fin-lattice structure(HFS) as TCE is designed and fabricated by additive manufacturing(AM).A two-equation numerical method is applied to study the heat transfer of the PCM,and its feasibility is validated with the experimental *** numerical results indicate that enhanced natural convection and improved heat conduction can be obtained simultaneously when a well-designed fin is embedded into a lattice *** enhanced natural convection results in the improved melting rate and the decreased wall temperature;e.g.,the complete melting time and the wall temperature are reduced by 11.6% and 19.7%,respectively,because of the fin for metal ***,the parameters of HFS including the porosity,pore density,and fin dimension have a great impact on the heat *** enhancement effect of the fin for HFS on the melting rate of the PCM increases as the thermal conductivity of the base material *** example,when the fin is introduced into the lattice structure,the complete melting time is reduced by 24.1% for metal *** summary,this study enables us to obtain a good understanding of the mechanism of the heat transfer and provides necessary experimental data for the structural design of HFS fabricated by AM.

关键词： natural convection heat transfer enhancement phase change material additive manufacturing hybrid fin-lattice structure

A Thermal-Solid–Fluid Method for Topology Optimization of Structures with Design-Dependent Pressure Load

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Acta Mechanica Solida Sinica 2022年第6期35卷 901-912页

作者： Huixin Huang Jingyu Hu shutian liu Yang liu State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian116024China College of Transportation Engineering Dalian Maritime UniversityDalian116026China

For the topology optimization of structures with design-dependent pressure,an intuitive way is to directly describe the loading boundary of the structure,and then update the load on ***,boundary recognition is usually cumbersome and ***,the pressure is always loaded either outside or inside the structure,instead of ***,the inner enclosed and outer open spaces should be distinguished to recognize the loading *** handle the above issues,a thermal-solid–fluid method for topology optimization with design-dependent pressure load is proposed in this *** this method,the specific void phase is defined to be an incompressible hydrostatic fluid,through which the pressure load can be transferred without any needs for special loading surface *** nonlinear-virtual thermal method(N-VTM)is used to distinguish the enclosed and open voids by the temperature difference between the enclosed(with higher temperature)and open(with lower temperature)voids,where the solid areas are treated as the thermal insulation material,and other areas are filled with the self-heating highly thermally conductive *** mixed displacement–pressure formulation is used to model this solid–fluid *** method is easily implemented in the standard density approach and its effectiveness is verified and illustrated by several typical examples at the end of the paper.

关键词： Topology optimization Design-dependent pressure load Nonlinear-virtual thermal method Mixed form

A novel parameterization method for the topology optimization of metallic antenna design

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Acta Mechanica Sinica 2017年第6期33卷 1040-1050页

作者： Qi Wang Renjing Gao shutian liu School of Automotive Engineering Dalian University of Technology Dalian 116024 China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian 116024 China

In this paper, based on a tangential interpolation function and an adaptively increasing penalty-factor strategy(TIPS), a novel parameterization method with a self-penalization scheme aimed for the topology optimization of metallic antenna design is proposed. The topology description is based on the material distribution *** proposed tangential interpolation function aims to associate the material resistance with design variables, in which the material resistance is expressed in the arctangent scale and the arctangent resistance is interpolated with the design variables using the rational approximation of material properties. During the optimization process, a strategy with an adaptively increasing penalty factor is used to eliminate the remaining gray scale elements, as illustrated in examples,in the topology optimization based on the proposed tangential interpolation function. Design results of typical examples express the effectiveness of the proposed TIPS parameterization.

关键词： Topology optimization Resistance sheets Metallic antenna design Antenna efficiency

A Gradient-Based Optimization Method for the Design of Layered Phononic Band-Gap Materials

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Acta Mechanica Solida Sinica 2016年第4期29卷 429-443页

作者： Yu Huang shutian liu Jian Zhao State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering MechanicsDalian University of Technology

Phononic materials with specific band-gap characteristics at desired frequency ranges are in great demand for vibration and noise isolation, elastic wave filters, and acoustic devices. The attenuation coefficient curve depicts both the frequency range of band gap and the attenuation of elastic wave, where the frequency ranges corresponding to the none-zero attenuation coefficients are band gaps. Therefore, the band-gap characteristics can be achieved through maximizing the attenuation coefficient at the corresponding frequency or within the corresponding frequency range. Because the attenuation coefficient curve is not smooth in the frequency domain, the gradient-based optimization methods cannot be directly used in the design optimization of phononic band-gap materials to achieve the maximum attenuation within the desired frequency range. To overcome this difficulty, the objective of maximizing the attenuation coefficient is transformed into maximizing its Cosine, and in this way, the objective function is smoothed and becomes differentiable. Based on this objective function, a novel gradient-based optimization approach is proposed to open the band gap at a prescribed frequency range and to further maximize the attenuation efficiency of the elastic wave at a specific frequency or within a prescribed frequency range. Numerical results demonstrate the effectiveness of the proposed gradient-based optimization method for enhancing the wave attenuation properties.

关键词： optimization band gap gradient-based optimization two-step optimization approach

MoM-based topology optimization method for planar metallic antenna design

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Acta Mechanica Sinica 2016年第6期32卷 1058-1064页

作者： shutian liu Qi Wang Renjing Gao State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology

The metallic antenna design problem can be treated as a problem to find the optimal distribution of conductive material in a certain domain. Although this problem is well suited for topology optimization method, the volumetric distribution of conductive material based on 3D finite element method (FEM) has been known to cause numerical bottlenecks such as the skin depth issue, meshed 'air regions' and other numerical problems. In this paper a topology optimization method based on the method of moments (MoM) for configuration design of planar metallic antenna was proposed. The candidate structure of the planar metallic antenna was approximately considered as a resistance sheet with position-dependent impedance. In this way, the electromagnetic property of the antenna can be analyzed easily by using the MoM to solve the radiation problem of the resistance sheet in a finite domain. The topology of the antenna was depicted with the distribution of the impedance related to the design parameters or relative densities. The conductive material (metal) was assumed to have zero impedance, whereas the non-conductive material was simulated as a material with a finite but large enough impedance. The interpolation function of the impedance between conductive material and non-conductive material was taken as a tangential function. The design of planar metallic antenna was optimized for maximizing the efficiency at the target frequency. The results illustrated the effectiveness of the method.

关键词： Metallic antenna design Topology optimization Method of moments Resistance sheet Impedance boundary condition

Enhancing buckling capacity of a rectangular plate under uniaxial compression by utilizing an auxetic material

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Chinese Journal of Aeronautics 2016年第4期29卷 945-951页

作者： Zhang Yongcun Li Xiaobin liu shutian State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanics Dalian University of Technology

Auxetic materials have previously been shown to enhance various performances due to its unusual property of becoming fatter when uniaxially stretched and thinner when uniaxially compressed (i.e., the materials exhibit a negative Poisson's ratio). The current study focuses on assessing the potential of an auxetic material to enhance the buckling capacity of a rectangular plate under uniaxial compression. The in-plane translational restraint along the unloaded edges that was often neglected in open literature is taken into consideration in our buckling model proposed in this study. The closed-form expressions for the critical buckling coefficient of the rectangle are provided and the predicted results agree well with those determined by the finite element method. Furthermore, the results indicate that the buckling performance of a rectangular plate under uniaxial compression can be significantly improved by replacing the traditional material that has a positive Poisson's ratio with an auxetic material when there is in-plane translation restraint along the unloaded edges. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd.

关键词： Auxetic material Buckling Elastically restraint Negative Poisson's ratio Optimization