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AbstractThis article proposes an enhanced proportional topology optimization (EPTO) method to solve the structural topology optimization problem of minimizing compliance under material volume constraints. In the proposed method, a new filtering weight function based on the improved Heaviside threshold function is adopted to filter element density during the optimization process. The optimization process of the EPTO method consists of an inner loop and an outer loop. In the inner loop, density distribution is modified in combination with a new filtering weight function. By locally averaging the weighted element compliance, an improved density distribution function in the inner loop is put forward to make the topology configuration of the optimized structure more reasonable. In addition, the projection method is used to reduce the number of intermediate density elements, thereby obtaining optimization results with clear boundaries. In the outer loop, a new termination criterion is adopted, which terminates the optimization process by determining that the relative error of the objective function in several consecutive iterations is less than the specified value. The effectiveness and efficiency of the proposed method are demonstrated through several numerical examples involving two-dimensional (2D) and three-dimensional (3D) topology optimization problems. The results of numerical examples show that the proposed method can not only accelerate the convergence of optimization iterations, but also obtain optimized structures with smaller objective function values and better topology configurations. HIGHLIGHTSA new density filtering weight function is proposed based on an improved Heaviside threshold function.An improved inner loop density distribution formula is proposed by combining a new filtering weight function.Using projection based methods to suppress the appearance of intermediate density elements.Verify the effectiveness of the proposed algorithm by comparing the optimization results with existing algorithms such as top88 and PTO.A new density filtering weight function is proposed based on an improved Heaviside threshold function.An improved inner loop density distribution formula is proposed by combining a new filtering weight function.Using projection based methods to suppress the appearance of intermediate density elements.Verify the effectiveness of the proposed algorithm by comparing the optimization results with existing algorithms such as top88 and PTO. [ABSTRACT FROM AUTHOR]

Attaching viscoelastic materials (VEMs) to structures has been widely used to improve structural dynamic properties. Nevertheless, the adhesion of VEMs inevitably leads to the increase in overall structural mass. Topology optimization is one of the most effective methods to tackle this contradiction. In the traditional topology optimization, VEMs damping cores in constrain layer damping (CLD) sandwich structures are often simplified into linear elastic materials with constant parameters, usually ignoring their frequency-dependent and temperature-dependent dynamic characteristics, which will cause the distortion of the optimization results. Therefore, we propose a topology optimization method for CLD sandwich panels with a frequency-dependent VEM damping core considering steady-state free vibration in this study, where the anelastic displacement fields (ADF) model is adopted to combine the derived frequency-dependent complex constitutive relationship with the layerwise finite element (LFE) model, and the iterative modal strain energy (IMSE) method is used to determine the modal parameters of the CLD sandwich panels. The results of numerical examples show that the proposed method in this study not only has the advantages of simple and intuitive model, high calculation efficiency, and accuracy but also can achieve relatively good dynamic properties of the CLD sandwich structures. [ABSTRACT FROM AUTHOR]

We propose a polygonal topology optimization method combined with the alternating active-phase algorithm to address the multi-material problems. During the process of topology optimization, the polygonal elements generated by signed distance functions are utilized to discretize the structural design domain. The volume fraction of each material is considered as a design variable and mapped to its corresponding element variable through a filtering matrix. This method is used to solve a multi-material structural topology optimization problem of minimizing compliance, in which a descriptive model is established by using the alternating active-phase algorithm and the solid isotropic microstructure with penalty theory. This method can accomplish the topology optimization of multi-material structures with complex curve boundaries, eliminate the phenomena of checkerboard patterns and a one-node connection, and avoid sensitivity filtering. In addition, this method possesses fine numerical stability and high calculation accuracy compared to the topology optimization methods that use quadrilateral elements or triangle elements. The effectiveness and feasibility of this method are demonstrated through several commonly used and representative numerical examples. [ABSTRACT FROM AUTHOR]

We propose an asymptotic concentration approach combined with isogeometric analysis (IGA) for the topology optimization of two-dimensional (2D) linear elasticity structures under the commonly-used framework of the solid isotropic materials and penalty (SIMP) model. Based on the SIMP framework, the B-splines are used as basis functions to describe geometric model in structural finite element analysis, which closely combines geometric modeling with structural analysis. Isogeometric analysis is utilized to define the geometric characteristics of the 2D linear elasticity structures, which can greatly improve the calculation accuracy. In addition, to eliminate the gray-scale intervals usually caused by the intermediate density in the SIMP approach, we utilize the asymptotic concentration method to concentrate the intermediate density values on either 0 or 1 gradually. Consequently, the intermediate densities representing gray-scale intervals in topology optimization results are sufficiently eliminated by virtue of the asymptotic concentration method. The effectiveness and applicability of the proposed method are illustrated by several typical examples. [ABSTRACT FROM AUTHOR]

The solid isotropic microstructure with penalization (SIMP) model is widely used in structural topology optimization. When the optimality criterion (OC) method is used for solving the SIMP model, the optimization solution process not only has relatively low computational efficiency, but also causes a large number of grey-scale elements in the obtained structure. To enhance the computational efficiency, an advance and retreat golden searching scheme is proposed to update the Lagrange multiplier, thereby improving the OC method for solving the SIMP model. To eliminate the grey-scale elements and also to enhance the computational efficiency, the improved OC method combined with the tanh-based density filtering is proposed for solving the SIMP model of structural topology optimization. Furthermore, the improved OC method combined with the sigmoid-based Heaviside density filtering is proposed for solving the SIMP model of multi-material structural topology optimization to eliminate the grey-scale elements and to enhance the computational efficiency. [ABSTRACT FROM AUTHOR]

We propose a parameterized level set method (PLSM) for structural topology optimization based on reaction diffusion equation (RDE) and fuzzy PID control algorithm. By using the proposed method, the structural compliance minimization problem under volume constraints is studied. In this work, the RDE is used as the evolution equation of level set function, and the topological derivative of the material domain is used as the reaction term of the RDE to drive the evolution of level set function, which has little dependence on the initial design domain, and can generate holes in the material domain; the compactly supported radial basis function (CS-RBF) is used to interpolate the level set function and modify the RDE, which can improve the computational efficiency, and keep the boundary smooth in the optimization process. Meanwhile, the fuzzy PID control algorithm is used to deal with the volume constraints, so that the convergence process of the structure volume is relatively stable. Furthermore, the proposed method is applied to 3D structural topology optimization. Several typical numerical examples are provided to demonstrate the feasibility and effectiveness of this method. [ABSTRACT FROM AUTHOR]

A level-set based multi-material topology optimization method using a reaction diffusion equation is proposed in this paper. Each phase is represented by a combined formulation of different level set functions. This description model is modified from Multi-Material Level Set (MM-LS) topology description model. With a total number of M level set functions, this approach provides a representation of M materials and one void phase (totally M + 1 phases). By this approach, the mathematic model of the multi-material topology optimization problem using a reaction diffusion equation is established. With this model, the geometrical complexity of optimal solutions can be easily controlled by appropriately setting a regularization parameter. Some implementation details for solving this model are also presented in this paper. Finally, several typical numerical examples are shown to confirm the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, four groups of shape memory composites with carbon fiber mass fraction of 28.09%, 41.87%, 53.20%, and 63.80% were prepared by vacuum infiltration hot-press forming experimental system. The effect of carbon fiber mass fraction on the shape memory properties of shape memory composites was studied. The results showed that the shape fixed rate and the shape recovered speed of composite decreased with the increase of carbon fiber mass fraction. The shape recovered rate and the maximum recovered force first increased and then decreased, and the shape recovered time increased gradually. [ABSTRACT FROM AUTHOR]

Graphene oxide-carbon fiber hybrid reinforced shape memory composites were prepared by vacuum infiltration hot-press forming experimental system. The effects of fiber stacking methods on the shape memory properties of the composites were investigated. The results showed the shape fixed rate of the composites increased and the shape recovered rate decreased with the decrease of X-direction fiber layers. The composite of XXXXX stacking method due to the greater recovery driving force provided by the fiber in the X-direction. The maximum shape recovered rate was 94.04%. When the fiber layers were all Y-direction, the shape fixed rate of the composite was 98.96%. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new method for the dynamic response analysis of linear stochastic truss structures under stationary random excitation. Considering the randomness of the structural physical parameters and geometric dimensions, the computational expressions of the mean value, variance and variation coefficient of the mean square value of the structural displacement and stress response under the stationary random excitation are developed by means of the random variable''s functional moment method and the algebra synthesis method from the expressions of structural stationary random response of the frequency domain. The influences of the randomness of the structural physical parameters and geometric dimensions on the randomness of the mean square value of the structural displacement and stress response are inspected by the engineering examples. [Copyright &y& Elsevier]

Considering the randomness of structural damping, physical parameters of structural materials, geometric dimensions of active bars and passive bars, applied loads and control forces simultaneously, the problems of dynamic response analysis of closed-loop control system based on probability for the random intelligent truss structures are studied in this paper. The computational expressions of numerical characteristics of structural dynamic response of closed-loop control system are derived by means of the mode superposition method. Through the engineering examples, the influences of the randomness of them on structural dynamic response are inspected and some significant conclusions are obtained. [Copyright &y& Elsevier]