Search

For effective bone healing, the stiffness of the bone plate should be adjusted to different bone‐healing processes. Thus, the design of stiffness‐changeable structures that take into account the time effect is of importance. To this end, this study introduces a novel topological optimization approach for the composite structural layout design considering material degradation to realize structures with changeable stiffness over time. In this approach, two sets of variables are used: a density field that defines the material layout, and a time field that determines the effect of material degradation on mechanical performance. The continuous degradation update formula is proposed by integrating the Heaviside projected function and Kreisselmeier–Steinhauser function to guarantee its derivability. The objective is to minimize the summed compliance in some specified time steps subject to the constraints of volume fraction. The sensitivity of the aforementioned objective with respect to the design variable is deduced by considering the material degradation over time. The proposed design formulation is general and is demonstrated with several design analyses, considering different fix and degradable interface boundary conditions. Moreover, the results are compared with the results of not considering material degradation and demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Structural dynamic performance of a machine tool greatly affects machining precision and productivity. One effective approach in improving the dynamic performance is by applying topology design optimization to the machine tool structure. However, traditional topology optimization method is hard to implement and does not provide a clear stiffener layout. Furthermore, the topology optimization of certain components does not signify the performance improvement of a holistic machine tool. This paper suggests a new structural dynamic design optimization method for the holistic machine tool. The Adaptive Growth Method which is based on the growth mechanism of natural branch systems is adopted to design the inner stiffener layout of structures, and an optimization strategy for the holistic machine tool utilizing dynamic sensitivity analysis is studied. Both components and contact parts are considered. The dynamic sensitivities of the components are analyzed based on modal test data, and help to determine which components need to be optimized. Then, the headstock, column, and bed are optimized, and the weak contact stiffness is improved. The FEA (finite element analysis) results of an optimized machine tool show that the TCP (tool center point) harmonic displacement is decreased distinctly. To validate the effectiveness of the suggested method, an experiment of the manufactured machine tool structure is conducted, and the experimental results had shown great improvements in the holistic machine tool. [ABSTRACT FROM AUTHOR]

Naturally evolved biological structures exhibit the optimal characteristics of light weight, high stiffness, and high strength. Based on the growth mechanism of biological branch systems in nature, an optimization method for internal stiffener plate distribution in box structures is suggested. Under the given load and support conditions, the internal stiffener plates of machine pedestal structures grow, bifurcate, and degenerate towards the direction of maximum overall structural stiffness in accordance with the adaptive growth law. The optimal and distinct distribution of internal stiffener plates with the most effective load path is thus obtained. Based on this, a size optimization for lightweight design is conducted, in which the self-weight of the structures is taken as the design objective, and the natural vibration frequency and static stiffness in the direction that is sensitive to machining accuracy are set as constraints. Finally, an optimized structure is obtained. The effectiveness of the proposed method is verified by using a precision grinder bed as an example. The results of numerical simulation and 3D-printed model experiment indicate that both the dynamic and the static performance of the optimized structure are improved, while the structural weight is reduced by compared with the initial structure. The suggested design method provides a new solution approach for the design optimization of machine pedestal structures. [ABSTRACT FROM AUTHOR]

Cutting fluid is traditionally used to remove the generated heat during the metal cutting process. Employing cutting fluid outside the cutting tools may result in environmental pollution, health hazards, and other significant negative consequences. Internally cooled cutting tools are thus desirable and promising for the machining industry. In this paper, an internally cooled turning tool is designed based on topology optimization and CFD simulation, followed by solid isotropic material with penalization (SIMP) model imported in mechanical and heat conduction analyzing models for the tool flow channel design and optimization. The mechanical and thermal results are utilized on a traditional tool to formulate a sound topology optimization model of the internally cooled tool. In comparison with the performance of the traditional tool, the newly designed one can greatly reduce the heat as well as the maximum temperature with minimum deformation. Key performance of the newly configured tool, including thermal field distribution, best flow speed, maximum cooling capacity and maximum tool temperature, are simulated under different flow speeds by fluid-structure interaction thermal analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a novel density-based concurrent topology optimization method to support the two-scale design of composite plates for vibration mitigation. To have exceptional damping performance, dynamic compliance of the composite plate is taken as the objective function. The complex stiffness model is used to describe the material damping and accurately consider the variation of structural response due to the change of damping composite material configurations. The mode superposition method is used to calculate the complex frequency response of the composite plates to reduce the heavy computational burden caused by a large number of sample points in the frequency range during each iteration. Both microstructural configurations and macroscopic distribution are optimized in an integrated manner. At the microscale, the damping layer consists of periodic composites with distinct damping and stiffness. The effective properties of the periodic composites are homogenized and then are fed into the complex frequency response analysis at the macroscale. To implement the concurrent topology optimization at two different scales, the design variables are assigned for both macro- and micro-scales. The adjoint sensitivity analysis is presented to compute the derivatives of dynamic compliance of composite plates with respect to the micro and macro design variables. Several numerical examples with different excitation inputs and boundary conditions are presented to confirm the validity of the proposed methodologies. This paper represents a first step towards designing two-scale composite plates with optional dynamic performance under harmonic loading using an inverse design method. [ABSTRACT FROM AUTHOR]

• Topology optimization for designing high broadband damping composite material. • Two competitive frequency-dependent damping materials are adopted in microstructure. • Optimal results with clear topology are obtained by K-S or weighted objective function. • Different connected phase damping material shows different damping properties. The optimization of damping composite material in a certain frequency range has become one of the critical issues in structural engineering applications due to the fact that the structures usually work in a wide vibration frequency range. This paper proposes a topology optimization method for designing the damping composite materials with high stiffness and high broadband damping. The broadband damping composite material is realized by the properly combing two phases of damping material, in which phase 1 has high loss factor in lower frequency range and phase 2 has high loss factor in higher frequency range. In order to maximize the material damping performance in a given frequency range, we suggest a new algorithm for finding the optimal two-phase damping materials layout in micro scales, while the homogenized effective complex elastic matrix is obtained by considering the two damping materials layout in the microstructure. The mathematical model with two different objective functions, which are K-S objective function and weighted objective function, has been established. The first is maximize the minimum material loss factor in the given frequency range and the second is maximize the sum of the material loss factor in the given frequency range. Several typical numerical examples are presented to demonstrate the effectiveness of the proposed optimization method. An in-depth analysis is conducted to reveal the effects of the weighting factor on the optimal solutions. The results show that the K-S function has the ability to maximize the minimum damping of composite material in the given frequency band. The material loss factor increases with the increase of weighting factor. All of the results show that the proposed method can get the optimal microstructure with clearly material layout, no matter the objective is K-S function or weighted function is used. [ABSTRACT FROM AUTHOR]

This work presents a method of designing liquid-cooled heat sink based on topology optimization. First, a multi-objective optimization problem is developed in order to manage the tradeoff between the minimization of fluid power dissipation and the maximization of heat exchange. The novel cooling channels with clear topology information are generated under both uniform single heat and the non-uniform multiple heat load conditions. The effects of initial guess, weighting factor, and Reynolds number on the Pareto optimal solutions are discussed. Next, a full scale 3D conjugate heat transfer numerical simulation model is built to test the flow and thermal performances of the heat sinks. The results show that the optimized cooling channel can achieve a lower thermal resistance and a higher Nusselts number in comparison to the conventional parallel channel. Lastly, the high performance of TO design is validated by conducting experimental tests. • Multi-objective topology optimization is applied to design liquid-cooled heat sinks. • Effects of initial guess, Re, weighting factors on Pareto optimum are discussed. • A detailed thermal analysis is conducted both numerically and experimentally. • Topology optimized designs are successfully benchmarked against parallel channel. This work suggests a design method of liquid-cooled heat sink based on topology optimization. First, a multi-objective optimization problem is developed in order to manage the tradeoff between the minimization of fluid power dissipation and the maximization of heat exchange. The novel cooling channels with clear topology information are generated under both single-uniform and the multiple-non uniform heat source conditions. The effects of initial guess, weighting factor, and Reynolds number on the Pareto optimal solutions are discussed. Next, a full scale 3D conjugate heat transfer numerical model is built to test the flow and thermal performances of the heat sinks. The results show that the optimized cooling channel can achieve a lower thermal resistance and a higher Nusselts number in comparison to the conventional parallel channel, which means the optimal channel can remove more heat energy while the pumping power supply is minimum. Finally, both traditional parallel and topology optimized channel are manufactured by CNC machine and the high performance of the optimally designed heat sink is validated by conducting experimental tests. [ABSTRACT FROM AUTHOR]

In order to study the relationship between the thermal-hydraulic performances and the layout of cooling channels designed by topology optimization from the engineering perspective, two types of topology optimization problems are studied. The first is the flow distribution problem that is to achieve the minimization of power dissipation under the flow rate quality constraints, and the second is the heat exchange maximization problem that is to achieve the optimal thermal performances under the constant input power constraint. Then the optimized heat sinks together with a conventional S-shaped channel heat sinks are manufactured and their thermal-hydraulic performances are investigated both numerically and experimentally. The results reveal that the flow distribution design can provide the lowest hydraulic resistance while the heat exchange maximization design can keep the thermal resistance to a minimum. The proposed design method can be used as a tool to provide cooling solutions to the thermal management of high heat flux electronic components. In order to study the relationship between the thermal-hydraulic performances and the layout of cooling channels designed by topology optimization from the engineering perspective, two types of topology optimization problems are studied. The first is the flow distribution problem that is to achieve the minimization of power dissipation under the flow rate quality constraints, and the second is the heat exchange maximization problem that is to achieve the optimal thermal performances under the constant input power constraint. Then the optimized heat sinks together with a conventional S-shaped channel heat sinks are manufactured and their thermal-hydraulic performances are investigated both numerically and experimentally. The results reveal that the flow distribution design can provide the lowest hydraulic resistance while the heat exchange maximization design can keep the thermal resistance to a minimum. The proposed design method can be used as a tool to provide cooling solutions to the thermal management of high heat flux electronic components. Image 1 • The liquid cooled heat sinks are designed by topology optimization. • Two TO problems are studied: flow distribution and Max. heat exchange. • TO designs are benchmarked against the S-shaped design. • Heat sink prototypes are manufactured and tested numerically and experimentally. • Flow distrib. design provides minimum hydraulic resistance and Max. heat exchange design gives minimum thermal resistance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Time-dependent topology optimization for designing biodegradable composites. • Consideration of material degradation in topology optimization. • Finite element based degradation simulation algorithm is proposed. • Update formula and step-wise sensitivity analysis are proposed for considering material degradation. • Biocomposites design examples and 3D-metal-printed prototypes demonstrated the effectiveness. Biodegradable materials have demonstrated promising potential for the treatment of bone fractures. Therefore, it is crucial to design biodegradable composites considering the degradation effect. Accordingly, to realize a composite material with controlled stiffness at the bone repair stage, this study introduces a novel topological optimization technique for the material layout design in microstructure, considering material degradation. In this approach, two sets of variables are adopted: a density field that defines the material layout, which is also the design variable, and a time field that determines the effect of material degradation on composite material properties. A continuous degradation update formula is proposed by integrating the Heaviside function and the Kreisselmeier–Steinhauser function to guarantee its derivability. The objective of this study was to maximize the material stiffness in some fixed time steps under a specified volume fraction. The sensitivity of the aforementioned objective relative to the design variable was deduced by considering the material degradation over time. The proposed design approach was demonstrated with several design examples, considering different degradable interface boundary conditions. Furthermore, the obtained results were compared with the results obtained without considering material degradation, thereby verifying the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

• Coated structures with layer-wise graded lattice microstructures optimized using the proposed method show higher fundamental eigenfrequency than those with periodic and uniform lattice infill. • Optimized microstructures are well-connectable between neighboring layers and the generated designs can be built out using the additive manufacturing (AM) technique. • Owing to the general gradient-based algorithms, the proposed approach can handle multiple constraints efficiently. • The modal assurance criterion (MAC) method in the proposed framework is able to treat the fundamental eigenfrequency and its eigenvector more accurately, which leads to great iteration convergence. Combining the advantages of lattice infill and coating, coated structures with lattice infill are widely used in engineering to achieve light-weight structural characteristic or certain functionalities. This paper presents a novel concurrent multiscale topology optimization (TO) framework to maximize the fundamental eigenfrequency of structures with a uniform outer coating and layer-wise graded lattice infill microstructures. The macroscale topology optimization is conducted by using the velocity field-based level set method, which inherits the implicit geometrical representation and signed distance property of the conventional level set method (smooth and clear boundaries and well-maintenance of the uniform thickness of the coating). Besides, the employment of general mathematical programming algorithms enables the velocity field-based level set method to handle multiple constraints in an easier way. At microscale, the popular density-based method is used to design layer-wise graded lattice structures. The effective material properties of microstructures are computed by using the asymptotic homogenization method, which bridges macroscale and microscale designs. With higher design flexibility, it is found that coated structures with layer-wise graded lattice infill have higher eigenfrequencies than those with periodic and uniform lattice infill microstructures. The influence of layers of lattice infill and coating thickness on the concurrent optimization of macrostructures and microstructures are carefully studied by showcasing several numerical examples, and the effectiveness of the proposed method is also confirmed, as well as the manufacturability of optimization results. [ABSTRACT FROM AUTHOR]