Search

There is a difficulty in setting the coordination of over-current protection in the distribution network with distributed power sources and widely laying optical fiber for differential protection in the distribution network， the study on engineering practice of adopting 5G communication in differential protection in the distribution network is tried. Firstly， based on the 5G communication latency measured by the actual device in the URLLC （ultra-reliable and low latency communications） scenario， the form of the latency is analyzed， and the differential protection currentprotection current is chosen according to the current situation that the 5G communication latency occasionally exists the wide range of jitter. On this basis， a technology for constructing communication network based on the topology of distribution network and a construction technology of self-adaption current differential components in the distribution network is proposed. Finally， the current differential protection devices in the distribution network are developed and used in engineering， which proves the feasibility and reliability of the current differential protection in the distribution network based on 5G communication.

Beam features of variable cross-sections are developed in this paper for topology optimization based on feature-driven method. As beam structures are extensively used and mostly hold standard cross-sections in engineering practice, this work is aimed at the simultaneous design of beam layout and beam cross-section. The H-shaped cross-section is taken as general design primitive owing to its flexible evolution into T-shaped, C-shaped, and L-shaped cross-sections. Meanwhile, it is represented by means of the level-set functions (LSFs) with design variables consisting of the beam position, rotation angles, cross-section sizes, and cross-section configurations. Through the continuous change of defined cross-section configuration variables, different specifications of standard cross-sections with normed size values can be obtained and selected from the parts library. Fixed-mesh technique is also implemented for structural analysis and sensitivity analysis. Several numerical examples are presented to demonstrate the effectiveness and merits of the proposed method. [ABSTRACT FROM AUTHOR]

With the rapid development of 3D printing technology, lattice structures have been widely utilized in structural designs aimed at vibration resistance due to their excellent performance. In this study, considering the moderate improvement of vibration suppression property of existing graded lattice, we introduce high-damping material into the optimization framework and further enhance the vibration resistance ability of gradient lattices. This framework extends the existing framework of stiffness and mass distribution to incorporate the distribution of stiffness, mass, and damping, which allows us to consider the damping changes with the cell configuration. Initially, the lattice cells are assigned with two different constitutive materials, one with high stiffness and the other with excellent damping properties. Different from traditional lattice units, we can obtain a series of lattice units with adjustable stiffness , mass and damping in a certain range. Via the homogenization method on the frequency domain, the complex elastic matrices about distribution of these lattice cells controlled by three parameters are obtained. In the meantime, the loss factor of these lattice cells is also obtained. A polynomial-based interpolation technique is employed to characterize the graded lattice units, which is integrated into an optimization process aimed at minimizing the lattice structures' vibration responses. Several numerical examples are presented to illustrate this framework's effectiveness, and experimental tests on 3D printed specimens are conducted to validate the numerical results. It's worth noting that under the condition that the total weight of the structure remains unchanged, this weakens the overall stiffness of the structure (the reduction of first-order natural frequency), but greatly increases the damping of the structure (with a widened resonance peak) to resist the vibration of the structure. For the lattice structures induced by damping materials, the average loss factor is 0.114, which is almost doubled to the average value of those not including the damping material. When comparing the results of the mean displacement amplitude with and without damping materials, the reduction of displacement amplitude of lattice structures is above 25 %. The methodology expands the scope of optimization design for lattice structures, moving beyond stiffness maximization to include vibration mitigation by determining the appropriate distribution of stiff and damping materials, showcasing the practical applicability of the presented methods in engineering practice. ● Dynamic topology optimization approach is developed for gradient lattice filled with damping materials. ● The complex elastic matrix of parameterized lattice filled with damping material is derived. ● Experimental results confirm the significant vibration attenuation by proper introduction of damping materials. [ABSTRACT FROM AUTHOR]

The electromagnetic performance of flight vehicles has been attracting considerable interest in recent years. As one of the important indicators of this performance, radar cross section (RCS) has been extensively studied. A significant limitation on the RCS of flight vehicles lies in the fact that tiny gaps will transform into steps during structural deformation, where the local RCS will be significantly affected. This study investigates a topology optimization method to minimize the RCS of step structures when subjected to external loads. To ensure that the structure discretized by shell elements in the mechanical finite element analysis can still simulate the wave reflection of step structures, artificial step elements are defined to simulate the generation of steps during structural deformation. Then, the conventional method of moments is utilized to calculate the RCS. To implement the gradient-based optimization, the sensitivity of RCS with respect to the design variables is derived analytically by the adjoint method. An extended compliance-based topology optimization is performed to determine a stiffness constraint. Then, together with a structural volume limitation, the average RCS of target incident angles will be set as the object to obtain the structural topology. The superiority compared with the general structural design method and the validity have been demonstrated with numerical examples. [ABSTRACT FROM AUTHOR]

Multidisciplinary topology optimization (TO) for additive manufacturing (AM) exhibits unprecedented design and manufacturing freedom as an effective lightweight methodology. In order to fully utilize the AM advantages of materialized arrangement in spatial and voxel-by-voxel digitalized printing, multidisciplinary TO for AM requires a full understanding of the process-structure-property-performance (PSPP) relationship to establish the quantitative correlation of part property and multiple process factors, including laser-, process-, and material-related parameters. This study incorporates the PSPP relationships of laser sintered material with topology optimizer so as to provide a guideline for TO collaborative AM design. The proposed workflow involves mapping functions of PSPP relationships via a data-driven approach and then optimizes the multiple process parameters and structural topology by the gradient-based algorithm. Compared with conventional optimization approaches, three case-dependent optimizations demonstrate the effectiveness of the proposed approach yielding encouraging improvements of lightweight performance. The multidisciplinary TO can be generally applied to types of AM technologies, establishing a strong linkage of physical product and digital design. [ABSTRACT FROM AUTHOR]

To date, sealing structures have been widely used in aerospace vehicles. This paper presents a normalized and systematic procedure realizing lightweight design for a square bolt-flange sealing structure of a rocket engine. To measure the sealing behavior, the contact force on the sealing interface is obtained by a nonlinear analysis of node-to-node contact. The topology optimization is established to achieve sufficient contact forces in the sealing area by acquiring the Kreisselmeier-Steinhauser (KS) function to condense multiple contact force constraints into a global sealing constraint. A three-field projection scheme is also adopted to obtain a clear result and a semi-analytical perturbation scheme is proposed to realize the sensitivity calculation. Then, the square flange cover is optimized by the proposed optimization framework and a lightweight design with a clear load-carrying path is obtained. The optimized design is reconstructed and further optimized in detail. Compared with several traditional designs, it shows better leakproofness under inner liquid pressure, which can be directly fabricated by additive manufacturing and used in the rocket engine. The optimization procedure is proved effective and practical in designing sealing structures for aerospace vehicles. [ABSTRACT FROM AUTHOR]

This paper presents the topology optimization of hierarchical microtextures for wetting behavior in the Cassie-Baxter mode, considering a structural unit of the hierarchical microtexture composed of base and secondary structures. The geometrical configuration of the considered structural unit can be described as a fiber bundle composed of an external surface of the base structure and the pattern of the secondary structures. Thus, two design variables are defined, one for the external surface of the base structure, and the other for the pattern of the secondary structures. The Young-Laplace equation, including a term depending on the mean curvature of the external surface, is used to describe the liquid/vapor interface imposed with a surface tension in the Cassie-Baxter mode. To overcome the difficulty of numerically computing the second-order derivative of the external surface, two partial differential equation filters are sequentially applied to the design variable of the base structure to ensure the numerical accuracy and feasibility of using an efficient linear-element-based finite element method to solve the Young-Laplace equation. To improve the performance of the hierarchical microtextures, the volume of the liquid bulges suspended at the liquid/vapor interface in the Cassie-Baxter mode, before the transition into the Wenzel mode, is minimized to optimize the match between the external surface of the base structure and the pattern of the secondary structures. In the topology optimization process, penalization of the material density of the surface tension is achieved by an artificial Marangoni phenomenon. In numerical examples, solid surfaces are tiled into textures with axial symmetry, radial symmetry, chirality, and quasiperiodicity; and structural units are derived consisting of base structures with peak shapes and dense secondary structures surrounding the crests of the peaks. The optimized performance of the derived structural units has been confirmed by comparisons. [ABSTRACT FROM AUTHOR]

A B-spline multi-parameterization method (MPM) is presented in this paper for topology optimization of thermoelastic structures. As thermoelastic topology optimization belongs to a kind of design-dependent problems that are complicated to deal with, this method is aimed to solve thermoelastic problems with multiple materials by means of B-spline parameterization that integrates together the recursive multiphase material interpolation (RMMI) and the uniform multiphase material interpolation (UMMI) schemes. The commonly used discrete pseudo-density variables related to the finite element model are thus replaced with continuous pseudo-density fields dominated by control parameters in the B-spline space. In this sense, B-spline multi-parameterization is used for the first time to represent multiple pseudo-density fields and multi-material properties including elasticity matrix and thermal stress coefficient. Compared with traditional pseudo-density method, the current method has the advantage of not only attaining a reduction of design variables in number but also achieving a regularized distribution of pseudo-density fields with a clear material layout over the whole structure domain. Numerical results show that the stable convergences are achieved with the avoidance of gray elements, checkerboards, and multi-material overlapping owing to the high continuity of B-spline preserved for multi-material distributions. Besides, it is found that the RMMI scheme distributes less stiff materials around stiff materials, while the UMMI scheme tends to gather less stiff materials together. [ABSTRACT FROM AUTHOR]

In this paper, a novel multiphase reconfigurable and fault-tolerant drive converter topology is proposed for driver with fail-work capability, and fault-tolerant strategies are proposed for open-circuit and short-circuit faults in the single-phase windings, aiming to improve the motor drive system's fail-work ability in the high reliability applications. The drive converter topology can isolate open-circuit and short-circuit faults in power supplies, power devices, or switches. Then, it can reconfigure the drive circuit topology from independent H-bridge to star type by reconfigurable switches and power devices, according to the fault-type and the fault-tolerant truth tables. After reconfiguration, remedial operation will be utilized for open- and short-circuit faults of windings, so that the motor system has twofold fail-work capabilities in driver and windings. Finally, based on a series of experiments on a transit co-simulation model and test bench, the effectiveness and validity of fault-tolerant capability and the strategies are verified, and has twofold fail-work remedy. [ABSTRACT FROM AUTHOR]

Spatial gradient information of density field in SIMP (solid isotropic material with penalization) topology optimization is very useful for imposing overhang angle and minimum length (size) manufacturing constraints or achieving shell-infill optimization. However, the computation of density gradient is an approximation since the design space is discretized. There are several operators for this purpose, which arise from the image processing field. This note compares different gradient operators in the context of SIMP topology optimization method and suggests a new computation strategy to improve the accuracy of gradient estimation. We take a case study of spatial gradient-based minimum size constraints. New structural indicator functions are proposed to improve the general applicability of previous gradient-based minimum length constraints. This study is carried out in 2D structure examples to validate the methodology. [ABSTRACT FROM AUTHOR]

Summary This work develops a concurrent shape and topology optimization method to solve the design problems of which the pressure loads are applied on designable boundaries. Implicit B‐spline curves including open B‐spline and closed B‐spline are introduced in the form of level‐set functions to act as common design primitives for the description of both moving pressure boundary and inner topology boundaries of a structure. Boolean operations are applied to describe mathematically the shape and topology variations. An artificial nondesignable offset domain of small bandwidth is introduced along the moving pressure boundary to ensure reasonably the imposition of pressure loads on solid materials. The pressure loads are numerically discretized onto the control nodes of finite cell method used for structural analysis with fixed mesh. Sensitivities of design‐dependent pressure loads with respect to both shape and topology design variables are explicitly derived. Numerical problems are finally solved to illustrate the presented method. [ABSTRACT FROM AUTHOR]

Subparts of load carrying structures like airplane windows or doors must be isolated from distortions and hence structural optimization needs to take such shape preserving constraints into account. The paper extends the shape preserving topology optimization approach from simple linear load cases into geometrically nonlinear problems with practical significance. Based on an integrated deformation energy function, an improved warpage formulation is proposed to measure the geometrical distortion during large deformations. Structural complementary elastic work is assigned as the objective function. The average distortion calculated as the integrated deformation energy accumulated in the incremental loading process is accordingly constrained to obtain warpage control. In the numerical implementation, an energy interpolation scheme is utilized to alleviate numerical instability in low stiffness regions. An additional loading case avoids isolation phenomena. Optimization results show that shape preserving design is successfully implemented in geometrically nonlinear structures by effectively suppressing local warping deformations. [ABSTRACT FROM AUTHOR]

In this paper, a new hybrid modulation fault-tolerant control of an open-end winding linear vernier permanent-magnet (OEW-LVPM) motor is proposed. By using a floating capacitor inverter, the proposed OEW-LVPM motor drive can continue operation under open-circuit fault condition. The OEW-LVPM motor fed by dual-inverter system consists of two inverters, which are connected to both ends of the motor windings, including a dc power named as main inverter (MI) and a floating capacitor called as capacitor inverter (CI). When one switch is broken in the CI, the CI topology will be restructured to a three-phase four-switch inverter. Then, an improved six-step modulation is investigated in the MI to reduce the switching frequency, while the conventional modulation is applied in the CI. Thus, the MI can provide all the active power, and the CI is only used to supply the reactive power. The proposed fault-tolerant control method is simulated and the experiments with the OEW-LVPM motor drive are also accomplished to verify the feasibility. [ABSTRACT FROM AUTHOR]

This paper proposes and designs a new five-phase modular flux-switching permanent-magnet (M-FSPM) machine for high reliability applications. The key is the new machine topology which incorporates the concept of fault-tolerant teeth (FTT) to provide the desired decoupling among phases. The electromagnetic performances of the newly designed M-FSPM machines having 18 and 19 rotor poles are quantitatively analyzed including the flux, back-EMF, cogging torque as well as unbalanced magnetic force (UMF). The results show that the proposed M-FSPM machine not only retains the merits of stator-PM machines and multiphase machines, but also offers lower cost and higher fault-tolerant capability. Especially, the 10/19-pole one incorporates the merits of symmetric back-EMF and reduced cogging torque, while suffers from UMF. Two experimental M-FSPM machines are designed and built for exemplification. Experimental results of the prototypes are given to confirm the validity of the proposed machines. [ABSTRACT FROM AUTHOR]

Abstract: Integrated design of the structure topology and involved component layout is a challenging design issue when compared with traditional topology optimization. In this paper, we propose an implicit modeling approach that works completely on an Eulerian finite element mesh throughout the whole optimization process. To this aim, implicit level-set functions and R-functions are employed to describe geometrical shapes of movable components. In particular, a modified arctan function is adopted to depict the material discontinuity along the interface between the structure domain and each component domain. They are then used for material interpolations and analytical sensitivity analysis w.r.t. both pseudo-density design variables and location design variables related to the host structure and components, respectively. Based on a variety of numerical tests, it is demonstrated that considered design problems with movable components can easily be solved by extending the SIMP material model based topology optimization approach using an Eulerian mesh and the gradient-based optimization algorithm. [Copyright &y& Elsevier]

In view of the prohibited computing time and the complexity of design procedure, a superelement formulation (SEF) is proposed to deal with the simultaneous optimization of component placement and the framework topology. In the iterative design process, each component is modelled as a movable superelement so that the sensitivity analysis with respect to the location design variables can be largely simplified by the SEF. Moreover, based on the Kuhn-Tucker optimality condition, two decomposition strategies are developed as variant approaches for the simultaneous design of multi-component system. By means of numerical examples, these approaches are compared to show their capability and efficiency for the system compliance minimization. [ABSTRACT FROM AUTHOR]

In this paper, we propose a B-Spline Offset Feature (BSOF) for feature-driven topology optimization. The feature is inspired from the geometric morphology of worms characterized by an elongated cylindrical, bilaterally symmetric, and well-segmented body along a highly deformable directrix. B-spline is used to define the directrix with its outward and inward offsets outlining the BSOF. This definition endows the BSOF with high deformability such as self-folding and self-intersection. To construct the implicit level-set function (LSF), the BSOF is decomposed into a sequence of segments whose LSFs can easily be constructed by Kreisselmeier–Steinhauser (KS) function. Regular or irregular shaped segments are identified by the deformation gradient. Irregular segments involving geometrical singularities, e.g. distorted and concave segments, are replaced with convex hulls. The stiffest structure design and compliant mechanism synthesis are studied to illustrate the effectiveness and advantages of the proposed BSOF for topology optimization. • Bio-inspired B-Spline Offset Feature (BSOF) is proposed for topology optimization. • The BSOF retains high deformability of self-folding and self-intersection. • The feature segmentation method is developed to construct the LSF of BSOF. • Convex hull replacement of irregular segments can stable the optimization process. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Topology optimisation and stereolithography effective approach to design porous structures. • Functionally graded structures from grey level information as a new approach of multi-criteria design. • Limited resolution for stereolithography to design unit cells below millimetre scale. • Elastic-plastic-damage-densification model to rank polymeric unit cells. • Two examples to show potential of tailoring local performance using varied unit cells. Abstract This work reports an integrated strategy to develop functionally graded materials using additive manufacturing technology. Topology optimisation is exploited to design porous structures with controlled amount and distribution of porosity. Designs are printed using stereolithography and their compression behaviour is determined. Designs are scaled down to form unit cells for functionally graded materials with contrasted mechanical properties. The designed unit cells demonstrate a wide variety of performance, which is achieved when combining topology optimisation and additive manufacturing. The compression performance of designed functionally graded materials exhibits distinctive behaviour depending on the nature and arrangement of unit cells. This study concludes on the high potential of topology optimisation and stereolithography to promote 3D printed designs with property-controlled structures. [ABSTRACT FROM AUTHOR]

In this paper, a feature-driven topology optimization method is developed. This is the first study on layout design of multiple engineering features using level-set functions (LSFs) and Boolean operations. The novelty of this work is threefold. First, multiple engineering features of arbitrary shape are considered as basic design primitives and topology variation is achieved via the layout and shape optimization of the features. Kreisselmeier–Steinhauser (KS) function constructed by means of Boolean operations is adopted as the LSF, which uses an implicit function to ensure a smooth description and topological changes of basic features and the whole structure. Second, using a modified Heaviside function to smooth the void–solid material transition over a fixed computing mesh, a narrow-band domain integral scheme is developed for the efficient sensitivity analysis. Third, the gray material distribution regions at the feature-connecting portions are analyzed and the underlying reason for that is traced to the non-equidistant distribution of level-set contours of specific features. To avoid the gray regions, an approximated signed distance function is proposed to regularize the LSF and KS function. The bounded normalization property of the KS function is highlighted for its construction with the signed distance functions or normalized first-order approximations. Numerical examples are finally tested to demonstrate the validity and merits of the proposed feature-driven topology optimization for complicated design problems. [ABSTRACT FROM AUTHOR]

This paper presents a highly deformable Multi-Section B-Spline Offset Feature (MS-BSOF) for topology optimization. The MS-BSOF is bio-inspired from the geometric morphology of worms which is modeled with a deformable directrix and deformable cross-sections. The directrix is defined by B-spline curve. The cross-section profile in 3D case is determined by a set of control cross-section profiles, each of which is defined as a closed B-spline (CBS) to ensure high deformability. The implicit representations of the proposed 2D and 3D MS-BSOFs are formulated using the level-set function (LSF). To perform topology optimization, a topology variation modeler (TVM) is constructed with the proposed MS-BSOF within a freeform design domain modeler (FDDM). Several numerical examples are presented to demonstrate the effectiveness and merits of the MS-BSOF. • The worm-like highly deformable MS-BSOF is proposed for 2D and 3D topology optimization. • Parametric and implicit representations of the MS-BSOF are developed. • The rotation minimizing frame with minimal twist property is used to define the moving frame of 3D MS-BSOF. [ABSTRACT FROM AUTHOR]

Surface flows can represent the motions of the viscous and incompressible fluid at the solid/fluid interfaces. This paper presents a topology optimization approach for surface flows and extends the design space of topology optimization of fluidic structures onto the curved surfaces in the forms of 2-manifolds corresponding to the geometrical configurations of the solid/fluid interfaces. The presented approach is implemented by filling a porous medium onto the 2-manifolds. An artificial Darcy friction is correspondingly added to the area force term of the surface Navier-Stokes equations used to describe the surface flows and the physical area forces are penalized to eliminate their existence in the fluidic regions and to avoid the invalidity of the porous medium based topology optimization model. Topology optimization for the steady and unsteady surface flows has been executed by iteratively evolving the impermeability of the porous medium, where the impermeability is interpolated by the material density derived from a design variable. The related partial differential equations are solved by using the surface finite element method. Numerical examples have been provided to demonstrate this topology optimization approach for the surface flows, including the boundary velocity driven flows, the area force driven flows and the convection-diffusion flows. [ABSTRACT FROM AUTHOR]

This paper presents a B-spline based topology optimization method to design self-supporting structures for additive manufacturing (AM). The density field of the structure is represented by B-spline parameterization together with Heaviside function through Boolean operation. Two constraints are constructed for overhang control. One concerns the overhang angle constraint to structural boundaries and is formulated in an integral form within a narrowband region identified by the density gradient norm. The density gradient is obtained by directly computing the derivatives of the B-spline density field. The other concerns the constraint to avoid undesired V-shaped areas and is formulated by limiting the density values at detection points uniformly distributed in the design domain. Several examples are dealt with to demonstrate the effectiveness of the proposed method. It is shown that the proposed overhang control scheme is independent of the FE mesh with the help of B-spline parameterization and works well with free-form design domains. • A B-spline based topology optimization method with overhang constraint is proposed. • The density gradient is computed by differentiating directly the B-spline function. • The blurry structural boundary is identified by the density gradient norm. • V-shaped areas are avoided by limiting density values at prescribed detection points. • The method can deal with various critical overhang angles and build directions. [ABSTRACT FROM AUTHOR]

• The moment of inertia constraint is introduced in the rudder design. • The skin compliance is proved more effective in the thermal loading rudder design. • An engineering-oriented post-processing is proposed for additive manufacturing. In high-speed vehicles, rudders often endure both aerodynamic pressure and thermal loads. The innovative design of rudders is of great importance for the performance of the whole vehicle. In this work, thermo-elastic topology optimization is adopted to design a typical all-movable rudder structure. The compliance of the rudder skin is considered to be a new objective and the moment of inertia of the rudder is constrained during optimization to ensure its fast response to instructions of the control system. Then sensitivity analysis of the structural compliance and the moment of inertia is carried out. Optimization results show that thermal load has a great effect on the optimized configuration and minimizing the compliance of the rudder skin gives much better design than minimizing the global compliance. Subsequently, an engineering-oriented post-processing is conducted to make the optimized design suitable for additive manufacturing. An appropriate printing direction is selected based on the layout of the optimized ribs and certain ribs are reshaped with fillets to make the rudder free of internal support structures. Besides, according to a secondary topology optimization of the ribs and the stress distribution, a set of powder-discharge holes are properly opened on the ribs so that all cavities within the rudder are connected and the metal powder inside the rudder can be discharged with little effort after manufacturing. Finally, the optimized design is successfully printed using Selective Laser Melting, demonstrating the proposed post-processing is effective for additive manufacturing. [ABSTRACT FROM AUTHOR]

• A new data-driven topology optimization (DDTO) framework is proposed. • Sensitivity analysis for discrete noisy material data sets is developed. • Verification of the new DDTO framework by truss structure designs. The application of structural topology optimization with complex engineering materials is largely hindered due to the complexity in phenomenological or physical constitutive modeling from experimental or computational material data sets. In this paper, we propose a new data-driven topology optimization (DDTO) framework to break through the limitation with the direct usage of discrete material data sets in lieu of constitutive models to describe the material behaviors. This new DDTO framework employs the recently developed data-driven computational mechanics for structural analysis which integrates prescribed material data sets into the computational formulations. Sensitivity analysis is formulated by applying the adjoint method where the tangent modulus of prescribed uniaxial stress-strain data is evaluated by means of moving least square approximation. The validity of the proposed framework is well demonstrated by the truss topology optimization examples. The proposed DDTO framework will provide a great flexibility in structural design for real applications. [ABSTRACT FROM AUTHOR]