Long Kai

North China Electric Power University | NCEPU · Department of Electrical Power Engineering

Yaw optimization control is recognized as the most effective active wake control strategy for enhancing the overall power generation of wind farms. However, the potential adverse effects of yaw optimization control on the fatigue life of wind turbines remain unclear. This study examined the effect of yaw optimization control on the fatigue life of...

Topology optimization (TO) has experienced substantial progress in both scholarly research and practical engineering applications. Recent years have witnessed extensive research on TO approaches incorporating the fail-safe concept, with a particular emphasis on potential failures. This paper proposes a TO methodology on the offshore wind turbine (O...

Floating platforms are an economical option for offshore energy harvesting in deep water sea. Lightweight design and structural stability are most important concerns in the design of floating foundations under the premise of ensuring load-bearing capacity. Topology optimization has proven to be a successful method for determining the optimal materi...

The ability of the floating offshore wind turbine foundation to withstand harsh wind and wave conditions is intrinsically linked to the meticulousness employed in the design of the mooring system. Therefore, it is vital to conduct research to reveal the variations in sensitivity of new mooring materials parameters and the response characteristics o...

This paper offers an extensive overview of the utilization of sequential approximate optimization approaches in the context of numerically simulated large-scale continuum structures. These structures, commonly encountered in engineering applications, often involve complex objective and constraint functions that cannot be readily expressed as explic...

Offshore wind turbine Tripod structure Fatigue analysis Stress influence matrix Design load case A B S T R A C T Welded features in the tubular joints are one of the most severe sources of fatigue failure in supporting structure for offshore wind turbines (OWTs). Therefore, fatigue resistance becomes a vital design, inspection and maintenance crite...

Wake interaction between floating offshore wind turbines (FOWTs) is complex and necessitates a comprehensive assessment, which is a prerequisite for the yaw misalignment control. However, existing research on the influence of the wake effect on fatigue damage still suffers from unreliable conclusions and incomplete analysis. Consequently, we aim to...

This paper aims to propose a topology optimization method on generating porous structures comprising multiple materials. The mathematical optimization formulation is established under the constraints of individual volume fraction of constituent phase or total mass, as well as the local volume fraction of all phases. The original optimization proble...

Currently, fatigue-resistance topology optimization has received ever increasing attention, in which most of the literature considers this issue as a simple extension of stress-based topology optimization. However, previous approaches may not be applicable when considering general loads, as the conventional uniaxial rainflow counting method, common...

：A fatigue-resistance topology optimization（TO）method based on augmented Lagrange function was proposed，in order to achieve a lightweight design for wind turbine main bearing seats. The quasi-static method was employed to efficiently obtain the time varying stress. Consequently，the cumulative fatigue damage was determined by rain-flow counting. Usi...

Flexible grippers with superior gripping capabilities are essential for carrying objects. Herein, an origami chomper‐based flexible gripper is designed using a combination of the origami technique and a newly developed nonlinear topology optimization method. This novel origami chomper‐based flexible gripper exhibits superior gripping performance, a...

To achieve the lightweight design of the offshore wind turbine（OWT）supporting structures，a topology optimization method for the OWT tripod structure is proposed. Firstly，the optimization problem with the minimum compliance subject to volume fraction is established. The concept design of the tripod structure is performed based on variable density me...

To achieve a design with the desired stiffness, strength, and durability at the component level, topology optimization has been practiced and was effective in the design of sustainable products, by autumnally allocating the available material within the design domain to form the shortest loading path. In the conceptual phase, this paper proposed a...

To realize the conceptual design of multfi- jacket structure for offshore wind turbine (OWT), modal analysis, loadAbstract:calculation, stiffness and strength study of in extreme working conditions were conducted for a 5 M mult-jacket structure wereconducted. Based on its mechanical behavior, a muli-ojective topology optimization (TO) formulationmo...

Topology optimization (TO), a numerical technique to find the optimal material layout with a given design domain, has attracted interest from researchers in the field of structural optimization in recent years. For beginners, open-source codes are undoubtedly the best alternative to learning TO, which can elaborate the implementation of a method in...

This work proposes a non-penalization Smooth-Edged Material Distribution for Optimizing Topology (SEMDOT) algorithm, which is a typical elemental volume fraction-based topology optimization method, by adopting discrete variable sensitivities for solid, void, and assumed boundary elements instead of the continuous variable sensitivities used in the...

To achieve an ideal balance between cost and robustness, reliability and structural safety, this paper presents a unified robust reliability-based topology optimization (RRBTO) approach for continuum structures considering loading uncertainty for the first time. An optimization model of minimizing a linear combination of mean and standard deviation...

This paper incorporates the homogenization theory into non-penalized Smooth-Edged Material Distribution for Optimizing Topology (SEMDOT) algorithm to conduct the design of cellular structures with the maximum shear modulus. The parametric study and comparison with existing results obtained by BESO are carried out. The numerical examples in 2D and 3...

This paper proposes an effective reliability design optimization method for fail-safe topology optimization (FSTO) considering uncertainty based on the moving morphable bars method to establish the ideal balance between cost and robustness, reliability and structural safety. To this end, a performance measure approach (PMA)-based double-loop optimi...

Although the flexible origami gripper can handle a wide range of objects, there is a need for significant further improvement in its gripping performance. This study develops a novel nonlinear topology optimization (NTO) method to enhance the gripping performance of an origami chomper-based flexible gripper. The proposed NTO method incorporates the...

This paper proposes a topology optimization methodology for offshore wind turbine (OWT) jacket structure design in the concept phase. First of all, modal analysis and load calculation of a 5 MW reference OWT are performed. On the basis of finite element analysis, the displacement and von Mises stress of multi-jacket support structures in various ul...

Continuum topology optimization considering the vibration response is of great value in the engineering structure design. The aim of this study is to address the topological design optimization of harmonic excitation structures with minimum length scale control to facilitate structural manufacturing. A structural topology design based on discrete v...

This article proposes an augmented Lagrangian-based topology optimization approach to minimize the volume fraction subject to multiple nodal displacement constraints. The proposed method puts the multiple constraint equations in the objective function and transforms it into a sequence of unconstrained optimization problems. This study explains the...

The objective of this work is to build a useful-response-surface-based reliability design approach for solving stress-constrained optimization problems taking into consideration load uncertainty. To this end, a reliability optimization problem of minimizing the volume fraction while satisfying a global probabilistic stress constraint is formulated,...

The continuum topology optimization method can extensively improve the structural performance from the mechanical essence, which can provide designers with a variety of innovative design candidates. Due to these advantages and significant help to engineering, the continuum topology optimization method has been rapidly developed in recent years. Thi...

Density-based topology optimization algorithms, such as solid isotropic material with penalization (SIMP), pursue solid/void solutions to yield distinct topologies, however blurry or zigzag boundaries are unavoidable. By contrast, newly developed elemental volume fraction based algorithms pursue solid/void grid points, and the intermediate elements...

The extreme deformation control under transient excitation typically takes the forms of bounds in the time domain. These maximum constraints are typically addressed using an aggregation strategy that approximates the upper bound in a differentiable manner. However, the conventional aggregation method exhibits a dependence on specified parameters. I...

Currently, most works on synchronous optimization of composite topology and fiber orientation are all carried out under deterministic conditions, where the influence of uncertain factor on design optimization of fiber-reinforced composite structures is ignored. In this work, an effective probabilistic reliability-based topology optimization (RBTO)...

The existing wind turbine vortex-vibration researohes usually focus on the first-order vortex-induced vibration of the rigid tower regardless of the top mass instead of ignoring. The second-order vortex-induced vibration of the high-flexible tower with top mass is neglected. This study mainly concentrates on the second- order vortex-induced vibrati...

This work integrate functional gradient constraint into multi-material topology optimization for transient heat conduction structure, taking into account the use of ordered rational approximation of material properties to represent the multi-material interpolation model. The optimization objectives modeled by the aggregation function are to minimiz...

Origami-based metamaterial has shown remarkable mechanical properties rarely found in natural materials, but achieving tailored multistage stiffness is still challenging. We propose a novel zigzag-base stacked-origami (ZBSO) metamaterial with tailored multistage stiffness based on crease customization and stacking strategies. A high precision finit...

The effect of power curtailment，which is ignored by the existing fatigue life prediction methods of tower bolt，is considered in this study. Firstly，the time series load of wind turbines under various power curtailment conditions is obtained by GH Bladed software. Secondly，the Schmidt-Neuper algorithm and the linear cumulative damage theory are appl...

Topology optimization is a powerful tool having capability of generating new solution to engineering design problems, while these designs enhance manufacturability and reduce manufacturing costs in a computational setting. Mesh-independent convergence and other techniques have been widely used as topology optimization technique, but they produce gr...

Cellular structure can possess superior mechanical properties and low density simultaneously. Additive manufacturing has experienced substantial progress in the past decades, which promotes the popularity of such bone-like structure. This paper proposes a methodology on the topological design of porous structure. For the typical technologies such a...

This article proposed a methodology that combines two well-known projections and modified density-based optimized techniques in one formulation methodology. This methodology contains an effective explicit geometric entity identified by shape variables that provide easy control in desired particular regions; implicit density-based topological optimi...

Origami-baed metamaterial has shown remarkable mechanical properties rarely found in natural materials, but achieving tailored multistage stiffness is still a challenge. This study proposes a novel zigzag-base stacked-origami (ZBSO) metamaterial with tailored multistage stiffness property based on crease customization and stacking strategies. A hig...

This paper proposes a novel method for the continuum topology optimization of transient vibration problem with maximum dynamic response constraint. An aggregated index in the form of an integral function is presented to cope with the maximum response constraint in the time domain. The density filter solid isotropic material with penalization method...

This article presents a novel formulation for geometric nonlinear topology optimization problems. In practical engineering, maximum deflection is frequently used to quantify the stiffness of continuum structures, yet not applied generally as the optimization constraint in geometrically nonlinear topology optimization problems. In this study, the ma...

Graph theory is a subdivision of discrete mathematics. In graph theory, a graph is made up of vertices connected through edges. Topological indices are numerical parameters or descriptors of graph. Topological index tells the symmetry of compound and helps us to compare those mathematical values, with boiling point, melting point, density, viscosit...

Topological index sometimes called molecular descriptor is a numerical value which associates a chemical composition for correlating chemical structure with numerous physical properties, chemical reactivity, or biological activity. In this paper, we study some topological indices of boron and try to correlate the physicochemical properties such as...

Currently, most works on layout optimization problem of continuum structure embedded with movable holes are all carried out to maximize the stiffness of the overall system. In this work, the embedding problem is solved for minimum stress design for the first time. To this end, we propose an effective hybrid methodology under SIMP-based computationa...

A methodology for achieving the maximum bulk or shear modulus in an elastic composite composed of two isotropic phases with distinct Poisson’s ratios is proposed. A topology optimization algorithm is developed which is capable of finding microstructures with extreme properties very close to theoretical upper bounds. The effective mechanical propert...

This paper proposes a new methodology for continuum topology optimization that is capable of fatigue-resistance design. Firstly, penalized stress is adopted to circumvent the singularity issue. Secondly, another additional penalization formulation of the elemental fatigue damage is proposed. The quasi-static finite element method is performed to ca...

Compared with traditional metal-materials, fiber-reinforced composite materials have better performance in many aspects such as strength, stiffness, and fracture resistance. At present, fiber-reinforced composite materials have been widely used in automotive, aerospace, and other industrial fields. This paper proposes a topology optimization method...

In this article, an explicit topology optimization method is proposed for maximizing the overall stiffness of a multi-material continuum structure embedded with multiple variable-size movable holes based on the Moving Morphable Bars (MMB) method. To this end, multiple sets of morphable bars are used to describe the structural topology of multiphase...

Purpose Negative Poisson’s ratio (NPR) material has huge potential applications in various industrial fields. However, lower Young’s modulus due to the porous form limits its further applications. Based on the topology optimization technique, this paper aims to optimize the structure consisting two isotropic porous materials with positive Poisson’s...

Nowadays, various regions and financial institutions in China are launching a new round of financial innovation in order to gain the next round of competitive advantages. As a pioneer of China’s reform and opening-up, Shenzhen must naturally consider what principles should be followed in financial innovation, what model should be adopted, what timi...

Scientists and researchers are focusing on generation electrical energy using maximum share of renewable energy resources. Wind turbines possess crucial part in generation of electrical energy from renewable energy sources. A lot of research work has been carried out to find out optimum mechanical design of wind turbines specially focused on reduct...

This paper introduces a new formulation of topology optimization for robust design including local failure and load uncertainty. In contrast to most studies, the focus has been on minimizing the total volume with multiple compliance constraints. With the introduction of the reciprocal intermediate variables, the topology optimization problem can be...

In this paper, we develop an efficient diagonal quadratic optimization formulation for minimum weight design problem subject to multiple constraints. An high‐efficiency computational approach of topology optimization is implemented within the framework of approximate reanalysis. The key point of the formulation is the introduction of the reciprocal...

In this paper, we propose a method for stress-constrained topology optimization of continuum structure sustaining harmonic load excitation using the reciprocal variables. In the optimization formulation, the total volume is minimized with a given stress amplitude constraint. The p-norm aggregation function is adopted to treat the vast number of loc...

Purpose The optimal material microstructures in pure material design are no longer efficient or optimal when accounting macroscopic structure performance with specific boundary conditions. Therefore, it is important to provide a novel multiscale topology optimization framework to tailor the topology of structure and the material to achieve specifi...

Structures and/or materials with engineered functionality, capable of achieving targeted mechanical responses reacting to changes in external excitation, have various potential engineering applications, e.g. aerospace, oceanographic engineering, soft robot, and several others. Yet tunable mechanical performance is normally realized through carefull...

Negative Poisson’s ratio (NPR) material attracts a lot of attentions for its unique mechanical properties. However, achieving NPR is at the expense of reducing Young’s modulus. It has been observed that the composite stiffness can be enhanced when blending positive Poisson’s ratio (PPR) material into NPR material. Based on the respective interpolat...

Layout design of multi-component systems has received ever-increasing attention over recent years. However, most of the current literature on the layout design of multi-component systems conducted are all carried out in an implicit way. In this paper, an explicit optimization model based on the moving morphable bars method is proposed. To this aim,...

It is necessary to limit maximum nominal stress for engineering structural design generally, so as to avoid that the failure of fracture or fatigue occurs. Topology optimization approach is a feasible strategy. The conventional bi-evolutionary structural optimization (BESO) method cannot effectively address the topology optimization problem with st...

It is revealed that the local optimum is particularly prone to occur in multi-material topology optimization using the conventional SIMP method. To overcome these undesirable phenomena, reciprocal variables are introduced into the formulation of topology optimization for minimization of total weight with the prescribed constraint of various structu...

Purpose In pure material design, the previous research has indicated that lots of optimization factors such as used algorithm and parameters have influence on the optimal solution. In other words, there are multiple local minima for the topological design of materials for extreme properties. Therefore, the purpose of this study is to attempt differ...

Transient heat conduction analysis involves extensive computational cost. It becomes more serious for multi-material topology optimization, in which many design variables are involved and hundreds of iterations are usually required for convergence. This article aims to provide an efficient quadratic approximation for multi-material topology optimiz...

The present work introduces a novel concurrent optimization formulation to meet the requirements of lightweight design and various constraints simultaneously. Nodal displacement of macrostructure and effective thermal conductivity of microstructure are referred as the constraint functions, which means taking into account both the load-carrying capa...

Most studies on composites assume that the constituent phases have different values of stiffness. Little attention has been paid to the effect of constituent phases having distinct Poisson’s ratios. This research focuses on a concurrent optimization method for simultaneously designing composite structures and materials with distinct Poisson’s ratio...

In topology optimization problems of structures containing multiphase materials, it is common practice to set the volume constraint of each constituent phase or total mass of entire constituent phase constraint to control the final material usage. On the practical engineering background for lightweight design, it is of significance that the minimiz...

This paper introduces a two-scale concurrent topology optimization method for maximizing the frequency of composite macrostructure that are composed of periodic composite units (PCUs) consisting of two isotropic materials with distinct Poisson’s ratios. Interpolation of Poisson’s ratios of different constituent phases is used in PCU to exploit the...