Kuo Tian

Dalian University of Technology | DUT · Department of Engineering Mechanics

The Worst Multiple Perturbation Load Approach (WMPLA) has been validated by full-scale tests to be an effective and credible determination method for the lower-bound buckling load of stiffened shells. In spite of its high prediction accuracy and robustness, the large computational time is a burden because this method is based on the large-scale opt...

In order to improve the global optimizing ability of surrogate-based optimizations, an enhanced variable-fidelity surrogate model (VFSM) optimization framework is developed based on the Gaussian process regression algorithm and the fuzzy clustering algorithm, which makes full use of the information fusion of high-fidelity model (HFM) and low-fideli...

Undevelopable stiffened curved shells have been widely used in engineering fields. The shape of the undevelopable curved surface is generally characterized with the non-straight generatrix and variable cross sections, which makes it challenging to automatically model and optimize stiffeners on the undevelopable curved surface. Therefore, the data-d...

This paper provides a novel establishment method of the variable-fidelity surrogate model (VFSM) driven by transfer learning for shell buckling prediction problems such as buckling prediction of variable-stiffness composite shells, aiming at achieving higher prediction accuracy than the traditional VFSM constructed by the bridge function. The trans...

This paper presents a non-uniform curved grid-stiffened shell design method aiming to enhance structural performance using various stiffener patterns, allowing simultaneous optimization of stiffener thickness and stiffener layout. Firstly, the grid-stiffened cell description function is defined using quadratic polynomial functions, comprising the o...

Topology and shape optimization (TSO) is a powerful technique for achieving high-stiffness configurations of stiffened curved shells. However, it presents a challenge to obtain stiffener layouts that satisfy manufacturing constraints using topology optimization (TO) while also considering the changes in the curved shell shape through shape optimiza...

Rotationally periodic stiffened shells have been widely used as load-bearing parts in engineering structures, however, the buckling analysis and optimization of stiffened shells suffer from large computational time owing to the large-scale and complex development tendency of engineering structures. Considering that most of the traditional equivalen...

As one of the most complex and critical components of spacecraft, the structural design of the curved cabin door faces two challenges. On the one hand, it is difficult to obtain innovative configurations for the cabin door in the preliminary design stage. On the other hand, the traditional optimization design algorithm is inefficient in the detaile...

As the key load-bearing component of spacecraft, the strength evaluation of stiffened plate structures faces two challenges. On the one hand, the simulation results are sometimes inaccurate, due to the simplification of the true loading conditions and modeling details. On the other hand, data from the sensors cannot provide the full-field strength...

A fast vibration reduction optimization approach accelerated by the global proper orthogonal decomposition (POD) reduced−order model (ROM) is proposed, aiming at increasing the efficiency of frequency response analysis and vibration reduction optimization of complex thin−walled shells. At the offline stage, the global POD ROM is adaptively updated...

The grid-stiffened shell is a promising aerospace structure configuration with high load-carrying capacity. However, it is challenging to fully exploit its optimal load-carrying efficiency. In this paper, an isogeometric analysis-based optimization framework in which the size and layout of stiffeners can be optimized simultaneously is provided to m...

To accelerate the multi-objective optimization for expensive engineering cases, a Knowledge-Extraction-based Variable-Fidelity Surrogate-assisted Covariance Matrix Adaptation Evolution Strategy (KE-VFS-CMA-ES) is presented. In the first part, the KE-VFS model is established. Firstly, the optimization is performed using the low-fidelity surrogate mo...

The integrally stiffened shells possess the advantages of high specific strength, high specific rigidity and excellent sealing performance, which have been widely used in the load-carrying structure of next-generation manned spacecraft and cargo spacecraft. However, the automatic modelling and optimization of the variable-thickness (VT) integrally...

Deep Neural Network (DNN) is widely used in engineering applications for its ability to handle problems with almost any nonlinearities. However, it is generally difficult to obtain sufficient high-fidelity (HF) sample points for expensive optimization tasks, which may affect the generalization performance of DNN and result in inaccurate predictions...

Purpose The purpose of this paper is to propose a numerical prediction method of buckling loads for shell structures under axial compression and thermal loads based on vibration correlation technique (VCT). Design/methodology/approach VCT is a non-destructive test method, and the numerical realization of its experimental process can become a promi...

Axisymmetric disk structures with complex contour curves are widely used in aero-engines. The shape optimization is generally carried out to reduce the stress level of axisymmetric disks. In this paper, a shape optimization method for axisymmetric disks based on radial basis function (RBF) mesh deformation and Laplace smoothing approaches is propos...

The efficiency as computational efforts and accuracy as optimum design condition are two major changes in hybrid intelligent optimization methods for hierarchical stiffened shells (HSS). In this current work, a novel hybrid optimization coupled by adaptive modeling framework is proposed to improve the accuracy of the predicted optimum results of lo...

To relieve the computational burden and improve the global optimizing ability of Covariance Matrix Adaptation Evolution Strategy (CMA-ES) for real-world expensive problems, an elite-driven surrogate-assisted CMA-ES (ES-CMA-ES) algorithm by the improved Lower Confidence Bound (ILCB) method is proposed in this paper. Firstly, the ILCB method is estab...

As a widely used non-destructive buckling experimental technique, the vibration correlation technique (VCT) is able to determine the buckling load without reaching the collapse point. Following the experimental procedure, the numerical implementation of VCT can be easily realized. That is to say, the numerical VCT (NVCT) can be used for predicting...

Thin-walled structures are commonly utilized in aerospace and aircraft structures, which are prone to buckling under axial compression and extremely sensitive to geometric imperfections. After decades of efforts, it still remains a challenging issue to accurately predict the lower-bound buckling load due to the impact of geometric imperfections. Up...

A novel isogeometric analysis-based stiffness spreading method (IGA-based SSM) is proposed for the truss layout optimization design within a continuum, where the topology, geometry, and cross-sectional areas of the truss elements can be simultaneously optimized. The IGA-based SSM based on energy conservation is employed to obtain the spreading stif...

Stiffened plates are widely used in aerospace structures as load-bearing components. In order to obtain a novel design of stiffened structures with excellent performance, a generative design method of stiffened plates (GDMSP) based on the homogenization method is proposed in this paper, which optimizes the stiffener layout based on an equivalent mo...

The lightweight design of turbine disks is challenging due to the extreme thermomechanical service environment which leads to high stress and temperature-dependency of material properties. The simplified engineering design method which uses uniform material properties at fixed temperature would lead to either unsafe or conservative designs. In this...

An innovative stiffener layout optimization framework is proposed based on the isogeometric analysis-based stiffness spreading method (IGA-based SSM), where the shape and size of stiffeners can be simultaneously optimized. The IGA-based SSM is employed to obtain the stiffness spreading matrices of the stiffeners that are embedded in the flat plate....

In this article, a topology optimization method is proposed to obtain a new preliminary shape design of the twin-web turbine disc considering the burst speed constraint. The burst speed constraint is converted to the constraints on the averaged hoop stress and the maximum averaged radial stress. The linear density filter and Heaviside projection ar...

The Covariance Matrix Adaptation Evolution Strategy (CMA-ES) algorithm is one of the most successful continuous black-box optimization algorithms widely used in many fields. However, the algorithm would be computationally unaffordable due to the sharp increase in dimension and complexity of problems. To improve the computational efficiency and glob...

The topology optimization can be used to obtain preliminary turbomachinery disk designs which meet strength requirement. In order to eliminate enclosed holes which challenge manufacturing processes and to ensure distinct solid-void interface in the optimal result obtained by the topology optimization, a density distribution function is introduced f...

Compared with the traditional design method of composite cylindrical shells with straight fiber laminate, variable stiffness composite cylindrical shells can greatly increase the design space of composite material and thus achieve higher buckling loads by means of the curved fiber laminate. To describe the curved fiber path precisely, it is nec-ess...

As a non-destructive buckling experimental technique, the vibration correlation technique (VCT) is extensively applied in buckling load prediction of columns, plates and shells under axial compression load. Following the experimental steps of VCT, the VCT can be numerically implemented and used as a numerical prediction method for buckling load. Th...

In the cutout reinforcement for a stiffened cylindrical shell, the layout optimization of global stiffeners and the stiffeners around the cutout are generally separated. However, considering the two optimizations separately is noncollaborative. To solve this problem, a global–local collaborative optimization method is proposed. Based on the sequent...

External pressure and axial compression are common load cases for stiffened cylindrical shells in underwater structures. Once these two load cases are combined, the buckling behavior will become quite complex, especially when the external pressure is non-uniform. In this study, the influence of external pressure combined with axial compression on t...

The accurate result of heuristic models combined by social inspired optimization methods is interesting issue for optimizations of hierarchical stiffened shells (HSS). In this paper, six heuristic combined by social-inspired optimization is compared for both ability and accuracy in optimization of load-carrying capacities of HSS. A three level opti...

In order to improve the concentrated force diffusion ability for the connector of spacecraft structures, it is necessary to design concentrated force diffusion on the stiffened curved shell. The traditional radial rib design method generally depends on the design experience and cannot ensure the requirement of efficient concentrated force diffusion...

In practical engineering, the design scheme is generally a compromise solution that meets various requirements. In most cases, the traditional optimization method provides a single optimized solution, which may be prone to fail during the subsequent design stage because some unpredictable requirements may be not considered in the preliminary optimi...

In this paper, a novel implementation of extrusion constraint in topology optimization is proposed based on Helmholtz-type anisotropic filter approach. The main idea is to set a far larger filter feature size along the extrusion direction than other directions, and thus, the density field is kept constant along the extrusion direction. The Helmholt...

Despite numerous studies on vibration reduction techniques for mechanical systems, the expensive computational cost is still a challenging issue for complex structures with a huge number of degrees of freedom. A constructing method of global reduced-order basis (ROB) is proposed in this article by combining proper orthogonal decomposition (POD) wit...

Vibration correlation technique (VCT) is an effective non-destructive buckling experimental technique for shell structures. In this study, VCT is studied from the point-of-view of being a buckling load numerical prediction method by numerically simulating the experimental procedure of VCT. Firstly, the formulas of VCT are introduced for axially loa...

Due to the high specific strength and stiffness, thin-walled shells are widely used in aerospace engineering structures. However, along with the increase of the structure size or the structure hierarchy, the computational cost of the post-buckling analysis of thin-walled shells would increase sharply and then the imperfection sensitivity analysis w...

Since the high-fidelity model (HFM) of hierarchical stiffened shells is time-consuming, the sampling points based on HFM are generally few, which would result in a certain randomness of the sampling process. In some cases, the prediction accuracy of the variable-fidelity surrogate model (VFSM) is prone to be not robust and reliable. In order to imp...

Stiffened shells are widely used in aerospace structures such as launch vehicles and aircraft wings. This paper presents a novel two-scale topology optimization method to design the innovative grid-stiffened pattern for maximizing the critical buckling load of thin-walled cylindrical shells. On the micro-scale, the asymptotic homogenization method...

In order to obtain a precise dynamic structural FE model for dynamic analysis, FE model updating is usually used to correct uncertainty parameters for an initial FE model using incomplete measured data. Despite numerous studies concerning FE model updating, the computational cost is still a challenging issue for the repeated eigenvalue structures....

In this paper, the integrated design of curvilinearly grid-stiffened panels is investigated, including stiffener layout design and profile design. The layout design includes the curvilinear path and non-uniform distribution of stiffeners. Firstly, the path of curvilinear stiffeners is defined by the piecewise linear function, and the non-uniform di...

The hierarchical stiffened shell is one kind of innovative aerospace t hin walled struc tures, which has the advantages of lightweight and high load carrying capacity. Since the stiffener configurations of hierarchical stiffened shells are complex, it would resu lt in the large computational cost of post buckling analysis. In t his case, it is mean...

Hybrid composite materials, which contain more than one type of reinforcing fiber, have been gaining ever-increasing popularity. They can keep superior mechanical properties while greatly reducing the material cost. To fully explore the load-carrying potential, it is crucial to develop a series of corresponding optimization methods for hybrid compo...

The surrogate-based optimization of hierarchical stiffened composite shells against buckling is a typical multimodal and multivariables optimization problem. To improve the computational efficiency and global optimizing ability of the surrogate-based optimization of hierarchical stiffened composite shells, an enhanced variance reduction method base...

For cylindrical shells under axial compression, the essence of initial geometric imperfections is the superposition of local out-of-plane deformations of various forms, which may facilitate the development of buckling deformations, thus leading to a significant knockdown of the load-carrying capacity. It is very challenging for existing methods to...

Stiffened shells have been widely utilized in fuel tanks and launch vehicles because of their high specific stiffness and strength. Since these structures are subjected to complex dynamic loads, reliable prediction of natural vibration characteristics is essential in preventing excessive vibration levels, which may result in failure or very high no...

Due to the high specific strength and stiffness,stiffened shells have been widely used in the high-end equipment of launch vehicles,missiles,aircraft and submarines.Because of their increasing sizes and loads of these equipment,the dimensions of stiffened shells used become larger and larger,and corresponding manufacturing processes and structural...

The concept of a curvilinearly stiffened panel is promising for aerospace and aircraft structures with cutouts, since the stiffness distribution and loading path can be flexibly tailored in terms of cutouts. However, uncertainties from the manufacturing process can significantly reduce the practical load-carrying capacity of a curvilinearly stiffen...

Composite cylindrical shells have been widely used in the fuel tanks of launch vehicles. To reduce the material cost of carbon-fiber-reinforced polymer shells, hybrid fiber composite shells composed of carbon fibers, glass fibers, and an epoxy matrix would be a more promising choice. Along with the development of heavy lift launch vehicles, the dia...

Sandwich-walled cylindrical shell has been built with lattice-like stiffeners by adding another layer of skin in the inner surface of shell. Taking advantage of high mechanical property of lattice-like stiffeners, such as high specific stiffness, high specific strength etc., sandwich-walled cylindrical shell is studied for high load-carrying capaci...

We investigate the effect of thermal stresses on the band structure of elastic metamaterial plates by developing a useful finite-element based method. The thermal field is assumed to be uniform throughout the whole plate. Specifically, we find that the stiffness matrix of plate element is comprised of elastic and thermal stresses parts, which can b...

The energy absorption capacity of origami crash boxes subjected to oblique loading is investigated in the present study. A conventional square tube with identical weight is employed as benchmark. The comparative study reveals that the origami crash box is more desirable than the conventional square tube in most of the range of load angle. A paramet...

In order to improve the post-buckling optimization efficiency of hierarchical stiffened shells, a multilevel optimization framework accelerated by adaptive equivalent strategy is presented in this paper. Firstly, the Numerical-based Smeared Stiffener Method (NSSM) for hierarchical stiffened shells is derived by means of the numerical implementation...

For tailoring the non-uniform axial compression, each sub-panel of stiffened shells should be designed separately to achieve a high load-carrying efficiency. Motivated by the challenge caused by numerous variables and high computational cost, a fast procedure for the minimum weight design of non-uniform stiffened shells under buckling constraint is...

A rapid buckling analysis method is proposed in this paper for large-scale grid-stiffened cylindrical shells used in heavy-lift launch vehicles and large aircrafts. The analysis framework is established by combining asymptotic homogenization method with Rayleigh-Ritz method. A comparison with the buckling load results by smeared stiffener method de...

In order to improve the efficiency of cutout reinforcements, a novel variable cross-section stiffened panel is presented in this paper. Due to the hierarchical characteristic of stiffeners, the development of deformations caused by the cutout is restricted effectively, and then the load-carrying capacity of the stiffened panel increases. Aiming at...

Buckling is usually initiated from a local region near the cutout for cylindrical stiffened shells under axial compression, and then the evolution of buckling waves is governed by the combined effects of local and global stiffness, which limit the load-carrying capacity. Therefore, a simultaneous buckling pattern is crucial for improving the struct...

With regard to future heavy-lift launch vehicles, the buckling analysis and optimization of large-scale stiffened shells by finite element method (FEM) suffer from unbearable computational cost. In spite of the high analysis efficiency, the traditional smeared stiffener method (SSM) is still not accurate enough owing to the assumptions of analytica...

An efficient optimization framework of cylindrical stiffened shells with reinforced cutouts by curvilinear stiffeners is proposed in this study. First, an adaptive method to determine the near field around the cutout and far field away from the cutout is presented. Then, a novel hybrid model is established to reduce the computational efforts of pos...

The influence of imperfection distributions considering manufacturing characters on the buckling response of stiffened shells has not been satisfactorily understood. Stiffened shells with three types of weld lands were established, including axial weld lands, circumferential and sequential axial weld lands, as well as staggered axial weld lands. As...

The motivation of this study is to meet the requirement of cutout reinforcements in aerospace industry by using the design flexibility of curvilinearly stiffened panels. The reason is that the load path and tension field caused by curvilinear stiffeners can increase the load-carrying capacity of stiffened panels. The inherent superiority of such st...

An optimization framework of determining the worst realistic imperfection was proposed by the present authors to study the reduction of the load-carrying capacity of unstiffened cylindrical shells. However, with regard to stiffened shells, especially when cutouts are included, the dimple combination pattern should be judged in a more rational manne...

In this study, a two-stage optimization framework is proposed for cylindrical or flat stiffened panels under uniform or non-uniform axial compression, which are extensively used in the aerospace industry. In the first stage, traditional sizing optimization is performed. Based on the buckling or collapse-like deformed shape evaluated for the optimiz...

Based on the widely used traditional stiffened panel in the field of aerospace, an innovative hierarchical stiffened panel was proposed. By means of dynamic explicit analysis, the ultimate load-carrying capacities of the traditional and hierarchical stiffened panels with equivalent mass subjected to axial compression were investigated via the numer...

A concept of hierarchical stiffened shell is proposed in this study, aiming at reducing the imperfection sensitivity without adding additional weight. Hierarchical stiffened shell is composed of major stiffeners and minor stiffeners, and the minor stiffeners are generally distributed between adjacent major stiffeners. For various types of geometric...

Thin-walled cylindrical shells subjected to axial compression are sensitive to initial geometrical imperfections. Firstly, the influence of a single dimple imperfection on the load-carrying capacity of cylindrical shells is investigated by varying the amplitudes and positions of the dimple imperfection. Thereafter, a surrogate based optimization fr...

Stiffened shells are very sensitive to initial imperfections, especially for geometrical imperfections. In this study, based on a 3-m-diameter orthogrid stiffened shell, post-buckling and imperfection sensitivity analyses are performed by use of explicit dynamic method. Result indicates that stiffened shell with outward hyperbolic generatrix shape...