Honeycomb structures of shape memory alloy(SMA)have become one of the most promising materials for flexible skins of morphing aircraft due to their excellent mechanical properties.However,due to the nonlinear material...Honeycomb structures of shape memory alloy(SMA)have become one of the most promising materials for flexible skins of morphing aircraft due to their excellent mechanical properties.However,due to the nonlinear material and geometric large deformation,the SMA honeycomb exhibits significant and complex nonlinearity in the skin and there is a lack of relevant previous research.In this paper,the nonlinear properties of the SMA honeycomb structure with arbitrary geometry are investigated for the first time for large deformation flexible skin applications by theoretical and experimental analysis.Firstly,a novel theoretical model of SMA honeycomb structure considering both material and geometric nonlinearity is proposed,and the corresponding calculation method of nonlinear governing equations is given based upon the shooting method and Runge–Kutta method.Then,the tensile behaviors of four kinds of SMA honeycomb structures,i.e.,U-type,V-type,cosine-type,and trapezoid-type,are analyzed and predicted by the proposed theoretical model and compared with the finite element analysis(FEA)results.Moreover,the tensile experiments were carried out by stretching U-type and V-type honeycomb structures to a global strain of 60%and 40%,respectively,to perform large deformation analysis and verify the theoretical model.Finally,experimental verification and finite element validation show that the curves of the theoretical model results,experimental results,and simulation results are in good agreement,illustrating the generalizability and accuracy of the proposed theoretical model.The theoretical model and experimental investigations in this paper are considered to provide an effective foundation for analyzing and predicting the mechanical behavior of SMA honeycomb flexible skins with large extensional deformations.展开更多
This paper analyzes the random response of structural-acoustic coupled systems. Most existing works on coupled structural-acoustic analysis are limited to systems under deterministic excitations due to high computatio...This paper analyzes the random response of structural-acoustic coupled systems. Most existing works on coupled structural-acoustic analysis are limited to systems under deterministic excitations due to high computational cost required by a random response analysis. To reduce the computational burden involved in the coupled random analysis, an iterative procedure based on the Pseudo excitation method has been developed. It is found that this algorithm has an overwhelming advantage in computing efficiency over traditional methods, as demonstrated by some numerical examples given in this paper.展开更多
Offshore oil and gas development plays an important part in the global energy sector.Offshore platforms and flexible pipes are the key equipments in the whole offshore oil and gas development system.Because of the ran...Offshore oil and gas development plays an important part in the global energy sector.Offshore platforms and flexible pipes are the key equipments in the whole offshore oil and gas development system.Because of the randomness and uncertainty of wave and current loads in the ocean environment,the structural design and mechanical analysis of the marine equipment can be highly complicated.Therefore,this paper reviews the recent works of the theoretical model,numerical simulation,and experimental test in three research areas:hydrodynamic analysis of offshore platforms,structural mechanics analysis of flexible pipe and cable,and monitoring technology of offshore floating structures under marine loads.By analyzing their main research methods and key technical difficulties,this paper provides theoretical basis and technical support for the reliability engineering application of offshore platforms and flexible pipelines.Also,China is relatively backward in the design of marine floating platform,the design,analysis and testing of flexible pipeline and cable,as well as the marine equipment prototype monitoring technology research.Calling for breakthroughs at the earliest possible stage in the above fields,prime research should be focused on and strategic planning should be made to deal with“key areas and stranglehold problems”.It is of great significance for the development of China's deep-sea energy and resource development of independent technology and on time to achieve the“carbon peak”national strategic objectives.展开更多
A partial-periodic model is proposed for predicting structural properties of composite laminate structures.The partial-periodic model contains periodic boundary conditions in one direction or two directions,and free b...A partial-periodic model is proposed for predicting structural properties of composite laminate structures.The partial-periodic model contains periodic boundary conditions in one direction or two directions,and free boundary condition in other directions.In the present study,partial-periodic model for composite laminate beam structures is particularly studied.Three-point bending experiments for laminate beam specimens with different laying parameters are firstly used to verify the present partial-periodic model.In addition,a detailed finite element method(FEM)model is also used to further quantitatively compare with the present partial-periodic model for composite laminate beams with different laying parameters.The results indicate that the proposed partial-periodic model is capable of providing accurate predictions in most cases.The computational time cost of the proposed partial-periodic model is much lower than that of the detailed FEM model as well.Convergence studies are also conducted for the present partial-periodic model with different model sizes and element sizes.It is suggested that the proposed partial-periodic model has the potential to be used as an accurate and time-saving tool for predicting the structural properties of composite laminate beam structures.展开更多
This paper presents a novel element differential method for modeling cracks in piezoelectric materials,aiming to simulate fracture behaviors and predict the fracture parameter known as the J-integral accurately.The me...This paper presents a novel element differential method for modeling cracks in piezoelectric materials,aiming to simulate fracture behaviors and predict the fracture parameter known as the J-integral accurately.The method leverages an efficient collocation technique to satisfy traction and electric charge equilibrium on the crack surface,aligning internal nodes with piezoelectric governing equations without needing integration or variational principles.It combines the strengths of the strong form collocation and finite element methods.The J-integral is derived analytically using the equivalent domain integral method,employing Green's formula and Gauss's divergence theorem to transform line integrals into area integrals for solving two-dimensional piezoelectric material problems.The accuracy of the method is validated through comparison with three typical examples,and it offers fracture prevention strategies for engineering piezoelectric structures under different electrical loading patterns.展开更多
To address the challenges associated with multi-sided shells in traditional isogeometric analysis(IGA),this paper introduces a novel isogeometric shell method for trimmed CAD geometries based on toric surfaces and Rei...To address the challenges associated with multi-sided shells in traditional isogeometric analysis(IGA),this paper introduces a novel isogeometric shell method for trimmed CAD geometries based on toric surfaces and Reissner–Mindlin shell theory.By utilizing toric surface patches,both trimmed and untrimmed elements of the CAD surfaces are represented through a unified geometric framework,ensuring continuity and an accurate geometric description.Toric-Bernstein basis functions are employed to accurately interpolate the geometry and displacement of the trimmed shell.For singularities and corner points on the toric surface,the normal vector is defined as the unit directional vector from the center of curvature to the corresponding control point.Several numerical examples of polygonal shells are presented to evaluate the effectiveness and robustness of the proposed method.This approach significantly simplifies the treatment of trimmed shell IGA and provides a promising solution for simulating complex shell structures with intricate boundaries.展开更多
In order to investigate the penetration performance of Linear-Shaped Charge(LSC),Embowed LinearShaped Charge(ELSC),and Embowed Linear Explosively Formed Projectile(ELEFP)on T-shaped stiffened plates,a series of near-f...In order to investigate the penetration performance of Linear-Shaped Charge(LSC),Embowed LinearShaped Charge(ELSC),and Embowed Linear Explosively Formed Projectile(ELEFP)on T-shaped stiffened plates,a series of near-field air-burst experiments are conducted.The damage modes and characteristics of the target plates are compared and analyzed.Each flat plate section is completely punctured,resulting in a penetration hole.The damage modes induced by the three charge types on the stiffened plate structure are consistent,characterized by shear failure in the central region of the flat plate due to penetration by the penetrator,localized plastic deformation of the flat plate,and local penetration failure resulting from partial perforation of the central stiffener.The penetration lengths caused by ELSC and ELEFP are 45.1%and 46.1% larger than that of LSC,while the half-width of the penetration hole generated by ELEFP is 54.2% and 24.7% smaller than that of ELSC and LSC,respectively.The penetration height caused by ELEFP are 17.5%and 62.1% larger than that of ELSC and LSC,respectively.The stiffener effectively segments the damage area,enhancing the local structural strength and limiting the extent of plastic deformation in the flat plate section.The comparative results show that the ELSC proves to be more effective for efficient large-scale damage,and ELEFP is more suitable for achieving efficient localized damage.展开更多
With the rapid development of artificial intelligence,intelligent air combat maneuver decision-making(ACMD)has garnered global attention.Although deep reinforcement learning provides a promising approach to ACMD,exist...With the rapid development of artificial intelligence,intelligent air combat maneuver decision-making(ACMD)has garnered global attention.Although deep reinforcement learning provides a promising approach to ACMD,existing methods often suffer from rigid reward functions and limited adaptability to evolving adversarial strategies.Moreover,most research assumes open airspace,overlooking the influence of potential obstacles.In this paper,we address one-on-one within-visual-range ACMD in obstructed environments,and propose an improved Soft Actor-Critic(SAC)algorithm trained under a curriculum self-play framework.A maneuver strategy mirroring inference module is integrated to estimate each other's likely positions when visual obstruction occurs.By leveraging curriculum learning to guide progressive experience accumulation and self-play for adversarial evolution,our method enhances both training efficiency and tactical diversity.We further integrate an attention mechanism that dynamically adjusts the weights of sub-rewards,enabling the learned policy to adapt to rapidly changing air combat situations.Numerical simulations demonstrate that our enhanced SAC converges more quickly and achieves higher win rates than other baseline methods.An animation is available at bilibili.com/video/BV1BHVszHE98 for better illustration.展开更多
Conformal truss-like lattice structures face significant manufacturability challenges in additive manufac-turing due to overhang angle limitations.To address this problem,we propose a novel angle-constrained optimizat...Conformal truss-like lattice structures face significant manufacturability challenges in additive manufac-turing due to overhang angle limitations.To address this problem,we propose a novel angle-constrained optimization method grounded in the global adjustment of nodal coordinates.First,a build direction is selected to minimize the number of violating struts.Then,an angular-constraint matrix is assembled from strut direction vectors,and analytical sensitivities with respect to nodal coordinates are derived to enable efficient constrained optimization under nonlinear angular inequality constraints.Numerical studies on two complex curved-surface lattices demonstrate that all overhang violations are eliminated while only minor changes are induced in global stiffness and strength.In particular,the maximum displacement of an ergonomic insole varies by only 2.87%after optimization.The results confirm the method’s versatility and engineering robustness,providing a practical approach for additive manufacturing-oriented lattice structure design.展开更多
As carrier aircraft sortie frequency and flight deck operational density increase,autonomous dispatch trajectory planning for carrier-based vehicles demands efficient,safe,and kinematically feasible solutions.This pap...As carrier aircraft sortie frequency and flight deck operational density increase,autonomous dispatch trajectory planning for carrier-based vehicles demands efficient,safe,and kinematically feasible solutions.This paper presents an Iterative Safe Dispatch Corridor(iSDC)framework,addressing the suboptimality of the traditional SDC method caused by static corridor construction and redundant obstacle exploration.First,a Kinodynamic-Informed-Bidirectional Rapidly-exploring Random Tree Star(KIBRRT^(*))algorithm is proposed for the front-end coarse planning.By integrating bidirectional tree expansion,goal-biased elliptical sampling,and artificial potential field guidance,it reduces unnecessary exploration near concave obstacles and generates kinematically admissible paths.Secondly,the traditional SDC is implemented in an iterative manner,and the obtained trajectory in the current iteration is fed into the next iteration for corridor generation,thus progressively improving the quality of withincorridor constraints.For tractors,a reverse-motion penalty function is incorporated into the back-end optimizer to prioritize forward driving,aligning with mechanical constraints and human operational preferences.Numerical validations on the data of Gerald R.Ford-class carrier demonstrate that the KIBRRT^(*)reduces average computational time by 75%and expansion nodes by 25%compared to conventional RRT^(*)algorithms.Meanwhile,the iSDC framework yields more time-efficient trajectories for both carrier aircraft and tractors,with the dispatch time reduced by 31.3%and tractor reverse motion proportion decreased by 23.4%relative to traditional SDC.The presented framework offers a scalable solution for autonomous dispatch in confined and safety-critical environment,and an illustrative animation is available at bilibili.com/video/BV1tZ7Zz6Eyz.Moreover,the framework can be easily extended to three-dimension scenarios,and thus applicable for trajectory planning of aerial and underwater vehicles.展开更多
The on-orbit parameter identification of a space structure can be used for the modification of a system dynamics model and controller coefficients. This study focuses on the estimation of a system state-space model fo...The on-orbit parameter identification of a space structure can be used for the modification of a system dynamics model and controller coefficients. This study focuses on the estimation of a system state-space model for a two-link space manipulator in the procedure of capturing an unknown object, and a recursive tracking approach based on the recursive predictor-based subspace identification(RPBSID) algorithm is proposed to identify the manipulator payload mass parameter. Structural rigid motion and elastic vibration are separated, and the dynamics model of the space manipulator is linearized at an arbitrary working point(i.e., a certain manipulator configuration).The state-space model is determined by using the RPBSID algorithm and matrix transformation. In addition, utilizing the identified system state-space model, the manipulator payload mass parameter is estimated by extracting the corresponding block matrix. In numerical simulations, the presented parameter identification method is implemented and compared with the classical algebraic algorithm and the recursive least squares method for different payload masses and manipulator configurations. Numerical results illustrate that the system state-space model and payload mass parameter of the two-link flexible space manipulator are effectively identified by the recursive subspace tracking method.展开更多
Abstract Lesion of ossicular chain is a common ear disease impairing the sense of hearing. A comprehensive numerical model of human ear can provide better understanding of sound transmission. In this study, we propose...Abstract Lesion of ossicular chain is a common ear disease impairing the sense of hearing. A comprehensive numerical model of human ear can provide better understanding of sound transmission. In this study, we propose a three-dimensional finite element model of human ear that incorporates the canal, tympanic membrane, ossicular bones, middle ear suspensory ligaments/muscles, middle ear cavity and inner ear fluid. Numerical analysis is conducted and employed to predict the effects of middle ear cavity, malleus handle defect, hypoplasia of the long process of incus, and stapedial crus defect on sound transmission. The present finite element model is shown to be reasonable in predicting the ossicular mechanics of human ear.展开更多
In order to overcome the difficulties caused by singular optima, in the present paper, a new method for the solutions of structural topology optimization problems is proposed. The distinctive feature of this method is...In order to overcome the difficulties caused by singular optima, in the present paper, a new method for the solutions of structural topology optimization problems is proposed. The distinctive feature of this method is that instead of solving the original optimization problem directly, we turn to seeking the solutions of a sequence of approximated problems which are formulated by relaxing the constraints of the original problem to some extent. The approximated problem can be solved efficiently by employing the algorithms developed for sizing optimization problems because its solution is not singular. It can also be proved that when the relaxation parameter is tending to zero, the solution of the approximated problem will converge to the solution of the original problem uniformly. Numerical examples illustrate the effectiveness and validity of the present approach. Results are also compared with those obtained by traditional methods.展开更多
The spectral methods and ice-induced fatigue analysis are discussed based on Miner＇s linear cumulative fatigue hypothesis and S-N curve data. According to the long-term data of full-scale tests on the platforms in th...The spectral methods and ice-induced fatigue analysis are discussed based on Miner＇s linear cumulative fatigue hypothesis and S-N curve data. According to the long-term data of full-scale tests on the platforms in the Bohai Sea, the ice force spectrum of conical structures and the fatigue environmental model are established. Moreover, the finite element model of JZ20-2MSW platform, an example of ice-induced fatigue analysis, is built with ANSYS software. The mode analysis and dynamic analysis in frequency domain under all kinds of ice fatigue work conditions are carded on, and the fatigue life of the structure is estimated in detail. The methods in this paper can be helpful in ice-induced fatigue analysis of ice-resistant platforms.展开更多
Environmental load is the primary factor in the design of offshore engineering structures and ocean current is the principal environmental load that causes underwater structural failure. In computational analysis, the...Environmental load is the primary factor in the design of offshore engineering structures and ocean current is the principal environmental load that causes underwater structural failure. In computational analysis, the calculation of current load is mainly based on the current profile. The current profile model, which is based on a structural failure criterion, is conducive to decreasing the uncertainty of the current load. In this study, we used prototype monitoring data and the empirical orthogonal function(EOF) method to investigate the current profile in the South China Sea and its correlation with the design of underwater structural strength and the dynamic design of fatigue. The underwater structural strength design takes into account the size of the structure and the service water depth. We propose profiles for the overall and local designs using the inverse first-order reliability method(IFORM). We extracted the characteristic profile current(CPC) of the monitored sea area to solve dynamic design problems such as vortex-induced vibration(VIV). We used random sampling to verify the feasibility of using the EOF method to calculate the CPC from the current data and identified the main problems associated with using the CPC, which deserve close attention in VIV design. Our research conclusions provide direct references for determining current load in this sea area. This analysis method can also be used in the analysis of other sea areas or field variables.展开更多
An extended multiscale finite element method(EMsFEM)is developed for solving the mechanical problems of heterogeneous materials in elasticity.The underlying idea of the method is to construct numerically the multiscal...An extended multiscale finite element method(EMsFEM)is developed for solving the mechanical problems of heterogeneous materials in elasticity.The underlying idea of the method is to construct numerically the multiscale base functions to capture the small-scale features of the coarse elements in the multiscale finite element analysis.On the basis of our existing work for periodic truss materials,the construction methods of the base functions for continuum heterogeneous materials are systematically introduced.Numerical experiments show that the choice of boundary conditions for the construction of the base functions has a big influence on the accuracy of the multiscale solutions,thus,different kinds of boundary conditions are proposed.The efficiency and accuracy of the developed method are validated and the results with different boundary conditions are verified through extensive numerical examples with both periodic and random heterogeneous micro-structures.Also,a consistency test of the method is performed numerically.The results show that the EMsFEM can effectively obtain the macro response of the heterogeneous structures as well as the response in micro-scale,especially under the periodic boundary conditions.展开更多
Mooring system is the key equipment of FPSO safe operation. The soft yoke mooring system is regarded as one of the best shallow water mooring strategies and widely applied to the oil exploitation in the Bohai Bay in C...Mooring system is the key equipment of FPSO safe operation. The soft yoke mooring system is regarded as one of the best shallow water mooring strategies and widely applied to the oil exploitation in the Bohai Bay in China and the Gulf of Mexico. Based on the analysis of numerous monitoring data obtained by the prototype monitoring system of one FPSO in the Bohai Bay, the on-site lateral vibration behaviors found on the site of the soft yoke subject to wave load were analyzed. ADAMS simulation and model experiment were utilized to analyze the soft yoke lateral vibration and it was determined that lateral vibration was resonance behaviors caused by wave excitation. On the basis of the soft yoke longitudinal restoring force being guaranteed, a TLD-based vibration damper system was constructed and the vibration reduction experiments with multi-tank space and multi-load conditions were developed. The experimental results demonstrated that the proposed TLD vibration reduction system can effectively reduce lateral vibration of soft yoke structures.展开更多
The study focuses on the flexible jumper issue of Subsurface Tension Leg Production （STLP） system concept, which is considered as a competing alternative system to support well completion devices and rigid risers in...The study focuses on the flexible jumper issue of Subsurface Tension Leg Production （STLP） system concept, which is considered as a competing alternative system to support well completion devices and rigid risers in ultra-deep water for offshore petroleum production. The paper presents analytical and numerical approaches for the optimum design and global analysis of the flexible jumper. Criteria using catenary concept are developed to define the critical length for optimum design. Based on the criteria, detailed hydrodynamic analyses including quasi-static analysis, modal analysis, and dynamic analysis are performed. Modal analysis with respect to the quasi-static analysis shows that the existence of resonant modes requires special consideration. The results of dynamic analysis confirm the effectiveness of the de-coupled effect from the jumper on STLP system. The approaches developed in the study also have wide application prospect in reference to the optimum design and analysis of any Hybrid Riser （HR） concept.展开更多
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 stil...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 to now,the lower-bound curve in NASA SP-8007 is still widely used as the design criterion of aerospace thin-walled structures,and this series of knockdown factors(KDF)has been proven to be overly conservative with the significant promotion of the manufacturing process.In recent years,several new numerical and experimental methods for determining KDF have been established,which are systematically reviewed in this paper.The Worst Multiple Perturbation Load Approach(WMPLA)is one of the most representative methods to reduce the conservatism of traditional methods in a rational manner.Based on an extensive collection of test data from 1990 to 2020,a new lower-bound curve is approximated to produce a series of improved KDFs.It is evident that these new KDFs have an overall improvement of 0.1-0.3 compared with NASA SP-8007,and the KDF predicted by the WMPLA is very close to the front of the new curve.This may provide some insight into future design guidelines of axially compressed cylindrical shells,which is promising for the lightweight design of large-diameter aerospace structures.展开更多
Space robotics has been used extensively in complex space missions. Rigid-manipulator space robots may suffer from rigid-body collisions with targets. This collision is likely to cause damage to the space robot and th...Space robotics has been used extensively in complex space missions. Rigid-manipulator space robots may suffer from rigid-body collisions with targets. This collision is likely to cause damage to the space robot and the target. To overcome such a problem, a novel ContinuumManipulator Space Robot(CMSR) for performing on-orbit servicing missions is proposed in this paper. Compared with rigid-manipulator space robots, CMSRs are able to perform compliant operations and avoid rigid-body collisions with a target. The CMSR consists of two kinds of flexible components, including solar arrays and continuum manipulators. The elastic vibrations of these flexible components disturb the position and attitude of CMSRs. The beating phenomenon introduced by the energy transfer among these flexible components can cause damage to solar arrays.The complicated dynamic coupling poses enormous challenges in dynamic modeling and vibration analysis. The dynamic model for CMSRs is derived and the mechanism of the beating phenomenon is analyzed in this paper. Simulation results show that an obvious beating phenomenon occurs and the amplitude of the solar arrays increases significantly when the natural frequencies of two kinds of flexible components are close. A method is provided to avoid the beating phenomenon.展开更多
基金supported by the National Key Research and Development Program of China(No.2020YFB1708303)the National Natural Science Foundation of China(Nos.U1808215 and 12072058)the Fundamental Research Funds for the Central Universities of China(DUT20LK02).
文摘Honeycomb structures of shape memory alloy(SMA)have become one of the most promising materials for flexible skins of morphing aircraft due to their excellent mechanical properties.However,due to the nonlinear material and geometric large deformation,the SMA honeycomb exhibits significant and complex nonlinearity in the skin and there is a lack of relevant previous research.In this paper,the nonlinear properties of the SMA honeycomb structure with arbitrary geometry are investigated for the first time for large deformation flexible skin applications by theoretical and experimental analysis.Firstly,a novel theoretical model of SMA honeycomb structure considering both material and geometric nonlinearity is proposed,and the corresponding calculation method of nonlinear governing equations is given based upon the shooting method and Runge–Kutta method.Then,the tensile behaviors of four kinds of SMA honeycomb structures,i.e.,U-type,V-type,cosine-type,and trapezoid-type,are analyzed and predicted by the proposed theoretical model and compared with the finite element analysis(FEA)results.Moreover,the tensile experiments were carried out by stretching U-type and V-type honeycomb structures to a global strain of 60%and 40%,respectively,to perform large deformation analysis and verify the theoretical model.Finally,experimental verification and finite element validation show that the curves of the theoretical model results,experimental results,and simulation results are in good agreement,illustrating the generalizability and accuracy of the proposed theoretical model.The theoretical model and experimental investigations in this paper are considered to provide an effective foundation for analyzing and predicting the mechanical behavior of SMA honeycomb flexible skins with large extensional deformations.
基金supported by the National Natural Science Foundation of China (11072049,10772038)the Key Project of Chinese National Programs for Fundamental Research and Development (2010CB832703)+1 种基金the National Key Technology Support Program (2009BAG12A04)the Program for New Century Excellent Talents in University
文摘This paper analyzes the random response of structural-acoustic coupled systems. Most existing works on coupled structural-acoustic analysis are limited to systems under deterministic excitations due to high computational cost required by a random response analysis. To reduce the computational burden involved in the coupled random analysis, an iterative procedure based on the Pseudo excitation method has been developed. It is found that this algorithm has an overwhelming advantage in computing efficiency over traditional methods, as demonstrated by some numerical examples given in this paper.
基金financially supported by the National Key R&D Program of China(Grant No.2021YFA1003501)the National Natural Science Foundation of China(Grant No.U1906233)+2 种基金the Key R&D Program of Shandong Province(Grant No.2019JZZY010801)the Central Guidance on Local Science and Technology Development Fund of Shenzhen(Grant No.2021Szvup021)the Fundamental Research Funds for the Central Universities(Grant Nos.DUT22ZD209 and DUT21ZD209)。
文摘Offshore oil and gas development plays an important part in the global energy sector.Offshore platforms and flexible pipes are the key equipments in the whole offshore oil and gas development system.Because of the randomness and uncertainty of wave and current loads in the ocean environment,the structural design and mechanical analysis of the marine equipment can be highly complicated.Therefore,this paper reviews the recent works of the theoretical model,numerical simulation,and experimental test in three research areas:hydrodynamic analysis of offshore platforms,structural mechanics analysis of flexible pipe and cable,and monitoring technology of offshore floating structures under marine loads.By analyzing their main research methods and key technical difficulties,this paper provides theoretical basis and technical support for the reliability engineering application of offshore platforms and flexible pipelines.Also,China is relatively backward in the design of marine floating platform,the design,analysis and testing of flexible pipeline and cable,as well as the marine equipment prototype monitoring technology research.Calling for breakthroughs at the earliest possible stage in the above fields,prime research should be focused on and strategic planning should be made to deal with“key areas and stranglehold problems”.It is of great significance for the development of China's deep-sea energy and resource development of independent technology and on time to achieve the“carbon peak”national strategic objectives.
基金financial support from the National Key Research and Development Plan(2022YFB3707700)the National Natural Science Foundation of China(11872138 and 12172074)+1 种基金the Liaoning Revitalization Talents Program(XLYC2001003)the Dalian Excellent Young Science and Technology Talent Program(2023RY025).
文摘A partial-periodic model is proposed for predicting structural properties of composite laminate structures.The partial-periodic model contains periodic boundary conditions in one direction or two directions,and free boundary condition in other directions.In the present study,partial-periodic model for composite laminate beam structures is particularly studied.Three-point bending experiments for laminate beam specimens with different laying parameters are firstly used to verify the present partial-periodic model.In addition,a detailed finite element method(FEM)model is also used to further quantitatively compare with the present partial-periodic model for composite laminate beams with different laying parameters.The results indicate that the proposed partial-periodic model is capable of providing accurate predictions in most cases.The computational time cost of the proposed partial-periodic model is much lower than that of the detailed FEM model as well.Convergence studies are also conducted for the present partial-periodic model with different model sizes and element sizes.It is suggested that the proposed partial-periodic model has the potential to be used as an accurate and time-saving tool for predicting the structural properties of composite laminate beam structures.
基金Financial support of this work by the Technology Development program of China(Grant No.2022204B003)National Natural Science Foundation of China(12272083 and 12172078)the Fundamental Research Funds for the Central Universities(DUT24YJ136)is gratefully acknowledged.
文摘This paper presents a novel element differential method for modeling cracks in piezoelectric materials,aiming to simulate fracture behaviors and predict the fracture parameter known as the J-integral accurately.The method leverages an efficient collocation technique to satisfy traction and electric charge equilibrium on the crack surface,aligning internal nodes with piezoelectric governing equations without needing integration or variational principles.It combines the strengths of the strong form collocation and finite element methods.The J-integral is derived analytically using the equivalent domain integral method,employing Green's formula and Gauss's divergence theorem to transform line integrals into area integrals for solving two-dimensional piezoelectric material problems.The accuracy of the method is validated through comparison with three typical examples,and it offers fracture prevention strategies for engineering piezoelectric structures under different electrical loading patterns.
基金the National Key Research and Development Projects(Grant Nos.2021YFB3300601,2021YFB3300603,2021YFB3300604)the Fundamental Research Funds for the Central Universities(No.DUT22QN241)is acknowledged.
文摘To address the challenges associated with multi-sided shells in traditional isogeometric analysis(IGA),this paper introduces a novel isogeometric shell method for trimmed CAD geometries based on toric surfaces and Reissner–Mindlin shell theory.By utilizing toric surface patches,both trimmed and untrimmed elements of the CAD surfaces are represented through a unified geometric framework,ensuring continuity and an accurate geometric description.Toric-Bernstein basis functions are employed to accurately interpolate the geometry and displacement of the trimmed shell.For singularities and corner points on the toric surface,the normal vector is defined as the unit directional vector from the center of curvature to the corresponding control point.Several numerical examples of polygonal shells are presented to evaluate the effectiveness and robustness of the proposed method.This approach significantly simplifies the treatment of trimmed shell IGA and provides a promising solution for simulating complex shell structures with intricate boundaries.
基金supported by the National Natural Science Foundation of China(Grant Nos.52271307,52061135107,52192692,11802025)the Liao Ning Excellent Youth Fund Program(Grant No.2023JH3/10200012)+1 种基金the Liao Ning Revitalization Tal-ents Program(Grant No.XLYC1908027)the Fundamental Research Funds for the Central Universities(Grant Nos.DUT20RC(3)025,DUT20TD108,DUT20LAB308)。
文摘In order to investigate the penetration performance of Linear-Shaped Charge(LSC),Embowed LinearShaped Charge(ELSC),and Embowed Linear Explosively Formed Projectile(ELEFP)on T-shaped stiffened plates,a series of near-field air-burst experiments are conducted.The damage modes and characteristics of the target plates are compared and analyzed.Each flat plate section is completely punctured,resulting in a penetration hole.The damage modes induced by the three charge types on the stiffened plate structure are consistent,characterized by shear failure in the central region of the flat plate due to penetration by the penetrator,localized plastic deformation of the flat plate,and local penetration failure resulting from partial perforation of the central stiffener.The penetration lengths caused by ELSC and ELEFP are 45.1%and 46.1% larger than that of LSC,while the half-width of the penetration hole generated by ELEFP is 54.2% and 24.7% smaller than that of ELSC and LSC,respectively.The penetration height caused by ELEFP are 17.5%and 62.1% larger than that of ELSC and LSC,respectively.The stiffener effectively segments the damage area,enhancing the local structural strength and limiting the extent of plastic deformation in the flat plate section.The comparative results show that the ELSC proves to be more effective for efficient large-scale damage,and ELEFP is more suitable for achieving efficient localized damage.
基金support of the National Key Research and Development Plan(No.2021YFB3302501)the financial support of the National Science Foundation of China(No.12161076)the financial support of the Fundamental Research Funds for the Central Universities(No.DUT25GF207).
文摘With the rapid development of artificial intelligence,intelligent air combat maneuver decision-making(ACMD)has garnered global attention.Although deep reinforcement learning provides a promising approach to ACMD,existing methods often suffer from rigid reward functions and limited adaptability to evolving adversarial strategies.Moreover,most research assumes open airspace,overlooking the influence of potential obstacles.In this paper,we address one-on-one within-visual-range ACMD in obstructed environments,and propose an improved Soft Actor-Critic(SAC)algorithm trained under a curriculum self-play framework.A maneuver strategy mirroring inference module is integrated to estimate each other's likely positions when visual obstruction occurs.By leveraging curriculum learning to guide progressive experience accumulation and self-play for adversarial evolution,our method enhances both training efficiency and tactical diversity.We further integrate an attention mechanism that dynamically adjusts the weights of sub-rewards,enabling the learned policy to adapt to rapidly changing air combat situations.Numerical simulations demonstrate that our enhanced SAC converges more quickly and achieves higher win rates than other baseline methods.An animation is available at bilibili.com/video/BV1BHVszHE98 for better illustration.
基金supported by the National Natural Science Foundation of China(Grant Nos.12432005 and 12472116)the Fundamental Research Funds for the Central Universities(DUTZD25240).
文摘Conformal truss-like lattice structures face significant manufacturability challenges in additive manufac-turing due to overhang angle limitations.To address this problem,we propose a novel angle-constrained optimization method grounded in the global adjustment of nodal coordinates.First,a build direction is selected to minimize the number of violating struts.Then,an angular-constraint matrix is assembled from strut direction vectors,and analytical sensitivities with respect to nodal coordinates are derived to enable efficient constrained optimization under nonlinear angular inequality constraints.Numerical studies on two complex curved-surface lattices demonstrate that all overhang violations are eliminated while only minor changes are induced in global stiffness and strength.In particular,the maximum displacement of an ergonomic insole varies by only 2.87%after optimization.The results confirm the method’s versatility and engineering robustness,providing a practical approach for additive manufacturing-oriented lattice structure design.
基金support of the National Key Research and Development Plan(Grant No.2021YFB3302501)the financial support of the National Science Foundation of China(Grant No.12161076)the financial support of the Fundamental Research Funds for the Central Universities(Grant No.DUT24LAB129).
文摘As carrier aircraft sortie frequency and flight deck operational density increase,autonomous dispatch trajectory planning for carrier-based vehicles demands efficient,safe,and kinematically feasible solutions.This paper presents an Iterative Safe Dispatch Corridor(iSDC)framework,addressing the suboptimality of the traditional SDC method caused by static corridor construction and redundant obstacle exploration.First,a Kinodynamic-Informed-Bidirectional Rapidly-exploring Random Tree Star(KIBRRT^(*))algorithm is proposed for the front-end coarse planning.By integrating bidirectional tree expansion,goal-biased elliptical sampling,and artificial potential field guidance,it reduces unnecessary exploration near concave obstacles and generates kinematically admissible paths.Secondly,the traditional SDC is implemented in an iterative manner,and the obtained trajectory in the current iteration is fed into the next iteration for corridor generation,thus progressively improving the quality of withincorridor constraints.For tractors,a reverse-motion penalty function is incorporated into the back-end optimizer to prioritize forward driving,aligning with mechanical constraints and human operational preferences.Numerical validations on the data of Gerald R.Ford-class carrier demonstrate that the KIBRRT^(*)reduces average computational time by 75%and expansion nodes by 25%compared to conventional RRT^(*)algorithms.Meanwhile,the iSDC framework yields more time-efficient trajectories for both carrier aircraft and tractors,with the dispatch time reduced by 31.3%and tractor reverse motion proportion decreased by 23.4%relative to traditional SDC.The presented framework offers a scalable solution for autonomous dispatch in confined and safety-critical environment,and an illustrative animation is available at bilibili.com/video/BV1tZ7Zz6Eyz.Moreover,the framework can be easily extended to three-dimension scenarios,and thus applicable for trajectory planning of aerial and underwater vehicles.
基金funded by the National Natural Science Foundation of China (Nos. 11572069 and 51775541)the China Postdoctoral Science Foundation (No. 2016M601354)
文摘The on-orbit parameter identification of a space structure can be used for the modification of a system dynamics model and controller coefficients. This study focuses on the estimation of a system state-space model for a two-link space manipulator in the procedure of capturing an unknown object, and a recursive tracking approach based on the recursive predictor-based subspace identification(RPBSID) algorithm is proposed to identify the manipulator payload mass parameter. Structural rigid motion and elastic vibration are separated, and the dynamics model of the space manipulator is linearized at an arbitrary working point(i.e., a certain manipulator configuration).The state-space model is determined by using the RPBSID algorithm and matrix transformation. In addition, utilizing the identified system state-space model, the manipulator payload mass parameter is estimated by extracting the corresponding block matrix. In numerical simulations, the presented parameter identification method is implemented and compared with the classical algebraic algorithm and the recursive least squares method for different payload masses and manipulator configurations. Numerical results illustrate that the system state-space model and payload mass parameter of the two-link flexible space manipulator are effectively identified by the recursive subspace tracking method.
基金supported by the National Natural Science Foundation of China (10472025, 10672036, and 10872043)
文摘Abstract Lesion of ossicular chain is a common ear disease impairing the sense of hearing. A comprehensive numerical model of human ear can provide better understanding of sound transmission. In this study, we propose a three-dimensional finite element model of human ear that incorporates the canal, tympanic membrane, ossicular bones, middle ear suspensory ligaments/muscles, middle ear cavity and inner ear fluid. Numerical analysis is conducted and employed to predict the effects of middle ear cavity, malleus handle defect, hypoplasia of the long process of incus, and stapedial crus defect on sound transmission. The present finite element model is shown to be reasonable in predicting the ossicular mechanics of human ear.
基金The project supported by the National Natural Science Foundation of China under project No.19572023
文摘In order to overcome the difficulties caused by singular optima, in the present paper, a new method for the solutions of structural topology optimization problems is proposed. The distinctive feature of this method is that instead of solving the original optimization problem directly, we turn to seeking the solutions of a sequence of approximated problems which are formulated by relaxing the constraints of the original problem to some extent. The approximated problem can be solved efficiently by employing the algorithms developed for sizing optimization problems because its solution is not singular. It can also be proved that when the relaxation parameter is tending to zero, the solution of the approximated problem will converge to the solution of the original problem uniformly. Numerical examples illustrate the effectiveness and validity of the present approach. Results are also compared with those obtained by traditional methods.
基金The paper was supported by the National 863 High Technology Develpoment Plan Project(Grant No.2001AA602015)
文摘The spectral methods and ice-induced fatigue analysis are discussed based on Miner＇s linear cumulative fatigue hypothesis and S-N curve data. According to the long-term data of full-scale tests on the platforms in the Bohai Sea, the ice force spectrum of conical structures and the fatigue environmental model are established. Moreover, the finite element model of JZ20-2MSW platform, an example of ice-induced fatigue analysis, is built with ANSYS software. The mode analysis and dynamic analysis in frequency domain under all kinds of ice fatigue work conditions are carded on, and the fatigue life of the structure is estimated in detail. The methods in this paper can be helpful in ice-induced fatigue analysis of ice-resistant platforms.
基金support for this work by the National Natural Science Foundation of China (No. 15572072)the National Key Basic Research and Development Program (No. 2016ZX05028-002-005)
文摘Environmental load is the primary factor in the design of offshore engineering structures and ocean current is the principal environmental load that causes underwater structural failure. In computational analysis, the calculation of current load is mainly based on the current profile. The current profile model, which is based on a structural failure criterion, is conducive to decreasing the uncertainty of the current load. In this study, we used prototype monitoring data and the empirical orthogonal function(EOF) method to investigate the current profile in the South China Sea and its correlation with the design of underwater structural strength and the dynamic design of fatigue. The underwater structural strength design takes into account the size of the structure and the service water depth. We propose profiles for the overall and local designs using the inverse first-order reliability method(IFORM). We extracted the characteristic profile current(CPC) of the monitored sea area to solve dynamic design problems such as vortex-induced vibration(VIV). We used random sampling to verify the feasibility of using the EOF method to calculate the CPC from the current data and identified the main problems associated with using the CPC, which deserve close attention in VIV design. Our research conclusions provide direct references for determining current load in this sea area. This analysis method can also be used in the analysis of other sea areas or field variables.
基金supported by the National Natural Science Foundation(10721062,11072051,90715037,10728205,91015003,51021140004)the Program of Introducing Talents of Discipline to Universities(B08014)the National Key Basic Research Special Foundation of China(2010CB832704).
文摘An extended multiscale finite element method(EMsFEM)is developed for solving the mechanical problems of heterogeneous materials in elasticity.The underlying idea of the method is to construct numerically the multiscale base functions to capture the small-scale features of the coarse elements in the multiscale finite element analysis.On the basis of our existing work for periodic truss materials,the construction methods of the base functions for continuum heterogeneous materials are systematically introduced.Numerical experiments show that the choice of boundary conditions for the construction of the base functions has a big influence on the accuracy of the multiscale solutions,thus,different kinds of boundary conditions are proposed.The efficiency and accuracy of the developed method are validated and the results with different boundary conditions are verified through extensive numerical examples with both periodic and random heterogeneous micro-structures.Also,a consistency test of the method is performed numerically.The results show that the EMsFEM can effectively obtain the macro response of the heterogeneous structures as well as the response in micro-scale,especially under the periodic boundary conditions.
基金supported by the National Natural Science Foundation of China(Grant No.11572072)the National Key Basic Research and Development Program of China(Grant Nos.2014CB046803 and 2016ZX05028-002-005)
文摘Mooring system is the key equipment of FPSO safe operation. The soft yoke mooring system is regarded as one of the best shallow water mooring strategies and widely applied to the oil exploitation in the Bohai Bay in China and the Gulf of Mexico. Based on the analysis of numerous monitoring data obtained by the prototype monitoring system of one FPSO in the Bohai Bay, the on-site lateral vibration behaviors found on the site of the soft yoke subject to wave load were analyzed. ADAMS simulation and model experiment were utilized to analyze the soft yoke lateral vibration and it was determined that lateral vibration was resonance behaviors caused by wave excitation. On the basis of the soft yoke longitudinal restoring force being guaranteed, a TLD-based vibration damper system was constructed and the vibration reduction experiments with multi-tank space and multi-load conditions were developed. The experimental results demonstrated that the proposed TLD vibration reduction system can effectively reduce lateral vibration of soft yoke structures.
基金financially supported by the National Natural Science Foundation of China(Grant No.51221961)
文摘The study focuses on the flexible jumper issue of Subsurface Tension Leg Production （STLP） system concept, which is considered as a competing alternative system to support well completion devices and rigid risers in ultra-deep water for offshore petroleum production. The paper presents analytical and numerical approaches for the optimum design and global analysis of the flexible jumper. Criteria using catenary concept are developed to define the critical length for optimum design. Based on the criteria, detailed hydrodynamic analyses including quasi-static analysis, modal analysis, and dynamic analysis are performed. Modal analysis with respect to the quasi-static analysis shows that the existence of resonant modes requires special consideration. The results of dynamic analysis confirm the effectiveness of the de-coupled effect from the jumper on STLP system. The approaches developed in the study also have wide application prospect in reference to the optimum design and analysis of any Hybrid Riser （HR） concept.
基金the National Natural Science Foundation of China(Grant Nos.U21A20429,11772078,and 11825202)the National Defense Basic Research Program(Grant No.JCKY2020110).
文摘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 to now,the lower-bound curve in NASA SP-8007 is still widely used as the design criterion of aerospace thin-walled structures,and this series of knockdown factors(KDF)has been proven to be overly conservative with the significant promotion of the manufacturing process.In recent years,several new numerical and experimental methods for determining KDF have been established,which are systematically reviewed in this paper.The Worst Multiple Perturbation Load Approach(WMPLA)is one of the most representative methods to reduce the conservatism of traditional methods in a rational manner.Based on an extensive collection of test data from 1990 to 2020,a new lower-bound curve is approximated to produce a series of improved KDFs.It is evident that these new KDFs have an overall improvement of 0.1-0.3 compared with NASA SP-8007,and the KDF predicted by the WMPLA is very close to the front of the new curve.This may provide some insight into future design guidelines of axially compressed cylindrical shells,which is promising for the lightweight design of large-diameter aerospace structures.
基金supported by the National Natural Science Foundation of China(Nos.91748203,11922203,11772074)。
文摘Space robotics has been used extensively in complex space missions. Rigid-manipulator space robots may suffer from rigid-body collisions with targets. This collision is likely to cause damage to the space robot and the target. To overcome such a problem, a novel ContinuumManipulator Space Robot(CMSR) for performing on-orbit servicing missions is proposed in this paper. Compared with rigid-manipulator space robots, CMSRs are able to perform compliant operations and avoid rigid-body collisions with a target. The CMSR consists of two kinds of flexible components, including solar arrays and continuum manipulators. The elastic vibrations of these flexible components disturb the position and attitude of CMSRs. The beating phenomenon introduced by the energy transfer among these flexible components can cause damage to solar arrays.The complicated dynamic coupling poses enormous challenges in dynamic modeling and vibration analysis. The dynamic model for CMSRs is derived and the mechanism of the beating phenomenon is analyzed in this paper. Simulation results show that an obvious beating phenomenon occurs and the amplitude of the solar arrays increases significantly when the natural frequencies of two kinds of flexible components are close. A method is provided to avoid the beating phenomenon.
