To solve the Laplacian problems,we adopt a meshless method with the multiquadric radial basis function(MQRBF)as a basis whose center is distributed inside a circle with a fictitious radius.A maximal projection techniq...To solve the Laplacian problems,we adopt a meshless method with the multiquadric radial basis function(MQRBF)as a basis whose center is distributed inside a circle with a fictitious radius.A maximal projection technique is developed to identify the optimal shape factor and fictitious radius by minimizing a merit function.A sample function is interpolated by theMQ-RBF to provide a trial coefficient vector to compute the merit function.We can quickly determine the optimal values of the parameters within a preferred rage using the golden section search algorithm.The novel method provides the optimal values of parameters and,hence,an optimal MQ-RBF;the performance of the method is validated in numerical examples.Moreover,nonharmonic problems are transformed to the Poisson equation endowed with a homogeneous boundary condition;this can overcome the problem of these problems being ill-posed.The optimal MQ-RBF is extremely accurate.We further propose a novel optimal polynomial method to solve the nonharmonic problems,which achieves high precision up to an order of 10^(−11).展开更多
Arches are widely used when large spans are necessary, e.g. to overpass large rivers, and further possess unquestioned aesthetics advantages. Their structural efficiency depends primarily on optimal material exploitat...Arches are widely used when large spans are necessary, e.g. to overpass large rivers, and further possess unquestioned aesthetics advantages. Their structural efficiency depends primarily on optimal material exploitation, i.e. minimization of internal stress eccentricity,and on minimization of structural material volume. An efficient structure, under these terms, further requires simpler and lighter scaffolding, contributing in minimizing construction costs.Although arches have millenary use and many researches dealing with this typology are available in literature, there is still scope for design optimization. The proposed study is framed within this context. Investigation is limited to statically determinate plane arches under vertical load. The problem of finding the profile of an equal strength catenary subjected to its self-weight is spread out to the case of an inverted catenary of equal strength under its self-weight and an external constant load. In the first optimization step, constant normal stress is imposed at all sections, to maximize material exploitation, and the resulting arch centerline shape is computed in closed form. In the second step, the ensemble of foundations and arch is considered and optimized, taking the linear combination of arch weight and thrust as objective function. The linear combination is dependent on a single variable, and minima of the objective function(i.e. optimal geometric shape parameters) are computed and charted to be simply used in the design process.展开更多
A body frame composed of thin sheet metal is a crucial structure that determines the safety performance of a vehicle.Designing a correct weight and high-performance automotive body is an emerging engineering problem.T...A body frame composed of thin sheet metal is a crucial structure that determines the safety performance of a vehicle.Designing a correct weight and high-performance automotive body is an emerging engineering problem.To improve the performance of the automotive frame,we attempt to reconstruct its design criteria based on statistical and mechanical approaches.At first,a fundamental study on the frame strength is conducted and a cross-sectional shape optimization problem is developed for designing the cross-sectional shape of an automobile frame having a very high mass efficiency for strength.Shape optimization is carried out using the nonlinear finite element method and a meta-modeling-based genetic algorithm.Data analysis of the obtained set of optimal results is performed to identify the dominant design variables by employing the smoothing spline analysis of variance,the principal component analysis,and the self-organizing map technique.The relationship between the cross-sectional shape and the objective function is also analyzed by hierarchical clustering.A design guideline is obtained from these statistical approach results.A comparison between the statistically obtained design guideline and the conventional one based on the designers’experience is performed based on mechanical interpretation of the optimal cross-sectional frame.Finally,a mechanically reasonable new general-purpose design guideline is proposed for the cross-sectional shape of the automotive frame.展开更多
We consider optimal shape design in Stokes flow using H^(1) shape gradient flows based on the distributed Eulerian derivatives.MINI element is used for discretizations of Stokes equation and Galerkin finite element is...We consider optimal shape design in Stokes flow using H^(1) shape gradient flows based on the distributed Eulerian derivatives.MINI element is used for discretizations of Stokes equation and Galerkin finite element is used for discretizations of distributed and boundary H^(1) shape gradient flows.Convergence analysis with a priori error estimates is provided under general and different regularity assumptions.We investigate the performances of shape gradient descent algorithms for energy dissipation minimization and obstacle flow.Numerical comparisons in 2D and 3D show that the distributed H1 shape gradient flow is more accurate than the popular boundary type.The corresponding distributed shape gradient algorithm is more effective.展开更多
The optimization of civil engineering structures is critical for enhancing structural performance and material efficiency in engineering applications.Structural optimization approaches seek to determine the optimal de...The optimization of civil engineering structures is critical for enhancing structural performance and material efficiency in engineering applications.Structural optimization approaches seek to determine the optimal design,by considering material performance,cost,and structural safety.The design approaches aim to reduce the built environment’s energy use and carbon emissions.This comprehensive review examines optimization techniques,including size,shape,topology,and multi-objective approaches,by integrating these methodologies.The trends and advancements that contribute to developing more efficient,cost-effective,and reliable structural designs were identified.The review also discusses emerging technologies,such as machine learning applications with different optimization techniques.Optimization of truss,frame,tensegrity,reinforced concrete,origami,pantographic,and adaptive structures are covered and discussed.Optimization techniques are explained,including metaheuristics,genetic algorithm,particle swarm,ant-colony,harmony search algorithm,and their applications with mentioned structure types.Linear and non-linear structures,including geometric and material nonlinearity,are distinguished.The role of optimization in active structures,structural design,seismic design,form-finding,and structural control is taken into account,and the most recent techniques and advancements are mentioned.展开更多
An effective optimization method for the shape/sizing design of composite wing structures is presented with satisfying weight-cutting results. After decoupling, a kind of two-layer cycled optimization strategy suitabl...An effective optimization method for the shape/sizing design of composite wing structures is presented with satisfying weight-cutting results. After decoupling, a kind of two-layer cycled optimization strategy suitable for these integrated shape/sizing optimization is obtained. The uniform design method is used to provide sample points, and approximation models for shape design variables. And the results of sizing optimization are construct- ed with the quadratic response surface method （QRSM）. The complex method based on QRSM is used to opti- mize the shape design variables and the criteria method is adopted to optimize the sizing design variables. Compared with the conventional method, the proposed algorithm is more effective and feasible for solving complex composite optimization problems and has good efficiency in weight cutting.展开更多
Aim To introduce a new method of adaptive shape optimization (ASOP) based on three-dimensional structure boundary strength and optimize an engine bearing cap with the method. Methods Using the normal substance's p...Aim To introduce a new method of adaptive shape optimization (ASOP) based on three-dimensional structure boundary strength and optimize an engine bearing cap with the method. Methods Using the normal substance's property of thermal expansion and cooling shrinkage,the load which is proportional to the difference between the nodes' stress and their respective objective stress were applied to the corresponding variable nodes on the boundary.The thermal load made the nodes whose stress is greater than their objective stress expand along the boundary's normal direction and the nodes whose stress is less than objec- tive stress shrink in the opposite direction , This process would repeat until the stress on the boundary nodes was converge to the objective stress. Results The satisfied results have been obtained when optimizing an engine bearing cap.The mass of the bearing cap is reduced to 55 percent of the total. Conclusion ASOP is an efficient,practical and reliable method which is suitable for optimizing the shape of the continuous structures.展开更多
The multi-objective optimization method was used for shape optimization of cement sand and gravel （CSG） dams in this study. The economic efficiency, the sensitivities of maximum horizontal displacement and maximum s...The multi-objective optimization method was used for shape optimization of cement sand and gravel （CSG） dams in this study. The economic efficiency, the sensitivities of maximum horizontal displacement and maximum settlement of the dam to water level changes, the overall stability, and the overall strength security were taken into account during the optimization process. Three weight coefficient selection schemes were adopted to conduct shape optimization of a dam, and the case studies lead to the conclusion that both the upstream-and downstream dam slope ratios for the optimal cross-section equal 1：0.7, which is consistent with the empirically observed range of 1：0.6 to 1;0.8 for the upstream and downstream dam slope ratios of CSG dams. Therefore, the present study is of certain reference value for designing CSG dams.展开更多
A new approach for the solution of truss shape and topology optimization problems under local and global stability constraints is proposed.By employing the cross sectional areas of each bar and some shape parameters a...A new approach for the solution of truss shape and topology optimization problems under local and global stability constraints is proposed.By employing the cross sectional areas of each bar and some shape parameters as topology design variables,the difficulty arising from the jumping of buckling length phenomenon can be easily overcome without the necessity of introduc- ing the overlapping bars into the initial ground structure.Therefore computational efforts can be saved for the solution of this kind of problem.By modifying the elements of the stiffness matrix using Sigmoid function,the continuity of the objective and constraint functions with respect to shape design parameters can be restored to some extent.Some numerical examples demonstrate the effectiveness of the proposed method.展开更多
In this paper,a Double-stage Surrogate-based Shape Optimization(DSSO)strategy for Blended-Wing-Body Underwater Gliders(BWBUGs)is proposed to reduce the computational cost.In this strategy,a double-stage surrogate mode...In this paper,a Double-stage Surrogate-based Shape Optimization(DSSO)strategy for Blended-Wing-Body Underwater Gliders(BWBUGs)is proposed to reduce the computational cost.In this strategy,a double-stage surrogate model is developed to replace the high-dimensional objective in shape optimization.Specifically,several First-stage Surrogate Models(FSMs)are built for the sectional airfoils,and the second-stage surrogate model is constructed with respect to the outputs of FSMs.Besides,a Multi-start Space Reduction surrogate-based global optimization method is applied to search for the optimum.In order to validate the efficiency of the proposed method,DSSO is first compared with an ordinary One-stage Surrogate-based Optimization strategy by using the same optimization method.Then,the other three popular surrogate-based optimization methods and three heuristic algorithms are utilized to make comparisons.Results indicate that the lift-to-drag ratio of the BWBUG is improved by 9.35%with DSSO,which outperforms the comparison methods.Besides,DSSO reduces more than 50%of the time that other methods used when obtaining the same level of results.Furthermore,some considerations of the proposed strategy are further discussed and some characteristics of DSSO are identified.展开更多
Subsea tunnel lining structures should be designed to sustain the loads transmitted from surrounding ground and groundwater during excavation. Extremely high pore-water pressure reduces the effective strength of the c...Subsea tunnel lining structures should be designed to sustain the loads transmitted from surrounding ground and groundwater during excavation. Extremely high pore-water pressure reduces the effective strength of the country rock that surrounds a tunnel, thereby lowering the arching effect and stratum stability of the structure. In this paper, the mechanical behavior and shape optimization of the lining structure for the Xiang＇an tunnel excavated in weathered slots are examined. Eight cross sections with different geometric parameters are adopted to study the mechanical behavior and shape optimization of the lining structure. The hyperstatic reaction method is used through finite element analysis software ANSYS. The mechanical behavior of the lining structure is evidently affected by the geometric parameters of crosssectional shape. The minimum safety factor of the lining structure elements is set to be the objective function. The efficient tunnel shape to maximize the minimum safety factor is identified. The minimum safety factor increases significantly after optimization. The optimized cross section significantly improves the mechanical characteristics of the lining structure and effectively reduces its deformation. Force analyses of optimization process and program are conducted parametrically so that the method can be applied to the optimization design of other similar structures. The results obtained from this study enhance our understanding of the mechanical behavior of the lining structure for subsea tunnels. These results are also beneficial to the optimal design of lining structures in general.展开更多
As a type of autonomous underwater vehicle(AUV),underwater gliders(UG)are getting increasing attention in ocean exploration.To save energy and satisfy the mission requirements of a longer voyage,shape optimization for...As a type of autonomous underwater vehicle(AUV),underwater gliders(UG)are getting increasing attention in ocean exploration.To save energy and satisfy the mission requirements of a longer voyage,shape optimization for UGs has become a key technique and research focus.In this paper,a conventional UG,including its fuselage and hydrofoil,is optimized,which aims to decrease the average resistance in one motion cycle.To operate the optimization progress for the complex object,multiple free form deformation(FFD)volumes are established for geometric parameterization.High-fidelity simulation models are employed for objective function evaluation and gradients calculation.And sequential quadratic programming(SQP)method is adopted as an optimization algorithm.The optimization results show that there exists a UG with symmetrical and non-horizontal hydrofoils that has lower resistance.展开更多
Tailor rolled blank （TRB） is a type of emerging material to produce lightweight vehicle parts. Transitional zoners shape is an important parameter for tailor rolled blank. It not only affects mold design and the loc...Tailor rolled blank （TRB） is a type of emerging material to produce lightweight vehicle parts. Transitional zoners shape is an important parameter for tailor rolled blank. It not only affects mold design and the local carrying capacity of the stamping parts, but also determines the maximum value and variation characteristics of rolling force. How to get the best transitional zone＇s shape is a key problem for production of tailor rolled blank. A double power function is put forward using for transitional curve, which is continuous and smooth at all connection points inde- pendent of its parameters, so the sudden change of mechanical parameters during rolling and forming process can be avoided. At the same time, the velocity formula and restriction for arbitrary transitional curve are derived to preset vertical velocity of the roller and judge whether the curve can be rolled successfully or not. Then, the finite element method （FEM） is used to verify the precision of velocity formula and study the mechanical characteristics of different curves. Finally, a method to obtain the optimal curve equation is put forward and verified.展开更多
Adjoint method is widely used in aerodynamic design because only once solution of flow field is required for it to obtain the gradients of all design variables. However, the computational cost of adjoint vector is app...Adjoint method is widely used in aerodynamic design because only once solution of flow field is required for it to obtain the gradients of all design variables. However, the computational cost of adjoint vector is approximately equal to that of flow computation. In order to accelerate the solution of adjoint vector and improve the efficiency of adjoint-based optimization, machine learning for adjoint vector modeling is presented. Deep neural network (DNN) is employed to construct the mapping between the adjoint vector and the local flow variables. DNN can efficiently predict adjoint vector and its generalization is examined by a transonic drag reduction of NACA0012 airfoil. The results indicate that with negligible computational cost of the adjoint vector, the proposed DNN-based adjoint method can achieve the same optimization results as the traditional adjoint method.展开更多
The hull form optimization concerns one of the most important applications of wave-making resistance theories.In recent years,scholars can determine the hull form by using the optimization method based on the computat...The hull form optimization concerns one of the most important applications of wave-making resistance theories.In recent years,scholars can determine the hull form by using the optimization method based on the computational fluid dynamics(CFD)and other mathematical techniques.In this paper,the hull form optimization method based on the Rankine source method and nonlinear programming(NLP)is discussed;in the optimization process,a hull form modification function is introduced to represent an improved hull surface and to generate a new smooth hull surface by changing its frame lines and bow stem profiles under the prescribed design constraints. Numerical example is given for a practical container hull form.Finally,shape optimization of bow bulls is shown for non-protruding and protruding bow bulls.This study presents a simplified and practical design method to the select frame lines of bow bulls.展开更多
Smoothly stitching multiple surfaces mainly represented by B-spline or NURBS together is an extremely important issue in complex surfaces modeling and reverse engineering.In recent years,a lot of progress has been mad...Smoothly stitching multiple surfaces mainly represented by B-spline or NURBS together is an extremely important issue in complex surfaces modeling and reverse engineering.In recent years,a lot of progress has been made in smooth join of non-trimmed surface patches,while there has been seldom research on smoothly stitching trimmed surface patches together.This paper studies the problem of global continuity adjustment,damaged hole repair and local shape optimization for complex trimmed surface model,and presents a uniform scheme to deal with continuity adjustment of trimmed surfaces and geometric repair of local broken region.Constrained B-spline surface refitting technique and trim calculation are first utilized to achieve global G^1 continuity,and then local shape optimization functional is adopted to reduce fitting error and improve local quality of refitted surface patch.The proposed approach is applied to a discontinuity ship hull surface model with an irregular hole,and the result demonstrates the validation of our method.Furthermore,on the premise of global continuity,the proposed locally repairing damaged surface model provides a better foundation for following research work,such as topology recovery technique for complex surface model after geometric repair.展开更多
This paper presents a novel optimization technique for an efficient multi-fidelity model building approach to reduce computational costs for handling aerodynamic shape optimization based on high-fidelity simulation mo...This paper presents a novel optimization technique for an efficient multi-fidelity model building approach to reduce computational costs for handling aerodynamic shape optimization based on high-fidelity simulation models. The wing aerodynamic shape optimization problem is solved by dividing optimization into three steps—modeling 3D（high-fidelity） and 2D（lowfidelity） models, building global meta-models from prominent instead of all variables, and determining robust optimizing shape associated with tuning local meta-models. The adaptive robust design optimization aims to modify the shape optimization process. The sufficient infilling strategy—known as adaptive uniform infilling strategy—determines search space dimensions based on the last optimization results or initial point. Following this, 3D model simulations are used to tune local meta-models. Finally, the global optimization gradient-based method—Adaptive Filter Sequential Quadratic Programing（AFSQP） is utilized to search the neighborhood for a probable optimum point. The effectiveness of the proposed method is investigated by applying it, along with conventional optimization approach-based meta-models, to a Blended Wing Body（BWB） Unmanned Aerial Vehicle（UAV）. The drag coefficient is defined as the objective function, which is subjected to minimum lift coefficient bounds and stability constraints. The simulation results indicate improvement in meta-model accuracy and reduction in computational time of the method introduced in this paper.展开更多
Based on the theory of reliability-based structural shape optimization, exact expressions of the sensibility using the stochastic finite element method for contact problems were derived in detail, and the basic steps ...Based on the theory of reliability-based structural shape optimization, exact expressions of the sensibility using the stochastic finite element method for contact problems were derived in detail, and the basic steps of structural optimization were given. A coattail-type tenon/mortise of an aero-engine was optimized. In this model, the maximum equivalent stress of the nodes on the boundary of the tenon was the objective function; the width of tooth’s neck and the side surface’s slope angle of a tenon were design variables, with constraints of tension stress, extrusion stress and reliability index. The result showed that the distributions of the contact pressure between tenon and mortise, the equivalence stress and reliability index were more reasonable. It validates the correctness of the optimization model and the reliability-based structural shape optimization, and provides valuable references for structural design of the tenon/mortise.展开更多
With the introduction of the design variables of nodal coordinates, which reflect the embedded depth of the pile and the jacket bed height, a shape optimum design model for offshore jacket platforms is established. A ...With the introduction of the design variables of nodal coordinates, which reflect the embedded depth of the pile and the jacket bed height, a shape optimum design model for offshore jacket platforms is established. A sequential two-level optimum algorithm is developed based on the design variable gradation. On the basis of the finite element method, the sensitivity of the objective function and nodal displacement is analyzed. As an example, the BZ281 oil storage offshore platform, which ties in the Bohai oil field, is designed with the shape optimum model. The results are compared with the cross-section optimum design. The tendency of design variables and its reasons in the two methods are analyzed. In the shape optimum design, the value of objective function is obviously smaller than that of the initial design and the cross-section optimum design. Therefore, the advantage of structure shape optimum design for jacket platforms is remarkable.展开更多
As a new kind of autonomous underwater vehicle,bionic submersible has many merits such as high efficiency and low costs.In order to obtain such advantages,it is a good way to simulate the shapes of marine animals and ...As a new kind of autonomous underwater vehicle,bionic submersible has many merits such as high efficiency and low costs.In order to obtain such advantages,it is a good way to simulate the shapes of marine animals and apply them to the design of artificial underwater vehicle.In this paper,an optimization system of airfoils is proposed by the improved class-shape-transformation(CST)parameterization method and genetic algorithm(GA).The appearance of a manta-ray-inspired underwater vehicle is rebuilt using the optimal sectional airfoils obtained by the proposed optimization system.Computational simulations are carried out to investigate the hydrodynamic performance of the submersible using the commercial computational fluid dynamics(CFD)code Fluent.The results demonstrate that the maximum thickness of the vehicle increases by 9%,which means the loading capacity is increased.Moreover,the underwater vehicle shows better hydrodynamic performance,and the lift-drag ratio of initial design is increased by more than 10%using the presented optimization system of airfoils.展开更多
基金supported by the the National Science and Technology Council(Grant Number:NSTC 112-2221-E239-022).
文摘To solve the Laplacian problems,we adopt a meshless method with the multiquadric radial basis function(MQRBF)as a basis whose center is distributed inside a circle with a fictitious radius.A maximal projection technique is developed to identify the optimal shape factor and fictitious radius by minimizing a merit function.A sample function is interpolated by theMQ-RBF to provide a trial coefficient vector to compute the merit function.We can quickly determine the optimal values of the parameters within a preferred rage using the golden section search algorithm.The novel method provides the optimal values of parameters and,hence,an optimal MQ-RBF;the performance of the method is validated in numerical examples.Moreover,nonharmonic problems are transformed to the Poisson equation endowed with a homogeneous boundary condition;this can overcome the problem of these problems being ill-posed.The optimal MQ-RBF is extremely accurate.We further propose a novel optimal polynomial method to solve the nonharmonic problems,which achieves high precision up to an order of 10^(−11).
基金the research project “OptArch e689983,H2020-MSCA-RISE-2015/H2020-MSCA-RISE-20”
文摘Arches are widely used when large spans are necessary, e.g. to overpass large rivers, and further possess unquestioned aesthetics advantages. Their structural efficiency depends primarily on optimal material exploitation, i.e. minimization of internal stress eccentricity,and on minimization of structural material volume. An efficient structure, under these terms, further requires simpler and lighter scaffolding, contributing in minimizing construction costs.Although arches have millenary use and many researches dealing with this typology are available in literature, there is still scope for design optimization. The proposed study is framed within this context. Investigation is limited to statically determinate plane arches under vertical load. The problem of finding the profile of an equal strength catenary subjected to its self-weight is spread out to the case of an inverted catenary of equal strength under its self-weight and an external constant load. In the first optimization step, constant normal stress is imposed at all sections, to maximize material exploitation, and the resulting arch centerline shape is computed in closed form. In the second step, the ensemble of foundations and arch is considered and optimized, taking the linear combination of arch weight and thrust as objective function. The linear combination is dependent on a single variable, and minima of the objective function(i.e. optimal geometric shape parameters) are computed and charted to be simply used in the design process.
文摘A body frame composed of thin sheet metal is a crucial structure that determines the safety performance of a vehicle.Designing a correct weight and high-performance automotive body is an emerging engineering problem.To improve the performance of the automotive frame,we attempt to reconstruct its design criteria based on statistical and mechanical approaches.At first,a fundamental study on the frame strength is conducted and a cross-sectional shape optimization problem is developed for designing the cross-sectional shape of an automobile frame having a very high mass efficiency for strength.Shape optimization is carried out using the nonlinear finite element method and a meta-modeling-based genetic algorithm.Data analysis of the obtained set of optimal results is performed to identify the dominant design variables by employing the smoothing spline analysis of variance,the principal component analysis,and the self-organizing map technique.The relationship between the cross-sectional shape and the objective function is also analyzed by hierarchical clustering.A design guideline is obtained from these statistical approach results.A comparison between the statistically obtained design guideline and the conventional one based on the designers’experience is performed based on mechanical interpretation of the optimal cross-sectional frame.Finally,a mechanically reasonable new general-purpose design guideline is proposed for the cross-sectional shape of the automotive frame.
基金This work was supported in part by the National Natural Science Foundation of China under grants(No.11571115 and No.12071149)Natural Science Foundation of Shanghai(No.19ZR1414100)Science and Technology Commission of Shanghai Municipality(No.18dz2271000).
文摘We consider optimal shape design in Stokes flow using H^(1) shape gradient flows based on the distributed Eulerian derivatives.MINI element is used for discretizations of Stokes equation and Galerkin finite element is used for discretizations of distributed and boundary H^(1) shape gradient flows.Convergence analysis with a priori error estimates is provided under general and different regularity assumptions.We investigate the performances of shape gradient descent algorithms for energy dissipation minimization and obstacle flow.Numerical comparisons in 2D and 3D show that the distributed H1 shape gradient flow is more accurate than the popular boundary type.The corresponding distributed shape gradient algorithm is more effective.
文摘The optimization of civil engineering structures is critical for enhancing structural performance and material efficiency in engineering applications.Structural optimization approaches seek to determine the optimal design,by considering material performance,cost,and structural safety.The design approaches aim to reduce the built environment’s energy use and carbon emissions.This comprehensive review examines optimization techniques,including size,shape,topology,and multi-objective approaches,by integrating these methodologies.The trends and advancements that contribute to developing more efficient,cost-effective,and reliable structural designs were identified.The review also discusses emerging technologies,such as machine learning applications with different optimization techniques.Optimization of truss,frame,tensegrity,reinforced concrete,origami,pantographic,and adaptive structures are covered and discussed.Optimization techniques are explained,including metaheuristics,genetic algorithm,particle swarm,ant-colony,harmony search algorithm,and their applications with mentioned structure types.Linear and non-linear structures,including geometric and material nonlinearity,are distinguished.The role of optimization in active structures,structural design,seismic design,form-finding,and structural control is taken into account,and the most recent techniques and advancements are mentioned.
文摘An effective optimization method for the shape/sizing design of composite wing structures is presented with satisfying weight-cutting results. After decoupling, a kind of two-layer cycled optimization strategy suitable for these integrated shape/sizing optimization is obtained. The uniform design method is used to provide sample points, and approximation models for shape design variables. And the results of sizing optimization are construct- ed with the quadratic response surface method （QRSM）. The complex method based on QRSM is used to opti- mize the shape design variables and the criteria method is adopted to optimize the sizing design variables. Compared with the conventional method, the proposed algorithm is more effective and feasible for solving complex composite optimization problems and has good efficiency in weight cutting.
文摘Aim To introduce a new method of adaptive shape optimization (ASOP) based on three-dimensional structure boundary strength and optimize an engine bearing cap with the method. Methods Using the normal substance's property of thermal expansion and cooling shrinkage,the load which is proportional to the difference between the nodes' stress and their respective objective stress were applied to the corresponding variable nodes on the boundary.The thermal load made the nodes whose stress is greater than their objective stress expand along the boundary's normal direction and the nodes whose stress is less than objec- tive stress shrink in the opposite direction , This process would repeat until the stress on the boundary nodes was converge to the objective stress. Results The satisfied results have been obtained when optimizing an engine bearing cap.The mass of the bearing cap is reduced to 55 percent of the total. Conclusion ASOP is an efficient,practical and reliable method which is suitable for optimizing the shape of the continuous structures.
基金supported by the National Natural Science Foundation of China (Grant No. 51179061)the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20100094110014)
文摘The multi-objective optimization method was used for shape optimization of cement sand and gravel （CSG） dams in this study. The economic efficiency, the sensitivities of maximum horizontal displacement and maximum settlement of the dam to water level changes, the overall stability, and the overall strength security were taken into account during the optimization process. Three weight coefficient selection schemes were adopted to conduct shape optimization of a dam, and the case studies lead to the conclusion that both the upstream-and downstream dam slope ratios for the optimal cross-section equal 1：0.7, which is consistent with the empirically observed range of 1：0.6 to 1;0.8 for the upstream and downstream dam slope ratios of CSG dams. Therefore, the present study is of certain reference value for designing CSG dams.
基金Project supported by the National Natural Science Foundation of China (Nos.200112023 and 10032030).
文摘A new approach for the solution of truss shape and topology optimization problems under local and global stability constraints is proposed.By employing the cross sectional areas of each bar and some shape parameters as topology design variables,the difficulty arising from the jumping of buckling length phenomenon can be easily overcome without the necessity of introduc- ing the overlapping bars into the initial ground structure.Therefore computational efforts can be saved for the solution of this kind of problem.By modifying the elements of the stiffness matrix using Sigmoid function,the continuity of the objective and constraint functions with respect to shape design parameters can be restored to some extent.Some numerical examples demonstrate the effectiveness of the proposed method.
基金This research was financially supported by the National Natural Science Foundation of China(Grant Nos.51875466 and 51805436)the China Postdoctoral Science Foundation(Grant No.2019T120941)the China Scholarships Council(Grant No.201806290133).
文摘In this paper,a Double-stage Surrogate-based Shape Optimization(DSSO)strategy for Blended-Wing-Body Underwater Gliders(BWBUGs)is proposed to reduce the computational cost.In this strategy,a double-stage surrogate model is developed to replace the high-dimensional objective in shape optimization.Specifically,several First-stage Surrogate Models(FSMs)are built for the sectional airfoils,and the second-stage surrogate model is constructed with respect to the outputs of FSMs.Besides,a Multi-start Space Reduction surrogate-based global optimization method is applied to search for the optimum.In order to validate the efficiency of the proposed method,DSSO is first compared with an ordinary One-stage Surrogate-based Optimization strategy by using the same optimization method.Then,the other three popular surrogate-based optimization methods and three heuristic algorithms are utilized to make comparisons.Results indicate that the lift-to-drag ratio of the BWBUG is improved by 9.35%with DSSO,which outperforms the comparison methods.Besides,DSSO reduces more than 50%of the time that other methods used when obtaining the same level of results.Furthermore,some considerations of the proposed strategy are further discussed and some characteristics of DSSO are identified.
基金financially supported by the National Natural Science Foundation of China(Grant No.51308012)the Key Laboratory of Transportation Tunnel Engineering+1 种基金Ministry of EducationSouthwest Jiaotong University(Grant No.TTE2014-06)
文摘Subsea tunnel lining structures should be designed to sustain the loads transmitted from surrounding ground and groundwater during excavation. Extremely high pore-water pressure reduces the effective strength of the country rock that surrounds a tunnel, thereby lowering the arching effect and stratum stability of the structure. In this paper, the mechanical behavior and shape optimization of the lining structure for the Xiang＇an tunnel excavated in weathered slots are examined. Eight cross sections with different geometric parameters are adopted to study the mechanical behavior and shape optimization of the lining structure. The hyperstatic reaction method is used through finite element analysis software ANSYS. The mechanical behavior of the lining structure is evidently affected by the geometric parameters of crosssectional shape. The minimum safety factor of the lining structure elements is set to be the objective function. The efficient tunnel shape to maximize the minimum safety factor is identified. The minimum safety factor increases significantly after optimization. The optimized cross section significantly improves the mechanical characteristics of the lining structure and effectively reduces its deformation. Force analyses of optimization process and program are conducted parametrically so that the method can be applied to the optimization design of other similar structures. The results obtained from this study enhance our understanding of the mechanical behavior of the lining structure for subsea tunnels. These results are also beneficial to the optimal design of lining structures in general.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51875466 and 51805436)the Fundamental Research Funds for the Central Universities(Grant No.3102020HHZY030003)。
文摘As a type of autonomous underwater vehicle(AUV),underwater gliders(UG)are getting increasing attention in ocean exploration.To save energy and satisfy the mission requirements of a longer voyage,shape optimization for UGs has become a key technique and research focus.In this paper,a conventional UG,including its fuselage and hydrofoil,is optimized,which aims to decrease the average resistance in one motion cycle.To operate the optimization progress for the complex object,multiple free form deformation(FFD)volumes are established for geometric parameterization.High-fidelity simulation models are employed for objective function evaluation and gradients calculation.And sequential quadratic programming(SQP)method is adopted as an optimization algorithm.The optimization results show that there exists a UG with symmetrical and non-horizontal hydrofoils that has lower resistance.
基金Item Sponsored by National Science and Technology Support Program of China(2011BAF15B02)Natural Science Foundation of Hebei Province of China(E2012203108)+2 种基金Science and Technology Research Program of the Colleges and Universities in Hebei of China(ZD2014034)Independent Research Project of Yanshan University of China(14LGA003)Open Project of National Engineering Research Center for Equipment and Technology of Cold Rolling Strip of China(NECSR-201206)
文摘Tailor rolled blank （TRB） is a type of emerging material to produce lightweight vehicle parts. Transitional zoners shape is an important parameter for tailor rolled blank. It not only affects mold design and the local carrying capacity of the stamping parts, but also determines the maximum value and variation characteristics of rolling force. How to get the best transitional zone＇s shape is a key problem for production of tailor rolled blank. A double power function is put forward using for transitional curve, which is continuous and smooth at all connection points inde- pendent of its parameters, so the sudden change of mechanical parameters during rolling and forming process can be avoided. At the same time, the velocity formula and restriction for arbitrary transitional curve are derived to preset vertical velocity of the roller and judge whether the curve can be rolled successfully or not. Then, the finite element method （FEM） is used to verify the precision of velocity formula and study the mechanical characteristics of different curves. Finally, a method to obtain the optimal curve equation is put forward and verified.
基金This work was supported by the National Numerical Wind tunnel Project(Grant NNW2018-ZT1B01)the National Natural Science Foundation of China(Grant 91852115).
文摘Adjoint method is widely used in aerodynamic design because only once solution of flow field is required for it to obtain the gradients of all design variables. However, the computational cost of adjoint vector is approximately equal to that of flow computation. In order to accelerate the solution of adjoint vector and improve the efficiency of adjoint-based optimization, machine learning for adjoint vector modeling is presented. Deep neural network (DNN) is employed to construct the mapping between the adjoint vector and the local flow variables. DNN can efficiently predict adjoint vector and its generalization is examined by a transonic drag reduction of NACA0012 airfoil. The results indicate that with negligible computational cost of the adjoint vector, the proposed DNN-based adjoint method can achieve the same optimization results as the traditional adjoint method.
基金the National Natural Science Foundation of China(No.51009087)
文摘The hull form optimization concerns one of the most important applications of wave-making resistance theories.In recent years,scholars can determine the hull form by using the optimization method based on the computational fluid dynamics(CFD)and other mathematical techniques.In this paper,the hull form optimization method based on the Rankine source method and nonlinear programming(NLP)is discussed;in the optimization process,a hull form modification function is introduced to represent an improved hull surface and to generate a new smooth hull surface by changing its frame lines and bow stem profiles under the prescribed design constraints. Numerical example is given for a practical container hull form.Finally,shape optimization of bow bulls is shown for non-protruding and protruding bow bulls.This study presents a simplified and practical design method to the select frame lines of bow bulls.
基金supported by National Natural Science Foundation of China(Grant No.50575098)
文摘Smoothly stitching multiple surfaces mainly represented by B-spline or NURBS together is an extremely important issue in complex surfaces modeling and reverse engineering.In recent years,a lot of progress has been made in smooth join of non-trimmed surface patches,while there has been seldom research on smoothly stitching trimmed surface patches together.This paper studies the problem of global continuity adjustment,damaged hole repair and local shape optimization for complex trimmed surface model,and presents a uniform scheme to deal with continuity adjustment of trimmed surfaces and geometric repair of local broken region.Constrained B-spline surface refitting technique and trim calculation are first utilized to achieve global G^1 continuity,and then local shape optimization functional is adopted to reduce fitting error and improve local quality of refitted surface patch.The proposed approach is applied to a discontinuity ship hull surface model with an irregular hole,and the result demonstrates the validation of our method.Furthermore,on the premise of global continuity,the proposed locally repairing damaged surface model provides a better foundation for following research work,such as topology recovery technique for complex surface model after geometric repair.
文摘This paper presents a novel optimization technique for an efficient multi-fidelity model building approach to reduce computational costs for handling aerodynamic shape optimization based on high-fidelity simulation models. The wing aerodynamic shape optimization problem is solved by dividing optimization into three steps—modeling 3D（high-fidelity） and 2D（lowfidelity） models, building global meta-models from prominent instead of all variables, and determining robust optimizing shape associated with tuning local meta-models. The adaptive robust design optimization aims to modify the shape optimization process. The sufficient infilling strategy—known as adaptive uniform infilling strategy—determines search space dimensions based on the last optimization results or initial point. Following this, 3D model simulations are used to tune local meta-models. Finally, the global optimization gradient-based method—Adaptive Filter Sequential Quadratic Programing（AFSQP） is utilized to search the neighborhood for a probable optimum point. The effectiveness of the proposed method is investigated by applying it, along with conventional optimization approach-based meta-models, to a Blended Wing Body（BWB） Unmanned Aerial Vehicle（UAV）. The drag coefficient is defined as the objective function, which is subjected to minimum lift coefficient bounds and stability constraints. The simulation results indicate improvement in meta-model accuracy and reduction in computational time of the method introduced in this paper.
基金National Natural Science Foundation of China (5 9875 0 3 7)
文摘Based on the theory of reliability-based structural shape optimization, exact expressions of the sensibility using the stochastic finite element method for contact problems were derived in detail, and the basic steps of structural optimization were given. A coattail-type tenon/mortise of an aero-engine was optimized. In this model, the maximum equivalent stress of the nodes on the boundary of the tenon was the objective function; the width of tooth’s neck and the side surface’s slope angle of a tenon were design variables, with constraints of tension stress, extrusion stress and reliability index. The result showed that the distributions of the contact pressure between tenon and mortise, the equivalence stress and reliability index were more reasonable. It validates the correctness of the optimization model and the reliability-based structural shape optimization, and provides valuable references for structural design of the tenon/mortise.
基金This project was financially supported by the National Natural Science Foundation of China(Grant No.59895410)
文摘With the introduction of the design variables of nodal coordinates, which reflect the embedded depth of the pile and the jacket bed height, a shape optimum design model for offshore jacket platforms is established. A sequential two-level optimum algorithm is developed based on the design variable gradation. On the basis of the finite element method, the sensitivity of the objective function and nodal displacement is analyzed. As an example, the BZ281 oil storage offshore platform, which ties in the Bohai oil field, is designed with the shape optimum model. The results are compared with the cross-section optimum design. The tendency of design variables and its reasons in the two methods are analyzed. In the shape optimum design, the value of objective function is obviously smaller than that of the initial design and the cross-section optimum design. Therefore, the advantage of structure shape optimum design for jacket platforms is remarkable.
基金the National Key Research and Development Plan of China(No.2016YFC0301300)
文摘As a new kind of autonomous underwater vehicle,bionic submersible has many merits such as high efficiency and low costs.In order to obtain such advantages,it is a good way to simulate the shapes of marine animals and apply them to the design of artificial underwater vehicle.In this paper,an optimization system of airfoils is proposed by the improved class-shape-transformation(CST)parameterization method and genetic algorithm(GA).The appearance of a manta-ray-inspired underwater vehicle is rebuilt using the optimal sectional airfoils obtained by the proposed optimization system.Computational simulations are carried out to investigate the hydrodynamic performance of the submersible using the commercial computational fluid dynamics(CFD)code Fluent.The results demonstrate that the maximum thickness of the vehicle increases by 9%,which means the loading capacity is increased.Moreover,the underwater vehicle shows better hydrodynamic performance,and the lift-drag ratio of initial design is increased by more than 10%using the presented optimization system of airfoils.
