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Kazuhiro Saitou - One of the best experts on this subject based on the ideXlab platform.
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DETC2004-57301 DECOMPOSITION-BASED ASSEMBLY SYNTHESIS OF SPACE FRAME STRUCTURES USING JOINT LIBRARY
2020Co-Authors: Naesung Lyu, Kazuhiro SaitouAbstract:ABSTRACT This paper presents a method for identifying the optimal designs of components and joints in the space frame body structures of passenger vehicles considering Structural characteristics, manufacturability and assembleability. Dissimilar to our previous work based on graph decomposition, the problem is posed as a simultaneous determination of the locations and types of joints in a structure and the cross sections of the joined Structural Frames, selected from a predefined joint library. The joint library is a set of joint designs containing the geometry of the feasible joints at each potential joint location and the cross sections of the joined Frames, associated with their Structural characteristics as equivalent torsional springs obtained from the finite element analyses of the detailed joint geometry. Structural characteristics of the entire structure are evaluated by finite element analyses of a beam-spring model constructed from the selected joints and joined Frames. Manufacturability and assembleability are evaluated as the manufacturing and assembly costs estimated from the geometry of the components and joints, respectively. The optimization problem is solved by a multi-objective genetic algorithm using a direct crossover. A case study on an aluminum space frame (ASF) of a middle size passenger vehicle is discussed
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optimal subassembly partitioning of space frame structures for in process dimensional adjustability and stiffness
Journal of Mechanical Design, 2006Co-Authors: Naesung Lyu, Byungwoo Lee, Kazuhiro SaitouAbstract:A method for optimally synthesizing multicomponent Structural assemblies of an aluminum space frame (ASF) vehicle body is presented, which simultaneously considers Structural stiffness, manufacturing and assembly costs and dimensional integrity under a unified framework based on joint libraries. The optimization problem is posed as a simultaneous determination of the location and feasible types of joints in a structure selected from the predefined joint libraries, combined with the size optimization for the cross sections of the joined Structural Frames. The Structural stiffness is evaluated by finite element analyses of a beam-spring model modeling the joints and joined Frames. Manufacturing and assembly costs are estimated based on the geometries of the components and joints. Dissimilar to the enumerative approach in our previous work, dimensional integrity of a candidate assembly is evaluated as the adjustability of the given critical dimensions, using an internal optimization routine that finds the optimal subassembly partitioning of an assembly for in-process adjustability. The optimization problem is solved by a multiobjective genetic algorithm. An example on an ASF of the midsize passenger vehicle is presented, where the representative designs in the Pareto set are examined with respect to the three design objectives.
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decomposition based assembly synthesis of space frame structures using joint library
Journal of Mechanical Design, 2006Co-Authors: Naesung Lyu, Kazuhiro SaitouAbstract:This paper presents a method for identifying the optimal designs of components and joints in the space frame body structures of passenger vehicles considering Structural characteristics, manufacturability and assembleability. Dissimilar to our previous work based on graph decomposition, the problem is posed as a simultaneous determination of the locations and types of joints in a structure and the cross sections of the joined Structural Frames, selected from a predefined joint library. The joint library is a set of joint designs containing the geometry of the feasible joints at each potential joint location and the cross sections of the joined Frames, associated with their Structural characteristics as equivalent torsional springs obtained from the finite element analyses of the detailed joint geometry. Structural characteristics of the entire structure are evaluated by finite element analyses of a beam-spring model constructed from the selected joints and joined Frames. Manufacturability and assembleability are evaluated as the manufacturing and assembly costs estimated from the geometry of the components and joints, respectively. The optimization problem is solved by a multi-objective genetic algorithm using a direct crossover. A case study on an aluminum space frame (ASF) of a middle size passenger vehicle is discussed.
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decomposition based assembly synthesis of space frame structures using joint library
Design Automation Conference, 2004Co-Authors: Naesung Lyu, Kazuhiro SaitouAbstract:This paper presents a method for identifying the optimal designs of components and joints in the space frame body structures of passenger vehicles considering Structural characteristics, manufacturability and assembleability. Dissimilar to our previous work based on graph decomposition, the problem is posed as a simultaneous determination of the locations and types of joints in a structure and the cross sections of the joined Structural Frames, selected from a predefined joint library. The joint library is a set of joint designs containing the geometry of the feasible joints at each potential joint location and the cross sections of the joined Frames, associated with their Structural characteristics as equivalent torsional springs obtained from the finite element analyses of the detailed joint geometry. Structural characteristics of the entire structure are evaluated by finite element analyses of a beam-spring model constructed from the selected joints and joined Frames. Manufacturability and assembleability are evaluated as the manufacturing and assembly costs estimated from the geometry of the components and joints, respectively. The optimization problem is solved by a multi-objective genetic algorithm using a direct crossover. A case study on an aluminum space frame (ASF) of a middle size passenger vehicle is discussed.Copyright © 2004 by ASME
T Machaly - One of the best experts on this subject based on the ideXlab platform.
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factors affecting the machinability of gfr epoxy composites
Composite Structures, 2004Co-Authors: I A Elsonbaty, U A Khashaba, T MachalyAbstract:Abstract Drilling is an essential operation in the assembly of the Structural Frames of automobiles and aircrafts. The life of the joint can be critically affected by the quality of the drilled holes. The main objective of the present paper is to investigate the influence of some parameters on the thrust force, torque and surface roughness in drilling processes of fiber-reinforced composite materials. These parameters include cutting speed, feed, drill size and fiber volume fraction. The quasi-isotropic composite materials were manufactured from randomly oriented glass fiber-reinforced epoxy, with various values of fiber volume fractions ( V f ), using hand-lay-up technique. Two components drill dynamometer has been designed and manufactured to measure the thrust and torque during the drilling process. The dynamometer was connected with a data acquisition, which installed in a PC computer. This set-up enable to monitor and record the thrust force and torque with the aid of a computer program that designed using Lab View utilities. The results indicate that the start point of torque cycle is delayed by few seconds (depending on the value of feed) than the thrust force. This time is consumed to penetrate the specimen by chiseling edge. After the thrust force reached its maximum value it is gradually decreased during the full engagement of the drill and goes to zero when both the chisel edge and the cutting lips have exit of the laminate. In contrast the torque was gradually increased up to the end of the cycle and sudden jump to a value about 10 times the peak value. Cutting speed has insignificant effect on the thrust force and surface roughness of epoxy resin. For glass fiber-reinforced epoxy composites (GFREC) with V f =9.8–23.7% the thrust force and torque were decreased with increasing cutting speed. On contrast increasing feed, drill size and fiber volume fractions lead to increase the thrust force and torque. The drilled holes of GFREC with lower V f ratio at lower feed have greater roughness than that drilled at higher feed. Specimens with high V f ratio have a contrary behavior. Drill diameter combined with feed has a significant effect on surface roughness.
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factors affecting the machinability of gfr epoxy composites
Composite Structures, 2004Co-Authors: I A Elsonbaty, U A Khashaba, T MachalyAbstract:Abstract Drilling is an essential operation in the assembly of the Structural Frames of automobiles and aircrafts. The life of the joint can be critically affected by the quality of the drilled holes. The main objective of the present paper is to investigate the influence of some parameters on the thrust force, torque and surface roughness in drilling processes of fiber-reinforced composite materials. These parameters include cutting speed, feed, drill size and fiber volume fraction. The quasi-isotropic composite materials were manufactured from randomly oriented glass fiber-reinforced epoxy, with various values of fiber volume fractions ( V f ), using hand-lay-up technique. Two components drill dynamometer has been designed and manufactured to measure the thrust and torque during the drilling process. The dynamometer was connected with a data acquisition, which installed in a PC computer. This set-up enable to monitor and record the thrust force and torque with the aid of a computer program that designed using Lab View utilities. The results indicate that the start point of torque cycle is delayed by few seconds (depending on the value of feed) than the thrust force. This time is consumed to penetrate the specimen by chiseling edge. After the thrust force reached its maximum value it is gradually decreased during the full engagement of the drill and goes to zero when both the chisel edge and the cutting lips have exit of the laminate. In contrast the torque was gradually increased up to the end of the cycle and sudden jump to a value about 10 times the peak value. Cutting speed has insignificant effect on the thrust force and surface roughness of epoxy resin. For glass fiber-reinforced epoxy composites (GFREC) with V f =9.8–23.7% the thrust force and torque were decreased with increasing cutting speed. On contrast increasing feed, drill size and fiber volume fractions lead to increase the thrust force and torque. The drilled holes of GFREC with lower V f ratio at lower feed have greater roughness than that drilled at higher feed. Specimens with high V f ratio have a contrary behavior. Drill diameter combined with feed has a significant effect on surface roughness.
Akinori Karasu - One of the best experts on this subject based on the ideXlab platform.
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design wind loads for Structural Frames of flat long span roofs gust loading factor for a Structurally integrated type
Journal of Wind Engineering and Industrial Aerodynamics, 1997Co-Authors: Yasushi Uematsu, Motohiko Yamada, Akinori KarasuAbstract:The primary purpose of this study is to present simple formulae for estimating the design wind loads for the Structural Frames of flat long-span roofs taking account on their dynamic response of turbulent wind forces. This paper discusses the design wind loads for a Structurally integrated type of roof, such as a space truss. The roof structure is supposed to act like an elastic plate under wind loadings. The first modal force acting on the roof was measured for various wind directions in two turbulent boundary layers. Based on the experimental results, the gust loading factor, defined as the ratio of the maximum peak response to the mean response in a time duration, was computed. The effects of the following parameters on the effective wind load acting on the roof structure are investigated: (i) turbulence intensity of the approaching flow, (ii) wind direction, and (iii) building geometry. An empirical formula for the gust loading factor is provided as a function of these parameters. The application of this formula to general conditions is discussed.
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design wind loads for Structural Frames of flat long span roofs gust loading factor for the beams supporting roofs
Journal of Wind Engineering and Industrial Aerodynamics, 1997Co-Authors: Yasushi Uematsu, Motohiko Yamada, Akinori KarasuAbstract:The primary purpose of this study is to provide simple formulas for estimating the design wind loads for the Structural Frames of flat long-span roofs considering their dynamic response to turbulent wind forces. This paper presents a discussion of the gust loading factor for beams supporting flat roofs. The first modal force acting on the beam was measured in two turbulent boundary layers for various beam locations and wind directions. Based on the experimental results, the gust loading factor, defined as the ratio of the maximum peak response to the mean response in a time duration, was computed. The effects of the following parameters on the gust loading factor are investigated: (i) turbulence intensity of the approaching flow, (ii) wind direction, (iii) span-to-height ratio of the building, and (iv) location of the beam. An empirical formula for the gust loading factor is provided as a function of these parameters as well as of the Structural properties of the beam. The application of the formula to general conditions is also discussed.
Gordon P Warn - One of the best experts on this subject based on the ideXlab platform.
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Topology optimization of Structural Frames considering material nonlinearity and time-varying excitation
Structural and Multidisciplinary Optimization, 2021Co-Authors: Navid Changizi, Gordon P WarnAbstract:An approach for the topology optimization of structures composed of nonlinear beam elements under time-varying excitation is presented. Central to this approach is a hysteretic beam finite element model that accounts for distributed plasticity and axial-moment interaction through appropriate hysteretic interpolation functions and yield/capacity function, respectively. Nonlinearity is represented via the hysteretic variables for curvature and axial deformations that evolve according to first order nonlinear ordinary differential equations (ODEs), referred to as evolution equations, and the yield function. Hence, the governing dynamic equilibrium equations and hysteretic evolution equations can thus be concisely presented as a system of first-order nonlinear ODEs that can be solved using general ODE solvers without the need for linearization. The approach is applied for the design of frame structures with an objective to minimize the total volume in the domain, such that the maximum displacement at specified node(s) satisfies a specified constraint (i.e., drift limit) for the given excitation. The maximum displacement is approximated using the p-norm and thus permits the completion of the analytical sensitivities required for gradient-based updating. Several numerical examples are presented to demonstrate the approach for the design of Structural Frames subjected to pulse, harmonic, and seismic base excitation. Topologies obtained using the suggested, nonlinear approach are compared to solutions obtained from topology optimization problems assuming linear-elastic material behavior. These comparisons show that although similarities between the designs exist, in general the nonlinear designs differ in composition and, importantly, outperform the linear designs when assessed by nonlinear dynamic analysis.
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stochastic stress based topology optimization of Structural Frames based upon the second deviatoric stress invariant
Engineering Structures, 2020Co-Authors: Navid Changizi, Gordon P WarnAbstract:Abstract This work pertains to the stochastic stress-based topology optimization of frame structures considering uncertainty. Specifically, this paper presents an investigation of the second deviatoric stress invariant, J 2 , as the measure of stress in the domain where the objective is to minimize the maximum of the expected values of the stress invariant. Analytical expressions for the expected value of the J 2 invariant are developed employing the perturbation approach. The premise being that the J 2 invariant eliminates the square root operator that would otherwise be present if using the von Mises stress, and by eliminating this operator, the nonlinearity in the functional mapping between the random input (magnitude and direction of external forces) and uncertain output (expected values of stress) is reduced. Hence, an improved accuracy can be achieved with an analytical approximation of a given order. The analytical expressions of the expected value of the J 2 invariant to the second order are obtained based on a Taylor series expansion along with the associated sensitivities for gradient-based optimization. The analytical expressions are implemented in an optimization scheme and applied for the design of three ground structures considering different variability in the input random variables. For each example, the relative error between the maximum of the expected values of the J 2 invariant obtained using the analytical expressions and corresponding values evaluated by performing stochastic finite element analysis, whereby the input distribution is sampled using Monte Carlo methods, finite element simulation performed for each sample realization, then computing the expected value of the stress measure using straightforward statistical expressions, and finally estimation of the maximum via the p-norm, were observed to be less than 2%, even for a coefficient of variation of 0.4. The optimized designs were again analyzed using the von Mises stress and the relative error again computed with respect to those obtained from Monte Carlo sampling and finite element simulation. In general, the relative error using the analytical expressions of the von Mises stress was greater than, except in a couple instances, those obtained using the J 2 invariant.
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A sequential decision process for the system-level design of Structural Frames
Structural and Multidisciplinary Optimization, 2017Co-Authors: Mehmet Unal, Gordon P Warn, Simon W. Miller, Jaskanwal P. S. Chhabra, Michael A. Yukish, Timothy W. SimpsonAbstract:The building design community is currently experiencing a shift towards generating more resilient and sustainable designs that are also safe and economic. Integrating these broad, often conflicting, factors into design causes the design process to become more complex, the decisions more difficult, and a need for higher fidelity (and more expensive) modeling efforts to gain insight to resolve these tradeoffs. Set-based design is a promising alternative to traditional point-based design for such complex design problems because many design concepts are generated, refined and carefully eliminated throughout the process thereby maintaining significant freedom in the early stages of design. There is an emerging concept of closely coupling set-based design with model-based simulation to systematically contract the design space through a sequence of modeling efforts in which bounding models are constructed to guarantee the antecedent model only eliminates design alternatives that are dominated when analyzed using a subsequent higher fidelity model. In this paper, the concept of the sequential decision process is explored for the system-level design of seismic-resisting Structural Frames using nonlinear static analysis. Bounding models are derived for this design problem that are sufficiently general for various types of Structural Frames. The merit of the novel approach lies in giving designers the ability to search the tradespace exhaustively, arriving at the global minimum with a reduced cost by comparison to a full evaluation using the highest fidelity model while also providing the freedom to retain dominated and non-dominated solutions.
Naesung Lyu - One of the best experts on this subject based on the ideXlab platform.
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DETC2004-57301 DECOMPOSITION-BASED ASSEMBLY SYNTHESIS OF SPACE FRAME STRUCTURES USING JOINT LIBRARY
2020Co-Authors: Naesung Lyu, Kazuhiro SaitouAbstract:ABSTRACT This paper presents a method for identifying the optimal designs of components and joints in the space frame body structures of passenger vehicles considering Structural characteristics, manufacturability and assembleability. Dissimilar to our previous work based on graph decomposition, the problem is posed as a simultaneous determination of the locations and types of joints in a structure and the cross sections of the joined Structural Frames, selected from a predefined joint library. The joint library is a set of joint designs containing the geometry of the feasible joints at each potential joint location and the cross sections of the joined Frames, associated with their Structural characteristics as equivalent torsional springs obtained from the finite element analyses of the detailed joint geometry. Structural characteristics of the entire structure are evaluated by finite element analyses of a beam-spring model constructed from the selected joints and joined Frames. Manufacturability and assembleability are evaluated as the manufacturing and assembly costs estimated from the geometry of the components and joints, respectively. The optimization problem is solved by a multi-objective genetic algorithm using a direct crossover. A case study on an aluminum space frame (ASF) of a middle size passenger vehicle is discussed
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optimal subassembly partitioning of space frame structures for in process dimensional adjustability and stiffness
Journal of Mechanical Design, 2006Co-Authors: Naesung Lyu, Byungwoo Lee, Kazuhiro SaitouAbstract:A method for optimally synthesizing multicomponent Structural assemblies of an aluminum space frame (ASF) vehicle body is presented, which simultaneously considers Structural stiffness, manufacturing and assembly costs and dimensional integrity under a unified framework based on joint libraries. The optimization problem is posed as a simultaneous determination of the location and feasible types of joints in a structure selected from the predefined joint libraries, combined with the size optimization for the cross sections of the joined Structural Frames. The Structural stiffness is evaluated by finite element analyses of a beam-spring model modeling the joints and joined Frames. Manufacturing and assembly costs are estimated based on the geometries of the components and joints. Dissimilar to the enumerative approach in our previous work, dimensional integrity of a candidate assembly is evaluated as the adjustability of the given critical dimensions, using an internal optimization routine that finds the optimal subassembly partitioning of an assembly for in-process adjustability. The optimization problem is solved by a multiobjective genetic algorithm. An example on an ASF of the midsize passenger vehicle is presented, where the representative designs in the Pareto set are examined with respect to the three design objectives.
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decomposition based assembly synthesis of space frame structures using joint library
Journal of Mechanical Design, 2006Co-Authors: Naesung Lyu, Kazuhiro SaitouAbstract:This paper presents a method for identifying the optimal designs of components and joints in the space frame body structures of passenger vehicles considering Structural characteristics, manufacturability and assembleability. Dissimilar to our previous work based on graph decomposition, the problem is posed as a simultaneous determination of the locations and types of joints in a structure and the cross sections of the joined Structural Frames, selected from a predefined joint library. The joint library is a set of joint designs containing the geometry of the feasible joints at each potential joint location and the cross sections of the joined Frames, associated with their Structural characteristics as equivalent torsional springs obtained from the finite element analyses of the detailed joint geometry. Structural characteristics of the entire structure are evaluated by finite element analyses of a beam-spring model constructed from the selected joints and joined Frames. Manufacturability and assembleability are evaluated as the manufacturing and assembly costs estimated from the geometry of the components and joints, respectively. The optimization problem is solved by a multi-objective genetic algorithm using a direct crossover. A case study on an aluminum space frame (ASF) of a middle size passenger vehicle is discussed.
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decomposition based assembly synthesis of space frame structures using joint library
Design Automation Conference, 2004Co-Authors: Naesung Lyu, Kazuhiro SaitouAbstract:This paper presents a method for identifying the optimal designs of components and joints in the space frame body structures of passenger vehicles considering Structural characteristics, manufacturability and assembleability. Dissimilar to our previous work based on graph decomposition, the problem is posed as a simultaneous determination of the locations and types of joints in a structure and the cross sections of the joined Structural Frames, selected from a predefined joint library. The joint library is a set of joint designs containing the geometry of the feasible joints at each potential joint location and the cross sections of the joined Frames, associated with their Structural characteristics as equivalent torsional springs obtained from the finite element analyses of the detailed joint geometry. Structural characteristics of the entire structure are evaluated by finite element analyses of a beam-spring model constructed from the selected joints and joined Frames. Manufacturability and assembleability are evaluated as the manufacturing and assembly costs estimated from the geometry of the components and joints, respectively. The optimization problem is solved by a multi-objective genetic algorithm using a direct crossover. A case study on an aluminum space frame (ASF) of a middle size passenger vehicle is discussed.Copyright © 2004 by ASME
