Multifield Variational Finite Element Sectional Analysis of Composite Beams

DHADWAL MANOJ KUMAR,정성남 한국복합재료학회 2017 Composites research Vol.30 No.6

A multifield variational formulation is developed for the finite element (FE) cross-sectional analysis of composite beams. The cross-sectional warping displacements and sectional stresses are considered to be the primary variables through the application of Reissner’s partially mixed principle. The warping displacements are modeled using generic FE shape functions with nonlinear distribution over the beam section. A generalized Timoshenko level stiffness matrix is derived which incorporates the effects of elastic couplings, transverse shear, and Poisson’s deformations. The accuracy of the present analysis is validated for the stiffness constants and elastostatic responses of composite box beams which correlate well with the experimental data and other state-of-the-art approaches.

Effect of Three-dimensional Warping on Stiffness Constants of Closed Section Composite Beams

Dhadwal, Manoj Kumar,Jung, Sung Nam The Korean Society for Aeronautical and Space Scie 2017 International Journal of Aeronautical and Space Sc Vol.18 No.3

This paper focuses on the investigation of three-dimensional (3D) warping effect on the stiffness constants of composite beams with closed section profiles. A finite element (FE) cross-sectional analysis is developed based on the Reissner's multifield variational principle. The 3D in-plane and out-of-plane warping displacements, and sectional stresses are approximated as linear functions of generalized sectional stress resultants at the global level and as FE shape functions at the local sectional level. The classical elastic couplings are taken into account which include transverse shear and Poisson deformation effects. A generalized Timoshenko level $6{\times}6$ stiffness matrix is computed for closed section composite beams with and without warping. The effect of neglecting the 3D warping on stiffness constants is shown to be significant indicating large errors as high as 93.3%.

Particle Swarm Assisted Genetic Algorithm for the Optimal Design of Flexbeam Sections

Dhadwal, Manoj Kumar,Lim, Kyu Baek,Jung, Sung Nam,Kim, Tae Joo The Korean Society for Aeronautical and Space Scie 2013 International Journal of Aeronautical and Space Sc Vol.14 No.4

This paper considers the optimum design of flexbeam cross-sections for a full-scale bearingless helicopter rotor, using an efficient hybrid optimization algorithm based on particle swarm optimization, and an improved genetic algorithm, with an effective constraint handling scheme for constrained nonlinear optimization. The basic operators of the genetic algorithm, of crossover and mutation, are revisited, and a new rank-based multi-parent crossover operator is utilized. The rank-based crossover operator simultaneously enhances both the local, and the global exploration. The benchmark results demonstrate remarkable improvements, in terms of efficiency and robustness, as compared to other state-of-the-art algorithms. The developed algorithm is adopted for two baseline flexbeam section designs, and optimum cross-section configurations are obtained with less function evaluations, and less computation time.

Generalized multifield variational formulation with interlaminar stress continuity for multilayered anisotropic beams

Dhadwal, Manoj Kumar,Jung, Sung Nam Elsevier 2019 Composites Part B, Engineering Vol.168 No.-

<P><B>Abstract</B></P> <P>Classical finite element (FE) beam theories are based on displacement formulation requiring derivatives to obtain the stress components which leads to a large number of FEs and depend on nodal averaging techniques for achieving sufficient accuracy. In this work, a new multifield variational based FE formulation is proposed within the cross-sectional framework of multilayered composite beams for accurate and efficient predictions of sectional stiffness constants and stresses. The interlaminar stress continuity is not assumed a priori and inherently incorporated using the Hellinger-Reissner principle along with a global stress equilibrium constraint, directly computing the stresses at nodal locations. The three-dimensional (3D) stresses and warping deformations are considered as primary variables which inherently incorporate elastic coupling effects related to transverse shear and Poisson deformations. The formulation results in a generalized fully-coupled 6 × 6 sectional stiffness matrix considering elastic couplings. The efficacy of the present analysis is substantiated for thin-walled composite beams with elastic couplings. An excellent correlation is achieved for the elastostatic response as compared with the 3D FE and experimental results. The stresses obtained by the multifield analysis are in accord with detailed 3D FE solutions for various loading conditions while computed at a much reduced computational cost. Improved predictions of interlaminar stresses and stress concentrations are achieved compared to displacement-based approach along with the correct identification of continuity across layer interfaces. The effect of fiber orientation on the interlaminar stresses is also shown to be significant which can be useful for damage analysis of composite beams.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A multifield variational finite element analysis developed for anisotropic beams. </LI> <LI> •3D stresses with interlaminar continuity modeled as unknowns without a priori assumptions or post-processing technique. </LI> <LI> •Excellent correlation obtained as compared with 3D finite element analysis while predicting interlaminar stresses and stress concentrations at corners correctly. </LI> <LI> •Influence of fiber angles on interlaminar stresses demonstrated for coupled beams. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Optimal Design of Flexbeam Cross-Sections using Particle Swarm Assisted Genetic Algorithm

Manoj Kumar Dhadwal,Kyubaek Lim,Sung Nam Jung,Tae Joo Kim 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.11

This paper presents the optimal design of flexbeam cross-sections for a full-scale bearingless helicopter. A hybrid optimization algorithm based on the particle swarm optimization and real-coded genetic algorithm is used combined with an effective constraint handling scheme. A new rank-based crossover is developed for the real-coded genetic algorithm based on the mutation operator of differential evolution and heuristic crossover. The suggested crossover operator improves both the efficiency as well as the global exploration of the solutions. The particle swarm optimization is then hybridized with the improved genetic algorithm. Euclidean-distance based niching is implemented in the genetic algorithm to maintain the population diversity. The developed algorithm is used for the design of two configurations of the flexbeam cross-section. The optimal results are obtained within very few function evaluations and less CPU time.

Recent Developments and Challenges in the Cross-sectional Analysis of Composite Beams

Manoj Kumar Dhadwal,Martin Alexander Eder,Ali Sarhadi,Sergei Semenov,Kim Branner 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

Improved Structural Behavior of Multiscale Composite Wind Turbine Blades Reinforced with Graphene Nanoplatelets

Manoj Kumar Dhadwal,Do-Nyun Kim(김도년) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12

A Hybrid of Particle Swarm and Genetic Algorithm for Constrained Real-Parameter Optimization

Manoj Kumar Dhadwal,Sung Nam Jung,Tae Joo Kim 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.4

This paper presents a hybrid evolutionary algorithm based on particle swarm optimization and genetic algorithm. Levy flights based random walk is introduced in the global-best particle swarm algorithm to enhance the global exploration. A new rank-based multiparent crossover operator is proposed for the realcoded genetic algorithm which improves both the local as well as the global search. The constraints are handled using a feasible population based approach. The numerical experiments are performed on benchmark constrained nonlinear problems including the engineering optimization problems. The results show significant improvements as compared to the other state-of-the-art algorithms in terms of efficiency and robustness.

Effect of Three-dimensional Warping on Stiffness Constants of Closed Section Composite Beams

Manoj Kumar Dhadwal,Sung Nam Jung 한국항공우주학회 2017 International Journal of Aeronautical and Space Sc Vol.18 No.3

This paper focuses on the investigation of three-dimensional (3D) warping effect on the stiffness constants of composite beams with closed section profiles. A finite element (FE) cross-sectional analysis is developed based on the Reissner"s multifield variational principle. The 3D in-plane and out-of-plane warping displacements, and sectional stresses are approximated as linear functions of generalized sectional stress resultants at the global level and as FE shape functions at the local sectional level. The classical elastic couplings are taken into account which include transverse shear and Poisson deformation effects. A generalized Timoshenko level 6×6 stiffness matrix is computed for closed section composite beams with and without warping. The effect of neglecting the 3D warping on stiffness constants is shown to be significant indicating large errors as high as 93.3%.

General Purpose Cross-sectional Analysis Program for Nonhomogeneous Anisotropic Beams

Manoj Kumar Dhadwal,정성남 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.4

전문 단면해석 프로그램을 개선하여 비균질 및 이방 특성을 갖는 복합재료 보 해석을 수행할 수 있도록 확장하였다. 보 이론은 St. Venant 가정을 기반으로 탄성론에 입각하여 엄격하게 전개하였으며, 복합재료의 연계특성 및 면외워핑을 고려하도록 구성하였다. 단면의 전단변형 및 면내워핑 효과는 무시하였다. 도출된 강성계수는 Euler-Bernoulli 및 Vlasov 수준을 기술한다. 개발된 프로그램은 강성치, 관성치, 중심치를 포함한다. 본 프로그램을 이용하여 비균질 형상의 등방성 보 및 복합재료 상자 보에 대한 단면해석을 수행하였으며, 여타의 최신 해석결과와 대비하여 만족할 만한 수준의 결과를 얻었다. The current version of a finite element-based cross-sectional analysis program is refined to cover nonhomogeneous and anisotropic beams. The formulation is based on the elasticity theory considering the St. Venant’s beam assumptions for nonhomogeneous anisotropic beams. The approach includes the effects of classical elastic couplings and non-classical out-of-plane torsional warpings. The effects of transverse shear deformation and in-plane warping are neglected. The stiffness matrix is computed at Euler-Bernoulli level for bending and Vlasov level for torsion. The analysis is capable of calculating the sectional mass per unit length, inertial properties, and section offsets such as shear center, tension center, and mass center. The results show an excellent correlation for highly heterogeneous isotropic beam and reasonable agreement for extension-torsion coupled composite box-beam compared to other state-of-the-art tools.