scholarly journals Wave sensitivity analysis for periodic and arbitrarily complex composite structures

2017 ◽  
Vol 34 (5) ◽  
pp. 1572-1597 ◽  
Author(s):  
Dimitrios Chronopoulos ◽  
Manuel Collet ◽  
Mohamed Ichchou
Keyword(s):  
Composite Structures ◽  
Dynamic Performance ◽  
Fe Modelling ◽  
Structural Dynamic ◽  
Content Type ◽  
Structural Modifications ◽  
Discrete Approach ◽  
Stiffness Matrices ◽  
Periodic Composite ◽  
The Waves

Purpose This paper aims to present the development of a numerical continuum-discrete approach for computing the sensitivity of the waves propagating in periodic composite structures. The work can be directly used for evaluating the sensitivity of the structural dynamic performance with respect to geometric and layering structural modifications. Design/methodology/approach A structure of arbitrary layering and geometric complexity is modelled using solid finite element (FE). A generic expression for computing the variation of the mass and the stiffness matrices of the structure with respect to the material and geometric characteristics is hereby given. The sensitivity of the structural wave properties can thus be numerically determined by computing the variability of the corresponding eigenvalues for the resulting eigenproblem. The exhibited approach is validated against the finite difference method as well as analytical results. Findings An intense wavenumber dependence is observed for the sensitivity results of a sandwich structure. This exhibits the importance and potential of the presented tool with regard to the optimization of layered structures for specific applications. The model can also be used for computing the effect of the inclusion of smart layers such as auxetics and piezoelectrics. Originality/value The paper presents the first continuum-discrete approach specifically developed for accurately and efficiently computing the sensitivity of the wave propagation data for periodic composite structures irrespective of their size. The considered structure can be of arbitrary layering and material characteristics as FE modelling is used.

Studies Regarding the Architectural Design of Various Composites and Nanofibres Used in Dental Medicine

2018 ◽  
Vol 69 (2) ◽  
pp. 328-331
Author(s):  
Irina Gradinaru ◽  
Leonard Ignat ◽  
Cristina Gena Dascalu ◽  
Laurentiu Valentin Soroaga ◽  
Magda Ecaterina Antohe
Keyword(s):  
Composite Structures ◽  
Architectural Design ◽  
Dental Restoration ◽  
Fibrillar Structure ◽  
Fiber Post ◽  
Fiber Glass ◽  
Full Agreement ◽  
Sem Images ◽  
Structural Modifications ◽  
New Formulation

The aim of this study was represented by the definition and testing of a new formulation strategy and the functionality of composite materials, while ensuring the optimization of the relevant properties for the dental restoration processes through the use of precise techniques of characterization, the modification and functionality of the components in view of obtaining results that are characterized by an optimum biomechanical and bioactive relation, in full agreement with the particularities of the dental structure that requires restoration. In view of obtaining new resistant composite structures we made a number of 10 samples including extracted teeth with various losses of dental substance and the structural modifications included 3 types of composites, whose structure was improved by the introduction of inorganic fillings based on hydroxyapatite and silver nanoparticles. All these structures were reinforced with two types of fibers, Reforpost fiber glass kit (Angelus) and Fiber post Schulzer Pre-silanized; With regard to the use of composite structures improved by HA addition, we notice a slight lacunary structure on the SEM images due to the properties of HA, an aspect present at much smaller dimensions in the silver � HA mix. The size of the grains associated with their continuous uniformity and adherence for the fibrillar structure stands out at the samples with hydroxyapatite, the first place as uniformity and adherence going to the composite of the nanofiller technology category.

Optimum design of composite structures with ply drop-offs using response surface methodology

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Camila Aparecida Diniz ◽  
Yohan Méndez ◽  
Fabrício Alves de Almeida ◽  
Sebastião Simões da Cunha Jr ◽  
G.F. Gomes
Keyword(s):  
Response Surface Methodology ◽  
Natural Frequency ◽  
Design Variable ◽  
Composite Structures ◽  
Laminate Plate ◽  
Longitudinal Direction ◽  
Stacking Sequence ◽  
Direct Influence ◽  
Optimization Strategy ◽  
Content Type

Purpose Many studies only take into account the ply stacking sequence as the design variable to determine the optimal ply drop-off location; however, it is necessary to optimize other parameters that have a direct influence on the ply drop-off site such as which plies should be dropped and in which longitudinal direction. That way, the purpose of this study is to find the most significant design variables relative to the drop-off location considering the transversal and longitudinal positions, seeking to achieve the optimal combination of ply drop-off locations that provides excellent performance for the laminate plate. Design/methodology/approach This study aims to determine the optimal drop-off location in a laminate plate using the finite element method and an approach statistical with design of experiments (DOE). Findings The optimization strategy using DOE revealed to be satisfactory for analyzing laminate structures with ply drop-offs, demonstrating that not all design factors influence the response variability. The failure criterion response variable revealed a poor fit, with an adjusted coefficient of determination lower than 60%, thus demonstrating that the response did not vary with the ply drop-off location. Already the strain and natural frequency response variables presented high significance. Finally, the optimization strategy revealed that the optimal drop-off location that minimizes the strain and maximizes the natural frequency is the ply drop-off located of the end plate. Originality/value It was also noted that many researchers prefer evolutionary algorithms for optimizing composite structures with ply drop-offs, being scarce to the literature studies involving optimization strategies using response surface methodology. In addition, many studies only take into account the ply stacking sequence as the design variable to determine the optimal ply drop-off location; however, in this study, the authors investigated other important parameters that have direct influence on the ply drop-off site such as which plies should be dropped and in which longitudinal direction.

Multi-objective particle swarm optimisation approach for production-inventory control systems

2018 ◽  
Vol 13 (4) ◽  
pp. 1037-1056 ◽  
Author(s):  
Huthaifa AL-Khazraji ◽  
Colin Cole ◽  
William Guo
Keyword(s):  
Control System ◽  
Control Systems ◽  
Inventory Control ◽  
Dynamic Performance ◽  
Particle Swarm ◽  
Particle Swarm Optimisation ◽  
Inventory Level ◽  
Content Type ◽  
Multi Objective ◽  
Production Inventory

Purpose This paper aims to optimise the dynamic performance of production–inventory control systems in terms of minimisation variance ratio between the order rate and the consumption, and minimisation the integral of absolute error between the actual and the target level of inventory by incorporating the Pareto optimality into particle swarm optimisation (PSO). Design/method/approach The production–inventory control system is modelled and optimised via control theory and simulations. The dynamics of a production–inventory control system are modelled through continuous time differential equations and Laplace transformations. The simulation design is conducted by using the state–space model of the system. The results of multi-objective particle swarm optimisation (MOPSO) are compared with published results obtained from weighted genetic algorithm (WGA) optimisation. Findings The results obtained from the MOPSO optimisation process ensure that the performance is systematically better than the WGA in terms of reducing the order variability (bullwhip effect) and improving the inventory responsiveness (customer service level) under the same operational conditions. Research limitations/implications This research is limited to optimising the dynamics of a single product, single-retailer single-manufacturer process with zero desired inventory level. Originality/value PSO is widely used and popular in many industrial applications. This research shows a unique application of PSO in optimising the dynamic performance of production–inventory control systems.

Optimization design of drive system for industrial robots based on dynamic performance

2017 ◽  
Vol 44 (6) ◽  
pp. 765-775 ◽  
Author(s):  
LianZheng Ge ◽  
Jian Chen ◽  
Ruifeng Li ◽  
Peidong Liang
Keyword(s):  
Optimization Model ◽  
Optimization Problem ◽  
Industrial Robot ◽  
Dynamic Performance ◽  
System Optimization ◽  
Drive System ◽  
Industrial Robots ◽  
Mixed Integer ◽  
Light Weight ◽  
Content Type

Purpose The global performance of industrial robots partly depends on the properties of drive system consisting of motor inertia, gearbox inertia, etc. This paper aims to deal with the problem of optimization of global dynamic performance for robotic drive system selected from available components. Design/methodology/approach Considering the performance specifications of drive system, an optimization model whose objective function is composed of working efficiency and natural frequency of robots is proposed. Meanwhile, constraints including the rated and peak torque of motor, lifetime of gearbox and light-weight were taken into account. Furthermore, the mapping relationship between discrete optimal design variables and component properties of drive system were presented. The optimization problem with mixed integer variables was solved by a mixed integer-laplace crossover power mutation algorithm. Findings The optimization results show that our optimization model and methods are applicable, and the performances are also greatly promoted without sacrificing any constraints of drive system. Besides, the model fits the overall performance well with respect to light-weight ratio, safety, cost reduction and others. Practical implications The proposed drive system optimization method has been used for a 4-DOF palletizing robot, which has been largely manufactured in a factory. Originality/value This paper focuses on how the simulation-based optimization can be used for the purpose of generating trade-offs between cost, performance and lifetime when designing robotic drive system. An applicable optimization model and method are proposed to handle the dynamic performance optimization problem of a drive system for industrial robot.

scholarly journals Receptance-based frequency assignment for assembled structures

2020 ◽  
pp. 107754632094545
Author(s):  
Shike Zhang ◽  
Huajiang Ouyang
Keyword(s):  
Structural Properties ◽  
Natural Frequencies ◽  
Dynamic Performance ◽  
Frequency Assignment ◽  
Structural Components ◽  
Engineering Structures ◽  
Numerical Examples ◽  
Structural Modifications ◽  
Assignment Method

For engineering structures, there is a strong need to assign natural frequencies to achieve desired dynamic performance. This study proposes a receptance-based frequency assignment method for assembled structures. Very often, the substructures involved are not allowed or are difficult to change. This method uses the links between the substructures as targets of structural modifications and determines the structural properties of the links that assign the desired frequencies cast as an optimisation problem. These links could be either simple discrete structural components such as masses and springs or complex continuous structures. Only a few receptances of the substructures are required in this method, which can be measured accurately and easily in practice. Two numerical examples are presented to show the validity of this method and its strength in dealing with complex assembled structures.

scholarly journals Influence of Gradual Damage on the Structural Dynamic Behaviour of Composite Rotors: Experimental Investigations

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2421 ◽  
Author(s):  
Angelos Filippatos ◽  
Maik Gude
Keyword(s):  
Mechanical Properties ◽  
Composite Structures ◽  
Dynamic Behaviour ◽  
Experimental Investigations ◽  
Catastrophic Failure ◽  
Structural Dynamic ◽  
Delamination Growth ◽  
Reinforced Composite ◽  
Out Of Plane ◽  
Effective Mechanical Properties

Fibre-reinforced composite structures subjected to complex loads exhibit gradual damage behaviour with the degradation of the effective mechanical properties and changes in their structural dynamic behaviour. Damage manifests itself as a spatial increase in inter-fibre failure and delamination growth, resulting in local changes in stiffness. These changes affect not only the residual strength but, more importantly, the structural dynamic behaviour. In the case of composite rotors, this can lead to catastrophic failure if an eigenfrequency coincides with the rotational speed. The description and analysis of the gradual damage behaviour of composite rotors, therefore, provide the fundamentals for a better understanding of unpredicted structural phenomena. The gradual damage behaviour of the example composite rotors and the resulting damage-dependent dynamic behaviour were experimentally investigated under propagating damage caused by a combination of out-of-plane and in-plane loads. A novel observation is the finding that a monotonic increase in damage results in a non-monotonic frequency shift of a significant number of eigenfrequencies.

Optimization of the Global Static and Dynamic Performance of a Vehicle Body by Means of Response Surface Models

2012 ◽  
Author(s):  
Pavlina Mihaylova ◽  
Alessandro Pratellesi ◽  
Niccolò Baldanzini ◽  
Marco Pierini
Keyword(s):  
Response Surface ◽  
Dynamic Performance ◽  
The Body ◽  
Vehicle Body ◽  
Fe Model ◽  
Structural Modifications ◽  
Response Surface Models ◽  
First Choice ◽  
Surface Models ◽  
Body In White

Concept FE models of the vehicle structure are often used to optimize it in terms of static and dynamic stiffness, as they are parametric and computationally inexpensive. On the other hand they introduce modeling errors with respect to their detailed FE equivalents due to the simplifications made. Even worse, the link between the concept and the detailed FE model can be sometimes lost after optimization. The aim of this paper is to present and validate an alternative optimization approach that uses the detailed FE model of the vehicle body-in-white instead of its concept representation. Structural modifications of this model were applied in two different ways — by local joint modifications and by using mesh morphing techniques. The first choice was motivated by the strong influence of the structural joints on the global vehicle performance. For this type of modification the plate thicknesses of the most influent car body joints were changed. In the second case the overall car dimensions were modified. The drawback of using detailed FE models of the vehicle body is that they can be times bigger than their concept counterparts and can thus require considerably more time for structural analysis. To make the approach proposed in this work a feasible alternative for optimization in the concept phase response surface models were introduced. With them the global static and dynamic performance of the body-in-white was represented by means of approximating polynomials. Optimization on such mathematical models is fast, so the choice of the optimization algorithm is not limited only among local-search strategies. In the current study Genetic Algorithm was used to increase the chances for finding better design alternatives. Two different optimization problems were defined and solved. Their final solutions were presented and compared in terms of structural modifications and resulting responses. The approach in this paper can be successfully used in the concept phase as it is fast and reliable and at the same time it avoids the problems typical for concept models.

An energy-efficient scalar control taking core losses into account

2018 ◽  
Vol 37 (2) ◽  
pp. 849-867 ◽  
Author(s):  
Gabriel Khoury ◽  
Ragi Ghosn ◽  
Flavia Khatounian ◽  
Maurice Fadel ◽  
Mathias Tientcheu
Keyword(s):  
Energy Efficient ◽  
Mechanical Load ◽  
Dynamic Performance ◽  
Optimization Technique ◽  
Optimization Methods ◽  
Variable Speed ◽  
Variable Speed Drives ◽  
Content Type ◽  
Scalar Control ◽  
Core Losses

PurposeIn the need to optimize the energy efficiency, control structures can have a positive effect by tracking the optimal operating point according to the speed and mechanical load of the motor. The purpose of this paper is to present an energy-efficient scalar control for squirrel-cage induction motors (IMs), taking into consideration the effect of core losses. Design/methodology/approachThe proposed technique is based on the modification of the stator flux reference, to track the best efficiency point. The optimal flux values are computed through an improved model of the IM including core losses, then stored in a look-up table. FindingsSimulations of the proposed scalar control are carried out, and results show the efficiency improvement when the flux is optimized especially at low load cases. Results were validated experimentally on two motors compliant with different efficiency standards. Practical implicationsThe proposed approach can be used in several fields and applications using the scalar-controlled IM with a proper implementation in variable speed drives, as in the cases of pumps, compressors and blowers. Originality/valueThe proposed technique is compared to existing optimization methods in literature, and the results show an improvement in the dynamic performance and in the response delays. The approach is also compared to an optimization technique used in industries like Leroy-Somer for variable speed drives, and efficiency improvements are shown.

Robust mode transition control of four-wheel-drive hybrid electric vehicles based on radial basis function neural network estimation-a simulation study

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ling Li ◽  
Fazhan Tao ◽  
Zhumu Fu
Keyword(s):  
Dynamic Performance ◽  
Transition Process ◽  
Mode Transition ◽  
Robust Controller ◽  
Content Type ◽  
Engine Torque ◽  
Transition Control ◽  
Wheel Drive ◽  
Mode Transition Control ◽  
Four Wheel Drive

Purpose The flexible mode transitions, multiple power sources and system uncertainty lead to challenges for mode transition control of four-wheel-drive hybrid powertrain. Therefore, the purpose of this paper is to improve dynamic performance and fuel economy in mode transition process for four-wheel-drive hybrid electric vehicles (HEVs), overcoming the influence of system uncertainty. Design/methodology/approach First, operation modes and transitions are analyzed and then dynamic models during mode transition process are established. Second, a robust mode transition controller based on radial basis function neural network (RBFNN) is proposed. RBFNN is designed as an uncertainty estimator to approximate lumped model uncertainty due to modeling error. Based on this estimator, a sliding mode controller (SMC) is proposed in clutch slipping phase to achieve clutch speed synchronization, despite disturbance of engine torque error, engine resistant torque and clutch torque. Finally, simulations are carried out on MATLAB/Cruise co-platform. Findings Compared with routine control and SMC, the proposed robust controller can achieve better performance in clutch slipping time, engine torque error, vehicle jerk and slipping work either in nominal system or perturbed system. Originality/value The mode transition control of four-wheel-drive HEVs is investigated, and a robust controller based on RBFNN estimation is proposed. Compared results show that the proposed controller can improve dynamic performance and fuel economy effectively in spite of the existence of uncertainty.

Stress, strain and displacement analysis of geodetic and conventional fuselage structure for future passenger aircraft

2019 ◽  
Vol 91 (6) ◽  
pp. 814-819
Author(s):  
Zdobyslaw Jan Goraj ◽  
Mariusz Kowalski ◽  
Bartlomiej Goliszek
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Weight Reduction ◽  
Composite Structures ◽  
Lattice Structure ◽  
Small Displacement ◽  
Structure Stability ◽  
Outer Diameter ◽  
Content Type ◽  
Element Method

Purpose This paper aims to present the results of calculations that checked how the longerons and frames arrangement affects the stiffness of a conventional structure. The paper focuses only on first stage of research – analysis of small displacement. Main goal was to compare different structures under static loads. These results are also compared with the results obtained for a geodetic structure fuselage model of the same dimensions subjected to the same internal and external loads. Design/methodology/approach The finite element method analysis was carried out for a section of the fuselage with a diameter of 6.3 m and a length equal to 10 m. A conventional and lattice structure – known as geodetic – was used. Findings Finite element analyses of the fuselage model with conventional and geodetic structures showed that with comparable stiffness, the weight of the geodetic fuselage is almost 20 per cent lower than that of the conventional one. Research limitations/implications This analysis is limited to small displacements, as the linear version of finite element method was used. Research and articles planned for the future will focus on nonlinear finite element method (FEM) analysis such as buckling, structure stability and limit cycles. Practical implications The increasing maturity of composite structures manufacturing technology offers great opportunities for aircraft designers. The use of carbon fibers with advanced resin systems and application of the geodetic fuselage concept gives the opportunity to obtain advanced structures with excellent mechanical properties and low weight. Originality/value This paper presents very efficient method of assessing and comparison of the stiffness and weight of geodetic and conventional fuselage structure. Geodetic fuselage design in combination with advanced composite materials yields an additional fuselage weight reduction of approximately 10 per cent. The additional weight reduction is achieved by reducing the number of rivets needed for joining the elements. A fuselage with a geodetic structure compared to the classic fuselage with the same outer diameter has a larger inner diameter, which gives a larger usable space in the cabin. The approach applied in this paper consisting in analyzing of main parameters of geodetic structure (hoop ribs, helical ribs and angle between the helical ribs) on fuselage stiffness and weight is original.

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