Metamodels in Optimisation of Plywood Sandwich Panels

In this paper, the strength and the weight effectiveness for the plywood I-core sandwich structure is elaborated. For the plywood sandwich concept the plywood sheets are used at the outer surfaces to maximize rigidity while introducing in between adhesively bonded plywood stiffeners to keep the whole sandwich structure together. The structural stiffness capacity and weight efficiency are elaborated for the pure plywood structure and the I-core sandwich panel with the corresponding height and width dimensions. A metamodelling procedure is applied by approximating the finite element stiffness response values with parametrical functions employing the Adaptive Basis Function Construction approach. The resulting design procedure provides an effective optimal design tool that enables to estimate the stiffness and the weight optimum solutions

Bending Properties of Plywood I-core Sandwich Panels

Lightweight structures as sandwich panels are one of the innovation products to drive the future of the wood/plywood industry for the near future. Material consumption, thus environmental impact, is the driving factor to replace commonly used plywood panels with the plywood sandwich structures. The aim of this paper is to elaborate the design methodology for different core type plywood sandwich panels under the flexural loading. The methodology is based on sampling of the numerical experiments by the finite element code ANSYS and approximation of the response values of the four point bending tests. This methodology is a collection of mathematical and statistical techniques that are useful for the modelling and analysis of problems in which structural responses are influenced by several variables and the objective is to optimize these responses. The methodology is often referred to as metamodelling as they provide a model of a model, replacing the expensive simulation analyses during the optimisation process. Moreover, validations of metamodelling procedure for design of I-core sandwich panels with physical tests have been evaluated. The sandwich panels used in physical experiments were made of plywood outer plate and I-core filling strips and the bending properties have been tested according to EN 789. The structural flexural stiffness capacity and weight efficiency have been elaborated for the I-core sandwich panels by the metamodelling procedure. The design guidelines have been elaborated and validated with the physical experiments

Metamodes in Design of GFRP Composite Stiffened Deck Structure

This paper deals with the comparison of parametric and non-parametric metamodels used in design procedure of pultruded glass fibre reinforced plastic (GFRP) deck panels. Stiffened deck structure loaded under the three-point bending and uniform distributed load has been examined. A set of five hundred sample points has been evaluated by means of finite element analysis and stiffness and strength responses extracted for building of metamodels. Moreover, set of complimentary physical experiments has been carried out in order to verify the numerical model. Both advantages and disadvantages of parametric and non-parametric metamodels have been drawn for a specific engineering application

Metamodels for Optimisation of Post-Buckling Responses in Full-Scale Composite Structures

Extensive application of advanced composite materials such as Carbon Fibre Reinforced Plastics (CFRP) emerges in design of aerospace structural components. Outstanding weight-related stiffness and strength properties in combination with structural topology solutions may lead to exploitation of full-load bearing potential of composite structures as utilization of the post-buckling region. In order to fully exploit the load-carrying capacity of such structures an accurate and reliable simulation is indispensable. That, however, requires fast tools which are capable of simulating the structural behaviour beyond skin buckling bifurcation points deep into the post-buckling phenomena up to the collapse of structure. In this paper a metamodeling methodology is proposed for post-buckling simulation of cylindrical-stiffened fuselage structures. Proposed methodology for elaboration of the fast simulation procedure for axially loaded stiffened cylinder structures is based on utilization of space-filling design of experiments and parametric and non-parametric approximations. For determination of the most suitable metamodeling technique different methods are compared – second-order global polynomials, second-order Locally-Weighted Polynomials, adaptively constructed sparse polynomials, Radial Basis Functions, Kriging, Multivariate Adaptive Regression Splines, and Support Vector Regression. Continuous design variables (the structural geometrical dimensions) are used together with a discrete variable (number of stiffeners), thus allowing to scale the full-scale structure towards the stiffened panel designs. The proposed and validated simulation procedure is an efficient optimum design tool in elaboration of the trade of design and in assessment of parametrical sensitivity analysis. It enables elaboration of Pareto-optimal fronts which can be used in the optimum design guidelines to realise the full potential of the stiffened composite structures subjected to uniform axial compression

Metamodels in Design of GFRP Composite Stiffened Deck Structure

This paper deals with the comparison of parametric and non-parametric metamodels used in design procedure of pultruded glass fibre reinforced plastic (GFRP) deck panels. Stiffened deck structure loaded under the three-point bending and uniform distributed load has been examined. A set of five hundred sample points has been evaluated by means of finite element analysis and stiffness and strength responses extracted for building of metamodels. Moreover, set of complimentary physical experiments has been carried out in order to verify the numerical model. Both advantages and disadvantages of parametric and non-parametric metamodels have been drawn for a specific engineering application

Polynomials in Metamodeling of Glass Fibre Bar Stability

Metamodelēšanā tipiski tiek izmantots zemas pakāpes polinoms – parasti otrās pakāpes polinoms. Tomēr tas nespēj modelēt augstas nelinearitātes uzvedības. Var tikt izmantoti augstākas kārtas polinomi, taču tas var izraisīt aproksimanta nestabilitāti. Kā šīs problēmas pretlīdzekli var izmantot apakškopu izvēles metodes. Taču tajās tiek pieņemts, ka izvēlētā fiksētā pilnā iepriekš izvēlēto bāzes funkciju kopa satur apakškopu, kas ir pilnīgi pietiekoša sakarību pietiekoši labai aprakstīšanai. Cita pieeja ir ļaut modelēšanas metodei pašai konstruēt tādas bāzes funkcijas, kas ir nepieciešamas adekvātas paredzēšanas spējas regresijas modeļa izveidošanai. To ir iespējams veikt izmantojot tā saucamo bāzes funkciju konstruēšanas pieeju (Basis Function Construction, BFC). Izmantojot BFC, lietotājam nav jāizvēlas modeļa maksimālā pakāpe (vai jādefinē bāzes funkciju kopa). BFC automātiski konstruē nepieciešamās bāzes funkcijas, pielietojot heiristisku pārmeklēšanu, efektīvi atrodot kompromisu starp modeļa vienkāršību un paredzēšanas spēju. Rakstā praktiskā stiklšķiedras stieņa stabilitātes metamodelēšanas problēmā tiek salīdzinātas četras dažādas polinomu regresijas modelēšanas metodes: vienkāršā p-tās kārtas polinomu regresija, uz priekšu vērsta izvēle ar statistisko mēru F, uz priekšu vērstā izvēle ar AICC, kā arī BFC pieejas instance. Rezultāti uzrāda BFC pieejas pārākumu

Metamodels for Optimum Design of Laser Welded Sandwich Structures

All-metal sandwich panels, made by a process of laser welding faceplates to core-stiffeners, show advanced cost/weight properties compared with the conventional structural applications of stiffened plates. However optimal design of these advanced structures requires a fast simulation procedure that should have the same level of reliability compared to finite element calculations and natural tests, while being more time effective and less complex. It was shown that different polynomial functions together with design of computer experiments can contribute to such an aim by providing simple however reliable metamodels. The validation procedure indicated an average of 10% relative root mean square error prediction accuracy, and due to this precision the procedure is capable to be used for further (cost/weight) design optimisation together with structural sizing studies and parametric sensitivity analysis

Effectiveness of E-Teaching Implementation and Prospects of Its Advancements for Distributed Groups of Learners

Process of teaching is considered as interaction of complicated intellectual systems. Properties of classical classroom teaching and computer-based learning (eLearning) are compared in respect of interrelated systems involved to teaching/learning process. It is shown that on the base of adoptive character of classical classroom teaching lies “slow” and “quick” feedback between teacher from one side and groups of learners and individual learners from other side. These feedbacks are not inherent to eLearning and eTeaching. Viewpoints of paper’s authors regarding problems of eLearning/eTeaching and possible ways of these problems eliminating are presented. Experience of paper’s authors in application of eTeaching directed to different types of distributed learners groups, namely, young people with special needs, teachers of Informatics from rural secondary schools and representatives of rural municipal offices, is described. It is shown that particularly teachers of Informatics are the most appropriate target group for approbation and popularization of new eLearning/eTeaching methods and approaches. Summarizing paper authors’ experience in conducting of eStudies with different target groups of learners a set of opened issues is formulated. Answers to raised questions should throw light upon mentioned problems and their reasons, give approaches to problems eliminating and show the way of eLearning/eTeaching advancements

Metamodels for the Optimum Design of Corrugate Load-Bearing Profile Plates

Nesošu gofrētu plānsienu profilu plātnes tiek plaši izmantotas būvniecība, it sevišķi, vieglo pārsegumu konstrukciju projektēšanā. Pastāvošā aprēķina metodika neievērtē šīs nesošās profila plātnes kopējās konstrukcijas stinguma aplēsēs. Šobrīd aprēķini ar galīgiem elementiem ir kļuvuši par plaši izplatītu konstrukciju aprēķina praksi. Tomēr šādus plaša mēroga modeļus nav racionāli sadalīt smalkā galīgo elementu tīklā, kas precīzi spētu aprakstīt gofrētās plātnes ģeometriju. Lai atrisinātu šo problēmu tiek piedāvāts aizvietot gofrēta profila plātni ar ekvivalentu ortotropa materiāla plātni. Darba mērķis ir atrast savstarpējas savietojamības iespējas gofrēta profila plātnes un ortotropa materiāla plātnes modeļiem