Metamodelēšanas pielietojums dinamisku sistēmu analīzē un optimizācijā

Promocijas darbs veltīts metamodelēšanas pielietojumam dinamisku sistēmu analīzei un optimizācijai. Izstrādāta metodika dinamisku sistēmu metamodeļu veidošanai uz skaitlisko un naturālo eksperimentu bāzes un šo metamodeļu pielietošanai daudzkriteriālajā optimizācijā. Metodes būtība ir dinamiskās sistēmas pārejas vai stacionārā procesa vienkāršota modeļa (metamodeļa) izveide, aprakstot to ar nelielu parametru skaitu. Pēc tam ar skaitlisko un naturālo eksperimentu un moderno neparametrisko aproksimācijas metožu palīdzību tiek izveidots matemātiskais modelis, kurš apraksta pārejas procesa parametru atkarību no sistēmas variējamajiem ieejas faktoriem. Šis modelis tālāk ir izmantojams procesu analīzē un daudzkriteriālajā optimizācijā. Konkrētajā gadījumā kā dinamiska sistēma tiek aplūkots betona paraugu formēšanas vibropresēšanas process. Pirmajā analīzes etapā ar atbildes virsmu metodi tiek izveidots vienkāršots vibrokompaktēšanas pārejas procesa modelis, kura ieejas ir trīs mainīgie vibropresēšanas procesa parametri: f0 – presēšanas spēks, fA – spēka amplitūda, ω – vibrēšanas frekvence, bet izejas ir trīs koeficienti, kuri raksturo kompaktēšanās procesu kā laika funkciju. Metamodeļu izveidošanai tiek lietots Latīņu Hiperkuba tipa eksperimentu plāns, variējot mainīgos parametrus, izveidotas vairākas paraugu sērijas izmantojot testēšanas mašīnas Instron 8802 un Zwick. Daļa no paraugiem tika testēta SIA „TMB Elements” laboratorijā. Ir izveidoti vibropresēšanas procesu raksturojošie metamodeļi, pielietojot kriginga un polinomiālās aproksimāciju metodes. Darbā ir noteikti dinamiskās sistēmas daudzkriteriālās optimizācijas mērķfunkcijas un ierobežojumi. Ir veikta paraugu formēšanas vibropresēšanas procesa parametru multikriteriālā optimizācija, pielietojot Pareto robežvirsmu metodi un programmatūru EDAOpt. Skaitliskie eksperimenti tika validēti ar naturālajiem. Tika konstatēta laba sakritība starp naturālajiem un skaitliskiem eksperimentiem

The Effect of Vibropressing Process on the Strength of Concrete

The paper describes the vibropresing process using for building concrete samples and the effect of vibropressing process [1] on the strength of concrete. The material testing machine Zwick was used for experiments with raw concrete vibropressing. The form of samples is cylindrical with diameter 84.5 mm. The vibropressing regime is described by formula f=f0+fAsin(ωt) was realizing changing three parameters - f0 pressing force (10-50kN), fA force amplitude (1-11kN) and frequency(10-50 Hz). The experiments were conducted according to the Mean Square Error Latin hypercube design [2]. The influence of pressing force, force amplitude and frequency on the vibropressing process [3] and on the strength of samples was investigated. The registered force curves were smoothed and approximated with 3 parameter functions. The results of crash test are analyzing using software Design Expert and EDAOpt. The dependency model of the strength of samples on the three parameters was identified and used process optimization

The Investigation of Vibropressing Process Technology

The vibropressing process tehnology is useful for compacting or packing any dispersed or granulometric materials, can be applied in the agriculture. Vibration is widely used in the preparation of concrete and formation of parts from it [1]. The vibropressing technology means a vibrating of a concrete mix in the press form under pressure. The method is high-efficiency, gives the chance to make rigid concrete that provides high durability and frost resistance of products. To achieve a high compaction rate and high strength of the formed product - paving blocks, bricks etc., the vibration must be combined with high pressure. There is an extensive literature on the effects of such features as frequency, amplitude and acceleration, and a lot of literature about rheological models of raw concrete. The results depend on material characteristics such as the difference between its initial density after preparation and its maximum packing fraction, the coefficient of friction between the grains, the angularity of particles etc. [2]. In the present work the vibropressing process was experimentally modelled on the dynamic testing machines Instron and Zwick. The form of concrete samples was cilindrical. The vibropressing regime, described by formula f=f0+fAsin(ωt) was realizing by changing three input parameters - f0 pressing force (10-50kN), fA force amplitude (1-11kN) and frequency(10-50 Hz). The experiments were conducted according to the Mean Square Error Latin hypercube design [3]. The influence of pressing force, force amplitude and frequency on the vibropressing process [4] and on the strength of samples was investigated

Analysis of Products Obtained from Recycled Absorbent Hygiene Products

This paper presents the analysis of product obtained from recycled Absorbent Hygiene Products (AHP). The average baby goes through nearly 7,000 diapers and all of them are sent to the landfill. The most popular technology in the world processes AHPs and reclaims the valuable plastic and fibre. The next technology reviewed in this paper changes used diapers into fuel resources in a safely managed process. It is final outcome is energy pellet with calorific value 20853 kJ/kg, which is a fuel for biomass boiler. The energy from biomass boiler can be supplied to in-house and/or neighbouring facilities. One more technology created to convert AHP into the coal and gas by pyrolysis process. Calorific values for them respectively are 15950-18080 kJ/kg (coal) and 34400 kJ/kg (gas). The energetic balance should be done in the future re-search to understand, what kind of product obtained from AHP is the most effective and useful. The maximal use or reuse of human waste let to decrease the amount of waste on the landfills, and helps to protect the nature

Research of Recycling of Absorbent Hygiene Products (AHPs)

The paper presents different Absorbent Hygiene Products (AHPs) recycling methods. Absorbent Hygiene Products consist of disposable child nappies, adult incontinence products, feminine hygiene and similar products. The paper gives view of two different AHPs waste recycling methods with different recycling products (plastic pellets, pellets). Describe`s technological methods step by step. Shows method`s plusses and minuses. On the basis of two existing recycling methods, experimentally is developed a new AHPs recycling method using pyrolysis method which gives recycling products as gas and pellets. As for the economical field, from experiment with pyrolysis recycling method seems that this method is self-contained. This method is the future of AHPs waste recycling

Experimental Identification and Multiobjective Optimization of the Vibrocompacting Process of Composite Substances

Vibration is the most popular means of compacting material mixtures such as fresh concrete, powder and granulated materials. To achieve a high compaction rate and high strength of formed product - paving blocks, bricks etc., the vibration must be combined with high pressure. There is an extensive literature on the effects of such features as frequency, amplitude and acceleration, and a lot of literature about rheological models of raw concrete. The results depend on material characteristics such as the difference between its initial density after preparation and its maximum packing fraction, the coefficient of friction between the grains, the angularity of particles etc. [1]. So the theoretical results are not capable of giving full and adequate information for the optimization of the vibrocompacting process according to quality of products, costs and other criteria of manufacturing effectiveness. Optimal vibrocompacting parameters usually must be determined experimentally [2]. In the present work a more general methodology of experimental identification of mathematical models of compacting process and consequent multiobjective optimization is introduced. This methodology consists of the following steps: 1. The choice of input variable parameters X for the model building. Some of them are controllable (vibration frequency, pressure, water/cement ratio...), other parameters have an effect on process, but are only monitored, and must be considered as given (dimensions of product to be formed, granulometric parameters of used materials...). 2. Carrying out the natural experiments according to sequential, Mean Square Error-optimal experimental design [3]. We used material testing machines Instron and Zwick with specially constructed mould-plunger devices for raw concrete forming. The measured results are load and displacement (compaction) graphs versus the time. 3. Approximation of load and displacement graphs with minimal number of parameters Y. Exponential functions with 2-3 parameters give sufficiently accurate approximation. 4. Building the mathematical models for the approximation of the dependence of the parameters Y on input factors X. Nonparametric approximation methods like kriging should be used to reduce the number of experimental tries [3]. 5. Analytical or experimental formulation of optimization objectives (compacting rate, manufacturing cost, product cost etc.). Providing of multiobjective Pareto-optimization. 6. Validation of optimization results using additional experiments. This methodology is demonstrated for the choice of optimal vibration frequency, pressure and process duration. The objectives are compacting rate, consumed energy, pressing force. The same methodology can be used for powder and granulated material compacting

Development of Experimental Optimization Methodology for the Pipelines Repairing by Using Advanced Composite Materials

Metamodelling is scientific current in the theoretical and experimental engineering science and mechanics. Metamodelling, or meta-modelling in software engineering and systems engineering among other disciplines, is the analysis, construction and development of the frames, rules, constraints, models and theories applicable and useful for modelling a predefined class of problems. This method allows obtaining information about the structure of the investigated object by analysing solely the registered output measurements of this object (machine, mechanism, technological process), and identifying both the mathematical model of the object and its input parameter values, using both natural experiments and computer experiments with different mathematical modelling software (ANSYS, LSDYNA, ADAMS, etc.). Creation of metamodels for the dependence of the response surface data to the input factors is facilitating to formulate the multiobjective optimization goal functions and constraints, conducting optimization. Verification and validation of results provides the best optimization data

Experimental Identification and Optimization of Concrete Block Vibropressing Process

The material testing machine Instron 8802 was used for experiments with raw concrete vibropressing. The experiments were conducted according to the Mean Square Error Latin hypercube design. The influence of pressing force, force amplitude and frequency on the pressing process was investigated. The registered displacement and force curves were smoothed and approximated with 1- 3 parameter functions. The dependence of these parameters on the pressing force constant component, force oscillation amplitude and frequency was determined using nonparametric kriging approximations. The approximations were validated with additional physical experiments. The estimated relative prediction error was 15%. The built approximated models were used for multiobjective optimization of the vibropressing process. Optimization criteria were: compacting rate, consumed energy, pressing cycle length. Pareto frontier surfaces were constructed and analyzed

Optimization and Metamodeling of Metal Sandwich Panel Structures

The development of new materials and new manufacturing techniques has accelerated during the last several years. Laser welding is one of these technologies and it has facilitated use of steel sandwich panels. The application of such new structures requires fast optimization procedures to obtain optimal design configuration for a given design case. In order to obtain recommendations concerning the best configuration, different metamodeling methods where used for approximation, optimization and analysis of different core sandwich panels. Application of metamodeling methods for optimization included several steps: 1) design of experiments, 2) numerical experiments based on FE calculations, 3) high precision approximations of experimental data using polynomials, locally weighted polynomials and kriging, 4) multi-objective optimization using three criterions. The results of different metamodeling methods and parameter fitting techniques where compared, with conclusion that kriging gives the best overall approximation results. The metamodel accuracy was increased by introduction of additional parameter inverse proportional to the second moment of area of panel cross section

Experimental Identification and Optimization of Concrete Block Vibropressing Process

The material testing machine Instron 8802 was used for experiments with raw concrete vibropressing. The experiments were conducted according to the Mean Square Error Latin hypercube design. The influence of pressing force, force amplitude and frequency on the pressing process was investigated. The registered displacement and force curves were smoothed and approximated with 1- 3 parameter functions. The dependence of these parameters on the pressing force constant component, force oscillation amplitude and frequency was determined using nonparametric kriging approximations. The approximations were validated with additional physical experiments. The estimated relative prediction error was 15%. The built approximated models were used for multiobjective optimization of the vibropressing process. Optimization criteria were: compacting rate, consumed energy, pressing cycle length. Pareto frontier surfaces were constructed and analyze