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Engineering Mechanics 2020最新文献

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DISTRIBUTION-BASED GLOBAL SENSITIVITY ANALYSIS BY POLYNOMIAL CHAOS EXPANSION 基于分布的多项式混沌展开全局灵敏度分析
Engineering Mechanics 2020 Pub Date : 1900-01-01 DOI: 10.21495/5896-3-380
L. Novák, D. Novak
{"title":"DISTRIBUTION-BASED GLOBAL SENSITIVITY ANALYSIS BY POLYNOMIAL CHAOS EXPANSION","authors":"L. Novák, D. Novak","doi":"10.21495/5896-3-380","DOIUrl":"https://doi.org/10.21495/5896-3-380","url":null,"abstract":": The paper is focused on study of distribution based global sensitivity indices derived directly from polynomial chaos expansion. The significant advantage is that, once the approximation in form of polynomial chaos expansion is available it is possible to obtain first statistical moments, Sobol indices and also distribution function with proposed moment-independent sensitivity indices without additional computational demands. The key idea is to use only specific part of approximation and compare obtained conditional probability cumulative distribution function to original distribution assuming all variables free to vary. The difference between distributions is measured by Cramer-von Misses distance herein. However, it is generally possible to employ any type of measure. The method is validated by analytical example with known solution. Proposed approach is highly efficient and thus it can be recommended for practical applications, when it is not possible to perform sensitivity analysis by standard Monte Carlo approach.","PeriodicalId":383836,"journal":{"name":"Engineering Mechanics 2020","volume":"23 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114457714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 13
STRUCTURAL OPTIMIZATION OF AEROFOILS FOR MANY CRITERIA 多准则下的翼型结构优化
Engineering Mechanics 2020 Pub Date : 1900-01-01 DOI: 10.21495/5896-3-448
T. Schlieter, A. Długosz
{"title":"STRUCTURAL OPTIMIZATION OF AEROFOILS FOR MANY CRITERIA","authors":"T. Schlieter, A. Długosz","doi":"10.21495/5896-3-448","DOIUrl":"https://doi.org/10.21495/5896-3-448","url":null,"abstract":": In this paper a problem of structural optimization of an aerofoil is examined. Authors’ implementation of a multiobjective optimization algorithm based on differential evolution and elements of game theory is used as an optimization tool. Real requirements asked of aerofoil systems, described by mathematical functions are used as optimization objectives. Values of these functionals are determined numerically multiple times during the course of optimization. On the basis of a wing of unmanned aerial vehicle (UAV), a parametric numerical model is built. The inner geometry of the wing is described by 24 design variables and is subject to the optimization, while the outer geometry doesn’t change.","PeriodicalId":383836,"journal":{"name":"Engineering Mechanics 2020","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123601167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
THREE-DIMENSIONAL NUMERICAL ANALYSIS OF CZECH VOWEL PRODUCTION 捷克语元音生成的三维数值分析
Engineering Mechanics 2020 Pub Date : 1900-01-01 DOI: 10.21495/5896-3-182
P. Hájek, P. Svancara, J. Horáček, J. Švec
{"title":"THREE-DIMENSIONAL NUMERICAL ANALYSIS OF CZECH VOWEL PRODUCTION","authors":"P. Hájek, P. Svancara, J. Horáček, J. Švec","doi":"10.21495/5896-3-182","DOIUrl":"https://doi.org/10.21495/5896-3-182","url":null,"abstract":": Spatial air pressures generated in human vocal tract by vibrating vocal folds present sound sources of vowel production. This paper simulates phonation phenomena by using fluid-structure-acoustic scheme in a three-dimensional (3D) finite element model of a Czech vowel [o:]. The computational model was composed of four-layered M5-shaped vocal folds together with an idealized trachea and vocal tract. Spatial fluid flow in the trachea and in the vocal tract was obtained by unsteady viscous compressible Navier-Stokes equations. The oscillating vocal folds were modelled by a momentum equation. Large deformations were allowed. Transient analysis was performed based on separate structure and fluid solvers, which were exchanging loads acting on the vocal folds boundaries in each time iteration. The deformation of the fluid mesh during the vocal fold oscillation was realized by the arbitrary Lagrangian-Eulerian approach and by interpolation of fluid results on the deformed fluid mesh. Preliminary results show vibration characteristics of the vocal folds, which correspond to those obtained from human phonation at higher pitch. The vocal folds were self-oscillating at a reasonable frequency of 180 Hz. The vocal tract eigenfrequencies were in the ranges of the formant frequencies of Czech vowel [o:] measured on humans; during self-oscillations the formants shifted to lower frequencies.","PeriodicalId":383836,"journal":{"name":"Engineering Mechanics 2020","volume":"05 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129568050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
STRUCTURAL MODAL MODIFICATION OF NON-PROPORTIONALLY DAMPED SYSTEM 非比例阻尼系统的结构模态修正
Engineering Mechanics 2020 Pub Date : 1900-01-01 DOI: 10.21495/5896-3-366
M. Musil, O. Chlebo, J. Úradníček, F. Havelka, M. Milata
{"title":"STRUCTURAL MODAL MODIFICATION OF NON-PROPORTIONALLY DAMPED SYSTEM","authors":"M. Musil, O. Chlebo, J. Úradníček, F. Havelka, M. Milata","doi":"10.21495/5896-3-366","DOIUrl":"https://doi.org/10.21495/5896-3-366","url":null,"abstract":": Undesirable levels of vibration are an especially common occurrence in modern engineering. Being able to effectively isolate and solve the problem areas of a structure would prove to be a valuable tool in correcting these levels of vibration. This work presents a method for modal synthesis that enables the structural properties to be purposefully changed and that can be applied to systems with non-proportional damping. In order to present the methodology in detail, the case where additional elements are made of aluminium foam are presented. These have very unique properties and broad applications. This methodology is demonstrated, for better understanding, on an example of a beam with added aluminium foam elements. A beam with aluminium foam was chosen since its connection with the base beam changes the inertial as well as stiffness and damping properties of the resulting system.","PeriodicalId":383836,"journal":{"name":"Engineering Mechanics 2020","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127489566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
AIR SPRING CONTROLLED BY REINFORCEMENT LEARNING ALGORITHM 采用强化学习算法控制空气弹簧
Engineering Mechanics 2020 Pub Date : 1900-01-01 DOI: 10.21495/5896-3-428
J. Rágulík, M. Sivčák
{"title":"AIR SPRING CONTROLLED BY REINFORCEMENT LEARNING ALGORITHM","authors":"J. Rágulík, M. Sivčák","doi":"10.21495/5896-3-428","DOIUrl":"https://doi.org/10.21495/5896-3-428","url":null,"abstract":": The paper deals with the replacement of the analogy PID stroke controller of a bellows pneumatic spring, by machine learning algorithms, specifically deep reinforcement learning. The Deep Deterministic Policy Gradient (DDPG) algorithm used consists of an environment, in this case a pneumatic spring, and an agent which, based on observations of environment, performs actions that lead to the cumulative reward it seeks to maximize. DDPG falls into the category of actor-critic algorithms. It combines the benefits of Q-learning and optimization of a deterministic strategy. Q-learning is represented here in the form of critic, while optimization of strategy is represented in the form of an actor that directly maps the state of the environment to actions. Both the critic and the actor are represented in deep reinforcement learning by deep neural networks. Both of these networks have a target variant of themselves. These target networks are designed to increase the stability and speed of the learning process. The DDPG algorithm also uses a replay buffer, from which the data from which the agent learns is taken in batches.","PeriodicalId":383836,"journal":{"name":"Engineering Mechanics 2020","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126957756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
STABILITY OF A BAR INFLUENCED BY SMALL AND LARGE IMPERFECTIONS 受大小缺陷影响的杆的稳定性
Engineering Mechanics 2020 Pub Date : 1900-01-01 DOI: 10.21495/5896-3-374
J. Náprstek, C. Fischer
{"title":"STABILITY OF A BAR INFLUENCED BY SMALL AND LARGE IMPERFECTIONS","authors":"J. Náprstek, C. Fischer","doi":"10.21495/5896-3-374","DOIUrl":"https://doi.org/10.21495/5896-3-374","url":null,"abstract":"Abstract: The geometrical and physical imperfections of systems can drastically reduce their critical loading. These imperfections are usually of stochastic character and, therefore, they act as random parametric perturbations of coefficients of corresponding differential equations. In this paper, the imperfections are introduced as multidimensional statistics on the set of a large number of realizations of the same system. As far as the amount of information is small or the imperfections themselves cannot be considered small, the convex analysis is preferable. The paper compares results obtained by both stochastic and convex analyses for hyperprism and demonstrates when each of them is more convenient to be used. Besides of the hyper-prism, the possibilities and properties of other modifications of convex method are considered, especially those based on the definition of imperfection zone marked as a centric hyper-ellipsoid or as an eccentric hyper-ellipsoid. The analytical background was brought up to the level when only a few configurations of imperfections are sufficient to be evaluated numerically. These configurations are obtained by means of the convex analysis as points of extreme critical loading using the Lagrange method of constrained extremes.","PeriodicalId":383836,"journal":{"name":"Engineering Mechanics 2020","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126891836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
RESULTS ANALYSIS OF TI6AL4V TITANIUM ALLOY TESTS IN STATIC LOAD CONDITIONS ti6al4v钛合金静载试验结果分析
Engineering Mechanics 2020 Pub Date : 1900-01-01 DOI: 10.21495/5896-3-266
K. Karolewska, B. Ligaj
{"title":"RESULTS ANALYSIS OF TI6AL4V TITANIUM ALLOY TESTS IN STATIC LOAD CONDITIONS","authors":"K. Karolewska, B. Ligaj","doi":"10.21495/5896-3-266","DOIUrl":"https://doi.org/10.21495/5896-3-266","url":null,"abstract":": The development of additive manufacturing increased the spectrum of printers from those intended for plastics to those that are designed for metal. Printing in metal allows to create elements of any shape and geometry, which would be difficult or even impossible to perform using conventional manufacturing methods. The aim of the work is to present the test results under static loading conditions of Ti6Al4V alloy produced by 3D printing. The test results obtained under static load conditions of Ti6Al4V material produced by the DMLS additive technology and drawn bar allow to conclude that: yield point S y0.2 for material made using the DMLS technology is higher than the value for the material delivered in the form of a drawn bar by 11.1 %, material tensile strength S u for material made using DMLS technology is higher than the value for material delivered in the form of a drawn rod by 11.5 %.","PeriodicalId":383836,"journal":{"name":"Engineering Mechanics 2020","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124955195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
GLOBAL TOPOLOGY STIFFNESS OPTIMIZATION OF FRAME STRUCTURES BY MOMENT-SUM-OF-SQUARES HIERARCHY 基于矩平方和层次的框架结构整体拓扑刚度优化
Engineering Mechanics 2020 Pub Date : 1900-01-01 DOI: 10.21495/5896-3-492
M. Tyburec, J. Zeman, M. Kružík, D. Henrion
{"title":"GLOBAL TOPOLOGY STIFFNESS OPTIMIZATION OF FRAME STRUCTURES BY MOMENT-SUM-OF-SQUARES HIERARCHY","authors":"M. Tyburec, J. Zeman, M. Kružík, D. Henrion","doi":"10.21495/5896-3-492","DOIUrl":"https://doi.org/10.21495/5896-3-492","url":null,"abstract":": This contribution develops an efficient formulation for the topology optimization of frame structures with fixed-aspect-ratio cross-sections, solvable to global optimality by the moment-sum-of-squares hierarchy. While the hierarchy generates a sequence of non-decreasing lower-bounds, we develop a sequence of feasible upper-bounds, allowing to assess the optimized design quality in each relaxation. Finally, these bounds provide a means of establishing a new sufficiency condition of global ε-optimality.","PeriodicalId":383836,"journal":{"name":"Engineering Mechanics 2020","volume":"222 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121564420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
FEM SIMULATION OF HEADLESS SCREW 无头螺杆有限元模拟
Engineering Mechanics 2020 Pub Date : 1900-01-01 DOI: 10.21495/5896-3-062
V. Bajtek, K. Frydrýšek, F. Sejda, J. Demel, L. Pleva, P. Bernard, J. Hlinka
{"title":"FEM SIMULATION OF HEADLESS SCREW","authors":"V. Bajtek, K. Frydrýšek, F. Sejda, J. Demel, L. Pleva, P. Bernard, J. Hlinka","doi":"10.21495/5896-3-062","DOIUrl":"https://doi.org/10.21495/5896-3-062","url":null,"abstract":": There are many ways for osteosynthetical treatment of broken bones via fixation. One of them is internal fixation by headless screw, which causes desired compression of bone fragments. In cooperation with medics and industry, FEM simulation (i.e. stress, deformation) was done for prototype of headless screw for 5th metatarsus. Simulations were based on experiment and are followed by other simulation methods too. The aim of this research is to describe basis of issue, define mechanical dependences in headless screws and assessment of headless screws. According to the results, the headless screws can be applied in orthopaedics treatment of fractures.","PeriodicalId":383836,"journal":{"name":"Engineering Mechanics 2020","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116500063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
MODEL OF THE PROCESS OF OPERATING RAIL TRANSPORT MEANS 轨道交通工具运营过程模型
Engineering Mechanics 2020 Pub Date : 1900-01-01 DOI: 10.21495/5896-3-370
Ł. Muślewski, E. Kulis, B. Landowski
{"title":"MODEL OF THE PROCESS OF OPERATING RAIL TRANSPORT MEANS","authors":"Ł. Muślewski, E. Kulis, B. Landowski","doi":"10.21495/5896-3-370","DOIUrl":"https://doi.org/10.21495/5896-3-370","url":null,"abstract":": The process of using public transport trams is characterized by a period of changing phases of use. For units that carry out a transport task, it is important to have tools (of varying complexity in complexity) to analyze and forecast the state of the system, and to facilitate decisions related to process control. It was assumed that in the set of technical objects operated in the test object, disjoint subsets of homogeneous objects can be distinguished from the point of view of the test. The following considerations include a subset of such objects. The results of completed model tests confirmed the expected model responses to changes in the value of its parameters. This proves the correctness of the calculations made and the model's usefulness for initial calculations, the forecasted state of the analyzed system after changing the scope of impacts.","PeriodicalId":383836,"journal":{"name":"Engineering Mechanics 2020","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115135682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 7
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