Rakenteiden Mekaniikka 2018-12-13T19:03:11+02:00 Jarkko Niiranen Open Journal Systems <p>Jo vuodesta 1968 Rakenteiden Mekaniikka -lehden aiheina ovat olleet kiinteiden ja virtaavien aineiden teoreettinen, laskennallinen ja kokeellinen mekaniikka sekä näihin liittyvä matematiikka ja sovellukset. Esimerkkeinä voidaan mainita rakenteiden staattinen ja dynaaminen lujuusanalyysi, monikappaledynamiikka, virtausmekaniikka, rakenteen ja virtauksen vuorovaikutus, rakenteiden ja koneiden suunnittelu ja mitoitus, rakenteiden optimointi, rakenteiden toimivuus ääritilanteissa, älykkäät koneet ja rakenteet, värähtelymekaniikka, kontaktimekaniikka, roottoridynamiikka, murtumismekaniikka ja väsyminen, termomekaniikka, maa- ja kallioperän mekaniikka, rakenteiden materiaalitekniikka, uudet materiaalit, dynaamisten systeemien optimaalinen säätö, elementtimenetelmät ja -analyysi, biomekaniikka, mikromekaniikka, mekaniikan teolliset ja lääketieteelliset sovellutukset sekä mekaniikan ja lujuusopin opetus. Lehti julkaisee lisäksi lyhyitä kommentteja sekä kirjallisuuskatsauksia.</p> History of structural analysis & dynamics of Wärtsilä medium speed engines 2018-12-13T19:03:11+02:00 Tero Frondelius Hannu Tienhaara Mauri Haataja <p>This paper opens up the history of structural analysis and dynamics simulations of&nbsp;Wärtsilä engines. It cites already published articles and theses with some backgrounds information.&nbsp;It also discusses some of the backgrounds of the in-house tool development. Additionally,&nbsp;this paper presents the development of the computers and investment of the simulation capacity&nbsp;in order to understand how it has been the enabler of ever more complicated models. It lists the&nbsp;work done during fifty decades. The authors sincerely attempt to make this article as reader-friendly&nbsp;as possible, even though there are over 220 references, which of course demonstrates&nbsp;how dedicated Wärtsilä has been in supporting numerical simulations research in the past five<br>decades.</p> 2018-12-08T23:05:35+02:00 ##submission.copyrightStatement## Benchmarking of two flexible multibody dynamic simulation software in engine simulations 2018-12-13T19:02:57+02:00 Terho Tuohineva Ilkka Väisänen Antti Mäntylä Teemu Kuivaniemi Mauri Haataja Tero Frondelius <p>In this paper, two different commercial multibody dynamic (MBD) simulation software cases are studied. Due to the restrictions determined in the conditions of contract, the names of the software are not revealed, instead being called Software S and Software E. The central purpose of this research was to investigate the abilities of Software S in the simulation of a large engine, as a part of the strength analysis process. The abilities were studied by comparing the program with another, here called Software E, which is designed primarily for engine simulations. The capabilities of Software E have been proven after years of usage at Wärtsilä, resulting in its essential role in the strength analysis process today. The aim was to find the shortcomings and restrictions of Software S but also advantages it could bring to the strength analysis process for Wärtsilä. Similar simulation models were also built using both programs during this research. A 16-cylinder V-engine was selected as the subject because of its size in order to obtain further information about the behavior of the program when working with extensive model files. The components of the engine were flexible and were reduced FE models, also called super elements. The forces and contact situations that occur inside the engine were modeled using elements provided by the MBD programs. Different levels of detail of the modeling elements were used to obtain information about the flexibility of the program. The results obtained from time integrations were compared to ensure the similarity of both modeling elements used. Also, this paper reports the calculation times. In addition, a small-scale study was performed for Software S to clarify the effect of the modes used in time integrations towards results accuracy and calculation times. Simulation models were built successfully in both programs, and the results obtained correlated with each other on an adequate level. Significant differences appeared in the features and usability of the programs in general. The GUI of Software S is advanced and user-friendly, whereas Software E is not focused on these features. On the other hand, the modeling element library of Software E covers all of the required features related to large engine simulations, some of which Software S is lacking. This work can be used in assistance when considering buying new software for a company as well as when investigating new development areas that could be improved with new software.</p> 2018-12-08T23:07:22+02:00 ##submission.copyrightStatement## Buckling length of a frame member 2018-12-13T19:02:43+02:00 Teemu Tiainen Markku Heinisuo <p>In steel frame design, the definition of buckling lengths of members is a basic task. Computers can be used to calculate the eigenmodes and corresponding eigenvalues for the frames and using these the buckling lengths of the members can be defined using Euler's equation. However, it is not always easy to say, which eigenmode should be used for the definition of the buckling length of a specific member. Conservatively, the lowest positive eigenvalue can be used for all members. In this paper, methods to define the buckling length of a specific member is presented. For this assessment, two ideas are considered. The first one uses geometric stiffness matrix locally and the other one uses strain energy measures to identify members taking part in a buckling mode. The behaviour of the methods is shown in several numerical examples. Both methods can be implemented into automated frame design, removing one big gap in the integrated design. This is essential when optimization of frames is considered.</p> 2018-12-08T23:24:06+02:00 ##submission.copyrightStatement##