Rakenteiden Mekaniikka 2019-09-18T09:48:28+03:00 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> On continuum damage mechanics 2019-09-03T19:25:50+03:00 Kari Juhani Santaoja <p>A material containing spherical microvoids with a Hookean matrix response was shown to take the appearance usually applied in continuum damage mechanics. However, the commonly used variable damage D was replaced with the void volume fraction f , which has a clear physical meaning, and the elastic strain tensor \Bold {ε}^e with the damage-elastic strain tensor \Bold {ε}^{de}. The postulate of strain equivalence with the effective stress concept was reformulated and applied to a case where the response of the matrix obeys Hooke’s law. In contrast to many other studies, in the derived relation between the effective stress tensor \Bold {\Tilde{σ}} and the stress tensor \Bold {σ}, the tensor \Bold {\Tilde{σ}} is symmetric. A uniaxial bar model was introduce for clarifying the derived results. Other candidates for damage were demonstrated by studying the effect of carbide coarsening on creep rate.</p> 2019-08-31T12:43:11+03:00 Copyright (c) 2019 Kari Juhani Santaoja Introduction to JuliaFEM, an open source FEM solver 2019-09-18T09:48:28+03:00 Jukka Aho Antti-Jussi Vuotikka Tero Frondelius <div>This article briefly describes a new programming language Julia and a new innovative Finite Element Method (FEM) solver JuliaFEM. We selected an easy to understand example of a linear elasticity problem as a method for this introduction. We go through the example step by step and provide a detailed explanation of the di fferent phases of the solution steps. The main result presented here demonstrates the scripting possibilities of JuliaFEM, both pre- and post-processing.</div> 2019-09-12T11:02:55+03:00 Copyright (c) 2019 Jukka Aho, Antti-Jussi Vuotikka, Tero Frondelius JuliaFEM beam element implementation 2019-09-13T09:55:56+03:00 Ville Eino Matias Jämsä Jukka Aho Teemu Kuivaniemi Niclas Liljenfeldt Tero Frondelius <div>This article describes implementations of beam elements to JuliaFEM. The theory is briefly introduced, and the usage of beam elements is introduced with a usage example that involves a natural frequency calculation of a formula race car frame. The calculation results were compared to results from a commercial program, and their consistency is excellent.</div> 2019-09-12T00:00:00+03:00 Copyright (c) 2019 Ville Eino Matias Jämsä, Jukka Aho, Teemu Kuivaniemi, Niclas Liljenfeldt, Tero Frondelius Pipe route optimization to avoid undesired vibration by using JuliaFEM 2019-09-13T09:54:55+03:00 Marja Rapo Joona Vaara Teemu Kuivaniemi Niclas Liljenfeldt Antti Vuohijoki Tero Frondelius Jukka Aho <p>An optimization routine was applied to high pressure fuel pipes to avoid resonance in a heavily vibrating environment. The optimization process and also the natural frequency calculations in every iteration were completely performed with the high-level programming language Julia; the optimization process was performed with the JuMP optimization environment, and the frequencies where calculated with JuliaFEM finite element method solver platform. The benefit of this kind of embedded implementation is a quick response which yields a pleasant development environment to focus on the essential—the choice of the optimization strategy.</p> 2019-09-12T15:09:29+03:00 Copyright (c) 2019 Marja Rapo, Joona Vaara, Teemu Kuivaniemi, Niclas Liljenfeldt, Antti Vuohijoki, Tero Frondelius, Jukka Aho A modified four-node rectangular element 2019-09-13T09:54:26+03:00 Jouni Freund Eero-Matti Salonen <p>The sensitized principle of virtual work is applied to modify the stiffness matrix of the ordinary four-node rectangular element by sensitizing terms. The sensitizing parameter values are determined by the single-element strain energy test. The reference solutions used are of bending mode types and their application removes the so-called parasitic shear behavior. A stiffness matrix of good quality is obtained corresponding exactly to an earlier formulation using incompatible modes.</p> 2019-09-12T17:44:58+03:00 Copyright (c) 2019 Jouni Freund, Eero-Matti Salonen