Jakub Kõo

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/7087

Sirvi

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Analysis of thermoelastic stresses in layered plates
(Tallinn University of Technology, 2008) Kõo, Jakub; Valgur, Jaak
This paper deals with thermoelastic effects in deformation of plates with arbitrarily changing elastic parameters and temperature through thickness. Using the semi-inverse method, a simple analytical solution is obtained for the thermoelastic problem of a nonhomogeneous plate with an arbitrary contour. Plates with free, sliding and fixed edges are considered. The results are applied to the layered plate. As an example of application, thermoelastic stresses and deformations are determined for a copper plate with a steel coating. The edge effects for this plate are examined by the finite element method.
Determination of residual stresses in coated plates using layer growing/removing methods: 100th anniversary of Stoney’s equations
(Tallinn University of Technology, 2010) Kõo, Jakub; Valgur, Jaak
In connection with the 100th anniversary of Stoney’s equations, some historical remarks are made with respect to the development of these equations. In the capacity of an example of the extension of Stoney’s equations, a unique algorithm of the layer growing/removing methods for determination of residual stresses in isotropic inhomogeneous coated plates is presented. Using a computer program based on this algorithm, residual stresses are computed in a detonation gun sprayed WC-Co coating.
Determination of Residual Stresses in Inhomogeneous Plates With Layer Growing/Removing Techniques
([Warsaw University of Technology], 1998) Kõo, Jakub; Lille, Harri; Valgur, Jaak; Estonian Agricultural University
A generalized algorithm of the layer growing/removing methods is presented for computing residual stresses in a free rectangular isotropic inhomogeneous plate whose elastic parameters depend on its thickness coordinate. The algorithm allows calculation of residual stresses from initial stresses measured on the moving surface using X-ray diffraction. The suggested algorithm is programmed for PC and presents interest first of all in the study of residual stresses in coatings and surface layers generally. An example of application is presented.
Determination of Residual Stresses in the Coat Deposited bt Brush Plating
(DGM Informationsgesellschaft, 1993) Lille, Harri; Kõo, Jakub; Valgur, Jaak; Estonian Agricultural University
The method of continuous growth described in the article enables the determination of initial stress in the brush plated coat by the circumferential strain of the short thin-walles cylindrical cathode. The Tihonov´s method of regularization could be reccommended as an effective method of approximation of experimental data and calculation of derivative.
Extension of Kübler's model for analysis of growth stresses in tree disc
(University of Tartu Press, 2015) Kõo, Jakub; Valgur, Jaak
The layer growing/removing method for determination of residual stresses in orthotropic non-homogeneous discs has been applied as an extension of Kübler's model for analysis of growth stresses in the tree disc. The extended model permits to take account of the orthotropic characteristics and the layered structure of the tree disc. As an illustrative example, growth stresses are calculated in a disc of spruce wood from initial (maturation) stress measured on its free outer surface.
Kihilise kasvatamise/kahandamise meetodid jääkpingete määramiseks ortotroopsetes mittehomogeensetes silindrites: rakendus kasvupingete määramiseks puu tüves
(Eesti Maaülikool, 2018) Kõo, Jakub; Valgur, Jaak; Maaehituse ja veemajanduse õppetool
Kihilise kasvatamise/kahandamise meetodid jääkpingete määramiseks mittehomogeensetes ortotroopsetes silindrites pakuvad huvi jääkpingete uurimisel kihilistes komposiitmaterjalides, samuti puidu jääkpingete uurimisel ja kasvupingete modelleerimisel. Ettekandes kirjeldatakse meetodi algoritmi ja tuuakse rakendusnäitena kasvupingete modelleerimine Jaapani punase männi (Pinus densiflora) tüves. Meetodi algoritm mittehomogeensetele isotroopsetele silindritele on esitatud töös [Kõo, Valgur: 5th Int. Conf. On Residual Stresses, Linköping, 1997].
Layer growing/removing method for determination of residual stresses in orthotropic non-homogeneous cylinders
(International Centre for Diffraction Data, 2009) Kõo, Jakub; Valgur, Jaak
A unique algorithm of layer growing/removing methods for computing of the residual stresses in the incompletely orthotropic layered circular cylinder is presented. The stresses are calculated from strain measurements on the free stationary surface or from strain measurements on the cylinder's moving surface. The suggested algorithm is programmed for PC. As an illustrative example, residual growth stresses in a stem of Japanese red pine are computed from initial stresses measured on its free outer surface.
Layer Growing/Removing Method for the Determination of Residual Stresses in Inhomogeneous Cylinders
(Linköping University, 1997) Kõo, Jakub; Valgur, Jaak; Estonian Agricultural University
An algorithm of the layer growing/removing method is presented for computing residual stresses in case of the long multilayered hollow cylinder from strain measurements on the free stationary surface or from X-ray diffraction measurements on the cylinder´s moving surface. The algorithm is valid for layer growing/removing on the outer or inner surface of the cylinder and is of interest first of all in the study of residual stresses in coatings and surface layers generally. The suggested algorithm is programmed for PC. An example of application is presented.
Layer Growing/Removing Method for the Determination of Residual Stresses in Inhomogeneous Spheres
([Warsaw University of Technology], 1998) Kõo, Jakub; Valgur, Jaak; Estonian Agricultural University
A generalized algorithm of the layer growing/removing methods is presented for computing residual stresses in case of the multilayered hollow sphere from strain measurements on the free stationary surface or from X-ray diffraction measurements on the sphere´s moving surface. The algorithm is valid for layer growing/removing on the outer or inner surface of the sphere and is of interest first of all in the study of residual stresses in coatings and surface layers generally. The suggested algorithm is programmed for PC. Two examples of application are presented.
Modelling of Residual Stresses by Photoelastic Method during the Coating Deposition
(DGM Informationsgesellschaft, 1993) Kõo, Jakub; Lille, Harri; Valgur, Jaak; Idnurm, Siim; Estonian Agricultural University
A calculating scheme according to which the process of material growth is regarded as a continuous growth of the equidistant to interface elementray layers with initial stresses is widely used for determination of residual stresses in coatings (1)-(5). Since the experimental confirmation of reliability of this scheme is missing, an attempt to model the formation of stress state in the grown bar by photoelastic method has been undertaken by the authors. The research carried out confirms the validity of the scheme of continuous growth in layers and the well-known Saint-Venant´s principle.
Residual stress determination in plates using layer growing/removing methods
(Rotterdam : Balkema, 1998) Kõo, Jakub; Valgur, Jaak
A generalized algorithm of the layer growing/removing methods is presented for computing residual stresses in a free rectangular orthotropic inhomogeneous plate whose elastic parameters depend on its thickness coordinate. The algorithm allows calculation of residual stresses from strains or curvatures measured on the stationary surface of the plate as well as from initial stresses measured on the moving surface using X-ray diffraction. The suggested algorithm is programmed for PC and presents interest first of all in the study of residual stresses in coatings and surface layers generally. Three examples of application are presented.
Residual stress measurement in goated plates using layer growing/removing methods: 100th anniversary of the publication of Stoney's paper "The tension of metallic films deposited by electrolysis"
(Trans Tech Publications Ltd, Switzerland, 2011) Kõo, Jakub; Valgur, Jaak
In connection with the 100th anniversary of Stoney's equations, some historical remarks are made with respect to the development of these equations. As an example of the extension of Stoney's equations, a unique algorithm of the layer growing/removing methods is presented for determination of residual stresses in isotropic inhomogeneous coated plates. Using a computer program based on this algorithm, residual stresses are computed in the galvanic steel coating on the copper plate substrate.

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