Jakub Kõo

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

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Algparameetrite meetodi ühest esitusvariandist tugevusõpetuses
(Eesti Põllumajanduse Akadeemia, 1990) Kõo, Jakub
Tavaliselt esitatakse õppekirjanduses algparameetrite meetod staatika määratava tala sisejõudude ja siirete määramiseks eraldi. Allpool käsitletakse algparameetrite meetodi üldistatud varianti, mille puhul talale mõjuvad koormised esitatakse Diraci ja Heaviside´i funktsioonide abil lauskoormistena ning sisejõud ja siirded määratakse ühtse metoodika järgi sõltumata staatika määramatuse astmest.
Boundary effect in the case of deposition of the coating on a free edged thin-walled tube : [full text in Russian]
(Eesti Põllumajanduse Akadeemia, 1974) Kõo, Jakub
The boundary effect at deposition of a coating on a thin-walled tubular substrate with free edges is examined. Using the equation of radial displacements of the long cylindrical shell with a uniform moment load on the edge, it is shown that with a precision of 5% the boundary effect can be considered attenuated at a length according to expression (7) where r₁ , h₁ and h₂ are given by Fig. 1, k = h₂/h₁ and µ is the Poisson´s ratio which is identical for substrate and coating materials.
Determination of residual stresses in cylinders with coatings : [full text in Russian]
(Eesti Põllumajanduse Akadeemia, 1977) Kõo, Jakub
Experimental determination of residual stresses in coated long hollow circular cylinders by measuring circumferential and longitudinal strains at material adding or removal is considered. Metrological equations for radial and circumferential residual stresses (6) and (7) are derived by using Lame´s formulas. Equation (10) for calculation of axial stress is obtained from the integral expression of the longitudinal force. Metrological equations (11) for a thin-shelled cylinder are presented.
Investigation of residual stresses in electrodeposits by strain measurement of a thin-walled tubular cathode : [full text in Russian]
(Eesti Põllumajanduse Akadeemia, 1969) Kõo, Jakub
A method for experimental determination of residual stresses in electro-deposits is described. According to this method a deposit to be investigated is deposited on the external surface of a thin-walled tubular cathode (Fig. 4) placed in a tank with rotating anodes (Fig. 3). At the same time, by using electrical-resistance strain gauges on the internal surface of the cathode strains are measured as a function of variable deposit thickness. Initial stress and residual stresses are determined via approximation of experimental information, applying the method of averaged sum. Determination of elastic constants of the substrate and coating materials is described. Technological problems of strain measurement are considered. An example of the processing of measurement data is presented. Initial stresses are determined for a number of cathode materials and galvanic iron coatings (Table 3).
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].
Modelling of the bending of a coated straigth strip substrate : [full text in Russian]
(Eesti Põllumajanduse Akadeemia, 1988) Kõo, Jakub; Lille, Harri
In the present paper the following problems are addressed: 1) bending of a plate at coating growth or removal; 2) bending of a plate with coating at temperature variation troughout thickness; 3) bending of a plate with a coating loaded by concentrated forces; 4) thermoelastic modelling of the bending of a coated straigth strip substrate by using thermoelastic bimetallic strips. It was found that at coating growth or removal the composite substrate- coating with a relative width of b/l= 0.05-0.5 bends like a plate that is non-homogeneous troughout thickness and is subjected to uniformly distributed edge moments (pure bending). However, in the case of a concentrated moment, the same substrate-coating behaves like a nonhomogeneous beam.
On Calculation of Electrocrystallization Stresses by Deformation of a Band Cathode : [full text in Russian]
(Eesti Põllumajanduse Akadeemia, 1969) Kõo, Jakub; Eesti Põllumajanduse Akadeemia
Revision of the method for calculation of electrocrystallization stresses by deformation of a band cathode proposed by M. J. Popereka [1-3] is suggested. Use of a during the coating process freely deforming rectangular plate cathode clamped in the limited region of the edge (see Fig.2) is proposed for rise precision.
Once again about the force and deformation methods for determination of residual stresses in clamped bars and plates with coatings : [full text in Russian]
(Eesti Põllumajanduse Akadeemia, 1971) Kõo, Jakub
Metrological equations for the indicated experimental methods are presented for rigidly clamped and slipping clamped substrates. It is pointed out that the equations derived remain valid when the layer adding or layer removal techno-logy is applied.
Thermoelastic Stresses in Multilayered Plates Under Variable Heating in the Direction of Thickness :[full text in Russian]
(Eesti Põllumajanduse Akadeemia, 1959) Kõo, Jakub
Thermoelastic equilibrium of multilayer isotropic plates (Fig. 1) Under variable heating in the thickness direction in considered. Proceedings from the well-known Kirchoff’s hypotheses, it is demonstrated that in the case of small deflections the solution of probleme is reduced to integration of differential equations (30) and to satisfy the boundary conditions for functions φ (stress function) and w (deflection function) where D’ designate reduced bending stiffness of a multilayered plate. Of the special cases for a plate with an arbitrary contour, the following fixing conditions are considered: 1) fixed edges (Fig. 3), 2) slipping edges (Fig. 4), 3) free edges. It is shown that for a plate with fixed or slipping edges w=0, but for a free plate w = 0,5K (x²+y²), i.e. a free plate is bent to spherical surface (K is a constant). Formulae (46), (47) and (57)-(60) may be readily adapted to calculate eigenstresses (residuals stresses) in galvanic coatings by the experimentally measured curvature at unilateral coating of a plate cathode.

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