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We analyze the stressed state of pipeline T-joints in which the connecting pipe makes an angle of 90° or 45° with the main pipe under the action of torques and bending moments causing the out-of-plane torsion and bending of the T-joint. The influence of the angle of orientation of the connecting pipe on the behavior of the stress tensor is studied for various loading modes. For all investigated loading modes, we determine the stress concentration factors according to the Maxell-More theory of specific distortion strain energy.

Conclusions 1.The hypotheses of the rod theory and the generalized plane state of strain that are used in the setting up of the method appear naturally in the case of variational formulation.2.Thanks to the identical formulation of the problems of heat conductance and thermoelasticity, the method proposed here advantageously differs from the well-known methods of algorithmic construction of finite difference equations for these problems.3.When considering variable parameters of elasticity over the section of the blade, there is no need for setting up an iterative process for the solution of the elastic problem.

Abstract: We analyze the stressed state of two types of T-joints in which the union makes angles of 45 and 90 with the main pipe. The character of the distribution of stresses in a T-joint illustrates the distinctive features of its operation under the action of internal pressure and bending moments applied in the plane of the T-joint. On the basis of the theory of strength for specific distortion strain energy, we determine the stress concentration factors for all considered loading modes. The numerical values of the stress concentration factors are compared with the experimental data obtained by other authors.

Abstract: The stressed state and stress concentration in sloping cooling circuits of the rim part of a disk of a gas-turbine engine are studied by using a three-dimensional finite-element model. It is shown that the numerical values of the stress concentration factors do not exceed their designed values.

The basic solving relationships of the finite-element method for three-dimensional nonstationary problems of heat conduction using local mixed variational formulations for an octagonal isoparametric element are obtained. To reduce the order of the system of algebraic equations, the components of the thermalflux vector (CTFV) are expressed in terms of nodal temperature values from stationary conditions relative to the variation in the CTFV, which are written for a single element. The CTFV are approximated by linear Legendre polynomials. Consideration of the orthogonality of the approximating functions within the limits of an element makes it possible to avoid the formulation and inversion of the corresponding matrices relating the CTFV and temperature. The accuracy and stability of the various schemes of discretization are analyzed as an example of the determination of the thermal state in a cube with mixed boundary conditions.

Conclusions 1.The proposed scheme for obtaining resolvent FEM equations, based on approximation of the divergence and curl of the displacement vector by element, is consistent with the classical FEM scheme.2.Having the advantages of the FEM moment scheme [6], the divergence-curl scheme permits simplification of the stiffness matrix by reducing volume integration to surface integration. It also presents the problem of optimizing the stiffness matrix of elements with a certain number of unknowns from premises of the Melosh hypothesis.3.The properties of monotonic energy convergence of the divergence-curl scheme makes it possible to use it in calculations of various problems (beams, slabs, shells, etc.) with one type of element, which is very important in developing branched program packs of universal application.

1.The proposed method, based on methods of multifactor regression analysis, makes it possible to make a quantitative analysis of the influence on the fatigue life of the metal under service conditions of a large number of factors characterizing both the condition of the metal and the components of service action, including corrosion, force, temperature, and other actions, to rank these factors by the degree of their influence on the fatigue life of the metal, and also to select the most effective criteria for evaluating various factors.2.The results obtained of quantitative analysis must be assumed to be preliminary, illustrating the effectiveness of the method developed.

Integral identities, which can be used in direct methods of constructing resolving equations of the method of boundary elements, are obtained for basic boundary problems of the theory of elasticity. As compared with familiar methods, numerical realization of integral identities is simplified and makes it possible to employ with flexibility various functions of stresses and displacements as unknowns.

1.The stress-strain state in the thickened zone of the testpiece (t2 = 2.6 mm) considerably differs from a momentless state.2.The perturbations introduced into the momentless state by the insertion of AD-1 and change in the thickness rapidly die away. At distances d = 6t1 the stress state can be considered momentless.3.The maximum value of the circumferential force N? is located in the contact zone between the alloy AD-1 and steel Kh18N10T, the maximum stresses (s?)M arising in steel Kh18N10T and exceeding 1.5–1.6-fold in modulus the stresses calculated according to the momentless theory.4.The stresses s? in the insertion AD-1 over the entire length of the insertion are less than (s?)M and differ from the latter within the limits (s?)M = 0.45–0.73.5.The maximum of the bending moment Mz falls into the contact zone between the alloy AD-1 and steel Kh18N10T; however, the values are relatively small: (Mz)max = 8.9 kgf-cm/m.