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Along with the classical finite element method (FEM), other calculation methods for assessing crack resistance characteristics are currently being actively developed. This is due to the existing shortcomings of the FEM caused by the dependence of the calculation results on the density of the finite element mesh. One of the promising methods being developed in world practice is the extended finite element method (XFEM), which allows obtaining satisfactory calculation results while simplifying the crack modeling procedure and saving calculation time. In this paper, three problems are numerically modeled using the classical FEM and XFEM methods: calculation of a disc crack in a cube under uniaxial tension, calculation of the off-center tension of a compact CT specimen, and calculation of a cylindrical part of an NPP reactor vessel with a semi-elliptical crack under thermal shock. The obtained results showed that the extended finite element method gives sufficiently accurate results compared to analytical solutions and the classical FEM. At the same time, using the XFEM method does not require considering the singularity of stresses at the crack tip when building an FE model. Therefore, the minimum size of the FE can be increased by almost five times while maintaining the accuracy of the results. This greatly simplifies the procedure for constructing the FE mesh, reduces the total number of FEs in the model, and saves computational time. Thus, the XFEM method can be used to calculate the crack resistance characteristics and improve the efficiency of assessing the resistance to brittle fracture of structural elements. [ABSTRACT FROM AUTHOR]

The paper deals with the dynamics of asymmetric three-layer hemispherical shells with the discretely symmetric lightweight, rib-reinforced filler under pulsed loads. Since the distances between the ribs are much larger than the dimensions of the rib cross-sections, the theory of independent static and kinematic hypotheses for each layer is applied. In asymmetric shells, the load-bearing layers are made of different materials and have various thicknesses. The equations of motion of asymmetric three-layer spherical shells and natural boundary conditions are obtained using the Hamilton– Ostrogradsky variational principle for the Timoshenko-type shell and rod theory model. This makes it possible to develop an adequate finite element model for asymmetric three-layer shells composed of several materials and obtain numerical results on the dynamic behavior of an asymmetric three-layer elastic structure using the finite element method. The influence of physical and mechanical parameters of asymmetric layers of hemispherical shells on the stress-strain state under axisymmetric internal pulse loading is investigated. New mechanical effects are revealed. [ABSTRACT FROM AUTHOR]

Recently, much attention has been given to developing numerical modeling methods for calculations of complex nodes of structural elements, especially for the equipment of the first circuit of NPP. The use of new methods increases the accuracy of the results and significantly reduces the calculation time. This is especially important when solving the problems of modeling the processes of crack nucleation and propagation in the material, in which, in particular, local thickening of the finite element mesh is necessary. In this paper, a description of the "submodeling" technique is given, which allows one to calculate individual components of structural elements, taking into account complex geometric shapes, contact conditions, and other factors that are difficult to take into account in calculations by conventional methods. The submodeling technique was used to calculate the stressstrain state in complex components of the pressure compensator of the WWER-440 reactor unit. For this purpose, a global simplified finite element model of the pressure compensator and a detailed submodel of the injection nozzle were built, taking into account the gap between the containment and the inner surface of the nozzle, as well as contact conditions. The results showed that the submodeling technique gives more conservative results when modeling complex assemblies. Hence, its application increases the reliability of the results obtained when assessing the strength of critical structural elements, particularly the equipment of the first circuit of NPP. [ABSTRACT FROM AUTHOR]

In this paper, reinforced thermoplastic pipes (RTP) were studied under various loads. A total of five groups of specimens were designed to study the mechanical properties of RTPs under internal pressure, bending, a combination of internal pressure and bending moment, external pressure, and tension. This study obtained the bursting pressure of RTPs under internal pressure, the minimum bending radius under the bending moment, and the failure pressure under external pressure. At the same time, the mechanical properties of RTPs under various loads were analyzed using the finite element analysis. Analytical results agree well with the experimental ones. The finite element model established in this paper can be used for further research on the mechanical properties of RTPs. [ABSTRACT FROM AUTHOR]

Special features of computational assessment of dimensional change of WWER-1000 reactor core baffle during the reactor operation are discussed. The paper gives results of computational analysis of a change in shape of core baffle, which was performed by applying up-to-date approaches of modeling the irradiation-induced swelling of constrained austenitic steels under the action of neutron irradiation and elevated temperatures. The results have been obtained by using median and conservative values of parameters of the temperature and dose dependence of free swelling of austenitic steel Kh18N10T. The authors have set out the fundamental principles of elastic-plastic stress-strain analysis of the reactor core baffle and core barrel, taking into account the irradiationinduced swelling deformation and contact interaction conditions. The finite-element analysis is based on a FEM mixed scheme that ensures a continuous approximation both for displacements as well as stresses and strains, thus providing a high-accuracy determination of the stress-strain state. The calculations were carried out in the two-dimensional definition for the baffle cross-section with the maximum damaging dose and irradiation temperature in the baffle height, assuming a generalized plane-strain deformation. The calculated results are given for the reactor full-power operation and scheduled shutdown for re-fueling at the end of the charge life. According to the calculation data, disregarding the irradiation-induced swelling deformation leads to an incorrect assessment of the change in shape of the core baffle during its operation, while the use of the accepted free swelling model gives too conservative results on the shape change, even within the designed lifetime. The influence of the mean normal stress on the irradiation-induced swelling of metal makes the principal contribution to the change in shape of the core baffle. During the reactor operation beyond the designed lifetime there occurs a local contact between the core baffle and the core barrel in the zone of the largest-diameter circular opening of the longitudinal cooling channel and the port channel for coolant flow between the baffle and the barrel. The paper gives results of the analysis of the change in shape of the baffle in modeling of the contact conditions taking into consideration the temperature re-distribution due to deviation from the design coolant passage conditions in the zone where the baffle is in contact with the barrel. In the case of using the median dependence of the free swelling, no loss of the nominal gap between the core baffle and the core barrel is observed within the designed lifetime. The computational assessment using the conservative parameters of the irradiation-induced swelling leads to a distinct decrease of the gap between the core baffle and the core barrel and a local contact between them at the end of the designed lifetime. The residual gap between the spacer grids of edge fuel assemblies and the baffle faces is ensured in the case of the median and conservative dependence of the irradiation-induced swelling. [ABSTRACT FROM AUTHOR]

Stress is one of the most important factors in metal-to-metal sealing. In this paper, two methods (theoretical and empirical) were adopted to calculate the normal stress of the brass sealing surfaces against different ultrahigh pressure liquid. The theoretical formula was derived in terms of force balance, and the empirical formula was obtained by polynomial curve fitting, which the fitted data were from simulated results; besides, the results calculated by using the empirical formula agree well with the results by theoretical formula. Meanwhile, the equivalent stresses of the brass seal, normal stress and contact stress on the brass seal surfaces were simulated by finite element method, and the simulated results indicated these stresses are increased with the increase of liquid pressure, and the maximum stresses always appear on the tip of the brass seal. [ABSTRACT FROM AUTHOR]

The paper presents the results of the application of the refined calculation guidelines to the analysis of the stress-strain state and fracture resistance of the equipment elements of the NPP primary circuit system with WWER reactor, in particular, the cylindrical part and the zone of the reactor pressure vessel inlet nozzle, coolant collector welded joint in a steam generator, baffle, and reactor internals' shaft under the operating and emergency modes of thermomechanical loading. The calculation methodology is based on the use of the modern models and methods of solution to the nonlinear boundary tasks of non-isothermal thermal viscoplasticity and tasks of fracture mechanics using the refined mixed schemes of the finite element method with increased accuracy. They allow one to obtain reliable solutions to the tasks considering the deformation history of thermomechanical loading, modern concepts of fracture mechanics and approaches to the modeling of brittle-viscous fracture defects, irradiation swelling and creep of metal, as well as as the structural elements, under the conditions of elevated temperature, intensive neutron irradiation and nonstationary modes of thermomechanical loading. The authors obtained and analyzed the calculation results for the cylindrical part and zone of the inlet nozzle of the WWER-1000 reactor pressure vessel, coolant collector welded joint in a steam generator, baffle, and reactor internals' shaft using the proposed guidelines. The results imply the possibilities of the proposed recommendations and make it possible to analyze some general tendencies and features of the application of the refined calculation models to justify the strength and life extension of the NPP structural elements under investigation. [ABSTRACT FROM AUTHOR]

The paper deals with the numerical stress calculation in the flexspline tooth rim of the harmonic drive. Due to the complex geometry of the toothed ring in the flexspline, the teeth were modeled as a ring, which height corresponded to the particular stress concentration in the teeth. To study the effect of type of wave generator on the stress distribution in the flexspline, the following models were elaborated: two-roller, four-roller, cam, and disk. The stress calculations were performed for the two cases: a zero torque load and the torque load value, corresponding to the true operation conditions of the hermetic harmonic drive. [ABSTRACT FROM AUTHOR]

This paper proposes an analytical model for the stress-strain state in a welded joint with a hard single-V butt weld. Analytical expressions for the stress-strain state in both the hard weld and the mild main material subjected to elasto-plastic deformation are proposed. In order to verify the proposed expressions, a finite element simulation of the stress-strain state in a welded joint with a hard single-V butt weld was carried out and the results were compared to the analytical results obtained applying the proposed analytical model. The analytical solution was basically consistent with the finite element analysis results. The proposed analytical model can be used in design practice for assessment of the stress-strain state in welded joints. [ABSTRACT FROM AUTHOR]

The statistical analysis performed on the defectiveness of rails in the Kiev subway railway shows that the main cause of the occurrence of most defects is the contact fatigue of the rail material. The paper presents modern concepts of crack growth in the railhead. It has been found that one of the most promising directions of studying the stress-strain state of rails and the crack growth process is a numerical simulation, which results on the contact interaction between rails and subway rolling stock wheels are presented. During the simulation, the problem was solved in an elastic formulation. We considered R50, R65, and UIC60 rail profiles, standard railway wheels, and wheels whose tire profile was developed by the Minetek closed joint-stock company. The conditions for the rail–wheel interaction corresponded to train movement on the straight section of the track without slipping. The effect of the wheel tire profile on the contact stress level in rails of different types has been assessed. Comparison of the maximum equivalent stress levels for a different combination of rail and wheel types shows that the best combination (in terms of reducing the contact stress level) for the straight sections of the subway track is an R50 rail with a gradient of 1 in 20 and 1 in 10 taper wheel, whose profile corresponds to GOST 9036-88. When wheels with the profile developed by the Minetek company are used, the maximum equivalent stress level in the contact zone is over 1000 MPa for all rail types. It is higher than the yield strength of rail steel, which will accelerate wear and give rise to low-cycle fatigue cracks with subsequent formation of contact fatigue defects. [ABSTRACT FROM AUTHOR]

The paper considers the results of determining the vibrodiagnostic indicators of the presence of various mode I breathing transverse cracks in rod elements of rectangular and circular cross section with different boundary conditions under longitudinal vibrations. Relative second harmonic amplitudes in the vibration spectrum at the main and superharmonic resonance of the first eigenmode of cantilever rods without mass and with a mass at the end and rods with the ends free for longitudinal displacements under forced and kinematic vibration excitation were taken as diagnostic indicators. To determine the above indicators, analytical and numerical bending vibration methods considered before are used. In the analytical solution, the nonlinearity parameter of the vibrating system is calculated using the corresponding values of stress intensity factors. The numerical solution is performed on the basis of eight-node finite element models with the representation of a breathing crack as a mathematical cut and the treatment of a contact problem in the formulation providing mutual nonpenetration between crack faces. Plots of the values of diagnostic indicators as a function of relative crack depth, crack location and the site of measurement of longitudinal displacements have been obtained. Comparisons of values of diagnostic indicators with the value of relative change in natural vibration frequency are presented. It has been shown that at the main resonance, the numerical solution confirms the pronounced effect of localization of diagnostic indicators in the crack region. It has been found that at the superharmonic resonance, the value of the vibrodiagnostic indicator is two orders of magnitude higher than that of the indicators at the main resonance, but the effect of their localization near the crack does not practically manifest itself. Some localization is observed for the absolute values of the second harmonic, and only for longitudinal strain, there is a strongly pronounced effect. A comparison of the obtained values of diagnostic indicators with the data for bending vibrations is given. It is noted that in spite of basically lower indicators under longitudinal vibrations, they have an advantage in terms of the possibility to diagnose symmetric both surface and internal breathing cracks. [ABSTRACT FROM AUTHOR]

The paper provides the strength analysis performed for POLYITAN-2 nano-satellite under quasistatic overload conditions arising at the ascent stage. An efficient solid-state model together with its corresponding finite element model has been developed for nano-satellite. The numerical investigation of the stress-strain state of nano-satellite has been performed using the ANSYS software package. The maximum relative displacements of structural elements, as well as safety factors, have been determined. Different strength criteria were analyzed for the strength assessment of nano-satellite structural elements made of composite materials. It is found the considered POLYITAN-2 structure satisfies the critical strength and stiffness requirements. [ABSTRACT FROM AUTHOR]

The paper addresses the temperature and thermoelastic states of a single-crystal blade with a complex vortex cooling system and passages for cooling air outflow. The problem of determination of stress-strain state of the blade at hand under the action of temperature fields and centrifugal forces is solved by the finite element method. The authors study the influence of azimuth orientation of crystallographic axes on the distribution and magnitude of thermoelastic stresses in the blade volume. [ABSTRACT FROM AUTHOR]

Accelerated life testing (ALT) is an effective way to assess the lifetime of a product. Due to the complex nature of its testing profile, it is difficult to carry out temperature cycling ALT. This paper establishes a modified Norris-Landzberg model as acceleration model, and proposes the optimum design method of temperature cycling ALT. First, the FEA method is used to study the influence of temperature cycling profile parameters on the thermal fatigue life of 63Sn-37Pb solder joints. Then, a modified Norris-Landzberg model is proposed by introducing ramp time and dwell time with an added weight value. Finally, the temperature cycling ALT is regarded as a special multi-stress ALT to study its optimum design method. The uniform design theory is used to determine the combined mode. The optimum model is established with the objective of minimizing the asymptotic variance of the estimation of median lifetime under normal use conditions, and the simulation example shows the workability of the proposed method. [ABSTRACT FROM AUTHOR]

The paper outlines the methodological approach and the related software package, which permit determining stress-strain state and defect rate for full-scale crack-containing objects. The method is based on computational assessment of the above-mentioned parameters on the condition of minimum of the objective function that describes discrepancy between the experimental data arrays and the results of numerical solutions to model problems using the finite-element method. [ABSTRACT FROM AUTHOR]

Experimental testing and non-linear finite element analysis using discrete reinforcement modeling of six numbers of reinforced concrete beams under four-point bending are presented in this paper. Finite element modeling of reinforced concrete beams is carried out using ANSYS 12.0, and the critical values of the results are also compared with analytical values calculated using IS 456: 2000 codal provisions. Wide-range graphical display of the results such as deflected shape of the beam, stress-strain variation along the length and depth of the beam and crack propagation is generated by creating a batch file using the ANSYS parametric design language. Comparison is made between the test results, finite element analysis and analytical values with respect to initial crack formation and the ultimate capacity of beams, in order to have a wide understanding on the behavior, which may reduce the physical destructive laboratory testing for the future researchers. [ABSTRACT FROM AUTHOR]

In this paper, the strain paths occurring in an anisotropic aluminum target under its impact loading are considered. The calculations are performed in a three-dimensional formulation using the finite-element method. The relationship between the “kinks” in the strain paths at different points of the target and the wave pattern of the deformation is shown. [ABSTRACT FROM AUTHOR]

A three-dimensional stress-strain state calculation is performed by the finite-element method for precracked Charpy specimens side grooves of different depths. Based on the calculated results, the paper addresses the suitability of various brittle fracture criteria to describe experimental data on fracture toughness of these specimens. [ABSTRACT FROM AUTHOR]

We describe the effect of the stacking sequence on the distribution of the deformation and stress fields through the thickness of the laminate. The laminates are made of epoxy resin and glass fibres, having the ratio of 0 to 90° plies equal to 1. This stacking sequence is applied to obtain composite laminates with different thicknesses. The study presented in this paper is focused on the linear static behavior of the cross-ply laminates by means of finite-element models developed using the commercial codes ANSYS 6.1 and LUSAS 15.3. The numerical models represent three-point bending loading cases. A viscoelastic analysis of the laminates based on the correspondence principle is also performed. The results from the finite-element models show good agreement with those obtained using the classical laminate theory, while the viscoelastic storage modulus and loss factors’ distribution indicate the optimal stacking sequences for structural dynamics applications, such as spring leaves for novel car suspension systems. [ABSTRACT FROM AUTHOR]

The aim of this finite element stress analysis (FEA) study was to assess the effect of separated files (SF) that were broken at two levels (at apical 4 and 9 mm) on the biomechanics of premolars and to determine if removal techniques affect stresses. Six lower premolar teeth were screened on computerized microtomography (micro-CT), standard access cavities were prepared, working lengths were determined, and root canals were prepared (Protaper files, Protaper Universal, Dentsply, Switzerland). Notches were created on the final shaping-file F3 at points 4 and 9 mm from the file tips, inserted in the canals, and squeezed at the apical to break. The roots were rescreened, and SFs were removed by using a Masseran kit (MK; Micro Mega, France), ultrasonic tips (UT; Satelec, Acteon group, France), and the bypass (BP) technique. Final scans were obtained and converted into three-dimensional FEA models. The following conditions were then simulated: a) root-filled tooth with SF; b) root-filled tooth after removal of the SF by using MK, UT, or BP techniques. The models were loaded axially (from two directions) and vertically (300 N), and von Mises stresses were then analyzed. SFs increased the stresses within the root. Longer SFs cause higher stresses within the root and thus should be removed, while short SFs could be kept considering the other clinical factors. Removal via MK caused the highest stresses within the roots among the techniques used. Axial loading caused higher stresses at the cervical side, while the stresses moved toward the apical side under vertical loading. SFs increase the stresses within the root. Long SFs should be removed while short SFs can be left (considering other clinical factors that may affect the success of the treatment). Removing short SFs located at the apical side negatively affects the biomechanics of the teeth, and this effect is more dramatic with the MK technique. [ABSTRACT FROM AUTHOR]

This work is devoted to the determination of vibrodiagnostic indicators of the presence of symmetric and annular breathing cracks in cantilever beams at their nonlinear longitudinal vibrations. The results of determining the vibrodiagnostic indicators of the presence of cracks, namely, the relative change in the fundamental frequency of longitudinal vibration and the ratio of the amplitudes of the dominant harmonics at the fundamental and superharmonic resonances for different depths and locations of cracks, are presented. To carry out computational studies, various computational models were developed, namely, with concentrated and distributed parameters, beam and volumetric finite element (FE) models, and methods for their research. The use of the model with concentrated parameters consists of the analytical determination of the nonlinearity parameter of the system, which takes into account the change in the stiffness of the system in the presence of damage and is determined by changing the potential deformation energy of the beam due to the opening of the crack during oscillations. The determination of vibrodiagnostic indicators of the presence of a crack using a model with distributed parameters is carried out by solving the differential equation of forced longitudinal vibrations of the second order, where the crack is represented as a section of the beam with a reduced cross-sectional area. The numerical analysis of vibrations of the objects of study with a breathing crack is carried out using the developed beam and volumetric FE models. In the beam FE model, the breathing crack is modeled by a finite element with variable stiffness, and in the volumetric model, it is represented as a mathematical section with the setting of contact interaction conditions for its banks. The main dependences of vibrodiagnostic indicators of the presence of cracks on their parameters are obtained analytically using a model with concentrated parameters and numerically using a beam FE model. To confirm the reliability of the obtained dependences, their individual values are compared with the data obtained for the volumetric FE model, which obviously describes the stress–strain state in the vicinity of the crack most accurately among the proposed models but at the same time requires more computational resources. The obtained numerical dependences of the ratio of the amplitudes of the dominant harmonics of displacements at the main resonance from the place of vibration registration are characterized by fractures in the vicinity of the crack and therefore can be used to determine the location of the crack. According to the results of the analysis of the obtained dependences, it was found that it is practically impossible to determine the location of the crack in this case, since the results obtained for the relative location of the crack in the range from 0.1 to 0.5 are close in values, and the dependences of the vibrodiagnostic indicator on the place of registration of vibrations at superharmonic resonance are uniform and have no fractures. [ABSTRACT FROM AUTHOR]

The authors present the results of computer simulation of the stress-strain state of a thin-walled spherical shell with an elliptical opening and the surrounding reinforcing inclusion of another material. The effect of geometric and mechanical parameters of inclusions on the stress distribution around the opening and deformation of the shell under uniform internal pressure are investigated. The issue of stress concentration in modern leading fields of technology and industry, namely, in mechanical engineering, rocket, and space, is quite topical since it is associated with the reliability and durability of the designed structures or their elements. Stress concentrators can occur due to imperfections in the materials' structure (cavities, cracks, foreign inclusions, etc.) or technological and structural necessity (openings, cutouts, leaks). Shell structures are used as load-carrying structures in many fields of engineering. They combine high strength with low weight, which contributes to their reliability and safety during operation. In most cases, shells in real structures have simple geometric surfaces (shells of rotation). Complex structures are usually a combination of such shells. It is important to investigate the effect of local stress concentrators as openings (considering inclusions) on the stress-strain state of shells. The methods of stress concentration reduction should be outlined. The authors performed a finite element analysis of the effect of reinforcements modeled by inclusions made of the different materials as compared with the shell material having an opening on the parameters of its stress-strain state. Such investigations are crucial for the design and optimization of the structures in many engineering fields. [ABSTRACT FROM AUTHOR]

The residual stresses and deformation, in terms of the thermoelastoplastic theory, were simulated with the finite element method using ANSYS 13.0 software for a 5A06 aluminum alloy plate after welding. The butt joint thickness of the plate was 6 mm. A 3D thermomechanical model of the plate was constructed. The dimensions and distribution of residual stresses in the welded structure should be analyzed after simulation. Appropriate welding technologies were chosen to control welding residual stresses and deformation. The efficient production of an aluminum alloy for the welded structures will be provided. [ABSTRACT FROM AUTHOR]

Tooth contact area optimization/meshing of the straight worm pair is vital for improving its operation efficiency. Geometric parameters of a worm helicoid were derived via the gear meshing theory using the equations of the instantaneous contact line. The visualization function and powerful computing capability of MATLAB are used for the numerical analysis where the instantaneous contact line distribution is simulated for particular worm drive parameters, which yields the induced curvature and slip angle in the direction of the line. The above results are used for further optimization of the meshing performance of the straight worm gear and identification of its influencing factors. A case study of the particular cylindrical worm gear in compliance with the GB 10085-1988 Standard of China demonstrate that a reasonable selection of worm gear parameters can extend the contact line and the working range of the tooth surface of the worm gear and/or make the contact line distribution along the worm wheel more uniform, thus improving the local meshing performance. [ABSTRACT FROM AUTHOR]

This study presents a numerical assessment of a crane for elevation of personnel by finite element analysis, validated with experimental data from constituent components of the crane. The original design of the crane consists of a jointed section of coplanar arms and a telescopic section of collinear arms. As a reference, the standard ANSI/SIA 92.2 was used to determine maximum loads and the consequent effects on the constituent components of the crane. This standard is suitable for crane designs distributed and commercialized in Mexico. The proposed numerical analysis is carried out through a finite element analysis, which is based on the assembly method of kinematic pairs, taking into account dynamic loads and their resulting reaction at each element. The mechanical performance of each component is assessed with the minimal security factor parameter. However, in those components where the minimum security factor was insufficiently in accordance with the standard, a variety of modifications to redesign a given component was proposed. Subsequently, a detailed structural analysis on the proposed redesign was carried out, in which higher security factors were obtained in comparison to the original design. Finally, the numerical results of the proposed redesign were validated through experimental measurements of strain, using strain gauges attached on a crane prototype, which was manufactured according to the proposed redesigned model. [ABSTRACT FROM AUTHOR]

A method is described to calculate creep and damage in structural elements under cyclic loading. Materials exhibiting anisotropic creep-damage behavior are considered. The results of calculating the deformation and fracture of structural elements at a plane stress state are presented. [ABSTRACT FROM AUTHOR]

For studying the vibration characteristics of a laminar composite rotating blade, the spin softening effect calculated by the finite element method (FEM) was incorporated with the prestress effect to analyze shaking, swing, torsion, and coupled vibrations. The mathematical formula was derived. The study shows that the centrifugal force exerts influence on the difference in vibration frequencies. The laminar composite can reduce an influence of the spin softening on the first swing vibration frequency because of its structure and smaller density. With the variation of rotating velocity, the blade spin softening can lead to the coupled first shaking and first swing vibrations. In the coupled vibrations, swing is contained in the shaking mode and shaking is also contained in the swing one, which is the reason of major blade damages. The results confirm the complexity of the dynamic characteristics of the laminar composite rotating blade. This method is also well applicable to the dynamic design of such blades. [ABSTRACT FROM AUTHOR]

The presented research results imply a certain relationship between elastic and plastic parts of strain. Based on the preliminary summary of this relationship, a new strength criterion is proposed, which can be treated as modification of the maximum principal strain criterion. Since the proposed approach establishes a relationship between strength and yield criteria, it can also be treated as a new yield criterion. [ABSTRACT FROM AUTHOR]

Finite element analysis has been carried out to obtain the interfacial stresses in a single lap joint using a special 6-node isoparametric element for adhesive layer. The analysis results are found to be in good agreement with the closed-form solution of Goland and Reissner. The peak normal and shear stresses found in the adhesive layer at the edges of the joint are due to stress singularity. The bond strength of the single-lap joint is estimated considering one of the stress fracture criteria known as the point stress criterion. Bond strength estimates are found to be reasonably in good agreement with existing test results. [ABSTRACT FROM AUTHOR]

The authors present the calculation results for the stress-strain state of the weldment of the 'hot'collector to the nozzle in the PGV-1000 steam generator in the area of welded joint No. 111 in the simulation of the seismic loading specified using the response spectra for the vertical and horizontal vibrations. The calculation of seismic stresses is performed based on the linear-spectral analysis using the three-dimensional model of the WWER-1000/338 reactor plant. [ABSTRACT FROM AUTHOR]

Results are presented for both the calculated assessment of the residual manufacturing stress fields in the simulation of the heat treatment in the vicinity of welded joint No. 111, and the calculation analysis of operating stresses and the fracture resistance of the collector-to-nozzle welded joint in the PGV-1000M steam generator in the simulation of the operating loading cycle. [ABSTRACT FROM AUTHOR]

The contact pressure distribution of the curvic couplings in a heavy duty gas turbine under a blade-off load condition is investigated in a three-dimensional finite element model. Several blade-off positions on each stage disk may develop the different characters on the contact pressure distributions of the curvic couplings during the application of a blade-off load. Both the position and magnitude of the applied blade-off load and the distribution of the spindle bolts have an effect on the contact pressure distribution of the curvic couplings. Further the contact stress on the left and right sides of the teeth develops different characters during the application of torque load following not only a normal centrifugal load but also a blade-off load which produces a unbalanced equivalent bending force. Furthermore the stiffness of the connection body part of the rotor between the compressor end and the turbine end associated with its section thickness is crucial in deciding the contact stress distribution on the curvic couplings. This analysis shows a change in the magnitude of contact stress of each set of the curvic couplings. [ABSTRACT FROM AUTHOR]

A modification of a method for the determination of limiting pressure for gas and oil pipelines with corrosion damages of local type under the action of internal pressure and with allowance for temperature field is considered. The problem is solved numerically in three-dimensional formulation. Particular numerical examples illustrate the general design procedure and show satisfactory agreement with experiment. [ABSTRACT FROM AUTHOR]

procedure for the determination of stress intensity factors of 3D flat cracks is proposed, which uses integral identities for displacements and strains on the crack surface. New formulations of boundary problems of the mathematical theory of linear fracture mechanics have been obtained, which are used to develop finite element models. The unknown functions are nodal displacements on the crack surface. The data given are compared with analytical solutions and results obtained by other methods. [ABSTRACT FROM AUTHOR]

method for calculating the fields of parameters of the stress-strain state at the crack tip for mixed modes of loading is developed and implemented taking into account the higher-order terms. The influence of the final crack tip curvature radius on the parameters characterizing the mixed failure modes under plane strain is shown. The nature of influence of the mixed modes of loading and the crack geometry on the behavior of dimensionless angular characteristics of the second term in the expansion of the stresses in the plastic crack tip region is established from the calculation results. The relationships between the mixing, constraint and triaxiality parameters are derived in a full range of mixed deformation modes. [ABSTRACT FROM AUTHOR]

We address the effects of the actual flight cycle on durability of gas turbine engine disks under low-cycle fatigue. An approach is proposed which improves reliability of life cycle prediction owing to schematization of flight cycle with a criterion for reaching the maximum intensity of total strain range. Contribution of subcycles to the cumulative damage is demonstrated. [ABSTRACT FROM AUTHOR]

A mixed projection-mesh scheme for solving a boundary-value problem of thermal plasticity is formulated in a quasi-static statement when the process of non-isothermal elastoplastic deformation of a body is a sequence of equilibrium states. In this case, the stress-strain state depends on the loading history, and the process of inelastic deformation is to be observed over the whole time interval under study. The correctness and convergence of the mixed approximations for stresses, strains and displacements are investigated as applied to the solution of nonlinear boundary-value problems that describe the non-isothermal processes of active loading taking into account the initial strains dependent on the history of deformation and heating. The properties of the projecting operators are studied in detail, and on this basis, the condition that ensures the existence, uniqueness and stability of solution is formulated. The results of the analysis of special formulas of the interpolation-type numerical integration are presented, the use of which considerably simplifies the computation procedure for solving equations of the mixed method. The convergence and accuracy estimations are based on the results of the theory of the generalized boundary-value problems and methods of the functional analysis. According to the estimations obtained, the accuracy of solution of a finite-dimensional problem at the initial stages of loading should be sufficient to avoid the effect of increase of the first coefficients in the expansion of the total error on the accuracy of solution of the elastoplastic problem at the subsequent stages of loading. [ABSTRACT FROM AUTHOR]

Based on 3D finite-element models, a procedure for analyzing a spatial stress-strain state in the stator-scroll assembly of hydroturbine units has been developed. It allows determination of stresses and their localization zones in structures that contain not only identical but also similar components. The output data visualization makes it possible to identify the places of stress localization in the system and in its components. [ABSTRACT FROM AUTHOR]