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1.
Yu. A. Radin I. A. Grishin T. S. Kontorovich O. B. Panshina A. V. Chugin 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2006,40(2):113-119
Problems arising with connecting the second exhaust-heat boiler to the first exhaust-heat boiler under load in the case of
flow circuits of combined-cycle plants of type PGU-450 are considered. Similar problems exist for two-boiler single-turbine
units of type PGU-325 and for two-boiler single-turbine units of traditional steampower plants with an output of 200–300 MW
upon connection of the second furnace of a two-furnace boiler to the operating first furnace. Analysis of the temperature-induced
stressed state and of the cyclic strength of thick-walled elements of the steam-water conduit of PGU-450 and of two-furnace
boilers of two-boiler single-turbine units with an output of 200–300 MW (the check valve, the inlet header of the water economizer)
is used for determining the steam temperature differences in the high-pressure conduits to the steam turbine and the order
of connection of the second exhaust-heat boiler to the operating fist one. Modes of enabling a two-boiler single-turbine unit
of a combined-cycle plant, which are most “rigid” from the standpoint of thermal strength, are determined.
__________
Translated from élektricheskie Stantsii, No. 2, February 2006, pp. 11–17. 相似文献
2.
L. T. MO M. HUURMAN S. P. WU A. A. A. MOLENAAR 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(9):823-831
Tensile fatigue behaviours of bitumen–stone adhesion were investigated using a dynamic mechanics analyser under stress‐controlled mode at two temperatures of 5 and 25°C and various controlled‐stress levels. Failure characteristics including interfacial failure and cohesive failure were examined using image analysis of fracture surfaces. Finite‐element analysis on stress distributions was conducted under different temperatures, film thickness and interfacial bonding conditions. A Coulomb–Mohr like criterion in combination with shear and normal stresses is proposed to deal with the extreme thin adhesive layer, which can be further simplified into an adhesive zone without significant loss of accuracy for stress analysis. 相似文献
3.
A new method is outlined which aims to predict high-cycle fatigue behavior of components which fail from stress-concentrators. This involves examination of the stress field in the vicinity of the stress-concentrator, and comparison with stress fields for cracks at known stress intensities. Methods which are currently used for simple notch geometries can thus be generalised, making the approach applicable to stress concentrators of any geometry. The method of prediction is shown to be stable, providing a solution of good accuracy when compared to analytical methods for standard specimen geometries. Favourable comparisons with experimental data have been achieved both for standard notches and for a corner geometry which represents a typical component case. 相似文献
4.
5.
Mahyar S. Dadkhah David B. Marshall Winfred L. Morris Brian N. Cox 《Journal of the American Ceramic Society》1991,74(3):584-592
Residual strains responsible for crack tip shielding have been measured within transformation zones surrounding cracks in Mg-PSZ. Two techniques were used for strain measurement: moiré interferometry and high-resolution image matching. Both methods provide maps of differential in-plane displacements within the specimen surface intersected by the crack, the latter method with the higher resolution. The results are compared with finite-element analysis to assess surface relaxation effects, and the measured strains are used to evaluate the crack tip shielding stress intensity factor. Calculations based on the assumption that the unconstrained transformation strain is hydrostatic dilatation yielded results that were significantly smaller than the measured toughness increases. 相似文献
6.
Effect of extrusion wheel angular velocity on continuous extrusion forming process of copper concave bus bar 总被引:2,自引:0,他引:2
The continuous extrusion forming process for producing large section copper concave bus bar under different extrusion wheel angular velocities was studied by three-dimensional finite element technology based on software DEFORM-3D. The rigid-viscoplastic constitutive equation was employed in the model. The numerical simulation results show that the deformation body flow velocity in the die orifice increases gradually with the increase of the extrusion wheel angular velocity. But slippage between the rod and extrusion wheel occurs when the extrusion wheel angular velocity is high. The effective stress near the die orifice enhances gradually with increasing extrusion wheel angular velocity. High stress is concentrated in adjacent regions of the flash gap. The effective strain gradient is greater near the abutment than that near the die orifice. The effective strain of the product increases gradually with increasing extrusion wheel angular velocity. In the deformation process, the deformation body temperature increases remarkably due to friction and deformation. So the cooling is necessary in the region of the die and tools. 相似文献
7.
Effects of coating thickness and residual stresses on the bond strength of ASTM C633-79 thermal spray coating test specimens 总被引:1,自引:0,他引:1
D. J. Greving J. R. Shadley E. F. Rybicki D. J. Greving J. R. Shadley E. F. Rybicki 《Journal of Thermal Spray Technology》1994,3(4):371-378
Wire-arc-sprayed nickel-aluminum is widely used in the aircraft industry for dimensional restoration of worn parts and as
a bond coat for thermal barrier coatings and other top coats. Some repair applications require thick coatings, which often
result in lower bond strength. A mechanism being investigated to ex-plain this decrease in bond strength is the free edge
effect, which includes both coating residual stresses and coating thickness. The layer-removal method was used to determine
experimentally the residual stresses in wire-arc-sprayed nickel-aluminum coatings of different thicknesses. Bond strength
evalu-ations were performed using an improved ASTM C 633-79 test specimen. Finite-element analysis and fracture mechanics
were used to investigate the effects of coating thickness and residual stress state on coating bond strength. 相似文献
8.
9.
Crystallographic analysis on small fatigue crack propagation behaviour of a nickel-based single crystal superalloy 下载免费PDF全文
W. Qiu X. Ma S. Rui H.-J. Shi 《Fatigue & Fracture of Engineering Materials & Structures》2017,40(1):3-11
In situ observations by scanning electron microscopy show that small fatigue cracks in a nickel-based single crystal superalloy are inclined to the loading direction and propagate in dominant crystallographic manners. In order to evaluate the driving forces for inclined crack propagation, three-dimensional anisotropic linear elastic finite-element analysis is conducted. The plastic zone size on the dominant slip plane has been calculated and proposed to correlate the fatigue crack growth. It is shown that this parameter takes into account both material anisotropy and octahedral fracture modes, and it can effectively characterize small crack propagation behaviour. 相似文献
10.
Allan P. Engsig-Karup Jan S. Hesthaven Harry B. Bingham Per A. Madsen 《Journal of Engineering Mathematics》2006,56(3):351-370
A discontinuous Galerkin finite-element method (DG-FEM) solution to a set of high-order Boussinesq-type equations for modelling
highly nonlinear and dispersive water waves in one horizontal dimension is presented. The continuous equations are discretized
using nodal polynomial basis functions of arbitrary order in space on each element of an unstructured computational domain.
A fourth-order explicit Runge-Kutta scheme is used to advance the solution in time. Methods for introducing artificial damping
to control mild nonlinear instabilities are also discussed. The accuracy and convergence of the model with both h (grid size) and p (order) refinement are confirmed for the linearized equations, and calculations are provided for two nonlinear test cases
in one horizontal dimension: harmonic generation over a submerged bar, and reflection of a steep solitary wave from a vertical
wall. Test cases for two horizontal dimensions will be considered in future work. 相似文献