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991.
Summary If the roots of the characteristic equation of the governing differential equation for the stress function of an orthotropic plate under generalized plane stress conditions are equal classical solutions of anisotropic elasticity theory do not hold anymore. The general form of the stress function for such orthotropic materials is discussed and the exact solution is given for the plate with an elliptic opening loaded in tension.Comparison of the stress distribution for the material with distinct characteristic roots indicated that in produces much higher stress concentrations than the model with equal roots. For the latter case solution of any boundary value problem may be obtained very easily through an existing solution for the isotropic material.Given also that there are several problems involving stress concentrations in orthotropic plates as yet unsolved, the analysis presented here might be of considerable help in the, designing of the structure of composite laminates.With 8 Figures 相似文献
992.
S. A. Bengelloun 《Acta Informatica》1986,23(2):119-125
Summary A new algorithm is presented for finding all primes between 2 and an incrementally increasing value n. The algorithm executes in linear arithmetic time and space. An outline is given to show how previously developed techniques can be applied to improve the efficiency of the algorithm to O(n/loglogn) time and space. 相似文献
993.
P. K. Yeung S. C. Kot 《International journal for numerical methods in engineering》1985,21(5):929-939
A body-fitted curvilinear co-ordinate system is used to solve the equations of two-dimensional incompressible laminar flow over bluff obstructions by finite differences. Arbitrary conditions at the corner are removed by this method. Results for a backward-facing step are in reasonable agreement with those obtained with conventional mesh systems, and the differences are explained. A treatment of a channel expansion, in comparison with empirical data, is also included. The capability of the present method to handle arbitrary two-dimensional geometries is stressed and demonstrated, using a triangle and a semi-circle as examples. 相似文献
994.
Static light scattering was used to investigate dilute dispersions of fine gamma -Fe/sub 2/O/sub 3/ magnetic particles. The particles were acicular and on average 0.39 mu m long and 0.056 mu m in diameter. They were dispersed in organic solvents at concentrations of approximately 10/sup -4/ vol%, corresponding to an average interparticle separation of 9 mu m. Computer programs using a coupled dipole algorithm to predict the scattering from the particles were written. Experimental results do not agree with computer calculations of the light scattering from single particles, but are consistent with scattering from thick ropelike agglomerates of particles. The size of these agglomerates was estimated after 10 s to be less than 100 particles, while the thickness of the ropes is at least 5 particles.<> 相似文献
995.
Y. Nath P. C. Dumir R. S. Bhatiaf 《International journal for numerical methods in engineering》1985,21(3):565-578
The present work investigates the efficacy and applicability of interior global orthogonal point collocation method to the axisymmetric nonlinear analysis of elastic circular plates and shallow spherical shells subjected to uniformly distributed transverse load. Spacewise discretisation has been carried out using a polynomial expansion with the zeros of a Chebyshev polynomial as collocation points. Timewise integration has been carried out with Newmark k-β scheme corresponding to average acceleration method. The static response and snap-through buckling results, as well as, the dynamic response and dynamic buckling results under a uniformly distributed step load have been obtained and found to agree closely with the available results. 相似文献
996.
C. Y. Liao S. N. Atluri 《International journal for numerical methods in engineering》1991,32(6):1339-1361
An efficient method, based on the Schwarz–Neumann alternating technique, is presented for computing weight functions of a general solid (3-D as well as 2-D), with embedded or surface-flaw configurations. The total rate of change of the crack-opening displacements, due to simple perturbations of crack-dimension characteristics, is conveniently decomposed into the infinite-domain and boundary-correction parts. The former is determined from available analytical solutions of ideal-shaped cracks, whereas the latter is computed numerically by imposing nil boundary-traction requirements for the displacement field corresponding to the weight functions. Numerical examples, with solutions for 3-D weighted-average and local stress intensity factors, indicate that the proposed method is very accurate and efficient. 相似文献
997.
On the basis of the results of measurements in the pressure range 3.5–11 GPa for the shear strength of a number of shock-compressed substances carried out taking account of the completion of relaxation processes and establishment of pressure equilibrium the divergence is explained in results published previously for measurements of the dynamic yield point for highly ductile metals of the lead and tin type.Translated from Problemy Prochnosti, No. 10, pp. 50–54, October, 1991. 相似文献
998.
999.
V. Vassilev S. Thijs P. L. Segura P. Wambacq P. Leroux G. Groeseneken M. I. Natarajan H. E. Maes M. Steyaert 《Microelectronics Reliability》2005,45(2):255-268
This paper describes an approach to design ESD protection for integrated low noise amplifier (LNA) circuits used in narrowband transceiver front-ends. The RF constraints on the implementation of ESD protection devices are relaxed by co-designing the RF and the ESD blocks, considering them as one single circuit to optimise. The method is applied for the design of 0.25 μm CMOS LNA. Circuit protection levels higher than 3 kV HBM stress are achieved using conventional highly capacitive ggNMOS snapback devices. The methodology can be extended to other RF-CMOS circuits requiring ESD protection by merging the ESD devices in the functionality of the corresponding matching blocks. 相似文献
1000.
The effects of fluidized bed heat treatment on the microstructural and mechanical properties of Al-Si-Cu-Mg cast alloys, namely,
354 and 319, were studied. The heating rate in fluidized beds (FBs) is greatervis-à-vis conventional electrical resistance furnaces (CFs). The high heating rate in FBs increases the kinetics of metallurgical phenomena
such as Si fragmentation and spherodization during solution heat treatment, as well as the precipitation rate of phases such
as Al5Cu2Mg8Si6 and Al2Cu during aging. It is observed that the dissolution rate of phases such as Mg2Si and Al5Cu2Mg8Si6 takes place very rapidly. The solution heat treatment of 319 alloy using FB results in complete dissolution of Mg2Si and Al5Cu2Mg8Si6 particles within 45 minutes. However, for phases such as Al2Cu and Ferich intermetallics, the dissolution rate is relatively slow. Even on prolonged solution heat treatment for 6 hours,
these phases do not dissolve completely. It is observed that incomplete dissolution of the Al2Cu phase does not significantly affect tensile properties of T4-treated alloys. The optimum solution heat-treatment time in
FB for both 354 and 319 alloys is 45 minutes at 527 °C and 493 °C, respectively. Thermal analysis shows an exothermic peak
owing to recrystallization and coarsening of eutectic grains during solution heat treatment. The high heating rate in FB causes
this transformation to take place at a lower temperature than in CF. It is observed that the nucleation rate of Al5Cu2Mg8Si6 during aging in FB is greater than using CF. Thermal analysis of samples during the ramp-up stage while aging using FB did
not show any phase transformation, while those using CF show two endothermic transformations, which are most likely due to
the dissolution of GP zones or the co-cluster of solutes. Aging at 200 °C results in a greater number density of precipitates
than those at 240 °C. The tensile strength of samples aged at 200 °C is greater than those aged at 240 °C, because the amount
of precipitates formed at 200 °C is greater than that at 240 °C. The total heat-treatment time for T6 temper is less than
2 hours in FBs, which is a significant reduction in heat-treatment time, as well as energy consumption. 相似文献