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111.
In this study plate-impact pressure-shear friction experiments are employed to investigate dynamic slip resistance and time-resolved growth of molten metal films during dry metal-on-metal slip under extreme interfacial conditions. By employing a tribo-pair comprising of a hard tool-steel against a relatively low melt-point metal (7075-T6 Al alloy), interfacial normal stress of up to 5 GPa and slip speeds of approximately 250 m/s have been achieved. These extreme interfacial conditions are conducive to the development of molten metal film at the tribo-pair interface. A Lagrangian finite element code is developed to understand the evolution of the thermo-mechanical fields and their relationship to the observed slip response. The code accounts for dynamic effects, heat conduction, contact with friction, and full thermo-mechanical coupling. At temperatures below the melting point of the tribo-pair materials are described as isotropic, thermally softening, elastic–viscoplastic solids. For material elements with temperatures in excess of the melt temperature a purely Newtonian fluid constitutive model is employed. 相似文献
112.
The theory of Tuncay and Corapcioglu (Transp Porous Media 23:237–258, 1996a) has been employed to investigate the possibility
of plane wave propagation in a fractured porous medium containing two immiscible fluids. Solid phase of the porous medium
is assumed to be linearly elastic, isotropic and the fractures are assumed to be distributed isotropically throughout the
medium. It has been shown that there can exist four compressional waves and one rotational wave. The phase speeds of these
waves are found to be affected by the presence of fractures, in general. Of the four compressional waves, one arises due to
the presence of fractures in the medium and the remaining three are those encountered by Tuncay and Corapcioglu (J Appl Mech
64:313–319, 1997). Reflection and transmission phenomena at a plane interface between a uniform elastic half-space and a fractured
porous half-space containing two immiscible fluids, are analyzed due to incidence of plane longitudinal/transverse wave from
uniform elastic half-space. Variation of modulus of amplitude and energy ratios with the angle of incidence are computed numerically
by taking the elastic half-space as granite and the fractured porous half-space as sandstone material containing non-viscous
wetting and non-wetting fluid phases. The results obtained in case of porous half-space with fractures, are compared graphically
with those in case of porous half-space without fractures. It is found that the presence of fractures in the porous half-space
do affect the reflection/transmission of waves, which is responsible for raising the reflection and lowering the transmission
coefficients. 相似文献
113.
S. Mukherjee A. Sharma S. Sodaye B.S. Tomar A. Goswami S.B. Manohar 《The European Physical Journal A - Hadrons and Nuclei》2001,12(2):199-205
Incomplete fusion reactions were investigated by measuring the excitation functions of nine evaporation residues in 16O + 51V reaction in the beam energy 4-6 MeV/amu, using the well-known recoil catcher technique and gamma-ray spectrometry. The experimental
data were compared with that obtained from Monte Carlo simulation calculations using the PACE2 code. The results indicate
the presence of incomplete fusion process in the production of two alpha emission products. This was further confirmed by
the measurement of recoil range distribution of these isotopes at 96 MeV beam energy. Calculations of the average angular
momentum associated with these products revealed the peripheral nature of these ICF reactions.
Received: 20 June 2001 / Accepted: 11 September 2001 相似文献
114.
In this paper, the extended Lagrangian formulation for a one-dimensional continuous system with gyroscopic coupling and non-conservative fields has been developed. Using this formulation, the dynamics of an internally and externally damped rotor driven through a dissipative coupling has been studied. The invariance of the extended or so-called umbra-Lagrangian density is obtained through an extension of Noether’s theorem. The rotor shaft is modeled as a Rayleigh beam. The dynamic behavior of the rotor shaft is obtained and validated through simulation studies. Results show an interesting phenomenon of limiting behavior of the rotor shaft with internal damping beyond certain threshold speeds which are obtained theoretically and affirmed by simulations. It is further observed that there is entrainment of whirling speeds at natural frequencies of the rotor shaft primarily depending on the damping ratio. 相似文献
115.
The possibility of plane wave propagation in a micropolar fluid of infinite extent has been explored. The reflection and transmission of longitudinal elastic wave at a plane interface between a homogeneous micropolar fluid half-space and a micropolar solid half-space has also been investigated. It is found that there can exist four plane waves propagating with distinct phase speeds in an infinite micropolar fluid. All the four waves are found to be dispersive and attenuated. The reflection and transmission coefficients are found to be the functions of the angle of incidence, the elastic properties of the half-spaces and the frequency of the incident wave. The expressions of energy ratios have also been obtained in explicit form. Frequency equation for the Stoneley wave at micropolar solid/fluid interface has also been derived in the form of sixth-order determinantal expression, which is found in full agreement with the corresponding result of inviscid liquid/elastic solid interface. Numerical computations have been performed for a specific model. The dispersion curves and attenuation of the existed waves in micropolar fluid have been computed and depicted graphically. The variations of various amplitudes and energy ratios are also shown against the angle of incidence. Results of some earlier workers have been deduced from the present formulation. 相似文献
116.
The knowledge of shear resistance in earth faults is of fundamental importance to our understanding of the magnitude of stress drop and the associated energy release during typical seismic rupture events. In the present study a modified torsional Kolsky bar is employed to investigate frictional slip resistance in rock-analog materials (i.e., quartz and soda lime glass) at normal stresses of relevance to earthquake physics (30–80 MPa) and co-seismic slip rates. The results indicate the coefficient of kinetic friction to be in the range of 0.2 to 0.3. These values of the coefficient of friction are much lower when compared to those obtained in rocks at quasi-static slip rates. In all experiments slip weakening is observed and is preceded by slip strengthening. The slip weakening is understood to be due to thermal weakening induced by flash-heating at asperity contacts and requires a few mm of slip to be effective; the slip strengthening is understood to be due to an increase in the real area of contact at the asperity junctions due to localized plastic flow and subsequent coalescence and solidification of local softened/melt patches at the slip interface. 相似文献
117.
An analysis is presented of the effect of a constant thermal gradient on coupled vibrations of a beam of linearly varying semi-circular cross-section attached to a rotating disc. A method based on Rayleigh's quotient is used to obtain upper bounds of the frequencies corresponding to the first three modes of vibrations. The frequencies for various values of cross-section variation, hub-radius and temperature gradient are obtained. 相似文献
118.
B. S. Tomar A. Goswami A. V. R. Reddy S. K. Das P. P. Burte S. B. Manohar Satya Prakash 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(2):223-227
Excitation functions for the evaporation residues for the reactions12C+93Nb and16O+89Y in the projectile energy range of 4 to 6.5 MeV/amu have been measured using off-line gamma spectrometry. The excitation functions for neutron(xn), proton(pxn) and one alpha(xn) emission channels are practically similar for both the reactions. However the products formed by two alpha(2xn) emission show much higher cross sections in the12C+93Nb than the16O+89Y system. This has been explained in terms of the incomplete fusion process involving transfer of an alpha particle from the projectile to the target in the former case.Authors thank Shri D.C. Ephraim for making the rolled metal foils and the operation crew of PELLETRON facility for their help in carrying out the irradiations. Authors are grateful to Dr. P.R. Natarajan, Head Radiochemistry Division for his keen interest in this work. 相似文献
119.
A. Goswami S. B. Manohar S. K. Das A. V. R. Reddy B. S. Tomar S. Prakash 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(3):299-301
Mass resolved fission fragment angular distribution was measured in the 28.5 MeV alpha induced fission of233U using recoil catcher technique and direct gamma spectrometry. The angular distribution of 8 fission products were obtained. The angular anisotropies of asymmetric fission products were found to be higher than those of symmetric products indicating a correlation between the fragment angular distribution and the mass distribution.The authors are grateful to Dr. S.K. Kataria and Dr. T. Datta for fruitful discussions. We thank the operation crew of the variable energy cyclotron, Calcutta for their help in carrying out the irradiations. Thanks are due to Dr. P.R. Natarajan, Head of the Radiochemistry Division for his keen interest in the work. 相似文献
120.
S. Kumar N. Rawat A. S. Kanekar B. S. Tomar V. K. Manchanda M. S. Sonavane N. L. Sonar K. Raj 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(2):225-228
Diffusion of sodium in Mn and Ti bearing sodium borosilicate glass used for the immobilization of the high level waste at
the Waste Immobilization Plant, Tarapur has been studied by heterogeneous isotopic exchange using 24Na as the radiotracer for sodium. The temperature dependence of the self-diffusion coefficient of sodium in the glass was
found to follow Arrhenius equation below the glass transition temperature. 相似文献