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1
Content available remote Principles of the Through-Air Dewatering Theory for Selected Fibrous Materials (Press Section Felts)
Kawka W.
Fibres & Textiles in Eastern Europe
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2009
|
Vol. 17, no. 3 (74)
95--97
EN
The conditioning process of press felts is a very important operation to intensify the dewatering process of the paper web in the press section of a paper machine. A new method of conditioning press felts by means of airflow, which is more efficient in the dewatering and cleaning processes of felts, is presented. Calculation methods for the dewatering efficiency of press felts and the air demand of the airflow are based on Darcy’s modified formula . A few methods for the determination of empirical coefficients have been suggested. The through-air dewatering of press section felts is especially advantageous for modern felts made entirely of synthetic fibres.
PL
Proces odwadniania mokrej wstęgi papieru w prasach przebiega tylko wówczas gdy wilgotność i przepuszczalność filców są utrzymywane na stałym poziomie. Do tego celu służą urządzenia do kondycjonowania filców jak np. przedmuchowe pralki filców. Przedstawiono model matematyczny procesu odwadniania filców prasowych. W którym bardzo ważnym parametrem jest współczynnik filtracji wody przez filc. Współczynnik ten powinien być wyznaczany w warunkach dynamicznych. W celu określenia jego wartości opracowano program i wykonano badania na doświadczalnej prasie. Badano filc igłowany z włókien syntetycznych. Określono wartości współczynnika filtracji wody przez filc w warunkach statycznych i dynamicznych. Ustalono że wartości tych współczynników są różne, ale zachodzi między nimi zależność liniowa. W oparciu o podane wzory można obliczyć objętościowe natężenie przepływu wody wypychanej z filcu przez strumień powietrza a w konsekwencji wilgotność filcu po jego kondycjonowaniu.
2
Content available remote Effect of end-shortening on the response of a steel cantilever beam with an opening
Rahman M. A., Kowser M. A., Siddiqui M. T.
International Journal of Applied Mechanics and Engineering
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2008
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Vol. 13, no 3
735-751
EN
This study is a continuation of our previous study that comprehensively dealt with the response of a slender cantilever beam with an opening of different geometry (circular, elliptical and square, respectively), having the same cross-sectional area, placed at different positions of the beam's span. The effect of end-shortening that becomes important at a high load is included in the present analysis. Obviously, stresses in these beams increase significantly due to the opening. Based on numerical calculations considering geometric nonlinearity and the effect of end shortening, it is found however, that the maximum values of the stresses are actually much smaller than their predictions are by linear theory without considering end-shortening. These stresses remain well below the proportional limit of highly elastic steel. Further, a similar analysis was performed for the case of a cantilever beam of a constant cross-section. It is found that the nonlinear analysis with end-shortening is much more important for a beam with an opening than it is for a beam of a constant cross-section. Though the topic chosen for this paper corresponds to a highly nonlinear boundary value problem, the numerical simulation scheme devised is sound enough to predict the response of the variable cross-section beams with high accuracy. Experimental results obtained by another research group have been compared by simulation; a very good agreement proves the soundness of the present numerical simulation scheme.
3
Content available remote Wave propagation in a micropolar elastic layer sandwiched between liquid haIf-space and mnicropolar solid half-space
Tomar S. K.
International Journal of Applied Mechanics and Engineering
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2007
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Vol. 12, no 1
255-262
EN
A problem of surface waves in a layer of micropolar elastic material overlying a micropolar elastic haIf-space and underlying a liquid haIf-space is studied. The frequency equation is derived, and then solved numerically for particular models. Numerical results show that there exist infinite numbers of modes of propagation. It is found that the surface waves are dispersive for all modes of propagation except the lowest one, which is almost non-dispersive. The numericaI results obtained are presented graphicaIly.
4
Content available remote Thermoelastic interactions without energy dissipation due to various sources
Kumar R., Rani L.
International Journal of Applied Mechanics and Engineering
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2007
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Vol. 12, no 2
431-446
EN
The linear theory of thermoelasticity without energy dissipation is employed to investigate the disturbance due to mechanical (horizontal or vertical) and thermal source in a homogeneous, thermoelasic half-space. Laplace-Fourier transforms are applied to the basic equations to form a vector matrix differential equation, which is then solved by using the eigenvalue approach. The displacements, stresses and temperature distribution so obtained in the physical domain are computed numerically and ilIustrated graphically for a magnesium-like material for an insulated boundary and temperature gradient boundary, respectively.
5
Content available remote Propagatlon of Rayleigh-Lamb waves in thermomicrostretch elastic plates
Pathania D. S., Sharma J. N., Kumar R.
International Journal of Applied Mechanics and Engineering
|
2007
|
Vol. 12, no 4
1147-1163
EN
The propagation of waves in a thermo-microstretch elastic plate subjected to stress free isothermal and thermally insulated conditions is investigated in the context of the conventional coupled thermoelasticity (CT), Lord-Shulman (LS), and Green-Lindsay (GL) theories of thermoelasticity. The secular equations for the thermomicrostretch elastic plate in a closed form and isolated mathematical conditions for the symmetric and skewsymmetric wave mode propagation in completely separate terms are derived. The secular equations for the thermo-microstretch elastic plate, coupled thermoelastic, micropolar elastic, thermoelastic and elastic plates have been deduced as particular cases from the secular equations derived. At short wave length limits, the secular equations for the symmetric and skew symmetric waves in stresses free, thermally insulated and isothermal, thermo-microstretch elastic plate reduce to the Rayleigh surface wave's frequency equation. Finally, in order to illustrate the analytical development, the numerical solution is carried out for aluminum-epoxy composite material. The symmetric and skew symmetric wave modes are computed numerically and presented graphically. The theory and numerical computations are found to be in close agreement.
6
Content available remote Propagation of generalized thermoelastic pIane waves at an imperfect interface
Kumar R., Singh M.
International Journal of Applied Mechanics and Engineering
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2007
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Vol. 12, no 3
713-732
EN
The present study is concerned with the reflection and transmission of thermoelastic pIane waves at an imperfect interface between two generalized thermoelastic solid half-spaces of different elastic and thermal properties. The generalized thermoelastic theory with one relaxation time developed by Lord and Shulman (1967) has been used to study the problem. The expressions for the reflection and transmission coefficients which are the ratios of the amplitudes of reflected and transmitted waves to the amplitude of incident waves are obtained for an imperfect boundary and deduced for normal stiffness, transverse stiffness, thermal contact conduetance, slip and welded boundaries. The amplitude ratios of various reflected and transmitted waves are also deduced at the interface of two semi-infinite media (I) Elastic/Generalized Thermoelastic and (II) Elastic/Elastic. The special case of stress free thermally insulated boundary has also been discussed. It is found that the amplitude ratios of reflected and transmitted waves are affected by the stiffness and thermal properties of the media.
7
Content available remote Large deflection anaIysis of cantilever beams with an opening
Rahman M. A., Rahman M. S., Hossain A. H. M.
International Journal of Applied Mechanics and Engineering
|
2007
|
Vol. 12, no 1
169-181
EN
Numerical solutions have been obtained for analyzing the elastic dellection and stresses of a cantilever beam with a variable cross-sectional area. The variable cross-section was due to a circular, an elliptical and a square openinglhole/slot having the same cross- sectional area placed at different positions of the beam's span. An extensive numerical simulation was carried out using both the smali and large dellection theories to calculate the stresses and the deflections of the same beam. A computer code in "C" has been developed using the Runge-Kutta technique for the purpose of simulation. The position of the opening over the beam's span is found to have significant effect on the beam's response under a tip load. Results show the linear theory fails to account for the change in curvature at high intensity loadings and underestimates the dellections. If same amount of material is removed considering different cross-sectional area (square, circle and ellipse), it is found that the maximum dellection is developed for the circular holes and the square slots. while the circular holes cause to develop the maximum stress. The discrepancy between the linear and nonlinear solutions is the maximum if the hollow section is near the fixed end. Among the three types of openings, the elliptic slots develop the minimum stress and tip dellections.
8
Content available remote Axi-symmetric problem in a micropolar generalized thermoelastic half-space
Kumar R., Deswal S.
International Journal of Applied Mechanics and Engineering
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2007
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Vol. 12, no 2
413-429
EN
The disturbance due to mechanical and thermal sources in a homogeneous isotropic micropolar generalized thermoelastic half space is investigated by the use of Laplace-Hankel transform techniques. The integral transforms are inverted by using a numerical technique. The displacement components, temperature field, normal and tangential stresses are obtained in the physical domain for Lord-Shulman (L-S), Green-Lindsay (G-L) and Green-Naghdi (G-N) theońes of micropolar generalized thermoelasticity and are shown graphically for magnesium crystal like material.
9
Content available remote Plane SH-wave response from elastic slab interposed between two different self-reinforced elastic solids
Chaudhary S., Kaushik V. P., Tomar S. K.
International Journal of Applied Mechanics and Engineering
|
2006
|
Vol. 11, no 4
787-801
EN
Closed form expressions of reflection and transmission coefficients are obtained when a plane SH-wave becomes incident at a uniform elastic layer interposed between two different self-reinforced elastic solid half-spaces. It is found that the reflection and transmission coefficients are strongly influenced by the reinforcement parameters of the half-spaces. Numerical computations are performed for a specific model to study the effect of reinforcement parameters and angle of incidence of the incident wave on these coefficients. Numerical study reveals that both reflection and transmission coefficients are significantly influenced by the reinforcement parameters in the entire range of angle of incidence, except at normal and grazing incidence where the effect of reinforcement parameters is found minimum. Known results of some earlier workers are reduced from the present formulations.
10
Content available remote On plane waves in an isotropic linear thermoelastic solid with initial stresses
Singh B.
International Journal of Applied Mechanics and Engineering
|
2006
|
Vol. 11, no 4
957-963
EN
The plane wave propagation in a homogenous isotropic, thermally conducting elastic solid under normal initial stresses is studied with two thermal relaxation times. Three types of plane waves, quasi-P, thermal and quasi-SV waves, are shown to exist. The dependence of the velocities of these plane waves on the direction of propagation is shown graphically for different combinations of normal initial stresses.
11
Content available remote Interaction due to mechanical sources in micropolar cubic crystal
Kumar R., Ailawalia P.
International Journal of Applied Mechanics and Engineering
|
2006
|
Vol. 11, no 2
337-357
EN
The response of a micropolar cubic crystal due to various sources has been investigated. The eigen-value approach after applying Laplace and Fourier transforms has been employed to solve the problem. The integral transforms have been inverted by using a numerical technique to obtain the displacement, microrotation and stress components in the physical domain. The results of normal displacement, normal force stress and tangential couple stress have been compared for a micropolar cubic crystal and micropolar isotropic solid and illustrated graphically.
12
Content available remote Free transverse vibrations of monoclinic rectangular plates with continuously varying thickness and density
Kumar Y., Tomar S. K.
International Journal of Applied Mechanics and Engineering
|
2006
|
Vol. 11, no 4
881-900
EN
Free transverse vibrations of a rectangular plate composed of a monoclinic elastic material are discussed. The plate is considered to be exponentially varying in density and thickness along one direction of the plate. Hamilton's principle is used to derive the equation of motion and its solution is obtained using Chebyshev collocation technique. Frequency equations are derived for three boundary value problems when two edges of the plate are simply supported and the other two have different possibilities, namely (i) C - S - C - S (ii) C - S - S - S (iii) C - S - F - S, where C, S and F denote the clamped, simply supported and free edge respectively. Effects of thickness and density variation on modes of vibrations have been analyzed. Numerical computations have been performed for a specific model of monoclinic plates and the results obtained are compared with those for orthotropic plates already given in Lal (2003).
13
Content available remote Effect of compressibility and suspended particles on thermal convection in a Walters' B' elastico-viscous fluid in hydromagnetics
Sharma R. C., Aggarwal A. K.
International Journal of Applied Mechanics and Engineering
|
2006
|
Vol. 11, no 2
391-399
EN
A layer of a compressible, electrically conducting Walters' B' elastico-viscous fluid permeated with suspended particles heated from below in the presence of a magnetic field is considered. For the case of stationary convection, the Walters'(model B') elastico-viscous fluid behaves like a Newtonian fluid and the compressibility, magnetic field are found to have stabilizing effects, whereas the suspended particles have a destabilizing effect on the thermal convection. The presence of each - viscoelasticity, magnetic field and suspended particles introduces oscillatory modes in the system which were non-existent in their absence.
14
Content available remote Dynamic analysis of ball bearings with effect of preload and number of balls
Purohit R. K., Purohit K.
International Journal of Applied Mechanics and Engineering
|
2006
|
Vol. 11, no 1
77-91
EN
In this paper, the radial and axial vibrations of rigid shaft supported ball bearings are studied. In the analytical formulation the contacts between the balls and the races are considered as nonlinear springs, whose stiffness are obtained by using the Hertzian elastic contact deformation theory. The implicit type numerical integration technique Newmark- with Newton-Raphson method is used to solve the nonlinear differential equations iteratively. The effect on vibrations of varying preload and the number of balls in the bearings is investigated for prefect bearings. For perfect bearings, vibrations occur at the ball passage frequency. The amplitudes of these vibrations are shown to be considerably reduced if the preload and number of balls are correctly selected. All results are presented in the form of Fast Fourier Transformations (FFT).
15
Content available remote Deformations due to mechanical sources in elastic solid with voids
Kumar R., Ailawalia P.
International Journal of Applied Mechanics and Engineering
|
2006
|
Vol. 11, no 4
865-880
EN
Void effects of a load applied normal to the boundary and moving at a constant velocity along one of the coordinate axis in an elastic half space is studied. The analytic expressions for displacement, force stress and volume fraction field for concentrated normal point force, uniformly distributed force, linearly distributed force and moving concentrated normal force are obtained by employing the eigen value approach after applying the integral transforms. A numerical inversion technique has been applied to obtain the solution in the physical domain. The numerical results are presented graphically. Some particular cases have been deduced.
16
Content available remote Deformation due to moving loads in thermoelastic body with voids
Kumar R., Rani L.
International Journal of Applied Mechanics and Engineering
|
2006
|
Vol. 11, no 1
37-59
EN
The voids effect of loads which are moving at a constant velocity along one of the coordinate axis in a generalized thermoelastic half-space is studied. The analytical expressions of the displacements, stresses, temperature distribution and change in the volume fraction field for two different theories, i.e., Lord-Shulman (L-S), Green-Lindsay (G-L) are obtained by the use of the Fourier transform technique. The integral transform has been inverted by using a numerical technique and numerical results are illustrated graphically for a magnesium crystal-like material for the insulated boundary and temperature gradient boundary.
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