Measurements of Forces and Temperature Fields in High-Speed Machining of 6061-T6 Aluminum Alloy

This study focuses on experimental modeling of dry high-speed machining at 30 m/s cutting velocity using 6061-T6 aluminum alloy. A modified Hopkinson bar apparatus is employed to simulate orthogonal machining, a focused array of mercury–cadmium–tellurium infrared detectors is used to measure the temperature distribution around the tool tip, and a three-component quartz force transducer is utilized in measuring the cutting and feed forces. The resulting measurements confirm the assumption of steady-state cutting and allow for estimation of the partition of cutting work into heating, shear, and momentum changes in the chip. In an earlier study, measurements of temperature distributions showed little heating of the finished surface. Therefore, a study of the temperature fields generated during machining with a cutting tool that has a wear-land was performed. The wear-land contributes significantly to the heating of the workpiece and, at this speed, is the most likely mechanism for the generation of residual stresses and a temperature rise on the finished surface.     

The impact of non-DLVO forces on the onset of shear thickening of concentrated electrically stabilized suspensions

This paper exposes an extension of an activation model previously published by the authors. When particles arranged along the compression axis of a sheared suspension, they may overcome the electrostatic repulsion and form force chains associated with shear thickening. A percolation-based consideration allows an estimation of the impact of the force chains on a flowing suspension. It suggests that similar to mode coupling models, the suspension becomes unstable before the critical stress evaluated from the activation model is reached. The percolated force chains lead to discontinuous shear thickening. The model predictions are compared with results from two experimental studies on aqueous suspensions of inorganic oxides; in one of them, hydration repulsion and in the other hydrophobic attraction can be expected. It is shown that the incorporation of non-Derjaguin–Landau–Verwey–Overbeek forces greatly improve predictions of the shear thickening instability.     

The cutting of soil by narrow blades

The available models for predicting the forces acting on a narrow soil cutting blade have required separate measurements of the shape of the three-dimensional soil failure pattern ahead of the blade. It is proposed that a three-dimensional model consisting of straight line failure patterns in the soil can be used to predict both the draft forces and the volume of soil disturbed in front of a narrow blade. Limit equilibrium mechanics equations are written for the soil wedges in terms of an unknown angle of the failure zone and the theoretical draft force is minimized with respect to this angle. Force factors are thus found which are of the type to fit Reece's general earthmoving equation, but which vary with the width to depth ratio of the blade as well as with the rake angle of the blade and the friction angle of the soil. In addition the approximate geometry of the three-dimensional failure pattern in the soil is predicted for varying blade shapes and soil strengths. This allows the design of simple tools on the basis of their draft force requirements and their soil cutting efficiency. The draft force predictions and failure geometry calculations are shown to have considerable verification by experimental results.     

Elastica of an euler rod with clamped ends

The stability of the postcritical states of equilibrium of a flexible rod with clamped ends loaded by an axial force is analyzed. It is shown that the existing Lagrange elliptic-integral solution has bifurcation points and branches of solution that have not been investigated thus far. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 3, pp. 184–186, May–June, 2000.     

In situ force-balance tensiometry

 Although a fundamental physical parameter, surface tension is difficult to measure. Common tensiometry inaccuracy comes from failure to control air–liquid–solid contact conditions, or account for liquid meniscus geometry and buoyancy corrections. This paper describes an in situ tensiometry technique, based on withdrawal of a thin-walled tube from the liquid interface, that enforces a known air–liquid–solid contact condition. This technique can be pursued at any level of experimental hygiene. Experimental results for filtered tap water, an alcohol–water solution, and a surfactant–water solution show that results repeatable to three significant digits are obtained with modest effort for a variety of geometrical parameters. Received: 7 October 1997/Accepted: 23 April 1998     

On the Range of Applicability of the Reissner–Mindlin and Kirchhoff–Love Plate Bending Models

We show that the Reissner–Mindlin plate bending model has a wider range of applicability than the Kirchhoff–Love model for the approximation of clamped linearly elastic plates. Under the assumption that the body force density is constant in the transverse direction, the Reissner–Mindlin model solution converges to the three-dimensional linear elasticity solution in the relative energy norm for the full range of surface loads. However, for loads with a significant transverse shear effect, the Kirchhoff–Love model fails. This revised version was published online in June 2006 with corrections to the Cover Date.     

Investigation of a turbulent boundary layer on a hypersonic aircraft model

An algorithm for calculation of a spatial compressible turbulent boundary layer on the surface of a pointed body is developed. The algorithm is based on the numerical solution of three-dimensional equations and algebraic models of turbulence. The flow around a hypersonic aircraft model is calculated, and the resultant Stanton numbers are compared with experimental data. The influence of the Mach number, the angle of attack, and the Reynolds number on the boundary-layer parameters is studied. It is shown that the change in the location of the transition zone has a weak effect on the skin-friction coefficient in the region of developed turbulent flow. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090.¹Technical University, Delft, the Netherlands. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 1, pp. 115–125, January–February, 1999.     

Series solution for large deflections of a cantilever beam with variable flexural rigidity

In this paper large deflection and rotation of a nonlinear Bernoulli-Euler beam with variable flexural rigidity and subjected to a static co-planar follower loading is studied. It is assumed that the angle of inclination of the force with respect to the deformed axis of the beam remains unchanged during deformation. The governing equation of this problem is solved analytically for the first time using a new kind of analytical technique for nonlinear problems, namely the Homotopy Analysis Method (HAM). The present solution can be used for the analysis of a wide range of loads, material/cross section properties and lengths for beams undergoing large deformations. The results obtained from HAM are compared with results reported in previous works. Finally, the load–displacement characteristics of a uniform cantilever beam with different material properties under a follower force applied normal to the deformed beam axis are presented.     

Compositive effects of orientation and contact angle on critical heat flux in pool boiling of water

An experimental study was carried out to investigate the effects of heat transfer surface orientation and the solid–liquid contact angle on the boiling heat transfer and critical heat flux (CHF) in water pool boiling using a smooth heat-transfer surface under atmospheric pressure. The orientation angle was ranged from 0° (up-facing horizontal position) to 180° (down-facing horizontal position) with a pace of 45°. The three kinds of heat transfer surfaces having different solid–liquid contact angles were the normal surface with a contact angle of 55°, the hydrophilic surface with a contact angle of 30° and the superhydrophilic surface with a contact angle of 0°. The experimental results indicate that orientation and contact angle have complex, coupling effects on heat transfer and CHF. A predicting correlation for the CHF which takes the effects of both orientation and contact angle into account is established. The predicting correlation agrees reasonably well with the experimental data.     

Three-dimensional motion of a viscous incompressible fluid in a narrow tube

An approximate solution of the problem of unsteady motion of a viscous incompressible fluid in a long narrow deformable tube at low Reynolds numbers is obtained. Pressure oscillations and tube deformation are shown to be related by an integrodifferential equation. The solution obtained extends the Poiseuille solution in elliptic tubes to the case of comparatively arbitrary small deformations in terms of the tube length and angle. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 4, pp. 28–32, July–August, 2009.     

The load distribution among three legs on the wall: model predictions for cockroaches

In a former study on terrestrial locomotion of cockroaches in the sagittal plane, it was hypothesised that the ground reaction force distribution among three legs synchronously in contact with a substrate is predominantly explained by joint torque minimisation within all three legs. We verified this hypothesis with a simple mechanical model in two dimensions, consisting of one body and three mass-less legs. Hereto, we calculated force distributions resulting from different optimisation criteria for varying slope angles of the substrate. We compared these distributions to each other and the few experimental findings available. We found that, for any slope angle, the force distribution rather seems to be derived from the fundamental “table” solution, i.e. equalised vertical and vanishing horizontal components (equivalent to pure force minimisation at zero slope), than from pure torque minimisation. For cockroaches, the “table” solution is likely to be modified by torque minimisation within the leading and the trailing leg. We demonstrate that the minimisation of leg forces and of interaction forces is fully equivalent. Moreover, our model predicts the force distribution for arbitrary slope angles. Based on our model calculations, we speculate that in terrestrial locomotion, some animals may rely on spring-mass model dynamics whatever slope angle to be overcome. This might only become evident when focusing movement analyses strictly on a gravity rather than on a substrate-based coordinate system.     

Effect of riblets on the drag of a body of revolution with trailing-edge flow separation

The results of measurements of the drag of axisymmetric bodies with smooth and ribbed central cylindrical sections and affinely similar trailing edges of various lengths are given. The experimental data were obtained for zero angle of attack and the numbers M=0.25–0.85 and Re=10⁷–2.4·10⁷ (calculated on the basis of the length of the body without the trailing section). The trailing-edge flow separation was visualized by the oil film method. It is shown that ribbing can lead to a decrease in drag due not only to a reduction in turbulent friction but also to reduction of the separation zone on the smooth trailing section of the body. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 163–168, January–February, 1998. The work was carried out with the support of the International Science-Technology Center (project No. 199-95).     

Bore impact on a vertical plate

This paper describes the technique and results of an experimental study of the longitudinal force component, the vertical coordinate of its application point, and the overturning moment for the impact of a bore on a vertical plate. The bore was generated by removal of a shield which produced the initial free-surface level difference in the channel (in the model formulation of the dam-break problem). It is shown that the greatest forces and overturning moments occur at the ratio of the initial headwater and tailwater levels at which a bore with a developed head roller is formed. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 6, pp. 45–54, November–December, 2008.     

Elastic–plastic contact force history and response characteristics of circular plate subjected to impact by a projectile

A new elastic–plastic impact–contact model is proposed in this paper. By adopting the principle of minimum acceleration for elastic–plastic continue at finite deformation, and with the aid of finite difference method, the proposed model is applied in the problem of dynamic response of a clamped thin circular plate subjected to a projectile impact centrally. The impact force history and response characteristics of the target plate is studied in detail. The theoretical predictions of the impact force and plate deflection are in good agreements with those of LDA experimental data. Linear expressions of the maximum impact force/transverse deflection versus impact velocity are given on the basis of the theoretical results. The project supported by the National Natural Science Foundation of China (10532020).     

Time-dependent thermoelastic creep analysis of rotating disk made of Al–SiC composite

Time-dependent creep stress redistribution analysis of rotating disk made of Al–SiC composite is investigated using Mendelson’s method of successive elastic solution. All mechanical and thermal properties except Poisson’s ratio are radial dependent based on volume fraction percent of SiC reinforcement. The material creep behavior is described by Sherby’s constitutive model using Pandey’s experimental results on Al–SiC composite. Loading is an inertia body force due to rotation and a distributed temperature field due to steady-state heat conduction from inner to outer surface of the disk. Using equations of equilibrium, stress strain, and strain displacement, a differential equation, containing creep strains, for displacement is obtained. History of stresses and deformations are calculated using method of successive elastic solution. It is concluded that the uniform distribution of SiC reinforcement does not considerably influence on stresses. However, the minimum and most uniform distribution of circumferential and effective thermoelastic stresses belongs to composite disk of aluminum with 0% SiC at inner surface and 40% SiC at outer surface. It has also been found that the stresses, displacement, and creep strains are changing with time at a decreasing rate so that after almost 50 years the solution approaches the steady-state condition.     

On a gas source in a constant force field

The nonbarochronic regular partially invariant submodel of the equations of gas dynamics is studied. The submodel reduces to an implicit ordinary differential equation of the first order for an auxiliary function X = X(x). The physical quantities (velocity, density, and pressure) are expressed in terms of the function X. The properties of the solutions of the equation are investigated and interpreted physically in terms of gas motion. The existence of a shock-wave solution is proved. The properties of the shock adiabat are studied. It is shown that the results obtained are new and differ significantly from the results for the case of no constant force. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 6, pp. 3–16, November–December, 2006.     

Effect of asymmetric pulsed periodic energy supply on aerodynamic characteristics of airfoils

The possibility of controlling the aerodynamic characteristics of airfoils in transonic flight regimes by means of local pulsed periodic energy supply is considered. The numerical solution of two-dimensional unsteady equations of gas dynamics allowed determining the changes in the flow structure near a symmetric airfoil and its aerodynamic characteristics depending on the magnitude of energy in the case of its asymmetric (with respect to the airfoil) supply. The results obtained are compared with the calculated data for the flow around the airfoil at different angles of attack without energy supply. With the use of energy supply, a prescribed lift force can be obtained with a substantially lower wave drag of the airfoil, as compared with the flow around the airfoil at an angle of attack. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 70–76, November–December, 2007.     

Effect of one-sided unsteady energy supply on aerodynamic characteristics of airfoils in a transonic flow

The possibility of controlling the aerodynamic characteristics of airfoils in transonic flight regimes by means of one-sided pulsed-periodic energy supply is studied. Based on the numerical solution of two-dimensional unsteady gas-dynamic equations, the change in the flow structure in the vicinity of a symmetric airfoil at different angles of attack and the aerodynamic characteristics of the airfoil as functions of the amount of energy supplied asymmetrically (with respect to the airfoil) are determined. The results obtained are compared with the data calculated for the flow past the airfoil at different angles of attack without energy supply. It is found that a given lift force can be obtained with the use of energy supply at a much better lift-to-drag ratio of the airfoil, as compared to the case of the flow past the airfoil at an angle of attack. The moment characteristics of the airfoil are found. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 6, pp. 82–87, November–December, 2008.     

Vortex diffraction on a swept wing

The forces acting on a swept wing in the presence of a vortex induced by a delta wing, as well as the velocity field in the vicinity of the swept wing, have been measured. By means of the “frozen,” vortex model and a specially-developed numerical panel method, the forces and moments acting on the wing are calculated from the known velocity field. Comparison of the calculated and measured force characteristics makes it possible to determine the extent to which the model fits the physical flow pattern. It is shown that for the intense vortex considered in this study the model gives results which disagree sharply with the experimental data. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, pp. 98–105, November–December, 1998. The study was supported by the International Scientific and Technical Center under grant No. 201.