How to predict soil compaction from agricultural tires

A concept of how to predict soil compaction with regard to agricultural machinery, tires and soil is proposed. This approach should provide criteria for choosing vehicles and tires, as well as for the choice of soil testing equipment. It should be stressed that, till now, the concept has only been tested for a few kinds of soil. Therefore, its application to other soil types has to start with one of the proposed “soil calibration tests”.     

An indoor traction measurement system for agricultural tires

To reliably study soil–wheel interactions, an indoor traction measurement system that allows creation of controlled soil conditions was developed. This system consisted of: (i) single wheel tester (SWT); (ii) mixing-and-compaction device (MCD) for soil preparation; (iii) soil bin; (iv) traction load device (TLD). The tire driving torque, drawbar pull, tire sinkage, position of tire lug, travel distance of the SWT and tire revolution angle were measured. It was observed that these measurements were highly reproducible under all experimental conditions. Also relationships of slip vs. sinkage and drawbar pull vs. slip showed high correlation. The tire driving torque was found to be directly influenced by the tire lug spacing. The effect of tire lug was also discussed in terms of tire slip.     

On the dynamic behavior of an elastoplastic oscillator

Summary We describe an experimental research on the behavior of an elastoplastic oscillator with one degree of freedom and we point out some differences with respect to the results of studies on a bilinear isteretical model. Therefore a mechanical scheme of an elastoplastic oscillator endowed with a continuous skeleton intrinsec curve is studied and the results of the theory agree with the experimental ones.

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Sommario Si descrivono le esperienze condotte su un oscillatore elastoplastico a un grado di libertà. Si mettono in evidenza alcune differenze del comportamento reale con le risultanze teoriche, queste vengono spiegate attraverso lo studio di un modello teorico elastoplastico con caratteristica intrinseca curvilinea anzichè bilineare.

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The present investigation has been promoted and financed by the Consiglio Nazionale delle Ricerche (C.N.R.) at the Istituto di Scienza e Tecnica delle Costruzioni del Politecnico di Milano.     

On the dynamic behavior of gas bubbles in an inhomogeneous standing wave

The motion of gas bubbles in an inhomogeneous standing wave is examined. The nonlinear system of equations is solved by the averaging method. Stationary solutions (bubble clusters) are found, and the conditions for their stability are established __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 5, pp. 88–94, May 2006.     

On the relationship between the dynamic behavior and nanoscale staggered structure of the bone

Bone, a typical load-bearing biological material, composed of ordinary base materials such as organic protein and inorganic mineral arranged in a hierarchical architecture, exhibits extraordinary mechanical properties. Up to now, most of previous studies focused on its mechanical properties under static loading. However, failure of the bone occurs often under dynamic loading. An interesting question is: Are the structural sizes and layouts of the bone related or even adapted to the functionalities demanded by its dynamic performance? In the present work, systematic finite element analysis was performed on the dynamic response of nanoscale bone structures under dynamic loading. It was found that for a fixed mineral volume fraction and unit cell area, there exists a nanoscale staggered structure at some specific feature size and layout which exhibits the fastest attenuation of stress waves. Remarkably, these specific feature sizes and layouts are in excellent agreement with those experimentally observed in the bone at the same scale, indicating that the structural size and layout of the bone at the nanoscale are evolutionarily adapted to its dynamic behavior. The present work points out the importance of dynamic effect on the biological evolution of load-bearing biological materials.     

On a new theory of the dynamic behavior of the structures carrying moving masses

Summary This paper represents an exact solution for a problem which has been of interest in Structural Engineering for many years. The solution is exact in the engineering sense; it converges very rapidly. The solution is given by means of an expansion of the eigenfunctions in a series. The eigenfunctions satisfying the boundary and transient conditions for masses moving over a structure have been determined exactly by performing the integration in the Stieltjes sense. The method is simple, short and elegant and is based on operational calculus. It yields the results in perfect agreement with an accurate numerical solution previously given in the literature.

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Über eine neue Theorie zum dynamischen Verhalten von Strukturen unter bewegten Massen

Übersicht In dieser Arbeit wird eine exakte Lösung für das Verhalten von Strukturen unter bewegten Massen gegeben. Die Lösung wird durch eine Reihenentwicklung in Eigenfunktionen ermittelt, wobei die Eigenfunktionen mit Hilfe von Stieltjes Integralen exakt bestimmt werden. Die Reihen konvergieren schnell; die Ergebnisse stimmen ausgezeichnet mit bekannten numerischen Lösungen überein.

     

On the dynamic behavior of a liquid droplet impacting upon an inclined heated surface

The dynamic behavior of a water droplet impinging upon a heated surface was shown to be significantly different, depending on the normal momentum of the impinging droplet before impact. This experimental study focused mainly on the effects of the impinging angle of the droplet on impact dynamics and its dependence on surface temperature. At the surface temperature of the nucleate boiling regime, disintegration of the droplet did not occur, whereas the deforming droplet adhered to the surface. The liquid film was spread and contracted several times on the horizontal surface, but the expanded droplet merely slipped without noticeable contraction on the inclined surfaces. In the film boiling regime, the impinging droplet spread over the surface as a liquid film separated from the surface by the vapor produced. Depending on the magnitude of the normal momentum of droplet, disintegration into several irregular shapes of liquid elements occurred in the case of the horizontal and 30°-inclined surfaces. The impinging droplet in the case of the 60°-inclined surface did not break up and tended to recover its original spherical shape. Received: 16 February 1999/Accepted: 9 November 1999     

Three-dimensional modeling of tires

Modeling the stress-strain state of pneumatic tires in the conditions of steady-state and transient rolling is of interest for mechanics of composites and computational mechanics and important from the applied point of view. Mechanical models of various levels of complexity can be used for numerical modeling. In quite a few papers, the corresponding models are derived from the theory of orthotropic shells [1]. However, more thorough and accurate studies of the stress-strain state can be carried out on the basis of three-dimensional models based on the elasticity or viscoelasticity equations. As far as Russian authors are concerned, this approach has first been suggested and implemented in [2]. Another, combined approach uses both the shell theory and the three-dimensional equations of elasticity theory [3, 4]. This approach is reasonable, because the tire structure includes both volumes filled with rubber and thin layers of the rubber cord. The rubber cord layers can be considered as a composite whose structural components possess very different properties. Also, it is quite admissible to consider the rubber cord as a structure periodic in the horizontal projection. Note that the mathematical theory of periodic composites has been developed in [5]. Owing to strong anisotropy and inhomogeneity of the material, large shape distortions of the tire, and, in some cases, its large deformations, viscoelastic properties of rubber play an important role, so that the mechanic model of the tire turns out to be quite complex. The large property differences between various structural components make the matrix of the resulting system of linear equations ill-conditioned, which complicates its numerical solution [6].In this paper, theoretical aspects of a three-dimensional tire model and its numerical implementation are considered.     

Modelling the dynamic behavior of multilayered composite structures

Moscow Region. Translated from Prikladnaya Mekhanika, Vol. 24, No. 3, pp. 39–45, March, 1988.     

Modeling the dynamic behavior of shape memory alloys

The paper studies the single degree of freedom vibration of a rigid mass suspended by a thin-walled shape memory alloy tube under torsional loading. The behavior is analyzed for the cases of quasiplasticity (low temperatures) and pseudoelasticity (high temperatures) on the basis of an improved version of the Müller–Achenbach model. To illustrate the strong hysteresis-induced damping capacity and the non-linear vibration characteristics, both, free and forced vibrations are considered in the first part of the paper. This is done on the basis of an isothermal version of the model, while the second part of the paper focuses on the effect of non-constant temperature caused by the rate-dependent release and absorption of latent heats.     

On the dynamic behavior of a functionally graded piezoelectric strip with periodic cracks vertical to the boundary

The dynamic anti-plane problem for a functionally graded piezoelectric strip containing a periodic array of parallel cracks, which are perpendicular to the boundary, is considered. Integral transforms techniques are employed to reduce the problem to the solution of singular integral equations. Numerical results are presented to show the influences of geometry, electromechanical combination factor and material gradient parameter on the fracture behavior.     

Calculation of the dynamic behavior of branched cable systems

A technique for the study of the dynamic behavior of three-dimensional elastic branched cable structures is proposed. Parametric local spline functions of spatial variables is used to reduce the boundary-value problem to a Cauchy problem. A graph of a three-dimensional cable structure is used to construct the solution algorithm. A study of the dynamic behavior of a hydrophysical anchored buoy system affected by the action of sea waves is performed, taking into account relaxation effects in individual elements. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 35, No. 9, pp. 106–110, September, 1999.     

Experiments on the dynamic behavior of fluid-coupled concentric cylinders

This paper describes an experimental vibration study of fluid-coupled coaxial cylinders that simulates the vibration of a reactor vessel with a thermal liner. The model cylinders are made of acrylic. Thickness and gap-size parameter studies are performed by a series of different compinations of three outside cylinders and nine inside cylinders that have variable thicknesses and diameters. Damping ratios are measured on a mode-by-mode basis for several combinations of cylinders. The vibrated cylinders are mounted to a rigid stand, with the cuter cylinder supported at both ends and the inner cylinder supported at either one end (pendulum mode) or both ends, as the case may be. The natural frequencies are obtained first in air and then with coaxial cylinders coupled by water. The mode shapes are obtained by circumferential (shell modes) and axial (shell/beam modes) mapping of the response with two diametrically opposite ‘roving’ Dymac eddy probes. In general, the natural vibration of the system has two distinct responses in-phase and/or out-of-phase modes, i.e., the radial displacement phase relationship between inner and outer cylinders. In the out-of-phase modes the frequency is shown to decrease to either zero or a very low limiting value as the gap size cecreases. The opposite occurs for in-phase modes. Damping ratios are found to be much higher for out-of-phase modes and for relatively rigid cylinders than for in-phase modes and flexible cylinders, respectively.     

On the theory and solution of dynamic problems of the nonstationary behavior of cylindrical shells with discrete variable stiffeners

The formulation and development of a numerical algorithm for solving shell theory problems concerning cylindrical shells with variable-stiffness reinforcements are considered. The Hamilton-Ostrogradskii variational principle is used to obtain the equation of motion. The algorithm is based on finite-difference approximation of the initial variational functional. A numerical example is presented. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Prikladnaya Mekhanika, Vol. 34, No. 6, pp. 53–59, June, 1999.     

On the dynamic shakedown stability

Summary Starting from a Benvenuto's sufficient stability Criterion, in the elastic-plastic range, on the load paths which will systematically exclude elastic returns in the actual state, and adopting a suitable incremental formulation of the Ceradini's theorem on the dynamic shakedown, the dynamic shakedown stability property may be proven, if the comparison material is assumed absolutely stable.

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Sommario Partendo da un noto risultato di Benvenuto circa un criterio sufficiente di stabilità elastoplastica su percorsi dei carichi che sistematicamente escludono ritorni elastici nello stato attuale, e adottando una opportuna formulazione incrementale del teorema di Ceradini sull'adattamento dinamico dei materiali, è possibile provare la stabilità dell'adattamento dinamico se il materiale fittizio di confronto è in fase stabile.

     

On the dynamic elastic limit

The fact that the elastic limit of some solids increases with increasing stress rate has been qualitatively and semiquantitatively established for many decades. Well known experimental difficulties have impeded reliable quantitative measurements of the magnitude or, in some solids, even the existence of such an increase of the elastic limit with stress rate. The present paper describes a simple method for accurately measuring the dynamic elastic limit in any solid which has a linear-elastic domain at small strain, including high-strength structural metal alloys. This method has the advantages of laboratory simplicity, a minimum of complex assumptions, and a close parallel with the manner in which the quasistatic elastic limit generally is determined. Although it is subsidiary to the main focus of this paper, evidence is presented here that a knowledge of the dynamic elastic limit firmly established by experiment, can be of considerable value for subsequent research in the continuum mechanics of solids, particularly with respect to the existence and properties of two distinct yield surfaces during impact loading.