Issue 3

JTAM, Sofia, vol. 23 Issue 3 (1992)

Mechanics of Biomolecules and Bioelectronics

G. Brankov
Institute of Mechanics and Biomechanics, Bulg. Acad., Sci. Sofia

A brief analysis is made on Physics, Chemistry and Biology methods, which help biological structures and processes to be studied on molecular and atomic level. These sciences have used quantum mechanical methods in their development. A conclusion is drawn that this approach ought to find an application in molecular mechanics as well. The potentialities of the phenomenological approach are limited. Phenomena and processes on a macro level are predetermined by the micro level. The dynamics of the biomolecule is considered in three aspects: vibration, rotation and movement. Bioelectronics, biochips and biosensors are briefly discussed too.

JTAM, Sofia, vol. 23 Issue 3 pp. 008-019 (1992), [Full Article]

Fundamental Identities of Lagrangean Formalism for Holonomic Mass-Points and for Rigid Bodies

G. Chobanov1, I. Chobanov2
1Bulgarian Academy of Sciences
2Sofia University

For systems of a finite number of mass-points the fundamental Identities (33) of Lagrangean formalism are deduced by means of purely identical transformations applied on the definitions of the mechanical entities therein involved. These identities are analogous for mass-point systems of the fundamental identities (45) of Lagrangean formalism in rigid body dynamics, deduced by the authors in previous papers. At that, no use is made of such metaphysical notations as virtual displacements, virtual velocities, or virtual work. In both cases (33) and (45) the Lagrangean dynamical equations for the motion of the respective mechanical systems are obtained as plain corollaries from the Newtonian dynamical axiom (the law of momentum) in the first case and from the Eulerian dynamical axioms (the laws of momentum and of moment of momentum) in the second case. As it is immediately seen from (33) and (45), in rigid body dynamics, as well as in mass-point dynamics, Lagrangean dynamical equations are, purely and simply, linear combinations of the projections of Newtonian and Eulerian dynamical axioms respectively on the appropriate axis in space.

JTAM, Sofia, vol. 23 Issue 3 pp. 020-035 (1992), [Full Article]

Perturbations of a Mechanical System with Two Degrees of Freedom

O. Christov
Sofia University

For a mechanical system with two degrees of freedom action variables are introduced. Then it is shown that KAM – theory conditions namely Kolmogorov's condition and condition of isoenergetical non-degeneracy are fulfilled everywhere in the bifurcation diagram of the energy-momentum map.

JTAM, Sofia, vol. 23 Issue 3 pp. 036-049 (1992), [Full Article]

Calculation of the Free Molecular Drag and Lift Coefficients of Satellites with the Shape Element Method

D. Johannsmeier, G. Koppenwallner
Hyperschall Technologie Gottingen, Germany

The shape element method (SEM) is used for trajectory calculations of satellites. The real satellite is divided into shape elements, such as cones, cylinders, spherical caps, boxes etc. The SEM, applied in this paper, is based on an analytical solution, considering the local surface pressure and the skin friction of the shapes under consideration. A satisfactory accuracy of the solution is obtained. The paper was reported at the 1-st International Workshop on Numerical Methods in Rarefied Gas Dynamics, Varna 12-16 September, 1991.

JTAM, Sofia, vol. 23 Issue 3 pp. 050-064 (1992), [Full Article]

On the Constitutive Ilyushin's Theory Relations for the Case of Lare Deformation – Part I

P. Trusov, U. Nyashin
Politechnical Institute, Perm, Russia

The paper seeks to establish the constitutive relations which are a generalization of Ilyushin's Elastoplastic Process Theory for the case of large plastic deformation. Motion decomposition methods, the strain trajectory notion and the loading process image are generalized for the case of large deformations in this connection.

JTAM, Sofia, vol. 23 Issue 3 pp. 065-074 (1992), [Full Article]

Limit Equilibrium of Dilating Medium with Initial Stresses

E. Makaroff1, G. Gencheff2
1Tula Technical Institute, Russia
2Space Exploration Institute, Bulg. Acad., Sci., Sofia

A variant of limit equilibrium theory of dilating medium and porous metals, concrete, soil and so on) with initial stresses is suggested. Plane deformation is considered as an example. Relationships between basic equations are studied regarding plane deformation. For hyperbolic systems one can detect characteristic equations and the correlations, valid along the characteristics.

JTAM, Sofia, vol. 23 Issue 3 pp. 075-080 (1992), [Full Article]

Dynamic Parameters during Fracture of High Manganese Steel (Hadfield Type Steel)

K. Minchev
nstitute of Metal Science and Technology, Bulg. Acad. Sci., Sofia

Mechanical characteristics variations of explosion strengthened steel are observed in a wide range, depending on a number of process parameters. An analysis of published data reveals that to a great extent investigations are directed towards studying the strengthened materials behaviour under static load. A strengthened high manganese Mn13 steel behavior has been assessed by fracturing Charpy specimens and by determining the energetic characteristics. Data about the impact load and technological parameter effects on the variation of some studied steel characteristics are presented.

JTAM, Sofia, vol. 23 Issue 3 pp. 081-089 (1992), [Full Article]