Issue 3

JTAM, Sofia, vol. 13 Issue 3 (1982)

A Generalized Design Approach and a Common Synthesis Method for Mechanisms with Rotating Input Link

V. Galabov
High. Inst. Mech. Electr. Eng., Darvenitsa

A procedure for the design and a common method for the synthesis of different types of single loop functional mechanisms with rotating input link is proposed, wherein the common kinematic invariants and the optimal by type and parameters mechanisms are determined in conformity with the prescribed conditions.

JTAM, Sofia, vol. 13 Issue 3 pp. 011-019 (1982), [Full Article]

Qualitative Kinematic Characteristics of the Functional Capabilities of Manipulating Systems

L. Lilov, B. Bekyarov
Inst. Mech. Biomech. Bulg. Acad. Sci., Bl. 8 Geo Mlilev

The paper proposes methods for the generation of kinematic qualitative characteristics of the functional capabilities of manipulating systems. Using those methods it could be formally expressed and quantitatively estimated any important-for-practice property, concerning the kinematics of motion of manipulating systems. The methods proposed could be used for the generation of estimations reflecting a specific aspect of the action of the manipulating system. The estimations of greatest practical interest are especially analysed and discussed.

JTAM, Sofia, vol. 13 Issue 3 pp. 020-029 (1982)

Vector Equations of the Kinematics and Dynamics of a Manipulator Mechanism

Y. Knapchik

The paper presents a vector method for the solution of the inverse kinematic and dynamic problem for the operating mechanism of a manipulator with 6 degrees of mobility.

JTAM, Sofia, vol. 13 Issue 3 pp. 030-036 (1982)

Calculation of the Electron Properties of Molecules of Large Clusters Using the Xα Method

G. Gadiak, V. Malkin, Y. Morokov, S. Chernov

The paper presents a survey of various Xα methods. A comparison between them is made and application to the solution of problems in the modelling of volume and surface properties of solids is analysed.

JTAM, Sofia, vol. 13 Issue 3 pp. 037-052 (1982)

Waves with Fixed Length in Thermo-Visco-Elastic Medium with a Finite Speed of Heat Propagation

Ts. Ivanov
Inst. Mech. Biomech., Bulg. Acad. Sci., BI. 8, Geo Milev

It is considered a propagation of harmonic waves with fixed length in thermo-visco-elastic medium where heat propagates with finite speed. The paper takes into account that while in classical thermo-elesticity the thermal wave is a standing one and the elastic wave propagates with a definite phase speed, here the two waves propagate with a definite speed or one could observe two or four standing waves. More than that the wave could be of one and the same character for small and great values of its reduced length or could change its character. It is analysed as well the variation of the common characteristics of displacement and temperature for various values of the wave length.

JTAM, Sofia, vol. 13 Issue 3 pp. 053-062 (1982)

Reaction Loads in the Edges of Cracked Steel-Reinforced Concrete Elements

L. Oksanovich
High. Inst. Arch. Civ. Eng., 1 Hr. Smirnenski Blvd, Sofia

The paper analyses an important problem in the calculation of steel-reinforced skeleton structures. It takes into account thereal stiffness of the element by means of a quasi-elastic solution, obtained following the classical deformational method. A method for the calculation of the reaction in steel-reinforced elements is proposed, wherein it is used a conventional averaged stiffness of the cross section as well as correction coefficients, which take into account the character of cracking. The method proposed is simple enough and of relatively high accuracy. It is convenient for algorithmic presentation.

JTAM, Sofia, vol. 13 Issue 3 pp. 063-069 (1982)

The Theory of a New Surface Dilatational Viscometer

C. Christov1, D. T. Wasan2
1Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8 Geo Milev
2Illionois Institute of Technology, Chicago, USA

A new method for the measurement of surface dilatational viscosity is proposed and the principle of operation is discussed. The new viscosimeter consists of a rotating cylinder submerged at a shallow depth under the surface of a surfactant solution. The "net" surface dilatational viscosity can be deduced by monitoring the surface velocity of the solution.

JTAM, Sofia, vol. 13 Issue 3 pp. 070-078 (1982), [Full Article]

Cylindric Orthotropic Shells Undergoing External Pressure – A Geometrical Stability Theory Considering Postcritical Deformations

Y. Ivanova
Inst. Mech. Biomech., Bulg. Acad. Sci., B1.8 Geo Milev

The paper investigated postcritical deformations of the shells treated. The investigation is performed on the basis of the variational principle A, modified for anisotropic shells by Y. Ivanova and V. Babenko. A simple formula for the value of the lower critical pressure, depending on the elastic and geometrical parameters of the problem, is obtained in the first part of the paper. The result is compared to that in the isotropic case. In the second part it is investigated the effect of the shell edge (the gill closeness) on the value of the lower critical pressure. The behaviour of the lower critical pressure, depending on the elastic characteristics, is graphically illustrated.

JTAM, Sofia, vol. 13 Issue 3 pp. 079-085 (1982)

Application of the Finite Element Method to Anisotropically Hardening Materials

A. Baltov, N. Boncheva
Inst. Mech. Biocmech., Bulg. Acad. Sci., Bl. 8 Geo Milev

A version of FEM is developed which is applied to strain rate sensitive, anisotropically hardening materials. Due to the nonlinearity of the differential equations describing the deformation process, it is used the method of the additional loads. The method of solution is applied to the case of plane stressed state. An example for a cantilever wall-beam is given and the effects resulting from the anisotropic hardening are shown.

JTAM, Sofia, vol. 13 Issue 3 pp. 086-098 (1982)

Finite Elements for the Solution of Static Crack Problems in Two and Three Dimensions

J. Altenbach, L. Wiltinger
3010, Magdeburg DDR

The considerations in this paper concern static cracks in two and three dimensions for linear elastic and elastic-plastic materials. For the solution of elastic crack problems a number of elements in the vicinity of the crack front and the surrounding regions in described. In the elastic-plastic case a mixed procedure, based on an iteration scheme, is presented, which optimises the rapidly growing computing time in three dimensional problems. A special procedure which divides the whole FEM – calculation into a number of single steps, permits the increase of the computable number of degrees of freedom (segement procedure).

JTAM, Sofia, vol. 13 Issue 3 pp. 099-104 (1982), [Full Article]

On the Accuracy of the Linear Programming Method Applied to Optimization Problems in the Limit State Theory

T. Daalov
High. Inst. Arch. Civ. Eng., Sofia

The effect of the range of limit moment variation in optimization problems of the limit state theory is considered, taking into account one-dimensional structures. It is made an approximation of the real relation, using a linear function of size and error.

JTAM, Sofia, vol. 13 Issue 3 pp. 105- (1982)