Contents of the Journal of Mechanical Engineering 49, 6 (1998)

J. MURIN: Non-linear equations of a hyperelastic bar and their solution  373

P. MUCKA: The influence of heavy vehicle active suspension on the 
reduction of road dynamic load (in Slovak)                               384

K. VAVRO, P. HODUR, F. DZIANIK: Balistics of dust particles (in Slovak)  396

S. MORAVKA: A comparison of the analytical solution 
of  the  transient impact strain of continuum with a discretized 
FEM solution (in Czech)                                                  406

M. KARAS, A. P. ZIELINSKI: Application of Trefftz complete functional 
system to stress analysis in helical spring with an arbitrary wire 
cross-section                                                            426

Non-linear equations have been obtained in incremental and non-incremental form for axial hyperelastic material. These equations define the relationship between loading and elongation of bar. We propose three algorithms for their solution after their linearization. The effectiveness of the algorithms is compared with the solution obtained by consistent linearization.

In this paper various concepts of active vibration isolation systems for use in a heavy vehicle suspension are analysed. The concepts are considered as a real or a fictitious damper placed between parts of the vehicle model. For simulation a quarter car model is used. The model is kinematically excited by random signal corresponding to the road unevenness. The aim was to find the most suitable concept from the viewpoint of road damage reduction. Except of the improvement of the potential road damage, the possibilities of various concepts are analysed from the viewpoint of ride comfort improvement, required workspace of the suspension and power requirement. The criteria for estimation are standard deviations of dynamic force, car body weighted vertical acceleration, relative displacement between car body and chassis (suspension stroke), and active force. Influence of cost function weighting coefficient that emphasizes the road damage reduction is taken into consideration. The results are compared with that ones corresponding to passive suspension.

In the paper a new approximate function for calculation of resistance of non spherical isometric dust particles at their movement in fluid viscous medium is published. The shape difference of the isometric particle from the spherical shape is described by the sphericity coefficient. Flight parameters of the particles with various sizes and various shapes thrown up vertically with various velocities are introduced in a graphical way. This enables to create reader's opinion about flight properties of the dust particles thrown into air at its normal conditions.

The paper presents a desired practical comparison of the extensive numerical calculation of the 3D transient strain by the Finite Element Method with the exact analytical solution. The properties and abilities of two commercial FEM systems - DYNA3D and MARC - are tested. The substantial effects of spatial discretization of continuum are summarized in the introductory part. These effects are demonstrated by several strain and stress dependencies like typical FEM properties. The results of the above-mentioned comparison have made possible to choose the parameters of numerical computation more professionally and to improve the reliability of the obtained FEM results for problems of this type. The analytical results of a longitudinal impact of thick elastic rods have been used for the comparison.

Trefftz functions for a special case of a two-dimensional quasi-harmonic differential equation are derived and investigated. The global Trefftz method using these trial functions is applied to the stress analysis in a helical coil spring with an arbitrary wire cross-section, subjected to a static tension or compression.