Finite element modeling of contact conditions in multibody system dynamics

In this paper a new method is developed for the dynamic analysis of contact conditions in flexible multibody systems undergoing a rolling type of motion. The relative motion between the two contacting bodies is treated as a constraint condition describing their kinematic and geometric relations. Equations of motion of the system are presented in a matrix form making use of Kane's equations and finite element method. The method developed has been implemented in a general purpose program called DARS and applied to the simulation and analysis of a rotating wheel on a track. Both the bodies are assumed flexible and discretized using a three dimensional 8-noded isoparametric elements. The time variant constraint conditions are imposed on the nodal points located at the peripheral surfaces of the bodies under consideration. The simulation is carried out under two different boundary conditions describing the support of the track. The subsequent constraint forces associated with the generalized coordinates of the system are computed and plotted. The effects of friction are also discussed.     

Effect of thermal radiation exchange between boundaries on convection in a gas heated from below

Natural convection problems offer many examples of branching of the solutions [1]. Usually, such branching (from the standpoint of catastrophe theory) can be described by a Whitney fold or cusp. A characteristic feature of nontrivial branching is the presence of some small but finite disturbance of the convective equilibrium conditions. In this study the perturbation disturbing the convective equilibrium of a fluid heated from below is Stefan-law thermal radiation exchange between the boundaries of the enclosure. Natural convection with lateral heating and allowance for radiative heat transfer was previously investigated in [2].Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.5, pp. 47–51, September–October, 1992.     

Self motion of a body in a fluid

Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 111–118, March–April, 1990.     

三维运动接触问题的广义Галин定理

本文给出了求解一类相当普遍的三维运动接触问题的分析解法,并且把仅仅对静态接触问题成立的 定理推广到动力学情形,作了严格证明。作为例子,对接触区为椭圆的情形给出了积分形式的解,并且作了数值计算,由这些结果可以看出运动压体速度的效应。     

Zero-shift values of automatic and inexpensive strain-gage instrumentation systems

Computer-controlled data-acquisition systems are being used extensively for gathering strain-gage data. This paper explores the relative merits of using modern solidstate digital multi-meters (DDM) to measure the strain-gage resistance directly rather than using a conventional Wheatstone bridge. Both a direct-resistance measurement scheme and a reversed current scheme are compared over long measurements terms of 6 and 12 days using a 6 1/2-digit multimeter. The results show that the reversed current method is superior in maintaining the zero-gage resistance reading at the cost of using several meters. Possibly the direct-resistance method can be improved so that the operation and equipment can be simplified.Paper was presented at the 1990 SEM Spring Conference on Experimental Mechanics held in Albuquerque, NM on June 4–6.     

Dynamische Wechselwirkung eines Fundamentes mit dem viskoelastischen Halbraum

Übersicht Im Zusammenhang mit der Ermittlung des dynamischen Verhaltens erregter Strukturen wird die Wechselwirkung von Fundament und Baugrund behandelt. Ein auf der Kontinuumstheorie basierendes Verfahren zur Berechnung von Vertikal- und Kippschwingungen beliebig berandeter, starrer Fundamente auf dem als viskoelastischer Halbraum abgebildeten Baugrund wird angegeben. Die Lösung eines dreidimensionalen dynamischen Spannungsrandwertproblems erlaubt mittels linearer Superposition die Berechnung der Parameter eines Halbraumersatzmodelles, der dynamischen Sohldruckverteilung sowie der Ausbreitung erzwungener Wellen im Erregernahfeld.

---

Summary Subject of the present paper is the dynamics of soil-foundation interactions. This interaction has to be included in calculating the response of dynamically loaded footing-supported structures. Vertical and rocking vibrations of an arbitrarily shaped rigid base resting on the surface of a viscoelastic halfspace are considered. A three-dimensional dynamic stress boundary value problem is solved using a continuum approach. Based on this solution one can calculate by means of linear superposition spring and damping coefficients of a lumped-parameter model for the halfspace, the actual pressure distribution at the interface between base and soil as well as the wave-propagation in the vicinity of the excitation.

     

Two-dimensional nonstationary gas dissipation into a vacuum from a plane or axisymmetric channel

The nonstationary escape of an ideal polytropic gas from a plane or axisymmetric channel is investigated. It is hence assumed that the gas is initially at rest, and the diaphragm separating it from the vacuum can be at any section of the channel.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 76–83, January–February, 1976.     

Computation of the shock adiabats of argon and xenon

Results of computations of the shock adiabats of Ar and Xe taking account of ionization, electron excitation, and a nonideal plasma are represented. Energy losses by radiation are estimated.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 70–76, May–June, 1973.     

Integration of the quasilinear equations of motion of a mixture through a porous nondeformable medium

Numerical methods are analyzed of solving the quasilinear system of partial differential equations describing the motion of a sorbed gas (liquid) mixture through a porous, saturated, nondeformable medium consisting of porous grains. Conditions are obtained for convergence of the iteration process of a difference scheme. Conditions are found under which the system attains invariant solutions of the running-wave type. Estimates are obtained of times and coordinates, during which and through whose passage the solutions of the boundary-value problem become invariant.