Elastic, thermal expansion, plastic and rheological processes - theory and experiment

Rocks are important examples for solid materials where, in various engineering situations, elastic, thermal expansion, rheological/viscoelastic and plastic phenomena each may play a remarkable role. Nonequilibrium continuum thermodynamics provides a consistent way to describe all these aspects in a unified framework. This we present here in a formulation where the kinematic quantities allow arbitrary nonzero initial (e.g., in situ) stresses and such initial configurations which - as a consequence of thermal or remanent stresses - do not satisfy the kinematic compatibility condition. The various characteristic effects accounted by the obtained theory are illustrated via experimental results where loaded solid samples undergo elastic, thermal expansion and plastic deformation and exhibit rheological behaviour. From the experimental data, the rheological coefficients are determined, and the measured temperature changes are also explained by the theory.Comment: 15 pages, to appear in Period. Polytech. Civil En

A device for testing tractors on fields

A new dynamometer vehicle was developed by the Hungarian Institute of Agricultural Engineering (MGI) to determine the traction performances of agricultural tractors on soft soil (fields) and on hard surfaces. The braking system of the vehicle is a special diesel-hydraulic version with 400 kW of power. Drawbar-force and travel-speed measurement and control and real-time data analysis are realised with a Programmable Logic Controller (PLC) control unit and Personal Computer (PC) data collection. The dynamometer vehicle developed is not only suited to the determination of the performance data of agricultural tractors on fields, it is also useful for research and development testing of tractors

Szilárd testek rugalmas, hőtágulási és képlékeny folyamatainak termodinamikája Thermodynamics of elastic, thermal expansion and plastic processes of solid bodies

ÖSSZEFOGLALÁS: A szilárd testek termodinamikai tárgyalásának egyik alappillére a szilárd közeg mozgásainak leírása. Az irodalomban hagyományosan elterjedt közegkinematika számos problémáját nemrég sikerült (kutatócsoportunknak) kiküszöbölni. Erre az alapra újra fel kell építeni a termodinamikát, és ennek a munkának az eddig elért eredményeiről számolunk itt be. A rugalmas, hőtágulási és képlékeny folyamatokat együttesen leíró termodinamikai egyen¬letrendszert kisdeformációs közelítésben ismertetjük, oldjuk meg egy numerikus példán, majd az egyes viselkedéseket egy kísérlet eredményein keresztül mutatjuk be. ABSTRACT: The description of the motion of a solid continuum is a basic ingredient of the thermodynamics of solid bodies. The several problems of the widespread traditional approach to the kinematic quantities of continua has been recently successfully eliminated (by our research group). Thermodynamics has to be rebuilt upon this basis, and, here, we report on the results of this work that have been reached so far. We present the thermodynamical sys¬tem of equations describing elastic, thermal expansion and plastic processes together, shown in the small deformation approximation, then we solve the equations in a numerical example, and illustrate the various types of behaviour via the results of an experiment