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Modeling of Motion Processes in a Substance

#1124


Development of the Model of Substance for Description of Processes with Motion of Brittle Low-Strength Media

Tech Area / Field

  • PHY-STM/Structural Mechanics/Physics

Status
8 Project completed

Registration date
09.10.1997

Completion date
21.08.2003

Senior Project Manager
Novozhilov V V

Leading Institute
VNIITF, Russia, Chelyabinsk reg., Snezhinsk

Collaborators

  • Korea Institute of Machinery&Materials, Korea, Changwon\nCEA / DAM / CE Bruyères le Châtel, France, Bruyères le Châtel

Project summary

The main goal of the project is to create a computation technique for the description of physical processes in brittle low-strength media which takes into consideration such an important from physico-mechanical point of view phenomenon, as loosening of brittle destroyed rock and other associated effects. For example, such processes take place during realization of explosions, in case of large natural destructions and as a result of collision of space bodies.

The majority of rocks of which the Earth's upper mantle consists (granite, basalt, etc.) are brittle materials. In normal conditions they collapse because of insignificant deformations, breaking down into separate fragments (pieces). The investigations, which were, performed earlier show that the strength of rocks plays a minor role in explosion processes with ground ejection in comparison with internal (dry) friction. Much the same occurs in camouflet explosions. The energy spent for destruction of rocks is, as a rule, significantly exceeded by the expenditure of energy for overcoming of internal friction during the process of large shear deformations. Therefore, in many cases the initial medium can be simulated by a substance, which consists of separate closely packed pieces. It simplifies the description of the explosive phenomena picture significantly and makes it independent of highly variable (as a result of natural cracks) characteristics of strength of rocks. The difficulty is not only in this, but also in the method of stressed state computation from given deformations. Usual elastoplastic models are unsuitable for the description of behavior of such materials, especially in conditions of low temperatures and stresses. Besides above mentioned rocks, loosening as a physical phenomenon is inherent in many mediums, such as concrete, ice, brick, glass, coal etc. Therefore, the development of the destroyed medium model, which taking into account process of loosening, is an important part of the project.

The problem of the study into dynamic processes with large deformations of ground is many-sided and contains both fundamental and applied aspects, which are supposed to be investigated within the framework of this project.

In the theoretical plan, the mathematical model of a substance consisting of separate pieces (granules) of destroyed medium will be developed. This model was proposed by the author of the project. The model takes into account different states of the medium, which differ by the extent of packing of its pieces, and also describes the transition from one state to another. The model takes into account the relation between deformations and the change of stressed state of an arbitrary element of medium, the properties of which are considered isotropic. The method for computation of the change in internal energy during the process of deformation is given. The special attention is given to the physical substantiation of this model.

The experimental study into the behavior of destroyed material in conditions of large deformations of different types in insufficiently known area is planned to be carried out at the laboratory sites of the VNIITF Scientific Research Testing Complex in static and quasi-static conditions. A series of experiments is proposed to be taken with various materials, as well as their theoretical data processing. Both experiments with links of dense structures under different pressure and different initial porosity, and study of regularities of change of internal friction are obligatory. Experiments with all-round compression and off-loading are necessary. Should be noted that the planned experiments will be very labour-consuming. To ensure necessary modes of deformation and necessary accuracy of measurements, we need to design and produce new devices and installations.

The results of the work on the project will be as follows:


- Experimental dependencies of physical parameters characterizing the state of substance will be obtained; this will allow the model to be improved. New laws, which were not taken into account in the model, can be found out.
- The existing techniques for the computation of the destroyed medium dynamics will be improved on the basis of obtained experimental data and the refined model.
- Mathematical programs will be developed for the solution of dynamic problems in two-dimensional geometry, and, perhaps, in three-dimensional geometry as well. The class of the problems, which can be solved, will depend not only on the set of experimentally investigated materials, but also on the capabilities of computer facilities.
- The model of medium and the parameters included in it will be checked and additionally calibrated on the basis of computations of the large-scale centers of underground explosions, especially on the basis of such computations, where unexpected results were obtained (The experiment "Salki" is a characteristic example).

In the future, successful accomplishment of the project will allow getting considerably more precise computed results when solving different practical problems. Let us put a list of Fields of Applicability of the Destroyed Medium Model.

I. Seismic catastrophes

1. Computing generation of seismic waves and tsunami caused by earthquake (Improvement of insights in shock waves formation and dissipation nearby a source).
2. Improvement of insights in shock waves propagation and interactions with the bases of facilities.


II. Extraction of mineral resources

1. Seismic survey (research of the Earth layers by explosive waves/ Refinement of formation of a wave near to a source of explosion.
2. Computing external explosions produced for splitting and open excavating of large volumes of rocks (designing developed deposits with rock exposure).
3. Drive underground workings by explosion.
4. Optimization of excavating parts of miner machines.


III. Industrial explosions

1. Computing foundation pits for large industrial objects.
2. Computing blasting for constructing dams embankments.
3. Safety of surrounding facilities from explosions.
4. Destructing an icing of foundations of bridges, trestles, etc. by splitting with the help of miniexplosions.


IV. Risk and its reduction in the work with environmental hazardous products

1. Safety of nuclear power plants at a falling of planes and terrorist acts.
2. Accurate strength computing collision between containers with wastes of nuclear power plants and barriers (concrete, ground etc.) during storage and transportation.
3. Computing a behavior of reservoir with environmental hazardous products when an accident during transportation (train crash etc.).


V. Space protection of the Earth

1. Computing consequences of space body impact on the Earth.
2. Destruction of dangerous space objects.


Thus, the range of applicability of proposed model is extremely wide: from simulation of global catastrophic processes up to modeling of "miniature" explosions.

The results obtained experimentally and the laws established during this work can be of fundamental significance for the development of the destroyed medium mechanics.

Purposeful long-term cooperation in science and technology between specialists of RFNC-VNIITF and potential Foreign Collaborators will allow to familiarize with unique research being executed at RFNC-VNIITF. Various types of collaboration, important for an interested party suit us, for example:


- Participation in the development of project proposal and work plan.
- Exchange of information during project implementation.
- Mutual review of technical reports.
- Joint seminars, workshops, meetings, consultations.
- Verification of results using independent methods and/or equipment.
- Sharing of scarce materials, samples, resources.
- Joint or parallel investigations.
- Consultation on Intellectual Property Rights, in case of joint invention.
- Other types of collaboration are possible.


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