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Destruction of Freshwater Polycrystalline Ice

#2605


Study of Processes of Destruction of Freshwater Polycrystalline Ice in Wide Range of Temperatures and Strain Rates

Tech Area / Field

  • MAT-OTH/Other/Materials
  • OBS-OTH/Other/Other Basic Sciences

Status
8 Project completed

Registration date
17.09.2002

Completion date
20.04.2007

Senior Project Manager
Tyurin I A

Leading Institute
VNIIEF, Russia, N. Novgorod reg., Sarov

Collaborators

  • Clarkson University / Department of Civil and Environmental Engineering, USA, NY, Potsdam

Project summary

In spite of the fact that ice belongs to number of most ancient natural materials, its properties have been studied far insufficiently. It can be explained by objective reasons. Because of great variety of structures, compositions, physical-mechanical states, ice properties are also rather various at various parameters of effects (temperature, intensity, duration and scale of effect, etc.).

Polycrystalline ice is a model material useful in fundamental researches in the field of mechanics of a deformable solid. Study of physical and mechanical properties of ice is a traditional and ultimately determining from the point of view of the subsequent engineering-technical applications. Many works are mostly devoted to properties of freshwater polycrystalline ice under static loading. To the present time the properties of freshwater ice under dynamic loadings and regularities of ice fracture are researched much worse.

A small number of works on study of ice crack-resistance have been published.

The concepts existing in fractures mechanics have been just started to be used for description of ice fracture. There are a few works on determination of characteristics of freshwater ice crack-resistance. Researches of crack-resistance of sea ices in the environment of deformation from quasi-static up to dynamic from 10 up to 10-3 s-1 have not been performed.

Goal of this project is study of processes of fracture of freshwater polycrystalline ice in a wide range of temperatures (from -60 to -1 °С) and strain rates (from 10-9 to 104 s-1). Thus in the specified range of temperatures, the physical-mechanical characteristics of polycrystalline ice will be determined.

Within the framework of the Project, it is planed to carry out collection, processing and analysis of data published in Russian Federation on physical-mechanical properties of polycrystalline ice.

It is planned to perform the following efforts under the Project frameworks:

– to develop a series of experimental techniques taking into account peculiarities of polycrystalline ice;


– to determine the physical-mechanical characteristics of polycrystalline ice in a wide interval of boundary conditions of loading and change of thermodynamic state;
– to study influence of deformation changes of ice structure on its physical-mechanical and strength characteristics, and regularities of its fracture;
– to study processes of origin, accumulation and interaction of cracks, and fracture of polycrystalline ice;
– to study interactions of steel cylindrical impactors with ice slabs;
– to study influence of scale factor at dynamic tests.

It should be noted that for the first time, in the author’s opinion, it is expected to obtain experimental data at strain rates of polycrystalline ice e = 10-104 s-1.

During Project efforts, it is planned to manufacture a portable device designed by one of the Project authors (Penetrometer. I/s USSR № 1539583 kl. G01N 3/48. Bull. № 4 30.01.90). This device is intended for collecting data on mechanical properties of ice in the environment of its natural deposition. It is planned to collect data on particular region.

Result of the Project will be accumulation of data on fundamental issues important for thorough understanding of ice fracture processes.

Except for the contribution to fundamental studies, the data obtained in this Project on dynamic characteristics, dynamic crack-resistance, study of interaction of steel cylindrical impactors will be useful for solving of a lot of applied problems, for example, for struggle against ice jams, solving of glaciers problems, etc. The above-mentioned portable device produced during the Project efforts can be used to estimate ice massive state for prevention of catastrophic situations.

Peculiarity of experimental studies planed within the Project framework will be solving of a series of methodical problems, which are taking into account specific properties of ice. In order to reduce scatter of measured values caused by residual stresses and defects in ice structure, it is planned to develop the technique for manufacture of samples of polycrystalline ice in laboratory environment, and the methods for estimation of identity of initial ice samples intended for mechanical tests.

It is planned to up-date the available experimental techniques, and to develop the measuring complex for observations of changes in microstructure of polycrystalline ice directly during deformation without need for unloading and micro sections production. This method is based on volume probing of a deformed sample by high-frequency acoustic impulses and recording of amplitude-frequency parameters of AE signals. The method is verified by the authors by testing ice and other structural materials at various types of stress-strain states.

For keeping the required temperature during tests, we plan to use cryochambers. The minimum gradient of temperature will be reached with the help of two thermostatic shells and additional cooling of supporting platforms of the testing machine.

The processes of origin, accumulation and interaction of cracks, as well as fracture of polycrystalline ice of various structure at static will be carried out with the help of the acoustic methods.

Studies of initiation and interaction of cracks in large-sized ice slabs during tests by the split-Hopkinson-bar method will be carried out with the help of high-velocity digital video camera making 10 thousand frames per second.

Mechanical characteristics of polycrystalline ice at uniaxial dynamic tension and compression during Project efforts will be determined by the split-Hopkinson-bar method (the Kolsky method).

This method for testing of structural materials at strain rates e = 10-104 s-1 has correct calculated and experimental substantiation. On the basis of the Kolsky method in VNIIEF more than twenty years ago, the testing facilities with explosive damping loading were developed and used. They allow to perform tests both in the field and laboratory environment. The explosive loading device allows to form impulse loadings of trapezoidal shape, and to vary loading amplitude within a wide range. This enables to perform testing of materials, which are tens times differ in strength. Application of compact cryochambers allows to perform dynamic tests at decreased temperatures (up to -60 °С).

Specified temperature will be also kept at end faces of measuring cores, between which a tested sample is placed.

Study of process of interaction of rigidly-cylindrical impactor with large-scale slabs of ice will be carried out at unique ballistic facilities with use of energy of explosion and pressure of compressed gas for formation of impulse loadings. Impactor velocity is 350-500 m/s.

The principle of operation of the above-mentioned portable device, which is planned to be produced during the Project efforts, is based on studies performed by the authors with ice fracture at dynamic insertion of a rigid spherical indentor equipped with piezoelectric accelerometer.

Methodology of the researches fits the world level. It is based on works of G. Kolsky, J. Klepachko, and scientists from RFNC-VNIIEF. This technique allows researching the dynamic crack-resistance of materials at various temperatures that is a doubtless advantage before the known Russian and foreign techniques allowing carrying out tests only at normal temperature. The proposed technique for research of dynamic crack-resistance in application to the problems of research of polycrystalline and sea ices is pioneer, facilitating deeper understanding of complicated regulations of their fracture.

The author's team has wide experience in experimental studies of mechanical characteristics of polycrystalline ice and processes of its fracture depending on temperature and loading rate, and in experimental studies of dynamic fracture of materials in various environments of loading.

From the early 80th, alongside with the other studies of dynamic strength of materials performed for a long time already, the author's team has studied their dynamic crack-resistance.

Competence of the highly skilled participants of the Project in the field of study of physical-mechanical properties of polycrystalline ice, dynamic fracture of materials in various environments of loading does not cause doubt, and it is documentary confirmed by large number of publications.

It gives reliance that the Project objectives will be reached by efforts of the author's team.

This Project meets ISTC goals and objectives:

– Project relates to fundamental researches. Experimental data got in the Project frameworks will make large contribution to thorough understanding of processes of destruction of polycrystalline ice.


– Project encourages involving of experts producing a nuclear ammunition into international cooperation.

The suggested Project provides highly skilled weapons scientists and engineers from RFNC-VNIIEF with opportunities to redirect their talents to peaceful activities.

Project duration is 2 years. Role of foreign Collaborators includes discussion of place for arrangement of experiments aimed to determine mechanical properties of ice in environments of its natural deposition.


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