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Non-Destructive Control Method of Material Fatigue

#2314


Development of Physical Principles of Non-Destructive Method for Control over Material Fatigue Degree Basing on Measurement of Dynamic Characteristics of Elastic-Plastic Wave Initiated by Pulse Source of Energy

Tech Area / Field

  • INS-DET/Detection Devices/Instrumentation
  • PHY-NGD/Fluid Mechanics and Gas Dynamics/Physics

Status
3 Approved without Funding

Registration date
26.09.2001

Leading Institute
FIAN Lebedev, Russia, Moscow

Supporting institutes

  • Saint-Petersburg State Institute of Engineering, Russia, St Petersburg\nVNIIEF, Russia, N. Novgorod reg., Sarov

Collaborators

  • Laboratoire pour L'Aplication des Lasers de Puissance, France, Arcueil\nENEA, Italy, Frascati\nGeneral Atomics, USA, CA, San Diego

Project summary

Goal of the Project is development of physical principles for the methods of non-destroying control over material fatigue degree basing on measurement of the dynamic characteristics of propagation of elastic-plastic wave initiated by an action of pulse source of energy.

Control over fatigue of constructional materials is one of the most important current technological problems associated with an operation of space devices, nuclear reactors and other power facilities, pipelines, transport and other constructions subjected to significant loadings during operation. This problem becomes especially urgent for nuclear reactors, since duration of operation of many Russian reactors approaches to the 30-years boundary that is critical from the point of view of radiation resistance of materials. Up-dating of the methods for control over materials fatigue will allow to raise level of facilities operation safety. From the technological point of view the special value is represented by the non-destroying methods for mobile control over fatigue, which could be used directly at place of operation of devices and equipment without need to transport fragments of constructions to a laboratory.

The material fatigue phenomenon consists in change of strength properties of material as result of effect of varied mechanical and thermal loadings. At the early stage of material fatigue, micro cracks and interior stresses occur in it. At the late stage these processes result in formation of macro cracks, which are the reasons of fatigue fracture of a construction. Analysis of state of a material subjected to loading and underwent a certain degree of fatigue degradation is a complicated problem. Solution of this problem includes development of the methods for diagnostics of interior state of material, creation of database of recorded responses to calibrated effect for the complete-resource and tired materials, and methods for an analysis of signals for identification of an informative component.

The present methods of the non-destroying control over materials fatigue are based on a ultrasonic, magnetic-inductive, tomographic and radio-wave diagnostics. However, these methods allow performing control over fatigue only at a late stage of its evalution, as they are able to diagnose rather large defects with sizes of several hundred microns. Control over early stage of materials fatigue is based on laboratory investigation of the material strength properties by mechanical methods and (or) investigation of its interior structure with application of electronic microscope or X-ray diffraction analysis. In practice these methods are not non-destroying, and they can not be used in mobile regime.

In this Project the new direction in a development of the non-destroying methods for control over materials fatigue, including at its early stage, is suggested. Two basic statements of this direction consist, firstly, in use of elastic-plastic waves for diagnostics material state, since their dynamics is sensitive to change of mechanical properties and dissipative characteristics of medium, and secondly, in use for initiation of these waves a narrow-directed pulse source of energy of short duration such, as a laser or electron beam. Under the framework of the Project it is planned to perform experimentally and theoretically fundamental researches of the physics of propagation of the elastic-plastic waves initiated by the pulse of laser radiation or electron beam in material with various degrees of fatigue. It is planned to carry out the investigations how dynamics of the elastic-plastic waves depends on properties of elasticity and fluidity of material, its transport properties, and dissipative processes associated with formation of the dislocations and micro cracks in a tired material.

As the characteristics of the waves propagation, it is suggested to study the amplitudes of pressure, velocity and displacement of substance. As the result of the Project efforts, databases will be created on these characteristics for the complete-resource materials and materials with a various degrees of fatigue, the methods will be developed for their comparative analysis to perform a certification of a tired material, the “fatigue curves” will be made for dependence between degree of fatigue degradation of material and its physical-mechanical characteristics. Equations of state for the materials with a various degrees of fatigue and equation for a prediction of certain degree of fatigue of the materials operated in the given conditions of loading will be found.

For the researches, three pulse sources of energy providing various pulse durations and intensities will be used, namely: neodymium laser with energy up to 20 J having the duration varied from 5 up to 30 ns and the intensity varied in the limits from 109 до 1012 W/cm2, and with the controllable energy distribution in a focal spot (amplitude of a non-uniformity of irradiation is less 10%); the neodymium laser with the energy up to 70 J having the duration from 50 to 100 ns and the intensity varied in the limits from 108 to 1011 W/cm2; the electron beam providing rate of specific energy deposition up to 1011 J/gs. It is planned to use diagnostic complexes, including thin-film piezoelectric gauges and optical equipment to measure a hydrodynamic response of the tested material to laser pulse with the space and time resolutions, respectively 1-2 mm and 1-5 ns.

To prepare the samples of constructional materials with the various graduated degrees of mechanical and thermal fatigue, it is planned to employ the test benches and technologies of the central laboratories of such leading manufacturers as Leningrad Metal Factory and Izhorsk factories. To create the database on functional relations between a degree of fatigue of the materials and their fundamental physical-mechanical characteristics, it is planned to use the experimental facility of S-PIMASh for the graduated measurements of dependence of the dynamic Young’s modulus and shear modulus on fatigue degree of structural materials. At the same facility of S-PIMASh the character of elastic wave propagation and their dissipation in structural materials with various residual resources will be studied.

Non-destroying character of the suggested methods for control over fatigue is caused by sharply-directed initiation of the elastic-plastic waves, when a small energy of the action on small area of sample is required. So, to excite an elastic-plastic wave by the laser pulse with the duration of 10 ns, the necessary energy of pulse does not exceed 1 J at the area of action not exceeding 0.001 cm2. Let us note that use of the laser with energy less than 1 J as an energy source allows to develop a transportable diagnostic complex for control over materials fatigue for its mobile application at place of construction location.

The Project efforts involves teams of the scientists from Lebedev Physical Institute of RAS (LPI), All-Russia Research Institute of Experimental Physics (RFNC-VNIIEF) and St.-Petersburg Machine-building Institute (S-PIMASh) having rich experience in the fields of physics and technology covered by the subject of Project. Experiments at 20 J laser in LPI and at 70 J laser and electron beam in RFNC-VNIIEF will be performed by the teams of leading Russian experts in the field of the physics of high densities of energy, the physics of shock waves and equation of state of substance. The theoretical researches will be based on the numerical calculations using the wellknown one-dimensional and two-dimensional hydrodynamic codes, including the actual equations of state of substance. Adequacy of these programs has been proved by their long-term successful operation for the investigations of an interaction of powerful flows of energy with matter performed in LPI, RFNC-VNIIEF and some other Institutes. In the theoretical researches it is planned to involve the team of LPI scientists, which is one of leading Russian experts teams in physics of an interaction of laser radiation with matter, the team of the scientists from S-PIMASh, who are the experts in field of the strength properties of the materials of power machine-building, and the team of scientists from RFNC-VNIIEF, who are the leading Russian experts in physics of substance state.

In the Project investigations it is planned to combine the well advanced physical methods for generation of shock and sound waves in solids by the action of powerful pulse sources of energy and large volumes of information on the problem of materials fatigue in applied physics and industry. It should be noted that for the processing of the experimental data on a response of material with various degrees of fatigue to pulse loading, it is planned to use neuronet codes designed by neurocomputer team from LPI, which also participate in the Project. To search the most informative regimes of a pulse excitation of the elastic-plastic waves and to develop the technology of information decoding the fundamental and applied researches for creation of the required database will be carried out in S-PIMASh with participation of the central factory laboratories of the industrial manufacturers.

Project collaborators are ICF Physics and Technology Laboratory of Ente per le Nuove Technologie I’Energia e l’Ambiente (E.N.E.A.) (headed by Professor Angelo Caruso, Italy) and Laboratoire pour Application and Lasers de Puissance of Centre Laser Franco-Allemand (CLFA) (headed by Professor Remy Fabbro, France). The first Laboratory is one of the most known European scientific teams in the field of interaction of laser radiation with matter and technology of laser processing of materials. Experimental researches in this Laboratory are performed with use of a neodymium laser with energy of 100 J. The second Laboratory is one of the leading European scientific teams in the field of technological applications of lasers. Experimental researches in this Laboratory are performed with use of various lasers, including the neodymium laser with energy of about 60 J. The both Laboratories perform experimental and theoretical researches in area of excitation and distribution of hydrodynamic perturbations in the solidls under the action of laser pulse, as well as in the field of physics of equation of state of substance. The role of collaborators in the Project will consist in the discussions on a formulation of problems in particular areas of Project subject, exchange of scientific information, and the discussion of investigation results, as well as in participation in the experiments and numerical calculations jointly with the Russian participants of Project.

Innovations under the Project framework will include:

– new knowledge on propagation of the elastic-plastic waves in solids, including the constructional materials, which were subjected to loading; new knowledge in the field of equation of state of substance and the physical nature of material fatigue;

– development of physical principles of the methods for non-destroying control over materials fatigue, including those associated with small-scale fractures of structure;

– creation of the database on the fatigue curves for various materials, and the filling of a gap between the known models of tired materials and the data on fatigue curves, which will be obtained under the Project framework.


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