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Engineering Materials and Structures (Dynamic, high strain rate, or impact fracture)

Organizer: Professor S. Vodenicharov

Abstracts

1. Influence of neutron irradiation on partition impact fracture energies of reactor pressure vessel steel.

Abstract: In process of work, the reactor pressure vessel metal is ageing under neutron irradiation. That’s why it is necessary to do some periodical control of mechanical characteristics by so called “surveillance-specimens”.

The three point bending impact test of “surveillance-specimens” is using to determinate the temperature dependence of absorbed impact energy Cv according to Standard surveillance program for nuclear reactors WWER-1000.

The aim of work is to be found some other criterion for assessment the rate of embrittelment of reactor pressure vessel weld metal. By detailed analyze of “force-displacement” diagram and determinate three partition energies, corresponding to initiation crack (A), stable and unstable propagation crack (B) and arrest-crack energy (C) receive some additional information about neutron irradiation.

Corresponding Author: Svetoslava Petkova

Corresponding author address: Institute of Metal Science, 67 Shipchenski prohod str., 1574 Sofia Bulgaria

Phone:+359(2) 7142335 FAX:+359(2) 9733970 E-mail: sv_petkova@yahoo.com

Co-authors names, affiliations & country: researcher, Bulgaria

2. Investigation of fracture mechanisms of high nickel WWER 1000 weld metal under three point impact loading

Abstract: The fracture mechanisms governed impact fracture of WWER 1000 reactor pressure weld metal at different test temperature was studied. The material was investigated in unirradiated and irradiated state. The fracture morphology of specimens fractured at upper shelf energy, transition zone and low shelf energy of Charpy curve was studied by scanning electron microscope. No changes of the main fracture mechanisms after irradiation were established. The intercrystal brittle fracture was observed in unirradiated and irradiated metal state. The temperature dependence of relative part of ductile fracture on the fractured surface of specimens was determined quantitatively. A linear correlation of ductile relative part with normalized fracture energy of WWER1000 weld metal was established.

Corresponding Author:

Corresponding author address: Institute of Metal Science, 67 Shipchenski prohod str., 1574 Sofia Bulgaria

Phone:+359(2) 7142373 FAX:+359(2) 9733970 E-mail: nemak@gbg.bg

Co-authors names, affiliations & country: researcher, Bulgaria

3. Assessment of dynamic fracture toughness of reactor steels by using sub-sized specimens

Abstract: The basic priority to use sub-sized specimens for assessment of embrittelment of reactor steels, is using a small part of volume of the material. Usually the sub-sized specimens are made from half of already tested specimens or templates, cutting form reactor corpus with dimension 7x60x95mm.

There are two methods for correlation of data from impact testing between sub-sized and standard Charpy specimens. First method is based of standardized absorbed impact energy. To this end is determine empirical correlation between USE of standard specimens 10x10x55mm and USE of sub-sized specimens, based on great number of experiments. The second methods is consist of empirical correlation of brittle temperature values Tk between sub-sized specimens and standard ones.

Corresponding Author: Martin Lolov

Corresponding author address: Institute of Metal Science, 67 Shipchenski prohod str., 1574 Sofia Bulgaria

Phone:+359(2) 7142373 FAX:+359(2) 9733970 E-mail: oldmarti@mail.bg

Co-authors names, affiliations & country: researcher, Bulgaria

4. Fracture toughness determination of reactor pressure vessel steel

Abstract: Brittle fracture in the ductile to brittle transition regime is connected with specimen size effects. The size effects have the consequence that fracture toughness data obtained from small laboratory specimens do not directly describe the fracture behavior of real flawed structures.

Intensive research has been conducted in the last decade in order to overcome these problems. Different approaches have been developed and proposed, one of the most promising being the master curve method.

The master curve method provides a description for the fracture toughness scatter, size effect and temperature dependence both for the transition region as well as the lower shelf.

For validation purposes, reactor pressure vessel (RPV) steel JRQ has been extensively characterized with fracture toughness testing. The tests have been performed on standard geometry SE(B) specimens.

Corresponding Author: Pavel Eskenazi

Corresponding author address: Institute of Metal Science, 67 Shipchenski prohod str., 1574 Sofia Bulgaria

Phone: +359(2) 7142545 FAX:+359(2) 9733970 E-mail: eskenazi@bigfoot.com

Co-authors names, affiliations & country: researcher, Bulgaria

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