STUDY OF THE DYNAMIC FRACTURE TOUGHNESS OF SUBMARINE HULL STEELS

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Authors
  1. Bassim, M.N.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN);Manitoba Univ, Winnipeg MAN (CAN)
Abstract
This report describes results of fracture toughness studies performed on high strength low alloy steels used in ship and submarine structures as a function of temperature and loading rates. Very high strain rates, up to 10 super 6 K (where K is the variation of the stress intensity factor with time) were obtained by using a specially designed swing arm Split Hopkinson Bar (SHB) system. The study emphasized particularly the use of the stretch zone width to characterize the fracture toughness. This stretch zone is usually measured using scanning electron microscopy. The program involved specifically four tasks as follows: (i) study of the evolution of blunting lines as a function of temperature and loading rates, (ii) evaluation of the fracture transition curve for CT specimens using total energy analysis, stretch zone width and measurement of the shear lips, (iii) evaluation of the stretch zone for samples supplied by DREA and (iv) study the effect of fatigue prestraining on the deformation of the stretch zone. Tests were performed at 25C and at -30C. Also examined was the strain distribution ahead of the crack tip using neutron diffraction techniques. The results show the importance of using stretch zone width for evaluation of the fractue toughness and also establish the various factors which may influence the extent of the stretch zone width.
Keywords
Split Hopkinson Bar system;Stretch zone;Shear lips
Report Number
DREA-CR-95-423 — Contractor Report
Date of publication
01 Apr 1995
Number of Pages
75
DSTKIM No
95-02925
CANDIS No
152128
Format(s):
Document Image stored on Optical Disk;Hardcopy

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