Fracture Toughness for

57
I N-97/505 IL0006640 iv s .n ,Dip .1 1998 >MQ- Fracture Toughness for Materials of Low Ductility S. Baralay, U.Karp, M. Perl May 1998 English, abstract included ISRAEL ATOMIC ENERGY COMMISSION, NUCLEAR RESEARCH CENTRE - NEGEV 3 1/23

Transcript of Fracture Toughness for

Page 1: Fracture Toughness for

IN-97/505

IL0006640

iv

s .n ,Dip .1

1998 >MQ -

Fracture Toughness forMaterials of Low Ductility

S. Baralay, U.Karp, M. Perl

May 1998

English, abstract included

ISRAEL ATOMIC ENERGY COMMISSION, NUCLEAR RESEARCHCENTRE - NEGEV

3 1 / 2 3

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nil IUII III m mi IIII ii.ii mi inn n mi

IL0006640

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Fracture Toughness of Loifr Ductility Materials

S. Barzilai, B. Karp, M. Perl

May 1998

Abstract *

The results of a survey of methods for evaluating fracture toughness

characteristics for semi-brittle and brittle materials are presented in this report.

These methods differ considerably from those used for ductile materials by the

specimen configurations, the methodology of the experiments and by the

problems occurring while using these methods.

The survey yields several important findings!

A.It is possible to create steady state crack growth by cyclic loading in several

semi-brittle materials.

B.The need for pre-cracking is not yet clear, nevertheless it is recommended

to evaluate fracture toughens with pre-cracked specimen.

C.As crack length and ligament size may effect fracture toughness results it is

necessary to define minimum specimen dimensions to avoid this effect.

D.The specimen thickness hardly affects the fracture toughens.

E.Loading rate for the test is not well defined. It is commonly accepted to end

the test in one minute.

F.The main mechanism that causes inelastic deformation in semi-brittle

materials is related to the generation of micro-cracks.

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Atkinson B.K., (1980) "Subcritical Crack Propagation in Rocks: Theory, ExperimentalResults and Applications", International Geological Congress, pp. 41-56. Paris.

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K CALIBRATIONS FOR TYPICALFRACTURE TOUGHNESS AND

FATIGUE CRACK PROPAGATIONTEST SPECIMENS

Type Stress Intensity Formulation Configuration

1. Compactspecimen"C(T)

2. Disk-shapedcompactspecimen"DC(T)

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(2 + aAV)where/( = ( ;_^[0 .1

-\2.32(aAV)2

K "

3. Wedgeopeningloadedspecimen*(WOL)

wheref(aAV) =

ts

BWla

+ 4.64a/W

(2 + aAV)[0.8072 + 8.858(o/W)

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4. Center-crackedtensionspecimen11

(CCT)

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SE(B)

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- 0.41(a/W)

" ASTM Standard E 399-81, Annual Book ofASTM Standards, Part 10, 1981.b A. Saxena and S. Hudak. Int. J. Fract. 14, 453 (1978).c C. E. Feddersen, ASTM STP 410, 1976. p. 77.dB. Gross. J. Srawley, and W. F. Brown, Jr., NASA Tech. Note D-2395, NASA, Aug. 1964.

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