IFMASS10

components EKL and engineering stress components are known, then all tensorial

quantities and invariants are calculated.

–

Constitutive modelling by Johnson-Cook (JC) /30/, Armstrong-Zerilli (AZ) /27/ and

simplified Zener-Hollomon (ZH) models, are improved to include higher strain rates.

–

A manifold of existent localization criteria like McClintock's, Hill-Korhonen's,

Marciniak-Kuczynski is applied to same real materials (mainly aluminium killed steel)

as well as some hypothetical materials. A special attention is paid to Gurson's fracture

criterion which allowed for higher values of fracture strains than found by experiments.

It should be noted, however, that in recent research of M.M. with coworkers these

strains are significantly smaller when thermal effects are taken into account.

Some additional conclusions are also have to be considered:

–

Manjoine's triaxiality

, which accounts also on trace of stress tensor, is one of the most

important analytical parameters for damage characterization and monitoring.

–

Identification of constitutive models based on the associate flow rule, as (JC), (AZ) and

(ZH) model may be considered as successful since all the models permitted calibration

of separate as well as simultaneous consideration of groups

and

. Such an ability

originated from the fact that a linear relationship between equivalent plastic strain rate

and equivalent stress rate

ሶ

௣ ௘௤

ൌ ݁

݌ሺെࣨሻ

ሶ

௘௤

has been found and the corresponding

universal material constant

ࣨ

calibrated. It is called “universal” since its value does not

depend on constitutive model chosen for the analysis. Another “universality”

introduced by relationships of the type

௘௤

ൌ Φ൫

௉ ௘௤

ߝ ,

ሶ

௣ ௘௤

൯

fails. It had been shown that

AZ-approach based on dislocation mechanics is superior over the others two.

–

The model based on tensor functions has shown its superiority far above all the

mentioned models even in its simplest version with only three material constants. Not

only its highest correlation coefficients but its best qualitative agreement with

experiments was very good. Such a model has been shown to be solely able to cover

small, medium and high strain rates at shear, unitension by traditional cylindrical

specimen as well as bitension by cruciform specimen tests /34/, whereas all traditional

associate flow rule models with“universal” flow rule assumption failed.

Let us note at the end of this review that for the sake of brevity non-proportional stress

histories given in /4/ are not included here. As mentioned in the introduction they are very

important for all plastically deforming real structures.

REFERENCES

Reviews on ductile fracture criteria

Dodd, B. and Bai, Y. (1987): Ductile Fracture and Ductility, London, Academic Press.

2. McClintock, F. A. (1971):

Plasticity Aspects of Fracture

, in: Liebowitz. H., (ed.), Fracture,

Academic Press, Vol.III, pp. 48-227.

3. Manjoine, M. J. (1971):

Multiaxial stress and fracture

, in: Liebowitz. H.,(ed.),

Fracture,Academic Press, Vol.III, pp. 265-309.

4. Mićunović, M.

Study of Ductile Failure Criteria Under Multiaxial Loading

, Contract No5364-

93-06 ED ISP YU, Final Report, JRC CEC - Ispra, Italy 1999.

5. Mićunović, M.

Study of Ductile Failure Criteria UnderMultiaxial Loading

(Biaxial

HopkinsonTests), Contract No 5364-93-06 ED ISP YU, Final Report, JRC CEC - Ispra, Italy

Experimental papers dealing with ductile fracture

Albertini, C. (1994):

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