Abstract
The present study addresses determination of the plastic “eta factor” \(\eta _{p}\) for single edge notched tensile (SENT) specimens of an interstitial-free (IF) steel sheet (thickness \(=\) 1 mm) for crack depth ratios in the range of 0.2 to 0.9. Two well-established \(\eta _{p}\) determination methods for thick fracture mechanics specimens proved adequate for the present purpose. Analyses using load-displacement data from mechanical tests and also from 3-D finite element simulations were used to verify the applicability of one of these adopted methods up to extensive crack tip necking even beyond crack initiation. Further analyses indicate that \(\eta _{p}\) thus determined (i) can be used for fatigue pre-cracked sheet specimens, and (ii) is consistent with the contour integral definition of J integral. Use of \(\eta _{p}\) thus determined for measuring initiation fracture toughness in notched specimens is also illustrated.
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Abbreviations
- \(A_{P}\) :
-
Plastic component of work done
- a :
-
Notch/crack length
- \(C_{M}, \,C_{S}\) :
-
Machine elastic compliance, specimen elastic compliance
- \(E,E^{'}\) :
-
Youngs modulus, effective elastic modulus
- H :
-
Free length of specimen between the two jaw grips
- \(J_{c}J_{p}^{c}\) :
-
Critical value of the Jintegral, \(J_{p}\) at crack initiation
- \({J;J}_{e}, J_{p}\) :
-
J integral parameter; elastic, plastic component of J
- \(J_{p}^{max}\) :
-
Maximum value of path independent contour J integral for fixed z computed with the adopted FE meshing
- K :
-
Stress intensity factor
- l :
-
Specimen ligament length
- \(\rho \) :
-
Notch root radius
- z :
-
Distance from specimen surface in the thickness direction
- n :
-
Hollomon strain hardening parameter
- P :
-
Load
- \(S_{k}\) :
-
Load separation factor (Eq. 7)
- \(t, \, t_{n}\) :
-
Sheet specimen thickness, ligament width at neck
- \(v_{p}\) :
-
Specimen plastic displacement
- \(v_{a}, \, v_{s}\) :
-
Actuator displacement, specimen free length (H) extension
- W :
-
Specimen width
- \(\delta \) :
-
Crack tip opening displacement (CTOD)
- \(\delta _{c}\) :
-
Critical value of \(\delta \) for crack initiation
- \(\eta _{p}\) :
-
Plastic “eta factor”
- CTOD:
-
Crack tip opening displacement
- DENT:
-
Double-edge notched tension
- FE:
-
Finite element
- IF:
-
Interstitial free
- SENT:
-
Single-edge notched tension
- \(A_{M}, G\left( \frac{l}{W} \right) H\left( \frac{v_{p}}{W} \right) \) :
-
constant, functions in Eq. (4)
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Acknowledgements
Authors acknowledge that the experimental research has been done in the DST-FIST sponsored equipment (Grant Sanction No. SR/FST/ETI-404/2015(c)). Authors also acknowledge TATA Steel Ltd., Jamshedpur, India for providing the required steel that has been used in the present research.
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Chandra, S.K., Sarkar, R., Choudhury, S. et al. Determination of \(\varvec{\eta }_{{\varvec{p}}}\) factor for clamped SENT thin sheet specimens of an Interstitial Free steel. Int J Fract 227, 137–152 (2021). https://doi.org/10.1007/s10704-020-00493-9
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DOI: https://doi.org/10.1007/s10704-020-00493-9