Observation of kink shear bands in an aluminium single crystal fracture specimen

Patil, Swapnil; Narasimhan, R.; Mishra, Raja K.

doi:10.1016/j.scriptamat.2009.04.043

Cited by 31 publications

(22 citation statements)

References 14 publications

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“…Further, the stress distribution corresponding to each member of these families, as well as the trajectory in stress plane as the crack tip is traversed agree well with those computed from finite element analysis for a certain value of T -stress. It must be noted that both families of analytical solutions proposed in this work, have a kink sector boundary at θ = 90 • , in conformity with the experimental observations of Patil et al (2008bPatil et al ( , 2009) for aluminum single crystal specimens. The possible reasons why this kink shear band was not detected in the experiments of Shield (2001, 2003), Crone et al (2004) as well as in the discrete dislocation simulations of Van der Giessen et al (2001) are discussed.…”

Section: Introductionsupporting

confidence: 89%

“…It must be noted that both families of solutions suggested in this work (Fig. 4a, b) involve a kink sector boundary at θ = 90 • which has been observed from EBSD maps by Patil et al (2008bPatil et al ( , 2009) in aluminum single crystal specimens.…”

Section: Construction Of Families Of Asymptotic Solutions For Stationsupporting

confidence: 73%

“…On the other hand, a more robust way of detecting kink shear bands is by using EBSD as demonstrated by Kysar and Briant (2002) and Flouriot et al (2003). Indeed, the recent in-situ EBSD results of Patil et al (2009) clearly show lattice rotation bands in aluminum single crystal specimens developing from the notch surface at θ = ±90 • to the notch line. Further, as mentioned by Rice (1987), the formation of kink shear bands requires adequate internal dislocation sources.…”

Section: Discussionmentioning

confidence: 99%

“…However, the finite element analysis of Patil et al (2008a), while confirming the existence of such a sector, suggests a different type of trajectory in stress plane as the crack tip is traversed in contrast to that assumed by Drugan (2001). Furthermore, recent experimental studies by Patil et al (2008bPatil et al ( , 2009) using single edge notched (tensile) and three point bend specimens, respectively, of aluminum single crystals having the orientation considered by Rice (1987) have shown the existence of kink shear bands at θ = ±90 • . These studies employed in-situ Electron Back Scattered Diffraction (EBSD) observations to detect lattice rotation bands near the notch tip.…”

Section: Introductionmentioning

confidence: 88%

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Families of asymptotic tensile crack tip stress fields in elastic-perfectly plastic single crystals

2009

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In this work, two families of asymptotic near-tip stress fields are constructed in an elastic-ideally plastic FCC single crystal under mode I plane strain conditions. A crack is taken to lie on the (010) plane and its front is aligned along the [101] direction. Finite element analysis is first used to systematically examine the stress distributions corresponding to different constraint levels. The general framework developed by Rice (Mech Mater 6:317-335, 1987) and Drugan (J Mech Phys Solids 49:2155-2176, 2001) is then adopted to generate low triaxiality solutions by introducing an elastic sector near the crack tip. The two families of stress fields are parameterized by the normalized opening stress (τ A 22 /τ o ) prevailing in the plastic sector in front of the tip and by the coordinates of a point where elastic unloading commences in stress space. It is found that the angular stress variations obtained from the analytical solutions show good agreement with finite element analysis.

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Section: Introductionsupporting

confidence: 89%

Section: Construction Of Families Of Asymptotic Solutions For Stationsupporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 88%

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Families of asymptotic tensile crack tip stress fields in elastic-perfectly plastic single crystals

2009

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“…In their solution structure, kink sector boundaries (especially the one at 90°to the crack line) are not present, but instead elastic sectors are incorporated in the near-tip field. Interestingly, in a recent work, Patil et al (2009b) performed in-situ EBSD mapping of a three point bend (TPB) aluminum single crystal fracture specimen and found the occurrence of these kink shear bands. It must be mentioned that all the above studies are limited to high constraint single crystal fracture geometries only.…”

Section: Introductionmentioning

confidence: 99%

Effect of loading rate on crack tip fields in three point bend fracture specimen of FCC single crystal

Biswas

Narasimhan

2011

International Journal of Solids and Structures

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Keywords:Ductile FCC single crystal Crack tip fields Loading rate Three point bend specimen Finite element analysis a b s t r a c t In this work, the effect of impact loading on mode I stationary crack tip fields in a three point bend FCC single crystal fracture specimen is investigated using plane strain finite element analysis. The behavior of the single crystal is assumed to be elastic-perfectly plastic. The main objective is to examine the role of material inertia in influencing the stress levels as well as the pattern of slip and kink shear bands around the tip. The results show that under quasi-static loading high stress levels prevail ahead of the notch tip. However, the specimen suffers considerable loss of constraint under dynamic loading, particularly during the initial stages. This increases with loading rate _ J. Also significant spread of the plastic zone occurs in the forward sector ahead of the tip under impact loading which is akin to isotropic solids. The pattern of shear bands around the tip in the single crystal also changes with impact velocity. In rate dependent single crystals, a competition between rate sensitivity and material inertia is observed. Thus, while the former enhances the stresses near the tip, the latter tends to reduce them.

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Finite element simulations of notch tip fields in magnesium single crystals

2014

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Recent experiments using three point bend specimens of Mg single crystals have revealed that tensile twins of {1012}-type form profusely near a notch tip and enhance the fracture toughness through large plastic dissipation. In this work, 3D finite element simulations of these experiments are carried out using a crystal plasticity framework which includes slip and twinning to gain insights on the mechanics of fracture. The predicted load-displacement curves, slip and tensile twinning activities from finite element analysis corroborate well with the experimental observations. The numerical results are used to explore the 3D nature of the crack tip stress, plastic slip and twin volume fraction distributions near the notch root. The occurrence of tensile twinning is rationalized from the variation of normal stress ahead of the notch tip. Further, deflection of the crack path at twin-twin intersections observed in the experiments is examined from an energy standpoint by modeling discrete twins close to the notch root.

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Observation of kink shear bands in an aluminium single crystal fracture specimen

Cited by 31 publications

References 14 publications

Families of asymptotic tensile crack tip stress fields in elastic-perfectly plastic single crystals

Families of asymptotic tensile crack tip stress fields in elastic-perfectly plastic single crystals

Effect of loading rate on crack tip fields in three point bend fracture specimen of FCC single crystal

Finite element simulations of notch tip fields in magnesium single crystals

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