Numerical fracture mechanics as a practical failure investigatory tool: The outlook of cracked round bars

Teh, S.; Akbar, Aditya N.; Andriyana, Andri; Ramesh, S.; Putra, Ichsan Setya; Riyandwita, Byan Wahyu; Manurung, Auralius; Kadarno, Purwo; Purbolaksono, J.

doi:10.1016/j.engfailanal.2021.105630

Cited by 4 publications

(1 citation statement)

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“…blunt crack), researchers are working on correction factors to account for the deviations that result from linear elastic fracture mechanics (LEFM) predictions. 1 Although literature is abundant on the use of finite element method to predict SIF, 2 most work focused on comparing finite element predictions and those from LEFM on sharp crack, and often not complemented by experimental observations. Also, some modelling techniques require manual node adjustment (i.e.…”

Section: Introductionmentioning

confidence: 99%

Modelling mode I failure at crack tip with verifications using digital image correlation

2021

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Background: Linear elastic fracture mechanics (LEFM) applies to sharp cracks, although crack sites such as holes and slots are often blunt cracks with nonzero widths. The advancement in finite element method (FEM) has enabled the calculation of stress intensity factor (SIF) for unstable crack growth prediction, regardless of crack shape and size, but the calculations often differ from contour to contour. Hence, the purpose of this work is to determine if SIFs computed using commercial FEM have experimentally verifiable advantages over the traditional stress-based modelling approaches in predicting Mode I brittle failure at blunt crack tip. Methods: Experiments and simulations were conducted on brittle Poly(methyl methacrylate) (PMMA) plastic to compare the actual and predicted strain fields and SIFs at crack tip, and the critical force at which unstable crack growth initiates. A centrally straight cracked Brazilian disc made of PMMA was subjected to purely Mode I fracture. Its strain fields were measured from deformed speckle patterns using digital image correlation software. The same disc was modelled using plane stress model in FEM. By applying the critical force, SIFs were then computed using ANSYS pre-meshed crack method at different contours away from the crack tip. The effects of element type, mesh size and crack width on the simulated SIFs were investigated. Results: It was found that the experimental critical load agreed well with LEFM prediction based on PMMA fracture toughness in published literature. Disc failure happened at the first sign of tensile yield at the crack tip in the finite element model with a triangle mesh. Digital image correlation clearly shows the occurrence of unstable crack growth at critical force. It also shows comparable far field strain responses to the FEM model. Conclusions: The computed SIFs were inconsistent, and their usefulness in predicting unstable crack growth requires further investigation.

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Section: Introductionmentioning

confidence: 99%