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Blackman, B. R. K.
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Blackman, B. R. K.
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Blackman, B. R. K.
Research Output
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Publication
Mode-mixity in Beam-like Geometries: Linear Elastic Cases and Local Partitioning
2012, Blackman, B. R. K., Conroy, Mark, Ivankovic, Alojz, et al.
This work is conducted as a part of a wider international activity on mixed mode fractures in beam-like geometries under the coordination of European Structural Integrity Society, Technical Committee 4. In its initial phase, it considers asymmetric double cantilever beam geometry made of a linear elastic material with varying lower arm thickness and constant bending moment applied to the upper arm of the beam. A number of relevant analytical solutions are reviewed including classical Hutchinson and Suo local and Williams global partitioning solutions. Some more recent attempts by Williams, and Wang and Harvey to reproduce local partitioning results by averaging global solutions are also presented. Numerical simulations are conducted using Abaqus package. Mode-mixity is calculated by employing virtual crack closure technique and interaction domain integral. Both approaches gave similar results and close to the Hutchinson and Suo. This is expected as in this initial phase numerical results are based on local partitioning in an elastic material which does not allow for any damage development in front of the crack tip.
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Publication
Modelling the Fracture Behaviour of Adhesively-Bonded Joints as a Function of Test Rate - A Rate Dependent CZM is Required to Predict the Full Range of Behaviour
2011, Ivankovic, Alojz, Karac, Aleksandar, Blackman, B. R. K., et al.
Adhesive bonding of lightweight, high-performance
materials is regarded as a key enabling technology for the
development of vehicles with increased crashworthiness,
better fuel economy and reduced exhaust emissions. However,
as automotive structures can be exposed to impact
events during service, it is necessary to gain a sound understanding
of the performance of adhesive joints under
different rates of loading. Therefore, characterising the
behaviour of adhesive joints as a function of loading rate is
critical for assessing and predicting their performance and
structural integrity over a wide range of conditions.
The present work investigates the rate-dependent behaviour
of adhesive joints under mode I loading conditions.
A series of fracture tests were conducted using tapered
double-cantilever beam (TDCB) specimens at various
loading rates [1-2]. The experiments were analysed
analytically and numerically. The full details of the analysis
strategy employing analytical approaches for different
types of fracture are presented in [1]. The numerical modelling
of the TDCB experiments was performed using the
finite-volume based package ‘OpenFOAM’ [3].
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Publication
Modelling the fracture behaviour of adhesively-bonded joints as a function of test rate
2011-04, Karac, Aleksandar, Blackman, B. R. K., Cooper, V., et al.
Tapered-double cantilever-beam joints were manufactured from aluminium-alloy substrates bonded together using a single-part, rubber-toughened, epoxy adhesive. The mode I fracture behaviour of the joints was investigated as a function of loading rate by conducting a series of tests at crosshead speeds ranging from 3.33 × 10−6 m/s to 13.5 m/s. Unstable (i.e. stick–slip crack) growth behaviour was observed at test rates between 0.1 m/s and 6 m/s, whilst stable crack growth occurred at both lower and higher rates of loading. The adhesive fracture energy, GIc, was estimated analytically, and the experiments were simulated numerically employing an implicit finite-volume method together with a cohesive-zone model. Good agreement was achieved between the numerical predictions, analytical results and the experimental observations over the entire range of loading rates investigated. The numerical simulations were able very readily to predict the stable crack growth which was observed, at both the slowest and highest rates of loading. However, the unstable crack propagation that was observed could only be predicted accurately when a particular rate-dependent cohesive-zone model was used. This crack-velocity dependency of GIc was also supported by the predictions of an adiabatic thermal-heating model.