Papers by Alojz Ivanković
Dynamic fracture of advanced ceramics under impact loading conditions using a
Composite Structures, 2021
Composite Structures, 2021
Composites Part A: Applied Science and Manufacturing, 2020
Carbon fibre reinforced poly-etherether-ketone (PEEK) and poly-phenylene-sulfide (PPS) composites... more Carbon fibre reinforced poly-etherether-ketone (PEEK) and poly-phenylene-sulfide (PPS) composites were rapidly surface-treated by high-power UV light, and then adhesively bonded to aluminium 2024-T3 and carbon fibre/epoxy composites. The results of a single lap-shear joint test demonstrated that a UV-treatment lasting for 5 s was sufficient to prevent joint failure occurring at the composite/adhesive interfaces in all cases, e.g. it increased the failure strength of the PPS composite/aluminium joints from 11.1 MPa to 37.5 MPa. Moreover, the composite/adhesive interfaces performed well upon an exposure of the joints to an environment of high humidity and temperature for 8 weeks. Additionally, an investigation lasting for 6 months showed no degradation of the surface functionalisation from UV-irradiation. Overall, this work highlights high-power UV-irradiation a very promising method for surface preparation of thermoplastic composites (TPCs) for adhesive joining, i.e. TPC adhesive joints with excellent structural integrity can be obtained by using this rapid, eco-friendly and low-cost surface-treatment method.
European Structural Integrity Society, 2003
ABSTRACT Drop impact resistance of fluid-filled plastic containers is of considerable concern to ... more ABSTRACT Drop impact resistance of fluid-filled plastic containers is of considerable concern to containers manufacturers as well as distribution industries using the containers for transportation of various liquids. This is due to potential failure of the containers following the drop impact and subsequent spillage of the transported liquid, and consequent safety and economical issues. In this work, a series of drop impact experiments is conducted on water filled bottles made of blow moulded high-density polyethylene (HDPE). During experiments, pressure and strain histories are recorded at various positions. The experiments are then simulated numerically.This problem falls into a category of strongly coupled fluid-structure interaction (FSI) problems due to comparable stiffnesses of the container and its liquid content. Hence, accurate prediction of containers' behaviour requires a liquid-container interaction model. Here, a two-system FSI model based on the Finite Volume Method is employed, and a good agreement is found between measured and predicted pressure and strain histories.To obtain fracture properties of HDPE conventional essential work of fracture tests are performed. Two grades of blow-moulded HDPE are tested at different test speeds. The main aim of these tests is to estimate traction-separation (cohesive zone) properties of the materials. In future work, these will be combined with the fluid-structure interaction model to provide a powerful tool for predicting the complex behaviour and potential failure of fluid-filled containers under drop impact.
Key Engineering Materials, 2009
Polycrystalline Cubic Boron Nitride (PCBN) is a superhard material which is used in machining of ... more Polycrystalline Cubic Boron Nitride (PCBN) is a superhard material which is used in machining of hardened steels and other abrasive and aerospace grade alloys. In these applications the tools are subjected to high operating temperatures, abrasive and impact loading. Impact loading can lead to the sudden fracture and hence failure of the tool. In this work the static and dynamic fracture toughness of PCBN is determined via a combined experimental-numerical approach. The results show that the fracture toughness of PCBN varies with loading rate.
Polymer, 2012
The current work is a combined experimental-numerical study of the fracture behaviour of a nano-t... more The current work is a combined experimental-numerical study of the fracture behaviour of a nano-toughened, structural epoxy adhesive. The mode I fracture toughness of the adhesive is measured using tapered double-cantilever beam (TDCB) tests with various bond gap thicknesses ranging from 0.25mm-2.5mm. Circumferentially deep-notched tensile specimens are independently employed to measure the cohesive strength of the adhesive as a function of constraint. The experimental TDCB test results are predicted numerically for each bond gap thickness using the Finite Volume method and a Dugdale cohesive zone model. A unique relationship between the fracture energy and the constraint level is established. The effect of bond gap thickness on the fracture behaviour of TDCB joints is hence directly attributed to the variation of the intrinsic fracture energy with constraint and thickness. Using the well known Rice and Tracey void growth model, a link is established between the voids observed in the fracture process zone, the constraint imposed by the thickness of the adhesive and the resulting fracture energy.
Numerical Heat Transfer, Part B: Fundamentals, 2005
ABSTRACT This article presents a development of the finite-volume method for solving linear therm... more ABSTRACT This article presents a development of the finite-volume method for solving linear thermoviscoelastic deformation problems. Hereditary continuum problems represented by spatially elliptic second-order partial differential equations with memory are considered. This is motivated by the need to develop numerical algorithms for the solution of thermoviscoelastic stress analysis problems, although it is expected that results presented will generalize to other Volterra problems. Assuming that the hydrostatic and deviatoric responses are uncoupled, and using the temperature–time equivalence hypothesis, the constitutive equations are expressed in an incremental form. Procedures for analyzing linear viscoelastic deformation are described, and numerical examples are given to demonstrate the effectiveness of the model and the numerical algorithms. The accuracy of the method is demonstrated through comparison with analytical and experimental results as well as with numerical solutions obtained elsewhere.
Journal of the European Ceramic Society, 2012
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Journal of Biomechanics, 2008
Journal of Biomechanics, Volume 41, Issue null, Pages S353, July 2008, Authors:Hamid Khalili Pars... more Journal of Biomechanics, Volume 41, Issue null, Pages S353, July 2008, Authors:Hamid Khalili Parsa; Alojz Ivankovic; Aleksandar Karac.
Journal of Biomechanics, 2009
International Journal of Impact Engineering, 2009
In this work, the behaviour of fluid-filled plastic containers under base drop impact is investig... more In this work, the behaviour of fluid-filled plastic containers under base drop impact is investigated using a combined experimental/numerical approach. In addition, theoretical predictions from two approaches, waterhammer theory and a mass-spring model, are also given. Experimental tests are conducted using a specially designed rig for testing plastic containers (bottles). Tested containers are fully instrumented with pressure transducers and strain gauges. The experiments are simulated using a two-system fluid-structure interaction procedure based on the Finite Volume Method. Good agreement is found between measured and predicted pressure and strain histories. Results obtained are in favour of waterhammer theory.
Engineering Fracture Mechanics, 2011
Engineering Fracture Mechanics, 2013
Numerical modelling of a series of experimental Single Edge V-Notched Beam tests was carried out ... more Numerical modelling of a series of experimental Single Edge V-Notched Beam tests was carried out for a number of grades of polycrystalline cubic boron nitride using the finite volume method (FV) and cohesive zone model approach. The effect of notch root radius observed experimentally was reproduced numerically via a unique CZM for each material examined. It was also found that the shape of the cohesive zone model can be significant, especially when the material has a relatively high fracture energy. It was also demonstrated that the experimentally observed drop in fracture toughness with increase in test rate was not explainable in terms of the system dynamics. It was found that in order to predict the experimental fracture loads for a range of loading rates, it was necessary to modify the CZM in such a way as to preserve the micro-structural length scale information of the material embedded within the CZM.
International Journal of Refractory Metals and Hard Materials, 2015
ABSTRACT A systematic study of the residual stress distribution in number of poly- crystalline di... more ABSTRACT A systematic study of the residual stress distribution in number of poly- crystalline diamond grades was performed using Raman spectroscopy. The analysis focuses on evaluating the stress state in the specimen both before and after oil quench treatment, with a particular emphasis on the role of the second phase material. Prior to heat treatment, measurements along the surface of the specimen indicate an average residual stress in excess of 1.5 GPa for all grades examined. For specimens subjected to oil quenching at 600 °C an increase in the presence of tensile stress was recorded. Removal of the cobalt second phase from the surface of the microstructure had the effect of limiting this increase of tensile stresses on the specimen surface. Numerical modelling of the quench experiment was performed for polycrystalline diamond using the finite volume method (FV). The increase in residual stress, observed experientially after oil quenching was reproduced numerically, validating the experimental approach for approximating the stress distribution on the surface of the specimens.
Composites Science and Technology
Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine
A patient-specific numerical model of the ankle joint has been developed using open-source softwa... more A patient-specific numerical model of the ankle joint has been developed using open-source software with realistic material properties that mimics the physiological movement of the foot during the stance phase of the gait cycle. The patient-specific ankle geometry has been segmented as a castellated surface using 3DSlicer from the computed tomography image scans of a subject with no congenital or acquired pathology; subsequently, the bones are smoothed, and cartilage is included as a uniform thickness extruded layer. A high-resolution Cartesian mesh has been generated using cfMesh. The material properties are assigned in the model based on the CT image Hounsfield intensities and compared to a sandwich-based material model. Gait data of the same subject was obtained and used to relatively position the tibia, talus, and calcaneus bones in the model. The stance phase of the gait cycle is simulated using a cell-centred finite-volume method implemented in open-source software OpenFOAM. T...
International Journal of Adhesion and Adhesives
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Papers by Alojz Ivanković