Investigating the behaviour of fluid-filled polyethylene containers under base drop impact: A combined experimental/numerical approach

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.Deposited by bulk impor

Characterisation of a surrogate lung material made of polyurethane foam and fluid-filled gelatine microcapsules

1st International Conference on Computational and Mathematical Biomedical Engineering (CMBE09), Swansea, UK, June 29 - July 1, 2009In this study, a surrogate lung material, developed to mimic the lungs behaviour in low and high rate impact tests in order to better understand the damage mechanism in the lungs resulting from car crashes, collisions and explosion [1], is tested and characterised. This aims to eliminate the practice of live animal testing. The surrogate lung consists of polyurethane foam mixed with gelatine microcapsules filled with Barium Sulphate solution. Thus, both the foam and microcapsules must be individually characterised in addition to the surrogate lung itself when treated as a continuum material. For this, a number of compression tests were carried out on each material to ascertain their mechanical properties. On the other hand, the damage to the surrogate lung specimens as represented by burst microcapsules was analysed by carrying out CT scans before and after testing. The results show that the modulus of elasticity increases with the test speed. CT scan results clearly demonstrated the magnitude and distribution of damage within the specimen.Deposited by bulk importkpw11/10/1

Development of a finite volume contact solver based on the penalty method

This paper describes the development and application of a frictionless contact stress solver based on the cell-centred finite volume method. The contact methodology, implemented in the open-source software OpenFOAM, is derived from the penalty method commonly used in finite element contact algorithms. The solver is verified on two benchmark tests using the available Hertzian analytical solutions.Deposited by bulk import5/11/2013. SB

A large strain finite volume method for orthotropic bodies with general material orientations

This paper describes a finite volume method for orthotropic bodies with general principal material directions undergoing large strains and large rotations. The governing and constitutive relations are presented and the employed updated Lagrangian mathematical model is outlined. In order to maintain equivalence with large strain total Lagrangian methods, the constitutive stiffness tensor is updated transforming the principal material directions to the deformed configuration. Discretisation is performed using the cell-centred finite volume method for unstructured convex polyhedral meshes. The current methodology is successfully verified by numerically examining two separate test cases: a circular hole in an orthotropic plate subjected to a traction and a rotating orthotropic plate containing a hole subjected to a pressure. The numerical predictions have been shown to agree closely with the available analytical solutions. In addition, a 3-D composite component is examined to demonstrate the capabilities of the developed methodology in terms of a variable material orientation and parallel processing.Deposited by bulk impor

Accurate prediction of blood flow transients : a fluid-structure interaction approach

Computational and Mathematical Biomedical Engineering (CMBE09), Swansea, UK, June 29- July 1, 2009Numerical studies are widely employed in establishing blood flow transients in arteries. Unfortunately, many of these are based on rigid arterial geometries where the physiological interaction between the flowing blood and the dynamics of a deforming arterial wall is ignored. Although many recent studies have adopted a fluid-structure interaction (FSI) approach, they lack the necessary validation and, thus, cannot guarantee the accuracy of their predictions. This work employs a well-validated FSI model to establish the dependency of WSS transients on arterial flexibility and predict flow transients in arterial geometries. Results show a high dependency of WSS transients on arterial wall flexibility, with hoop strains of as low as 0.15% showing significant differences in these transients compared to that seen in a rigid geometry. It is also shown that flow in the atherosclerosis susceptible regions of the vascular tree is characterised by a highly disturbed flow. In these regions, WSS magnitudes are at their lowest, while the WSS spatial gradients, rate of change and oscillatory shear index are at their highest.Deposited by bulk import9/10/2013. SB

Development of a Finite Volume Based Structural Solver for Large Rotation of Non-Orthogonal Meshes

7th OpenFOAM Workshop, Technische Universität Darmstadt Germany 25-28 June 2012 DarmstadtDeposited by bulk import15/10/2013. SB

Characterisation of the fracture energy and toughening mechanisms of a nano-toughened epoxy adhesive

In this study the adhesive joint fracture behaviour of a nano-toughened epoxy adhesive was investigated. Two experimental test methods were used; (i) the standard tapered double cantilever beam (TDCB) test to measure the mode I adhesive joint fracture energy, GIC, as a function of bond gap thickness and (ii) a circumferentially deep notched tensile test to determine the cohesive strength of the adhesive for a range of constraint levels. It was found that the fracture energy of the adhesive followed the well-known bond gap thickness dependency [1]. SEM analysis of the TDCB fracture surfaces revealed significant plastic void growth. Finally, numerical modelling of the experimental tests suggested that most of the fracture energy was dissipated via highly localised plasticity in the fracture process zone ahead of the crack tip.Deposited by bulk importkpw3/10/1

The Effect of Constraint on the Fracture Toughness of Adhesively Bonded Joints

32nd Annual Meeting of the Adhesion Society, Savannah, Georgia, 15-18 February 2009Deposited by bulk import15/10/2013. SB

Micro-Mechanical Modelling of Void Growth, Damage and Fracture of Nano-Phase Structural Adhesives Using the Finite Volume Method

6th International Conference on Fracture of Polymers, Composites and Adhesives, September 11-15, 2011, Les Diablerets, SwitzerlandSignificant toughening of structural adhesives is attainable with the addition of nano and/or micro particles1,2,3. A deep understanding of the effect of particle de-bonding and subsequent void growth to coalescence is key to evaluating the strengthening and failure mechanisms occurring in the damage and fracture of these adhesives. Tapered Double Cantilever Beam (TDCB) experiments, conducted at University College Dublin (UCD), have observed a significant dependence of the fracture toughness of these adhesives on bond gap thickness5. In conjunction with this change in fracture toughness, scanning electronmicroscopy (SEM) of the fracture surface has also revealed corresponding changes in void evolution as the bond gap is varied. Classical analysis suggests the change in toughness may be attributed to a physical constraint of the size to which the plastic zone around a crack tip may develop6. However, simulation of these TDCB tests using finite volume stress analysis has found that little plasticity develops in the bulk adhesive layer and is instead concentrated in the fracture process zone. The change in fracture toughness and void evolution present can be attributed to the change in triaxiality at different bond gap thicknesses and the results agree quite well with the void growth model of Rice & Tracey4. The variance of void growth with triaxiality is investigated here. The initial work considered here concerned 3D modelling of a void in an elastic perfectly plastic material with a view to verifying exponential dependence of void growth on the macroscopic stress triaxiality in the system in accordance with the Rice & Tracey model. The model examines void growth rate dependence on the stress triaxiality, for a given effective strain.Deposited by bulk import15/10/2013. SB

Mode-mixity in beam-like geometries: global partitioning with cohesive zones

36th Annual Meeting of The Adhesion Society, Inc. Daytona Beach, Fl, USA, 2013.In-service adhesive joints and composite laminates are often subjected to a mixture of mode I (tensile opening) and mode II (in-plane shear) loads. It is generally accepted that the toughness of such joints can vary depending on the relative amounts of mode I and mode II loading present. From a design perspective, it is therefore of great importance to understand and measure joint toughness under a full range of mode-mixities, thus obtaining a failure locus ranging from pure mode I to pure mode II. The pure mode toughnesses (I, II) can be measured directly from experimental tests. The most common tests being the double cantilever beam (DCB) for mode I and end loaded split (ELS) for mode II. Unfortunately, the analysis of a mixed mode test is not straightforward. In any mixed mode test, one must apply a partition in order to estimate the contributions from each mode. The particular test under study in this work is the fixed ratio mixed mode test (FRMM) with a pure rotation applied to the top beam (fig. 1). In this test, a range of mode-mixities can be obtained by varying γ, where γ is the ratio of h1/h2. This test is normally analysed using analytical or numerical methods, each of which suffers from a number of uncertainties. The present work attempts to shed some light on both analytical and numerical approaches and ultimately develop a testing protocol and recommendations for the accurate determination of modemixity in this FRMM test and other similar beam-like geometries.Deposited by bulk importkpw30/10/1