Testing and simulation of extruded polystyrene foam at low to moderate strain rates

This paper presents a study into the behaviour of extruded polystyrene foam at low strain rates. The foam is being studied in order assess its potential for use as part of a new innovative design of portable road safety barrier the aim to consume less water and reduce rates of serious injury. The foam was tested at a range of low strain rates, with the stress and strain behaviour of the foam specimens being recorded. The energy absorption capabilities of the foam were assessed as well as the response of the foam to multiple loadings. The experimental data was then used to create a material model of the foam for use in the explicit finite element solver LS-DYNA. Simulations were carried out using the material model which showed excellent correlation between the numerical material model and the experimental data

Preliminary characterisation of the surface of cartilage following exposure to saturated and unsaturated synthetic lips

Articular cartilage is covered by a microscopic structure known as surface amorphous layer. This surface structure is often the first victim of attack during cartilage degeneration, thereby resulting in a gross impairment in cartilage function such as lubrication and load bearing. We hypothesize that incubation of degraded cartilage in solutions of different species of synthetic surface active phospholipids (saturated and unsaturated species) can remodel this lost surface structure. To test this hypothesis, the structural configuration of the surface of articular cartilage was studied and characterised with the lipid filled surface amorphous layer intact using the AFM. The results were then compared with those obtained following a systematic removal (delipidization) and replacement (relipidization) of this layer. Our results show that the unsaturated surfactant partially restored the lost surface amorphous layer while the saturated surfactant specie settled on the surface due to its poor solubility in aqueous solution

A 3D measurement and computerized meshing study to promote bus ridership among people using powered mobility aids

People who use powered mobility aids such as wheelchairs and scooters need and want to use public transport. Buses are the most affordable and efficient form of public transport, capable of connecting people across local communities. However, with curbside rather than platform boarding and internal space limitations, buses also present many accessibility challenges for people using mobility aids during ingress, egress, and interior maneuverability. In Australia, people using mobility aids board low floor buses that are required to comply with the national bus accessibility standard, using the front doors. A new standard was recently created to provide a Blue Label identification for powered mobility aids suitable to access public transport. The accuracy of this standard to identify mobility aids suitable to use on buses has not been verified. This research used a world-first methodology that included 3-Dimensional (3D) scanning of 35 mobility aids and 21 buses. The resulting 735 scan combinations were efficiently meshed using Meshlab, an open-source software. The research demonstrated that (i) although none of the buses were compliant with the relevant standard in 3D, many could still facilitate the boarding of a variety of mobility aids, and (ii) the Blue Label, while a valuable guide, did not accurately identifying all mobility aids that would and would not be able to board buses. This research has shortlisted nine mobility aids that can be recommended to consumers as being able to fit all the full-size buses tested. The dimensions of mobility aids that appear to enable access on most buses were also identified for consumers to consider when purchasing a mobility aid. The novel 3D meshing methodology used in this research also revealed that most collision points between mobility aids and buses occur in the curved-corridor entry of the buses. To minimize this entry problem, future bus boarding designs should consider the option of double-door entry/exit in the middle of the bus, which is common in many other countries. Adoption of this strategy would mitigate some of the challenges that people using mobility aids encounter when accessing buses, thereby increasing public transport ridership among this group. © Copyright © 2020 Unsworth, Chua and Gudimetla

Mechanical behaviours of pumpkin peel under compression test

Mechanical damages such as bruising, collision and impact during food processing stages diminish quality and quantity of productions as well as efficiency of operations. Studying mechanical characteristics of food materials will help to enhance current industrial practices. Mechanical properties of fruits and vegetables describe how these materials behave under loading in real industrial operations. Optimizing and designing more efficient equipments require accurate and precise information of tissue behaviours. FE modelling of food industrial processes is an effective method of studying interrelation of variables during mechanical operation. In this study, empirical investigation has been done on mechanical properties of pumpkin peel. The test was a part of FE modelling and simulation of mechanical peeling stage of tough skinned vegetables. The compression test has been conducted on Jap variety of pumpkin. Additionally, stress strain curve, bio-yield and toughness of pumpkin skin have been calculated. The required energy for reaching bio-yield point was 493.75, 507.71 and 451.71 N.mm for 1.25, 10 and 20 mm/min loading speed respectively. Average value of force in bio-yield point for pumpkin peel was 310 N

The Role for E-Learning in Engineering Education: Creating Quality Support Structures to Complement Traditional Learning

The use of information technology (IT) based e-learning has emerged as an all-pervasive complementary learning tool for undergraduate instruction in recent times. E-learning or web-based instruction is being rapidly embraced by most universities across the world as such media of instruction are economical, convenient and disbursable to a larger audience. IT-based engineering education is now an important profit market for universities from a socio-economic and political view point. Consequently, diverse models have been developed and implemented across various disciplines of engineering. However, these initiatives have been misaligned and not properly integrated with existing and the ever-changing IT infrastructure. In this paper, we identify the hurdles faced with adopting IT-based learning tools for the instruction of highly technical courses in Mechanical Engineering in the Faculty of Built Environment & Engineering, QUT. We propose some support structures that are required to improve upon the existing mechanisms to deliver better and improved e-learning content

The Influence of Lipid-Extraction Method on the Stiffness of Articular Cartilage

Background One of the known characteristics of osteoarthritis is the loss of articular cartilage lipids. Therefore, it is important to study how lipids influence the functions of the tissue. This can only be done successfully by indirect analysis involving the extraction of lipids and subsequent assessment of the delipidized matrix. Therefore, for accuracy, the procedure for lipid extraction must not induce any other modification in the samples to be assessed. Hence, we compare three rinsing agents and methods in this study. Methods Normal and delipidized articular cartilage samples were tested under compressive loading at 4 loading velocities to obtain and compare their stiffness values. Findings Chloroform rinsing resulted in a 45% decrease in the stiffness of cartilage at low strain-rates (10−2/s and 10−1/s) on average with a corresponding increase of 55% at higher strain-rate of 10/s relative to the normal. Ethanol rinsed cartilage exhibited a corresponding decrease of 40% at the low strain-rates while exhibiting an increase of about 20% at the highest loading rates. Propylene glycol rinsing resulted in a decrease of approximately 20% in stiffness, while an increase of up to 5% at high rates of loading. Interpretation • The loss of lipids modifies the stiffness of articular cartilage at all loading rates. • The relatively larger deviation of the stiffness of chloroform rinsed samples relative to the normal is probably a consequence of the drying process involved in rinsing protocol. • It is probable that the results of milder rinsing agents, used without vacuum drying are more reflective of physiological delipidization effects on the tissue. Consequently, we recommend propylene glycol and its associated protocol for extracting lipids from articular cartilage

Simulation of delaminations in composite laminates

Lamb waves propagation in composite materials has been studied extensively since it was first observed in 1982. In this paper, we show a procedure to simulate the propagation of Lamb waves in composite laminates using a two-dimensional model in ANSYS. This is done by simulating the Lamb waves propagating along the plane of the structure in the form of a time dependent force excitation. In this paper, an 8-layered carbon reinforced fibre plastic (CRFP) is modelled as transversely isotropic and dissipative medium and the effect of flaws is analyzed with respect to the defects induced between various layers of the composite laminate. This effort is the basis for the future development of a 3D model for similar applications

Properties of tough skinned vegetable-pumpkin tissue

Understanding of mechanical behaviour of food particles will provide researchers and designers essential knowledge to improve and optimise current food industrial technologies. Understanding of tissue behaviours will lead to the reduction of material loss and enhance energy efficiency during processing operations. Although, there are some previous studies on properties of fruits and vegetables however, tissue behaviour under different processing operations will be different. The presented paper is a part of FE modelling and simulation of tissue damage during mechanical peeling of tough skinned vegetables. In this study indentation test was performed on peeled and unpeeled samples at loading rate of 20 mm/min for peel, flesh and unpeeled samples. Consequently, force deformation and stress and strain of samples were calculated. The toughness of the tissue also has been calculated and compared with the previous results

Finite Element Analysis of the Interaction between an AWJ Particle and a Polycrystalline Alumina Ceramic

Purpose: Abrasive waterjet cutting involves use of a high pressure, abrasive laden waterjet at trans-sonic speeds to cut difficult-to-machine materials. The jet-material interaction depends on the nature of the material being cut, such as ductile or brittle. The brittle regime involves the generation and propagation of microcracks due to impact and many theories have been proposed in this regard. We aim to resolve the nature of the generation and propagation of cracks in such phenomena using the finite element analysis methodology. Design/methodology/approach: A 3-dimensional FE model was set up using PATRAN. The alumina ceramic was modelled as a 1-mm cube while a 0.1mm diameter half sphere was used to model a single abrasive particle. The system was imported into ABAQUS and an explicit analysis was performed. The element deletion method was used after invoking a failure criterion to estimate the number of elements removed due to a single impact. The aggregate volume of eroded material was then calculated by multiplying the number of elements removed with the volume of each element. The results of the FEA were compared with the brittle model proposed by Kim & Zeng [12]. Findings: The results of the FEA indicate that mixed-mode failure is the most common form of failure in such interactions. The volume of material removed per impact from the FE results is close to 16% of those predicted by Kim & Zeng’s model. Research limitations/implications: The finite element framework presented is idealized for the case of regular cubes based on a set of assumptions. Originality/value: This finite element approach is a good tool to study the nature of interaction between a microscopic particle and a brittle material and accurately predict the erosion mechanisms in such interactions