Prasad Gudimetla

Kerf formation analysis in the abrasive waterjet cutting of industrial ceramics

Abstract This paper investigated the machinability and kerf formation characteristics associated with the abrasive waterjet cutting of industrial ceramics. It is found that at low cutting rates, the erosive process is associated with initial surface fracture leading to a high degree of plastic flow and deformation of the subsurface, probably due to the incidence of high thermal stresses at the jet–target interaction zone. At higher speeds, surface fracture results in an intergranular network propagating downward, creating a critical shear plane that forms a kerf due to the hydrodynamic forces within the waterjet. This study reveals that there exists a combination of process parameters for the effective machining of ceramics. A grooving wear effect exists for the uncut through kerf.

Mechanical Behaviours of Pumpkin Peel under Compression Test

Abstract 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.

Impact & Energy Absorption of Road Safety Barriers by Coupled SPH/FEM

Road safety barriers are used to minimise the severity of road accidents and protect lives and property. There are several types of barrier in use today. This paper reports the initial phase of research carried out to study the impact response of portable water-filled barrier (PWFB) which has the potential to absorb impact energy and hence provide crash mitigation under low to moderate speeds. Current research on the impact and energy absorption capacity of water-filled road safety barriers is limited due to the complexity of fluid-structure interaction under dynamic impact. In this paper, a novel fluid-structure interaction method is developed based on the combination of Smooth Particle Hydrodynamics (SPH) and Finite Element Method (FEM). The sloshing phenomenon of water inside a PWFB is investigated to explore the energy absorption capacity of water under dynamic impact. It was found that water plays an important role in energy absorption. The coupling analysis developed in this paper will provide a platform to further the research in optimising the behaviour of the PWFB. The effect of the amount of water on its energy absorption capacity is investigated and the results have practical applications in the design of PWFBs.

In vitro reversal of the load-bearing properties of lipid-depleted articular cartilage following exposure to phospholipid surfactant solutions

BACKGROUND A microscopic layer of surface active phospholipids overlays the articular cartilage of the knee. Its depletion in osteoarthritic joints results in loss of lubrication and load-bearing efficiency. We hypothesize that exposure of articular cartilage to the dominant unsaturated phospholipid component of knee surfactant can regenerate the load-bearing properties of the tissue. This was evaluated by studying the stress-strain and stiffness characteristics of normal intact and lipid-depleted cartilage exposed to lipid-based surfactants for known durations. METHODS Normal intact, lipid-depleted and surfactant-treated bovine articular cartilage specimens were compressed at 0.5mm/min to a maximum strain of 40% and their stress-strain and stiffness data were compared. FINDINGS The stiffness of lipid-depleted samples increased by 40% on average relative to the normal; after exposure of the same samples to saturated surfactant for one and 24h, the average stiffness decreased by 25% and 62%, respectively from this high value. On the other hand, exposure of delipidized specimens to a mixture of selected unsaturated surfactant species for one and 24h resulted in a reduction of 85% and 90% in the stiffness of the depilidized samples respectively, largely reversing the effect of lipid removal to a level much closer to that of the normal intact cartilage and therefore better than that obtained with incubation in the saturated surfactant. INTERPRETATION Lipid loss in articular cartilage results in a consistent increase in stiffness relative to normal tissue stiffness. This consequence of lipid loss can be partially reversed by the reintroduction of surface active phospholipids. The results of this study show that the lipid components of cartilage play an important role in determining the compliance of the loaded tissue.

Studies on Bending Limitations for the Optimal Fit of Orthopaedic Bone Plates

Distal tibial fractures are now commonly treated via intermedullary plate fixation due to higher rates of union and lower rates of postoperative complications. However, patient specific bone morphology demands manual deformation of the plate to ensure appropriate fit along the bone contours, and depending on the material of the plate, different outcomes have been reported along with postoperative complications. A comparative analysis of Stainless Steel 316L and Ti-6Al-4V alloys was carried to estimate the safe bending limit for appropriate fits. The results from the ANSYS FEA simulations were validated with experiments based on ASTM F382-99. It is found that SS316L is better suited for large deformations (up to 16˚ in proximal tip and 7.5˚ in distal end) and Ti for smaller deformation contours (up to 3˚ in proximal tip and 1.8˚ in distal end). The results of this study have profound implications for the choice of plates based on preliminary radiographical fracture examinations to ensure better fixation and higher rates of union of distal tibial fractures.

“I’m very visible but seldom seen”: consumer choice and use of mobility aids on public transport

Abstract Purpose: The number of mobility aid users continues to rise as the population ages. While mobility aid users rely on public transport due to its affordability, evidence suggests access can be difficult. This study aims to describe people who use mobility aids to access public transport and the role of public transport access in influencing mobility aid choice. Methods: Sixty-seven mobility aid users participated in telephone surveys which predominantly used a structured quantitative format. Data were analysed descriptively and any additional comments were simply categorized. Results: Thirty-six participants were female (54%), with a total sample mean age of 58.15 years (SD = 14.46). Seventy-two percent lived in metropolitan areas, 48% lived alone, and the sample experienced a variety of conditions including spinal cord injury (37%) and arthritis (18%). Sixty-four percent of all respondents used two or more mobility aids including powered wheelchairs, scooters and walking frames. The most important features when choosing a mobility aid were reliability, turning ability and size. Fifty-two percent of all respondents strongly agreed that public transport is generally accessible. Conclusions: While work continues to ensure that public transport vehicles and stations are fully accessible, mobility aid users must manage current infrastructure and access a system which has been shown through this research to have many limitations. Mobility aid users, vendors and health professionals need to work together to identify mobility aids that fulfil needs, and are reliable and safe, so that mobility aid users are both “visible and seen” when accessing the public transport network. Implications for rehabilitation Some mobility aid users experience difficulties accessing and using public transport and further research is required to ensure the whole public transport network is fully accessible to people using mobility aids. Many people have more than one seated mobility aid, suggesting people can choose different aids for different purposes and environments. Health professionals may need to increase their involvement in assisting individuals to select and use mobility aids.