28,846 research outputs found
Numerical modelling and simulation in sheet metal forming
The application of numerical modelling and simulation in manufacturing technologies is looking back over about a 20â30 years history. In recent years, the role of modelling and simulation in engineering and in manufacturing industry has been continuously increasing. It is well known that during manufacturing processes simultaneous the effect of many different parameters can be observed. This is the reason why in former years, detailed analysis of manufacturing processes could have been done only by time-consuming and expensive trial-and-error methods. Due to the recent developments in the methods of modelling and simulation, as well as in computational facilities, modelling and simulation has become an everyday tool in engineering practice. Besides the aforementioned facts, the emerging role of modelling and simulation can also be explained by the growing globalisation and competition of the world market requiring shorter lead times and more cost effective solutions. In spite the enormous development of hardware and software facilities, the exclusive use of numerical modelling still seems to be very time- and cost consuming, and there is still often a high scepticism about the results among industrialists. Therefore, the purpose of this paper is to overview the present situation of numerical modelling and simulation in sheet metal forming, mainly from the viewpoint of scientific research and industrial applications
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Robust semi-automated path extraction for visualising stenosis of the coronary arteries
Computed tomography angiography (CTA) is useful for diagnosing and planning treatment of heart disease. However, contrast agent in surrounding structures (such as the aorta and left ventricle) makes 3-D visualisation of the coronary arteries difficult. This paper presents a composite method employing segmentation and volume rendering to overcome this issue. A key contribution is a novel Fast Marching minimal path cost function for vessel centreline extraction. The resultant centreline is used to compute a measure of vessel lumen, which indicates the degree of stenosis (narrowing of a vessel). Two volume visualisation techniques are presented which utilise the segmented arteries and lumen measure. The system is evaluated and demonstrated using synthetic and clinically obtained datasets
Phase-field simulations of viscous fingering in shear-thinning fluids
A phase-field model for the Hele-Shaw flow of non-Newtonian fluids is
developed. It extends a previous model for Newtonian fluids to a wide range of
shear-dependent fluids. The model is applied to perform simulations of viscous
fingering in shear- thinning fluids, and it is found to be capable of
describing the complete crossover from the Newtonian regime at low shear rate
to the strongly shear-thinning regime at high shear rate. The width selection
of a single steady-state finger is studied in detail for a 2-plateaux
shear-thinning law (Carreau law) in both its weakly and strongly shear-thinning
limits, and the results are related to previous analyses. In the strongly
shear-thinning regime a rescaling is found for power-law (Ostwald-de-Waehle)
fluids that allows for a direct comparison between simulations and experiments
without any adjustable parameters, and good agreement is obtained
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