177 research outputs found
Determination of heat transfer coefficient for hot stamping process
© 2015 The Authors.The selection of the heat transfer coefficient is one of the most important factors that determine the reliability of FE simulation results of a hot stamping process, in which the formed component is held within cold dies until fully quenched. The quenching process could take up to 10. seconds. In order to maximise the production rate, the optimised quenching parameters should be identified to achieve the highest possible quenching rate and to reduce the quenching time. For this purpose, a novel-testing rig for the Gleeble 3800 thermo- mechanical simulator was designed and manufactured, with an advanced control system for temperature and contact pressure. The effect of contact pressure on the heat transfer coefficient was studied. The findings of this research will provide useful guidelines for the selection of the heat transfer coefficient in simulations of hot stamping processes and useful information for the design of hot stamping processes
New Approach for Detecting and Tracking a Moving Object
This article presents the implementation of a tracking system for a moving target using a fixed camera. The objective of this work is the ability to detect a moving object and locate their positions. In picture processing, tracking moving objects in a known or unknown environment is commonly studied. It is based on invariance properties of objects of interest. The invariance can affect the geometry of the scene or the objects. The proposed approach is composed of several steps; the first is the extraction of points of interest in the current image. Then, these points will be tracked in the following image by using techniques for calculating the optical flow. After this step, the static points will be removed to focus on moving objects, That is to say, there is only the characteristic points belonging to moving objects. Now, to detect moving targets using images of the video, the background is first extracted from the successive images. In our approach, a method of the average values of every pixel has been developed for modeling background. The last step which stays before switching to tracking moving object is the segmentation which allows identifying every moving object. And by using the characteristic points in the previous steps
Knowledge based cloud FE simulation of sheet metal forming processes
The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques. This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions
Hot stamping of AA6082 tailor welded blanks: experiment and FE simulation
An advanced forming technology, solution Heat treatment, Forming and in-die Quenching (HFQ®), has been employed to form AA6082 tailor welded blanks (TWBs). In comparison with conventional stamping of TWBs, the mechanical properties and formability of AA6082 laser TWBs could be improved under the HFQ® forming condition. The TWB was divided into three physical zones, i.e. base metal, heat affected zone (HAZ) and weld zone, based on the hardness distribution. It was found that the degraded hardness of the weldment can be restored after HFQ® forming. TWBs of AA6082 with different thickness ratios of 2 (2–1 mm), 1.3 (2–1.5 mm) and 1 (1.5–1.5 mm) were used to study the TWB thickness ratio effects on the forming behaviour. Hemispherical punch dome tests on the TWBs with varying thickness ratios demonstrated different formabilities, and indicated increased displacement of the weld line with increasing thickness ratio. Finite element (FE) modelling was adopted to analyse the weld line movement and strain distributions during HFQ® forming
Determination of the interfacial heat transfer coefficient for a hot aluminium stamping process
The interfacial heat transfer coefficient (IHTC) is an important thermophysical parameter in hot stamping processes and must be identified not only to retain the full mechanical strength of formed components, but also to optimise the production rate. In this work, a novel experimental facility was developed and applied to measure the temperature evolutions of the specimens and tools in stamping processes. Simulated temperature evolutions obtained using the FE software PAM-STAMP were then fit to this data. The IHTC values between AA7075 and three different tool materials were characterized at different contact pressures under both dry and lubricated conditions. In addition, a mechanism based IHTC model was developed and validated as a function of contact pressure, tool material and lubricant thickness to predict the IHTC values under different conditions
A Study on Awareness of Income Tax Planning Among Women with Special Reference to Panvel Region
Based on a number of factors, including knowledge of the basic exemption limit, interest and penalties for nonpayment, deductions, rebates, TDS, loopholes, and alternative income-saving techniques, it can be determined that the majority of women in the Panvel region are aware of income tax planning. The unit is sampled using a simple random sampling technique. The data is collected from 118 respondents in the Panvel region. A descriptive Research Design is used to understand the variables that impact the income tax planning. Average mean descriptive statistics method using excel is used to analyze the data
Non-chaotic dynamics in general-relativistic and scalar-tensor cosmology
In the context of scalar-tensor models of dark energy and inflation, the
dynamics of vacuum scalar-tensor cosmology are analysed without specifying the
coupling function or the scalar field potential. A conformal transformation to
the Einstein frame is used and the dynamics of general relativity with a
minimally coupled scalar field are derived for a generic potential. It is shown
that the dynamics are non-chaotic, thus settling an existing debate.Comment: 20 pages, LaTeX, to appear in Class. Quantum Gra
Bending of Light by Gravity Waves
We describe the statistical properties of light rays propagating though a
random sea of gravity waves and compare with the case for scalar metric
perturbations from density inhomogeneities. For scalar fluctuations the
deflection angle grows as the square-root of the path length in the manner
of a random walk, and the rms displacement of a ray from the unperturbed
trajectory grows as . For gravity waves the situation is very
different. The mean square deflection angle remains finite and is dominated by
the effect of the metric fluctuations at the ends of the ray, and the mean
square displacement grows only as the logarithm of the path length. In terms of
power spectra, the displacement for scalar perturbations has while for gravity waves the trajectories of photons have which is a scale-invariant or `flicker-noise' process, and departures from
rectilinear motion are suppressed, relative to the scalar case, by a factor
where is the characteristic scale of the
metric fluctuations and is the path length. This result casts doubt on the
viability of some recent proposals for detecting or constraining the gravity
wave background by astronomical measurements.Comment: 14 pages, aastex, submitted to Astrophysical Journa
Chaotic inflation with running nonminimal coupling
We have found a successful model of chaotic inflation with an inflaton
coupled nonminimally with gravity. The nonminimal coupling constant runs
with the evolution of the inflaton. The running nature of the coupling leads
naturally to the situations where the coupling becomes small enough to have
sufficient period of the inflation to resolve the cosmological puzzles.Comment: 9 pages, Latex, 2 Figures. In Introduction and Discussion Comments on
the related works are changed and added appropriately. References are added
for completenes
Comment on Higgs Inflation and Naturalness
We rebut the recent claim (arXiv:0912.5463) that Einstein-frame scattering in
the Higgs inflation model is unitary above the cut-off energy Lambda ~ Mp/xi.
We show explicitly how unitarity problems arise in both the Einstein and Jordan
frames of the theory. In a covariant gauge they arise from non-minimal Higgs
self-couplings, which cannot be removed by field redefinitions because the
target space is not flat. In unitary gauge, where there is only a single scalar
which can be redefined to achieve canonical kinetic terms, the unitarity
problems arise through non-minimal Higgs-gauge couplings.Comment: 5 pages, 1 figure V3: Journal Versio
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