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1
Content available remote The Effect of Non-Fully Filled Gaps in Elastic Tribological Contacts
EN
In recent papers, the authors of this paper investigated the dynamic behavior in partially fluid-filled tribological gaps with a novel modeling technique. The impact of the fluid amount towards the buildup of hydrodynamic pressures has been demonstrated. It shows high nonlinearities with respect to the correlation of the filling ratio and the mean pressure, in particular near the fully filled regime. So far, this modeling technique neglected deformations caused by the pressures in the gap. This paper is focused on fundamental studies on the impact of elastic deformations in combination with varying filling ratios onto the pressure characteristic. The studies are performed using an example of two ellipsoidal bodies moving relative to one another. The size of the ellipsoids is varied which allows modifying the gap topography. In this paper, the essential effect of elastic deformations at very small gaps is shown. It is discussed that it is very complex to formulate a general rule about parameter sets that give the possibility to neglect elastic deformations.
EN
Presented work concerns problems connected with a new "smart material". It is a granular structure, built basing on a loose material, placed in a tight encapsulation, where in a next stage so called underpressure has been generated. The main aim of this paper is to establish the general dependence between grain's material and an elastic range of deformations (proof stress), in uniaxial experiments, of specially performed granular samples, for a wide range of applied underpressure values.
EN
A new "smart structure", based on granular materials encapsulated in an elastic envelope, is proposed and investigated in the paper. Fundamental mechanical properties of the specially prepared granular testing specimens are described by the viscoplastic constitutive Chaboche's model. The experimental results of uniaxial tests are presented and applied to the identification of parameters of the Chaboche's law. The proposed procedure of material parameters estimation is based on evolutionary algorithms, solving corresponding optimization problem. The efficiency of the approach and the quality of the results are discussed.
4
Content available remote Diffusion of hydrogen in austenitic stainless steel.
EN
A method has been proposed for determination the hydrogen diffusion coefficient in metals. It involves measuring the magnitude of elastic deformations in samples during the time of hydrogen desorption. Measurements of the elongations of thin samples of the type 310 austenitic stainless steel show that, during electrolytic charging with hydrogen, as well as elastic deformations, permanent deformations arise, meaning that measurements made during charging are of no value in determining the diffusion coefficient. Such determination can be made, however, from the elastic deformations occuring during the time of desorption of hydrogen. These deformations (approx. 1,9%) are great enough in the case of the steel tested to apply in the proposed method. The hydrogen diffusion coefficient obtained from measuring elastic deformations is very close in value to the results obtained for austenitic stainless steels using other methods, which suggests that the assumptions used herein are correct.
PL
Zaproponowano metodę wyznaczania współczynnika dyfuzji wodoru w metalach opartą na pomiarach wielkości odkształceń sprężystych próbek w czasie desorpcji wodoru. Pomiary wydłużeń cienkich próbek ze stabilnej stali austenitycznej typu 310 wykazały, że w czasie elektrolitycznego nasycania wodorem, obok odkształceń sprężystych powstają również odkształcenia trwałe, co powoduje, że pomiary w czasie nasycania nie są miarodajne dla określenia współczynnika dyfuzji. Współczynnik dyfuzji można natomiast określić w oparciu o odkształcenia sprężyste w czasie desorpcji wodoru. W przypadku badanej stali odkształcenia te wynoszą ok. 1,9% i są wystarczające do zastosowania zaproponowanej metody. Współczynnik dyfuzji wodoru wyznaczony metodą pomiaru wydłużeń sprężystych, ma bardzo zbliżoną wartość do wyników otrzymanych dla stali austenitycznych innymi metodami, co wskazuje na słuszność przyjętych założeń.
EN
We propose an approach for estimation of elastic deformations in medical registration. Compared to standard registration methods based on elasticity theory, our estimation scheme does not contain parameters of the deformation model (elastic constants). Rather, the computed elastic deformation is uniquely defined through incorporation of prescribed displacements on boundary structures in the source and target image. Under the assumption of correctness of input data, our estimation scheme provides the exact correspondence of sructures to be registered due to the constrains. Furthermore, to cope with large-magnitude deformation, we propose an incemental model based on successive linearizations of the non-linear elastic equilibrium equation. To illustrate the performance of our approach, we show experimental results for 2-D and 3-D synthetic as well as real medical images and provide timing information for sequential and parallel realizations.
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