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1

Validation of an experimental technique with the physically based global method

Magiera J.

Computer Assisted Methods in Engineering and Science

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2012

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Vol. 19, no. 4

369-382

EN

Validation of an experimental approach requires that both m odel and data errors are proved to be within acceptable ranges. In case of destructive testing none of th e classic, statistically based methods can be applied for that task due to the lack of independent data seri es required for building data statistics. The aim of the paper is to present a non-statistical methodology for performing such validation, developed within the framework of physically based approximation (PB A). It has been developed to validate a neutron diffraction based experimental-numerical approac h applied for studying 3D rail residual stress. It is for the PBA technique’s capability to provide high qualit y physically reasonable data fits for one data set only, treated here as higher order reference fields that m ade it possible to develop this methodology and perform error analysis/validation. In many ways this aproach is analogical to Zienkiewicz-Zhu type of error estimators, and its performance will be demonstrated for a defective RE136 rail sample that was installed in a US DOT test track.

2

Analiza naprężeń i odkształceń plastycznych w kontakcie koła pojazdu szynowego z szyną z zastosowaniem różnych modeli materiału

Skrzat A.

Rudy i Metale Nieżelazne

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2009

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R. 54, nr 11

815-820

PL

Opisano prace badawcze związane z projektem sponsorowanym przez Federal Railroad Administration z USA dotyczącym analizy naprężeń i odkształceń w kołach pojazdów szynowych i szynach kolejowych. Głównym celem autora było określenie na drodze obliczeń numerycznych rozkładów naprężeń i odkształceń w kole wynikających z kontaktu koło-szyna. W obliczeniach przyjęto następujące modele materiału: materiał idealnie sprężysto-plastyczny, materiał sprężysto-plastyczny z umocnieniem izotropowym oraz materiał sprężysto-lepkoplastyczny. W artykule opisano zunifikowany materiał plastyczny Bodnera-Partoma, dla którego na tym etapie prac wykonano jedynie testy dla stanu jednoosiowego rozciągania. Wiarygodność znalezionych numerycznie rozkładów naprężeń i odkształceń w kole powinna być zweryfikowana w badaniach eksperymentalnych. Przedstawiono niszczące badania kół pojazdów szynowych oraz rozkłady obwodowych naprężeń własnych uzyskane w wyniku podejścia zwanego aproksymacją fizycznie uzasadnioną.

EN

Research sponsored by Federal Railroad Administration USA concerning stress and strain analysis in railroad car wheels and rails is presented in this paper. The main goal is the numerical stress and strain analysis in railroad car wheels resulting from the wheel-rail contact. Various wheel-rail positions are considered. The following material models are used: elastic-perfectly plastic, elastic-isotropic hardening and elastic-viscoplastic. Description of unified plastic Bodner-Partom material is included. Bodner-Partom material is suitable for the analysis of the materials beyond the yield limit subjected to cyclic loading under different temperatures. Results of BP material application to uniaxial tests are presented. Reliability of numerically found stress and strain distributions in wheels should be verified experimentally. Destructive tests for railroad car wheels are described. Residual hoop stress reconstruction obtained by application of the approach called physically-based approximation is also included.

3

Non-statistical physically reasonable technique for a posteriori estimation of experimental data error

Magiera J.

Computer Assisted Mechanics and Engineering Sciences

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2006

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Vol. 13, No. 4

593-611

EN

In the paper presented is an application of the physically based global method (PBGM) to a posteriori estimation of experimental data error. It is proposed here to build data error measures by spanning a high ąuality physically reasonable smoothing fit to data and treat it as a reference field for error estimation in a very similar way it is done in the postprocessing type error estimates used widely in FE or meshless methods, where the higher order (superconvergent) solutions are used for building error estimates (post-processing type of error estimators). The new techniąue is different from classical methods of experimental data error estimation as it provides non-statistical estimates of the data error and as such it may be applied to a wider rangę of problems, including cases when only a single data set is available (e.g., destructive testing). And because the new approach builds the estimates while performing its standard physically based global-type approximation, it fully integrates other features of the PBGM approach like data interpolation, extrapolation or differentiation. In the paper the whole PBGM approach is presented, including the concept of the method formulated for the case of analysis of residual stress in railroad rails, discretisation with MFDM, then several PBGM a posteriori error estimates are introduced and results for test problems (benchmark and actual data) are shown.