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Influence of modelling phase transformations with the use of LSTM network on the accuracy of computations of residual stresses for the hardening process

Wróbel Joanna, Kulawik Adam

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 4

art. no. e145681

EN

Replacing mathematical models with artificial intelligence tools can play an important role in numerical models. This paper analyses the modeling of the hardening process in terms of temperature, phase transformations in the solid state and stresses in the elastic-plastic range. Currently, the use of artificial intelligence tools is increasing, both to make greater generalizations and to reduce possible errors in the numerical simulation process. It is possible to replace the mathematical model of phase transformations in the solid state with an artificial neural network (ANN). Such a substitution requires an ANN network that converts time series (temperature curves) into shares of phase transformations with a small training error. With an insufficient training level of the network, significant differences in stress values will occur due to the existing couplings. Long-Short-Term Memory (LSTM) networks were chosen for the analysis. The paper compares the differences in stress levels with two coupled models using a macroscopic model based on CCT diagram analysis and using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) and Koistinen-Marburger (KM) equations, against the model memorized by the LSTM network. In addition, two levels of network training accuracy were also compared. Considering the results obtained from the model based on LSTM networks, it can be concluded that it is possible to effectively replace the classical model in modeling the phenomena of the heat treatment process.

2

Charakterystyki dynamiczne zapór ziemnych i obwałowań

Kuboń P., Tatara T.

Czasopismo Techniczne. Budownictwo

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2005

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R. 102, z. 12-B

51--66

PL

W niniejszym artykule przedstawiono metodykę badań dynamicznych in situ zapór ziemych i obwałowań z zastosowaniem wibrosejsu MARK3. Rozważono również dobór dynamicznego modelu wybranych zapór ziemnych i obwałowań. Wykonano obliczenia z uwzględnieniem zastanego poziomu piętrzenia wody podczas badań dynamicznych in situ analizowanych obiektów. Model analizowanych konstrukcji przyjęto w postaci sprężystej tarczy pracującej w płaskim stanie odkształcenia. W pracy omówiono także kilka wariantów modelu dynamicznego. W poszczególnych wariantach uwzględniano odpowiednio: stałe materiałowe przyjęte na podstawie danych z literatury, naprężenia efektywne w gruncie wynikające z ciężaru wody i ciężaru gruntu, stopnie nasycenia gruntu wodą oraz masę wody związanej.

EN

The paper deals with methodology of dynamic investigation of earth dams and embankments with vibrator MARK3 as well as selection of dynamic model of chosen structures. Calculations were executed with regard of existing water level during dynamic investigation in situ of analyzed structures. In the study several variants of dynamic model have been considered. The model of analyzed structures has been assumed as elastic shield in plain strain. In particular variants of model there have been assumed: material data properties taken from literature, effective stresses in soil resulting from weights of water and soil, saturation ratio and mass of bounded water.

3

Dislocation structures, effective and internal stresses of cyclic strained ferritic stainless steel

Petrenec M., Polák J.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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Vol. 279, z. 72

129-133

EN

The hysteresis loops of ferritic X10CrA124 were digitally recorded and analysed in order to separate the effective and internal. By means of the "Generalised statistical theory of the hysteresis loop" the average characteristics such as the effective elastic modulus Eeff, the saturated effective stress [sigma es] and the probability density function f(sic) in relation to the number of cycles and [epsilon ap] were determined. The cyclic plastic response of ferritic steel can be accurately described by this statistical theory (high [sigma es] = 255 MPa). As for the ferritic steel, the secon local maximum of f([sigma ic]) was revealed. This phenomenon was discussed together with an observed dislocation arrangement by TEM methods, the orientation of crystals was determined by Kikuchi lines. The dislocation structures were studied in cyclical deformed polycrystalline ferritic stainless steel X10CrA124 using transmission electron microscope (TEM). Specimens were strained in plastic strain amplitude [epsilon ap] controlled tests (symmetric tension-compression) at room temperature to failure. Thin foils were prepared from specimens cycled with plastic strain amplitudes = 1x10-5, 2x10-5, 1x10-4, 5x10-4, 1x10-3, 3x10-3, 1x10-2. In dependence on [epsilon ap] three basic dislocation structures were identified. Nevertheless space dislocation arrangements at low [epsilon ap] change into bunch dislocation loops, veins, walls (labyrinths) and cell dislocation arrangements prevail at high.