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Nominal stress-based estimation of fatigue life of welded joints

100%

Głowacka K. , Łagoda T.

tom Vol. 64, No. 2

39--44

The paper presents methods for determining the fatigue life of welded joints with particular emphasis given to typical joints. In addition, the article presents various possible nominal stress-based ways enabling the calculation of stresses, including structural stresses and involving the most complex linear fracture mechanics. The paper also discusses recommendations by the International Institute of Welding related to the determination of the fatigue life of welded joints in flat elements exposed to tension-compression conditions. The work is focused on assessing the fatigue life of welded joints (selected types) in accordance with the guidelines specified in related recommendations issued by the International Institute of Welding and taking into consideration the analysis concerned with the safety of such structures.

Przedstawiono metody wyznaczania trwałości zmęczeniowej złączy spawanych ze szczególnym uwzględnieniem typowych złączy. Podano możliwe sposoby wyznaczania naprężeń uzyskanych na drodze obliczeniowej w złączach spawanych na podstawie naprężeń nominalnych według różnych propozycji, poprzez naprężenia strukturalne, aż po zastosowanie najbardziej skomplikowanej liniowej mechaniki pękania. Na tym tle przedstawiono zalecenia Międzynarodowego Instytutu Spawalnictwa dotyczące wyznaczania trwałości zmęczeniowej złączy spawanych w warunkach rozciągania-ściskania elementów płaskich. Skupiono uwagę na problemie oceny trwałości zmęczeniowej połączeń spawanych wybranych typów złączy zgodnie z wytycznymi zawartymi w zaleceniach Międzynarodowego Instytutu Spawalnictwa oraz analizie bezpieczeństwa takich konstrukcji.

Nonlinear motion law of coalbed gas seepage under the combined effects of stress field and temperature field

80%

Li B. , Wei J. , Li P. , Wang K. , Borisyuk Y. A.

tom Vol. 94, nr 2

106--113

The shrinkage and swelling of the coal matrix due to the effects of temperature were investigated through the performance by Henan Province Key Lab of Gas Geology & Gas Control of a permeability test of loaded coal under various temperature and working conditions using its own seepage equipment for thermo-fluid-solid-mechanical coupling of methane-containing coal. The variation of coal permeability under the combined effects of stress and temperature was investigated, and the gas motion law in the coal samples was tested. The variation equations of coal permeability under the combined effects of stress and temperature, as well as the motion equations describing the nonlinear gas seepage law in coal seams were established. The established equations were proved to fit well with the experimental data, which demonstrated that the motion equations and the research methods were both reasonable. Study on the seepage nonlinear motion law of gas in the coal seam is great significance to mineral gas extraction.

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

80%

Wróbel J. , Kulawik A.

tom Vol. 71, nr 4

art. no. e145681

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.