fatigue reliability analysis of a turbine disc under multi source uncertainties

Abstract Life and reliability analysis of hot section components like high pressure turbine (HPT) discs plays an important role for ensuring the engine structural integrity. HPT disc operates under high temperatures to withstand complex loadings, its basic parameters, including the applied loads, material properties and working environments, have shown multi-source uncertainties. The influence of these uncertainties on the structural response of the turbine disc cannot be ignored. According to this, the variations of applied loads and material properties are quantified for fatigue reliability analysis of turbine disc. In particular, material response variability is modeled by using the Chaboche model and Fatemi-Socie damage criterion. Moreover, the inhomogeneity of its constituent material is also considered through combining FE simulation with Latin hypercube sampling. Finally, fatigue reliability analysis of a HPT disc under multi-source uncertainties is conducted for different flight missions

a new energy gradient based model for lcf life prediction of turbine discs

Abstract With continuous raising of thrust-weight ratio, low cycle fatigue (LCF) at high temperature is one of main failure modes for engine hot section components. Accurate life prediction of turbine discs has been critical for ensuring the engine integrity. According to this, a new LCF model through combining the energy gradient concept with critical distance theory is proposed for fatigue life prediction of turbine discs. In this paper, assuming that the processes of crack initiation and propagation in a LCF regime can be described by the cumulative strain energy. A relationship between the total strain energy in the fatigue process zone and the LCF life is explored. In particular, the energy parameters are weighted based on the energy gradient in the fatigue process zone. Using experimental data of GH4169 alloy at 650°C, a good agreement was achieved between model predictions and experimental results

Advanced Approaches Applied to Materials Development and Design Predictions

This thematic issue on advanced simulation tools applied to materials development and design predictions gathers selected extended papers related to power generation systems, presented at the XIX International Colloquium on Mechanical Fatigue of Metals (ICMFM XIX), organized at University of Porto, Portugal, in 2018. In this issue, the limits of the current generation of materials are explored, which are continuously being reached according to the frontier of hostile environments, whether in the aerospace, nuclear, or petrochemistry industry, or in the design of gas turbines where efficiency of energy production and transformation demands increased temperatures and pressures. Thus, advanced methods and applications for theoretical, numerical, and experimental contributions that address these issues on failure mechanism modeling and simulation of materials are covered. As the Guest Editors, we would like to thank all the authors who submitted papers to this Special Issue. All the papers published were peer-reviewed by experts in the field whose comments helped to improve the quality of the edition. We also would like to thank the Editorial Board of Materials for their assistance in managing this Special Issue

Liraglutide-induced reduction of myocardial ischemiareperfusion injury in rats via ERK1/2 signaling pathway

Purpose: To investigate the protective effect of liraglutide on myocardial ischemia reperfusion (I/R) injury and its molecular mechanism.Methods: Ischemia reperfusion model male Sprague-Dawley (SD) rats were randomly divided into negative control group, I/R group (saline), liraglutide group (liraglutide) and PD group (liraglutide + PD98059). The weight of myocardium in ischemic and infarction areas of the heart, myocardial injury biomarker, oxidative stress, as well as expressions of mRNA molecules of apoptosis were determined.Results: The myocardial mass of ischemic and infarcted areas of the heart (relative to left ventricular mass) of I/R group were significantly higher (p ˂ 0.05) than those of negative control group, but significantly lower in liraglutide group than in I/R group (p > 0.05). However, the parameters were significantly higher in PD group than in liraglutide group (p ˂ 0.05). CK, CK-MB and LDH activities, as well as levels of cTnI and cTnT in I/R group were significantly higher (p ˂ 0.05) than those of negative control group. However, the parameters were significantly lower (p ˂ 0.05) in liraglutide group than in I/R group, but higher in PD group (p ˂ 0.05) than in liraglutide group. Serum SOD, GSH-Px, CAT activities and tBcl-2 mRNA expression were significantly lower in I/R group than those of negative control group (p ˂ 0.001), while those PD group were significantly lower than those of liraglutide group (p ˂ 0.001).Conclusion: Liraglutide alleviates myocardial ischemia-reperfusion injury and inhibits oxidative stress and apoptosis via ERK1/2 signaling pathway in rats, but further studies are required to ascertain the clinical efficacy and safety of the compound.Keywords: Ischemia-reperfusion injury, Liraglutide, ERK1/2 signal pathway, Oxidative stress, Apoptosi

A Modified Nonlinear Damage Accumulation Model for Fatigue Life Prediction Considering Load Interaction Effects

Many structures are subjected to variable amplitude loading in engineering practice. The foundation of fatigue life prediction under variable amplitude loading is how to deal with the fatigue damage accumulation. A nonlinear fatigue damage accumulation model to consider the effects of load sequences was proposed in earlier literature, but the model cannot consider the load interaction effects, and sometimes it makes a major error. A modified nonlinear damage accumulation model is proposed in this paper to account for the load interaction effects. Experimental data of two metallic materials are used to validate the proposed model. The agreement between the model prediction and experimental data is observed, and the predictions by proposed model are more possibly in accordance with experimental data than that by primary model and Miner’s rule. Comparison between the predicted cumulative damage by the proposed model and an existing model shows that the proposed model predictions can meet the accuracy requirement of the engineering project and it can be used to predict the fatigue life of welded aluminum alloy joint of Electric Multiple Units (EMU); meanwhile, the accuracy of approximation can be obtained from the proposed model though more simple computing process and less material parameters calling for extensive testing than the existing model