DATABASE FINLIV – FOCUS ON STAIRCASE METHOD

This paper introduces FinLiv database focused on gathering, manipulating and providing experimental static and fatigue data. One of its new features is the ability to include also fatigue tests realized by the staircase method

Differences in the response to in-phase and out-of-phase multiaxial high-cycle fatigue loading

This paper discusses the phase shift effect occurring between two and more load channels of multiaxially loaded specimens. The discussion concludes that there is an extreme shortage of good experimental data that would prove the existence and the trend of the phase shift effect in the high-cycle fatigue region. It is no wonder that there are so many fatigue strength estimation criteria that use quite different computational concepts, because the response to the phase shift effect in the experimental base is often hidden in a conglomeration of other interacting effects. The paper presents results of a sensitivity study that compares the fatigue strength estimation results for various such criteria for the same stress amplitudes, but for different phase shifts between the push-pull and torsion load channels. These results show that, with the exception of criteria, that assume a zero phase shift effect, the phase shift affects the results of each studied fatigue strength estimation criterion in a different way. If well-organized experiments were available, experiments corresponding to the described comparison between in-phase and out-of-phase loading would show the right trends, and the optimum criterion could be selected. A proposal for such an experimental setup is provided in the paper

Progress in fatigue life calculation by implementing life-dependent material parameters in multiaxial fatigue criteria

This paper presents the concept of applying life-dependent material parameters to several multiaxial fatigue criteria. This concept reflects the transformation of damage mechanisms in relation to the applied load level, and also in relation to the varying level of plasticity. The goal of this study is to demonstrate the benefit of introducing life-dependent material parameters into stress-based multiaxial fatigue criteria for predicting the fatigue life of materials. New experimental results of fatigue tests on 2124-T851 aluminium alloy confirm the advantage of the life-dependent concept in life assessment over the concept with fixed weight parameters

THERMO-MECHANICAL FATIGUE ANALYSIS OF A STEAM TURBINE SHAFT

Increasing demands on the flexibility of steam turbines due to the use of renewable energy sources substantially alters the fatigue strength requirements of components of these devices. Rapid start-ups as well as the increased number of the load cycles applied to the turbines must be handled by design methodologies. The goal of the work presented in this paper was to provide a computational framework applicable to the thermo-mechanical fatigue (TMF) prediction of steam turbine shafts. The so-called Damage Operator Approach by Nagode et al. has been implemented to the software codes and applied to fatigue analysis of the thermo-mechanical material response computed numerically by the finite element analysis. Experimental program conducted in order to identify the material thermo-mechanical behavior and to verify numerical simulations is introduced in the paper. Some results of TMF prediction of a sample steam turbine shaft are shown

The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

The FLUXNET2015 dataset provides ecosystem-scale data on CO2, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.Peer reviewe

Coverage of multiaxial fatigue criteria in fatigue limit region

There is a power of methods aimed at calculation of equivalent fatigue limit for arbitrary multiaxial loading. Although there are so many ways of computation, their thorough mutual comparison in a larger scale is missing. The database project presented in this paper comprise of several databases crowned with the FatLim database, which comprise of a huge number of experimental results and of 18 computational method working in the category mentioned before. The great block of data was acquired using in-house fatigue software PragTic, which is offered as a freeware application. The FatLim database follows its philosophy of a simple and non-paid accessibility. Its query tool written in MySQL and PhP allows to users to evaluate a practical usability of tested methods on load cases, which the users define. All the issues covered within this paper are available on the website www.pragtic.com, structure of which is described here

Mean stress effect in multiaxial fatigue limit criteria

The paper deals with evaluating the mean stress effect in multiaxial criteria for fatigue limit estimation, with special emphasis on the mean shear stress effect. The usual practice of accepting the mean normal stress effect and neglecting the effect of static torsion is scrutinized. Two methodstwo critical plane criteria, PCr (Papuga Criterion) and QCP (Quadratic parameter on the Critical Plane)are described, and additional local stress parameters representing the mean torsion effect are implemented. The efficiency of the new implementations is evaluated on a large data set of 407 fatigue limits. Additionally, outputs of two other well-known methodsthe Crossland method and the Dang Van methodare provided for comparison. The positive outcome of including the mean shear stress effect is evident not only in cases of applied mean torsion load, but also in cases with purely axial loading or with biaxial configurations.Web of Science89583482