Monotonic Fatigue

BACKROUND AND INTRODUCTION Fatigue is a phenomenon that has undergone to a structure due to repeated loadings which has stress cycles before undergoing failure.
In 19th century Developments regarding material fatigue damage could not be seen. Failure apparently occurred without any previous warning. But in 20th century we could understand that repeated load applications can cause a fatigue mechanism in the material leading to initiation of a small crack, followed by crack growth, and ultimately leading to structure failure. The history of engineering structures until now has been marked by numerous fatigue failures of machinery, moving vehicles, welded structures, aircraft, etc. There has been failures which have caused catastrophic accidents,

A basic approach was utilized throughout the study to understand the fundamental relationships responsible for metal failure. This method is just the elongation of previously existed continuum mechanics based theories which used a wider range of application. Research was conducted as two separate studies one which examine specific aspects of the metal failure spectrum, one by monotonic loading, and the other by fatigue failure due to cyclic loading. The failure due to monotonic loading research was conducted to examine the influence of hydrostatic stress on metal ductility. A basic relationship in the form of a monotonic failure criterion was proposed based on a relationship between equivalent plastic fracture strain and hydrostatic stress. An experimental program incorporating uniaxial tensile testing of notched specimens was conducted to examine the proposed relationship for the hydrostatic tensile stress range. Finite element analyses were produced to confirm the mechanical properties and obtain the stress-strain state present at specimen failure. A good relation was established between the load-displacement results obtained from experiment and finite element analysis, providing confirmation of the stress-strain data. The stress-strain results confirmed the existence of a relationship between hydrostatic stress and ductility in the form of a monotonically

For bending Fatigues S-N curves have been obtained. There has been many tests being conducted on the behaviour of tension and compression on strain control. Some of the authors perform their tests through sinusoidal loading. For estimation of bending fatigue in cement A basic approach was WEibull distribution of survival probability was taken which indicates the failure possibility for a constant amplitude and given frequency.
Some of the methods also applied by authors is to use data science technique to predict failure strength of materials like steel Understanding each step we get
1.Preprocesssing
Understanding and cleaning the data for proper normalization is one of the most important steps for effective data mining. Preprocessing, indefinitely, becomes extremely crucial in any kind of predictive modelling, including that of fatigue strength.
2.Feature selection
Information gain
This is an entropy-based metric that evaluates each attribute independently in terms of its worth by measuring the information gain with respect to the target variable.
3.Predictive