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Abstract. The paper compares various methods for computing the equivalent stress amplitude for stress cycles of non-zero mean value in stress-life fatigue prediction. A set of 11 calculation methods is evaluated. In addition to formulations based on common static or fatigue properties, the Walker formula and the generalized Linear formula are included in the investigation. These two methods use an optimization routine to find the material parameters. The final response of the methods is compared and discussed. The Walker method provides a better solution. The generalized Linear method produces inferior results, i.e. the linear fit of the segment of the Haigh diagram is not an optimal solution.

This paper presents a systematic effort to prepare base data for benchmark tests to evaluate the quality of fatigue prediction methods and solvers. The output of the work is the FinLiv database. The use of FinLiv is based on data sheets with a predefined structure, saved as *.csv files. Two applications take care of handling the data. The FinLiv.VBA application under MS Excel is focused on new data input. It allows users to categorize various aspects of fatigue tests, save them to a csv data sheet, send them to a standardized xls document, and finish the regression analysis there. The final results of the regression can be further elaborated or processed to generate inputs for various fatigue solvers. The other part of the solution is the Internet FinLiv application, which takes over the csv files and gathers them into MySQL databases. The front-end of the database is available on the www.fadoff.cz website. It allows users to look for particular types of data, and to view them or compare them. A csv file can again be generated from the database record and reused for any other goal in research or engineering analyses.

Selected methods for calculating notch tip strains and stresses in elastic-plastic isotropic bodies subjected to multiaxial monotonic loading were compared. The methods use sets of equations where hypothetical notch tip elastic strains and stresses obtained from FEM calculations serve as an input. The comparison was performed within two separate groups of methods: the first group consists of the methods intended for cases of multiaxial proportional loading and the second group deals with multiaxial non-proportional loading. Originally, the precision of the methods was validated by comparison with results obtained from elastic-plastic FEM analyses. Since computer performance at the time was lower than nowadays, verification of the proposed methods on FEM models with a finer mesh was needed. Such verification was carried out and is presented in this paper. The effect of various formulations of material stress-strain curve was also evaluated.

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