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Fatigue testing by means of miniature test specimens

Volak J., Novak M., Kaiser J., Mentl V.

Journal of Achievements in Materials and Manufacturing Engineering

2012

Vol. 55, nr 2

386--389

Purpose: The purpose of the paper is to describe fatigue testing by means of miniature test specimens. Design/methodology/approach: Special miniature test specimens fixtures were designed and manufactured for the purposes of fatigue testing at the Zwick/Roell - Amsler 10HPF5100 test machine. The miniature test specimens were produced of the traditional test specimens. Seven different steels and an Al-alloy were fatigue loaded (R = 0.1) at room temperature. Findings: The paper describes the results of fatigue tests performed on miniature tests specimens in comparison with traditional fatigue tests for several steels (and one Al-alloy) applied in power producing industry. Research limitations/implications: At present, questions on quantitative evaluation of remaining lifetime become urgent and because fatigue is the most frequent cause of materials degradation and resulting structural components failures, the most important means of remaining lifetime assessment is the evaluation of fatigue properties before and after some time of service. Originality/value: The original material data are usually tested by means of classic test specimens, which can be hardly used in case of components in service, where there is no possibility to withdraw sufficient volume of representative material for the classic test specimen manufacturing. In such cases today, new modern methods of semi-destructive removal of a small volume of test material by grinding or an electro-discharge are utilized. This makes it possible to produce a miniature test specimens.

Initial limit deflections of R-C beams with respect to the coupled nonlinear and non-homogeneous characteristics of the concrete by using EC2 code

Kaiser J., Ivankova O., Sumec J.

Archives of Civil Engineering

1998

Vol. 44, nr 1

79-88

Procedures for calculations of the initial deflections of beams including the effects of changes coupled physical characteristics of concrete cross-sections as well as the growth of the micro- and macro-cracks are presented in this paper. Theoretical results of the deformations are compared with the experimental values for two cases of solved beams. Good agreement can be seen between theoretical and experimental results of the deformations in the cracked zone.