Vejvoda, S.

Influence of the multi-axis state of stresses on fatigue

Abstract eng:
Damage of materials by fatigue at varying loading is influenced by different factors such as welding, multi axis state stress and environment. Results of cyclic loading on fatigue for multi-axis state of stresses are compared with calculation on fatigue for the strain amplitude determined by the finite element method using the program ANSYS. The Manson-Coffin fatigue curve, the cyclic curve and hysteresis loop were measured for the S355NL steel. This steel was used for the manufacturing of the tested samples with the openings and the notch. The detailed category of the strength weld of lamellar flanges was determined. 1 RESEARCH FOCUS The effects of multi-axis state of stresses and gradient of stresses on fatigue of materials were verified experimentally by cyclic loading of large Flat Samples (FS) with holes and of Cylindrical Samples (CS) with a circumferential groove. The experiment results were compared with the numerical calculation on fatigue. Strains and stresses in a geometric notch were calculated in the elastic plastic state by the finite element methods using program ANSYS. Calculated strain amplitudes and middle stresses were inserted into the fatigue strength curve of the Manson-Coffin type (1) and (2). From these were calculated the number of cycles to fatigue crack creation. Parameters of fatigue strength curve of the Manson-Coffin type were measured using standard samples, made from steel S355 J2 + N and S355 NL+N. 2 FATIGUE TESTS Specimens were filled with strain gauges to identify creation of plastic strains and fatigue cracks. Strain gauges were placed into potential sites for fatigue cracks. There were tested 17 samples [1]. The size of these samples was selected so that plastic strains will be created only in the part of the cross section near of the notch. The flat samples were made with holes, three of them had one hole, another three had three holes in the vertical direction and the other two had three holes in horizontal direction. Nine cylindrical test samples were divided into three groups of three, differed from each notch dimensions: depth/width/ rounding of the bottom: 5/2/1; 3/2/1, 3/4/2 mm. Examples are shown in the Figures 1, 2 and 3.

Publisher:

Taylor and Francis Group, London, UK

Conference Title:

Insights and Innovations in Structural Engineering, Mechanics and Computation

Conference Title:

Sixth International Conference on Structural Engineering, Mechanics and Computation

Conference Venue:

Cape Town, South Africa

Conference Dates:

2016-09-05 / 2016-09-07

Rights:

Text je chráněný podle autorského zákona č. 121/2000 Sb.