Multiaxial Fatigue Strength to Notched specimens made of 40CrMoV13.9

Abstract

Fatigue is a process (succession of mechanisms) which under the action of time-varying strains or deformations modifies the local properties of a material. These can lead to the formation of cracks and eventual rupture of the structure. Fatigue is in particular characterized by an extent of variation in stress which may be well below the yield strength of the material. The main stages of fatigue failure of an assembly are the initiation of cracks (if defects are not already present in the material), the propagation of cracks and the final rupture. The parameters often used to predict the fatigue behavior and thus the number of cycles at break of a structure is: The amplitude of the stress (loading or imposed strain), its average value, the surface state and the medium In which the structure will be used. Even if the study of fatigue is based on theoretical considerations (in particular the mechanics of the rupture), it is essentially an experimental field. The characterization of a material, a part, an assembly, a structure, requires numerous tests and measurements. The work deals with multiaxial fatigue power of specimens which are notched and all made of 40CrMoV13.9. Circumferentially V-notched specimens and semicircular notched were tested under combined tension and torsion loading, both, in phase or out of phase. Geometry of symmetric axis of V notched issues has been characterized of a notch radius constant from (1 mm) and V-notch opening angle of 90°. The semicircular specimens were characterized by a constant notch tip radius. For both situations the net diameter sectional area was 12 mm. The results from multi-axial tests are discussed together with those obtained being all under loading pure torsion and tension by the issues notched having the same geometry. Altogether more than 120 new fatigue data are summarized in the present work. All presented fatigue data are first in terms of nominal amplitudes stress and then reanalyzed in terms of the mean value of the strain energy density evaluated over a finite size semicircular sector surrounding the tip of the notch.

Effect of nano silica (SiO2) on the hydration kinetics of cement

“…From the chemical composition of Portland cement, the peaks can possibly be assigned to the CaO and the SiO2 respectively [12]. Second, the spectra for the hydrated 3, 7, 28, and 56 days water and vacuum cured samples were recorded followed by the subtraction of the reference dry cement spectrum [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. The purpose of the subtraction is to remove the bonds of the reference material away from that of the hydrated specimens.…”

Validation of notch stress estimation schemes for low C–Mn steel

“…Further, these locations are bound to setup stress/strain gradients. Earlier tests investigations 1–9 have shown a significant effect of multiaxiality and strain gradients on fatigue life. For fatigue design qualification of notched components, generally, a three‐steps‐procedure is followed.…”

The Strain energy density to estimate lifetime of notched components subjected to variable amplitude fatigue loading

“…The control radius R0 of the volume is a material property, which involves the plain specimen's fatigue limit and the threshold stress intensity factor range [10]. The approach was successfully used under both static and CA fatigue loading conditions to assess the strength of notched components subjected to uniaxial [12][13][14] as well as to multiaxial loading [15][16][17][18][19].…”