Vâlcu ROŞCA


25-68 PROPAGAREA FISURII LA OBOSEALĂ AXIAL- EXCENTRICĂ. MODELE DE STUDIU

THE CRACK PROPAGATION AT ECCENTRICALLY
TENSILE FATIGUE TEST. STUDY MODELS
The study consists in crack propagation analysis in a plate specimen
CT model with side notch, made by a R520 steel. The specimen is loaded to a
eccentrically tensile test. The loading asymmetry factors are: R = 0.1 and R =
0.3, and the loading temperature is the room temperature, T = 293K.
The defect seeding rate in the specimen material marked as da/dN
was analysed by the empiric mathematical models: 1° – a second degree
polynomial method of approximation; 2º – according to Paris formula and, 3° –
respectively to Walker model. By using the three methods, there was
determined the crack propagation rate variation da/dN versus the crack length
variation a1, respectively versus the stress intensity factor ΔK.
Keywords: cyclic, request coefficient of asymmetry, cracking, cracking
speed, intensity factor in blood (FIT)
Cuvinte cheie: solicitare ciclică, coeficient de asimetrie, fisură, viteză
de fisurare, factor de intensitate a tensiunii (FIT)
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21-108 STUDIUL VITEZEI DE CREŞTERE A FISURII ÎN RAPORT CU MODELUL MATEMATIC PROPUS

STUDY OF SPEED INCREASE OF THE CRACK
IN RELATION TO MATHEMATICAL MODEL PROPOSED
It has been carried out a study of the crack propagation rate in testpieces
with flat model CT, with side notch, from a 10TiNiCr175 mark stainless,
by three known variants: polynomial method according to ASTM 647-95, Paris
method and Forman method. It was examined the influence of temperature
variation to low values, for an axial cyclic eccentric strain. Asymmetry coefficient
by working was R = 0,3, and the temperatures T = 293 K, T = 253 K,
respectively T = 213 K.
Cuvinte cheie: solicitare ciclică, coeficient de asimetrie, fisură, viteză
de fisurare, factor de intensitate a tensiunii
Keywords: application cyclical asymmetry coefficient, crack, crack
speed, voltage intensity factor

108 STUDIUL VITEZEI DE CREŞTERE A FISURII ÎN