National Repository of Grey Literature 274 records found  beginprevious265 - 274  jump to record: Search took 0.07 seconds. 
Quantitative assessment of the surface relief in fatigue using AFM
Man, Jiří ; Obrtlík, Karel ; Polák, Jaroslav
Atomic force microscopy (AFM) was applied to study the early stages of fatigue damage in polycrystalline copper and stainless 316L steel. The analysis of the image formation using an AFM tip reveals the lateral distortion of the extrusions and intrusions in case of high extrusions and deep intrusions. The true extrusion height can be obtained in direct observation and the depth of intrusions using replica technique. The evolution of the shape and the height of extrusions allowed to judge the activity of the persistent slip bands (PSBs) during fatigue life.
Effect oc surface carburizing on low cycle fatigue of 316L austenitic stainless steel
Obrtlík, Karel ; Polák, Jaroslav
Both surface carburized and untreated 316L stainless steel specimens were cyclically loaded with constant plastic strain amplitude. Characteristics of stress strain response and fatigue life were evaluated and surface relief evolution and crack initiation was studied.
The effect of V-notch on the propagation rate of fatigue crack
Hutař, Pavel ; Knésl, Zdeněk
The rate of a fatigue crack propagating in a vicinity of a V-notch is studied. To assess the influence of the constraint on the rate of the propagation, two parameter constraint based linear elastic fracture mechanics is used. The corresponding values of the T-stress are calculated and values of the effective stress intensity factor Keff controlling the rate of a crack propagation are estimated as a function of the V-notch opening angle. The results obtained are compared with those for a crack emanating from nonsingular U- notch concentrator.
The influence of T-stress on the characteristics of a fatigue crack
Hutař, Pavel
The influence of the T-stress values on the propagation of fatigue cracks is analyzed. The parameters of the plastic zone are studied at two levels of applied stress, i.e. loading and unloading. The CTOD parameter and rp (plastic zone size) in the crack grow direction are discussed as a driving parameter of a fatigue crack propagation rate. The three ways of determination of propagation rate of a fatigue cracks are compared. Recommendations for applications of these methods are discussed.
Factors determining lifetime of single crystalline gas turbine blades
Lukáš, Petr ; Kunz, Ludvík ; Obrtlík, Karel ; Čadek, Josef
Creep, low-cycle fatigue and creep/fatigue tests were performed on Nickel base superalloy CMSX-4 at high temperatures. It has been shown that the crystal orientation has a strong influence on creep and low-cycle fatigue resitance. Results of creep/fatigue experiments show that small vibrations exhibit a beneficial effect on creep rate.
Statistical analysis of effect of magnitude and shape if initial imperfections in thin-walled girder
Kala, Z. ; Škaloud, Miroslav
The results of statistical analysis of experimentally found girder slender web geometrical imperfections are given in the present paper.

National Repository of Grey Literature : 274 records found   beginprevious265 - 274  jump to record:
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