scholarly journals Notch Effect in Low Cycle Fatigue : 1st Report, Some Considerations on Fatigue Strength Reduction Factor by Round-Bar Specimens with Circumferential Notches

1969 ◽  
Vol 12 (52) ◽  
pp. 673-682 ◽  
Author(s):  
Teruyoshi UDOGUCHI ◽  
Shunsaku MITSUHASHI ◽  
Tomoyuki WADA
Keyword(s):  
Fatigue Strength ◽  
Low Cycle Fatigue ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Notch Effect ◽  
Cycle Fatigue ◽  
Strength Reduction Factor ◽  
Round Bar

Design of Pressure Vessels for Low-Cycle Fatigue

1962 ◽  
Vol 84 (3) ◽  
pp. 389-399 ◽  
Author(s):  
B. F. Langer
Keyword(s):  
Fatigue Strength ◽  
Pressure Vessel ◽  
Low Cycle Fatigue ◽  
Fatigue Curve ◽  
Pressure Vessels ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
The Mean ◽  
Fatigue Evaluation

Methods are described for constructing a fatigue curve based on strain-fatigue data for use in pressure vessel design. When this curve is used, the same fatigue strength-reduction factor should be used for low-cycle as for high-cycle conditions. When evaluating the effects of combined mean and alternating stress, the fatigue strength-reduction factor should be applied to both the mean and the alternating component, but then account must be taken of the reduction in mean stress which can be produced by yielding. The complete fatigue evaluation of a pressure vessel can be a major task for the designer, but it can be omitted, or at least drastically reduced, if certain requirements can be met regarding design details, inspection, and magnitude of transients. Although the emphasis in this paper is on pressure vessel design, the same principles could be applied to any structure made of ductile metal and subjected to limited numbers of load cycles.

scholarly journals Failure mechanisms and fatigue strength reduction factor of a Cr-Ni-Mo-V steel welded joint up to ultra-long life regime

2018 ◽  
Vol 165 ◽  
pp. 21012 ◽  
Author(s):  
Ming-Liang Zhu ◽  
Fu-Zhen Xuan
Keyword(s):  
Fatigue Strength ◽  
Base Metal ◽  
High Cycle Fatigue ◽  
Welded Joint ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Cycle Fatigue ◽  
Strength Reduction Factor ◽  
Fatigue Design ◽  
Very High

It is known that welded joint is much “weaker” than base metal due to discontinuities of geometry, materials and residual stresses. It seems current international design rules do not adopt a uniform approach to weld efficiency, which is often defined as the ratio of the strength of a welded joint to the strength of base metal, in their guidance for creep and fatigue design of welds. This appears to be a great barrier for the application of nuclear welded structures which has a prolonged design lifetime of 60 years. In this work, fatigue strength reduction factor of a Cr-Ni-Mo-V steel welded joint, machined from welded steam turbine rotors for nuclear power plant, was investigated by performing axially push-pull cyclic loads tests with both cross-weld and pure base metal specimens up to very high cycle fatigue regime under ultrasonic frequency at ambient temperature. The effects of residual stress, strain localization, and microdefects in mismatched steels on failure mechanisms of welds were discussed thoroughly. Results show that fatigue strength reduction factor is varied in the range of 0.95-0.975, and is found to be dependent on fatigue lifetime for the first time. It is indicated that variation of fatigue strength reduction factor are associated with transition of crack initiation from specimen surface in high cycle fatigue regime to interior micro-defects in very high cycle fatigue regime. Comparing existing codes and standards for fatigue design of welds with experimental data indicates the over-conservativeness of present code-based design method. This implies a micro-defect based fatigue design approach is required for long life safe and reliability of weldments.

Fatigue life evaluation of an ultrafine-grained pure aluminum

2019 ◽  
Vol 234 (1) ◽  
pp. 90-104
Author(s):  
Alireza Babaei ◽  
Firooz Esmaeili-Goldarag ◽  
Hossein Jafarzadeh
Keyword(s):  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Pure Aluminum ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
Dislocation Dynamic ◽  
Constitutive Material Model ◽  
Ultrafine Grained ◽  
Cyclic Extrusion Compression

The aim of this study is an experimental and numerical investigation of the fatigue behavior of a notched ultrafine-grained pure aluminum processed by strip cyclic extrusion-compression method. In this regard, the fatigue experiments were conducted for the unprocessed and strip cyclic extrusion-compression processed specimens under various cyclic loads. In the numerical analyses, a dislocation dynamic constitutive material model which tracks the microstructure evolution was implemented for numerical estimation of the values of fatigue strength reduction factor via the volumetric approach. Considering the three-dimensional effect near the plate hole, the variation of the fatigue notch factor through the thickness of the plate was investigated and the obtained results showed that maximum fatigue strength reduction factor was occurred in the middle of the plate due to the symmetry of specimen geometry and loading condition. The investigation reveals a good agreement between the numerical and experimental lives. The results showed although the smooth processed specimens have higher fatigue strength in comparison of the unprocessed ones, the notched processed specimens have lower fatigue strength in comparison of the unprocessed ones.

346 Fatigue Strength Reduction Factor of Notched Plates subjected to Cyclic Bending Load

2001 ◽  
Vol 2001 (0) ◽  
pp. 323-324
Author(s):  
Yoshio FUKUDA ◽  
Masakazu KANOU ◽  
Satoshi SUKEGAWA ◽  
Kazuya WATANABE ◽  
Ryukichi KENJOU
Keyword(s):  
Fatigue Strength ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
Cyclic Bending ◽  
Bending Load

Analytical Study on Fatigue Strength Reduction Factor of Small-Diameter Socket-Welded Pipe Joints

1998 ◽  
Vol 120 (2) ◽  
pp. 157-163 ◽  
Author(s):  
M. Higuchi ◽  
A. Nakagawa ◽  
K. Iida ◽  
M. Hayashi ◽  
T. Yamauchi ◽  
...  
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Welded Joints ◽  
Small Diameter ◽  
Large Change ◽  
Fatigue Tests ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
Welded Pipe

Four-point bending and rotating bending fatigue tests were conducted on socket-welded joints made of carbon, stainless, and Cr-Mo steels for clarification of the effects of diameter, welding pass sequence and post-weld heat treatment (PWHT) on fatigue strength. The results were evaluated quantitatively. Fatigue strength of socket-welded joints was found to strongly depend on weld pass sequences in fillet welds, this being possibly due to large change in residual stress distribution at roots and toes. The effects of residual stress were thus examined quantitatively by comparison of fatigue strength of PWHT stress-free specimens with that of as-welded specimens. By the modified Goodman’s method, the lowest S-N curve corresponding to maximum tensile residual stress and the highest S-N curve corresponding to maximum compression residual stress were obtained for different steels and diameters. Conventional S-N data of socket-welded joints were situated between these two limiting curves. Based on the lowest curve, fatigue strength reduction factors of socket-welded joints were proposed.

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