scholarly journals Evaluation of Weldment Creep and Fatigue Strength-Reduction Factors for Elevated-Temperature Design

1990 ◽  
Vol 112 (4) ◽  
pp. 333-339 ◽  
Author(s):  
J. M. Corum
Keyword(s):  
Elevated Temperature ◽  
Fatigue Strength ◽  
The United States ◽  
Fatigue Tests ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
Nuclear Component ◽  
American Society ◽  
Reduction Factors

New explicit weldment strength criteria in the form of creep and fatigue strength-reduction factors were recently introduced into the American Society of Mechanical Engineers Code Case N-47, which governs the design of elevated-temperature nuclear plant components in the United States. This paper provides some of the background and logic for these factors and their use, and it describes the results of a series of confirmatory creep-rupture and fatigue tests of simple welded structures. The structures (welded plates and tubes) were made of 316 stainless steel base metal and 16-8-2 weld filler metal. Overall, the results provide further substantiation of the validity of the strength-reduction factor approach for ensuring adequate life in elevated-temperature nuclear component weldments.

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.

A Probabilistic Model of Size Effect in the Fatigue Strength of Rounds in Bending and Torsion

1980 ◽  
Vol 102 (1) ◽  
pp. 32-37
Author(s):  
C. R. Mischke
Keyword(s):  
Fatigue Strength ◽  
Probabilistic Model ◽  
Fatigue Tests ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Probabilistic Design ◽  
Strength Reduction Factor ◽  
Design Procedures ◽  
Endurance Strength ◽  
The Mean

The use of a probabilistic premise to establish the relation of size to the attenuation of endurance strength in rounds, such as shafts subjected to bending or torsion is investigated. The method allows the designer to construct the appropriate expression for Marin fatigue strength reduction factor, kb, directly from fatigue tests that have been ordered. For probabilistic design procedures, the mean and standard deivation of the Marin fatigue strength reduction factor are required, and the method described allows these estimates to be made.

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.

The Effect of Multiaxiality on the Evaluation of Weldment Strength Reduction Factors in High-Temperature Creep

1994 ◽  
Vol 116 (1) ◽  
pp. 76-80 ◽  
Author(s):  
R. Sandstro¨m ◽  
S.-T. Tu
Keyword(s):  
Transfer Function ◽  
Weld Metal ◽  
Creep Strength ◽  
Rupture Strength ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
Welded Tube ◽  
Metal Creep ◽  
Reduction Factors

The conventional way to define the weldment creep strength reduction factor is usually based on uniaxial creep data of weld metals and parent metals. In order to take the multiaxial effect into consideration, this paper has defined a structural transfer function which can be evaluated from general creep stress analysis. An analytical model is then proposed in the light of the function. Two numerical examples of typical weld properties show that the transfer function has a load-independent feature, which allows one to obtain multiaxial stress components in a weldment through minimal computation effort. Fairly good estimation of the stress level in the weld metal is achieved. On the basis of the present semi-analytical procedure, the weldment creep strength reduction factors are evaluated. For a 0.5Cr0.5Mo0.25V butt-welded tube under internal pressure, which has a higher weld metal creep-rupture strength, and lower weld metal creep strain rate, the reduction factors range from 0.9 to 0.95. For the AISI 316 butt-welded tube of cold-worked parent metal and creep soft weld metal, lower strength reduction factors are found, but they may still be nonconservative due to stress enhancement in the heat-affected zone.

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
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