The Size Effect in Fatigue of Plain and Notched Steel Specimens Loaded under Reversed Direct Stress

1951 ◽  
Vol 165 (1) ◽  
pp. 113-124 ◽  
Author(s):  
C. E. Phillips ◽  
R. B. Heywood
Keyword(s):  
Fatigue Strength ◽  
Size Effect ◽  
Mild Steel ◽  
Fatigue Limit ◽  
Laboratory Tests ◽  
Chromium Steel ◽  
Fatigue Tests ◽  
Strength Reduction ◽  
Engineering Practice ◽  
Nickel Chromium

The fatigue strength under reversed direct stress was ascertained for specimens of various diameters in the range from 0·19 inch to 2·4 inches, the largest diameter being determined by the capacity of the machines available. Two steels were used in this investigation—a 25-ton mild steel and a 65-ton, per cent nickel-chromium steel. The specimens were either plain or notched (transverse hole) and, as far as possible, geometrical similarity was preserved with regard to the transition radii and the diameter of the transverse hole. A few fatigue tests on other types of notch, such as a circumferential V-groove and a shoulder, were also carried out. No intrinsic size effect with either material was observed with the plain specimens. With transverse-hole specimens in mild steel, the fatigue limit was ±8·4 tons per sq. in. for specimens of 0·33 inch diameter, and 6·1 tons per sq. in. for specimens of 1·7 inches diameter, thus showing that an appreciable size effect was present. A similar size effect was found with the alloy steel specimens containing a transverse hole, and fatigue limits of ±17·1 and ±13·9 tons per sq. in. respectively were obtained for these two sizes of specimen. It is suggested that the low values of fatigue-strength reduction factors usually associated with mild steel as a result of laboratory tests do not apply to the larger sections of this material commonly employed in engineering practice.

scholarly journals Effect of micro-notches on fatigue strength of electrodeposited nanocrystalline nickel thin films

2018 ◽  
Vol 165 ◽  
pp. 04011
Author(s):  
Keisuke Tanaka ◽  
Yuta Murase ◽  
Hirohisa Kimachi
Keyword(s):  
Thin Films ◽  
Fatigue Strength ◽  
Fatigue Limit ◽  
Stress Ratio ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Fine Grained ◽  
Nickel Thin Films ◽  
Nano Crystalline ◽  
Fictitious Crack

The effect of micro-notches on the fatigue strength of nickel thin films was studied. Two types of thin films with 10 μm thickness were produced by electrodeposition using sulfamate solution without and with brightener: ultra-fine grained film (UFG) with the grain size of 384 nm and nano-crystalline grained film (NCG) with that of 17 nm. Micro-sized notches introduced by FIB had the width of 2 μm and various depths from 8 to 150μm. Fatigue tests were conducted under the stress ratio of 0.1. The fatigue strength decreased with increasing depth of notches. NCG had much higher strength than UFG compared at the same notch depth. Notches as small as 8μm did reduce the fatigue strength of both UFG and NCG. The fatigue limit was controlled by the initiation of cracks and no non-propagating crack was observed in specimens fatigued below the fatigue limit. A model of fictitious crack successfully predicted the reduction of the fatigue limit due to micro-notches. The characteristic crack length of NCG was much smaller than the UFG, while the fatigue strength of defect-free NCG was larger than that of UFG. SEM observation of fracture surfaces was conducted to reveal micromechanisms of fatigue crack initiation.

Exploratory Tests on the Effects of Random Loading and Corrosive Environment on the Fatigue Strength of Fillet-Welded Lap Joints

1975 ◽  
Vol 17 (4) ◽  
pp. 181-185 ◽  
Author(s):  
K. J. Marsh ◽  
T. Martin ◽  
J. McGregor
Keyword(s):  
Fatigue Strength ◽  
Mild Steel ◽  
Narrow Band ◽  
Fatigue Tests ◽  
Lap Joints ◽  
Corrosive Environment ◽  
Test Frequency ◽  
Constant Amplitude ◽  
Random Loading ◽  
Loading Tests

Fatigue tests on simple, fillet-welded, mild steel lap joints have been carried out to determine the effects of a corrosive environment and random loading. At normal testing frequencies, a brine-drip environment had no effect on the constant-amplitude fatigue strength at short endurances. At stresses less than the in-air fatigue limit, the corrosive environment was sufficient to allow crack growth at very low stress levels. In these corrosive environment tests, reducing the test frequency by a factor of 50 halved the life. The results of narrow-band random loading tests could be predicted reasonably accurately either by a fracture mechanics method or by Miner's rule.

Influence of Strength Level of Steels on Fatigue Strength and Fracture Morphology of Spot Welded Joints

2011 ◽  
Vol 462-463 ◽  
pp. 94-99
Author(s):  
Keiichiro Tohgo ◽  
Tomoya Ohguma ◽  
Yoshinobu Shimamura ◽  
Yoshifumi Ojima
Keyword(s):  
Finite Element ◽  
Fatigue Strength ◽  
Mild Steel ◽  
Welded Joints ◽  
High Strength ◽  
Fracture Morphology ◽  
Fatigue Tests ◽  
Finite Element Analyses ◽  
Ultra High Strength Steel ◽  
Spot Welded

In this paper, fatigue tests and finite element analyses are carried out on spot welded joints of mild steel (270MPa class) and ultra-high strength steel (980MPa class) in order to investigate the influence of strength level of base steels on fatigue strength and fracture morphology of spot welded joints. From the fatigue tests the following results are obtained: (1) Fatigue limit of spot welded joints is almost the same in both steels. (2) Fatigue fracture morphology of spot welded joints depends on the load level in the ultra-high strength steel, but not in the mild steel. From discussion based on the finite element analyses the following results are obtained: (3) The fatigue limit of spot welded joints can be predicted by stress intensity factors for a nugget edge, fracture criterion for a mixed mode crack and threshold value for fatigue crack growth in base steel. (4) Plastic deformation around a nugget in spot welded joints strongly affects the fatigue fracture morphology.

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.

Research of Fatigue Limit and Stress Concentration on Structural Steel with Double-Notches

2009 ◽  
Vol 419-420 ◽  
pp. 849-852
Author(s):  
Sheng Wu Wang ◽  
Shu Juan Sun ◽  
Ai Ling Wen ◽  
Wei Da Wang ◽  
Shinichi Nishida
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Strength ◽  
Stress Concentration ◽  
Fatigue Limit ◽  
Three Dimensional ◽  
Fatigue Tests ◽  
Notched Specimen ◽  
Blind Hole ◽  
Element Method

The fatigue limit of parts and components that have the multi-notches is important data for the design and manufacture of machinery and traffic equipment which are operated under the high speed or pressure. In this paper the rotating bending fatigue tests have been carried out to investigate the fatigue limit of specimen with double-notch that is constructed of step and blind hole, and analyzed the effect of stress concentrations at the double-notched bottoms on the fatigue limits, using three-dimensional elastic finite element method. Firstly, the fatigue tests of 8 group specimens have been performed for examining the of fatigue limits of the single-notched specimen and double-notched specimen, respectively. Additionally, the stress field interactions between two stress fields by the blind hole notch and step are discussed using three-dimensional elastic finite element method. The main results obtained in this study are as follows: The fatigue limit of the double-notched specimen are down comparison with the fatigue limit of the single-notched specimen; the fatigue limit of the double-notch specimen is insensitive to distance between the blind hole and step for the low carbon structure steel with better ductility; for the high-strength steel, superposition and intensification of the stress concentration by the blind hole and step mutually may be avoided so that their adverse effects on the fatigue strength may be become to minimize, as take appropriate distance between the blind hole and step. The results are significant for the design of engineering design of the multi-notched parts, and the study of fatigue strength.

Study on Consideration of Size Effects on Design Fatigue Curve

2014 ◽  
Author(s):  
Akihiko Hirano ◽  
Motoki Nakane ◽  
Seiji Asada ◽  
Takehiko Sera
Keyword(s):  
Fatigue Life ◽  
Size Effect ◽  
Fatigue Limit ◽  
Fatigue Curve ◽  
Fatigue Tests ◽  
Specimen Size ◽  
Compression Loading ◽  
Axial Tension ◽  
Current Design ◽  
Tension And Compression

Published works on studying effects of specimen size on fatigue endurance limit and fatigue life were reviewed. Specimen size effect is apparent in many bending fatigue tests. However, axial tension and compression loading fatigue tests showed that the fatigue limit decreased slightly with increasing specimen size. Design margin for the size effect on fatigue limit under axial tension and compression loading condition that is the condition of the data used to construct Design Fatigue Curve (DFC) is not considered to be necessary. If it is considered conservatively, the value less than 1.1 is enough. Axial tension and compression loading fatigue tests using cylindrical specimens having different diameters showed that the fatigue life increased with increasing specimen diameter. This phenomenon is considered to occur due to the crack growth life which is not negligible in relatively large diameter specimens. Based on this, design margin factor on number of cycles is not necessary to be considered in DFC. These design margins based on the axial tension and compression loading fatigue test results are less than the values in current design codes. This indicates that the current design fatigue curves in the codes have large margins. These considerations will be verified after the large scale fatigue tests that are planned in Design Fatigue Curve (DFC) subcommittee in the Atomic Energy Research Committee in the Japan Welding Engineering Society.

Fretting Corrosion and Fatigue Strength: Brief Results of Preliminary Experiments

1941 ◽  
Vol 146 (1) ◽  
pp. 32-38 ◽  
Author(s):  
E. J. Warlow-Davies
Keyword(s):  
Fatigue Strength ◽  
Accurate Estimate ◽  
Fatigue Tests ◽  
Medium Carbon Steel ◽  
Fretting Corrosion ◽  
Medium Carbon ◽  
Chemical Corrosion ◽  
Nickel Chromium ◽  
Test Pieces ◽  
Percentage Loss

Fretting corrosion, the conditions under which it occurs, and the possibility of its effect on fatigue strength, are discussed. Fretting corrosion always appears in regions of unknown stress concentration, so that an accurate estimate of the weakening effect due to it cannot be made from combined fretting and fatigue tests. It is suggested that fatigue tests of previously fretted test pieces, analogous to determinations of the percentage loss of fatigue strength by prior stressless chemical corrosion, would be useful. Apparatus for making such tests is described, and preliminary results for a medium-carbon steel and for a nickel-chromium-molybdenum alloy stéel are given. The losses of fatigue strength after fairly severe fretting were 13 per cent and 18 per cent respectively. Although these are not necessarily maximum values, reductions of this order are regarded as justifying further investigation, and the suitability of the apparatus and methods used is considered.

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.

Fatigue Characteristics of Bolted Joint under Transverse Vibration ~Influence of Bolt Tightening Conditions on Transverse Fatigue Strength~

2010 ◽  
Vol 452-453 ◽  
pp. 609-612
Author(s):  
Shinji Hashimura ◽  
YU Kurakake ◽  
Shinichi Umeno
Keyword(s):  
Fatigue Strength ◽  
Fatigue Limit ◽  
Transverse Vibration ◽  
Bending Moment ◽  
Fatigue Tests ◽  
Bolted Joint ◽  
The Real ◽  
Thread Length ◽  
Fatigue Characteristics

Fatigue tests under transverse vibration were performed for three separate tightening conditions to investigate the grip length and the engaging thread length in this study. The relationships between the apparent fatigue limit (the highest amplitude of transverse vibration force which can be applied to the bolted joint without generating fatigue) and the real fatigue limit of bolt material also were investigated. Results showed that apparent transverse fatigue limit decreased if the grip length was long. And relationships of the apparent fatigue limit and the real fatigue limit were different in each tightening conditions depending on the bending moment at the root of the first thread.

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