Non-Propagating Cracks in Vee- Notched Specimens Subject to Fatigue Loading

1957 ◽  
Vol 8 (1) ◽  
pp. 1-20 ◽  
Author(s):  
N. E. Frost
Keyword(s):  
Fatigue Limit ◽  
Fatigue Loading ◽  
Critical Value ◽  
Chromium Steel ◽  
Fatigue Tests ◽  
Reduction Factor ◽  
Strength Reduction Factor ◽  
Notched Specimens ◽  
Specimen Material ◽  
Rotating Bending Fatigue

SummaryReversed direct stress and rotating bending fatigue tests have been carried out on Vee-notched specimens of aluminium alloy, nickel chromium steel and mild steel.Diagrams are presented showing the relationship between the geometric stress concentration factor Kt and the strength reduction factor Kt. It was found that non-propagating cracks formed in the roots of the sharper notches. These cracks formed at or above some critical value of Kt, the value depending on the specimen material. Below the critical value of Kt, cracks did not form unless the applied nominal stress exceeded that at the fatigue limit, and a crack, once formed, continued to propagate until the specimen failed. Above the critical value of Kt, non-propagating cracks formed at nominal stresses less than the fatigue limit, the stress having to be increased to the latter value in order to propagate the crack. This critical value of Kt coincided with the maximum Kf value realised. It would appear that Kf equals Kt up to a certain value of Kt; there is then a transition where Kt reaches a maximum at the critical value of Kt. Increasing the value of Kt above the critical value causes no further increase and may tend to decrease the value of Kt.The conclusions drawn apply only when the fatigue stresses are completely reversed, i.e. the mean load is zero.

Application of Two Methods for Notch Fatigue Life Prediction

2011 ◽  
Vol 488-489 ◽  
pp. 654-657
Author(s):  
Radu Negru ◽  
Liviu Marsavina ◽  
Hannelore Filipescu ◽  
Cristiana Caplescu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Reduction Factor ◽  
Volumetric Method ◽  
Life Assessment ◽  
Strength Reduction Factor ◽  
Element Analysis ◽  
Linear Elastic ◽  
Notched Specimens

The aim of this paper is the application of two methods for notch fatigue life assessment, methods which are based on finite element analysis: the theory of critical distances and the volumetric method. Firstly, un-notched and notched specimens (for three different geometries) were tested in tension under constant-amplitude loading. The use of theory of critical distances (TCD) to predict the notch fatigue life involves the determination of the material characteristic length L based on experimental results obtained for the un-notched and one type of notched specimens. For the others notched geometries, based on linear-elastic finite element analysis, the fatigue strength is predicted using the TCD. In order to apply the volumetric method, elastic-plastic stress field around notches are considered and notch strength reduction factor are determined. Finally, the predictions of the two methods were compared with experimental fatigue data for notched specimens.

A Study of the Notch Effect and of Specimen Design and Loading on the Fatigue Properties of Cast Steel

1968 ◽  
Vol 90 (1) ◽  
pp. 51-57 ◽  
Author(s):  
J. F. Wallace ◽  
C. Vishnevsky ◽  
C. W. Briggs
Keyword(s):  
Endurance Limit ◽  
Fatigue Testing ◽  
Cast Steel ◽  
Fatigue Tests ◽  
Reduction Factor ◽  
Fatigue Properties ◽  
Research Report ◽  
Notch Effect ◽  
Percent Reduction ◽  
Strength Reduction Factor

Scope of the research report: The purpose of the research included in this report is to extend the knowledge on the fatigue properties of cast steel by presenting a study of the effect of notches on fatigue properties and the effect of specimen design and the method of loading on the fatigue properties of cast steel. Summary of the research report conclusions: (a) Notch Effect—A severe notch (0.015-in. radius) in fatigue testing of cast steel results in a 36 percent reduction in endurance limit based on unnotched specimens. An extremely severe notch (0.001 in. radius) results in a 42 to 53 percent reduction in the endurance limit. The fatigue strength reduction factor Kf for extreme notched specimens is appreciably higher for cast steel in the quenched and tempered condition. (b) Specimen Design and Loading—Cast steel exhibits better endurance properties in reversed torsion than reversed bending. Bending fatigue tests of cast steel tested at 1800 rpm result in lower endurance properties than rotating beam tests at 10,000 rpm. The difference is greater at the higher tensile strength level.

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.

scholarly journals Proposal of Fatigue Limit Design Curves for Additively Manufactured Ti-6Al-4V in a VHCF Regime Using Specimens with Artificial Defects

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 964
Author(s):  
Yoshihiko Uematsu ◽  
Toshifumi Kakiuchi ◽  
Yaodong Han ◽  
Masaki Nakajima
Keyword(s):  
Fatigue Limit ◽  
High Cycle Fatigue ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Design Curve ◽  
Very High Cycle Fatigue ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
The Relationship ◽  
Very High

Cantilever-type rotating bending fatigue tests were conducted under a very high cycle fatigue regime using conventionally manufactured Ti-6Al-4V specimens having drilled artificial defects with different sizes. The relationship between fatigue limit and defect size was defined as a fatigue limit design curve considering the transition from the fracture-mechanics dominating area to the fatigue-limit dominating area. A conventional Murakami’s equation was applicable as a design curve of additively manufactured Ti-6Al-4V with defects at 107 cycles. However, conventional equation gave un-conservative predictions for the fatigue limit at 108 cycles. Therefore, two kinds of modified Murakami’s equation were proposed as fatigue limit design curves for the very high cycle fatigue regime. Simple parallel shift of Murakami’s equation gave a conservative fatigue limit, whilst better result was obtained by changing the slope of Murakami’s equation. The proposed design curve was valid for the defect sizes ranging from 10 to 500 μm.

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.

Stress concentration on artificial pitting holes and fatigue life for aluminum alloy 6061-T6, undergoing rotating bending fatigue tests

2010 ◽  
Vol 1276 ◽  
Author(s):  
Víctor H. M. Lemus ◽  
Gonzalo M. D. Almaraz ◽  
J. Jesús V. Lopez
Keyword(s):  
Aluminum Alloy ◽  
Stress Concentration ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Stress Concentrations ◽  
Bending Fatigue ◽  
Aluminum Alloy 6061 ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
Alloy 6061

AbstractThis work deals with rotating bending fatigue tests on aluminum alloy 6061-T6, under loading condition close to the elastic limit of the material. Results have been obtained for three types of specimens: without artificial pitting, specimens with one artificial pitting hole and specimens with two neighboring artificial pitting holes. Results show that fatigue endurance is reduced in the case of one pitting hole and considerably for two neighboring pitting holes. In order to explain this behavior, numerical analysis by FE are carried out to determine the stress concentrations for the three types of specimens. It is found that the stress concentration for two neighboring pitting holes is an exponential function of the separation between the two holes, under uniaxial loading. The probability to find two or more neighboring pitting holes in real industrial materials, such as cast iron, corroded or pitting metallic alloys is high; then, the stress concentration for two or more neighboring pitting holes needs to be considered for the fatigue prediction life under fatigue loading and corrosion attack applications.

Sub-Surface Fatigue Strength of a Steel

1969 ◽  
Vol 11 (4) ◽  
pp. 432-443 ◽  
Author(s):  
P. F. Bray
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
Fatigue Limit ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Surface Fatigue ◽  
Test Pieces ◽  
Surface Failure ◽  
Rotating Bending Fatigue ◽  
Rotating Bending

Rotating bending fatigue tests on En 40B steel gave a fatigue limit for surface failure of 30·5 tonf/in2. With nitrided test-pieces sub-surface failures were produced and, with no allowance being made for residual stresses, a fatigue limit of 34·5 tonf/in2 was obtained for sub-surface failure. In the absence of residual stresses this fatigue limit would probably have been higher.

scholarly journals Improvement of rubber recipe for massive tires by addition of non-traditional fillers

2020 ◽  
Vol 81 (4) ◽  
pp. 196-204
Author(s):  
I. A. Litvinova ◽  
I. V. Veselov ◽  
Y. A. Gamlitskiy
Keyword(s):  
Fatigue Loading ◽  
Critical Value ◽  
Fatigue Tests ◽  
Operating Conditions ◽  
Fatigue Properties ◽  
Actual Operating ◽  
Strength Tests ◽  
Industrial Rubber ◽  
Fatigue Characteristics ◽  
Alternating Bending

We investigated the effect of new fillers on the properties of rubbers for solid tires. Modified by fullerenes and unmodified iron oxide fillers were used as new fillers. Fatigue characteristics were determined by two methods: multiple tension on the UR-500 device in accordance with GOST 261-79; alternating bending with rotation on the device SZPI in accordance with GOST 10952-75. The main tasks of constructing fatigue curves were to assess the compliance of the results of strength tests (tension at a constant speed to break) with fatigue in terms of fatigue life, fatigue strength, and fatigue energy density of fracture. In addition, the task was to verify the possibility of plotting on one Weller curve points obtained on different devices - UR 500 and ZPI. The ranking of rubbers in static does not coincide with each other. Since the fatigue loading conditions are closer to the actual operating conditions than the static ones, in order to predict the behavior of rubber goods in operation, one should focus on the results of fatigue tests. Combining the results of fatigue tests with repeated tension and with alternating bending with rotation showed that this procedure is valid, but only in cases where the temperature of self-heating on the ZPI device does not exceed a certain critical value when thermal decomposition begins. The results of fatigue tests showed that the use of the studied fillers with small degrees of filling (up to 30 mass parts) can be justified. An example is Ferrocolor fraction 0–20 ?m with a mass fraction of 5 m.h. In this case, the fatigue properties practically do not deteriorate in comparison with industrial rubber for solid tires, in which new fillers are not added.

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