Cumulative Damage in Push-Pull Fatigue of Fillet-Welded Mild Steel Plate Subjected to Narrow Band Random Loading

1970 ◽  
Vol 185 (1) ◽  
pp. 339-351 ◽  
Author(s):  
D. J. White ◽  
J. Lewszuk
Keyword(s):  
Mild Steel ◽  
Steel Plate ◽  
Narrow Band ◽  
Fatigue Tests ◽  
Cumulative Damage ◽  
Mean Stress ◽  
Constant Amplitude ◽  
Random Loading ◽  
The Relationship ◽  
Made In

Push-pull fatigue tests have been made in constant amplitude loading and in narrow band random loading on fillet-welded cruciforms made from 3/8 in thick mild steel plate to B.S. 1501-151 Grade 28. The test frequency was 250 Hz, mean tensile stresses of 0, 5 and 10 tonf/in2were employed and tests were extended for endurances of up to 108cycles. Curves have been fitted to the S-N results using the relationship N( S — So)α= C and on the assumption that this may be extrapolated beyond 108cycles, curves showing the effect of mean stress are given for both constant amplitude loading and narrow band random loading for endurances up to 1012cycles. Suitable factors of safety should be applied to these stresses before use in design. For endurances beyond 107cycles, an increase in tensile mean stress from 0 to 10 tonf/in2reduced the fatigue strength by about 50 per cent in both constant amplitude loading and random loading. Reasonable agreement was found at all mean stresses between the experimental random loading S-N curves and those predicted using the constant amplitude results and the Palmgren-Miner cumulative damage hypothesis.

Cumulative Damage in Fretting Fatigue of Pinned Joints Subjected to Narrow Band Random Loading

1970 ◽  
Vol 21 (4) ◽  
pp. 400-408 ◽  
Author(s):  
D. J. White ◽  
J. Lewszuk
Keyword(s):  
Tensile Stress ◽  
Narrow Band ◽  
Fatigue Tests ◽  
Cumulative Damage ◽  
Mean Square ◽  
Test Frequency ◽  
Constant Amplitude ◽  
Random Loading ◽  
Good Agreement ◽  
Made In

SummaryFatigue tests have been made in constant amplitude loading and in narrow band random loading on FV520B steel lugs of width 27 mm loaded by means of a pin 12·7 mm in diameter. The test frequency was 220 Hz, a mean tensile stress of 309 N/mm2 was used and tests extended for endurances of up to 109 cycles.For endurances up to 106 cycles there was good agreement between constant amplitude and random loading results with both stresses expressed in root mean square values. Beyond this endurance, the random loading results lay below those obtained in constant amplitude loading. Predictions made using the Palmgren-Miner cumulative damage hypothesis in conjunction with the endurance curve in constant amplitude loading gave good agreement with the results in random loading over the whole range of endurances tested.

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.

Narrow Band Random Fatigue Testing with Amsler Vibrophore Machines

1969 ◽  
Vol 11 (6) ◽  
pp. 598-604 ◽  
Author(s):  
D. J. White ◽  
J. Lewszuk
Keyword(s):  
Fatigue Testing ◽  
Narrow Band ◽  
Rayleigh Distribution ◽  
Fatigue Tests ◽  
Random Loading ◽  
Complete Control ◽  
Random Generator ◽  
Random Fatigue ◽  
Predetermined Time ◽  
Made In

A description is given of modifications made to Amsler Vibrophore machines to permit narrow band random fatigue tests to be made. In this mode of working, the machine electromagnet is excited by means of a random generator and a complete control loop is effected by connecting the output of the inductive transducer of the machine dynamometer to the automatic output regulator (compressor circuit) of the random generator. The dynamometer was strain-gauged and calibrated to read r.m.s. load. Under compressor circuit control, the stress peaks in a specimen followed the Rayleigh distribution at least up to four times the r.m.s. value. As in constant amplitude sinusoidal loading, these machines are capable of applying mean stress when working in random loading. Some practically occurring stress spectra may be synthesized by applying sequences consisting of a number of stepped r.m.s. loads, each step being applied for a predetermined time.

Corrosion Fatigue of AZ91E-T6 Cast Magnesium Alloy in a 3.5 Percent NaCl Aqueous Environment

1995 ◽  
Vol 117 (3) ◽  
pp. 293-298 ◽  
Author(s):  
R. I. Stephens ◽  
C. D. Schrader ◽  
K. B. Lease
Keyword(s):  
Fatigue Life ◽  
Magnesium Alloy ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Mean Stress ◽  
Constant Amplitude ◽  
Variable Amplitude ◽  
Cast Magnesium Alloy ◽  
Cast Magnesium ◽  
Variable Amplitude Fatigue

The objective of this research was to obtain and compare constant and variable amplitude fatigue behavior of AZ91E-T6 cast magnesium alloy in both an air and 3.5 percent NaCl aqueous corrosive environment. An additional objective was to determine if commonly used models that describe fatigue behavior and fatigue life are applicable to this material and test environment. Fatigue tests included constant amplitude strain-controlled low cycle fatigue with strain ratio, R, equal to 0, −1 and −2, Region II constant amplitude fatigue crack growth with load ratio, R, equal to 0.05 and 0.5 and variable amplitude fatigue tests using keyhole notched specimens. In all fatigue tests, the corrosion environment was significantly detrimental relative to the air environment. Mean strains influenced fatigue life only if accompanied by significant mean stress. The Morrow and Smith, Watson, and Topper mean stress models provided both accurate and inaccurate fatigue life calculations. Likewise, variable amplitude fatigue life calculations using the local strain approach and based upon the formation ofal mm crack at the keyhole notch were both accurate and fairly inaccurate depending on the specific model used.

scholarly journals Fatigue Characteristic of Designed T-Type Specimen under Two-Step Repeating Variable Amplitude Load with Low-Amplitude Load below the Fatigue Limit

2021 ◽  
Vol 9 (2) ◽  
pp. 107
Author(s):  
Jin Gan ◽  
Di Sun ◽  
Hui Deng ◽  
Zhou Wang ◽  
Xiaoli Wang ◽  
...  
Keyword(s):  
Stress Ratio ◽  
Type Specimen ◽  
Fatigue Tests ◽  
Cumulative Damage ◽  
Cyclic Loads ◽  
Constant Amplitude ◽  
Type Specimens ◽  
Variable Amplitude ◽  
Non Linear ◽  
Low Amplitude

In order to investigate the non-linear fatigue cumulative damage of joints in ocean structural parts, one type of low carbon steel Q345D was employed to prepare designed T-type specimens, and a series of fatigue experiments were carried out on the specimens under two-step repeating variable amplitude loading condition. The chosen high cyclic loads were larger than the constant amplitude fatigue limit (CAFL) and the chosen low cyclic loads were below the CAFL. Firstly, the S-N curve of designed T-type specimen was obtained via different constant amplitude fatigue tests. Then, a series of two-step repeating variable load were carried out on designed T-type specimens with the aim of calculating the cumulative damage of specimen under the variable fatigue load. The discussions about non-linear fatigue cumulative damage of designed T-type specimens and the interaction effect between the high and low amplitude loadings on the fatigue life were carried out, and some meaningful conclusions were obtained according to the series of fatigue tests. The results show that fatigue cumulative damage of designed T-type specimens calculated based on Miner’s rule ranges from 0.513 to 1.756. Under the same cycle ratio, the cumulative damage increases with the increase of high cyclic stress, and at the same stress ratio, the cumulative damage increases linearly with the increase of cycle ratio. Based on the non-linear damage evaluation method, it is found that the load interaction effect between high and low stress loads exhibits different damage or strengthening effects with the change of stress ratio and cycle ratio.

On Cumulative Damage in Impulse Fatigue Tests

1963 ◽  
Vol 85 (4) ◽  
pp. 535-538 ◽  
Author(s):  
S. Tanaka
Keyword(s):  
Mild Steel ◽  
Fatigue Failure ◽  
Fatigue Tests ◽  
Cumulative Damage ◽  
Experimental Results ◽  
Damage Effect ◽  
Repeated Application

Experimental results are presented for fatigue failure of mild steel specimens under repeated application of lateral impulses; the cumulative damage effect as a result of stresses arising from free-damped vibration of the specimen in the intervals between the repeated impulses is studied. A discussion on the conformity of these results with Miner’s hypothesis is given.

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