The Resistance of Metals to Cyclic Deformation

Landgraf, R. W.

doi:10.1520/stp26837s

Cited by 126 publications

(33 citation statements)

References 10 publications

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“…However, the number of 18 data sets for steel is sufficiently large that omitting any one data set and revising Eq. (20) will not significantly affect the comparison for the omitted data set. This contention was tested by omitting, one at a time, several of the data points that fell farthest from the fitted line of Fig.…”

Section: Trends In Fitted Walker γ Values For Steelsmentioning

confidence: 99%

Mean stress effects in stress‐life fatigue and the Walker equation

Dowling

Calhoun

Arcari

2009

Fatigue Fract Eng Mat Struct

248

178

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A B S T R A C T Mean stress effects in finite-life fatigue are studied for a number of sets of experimental data for steels, aluminium alloys and one titanium alloy. Specifically, the agreement with these data is examined for the Goodman, Morrow, Smith-Watson-Topper and Walker equations. The Goodman relationship is found to be highly inaccurate. Reasonable accuracy is provided by the Morrow and by the Smith-Watson-Topper equations. But the Morrow method should not be used for aluminium alloys unless the true fracture strength is employed, instead of the more usual use of the stress-life intercept constant. The Walker equation with its adjustable fitting parameter γ gives superior results. For steels, γ is found to correlate with the ultimate tensile strength, and a linear relationship permits γ to be estimated for cases where non-zero mean stress data are not available.Relatively high-strength aluminium alloys have γ ≈ 0.5, which corresponds with the SWT method, but higher values of γ apply for relatively low-strength aluminium alloys.For both steels and aluminium alloys, there is a trend of decreasing γ with increasing strength, indicating an increasing sensitivity to mean stress.A = intercept constant at 1 cycle for a stress-life curve b = exponent constant for a stress-life curve b w = exponent constant for a Walker method stress-life fit c = exponent constant for a plastic strain versus life curve d = intercept constant for multiple linear regression E = elastic modulus m 1 , m 2 = slope constants for multiple linear regression n = number of data points for an s z calculation N * = life for a given ε a for the σ m = 0 case N * w = value of N * from the Walker method N f = fatigue life; cycles to failure R = stress ratio, R = σ min /σ max s z = stress deviation; the standard deviation of z for a set of data z = normalized stress-direction deviation of a data point relative to a stress-life curve σ = stress range, σ = 2σ a ε a = strain amplitude ε ar = strain amplitude for σ m = 0 ε f = intercept constant at 1/2 cycle for a plastic strain versus life curve Correspondence: N. E. Dowling.

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Section: Trends In Fitted Walker γ Values For Steelsmentioning

confidence: 99%

Mean stress effects in stress‐life fatigue and the Walker equation

Dowling

Calhoun

Arcari

2009

Fatigue Fract Eng Mat Struct

248

178

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“…The TMT-75-74s15L had the same fatigue life as the 75% cold rolled samples yet a lower tensile strength. This behavior can be explained by the "toughness" [31] or a good combination of strength and ductility of TMT materials, which gives them good fatigue resistance in both high and low cycle fatigue regons. This kind of high fatigue strain capacity must resist the early development of microcracks as was pointed out by Manson [32].…”

Section: Discussionmentioning

confidence: 99%

Improvement of Fatigue Life of 1080 Steel by Thermomechanical Processing

Querales

Byrne

1979

Fatigue Fract Eng Mat Struct

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Abstract-Many thermomechanical treatments (TMT) have been applied in the past to alloys in order to improve the balance between various static mechanical properties. The current research has applied a given type of T M T to the improvement of fatigue behavior in eutectoid steel. The TMT involved the cold rolling of annealed eutectoid steel to a reduction in thickness of 75% followed by rapid heating in liquid lead to a temperature just above the A , temperature for a short time period and an air cool to room temperature. This type of TMT produces very oriented cementite in recrystallized ferrite. Plane bending cantilever fatigue tests with constant maximum load were run at 30 Hz and zero mean stress (R = -1.0). In terms of S-N fatigue curves the annealed condition is inferior to both the TMT and cold rolled conditions, however, there is no apparent advantage of the TMT over the &Id rolled condition. There is, however, a considerable advantage in the TMT which becomes evident with normalization of all S-N curves with respect to the ultimate tensile strength. One thus finds that the TMT is quite superior, on an equivalent strength basis, to both the cold rolled and annealed conditions. The same was true on a basis of hardness normalization. This means that by TMT one can produce fatigue properties in a material of much higher formability which are equivalent to or better than those in a cold rolled material. Samples oriented in the cross-roll direction had total fatigue lives longer than for those oriented in the roll direction. This is explained in terms of mechanical fibering of pearlite colonies and inclusions, and by a crystallographic texturing of the ferrite matrix.TMT strength is a result of austenite grain size refinement, reduction of interlamellar spacing, fiber strengthening and both solid solution and precipitate hardening.

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“…Both of the true fracture form and the stress intercept form of Morrow equation are shown in (2a) and (2b). The assumption of f = f is often accurate for steels, as shown by Landgraf [29]; however, for aluminums alloys the assumption shows less accuracy, as illustrated by Dowling et al [15].…”

Section: Mean Stress Models In Fatiguementioning

confidence: 99%

A Modified Walker Model Dealing with Mean Stress Effect in Fatigue Life Prediction for Aeroengine Disks

Mao

et al. 2018

Mathematical Problems in Engineering

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Mean stress effect plays an important role in fatigue life prediction, and it is discovered that maximum stress has nonnegligible influence on mean stress effect. Therefore, a modified Walker model is proposed to account for mean stress effect on fatigue life of aeroengine disks, which contains the influence of stress ratio and maximum stress on mean stress effect. Eight sets of fatigue data for standard smooth bars from six kinds of materials commonly used in aeroengine disks as well as two sets of experimental data from simulated specimens of turbine disks were employed to investigate the prediction capability of the proposed model against other candidate mean stress relationships. It is found that Goodman model generates most conservative results, while Morrow model overestimates fatigue life for most cases. SWT model yields similar results to Walker model but with less accuracy. The results of the modified Walker model turn out to be superior to those of any other candidate models for all cases examined, especially for large mean stress ones. Thus, the modified Walker model can be an effective method to predict fatigue lives of aeroengine disks influenced by mean stresses.

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The Resistance of Metals to Cyclic Deformation

Cited by 126 publications

References 10 publications

Mean stress effects in stress‐life fatigue and the Walker equation

Mean stress effects in stress‐life fatigue and the Walker equation

Improvement of Fatigue Life of 1080 Steel by Thermomechanical Processing

A Modified Walker Model Dealing with Mean Stress Effect in Fatigue Life Prediction for Aeroengine Disks

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