A Novel Multiaxial Strain-Based Criterion Considering Additional Cyclic Hardening

The present paper is dedicated to the theoretical evaluation of a loading feature, that may have a significant influence on fatigue phenomenon: non-proportionality. As a matter of fact, considerable interactions between dislocations, leading to the formation of dislocation cells, cause additional cyclic hardening of material. Such a phenomenon is experimentally observed for materials sensitive to non-proportionality. In such a context, the present paper is aimed to propose a novel multiaxial strain-based criterion, the refined equivalent deformation (RED) criterion, which allows to take into account, in fatigue life estimation, both strain amplitude and additional cyclic hardening. The accuracy of the novel criterion is evaluated by considering experimental tests, performed on Ti-6Al-4V specimens, subjected to multiaxial LCF loading.

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An Investigation of Cyclic Transient Behavior and Implications on Fatigue Life Estimates

Journal of Engineering Materials and Technology ◽

10.1115/1.2805989 ◽

1997 ◽

Vol 119 (2) ◽

pp. 161-170 ◽

Cited By ~ 35

Author(s):

Yanyao Jiang ◽

Peter Kurath

Keyword(s):

Stainless Steel ◽

Fatigue Life ◽

Cyclic Hardening ◽

Transient Behavior ◽

Fatigue Tests ◽

304 Stainless Steel ◽

Deformation History ◽

Life Estimation ◽

Fatigue Life Estimation ◽

Track Deformation

Current research focuses on proportional cyclic hardening and non-Massing behaviors. The interaction of these two hardenings can result in the traditionally observed overall softening, hardening or mixed behavior exhibited for fully reversed strain controlled fatigue tests. Proportional experiments were conducted with five materials, 304 stainless steel, normalized 1070 and 1045 steels, and 7075-T6 and 6061-T6 aluminum alloys. All the materials display similar trends, but the 304 stainless steel shows the most pronounced transient behavior and will be discussed in detail. Existing algorithms for this behavior are evaluated in light of the recent experiments, and refinements to the Armstrong-Frederick class of incremental plasticity models are proposed. Modifications implemented are more extensive than the traditional variation of yield stress, and a traditional strain based memory surface is utilized to track deformation history. Implications of the deformation characteristics with regard to fatigue life estimation, especially variable amplitude loading, will be examined. The high-low step loading is utilized to illustrate the effect of transient deformation on fatigue life estimation procedures, and their relationship to the observed and modeled deformation.

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The Fictitious Radius as a Tool for Fatigue Life Estimation of Notched Elements

Materials Science Forum ◽

10.4028/www.scientific.net/msf.726.27 ◽

2012 ◽

Vol 726 ◽

pp. 27-32 ◽

Cited By ~ 4

Author(s):

Grzegorz Robak ◽

Marcel Szymaniec ◽

Tadeusz Łagoda

Keyword(s):

Fatigue Life ◽

Notch Root ◽

Experimental Tests ◽

Life Estimation ◽

Fatigue Life Estimation

In this paper, the fictitious radius - according to Neuber’s method for determination of stresses at the notch root was used. Next, the fatigue lives of elements of the ring notches were calculated, and then compared with results of experimental tests of S235JR steel samples. However, the obtained fatigue lives did not bring satisfactory results. It has been demonstrated that the fictitious radius strongly depends on the expected fatigue life

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Fatigue Life Estimation in Notched Geometries

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2013-98104 ◽

2013 ◽

Author(s):

Sebastian Cravero ◽

Hugo Ernst

Keyword(s):

Fatigue Life ◽

Experimental Tests ◽

Crack Size ◽

Initial Crack ◽

Life Estimation ◽

Threaded Connections ◽

Fatigue Life Estimation ◽

Initiation Stage ◽

Study Techniques ◽

Number Of Cycles

The fatigue failure in components is divided in two stages: an initiation stage that defines the number of cycles that it takes for a crack to appear in the material and a second stage that estimates the number of cycles where the crack grows until it becomes unstable. Usual fatigue life estimation procedures (in crack free components) only consider the initiation stage and assume that the crack propagation period is relatively small compared with the total life. However, in the case of severely notched geometries like threaded connections, the propagation stage can be an important part of the component fatigue life and must be evaluated. A fundamental issue in the calculation of initiation plus propagation fatigue life is the definition of the initial crack size after the initiation stage. In the present study techniques for crack initiation and crack growth are described. Also the procedure to combine the two techniques and define an initial crack size is presented. The study is based on previous work of C. Navarro, et al. [1]. Additionally, validation against experimental tests on notched specimens is provided.

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Fatigue Life Estimation of the Tail Boom and Vertical Stabilizer of MI-24 Helicopter

Fatigue of Aircraft Structures ◽

10.2478/v10164-010-0028-4 ◽

2010 ◽

Vol 2010 (2) ◽

Author(s):

Piotr Reymer ◽

Andrzej Leski

Keyword(s):

Fatigue Life ◽

Life Estimation ◽

Fatigue Life Estimation

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Load Spectrum Compiling and Fatigue Life Estimation of the Automobile Wheel Hub

Recent Patents on Mechanical Engineering ◽

10.2174/2212797613999201231200939 ◽

2020 ◽

Vol 13 ◽

Author(s):

Xintian Liu ◽

Yang Qu ◽

Xiaobing Yang ◽

Yongfeng Shen

Keyword(s):

Fatigue Life ◽

High Speed ◽

Two Dimensional ◽

Load Spectrum ◽

One Dimensional ◽

Life Estimation ◽

Load Spectra ◽

Fatigue Life Estimation ◽

Program Load Spectrum ◽

Program Load

Background:: In the process of high-speed driving, the wheel hub is constantly subjected to the impact load from the ground. Therefore, it is important to estimate the fatigue life of the hub in the design and production process. Objective:: This paper introduces a method to study the fatigue life of car hub based on the road load collected from test site. Methods:: Based on interval analysis, the distribution characteristics of load spectrum are analyzed. The fatigue life estimation of one - dimensional and two - dimensional load spectra is compared by compiling load spectra. Results:: According to the S-N curve cluster and the one-dimensional program load spectrum, the estimated range fatigue life of the hub is 397,100 km to 529,700 km. For unsymmetrical cyclic loading, each level means and amplitude of load were obtained through the Goodman fatigue empirical formula, and then according to S-N curve clusters in the upper and lower curves and two-dimensional program load spectrum, estimates the fatigue life of wheel hub of the interval is 329900 km to 435200 km, than one-dimensional load spectrum fatigue life was reduced by 16.9% - 17.8%. Conclusion:: This paper lays a foundation for the prediction of fatigue life and the bench test of fatigue durability of auto parts subjected to complex and variable random loads. At the same time, the research method can also be used to estimate the fatigue life of other bearing parts or high-speed moving parts and assemblies.

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