Vibration fatigue

About: Vibration fatigue is a research topic. Over the lifetime, 3460 publications have been published within this topic receiving 46297 citations.

An Ultra-High Frequency Vibration-Based Fatigue Test and Its Comparative Study of a Titanium Alloy in the VHCF Regime

Abstract: This paper proposes an ultra-high frequency (UHF) fatigue test of a titanium alloy TA11 based on electrodynamic shaker in order to develop a feasible testing method in the VHCF regime. Firstly, a type of UHF fatigue specimen is designed to make its actual testing frequency reach as high as 1756 Hz. Then the influences of the loading frequency and loading types on the testing results are considered separately, and a series of comparative fatigue tests are hence conducted. The results show the testing data from the present UHF fatigue specimen agree well with those from the conventional vibration fatigue specimen with the loading frequency of 240 Hz. Furthermore, the present UHF testing data show good consistency with those from the axial-loading fatigue and rotating bending fatigue tests. But the obtained fatigue life from ultrasonic fatigue test with the loading frequency of 20 kHz is significantly higher than all other fatigue test results. Thus the proposed ultra-high frequency vibration-based fatigue test shows a balance of high efficiency and similarity with the conventional testing results.

Fatigue Life Estimation under Cyclic Loading Including Out-of-Parallelism of the Characteristics

Abstract: The paper presents an algorithm of fatigue life determination for materials with no parallel fatigue characteristics under pure bending and pure torsion. The presented model uses the iteration method, and the applied fatigue criterion is function of the ratio of normal and shear stresses coming from bending and torsion, respectively. Three materials were applied for analysis: CuZn40Pb2 brass, 30CrNiMo8 medium-alloy steel and 35NCD16 high-alloy steel.

A robust stress analysis method for fatigue life prediction of welded structures

Abstract: In the case of structural weldments, the procedure for estimating fatigue life requires information concerning geometry of the object, loads, and material. Detailed knowledge of stress fields in the critical regions of weldments is used to determine the fatigue life. The main theme of the research discussed in this paper is to provide details of the methodology which has been developed to determine the peak stress and associated non-linear through-thickness stress distribution at the critical weld toe crack plane by using only the geometry-dependent stress concentration factors along with appropriate unique reference stress calculated in an efficient manner, e.g., without modeling geometrical weld toe details. The peak stress at the weld toe can be subsequently used for estimating the fatigue crack initiation life. The non-linear through-thickness stress distribution and the weight function method can be used for the determination of stress intensity factors and for the analysis of subsequent fatigue crack growth. Accurate peak stress estimation requires 3D fine mesh finite element (FE) models, accounting for the micro-geometrical features, such as the weld toe angle and weld toe radius. Such models are computationally expensive and therefore impractical. On the other hand, stresses at the sharp weld corners obtained from 3D coarse FE meshes are inaccurate and cannot be used directly for fatigue life estimations. This paper describes a robust, sufficiently accurate, and efficient stress analysis method for fatigue life estimation of welded structures based on 3D FE coarse mesh models. Another objective is to establish a methodology which is capable of accounting for the actual variability of stress concentration factors at welds, welding defects such as misalignment, and incomplete penetration resulting from the manufacturing process. The methodology described in the paper has been validated by analyzing several weldments of varying geometrical and load configurations. The proposed methodology not only reduces conservative fatigue design of welded structures but also leads to significant savings concerning modeling and computation efforts.

Reliability of metal components in fatigue: a simple algorithm for the exact solution

Abstract: — An efficient and accurate method for computing the fatigue-life distribution of metal structures is presented. The problem is governed by the basic equations of the Coffin-Manson-Neuber local-strain fatigue theory for notched components. The coefficients of fatigue strength and fatigue ductility, the fatigue notch factor as well as the nominal-stress amplitude may be random variables with an arbitrary joint distribution. In order to arrive at a direct solution for the fatigue-life distribution, hence an assessment of the reliability of a component, a collocation method has been developed which gives the total-strain amplitude as an explicit function of the stress amplitude and the fatigue notch factor. This explicit equation has very close conformity to the corresponding, true, implicit equation. The fatigue-life distribution is finally expressed in a multiple-integral closed form. A simple algorithm termed the “complete-probability fast integration” (CPFI) is developed which gives the exact solution, to any desired accuracy, for the entire ranges of fatigue-life and reliability. CPFI is superior when compared to the results and procedures of the approximate methods currently employed.