Fatigue Life Prediction Model Research Articles

Weft direction tension-tension fatigue responses of layer-to-layer 3D angle-interlock woven composites at room and elevated temperatures

Elevated fatigue behaviors of resin matrix composites are considerable key to the application of aeroengine that requires fatigue resistance at elevated temperature. However, undeniably, very few studies are focused on this issue, thereby resulting in limitation applications of resin matrix composites in aeroengine components, i.e. blades and case. In this work, the fatigue responses of layer-to-layer 3D angle-interlock woven composites (2.5DWC) were experimentally and numerically studied at room and elevated temperatures. Experimental results show that the weft direction fatigue lives at 20 °C and 180 °C experienced a relatively short cycle (less than 104 cycles) prior to the failure. But, once the stress level declined to a threshold value (dropped by 1–2%), the fatigue limitation would be activated, regardless of temperature. Moreover, the residual strength at 20 °C or 180 °C was reinforced compared to the static strength. Considering the fatigue data and fracture morphology, probable damage mechanisms corresponding to temperature-dependent weft direction fatigue behaviors of 2.5DWC were proposed. A temperature-dependent fatigue life prediction model of 2.5DWC was proposed, based on which the weft direction fatigue lives, damage propagation processes and residual stiffnesses of 2.5DWC at 20 °C and 180 °C were predicted.

Evaluation of interlayer stability in asphalt pavements based on shear fatigue property

Interlayer fatigue resistance is an important property to ensure the durability and stability of asphalt pavements. Shear fatigue damage is one of the main failure modes of asphalt pavements, but the existing design methods involve little in the way of shear fatigue property. In this work, the fatigue life of five different interlayer bonding conditions was studied by a direct shear fatigue test. The fatigue test data was processed by the Weibull distribution function. The laboratory prediction model of interlayer fatigue life was obtained with shear stress (τ) and interface stiffness (Kmin) as variables. A decay model of interlayer bonding property was proposed based on the fatigue life model. The axle-load conversion formula was obtained based on the laboratory prediction and decay models. The laboratory fatigue life prediction model was revised, and the final prediction model was obtained. Finally, a method to evaluate interlayer stability was proposed based on the shear fatigue model and conversion method of axle-load. The study provides a theoretical basis for the interlayer design and stability evaluation of asphalt pavement.

Corrosion-Fatigue Analysis of High-Strength Steel Wire by Experiment and the Numerical Simulation

The paper takes the corrosion fatigue damage of cable or sling in the actual bridge as a starting point. The high-strength steel wire is chosen as the basic component to study the corrosion fatigue failure mode. The service life prediction model is put forward, which provides a basis for future research. In this paper, the S-N curves of the steel wire with the different corrosion degrees are given through fatigue tests of six groups of steel wire under different corrosion conditions. The results show that the higher the corrosion degree, the steeper the S-N curve, and the fatigue life considering corrosion are much lower than that without considering corrosion. Finally, a fatigue life prediction model considering the coupling effect of corrosion fatigue is proposed and embedded into Abaqus v6.14 (Dassault, Paris, French). The calculation results show that the fatigue model considering the corrosion can predict the service life to some extent.

A new multiaxial fatigue life prediction model considering additional hardening effect

The established linear fatigue life prediction model based on the Miner rule has been widely applied to fatigue life prediction under constant amplitude uniaxial and multiaxial loading. Considering the physical significance of crack formation and propagation, a multiaxial equivalent linear fatigue life prediction model is put forward based on Miner rule and critical plane method under constant amplitude loading. The essence of this approach is that the equivalent strain, which consists of the shear strain and normal strain on the critical plane, replaces the relevant parameter of uniaxial nonlinear fatigue damage model. The principal axes of stress/strain rotate under non-proportional loading. Meanwhile, the microstructure of material and slip systems change, which lead to additional hardening effect. The ratio of cyclic yield stress to static yield stress is used to represent the cyclic hardening capacity of material, and the influence of phase difference and loading condition on the non-proportional hardening effect is considered. The multiaxial fatigue life is predicted using equivalent stain approach, maximum shear stain amplitude model, CXH model, and equivalent multiaxial liner model under proportional and/or non-proportional loading. The smooth and notched fatigue specimens of four kinds of materials (Q235B steel, titanium alloy TC4, Haynes 188, and Mod.9Cr-1Mo steel) are used in the multiaxial fatigue experiments to verify the proposed model. The predicted results of these materials are compared with the test results, and the results show that these four models can achieve good effect under proportional loading, but the proposed model performs better than the other three models under non-proportional loading. Meanwhile, it also verifies that the proposed enhancement factor can reflect the influence of phase difference and material properties on additional hardening.

Review on fatigue life prediction models of welded joint

Fatigue assessment of welded joint is still far from being completely solved now, since many influencing factors coexist and some important ones should be considered in the developed life prediction models reasonably. Thus, such influencing factors of welded joint fatigue are firstly summarized in this work; and then, the existing life prediction models are reviewed from two aspects, i.e., uniaxial and multiaxial ones; finally, significant conclusions of existing experimental and theoretical researches and some suggestions on improving the fatigue assessment of welded joints, especially for the low-cycle fatigue with the occurrence of ratchetting, are provided.

Damage and fatigue life prediction of short fiber reinforced composites submitted to variable temperature loading: Application to Sheet Molding Compound composites

The majority of fatigue life prediction models which have been proposed for the Short Fiber Reinforced Composite (SFRC) materials have been developed for constant temperature. However, in real situations, SFRC structures are subjected to variable temperature. This study focus on the response of SFRC composites subjected to different sequences (or blocks) under variable temperature conditions. Experientially, this kind of study requires a lot of investment from the point of view of cost and time. In this paper, the results coming from modelling the fatigue life and residual stiffness of short fiber reinforced composites subjected to thermomechanical loadings are reported. In fact, we propose to use a hybrid micromechanical-phenomenological model to quantify the evolution of the local damage rate during each loading block. Indeed, damage accumulation is calculated and cumulated step by step through the calculation of the evolution of a local damage ratio which describes the evolution of micro-cracks density until failure. Life prediction for specimens submitted to a variable temperature loading found to give acceptable results compared to experiments.

Fatigue behavior of in-situ TiB2/7050Al metal matrix composites: Fracture mechanisms and fatigue life modeling after milling

Due to the superior properties such as low density, improved strength and wear resistance, the in-situ TiB2/7050Al MMCs have become a series of promising aeronautical materials. However, researches of manufacturing performance and fatigue behavior on machined in-situ TiB2/7050 Al MMCs have not been widely carried out. In this study, the fatigue behavior of machined in-situ TiB2/7050Al MMCs specimens such as fatigue mechanism, stress concentration, fatigue life and life modeling were deeply investigated. It was found that the fatigue life ranges from 1.0 × 105 to 4.0 × 106, which turned to be obvious high-cycle fatigue life. With surface roughness increased, the fatigue life decreased sharply. It would be highly significant to reduce the machined surface roughness below 1.0 μm for higher fatigue life. The fracture mechanisms of cutting in-situ TiB2/7050Al MMCs was found to be brittle fracture due to the existence of fine particles. Besides, a stress concentration model and fatigue life prediction model were established. With validation, the relative errors between prediction model and experiment were smaller than 18% indicating that the proposed fatigue life prediction model of machined in-situ TiB2/7050Al MMCs was of good reliability and accuracy.

Fatigue Life Simulation and Analysis of Aluminum Alloy Sheet Self-piercing Riveting

The fatigue life prediction model of self-piecing riveting components of aluminum alloy is established and the effects of roughness and residual stress on fatigue life of self-piercing riveting components is analyzed by the model. Finite element software ABAQUS and fatigue analysis software FE-SAFE are used to study the effects of roughness and residual stress on the fatigue life of self-piecing riveting components through finite element simulation and mathematical statistics multivariate orthogonal regression experiment. The quantitative relations between fatigue life and three variables (roughness, residual stress and maximum stress) are fitted, and the variation trend of fatigue life with roughness and residual stress is obtained. The order of influence of roughness, residual stress, maximum stress and two interactions on fatigue life is as follows: residual stress, interaction between roughness and residual stress, roughness. When the maximum stress is fixed, the fatigue life decreases with the increase of roughness with a certain residual stress, and the fatigue life decreases with the increase of roughness with a certain residual stress. The average error between the fatigue experiment results and the simulation results is 9.74%, which proves that the simulation results are reliable.

Fatigue Life Prediction of GLARE Composites Using Regression Tree Ensemble‐Based Machine Learning Model

AbstractWith the advancement of machine learning in leading technologies, it is perceived that machine learning is a new and effective alternative for the classic fatigue life prediction. This paper provides a regression tree ensemble‐based machine learning approach to predict the fatigue life of GLARE composites. In the model, mechanical, geometrical properties and fatigue loading stresses are selected as the training parameters (so‐called features), and the GLARE fatigue life is predicted as the output of the model. Experimental data of a total of 98 pieces of GLARE specimens with nine different layups are used for the training and validation of the machine learning model. Results show that the model can provide good fatigue life prediction accuracy and model stability. The most correlated, either positively or negatively, parameters to the fatigue life span are the stress developed in the aluminum layer, the maximum cyclic stress, alternating stress, and mean fatigue stress.

Bending Fatigue Life Prediction of Spur Gear in Axial Misalignment Condition

Misalignment between pinions to wheel gears induces bending stresses continued influences the fatigue life of the spur gear system. Lack of research projected to the issues causes uncertain in their useful lifetime estimation. In this paper, the bending fatigue life of the spur gear in axial misalignments condition was predicted. A three teeth FEM model of spur gear with the same geometrical profiles was constructed according to ISO 6336-1:2006. The gear was subjected with five misalignment from 0.1mm to 0. 5mm at different torque loadings from 50Nm to 300 Nm. Exerted with quasi-static approach; the stress variant was analysed to stress life model as well as the damage accumulation model for fatigue life prediction in ANSYS V19. Results showed that the application of axial misalignment had a small impact significantly reduce the life of the gear, in percentage difference between 0.1 - 2%. This suggested that the bending fatigue life did not reflect to the existence of axial misalignments as the effect is very small that it is possible to be neglected.

Experiment and modelling on the effect of microstructural morphology on fatigue life of a Ni-based superalloy

A directionally solidified Ni-based superalloy was pre-treated under high temperature with/without the applied stress to obtain different microstructural morphology. Then, strain-controlled low cycle fatigue experiments were carried out under 850°C with a 0 strain ratio to measure the reduction in the fatigue resistance. The scanning electron microscopy (SEM) was employed to characterize the microstructures of the alloy with different treatments. The micro-deformation and dislocation movement were investigated via transmission electron microscopy (TEM). The results show that both coarsening and rafting morphology have negative effects on the fatigue properties, which is closely related to the deformation mechanism of the alloys with different γ' morphology. The coarsening morphology decreases the shear resistance of the γ' precipitates, resulting in shearing of γ' particles. More plastic deformation introduces during the cyclic process, leading in the reduction of fatigue life. On the other hand, the wide γ channel promoted the piling up and movement of dislocations in the matrix, also resulting in reduction of plastic deformation resistance and lifespan. Finally, a fatigue life prediction model was proposed based on the continuum damage mechanics (CDM) by introducing the variation of matrix channels’ width, showing a good competency compared with the experimental results.

Influence of flexural loading and chloride exposure on the fatigue behavior of high-performance lightweight engineered cementitious composites

The flexural fatigue behavior of high-performance lightweight engineered cementitious composites (HPLW-ECC) with tensile strength of 7.16 MPa and tensile strain capacity of 8.91% was investigated. The flexural repetitive loading demonstrated a pronounced influence on the fiber bridging capacity of HPLW-ECC. In contrast, the multiple cracking characteristics of HPLW-ECC under chloride exposure were maintained though its fatigue life decreased. The low-density HPLW-ECC exhibited high resistance to chloride penetration, and the fiber bridging capacity remained almost intact. Moreover, the flexural fatigue performance of HPLW-ECC possessing higher strength was comparable to that of conventional lightweight ECC. A fatigue life prediction model was proposed, and the model’s failure probability was discussed based on the probabilistic reliability analyses.

Life prediction for rate-dependent low-cycle fatigue of PA6 polymer considering ratchetting: Semi-empirical model and neural network based approach

Based on the experimental results in [1,2], a semi-empirical low-cycle fatigue life prediction model is constructed for a polyamide-6 (PA6) polymer, in which the rate dependence of fatigue life and the effect of ratchetting strain on the life are considered. Since the fatigue damage in PA6 is not only loading-cycle-dependent but also time-dependent, a function to describe the complicate effect of stress rate on the fatigue life is obtained. In the proposed model, the detrimental effect of ratchetting strain on the fatigue life is characterized by introducing a function of mean stress. Comparison of the predicted and experimental results shows that the proposed model presents a good prediction. Furthermore, the neural network based method is also used to correlate the low-cycle fatigue data of PA6. The results show that the established neural network based approach achieves a better prediction to the fatigue life of PA6 with the occurrence of ratchetting than that by the proposed semi-empirical model, which demonstrates a possibility to apply the neural network based machine learning method to deal with the fatigue of polymer.

A Multi-Axial Fatigue Limit Prediction Equation for Metallic Materials

Abstract Based on the multi-axial fatigue life prediction model presented recently by the authors, in this note, a fatigue limit prediction equation for metallic materials under multi-axial loading is proposed. In the multi-axial fatigue life prediction model, the wildly used von Mises equivalent stress is taken as an equivalent fatigue mechanical quantity, and the multi-axial fatigue life prediction equation has the invariance of mathematical equation form. By applying the multi-axial fatigue life prediction equation without mean stress effect to fatigue limit case, a simple fatigue limit prediction equation can be obtained. By using a large number of experimental data of metallic materials reported in literature, it has been proven that the fatigue limit prediction equation is not only simple in computation but also high in accuracy.

Cyclic plastic zone-based notch analysis and damage evolution model for fatigue life prediction of metals

Fatigue strength analysis of critical components plays a vital role for ensuring structural integrity and operational reliability of major equipment. In notched components, the concept of cyclic plastic zone (CPZ) is commonly utilized for fatigue cracking analysis, in which the CPZ size normally relates to the material strength. In particular, materials with higher yield stress have shown smaller CPZ size and vice versa. According to this, a new approach for determining closed-form stress at the notch tip is proposed by considering the size of cyclic plastic zone, which can be used for the notch tip stress evaluation along the load direction under cyclic loadings. By implementing FE analysis, experimental data of 304 stainless steel, 40Cr steel and Ti-6Al-4V alloy are utilized for model validation and comparison. Results show that the scope of damaged CPZ alters the notch tip stress under fatigue loadings, and the proposed model yields better correlation of fatigue life predictions with experimental results of the three materials than other two models.

A low-cycle fatigue life prediction model for Alloy625 arc wire welding repairs of gas turbine blades

Wire arc deposition is an interesting manufacturing technique for producing metallic parts made of Ni-based alloys, for cladding and for repairs in turbine components. This technique, when compared to power bed fusion processes, allows to obtain parts with a limited porosity. In this paper, a wide experimental campaign on the Alloy625 wire arc deposited alloy was carried out to characterize its mechanical behavior under low cycle fatigue conditions. Specific specimen geometries were implemented to reproduce the welded Alloy625 mechanical behavior as solid material or thick repairs. A crack propagation model based on the effective value of the J-integral range is proposed to simulate the propagation of a potential crack originated from a welding defect. The work aims to provide a robust methodology to approach the damage tolerance design of solid and repaired parts obtained by wire arc deposition.

Corrosion fatigue failure analysis and service life prediction of high strength steel wire

In this paper, corrosion fatigue failure of high-strength steel wire was studied based on the actual cable or sling in the bridge, and the service life prediction formula considering the corrosion effect was put forward, which provides a force basis for future research. Firstly, six groups of steel wires with different corrosion degrees were analyzed by a 3D scanner, and the corrosion characteristics of different specimens were given. Secondly, S-N curves of different corrosion degrees and S-N-φ surface were given by fatigue tests of six groups of steel wires with different corrosion degrees. The results show that the S-N curve becomes steeper with the increase of steel wire corrosion. Fatigue life considering the corrosion is much lower than that without considering corrosion. Finally, a fatigue life prediction model considering the corrosion fatigue coupling effect was proposed. The calculation results show that the fatigue life prediction model considering the corrosion fatigue coupling effect can reflect the effect of the corrosion fatigue coupling effect to some extent.

Probabilistic fatigue resistance model for steel welded details under variable amplitude loading – Inference and uncertainty estimation

This paper presents a probabilistic fatigue life prediction model for welded details subjected to variable amplitude random loading, using the nominal stress approach. The proposed model makes use of CA S-N curves in combination with the relative damage rule which allows to globally account for load interaction effects, and the damage limit concept that permits the estimation of the damage for the stress ranges lower than the fatigue limit and is based on linear elastic fracture mechanics. Epistemic (sampling) and aleatory (statistical) uncertainties are estimated in a statistical framework, making the model applicable for structural reliability analyses.

Investigation on fatigue performance of adhesively bonded butt-joints and multiaxial life estimation using stress-based failure models

Uniaxial and multiaxial low-cycle fatigue experiments were conducted on the automobile sealant adhesive bonding hollow cylindrical butt-joints under stress-controlled mode, and the effects of equivalent stress amplitude, equivalent mean stress and loading frequency on the fatigue life of specimens were analyzed. The experimental results showed that the fatigue life of uniaxial tensile cycle was shorter than that one of uniaxial torsion cycle. The fatigue life of the automobile sealant adhesive bonding butt-joints decreased with the increase of equivalent stress amplitude, mean stress, loading frequency. The fatigue life of the non-proportional loading path was shorter than that of the proportional loading path. In addition, a modified stress-based fatigue life prediction model was proposed that collectively considered the effect of loading path, equivalent stress amplitude, equivalent mean stress and loading frequency on the multiaxial fatigue life. The comparisons of the predicted results and the experiment life indicated that the modified fatigue life prediction model had good prediction ability for the multiaxial fatigue life of the sealant adhesive bonding butt-joints.

Predicting Fatigue Life for Finite Line Contact under Starved Elastohydrodynamic Lubrication Condition

Surface contact fatigue is the main failure mode in many mechanical components, such as gears, bearings, and cam-followers. A fatigue life prediction model is proposed for finite line contact under starved thermal elastohydrodynamic lubrication (TEHL) condition in this paper. Then, the effects of inlet oil-supply thickness, slide-to-roll ratio (SRR), and operating conditions on the lubrication performance and fatigue life are investigated. The results show that the lubrication characteristics and fatigue life of finite line contact are obviously different from those of fully flooded situation by introducing the starved lubrication condition. For example, the severe starved conditions lead to a significant increase in friction coefficient and decreased fatigue life. The variation of SRR has an important influence on the fatigue life. With the increase of SRR, the fatigue life decreases firstly and then increases. The stress concentration occurs near the surface when speed is low. In addition, under the low-speed situation, rotation speed variation has little effect on the fatigue life.