A vast amount of research has been carried out towards the goal of quantifying changes related to the fatigue damaging process in materials throughout the fatigue life. However, no recommended practice has been developed for the experimental measurement of fatigue damage before a macroscopic crack has been initiated. Therefore, this paper reviews the existing fatigue damage detection and measurement

The paper, after analysis of a large experimental data base, shows that, depending on the material, the effect of defect on the fatigue limit should be described through 5 major parameters: Size, Type, Position, Morphology and Loading. A fatigue criterion describing the effect of the defect through the local stress gradient is discussed and the identification procedure shows that each of the 5 major

The fatigue crack growth behaviors of two fuel membranes are investigated at different temperatures. Fatigue crack growth rate increases with temperature, and Nafion XL membrane is more sensitive to temperature. An Arrhenius-type expression for fatigue crack growth rate is proposed and good prediction results are obtained. For Nafion XL composite membrane, fatigue crack grows by forming micropores

In the present paper, a criterion for fatigue assessment of high strength steels is proposed, where the influence of non-metallic inclusions on fatigue life is taken into account. To such an aim, the Carpinteri et al. criterion is used in conjunction with the area-parameter model by Murakami and Yanase. An experimental campaign available in the literature is analysed to evaluate the criterion accuracy

This study proposes a Bayesian inference-based decision framework to quantify the physical uncertainty based on fatigue life tests on maraging steel according to post-processing treatments and build orientations. Uncertainty quantification of fatigue life models is performed to determine the most suitable models for the metal additive manufacturing process by employing Bayesian inference. To select

The use of fracture mechanics based methodologies to assess the influence of defects on the high cycle fatigue resistance of mechanical components has become increasingly important for industrial applications and design. This presentation introduces the most commonly used fracture mechanics methods, emphasizing the assumptions on which they are based and analyzing their potential in predicting the

Additive manufacturing (AM) of metallic parts is a relatively new manufacturing procedure. Many industry sectors, such as the aerospace or automotive sectors, have started to apply this technology to produce some elements, thus reducing costs and weight. Several metallic alloys have been employed for AM. Due to the high strength-to-density ratio, Ti6Al4V alloy is probably the alloy most used for AM

High Frequency Mechanical Impact (HFMI) treatment offers a great opportunity to enhance the lightweight potential of welded structures using high strength steel materials. Focusing on the IIW Recommendations for the HFMI Treatment, a fatigue assessment based on the nominal, structural as well as notch stress approach is considered. Due to its sound applicability and proper assessment of the fatigue

To date the term “Fatigue Damage” has had an ambiguous usage in the fatigue community. This paper explains the reason for the poor predictive results of existing fatigue damage rules, such as Miner’s rule, through precise observation of small crack growth during multiple step loadings. For the exact evaluation of fatigue damage it is crucially important to attend to the phenomenon of the continuous

Hole cold expansion is an effective anti-fatigue manufacturing technology, which is widely used in hole strengthening of aviation components. In this paper, a novel small-deep hole (with the diameter less than 2 mm and the depth greater than 10 mm) cold expansion process, called the multi-spherical bump rotating cold expansion process (MBR-CEP), was proposed and verified by experiments on the Inconel

Fatigue crack growth in composite, single lap bonded joints is analysed by back face distributed strain sensing, using optical backscatter reflectometry. Crack growth is inferred from the back-face strain profile measured with high spatial resolution along optical fibres bonded on the joints. The indications about the position of the crack front are compared with micro computed tomography scans conducted

The probability of fracture (POF) assessment of complex cracked structures is a difficult task in the reliability assessment of engineering structures. Due to the complexity of structure, balancing efficiency and accuracy is the top concern in POF calculation. In this study, a novel probabilistic solution method called AKNN-MCS (Active learning-based K-Nearest Neighbors-Monte Carlo Simulation) is proposed

In this paper, the sub-scaled dovetail joints with the material of DD6-FGH96 are studied by experimental and numerical methods. To monitor the crack growth, the silicon-rubber replica method and telephoto microscope are used for testing at room temperature 25 °C and high temperature 600 °C, respectively. The testing results show significant differences between high and room temperature. Furthermore

This study investigates the characteristics of Fiber Braggs Grating (FBG) sensors with respect to their feasibility for use in additive manufactured materials under fatigue loading. This was done through tensile fatigue testing of both standard Acrylonitrile butadiene styrene (ABS) specimens and ABS specimens containing FBG sensors. These sensors were incorporated into the material using two different

AA7050-T7451 aluminum alloy is one of the most used material in aeronautical applications due to its high strength/density ratio and good fatigue resistance. More recently the AA2050-T84 alloy was introduced due to its reduced density and comparable static mechanical properties. However, fatigue crack propagation properties in corrosive environments are yet to be documented. In this paper fatigue crack

In this paper, a dual-scale modelling approach is developed to investigate creep-fatigue behavior and predict crack initiation life for holed structures under multi-axial stress state. The macro-scale simulation supplies local deformation histories to the dual-scale simulation as boundary conditions. In the dual-scale simulation process, the micro-mechanical behavior and damage evolution are described

The loads for bogie frame fatigue damage prediction under service environment has become a critical priority. In this study, the completeness of the measured loads was verified and bogie loads were classified into quasi-static and dynamic regions. Bogie modal vibration and rail corrugation were studied to adjust the loads. The predicted fatigue damage was closer to the actual damage and covered the

We present a new theoretical and numerical phase field-based formulation for predicting hydrogen-assisted fatigue. The coupled deformation-diffusion-damage model presented enables predicting fatigue crack nucleation and growth for arbitrary loading patterns and specimen geometries. The role of hydrogen in increasing fatigue crack growth rates and decreasing the number of cycles to failure is investigated

An empirical bi-parametric model based on the Vickers hardness HV and a proper microstructural length parameter, l, was proposed to estimate the fully reversed threshold-Stress Intensity Factor for long cracks of wrought and additively manufactured (AM) alloys. In this paper, the model has been extended to positive load ratios (R≅0 and ≅0.5). Afterwards, experimental results, generated from testing

A probabilistic low-cycle fatigue (LCF) model, ProbLCF-VA, is proposed in this work to describe the scatter of the LCF crack initiation life for homogeneous materials subjected to variable or random load cycles. This model can be implemented either to estimate the probabilistic cumulative damage for a given load history consisting of variable cyclic loads, or to predict the probabilistic LCF crack

Traditional design approaches using safety factors are intended to account for uncertainties due to the lack of available data in engineering practice. However, the direct use of safety factor to represent uncertainties often causes conservative results, and it is not intuitive to describe the reliability of these structures through safety factor. To deal with the issue, this research revisits the

Fatigue crack propagation behavior of IN718 superalloy aged with or without stress was investigated. The alloy aged with stress exhibited a higher fatigue crack growth rate and a lower fatigue threshold compared to that without stress. Both the restricted dislocation planar slip and the decreased difference in orientation of the activated slip system between adjacent grains were promoted by coarse

In this paper, the fatigue behavior of railway wheel specimens subjected to cyclic loading have been investigated via experimental tests and numerical analysis. The material behaviour of the wheel specimen has been modelled by means of the Ramberg‐Osgood equation. The non‐linear Kujawski‐Ellyin (KE) model has been adopted for the fatigue crack propagation under small‐scale yielding (SSY) conditions

Two-level step multiaxial fatigue tests were conducted to investigate the crack growth behavior and damage accumulation of 30CrMnSiA steel. When the first load step (50% of the fatigue failure life) is completed, main cracks of specimens have entered the stage Ⅱ propagation. The cracks gradually turn direction to propagate along the maximum normal stress planes of load step 2 under the second load

In the present study, fatigue damage evolution of Inconel 617 at 600 °C and 700 °C was investigated by using an in situ scanning electron microscope (SEM) fatigue test. The fatigue crack initiation and propagation processes were directly observed and recorded online. Fractography and microstructure analyses were performed to further reveal the mechanism of high-temperature failure. Experimental results

The aim of this work is to study how well fatigue life predictions, based on Arcan tests results, apply to real joint with a complex geometry, used as a structural component in industrial vehicles. Using a stress-life approach, a master stress-life curve for fatigue was constructed. By utilizing the master curve, fatigue life predictions were made for the joints and compared with the welded assembly

Accurate fatigue lifetime prediction is a central element in many industries. Often, a damage tolerant approach is used to ensure that some given imperfections are safe. In this context, these lifetime predictions are frequently made using simplified crack geometries leading to costly conservatism. In particular for a closed crack front, a circular or elliptical crack enclosing the real defect is generally

High-cycle fatigue tests were performed on differently deep rolled conditions of the equiatomic high-entropy alloy (HEA) CoCrFeMnNi. Twinning in the near-surface layer of specimens deep rolled at cryogenic temperature is revealed by electron-backscatter diffraction. As internal failure mode and similar fatigue lives are found irrespective of the deep rolling temperature, these twins are not expected

The pore defects and surface roughness derived from additive manufacturing restrict applications in the production of ultra-long service time parts. Due to the high sensitivity of very high cycle fatigue (VHCF) resistance to defects, smaller defects may also become potential crack initiation sites. To remove these defects and consequently improve fatigue strength, three different post-processing routes

The simulation of the damage process is a challenge for researchers nowadays. In ductile materials, the continuum damage mechanics is based on the plasticity framework, but quasi-fragile materials have some characteristic phenomena such as localization and size effects, among others, that cannot be taken into account with this approach. The discrete element method has demonstrated considerable success

Axially loaded cyclic tests of a precipitation-hardened martensitic steel at different stress ratios in 3% NaCl solution and steam environment were conducted up to very high cycle fatigue regime. In-depth fracture surface observation, quantitative characterization of microstructural damage, and theoretical modeling were carried out to illustrate the physics and mechanics of micro-defect induced interior

In this work, fatigue crack growth (FCG) in the 2024-T351 aluminium alloy is studied using the plastic CTOD range, Δδp. Experimental tests were performed on 12 mm thick CT specimens in order to obtain FCG rate and in cylindrical specimens to obtain stress–strain loops. A numerical analysis replicated the experimental work in terms of material, geometry and loading conditions, but assuming pure plane

This work investigated the static and fatigue properties of 3D stitched composite and 2D laminated composite subjected to three-point bending loads. Four stress levels were carried out to investigate fatigue characteristics of the composites. The failure propagation of the composites and their fracture morphology were captured in detail using the high-speed camera. The results demonstrated that the

The microscopic stochastic fracture model is extended by introducing a concept of microscale damage, whose evolution law is derived by an energy analysis on the propagation of the cracks from nano- to microscale. A material parameter termed nano-to-micro comprehensive fracture energy is found to play a key role in the random and nonlinear behavior of concrete. It is shown that the proposed model can

Fatigue tests were conducted on an equiatomic CrMnFeCoNi high-entropy alloy with three different micro-stress concentration sources. A fatigue crack behavior analysis using a replica of a specimen surface, fractographic analysis in a fracture surface, fatigue crack shape analysis, and strain analysis under the fracture surface were performed. It was found that the fatigue crack extension mode was transited

The misorientation of nickel-base single crystal (NBSX) superalloy is always ignored in the current research, which in fact has a certain influence on the fatigue life of NBSXs. To investigate this influence, the fatigue tests of NBSX superalloy DD5 with different misorientation angles have been carried out at 980 °C, and the failure mechanism has been investigated based on the fractographic observation

Conventional engineering methods oftentimes have challenges in the quantification of crack nucleation processes from manufacturing defects that are relevant for engineering component lifing. We present peridynamic simulation framework for the description of the crack nucleation process from cluster of non-metallic inclusions in aluminum alloys. Our non-local simulation framework characterizes crack

Herein, the effect of multiple laser shock peening (LSP) on fatigue performance of aluminized steel and de-twinning behavior during cyclic deformation are investigated. Results reveal their fatigue lives successively increase within LSP times ranging from 0 to 3. Instead, life degradation is noticed after 4th LSP due to damaged adsorption layer. Consequently, the negative thermal ablations release

It is well-known that fatigue failures in VHCF originate from defects present within the risk-volume. Moreover, experimental results have shown that the larger the specimen size and the risk-volume, the shorter is the VHCF life. This is known as size-effect and is generally due to the statistical increment of the defect size with the material volume. In the paper, size-effect in VHCF is critically

This study investigated low-temperature fatigue behavior of fine-grained magnesium through tension–tension fatigue testing at the temperature of 0 °C. The applied stress profiles of fatigue testing were selected to cover a wide range of loading conditions including low, medium, and high loading stresses. Even when the maximum applied stress of fatigue testing was as high as 88% of the ultimate tensile

Piezo-electric ultrasonic fatigue machines are used to carry out fatigue tests more rapidly than what is possible using other technologies, at a frequency of 20kHz. The very high cycle fatigue (VHCF) domain can be studied with these machines as 109 cycles are reached within 14 h when specimens are loaded at stress amplitudes below the yield stress or conventional fatigue strength. The estimation of

The service damage mechanism of K403 Ni-based superalloy turbine blade with the aluminized coating are investigated systematically. Fracture morphologies are inspected with a failure event, and the microscopic damage mechanisms are explored based on the aluminized blades with different operation times. It concludes that the formation of massive pores, aggregation of bulk carbides, coarsening and breaking

The fatigue behavior of a C70250 alloy has been studied. The crack propagation behavior was investigated by performing fatigue crack propagation tests at load ratio R varying over the range 0.3-0.7. A considerable crack deflection and jagging was observed at low R-ratio. The study of the crack paths revealed that the closure effect is more relevant for R=0.3. In this case the crack path is characterized

This work presents global and local fatigue approaches for snug-tight (common in rack structures) and preloaded bolted joints using thin hot-dip galvanized steel plates, where the zinc coating results in a low friction coefficient. Moreover, S-N data supporting the current revision of Eurocode 3 (EN 1993-1-9) is generated by considering remote and net stresses computed directly or by numerical analysis

The Master S-N curve method enables the use of computationally efficient coarse FE models without overlooking accuracy in fatigue life estimates of welded structures. However, the use of the method in daily design practice of engineering offices faces the barrier of a largely available finite element post-processor. This paper intends to fill the gap on how to implement a finite element structural

Within the scope of this investigation, the quasi in-situ analysis of the fracture path of a FeCo alloy is performed. In the additively manufactured FeCo alloy sample, two U shaped notches are machined, and the sample is subjected to a fatigue test. EBSD maps are acquired near the U notch region before and after the fatigue test. Thus, crack propagation micro-mechanisms are evaluated by quasi in-situ

Ultrasonic surface rolling (USR), carburizing and the combined (Carburizing + USR) strengthening method were applied on the 20CrMoH steel, and the rolling contact fatigue (RCF) mechanisms of 20CrMoH steel subjected to different strengthening methods are analyzed. Results indicated that the combined strengthening method effectively increased the surface hardness value from 370 HV0.2 to 900 HV0.2, produced

An experimental-analytical investigation was conducted to study the fatigue properties of ZL114A aluminum alloy with low-velocity impact pit. The analysis of the fracture surfaces indicated that the cracks initiated at the position with tension residual stress rather than at the pit. Considering that the pit depth has a direct correlation with the magnitude of residual stresses, a new damage evolution

In the marine industry, designers utilize 5052-H32 marine grade series aluminum for its strength to weight ratio, and the ability of this series to resist marine corrosive environments. During the operating lifetime of a marine vessel, it experiences constant and variable amplitude loading conditions from the sea environment, plus overloads/underloads in the form of high frequency pulses. These high

Rolling contact fatigue (RCF) regularly causes mechanical components to fail under cyclic loads. Popular surface treatment processes such as case hardening (carburization), nitriding and tempered martensitic reduce the effect of RCF damage. This paper presents multi-stage S-N curve for steels with different surface treatments, under point and line contact conditions using RCF tribometers for the experiments

Fatigue is one of the main causes of failures as well as mechanical fractures in structural details made of aluminium alloys under cyclic loading, where the materials (during the crack growth process) are subject to the stress R-ratio effects and crack closure phenomenon. In this research work, a comparison of the effect of various crack closure/opening models on the fatigue crack growth behaviour