Determination Of Fatigue Life Research Articles

Strength and fatigue analysis of mudline wellhead and its tie-back system in offshore drilling

This article presents a new operational approach for mudline wellheads, aimed at transforming exploration wells into development wells, thus reducing costs and construction time in marginal oil fields. It includes a fatigue life analysis of mudline wellhead systems and tie-back systems at different platform heights (20 m and 100 m). The study develops mechanical models to assess structural integrity under environmental loads such as wind, waves, and currents. Stress concentrations, especially at connection points, are analyzed to determine fatigue life. The study not only establishes the service life for both water depth scenarios but also offers structural optimization suggestions for the tie-back system. Incorporating marine environmental data, it provides a comprehensive strength and fatigue analysis, ensuring the structural safety of the mudline wellhead and tie-back system. This research underpins the economic viability of the mudline wellhead tie-back operation mode, contributing significantly to offshore drilling design, efficiency, and sustainability, marking progress in offshore engineering.

Determination of fatigue life under low frequency fatigue loading based on temperature evolution

The wind turbine blades are key components of wind turbines. During the working process, the blades are subjected to fatigue loading, resulting in the failure of wind turbine blades. The surface temperature of blade materials will change when subjected to fatigue loading and the temperature rise rate of blade surface under fatigue loading can be used as an index to predict fatigue life. However, the frequency of fatigue loading on the wind turbine blades is low, the non-adiabatic response under low frequency fatigue loading would lead to temperature dissipation. In this paper, fatigue life prediction under low frequency fatigue loading was studied. Based on the law of energy conservation and the laws of heat conduction, heat convection, heat radiation, the temperature evolution of materials under low frequency fatigue loading was theoretically analyzed. Epoxy resin was selected as testing material and fatigue tests were conducted on epoxy resin specimens. During the fatigue test, the infrared thermal imager was used to monitor the samples surface temperature in real-time. The results show that the predicted life considering temperature dissipation effect is closer to the real life. Meanwhile, the general application of life prediction model is further verified by metal material. This work can be used for predicting the fatigue life of wind turbine blades under low frequency.

Determination of wheel polygonal wear limit and fatigue life of railway bogie frames considering wheel/rail excitation

Determination of wheel polygonal wear limit and fatigue life of railway bogie frames considering wheel/rail excitation

Predicting the fatigue survival probability of High-Strength steel Wires: A Weibull model incorporating corrosion and stress ratios

Fatigue behavior of high-strength steel wires in bridge stay cables is critical to bridge reliability, as these wires experience varying stress ratios, stress ranges, and corrosion levels that significantly impact their fatigue life. Existing models typically predict fatigue life under different stress ranges and corrosion conditions but often neglect the critical influence of stress ratio, leading to potential inaccuracies. This paper introduces an innovative R-C-S-N Weibull model that integrates stress ratio, stress range, and corrosion effects to improve fatigue life predictions. Model parameters are determined through maximum likelihood estimation (MLE) and validated using both experimental data and literature sources. The model achieves a Mean Absolute Error (MAE) of 0.10, indicating minimal deviation from observed values, while a Skewness of 0.13 reflects a balanced yet slightly conservative distribution. Additionally, the 0.4–0.6 Probability Interval Coverage of 0.6 shows that 60% of predictions fall within this central range, underscoring model stability. Results indicate that corrosion has a more pronounced impact on fatigue life at lower stress ranges, with stress ratio playing a secondary but significant role. In the model, parameter D quantifies the effect of corrosion, and the shape parameter β governs variability. Sensitivity analysis highlights stress range and corrosion as the most influential factors in determining fatigue life. The model’s reliable predictive capabilities make it valuable for assessing the remaining life of corroded steel wires in bridge structures, particularly when combined with non-destructive testing methods, providing a robust and partially conservative tool for structural health monitoring.

Effect of stick and slip zones on fatigue life of a slewing ball bearing

Prediction of fatigue life of slewing ball bearings is challenging due to the influence of large deformations and adverse lubrication conditions. The present study presents an elegant simulation model that considers the flexibility of the supporting elements of the slewing bearing along with stick/slip zones at the raceway-ball contact interface. Using the stresses predicted by the simulation model, relative fatigue life using stick/slip condition versus no-friction condition is computed. A sensitivity study of the ball contact force, ball contact angle, coefficient of friction and raceway conformity is also performed. The present study also evaluates the results in comparison with full-sliding assumptions. The final results show that the stick/slip zone determination at the contact interface is beneficial for accurate determination of fatigue life of slewing bearings.

Experimental analysis of failure modes depending on different loading conditions applied on cylindrical polyamide 66 gears

Abstract Engineering plastics are increasingly used for gearing systems, such as in the automotive sector, e-mobility sector, and household appliances. The basic task of the gearing system is to efficiently transfer power from the source to the application user. The use of engineering plastics for gearing applications is conditioned by the lack of tribological characteristics of material pairs which influence on fatigue and wear behaviour of the whole gearing system. The paper presents testing of the steel/Polyamide 66-gear by determining fatigue life in an infinite area, considering high precision optical measurements in the range of micro-meter accuracy of abrasion flank wear together with surface temperature in contact, providing an important database for engineers about material suitability for appropriate mechanical systems. Observing the results, gear flank wear of PA66 HT is directly proportional to the meshing temperature and torque. Thermal melting is a characteristic failure mode of the polymer gears which are exposed to higher load levels. In the middle torques, the dominant failure mode is flank fracture known as pitch point fracture. The greater impact of the gear wear mechanism occurs at lower torques where initial crack propagation starts at the pitch point and ends in the tooth root area.

A framework to identify fatigue failure of asphalt binders under multiple aging levels using linear amplitude and time sweep testing

ABSTRACT The identification of fatigue failure can significantly affect the determination and prediction of fatigue life for a given asphalt binder. In this work, different approaches for identifying the fatigue failure on linear amplitude sweep (LAS) and time sweep (TS) are compared, especially for highly-aged asphalt binders. The candidate methods include traditional 50% or 80% reduction in pseudo-stiffness parameter (denoted as C0.5 and C0.2), peak stored pseudo-strain energy (PSE), peak C × N and peak phase angle. For asphalt binder at multiple aging levels, peak C × N is found to be effective in defining fatigue failure of TS testing. Meanwhile, peak stored PSE is suitable as the failure definition of LAS because it can capture the benefit of polymer modification and has a high accuracy for fatigue life prediction. Nf in strain-control TS test determined by different failure definitions shows that aging can increase the fatigue resistance at early-aged levels and then decrease the fatigue resistance at highly-aged levels. In general, the selected failure definitions have little influence on the trend of Nf with age levels. The purpose of this work is to select the logical failure definitions of asphalt binder under multiple aging levels.

Developing statistical tools to analyze historical stress-controlled fatigue data in additively manufactured austenitic stainless steel

The development of robust fatigue property data sets for additively manufactured 316L austenitic stainless steels is hindered by the small sample sizes, inconsistent reporting of material properties and processing conditions, and differences in testing procedures for current sources of testing data. By applying standardization and categorization protocols to account for these shortcomings, historical data sets were aggregated into a single large data set and analyzed in greater detail, providing new levels of insight into the stress-controlled fatigue behavior of additively manufactured materials. Using this single aggregated data set, scatter was quantified using an eigenvalue analysis, and a multi-variable statistical model for predicting the mean fatigue life was developed. Interactions between variables and the sensitivity to different loading conditions were then identified, with the scatter in the data being attributed to differences in testing and post-processing condition such as surface condition and heat treatment, and the model was used to identify the role that each variable plays in determining fatigue life. An analysis of the fatigue responses across the aggregated data set using clustering algorithms allowed two distinct trends to be identified and attributed to the differing roles of microstructure and porosity on the resulting fatigue lives across different equivalent stress amplitude ranges.

Dislocation density-based fatigue approach for structural steel details

Global approaches have been the main procedure for designing structural details and components under fatigue loading. This procedure is easy to apply but it disregards not only the effect of the material type but also the influence of the geometry. On the other hand, local approaches rely on the specific local parameters that can be assessed for each type of material and detail geometry. The parameters derived from low cycle fatigue (LCF) tests are the most common damage parameters used to predict fatigue life and establish fatigue design approaches. Recently, Huffman proposed a fatigue damage model based on strain energy density and dislocation density of the material. In this regard, two structural steels were selected to perform a metallographic and mechanical characterization aiming to determine fatigue life parameters and dislocation density. The fatigue behavior of these materials was evaluated using strain-Morrow, SWT, and strain-Huffman parameters, and the dislocation density values obtained by XRD were analyzed. Additionally, experimental results from fatigue tests on structural details (plate with hole) were compared with fatigue life predictions based on each local model. It was found that the Huffman model based on dislocation density is a reliable approach to predict the fatigue life of structural steel details.

Machine Learning-Based Fatigue Life Prediction of Functionally Graded Materials Using Material Extrusion Technology

In this study, the research investigates the prediction of fatigue life for Functionally Graded Materials (FGM) specimens comprising Polylactic acid (PLA) and Thermoplastic Polyurethane (TPU). For this, Machine learning (ML) techniques, including Random Forest (RF), Support Vector Machine (SVM), and Artificial Neural Network (ANN) are utilized. A predictive in-house code is developed for each technique, thereby facilitating the fatigue performance of layered deposited specimens subjected to varying cyclic loadings. In order to verify the effectiveness of the ML technique, a comparative analysis among all is reported based on empirically determined fatigue life obtained values. RF is proven to be the most suitable technique with minimal error percentage in obtained results with optimally synchronized data sets in a minimum time frame. Subsequently, the application of ML in those predictions is reported for future aspects in augmenting the operational efficiency associated with fatigue life prediction.

Evaluation of Rutting, Fatigue, and Moisture Resistance of Low-Energy Asphalt Mixtures Modified by Crumb Rubber

Low-energy asphalt (LEA) mixture, as an alternative to hot mix asphalt (HMA) due to its lower mixing temperature, has advantages such as reducing energy consumption and environmental pollutants. LEA has poor performance characteristics due to the presence of water in its manufacturing process and low mixing temperature. All the studies about LEA have been focused only on investigating the performance of this asphalt mixture, and the effect of additives in its modification is one of the research gaps in this field. Therefore, the use of crumb rubber (CR) and determining its optimal percentage in modifying the performance characteristics of LEA is considered an innovation of this research. In this research, the performance characteristics of LEA modified by 10%, 15%, and 20% CR were evaluated. In order to examine the rutting behavior, moisture sensitivity and fatigue resistance, dynamic creep, indirect tensile strength (ITS), and four-point bending beam tests were applied, respectively. The results of creep curves and flow numbers (FNs) indicated that modifying LEA by 15% increased the rutting resistance by 1.92 and 2.3 times, respectively, compared to the HMA specimen at the stress level of 207 and 310 kPa. Moreover, the evaluation of the creep strain slope revealed that modifying LEA significantly reduced stress sensitivity. ITS test showed an increase in tensile strength ratio by 22% in the specimen with 10% CR compared to the unmodified specimen. In the evaluation of fatigue resistance, while LEA containing 10% CR had almost similar results to the HMA specimen, other specimens represented a shorter fatigue life, so that with the increase in CR percentage, the fatigue life decreased. Determination of fatigue life by energy ratio and Rowe and Bouldin criteria showed similar results. Finally, by determining the plateau value (PV) in the ratio of the dissipated energy change method, the lowest PV was assigned to the 10% CR-modified LEA and HMA specimens, respectively.

Influence of Build Orientation on Surface Roughness and Fatigue Life of the Al2024-RAM2 Alloy Produced by Laser Powder Bed Fusion (L-PBF)

Additive manufacturing of high strength Al alloys brings problems with hot cracking during rapid solidification. One of the ways to solve this challenge is technology developed by the Elementum 3D company. The way consists of inoculation by ceramic nanoparticles using RAM technology. When applying the L-PBF method, a very fine equiaxed microstructure with exceptional properties and without cracks is created. This paper offers the results and discussion of the microstructure, surface roughness and fatigue life of the high-strength Al2024-RAM2 alloy made from a gas atomized powder with an additive of 2 wt.% ceramic nanoparticles on the base of Ti. The specimens for fatigue tests were produced in different orientations relative to the building platform and left in the as-built conditions with different surface quality (roughness). The specimens were T6 heat-treated. The treatment caused a coarsening of a part of the fine grains. After T6 heat treatment, the hardness increased significantly, which occurred by precipitation hardening. Fatigue tests of specimens with different build orientation were performed in plane bending and the experimentally determined fatigue life was discussed in terms of surface roughness and material microstructure.

Fatigue life determination based on infrared thermographic data for MultiDirectional (MD) CFRP composite laminates

Infrared thermography is a useful tool for the rapid determination of fatigue properties. A previously proposed fatigue life model, which combines the stiffness degradation k(N) with thermographic data ΔTstab, has been successfully applied to UD and ±45° CFRP laminates. In view of more complex damage mechanisms in multidirectional laminates, the model is modified in this work to overcome the conservative predictions. The S-N curves determined by the modified model are compared with the experimental results of traditional fatigue tests on Quasi-Isotropic (QI) and cross-ply CFRP laminates. Very good consistency was observed. In particular, the S-N curve corresponding to fatigue life of Nfl=106 cycles is conservative compared to that from the traditional fatigue test results, but the maximum safety factors are no more than 1.15 and 1.08 for QI and cross-ply laminates, respectively. Both S-N curves corresponding to Nfl=107 cycles for two tested laminates lie within the 95% confidence interval of traditional experimental results. Therefore, based on infrared thermographic data, the modified model proposed in this study is more general. It allows to determine the S-N curves of QI and cross-ply CFRP laminates just in about ten hours of testing machine time instead of one month and a half using traditional fatigue tests, even though more experimental data (other types of MD stacking sequences, composite materials, under other fatigue modes, etc.) are necessary to demonstrate the applicability of modified model to all types of MD laminates.

StressLife: A Short-Time Approach for the Determination of a Trend S-N Curve in and beyond the HCF Regime for the Steels 20MnMoNi5-5 and SAE 1045.

Within the scope of this research, a new short-time procedure designated as StressLifeHCF was developed. Through a combination of classic fatigue testing and non-destructive monitoring of the material response due to cyclic loading, a process-oriented fatigue life determination can be carried out. A total of two load increases and two constant amplitude tests are required for this procedure. By using data from non-destructive measurements, the parameters of the elastic approach according to Basquin and the plastic approach according to Manson-Coffin were determined and combined within the StressLifeHCF calculation. Furthermore, two additional variations of the StressLifeHCF method were developed in order to be able to accurately describe the S-N curve over a wider range. The main focus of this research was 20MnMoNi5-5 steel, which is a ferritic-bainitic steel (1.6310). This steel is widely used for spraylines in German nuclear power plants. In order to validate the findings, tests were also performed on an SAE 1045 steel (1.1191).

Fatigue damage development in 10CrMo9-10 steel for power plant pipes in as-received state and after 280,000 h of exploitation

This paper discusses an effect of 280,000 h of exploitation under internal pressure of 2.9 MPa and high temperature of 540 °C on the mechanical properties of 10CrMo9-10 (10H2M) power engineering steel. The mechanical response of the specimens obtained from two pipes: a new in the as-received state and exploited for a long period was assessed through the uniaxial tensile tests and subsequent fatigue tests. The long-term, high-temperature exposure of 10H2M steel resulted in the deterioration of its mechanical properties and was quantitatively described as a function of the fatigue damage measure, φ, and the fatigue damage parameter D. Finally, the proposed methodology of power exponent approximation with both damage sensitive parameters (φ, D) enabled for successful determination of the 10H2M steel fatigue life.

Influence of surface roughness on fatigue performace of additively manufactured metal matrix composite Al2024–RAM2 alloy

Numerous studies on Laser Powder Bed Fusion (L-PBF) have demonstrated the necessity to refine microstructure of additive manufactured (AM) parts to eliminate hot cracking and anisotropy to improve L-PBF processability. It has been shown that ceramic nanoparticles based on Ti can be extremely effective inoculant resulting in fine grains structure for high strength aluminum alloys without hot cracking. The company ELEMENTUM 3D has patented production process of reactive additive manufacturing (RAM) with a low content of ceramic nanoparticles as Al2024-RAM2. This contribution presents results of an experimental determination of high cycle fatigue life of L-PBF Al2024-RAM2 alloy with as-built (i.e., rough) and polished surface. Experiments were done on miniature specimens printed on a SLM 280 HL system with a layer thickness of 60 µm. The specimens were tested in cyclic plane bending at a load ratio of R = 0 at a frequency of 25 Hz. Moreover, the microstructure was investigated by means of scanning and transmission electron microscopy.

A novel methodology for estimating damage evolution and energy dissipation for steel fiber reinforced concrete under flexural fatigue loading

The present research proposes a novel methodology for estimating mechanical degradation for steel fiber reinforced concrete. An experimental campaign was carried out in order to characterize the fatigue response of the cementitious composite and to determine fatigue life using S-N curves based on Weibull distribution. Using the experimental results, two empirical correlations were proposed to estimate damage evolution and energy release growth rate as a function of the number of cycles. Both use the initial stiffness and the energy release of the studied material as an input, which are both evaluated as the flexural strength at 0.50 mm of crack mouth opening displacement.

Effect of sample geometry and air voids on the 3-Point Bend Cylinder (3PBC) fatigue test for asphalt concrete

As part of NCHRP IDEA IDEA Project 218, a new testing protocol called Three-Point Bend Cylinder (3PBC) test was developed to speed up the fatigue characterization of asphalt mixtures. In this paper, the effects of sample geometry and air voids on the 3PBC fatigue test were investigated. The results showed that the VECD theory was successfully applied to all the selected geometries. This allowed the determination of fatigue life at any desired strain levels, temperatures, and frequencies. Based on the selected levels for each factor, specimen diameter significantly affected the 3PBC test results and fatigue lives. Specimen span length and air void content, however, did not appear to have considerable effects on the fatigue lives of the asphalt material. It should be noted that the sample variability of the 3PBC test may have softened the effects of air voids on the fatigue lives of the asphalt material.

Determination of Fatigue Life and Failure Location of Vehicle Cylindrical LPG Fuel Tanks

Abstract This study addresses the determination of the fatigue life and its failure locations of the vehicle cylindrical LPG fuel tanks using both experimental and finite element analysis (FEA) methods. The experimental investigations performed as an accelerated fatigue tests are carried out using a hydraulics test unit in which the cylinders are internally pressurized by hydraulic oil. The LPG cylinders are subjected to repeated cyclic pressure varying from zero to service pressure of the tank. The FEA modeling of these tanks are developed in three dimensional (3D) using non-uniform geometrical parameters and nonlinear material properties. These models are also subjected to zero-based high cycle fatigue pressure load considering the stress life approach. The FEA modeling process is also simulated in non-homogeneous material conditions. Therefore, the fatigue life performance and failure location of the cylindrical LPG fuel tanks are predicted and compared to the experimental results.

Design recommendations for container ship side-shell structure under fatigue strength assessment

The aim of the work is to evaluate various designs in order to arrive at some guidelines for choosing a good standard design by means of a fatigue damage analysis in the connection between longitudinal stiffener and transverse web frame on container ship side-shell structure located in the upper wing torsional box. Design proposals and recommendations are developed, based on numerical and experimental analysis, which allow, from different structural configurations formed by combinations between cut-outs and collar plates, to establish more and less adequate structural designs in one of the ships with the greatest future projection. In the first phase, the cut-out without influence of the longitudinal stiffener is studied and the stress state and fatigue assessment are determined. In the second phase, the longitudinal stiffener is taken into account under the presence of the collar plate in the model and different geometrical alternatives (thickness, ducktail, overlap and radius of curvature) and their influence on the determination of stress and fatigue life are studied. From the different configurations, the most appropriate combination is established and structural solutions are proposed in order to improve the design.