Fatigue Reliability Research Articles

Structure Design and Driving Dynamics Research of Crane Wheel Fatigue Test Device

In order to explore the fatigue damage of the crane wheel, the contact stress between the crane wheel and the steel rail was calculated. Moreover, the fatigue mechanism of crane wheels was also discussed by deriving the theoretical wheel pressure formula. As a result, a device design idea based on the fatigue mechanism of the crane wheel was proposed, where the device can be used to detect the bearing capacity, wear resistance and fatigue resistance of crane wheels. By using the simulation methods, the structure requirements and driving dynamics of the test device for different wheel diameters and wheel pressures were investigated and validated. Finally, the structural diagram of the fatigue test device is presented to provide the design guidance for the experiment research of the fatigue properties and reliability of crane wheels.

Characteristic fatigue strength and reliability of dental glass-ceramics: Effect of distinct surface treatments – Hydrofluoric acid etching and silane treatment vs one-step self-etching ceramic primer

The aim of this study was to mechanically characterize through flexural fatigue test two CAD-CAM glass-ceramics according to distinct surface etching protocols. To do so, feldspathic (FELD) and lithium disilicate (LD) glass ceramics were subjected to different surface treatments: (1) control – no treatment (Ctrl); (2) conventional protocol etching with 5% hydrofluoric acid followed by silane coupling agent application (HF + SIL; Monobond N, Ivoclar); or (3) using a self-etching ceramic primer (E&P; Monobond Etch & Prime, Ivoclar). Ceramic discs (N = 120; Ø = 12 mm; thickness = 1.2 mm) were produced from CAD-CAM blocks, with 60 being from FELD (VITABLOCS Mark II, Vita Zahnfabrik) and 60 from LD (IPS e.max CAD, Ivoclar). Next, 20 disks of each ceramic were allocated into three groups: Ctrl, HF + SIL, or E&P. Surface roughness data were collected on all samples before and after surface treatments (except for Ctrl). Cyclic fatigue (n = 15) biaxial flexural strength tests were performed by the piston-on-three-balls geometry (ISO 6872) considering the test parameters established from a monotonic test (n = 5). The monotonic test was carried out at a 1 mm/min loading rate and 500 kgf loading cell until fracture to obtain the failure data. The cyclic fatigue test was executed underwater at a frequency up to 20 Hz, with the first stress being 25% of the monotonic test for 5000 cycles, followed by increments of 5% of the monotonic test at each step of 10,000 cycles until failure (fracture). Complementary fractography, topography and Atomic Force Microscopy (AFM) analyses were performed. Characteristic Fatigue Strength (CFS) and Weibull modulus were analyzed by Weibull analysis using the fatigue test data. Roughness and complementary analysis data were analyzed by one-way ANOVA. The statistical results exhibited similar CFS among Ctrl, HF + SIL and E&P for both glass-ceramics. The survival analysis corroborates the findings, however the Weibull modulus pointed out superior structural reliability of FELD treated with the E&P group compared to HF + SIL. According to the complementary analyses, HF + SIL exhibited a higher surface area than E&P and Ctrl for FELD (p = 0.001). Roughness showed statistically significant differences among conditions for FELD (E&P < Ctrl = HF + SIL; p < 0.05) and no difference for LD (p > 0.05). Therefore, the CFS were not influenced by any condition evaluated for FELD and LD glass-ceramics; however, superior structural reliability (higher Weibull modulus) for the feldspathic ceramic treated with the E&P was observed.

Comparison of critical plane models for multiaxial fatigue life prediction

Background. The operation of numerous machines and units takes place under conditions of multi-axial cyclic loading, which, as a rule, is non-proportional. Evaluating the fatigue durability of metal alloys under conditions of multi-axial non-proportional loading is a relevant task in modern engineering. Solving this problem requires fatigue calculation methods that would consider operating conditions and properties of structural materials, including factors such as the type of stress state, loading trajectory, material sensitivity to non-proportional loading, and so on.Objective. To conduct a comparative analysis of a range of fatigue life models based on the concept of the critical plane, including the Fatemi-Socie, Wang-Brown, Smith-Watson-Topper, Liu I, and Liu II approaches, and to identify the limits and peculiarities of their application.Methods. The fatigue lives calculated using the selected models were compared with experimental results obtained for various metal alloys subjected to uniaxial tension-compression, alternating torsion, and proportional and non-proportional multiaxial loading.Results. The applicability limits of fatigue life models based on the critical plane concept were analyzed for different metal alloys under conditions of proportional and non-proportional multiaxial loading.Conclusions. The research results demonstrated that models requiring the use of material constants obtained from tests in both tension-compression and alternating torsion provide reliable fatigue life estimates for various types of metal alloys. Calculations based solely on fatigue curves from alternating torsion better correlate with the results of tests on ductile materials, while calculations based on criteria utilizing fatigue curves from tension-compression align more closely with results from tests on brittle materials.

Fatigue reliability assessment of load‐carrying cruciform welded joints with undercuts and misalignments

AbstractThe additional local stress concentration caused by undercut and misaligned defects could lead to lower fatigue strength of welded joints. The paper aims to investigate the effects of undercuts and misalignments on fatigue performance and reliability of Load‐carrying Cruciform Welded Joint (LCWJ) quantitatively by probabilistic statistics theory and fracture mechanics theory. Firstly, the geometrical characteristics of undercut and misalignment are summarized from the literature and our experiments. Subsequently, the probabilistic distributions of material fracture properties, the configurations of geometries, and flaws were evaluated under specific loading conditions. The fatigue strengths are further estimated by the probabilistic reliability theory by combining the actual fatigue data. The results demonstrate a clear disparity of fatigue crack growth threshold and resistances for the tested data of base metal and weldment. The level of defects determines the interval of fatigue life, and the larger the dispersion accompanying earlier fatigue failure occurs.

Fatigue fracture characteristics of normal concrete and high ductility geopolymer bonding based on DIC technique

This study reveals the adhesive fatigue behavior of normal concrete (NC)–high-ductility geopolymer (HDG) interfaces. A digital image correlation (DIC) technique was employed to capture the fracture characteristics. The fatigue stress level (β) and interfacial inclination angle (α) are the variables used in this research. The failure mode of the NC–HDG bonding interface was affected by α, and gradually transformed from compression crushing to debonding. The HDG matrix ultimately remained relatively intact compared to NC owing to the bridging effect of the polyvinyl-alcohol (PVA) fibers. The NC–HDG bonding interfaces experience three-phase fracture development: crack initiation phase, stable crack propagation phase, and final rapid crack propagation phase. At the earlier 15 %∼40 % of the fatigue life, the microcrack was initiated rather than propagated. The stable crack propagation phase presented a stabilized fracture propagation rate for most of the fatigue life. The cracks finally propagated rapidly until failure. A high fatigue stress accelerates damage accumulation and causes a greater degree of damage. Moreover, through inspection, the fatigue life of the NC–HDG interfaces was proven to abide by the Weibull distribution. The existing fatigue model was adopted to predict the fatigue life of an NC–HDG interface under a preset fatigue stress level and reliability.

Sensitivity of step‐stress accelerated fatigue‐life tests on type I censored data—An engineering perspective

AbstractStep‐stress accelerated life testing is often used to estimate the fatigue life or reliability of structural components. Various methods exist for designing the optimal accelerated life test and estimating the parameters of the fatigue‐life or reliability models. Although they are based on rigorous mathematical formulations, they sometimes result in inappropriate estimates of the model parameters if the experimental data consists of censored data. This article presents a robust engineering procedure for estimating the parameters of the fatigue‐life curve and its scatter, which combines an inverse power law and the two‐parametric Weibull distribution. The presented methodology is tested on use cases that stem from the experimental fatigue‐life data. The results show that the proposed approach can yield a good estimate of the fatigue‐life model. Moreover, it can be further concluded that the sensitivity of the fatigue‐life model to the type I censored data strongly depends on the data scatter.

Fatigue Reliability Assessment of RC Beams in Heavy-Haul Railways Based on Point Estimate Method.

Heavy-haul railways have a high passing frequency of trains with a large axle weight, causing rapid accumulation of fatigue damage in reinforced concrete (RC) bridge structures, which significantly affects the safety of the bridges. To study the fatigue reliability of RC beams in heavy-haul railways, the fatigue performance function for RC beams in heavy-haul railways was established, and the fatigue reliability assessment method for bridge structures in heavy-haul railways based on the point estimate method (PEM) was developed. An 8 meter-span plate beam in an existing heavy-haul railway illustrates the method. The train axle weight and dynamic coefficient were considered random variables, and the first four moments of equivalent stress ranges were obtained. The traffic quantity of the heavy-haul railways was investigated, and the fatigue reliability was evaluated using the proposed method. In addition, the effects of annual freight volume and train axle weight on fatigue reliability were discussed. Results indicate that PEM can effectively and accurately evaluate the fatigue reliability of RC beams in heavy-haul railways. In the first 20 years of operation, the fatigue failure probability was less than the limit value specified in the standard. The increase in annual traffic volume and train axle weight will cause a significant increase in fatigue failure probability. The research results of this paper are expected to provide an important basis for the design and maintenance of reinforced concrete bridges for heavy-haul railways in the future.

Probabilistic machine learning approach to reliability analysis of a bogie frame under dynamic loading

ABSTRACT This study aims to evaluate the fatigue failure probability of a bogie frame considering the variability of input parameters, including loading ( L ), endurance limit ( S e ), and fillet size ( r ), through a data-driven surrogate model. Mechanical tests were conducted to determine the mechanical properties of the material of the bogie frame while a combination of machine learning and FEA has been utilized to generate a dataset for the dynamic response of the bogie frame under main in-service fatigue loads. Nine machine learning-based surrogate models were constructed based on the actual response at a limited set of data points chosen by the Optimum space-filling algorithm, and their accuracy was investigated. It is found that the CatBoost model is the optimal algorithm to map the stochastic input parameters with the factor of safety as the output parameter and perform the reliability evaluation. Also, results reveal a fatigue reliability of 99.34% for the bogie frame under normal conditions, with a cumulative failure probability of less than 0.66% over a 30-year service life. Furthermore, the results show that the proposed machine learning-based approach is an efficient tool to evaluate the fatigue failure probability of the bogie frame with reasonable accuracy when a small set of training data is available. This study’s scope extends to providing comprehensive guidelines for employing machine learning methods for fatigue reliability analysis of complex vehicle structures in the presence of various stochastic variables.

Fatigue reliability prediction of shape memory alloy parts based on multi-scale high cycle fatigue criterion

Fatigue reliability prediction of shape memory alloy parts based on multi-scale high cycle fatigue criterion

Influence of ring gear flexibility on the fatigue reliability of planetary gear systems in heavy helicopters

Flexibility of ring gear rims significantly affects the mechanical properties of planetary transmissions at both levels of gear tooth meshing and system power sharing, and is one of the important design factors determining the service reliability of large aviation planetary systems. Therefore, to analyze the mechanism by which the flexibility of ring gear rims affects the fatigue reliability of planetary systems, in the framework of the stress-strength interference theory, a reliability assessment model for the planetary system is constructed based on a calculation logic extension for the full probability formula. Starting from balancing evaluation accuracy and evaluation cost, a hybrid finite element method and a gear tooth lifetime transformation test are employed to provide load and strength input variables for the reliability model respectively. Finally, a mapping relationship from ring gear rim flexibility to planetary system fatigue reliability is established. For the specific design scheme of planetary systems, a lower limit of the ring gear rim thickness can be determined according to the requirements of reliability indexes, so that the balance between reliability and lightweight can be achieved to some extent.

Measurement properties of instruments to measure the fatigue domain of vitality capacity in community-dwelling older people: an umbrella review of systematic reviews and meta-analysis.

Vitality capacity (VC) is a key domain of intrinsic capacity (IC) and is the underlying biophysiological aspect of IC. Energy and metabolism (E&M) is one of the domains of VC. Fatigue is one of the main characteristics of E&M. The aims of this umbrella review are (i) to identify the available instruments suitable for measuring fatigue in community-dwelling older adults and (ii) to critically review the measurement properties of the identified instruments. Umbrella review. Healthcare. Community-dwelling older adults. PubMed and Web of Knowledge were systematically screened for systematic reviews and meta-analysis reporting on fatigue instruments resulting in 2,263 articles (last search 5 December 2022). The COSMIN checklist was used to appraise psychometric properties and the AMSTAR for assessing methodological quality. Data on fatigue instruments, construct, reference period, assessment method, validated population, reliability, validity, responsiveness and predictive validity on negative health outcomes were extracted. 10 systematic reviews and 1 meta-analysis were included in this study. 70 fatigue instruments were identified in the literature and 21 were originally designed for fatigue. The Fatigue Severity Scale (FSS), Pittsburgh Fatigability Scale (PFS) and Visual Analogue scale (VAS-F), Fatigue Impact Scale (FIS) and the Functional Assessment of Chronic Illness Therapy Fatigue (FACIT-F) presented good psychometric properties. The FSS, FIS, FACIT-F, PFS and the VAS-F presented good psychometric properties in various conditions. Therefore, these instruments could be used to quantify trajectories in the domain E&M in the context of VC in community-dwelling older adults.

Sub-zero temperature flexural and flexural fatigue behaviour of glass fabric /epoxy composite tubular anti roll bars

Flexural and flexural fatigue reliability of glass fabric/epoxy composites used in anti-roll bars in room and sub-zero temperature regions at +25 °C, +10 °C, 0 °C, −10 °C, −20 °C, −30 °C, and −40 °C are investigated. The mean flexural strength of anti-roll bars substantially varies and improves in the sub-zero flexural property assessment (+25 °C to −40 °C). The fixed amplitude pulsating mode fatigue test was carried out at temperature points, i.e., 25 °C and −40 °C. The improvement in fatigue strength was observed 3.5 times at a sub-zero temperature of −40 °C. The fatigue durability of glass/epoxy composite anti-roll bars is observed to be longer at sub-zero temperatures due to residual stresses building up, an increase in glass transition temperature, and a lack of molecular mobility leading to higher chain stiffness in the epoxy matrix. The structural properties like flexural rigidity and modulus were calculated with reference to the shape factor and test temperatures for better correlations. These lifetime prediction studies under unpredictable operating conditions for automotive are crucial in the development of robust designs. Automotive performance under service conditions and environmental extremes will become increasingly important as lighter weight, longer life, and higher structural performance continue to evolve.

Fatigue Safety Assessment of Concrete Continuous Rigid Frame Bridge Based on Rain Flow Counting Method and Health Monitoring Data

The fatigue of concrete structures will gradually appear after being subjected to alternating loads for a long time, and the accidents caused by fatigue failure of bridge structures also appear from time to time. Aiming at the problem of degradation of long-span continuous rigid frame bridges due to fatigue and environmental effects, this paper suggests a method to analyze the fatigue degradation mechanism of this type of bridge, which combines long-term in-site monitoring data collected by the health monitoring system (HMS) and fatigue theory. In the paper, the authors mainly carry out the research work in the following aspects: First of all, a long-span continuous rigid frame bridge installed with HMS is used as an example, and a large amount of health monitoring data have been acquired, which can provide efficient information for fatigue in terms of equivalent stress range and cumulative number of stress cycles; next, for calculating the cumulative fatigue damage of the bridge structure, fatigue stress spectrum got by rain flow counting method, S-N curves and damage criteria are used for fatigue damage analysis. Moreover, it was considered a linear accumulation damage through the Palmgren-Miner rule for the counting of stress cycles. The health monitoring data are adopted to obtain fatigue stress data and the rain flow counting method is used to count the amplitude varying fatigue stress. The proposed fatigue reliability approach in the paper can estimate the fatigue damage degree and its evolution law of bridge structures well, and also can help bridge engineers do the assessment of future service duration.

LCF Lifetime Reliability Prediction of Turbine Blisks Using Marine Predators Algorithm-Based Kriging Method

To achieve the low-cycle fatigue (LCF) lifetime prediction and reliability estimation of turbine blisks, a Marine Predators Algorithm (MPA)-based Kriging (MPA-Kriging) method is developed by introducing the MPA into the Kriging model. To obtain the optimum hyperparameters of the Kriging surrogate model, the developed MPA-Kriging method replaces the gradient descent method with MPA and improves the modeling accuracy of Kriging modeling and simulation precision in reliability analysis. With respect to the MPA-Kriging model, the Kriging model is structured by matching the relation between the LCF lifetime and the relevant parameters to implement the reliability-based LCF lifetime prediction of an aeroengine high-pressure turbine blisk by considering the effect of fluid–thermal–structural interaction. According to the forecast, when the allowable value of LCF lifetime is 2957 cycles, allowing for engineering experience, the turbine degree of reliability is 0.9979. Through the comparison of methods, the proposed MPA-Kriging method is demonstrated to have high precision and efficiency in modeling and simulation for LCF lifetime reliability prediction of turbine blisks, which, in addition to the turbine blisk, provides a promising method for reliability evaluation of complicated structures. The work done in this study aims to expand and refine mechanical reliability theory.

The high-throughput bridge to the rapid evaluation of fatigue reliability of structural engineering materials

A high-throughput strategy using miniature specimens to evaluate the ASTM-defined fatigue endurance limits of some engineering materials through a high-throughput symmetry bending cantilever beam fatigue testing system is proposed. Employing such a high-throughput testing method for examining some typical engineering materials, we reveal that the fatigue limits obtained by the traditional testing standard can be directly determined by the high-throughput method-obtained fatigue limit multiplied by a suitable conversion factor. Such a high-throughput method was validated theoretically by the proposed crack initiation model and experimentally by the F316 stainless steel specimens subjected to different aging treatments and Gamma-ray irradiation.

Discussion on Fatigue Reliability Evaluation Method of Welded Structure of Carbody Based on Digital Twin

Abstract Taking the key welds of the heavy-duty gondola carbody as the research object, first, the fatigue assessment of the carbody is carried out based on the quasi-static the main S–N curve method, and the quasi-static evaluation method is discussed; second, the typical welds are selected. Based on the full-size bench physical test and virtual test of railway freight carbody, the quasi-static method is discussed; finally, the line test is used to verify the results. The results show that: (1) among all the load conditions in the quasi-static analysis of railway freight cars, the damage of the core plate needs to be considered according to different parts of the carbody, and this condition is effective for the evaluation of the bearing area of the linear load transfer of the carbody for the welds with nonlinear load transfer such as floor, the stress response caused by core plate load has the problem of over-estimation of damage. (2) The lap weld of floor and beam is less damaged under heavy load, but the stress response is larger in empty state, which indicates that the vibration effect should be considered in the design. (3) The virtual test can make up for the problem of traditional quasi-static analysis. The combination of the two can better realize the fatigue reliability evaluation of carbody.

An investigation of relationships between statistical dispersion of crankshaft’s fatigue properties and initial damage

Premature failure due to fatigue would occasionally happen even in a well-designed crankshaft. The microstructural nonuniformity (including micro-defects) plays an essential role in the premature failure due to fatigue, which can lead to the scatter of strength and fatigue life properties. In this paper, the statistical distribution of initial damage corresponding to microstructural nonuniformity has been introduced to uniformly characterize scattering behaviors of tensile strength, fatigue life and impact energy in sampling tests of crankshafts. The goal of this study is to investigate quantitative relationships between the dispersion of initial damage and scattering behaviors of the above sampling tests, so that dispersion properties of a crankshaft can be determined only by relatively simple experiments. By impact sampling tests and several single-throw crankshaft fatigue tests, probability density functions of initial damage have been determined for two crankshafts provided by different manufacturers. It is found that the fatigue reliability of a crankshaft depends on its actual dispersion properties. For a crankshaft with large dispersion of initial damage, the safety factor in the fatigue strength design should be sufficiently large to prevent its premature failure due to fatigue, rather than the one directly recommended in the design manual.

Fatigue Reliability Analysis of Composite Material Considering the Growth of Effective Stress and Critical Stiffness

Fatigue damage accumulation will not only cause the degradation of material performance but also lead to the growth of effective stress and critical stiffness. However, the existing fatigue reliability models usually ignore the effective stress growth and its influence on the critical stiffness of a composite material. This study considers the combined effects of performance degradation and effective stress growth, and a pair of fatigue reliability models for a composite material are presented. Firstly, the fatigue damage in a composite material is quantified by its performance degradation, and the fitting accuracy of several typical fatigue damage models is compared. Subsequently, the uncertainties of initial strength and initial stiffness are considered, and a pair of probabilistic models of residual strength and residual stiffness are proposed. The performance degradation data of Gr/PEEK [0/45/90/−45]2S laminates are utilized to verify the proposed probabilistic models. Finally, the effective stress growth mechanism and its influence on the failure threshold are elaborated, and a pair of fatigue reliability models for composite materials are developed. Moreover, the differences between the strength-based and stiffness-based reliability analysis results of composite materials are compared and discussed.

Fatigue Life Prediction of S235 Details Based on Dislocation Density

AbstractGlobal approaches have been the main procedure to design 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 in complex components. On the other hand, local approaches rely on the specific local damage 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 the fatigue life and establish reliable fatigue design approaches. Recently, Huffman proposed a fatigue damage model based on strain energy density and on the dislocation density of the material. In this regard, S235 was selected to perform a metallographic and mechanical assessment aiming to define the dislocation density of the material and to describe the fatigue behavior using the Huffman damage model. Additionally, fatigue tests on structural details (plate with hole) were conducted and results were compared with fatigue life predictions based on Huffman local approach. It was found that Huffman model based on dislocation density is a reliable approach to predict the fatigue life of structural steel details.

Dynamic impact behavior and notched fatigue life of GLARE laminates

As a member of the fiber metal laminates (FMLs) family, GLARE laminates have been widely used in aircraft skin structure due to the excellent resistance to dynamic impact and fatigue loadings. The low-velocity impact of GLARE laminates are conducted to explore the mechanical response on the impact energy and punch shape. The impact indentations are characterized by the damage morphology and quantitative dimension analysis. The mechanism of impact damage resistance is illuminated by the contact force-time curve, intra-laminar and inter-laminar damage modes. The lagrangian SPH modelling is employed to numerically analyze the bird-strike behavior of GLARE laminates, revealing the variation of bird particle flow and impact energy with different impact attitudes. The tension-tension fatigue of GLARE laminates is experimentally performed subjected to different stress levels. The influence of the circular open-hole on the fatigue residual life of GLARE laminates is studied. Considering the uncertainty of S-N curves, the probabilistic fatigue life P-S-N curves are developed under different survival probabilities. These would be more positive for the fatigue life estimation and reliability design for GLARE laminates in aircraft engineering application.