Multiaxial Fatigue Failure Research Articles

A deep learning dataset for metal multiaxial fatigue life prediction

Multiaxial fatigue failure of metals, a common issue in industrial production, often leads to significant losses. Recently, many researchers have applied deep learning methods to predict the multiaxial fatigue life of metals, achieving promising results. Due to the high costs of fatigue testing, training data for deep learning is scarce and labor-intensive to collect. This study meets this need by creating a large-scale, high-quality dataset for multiaxial fatigue life prediction, consisting of 1167 samples from 40 materials collected from literature. The dataset includes key mechanical properties (elastic modulus, yield strength, tensile strength, Poisson’s ratio) and 48 loading paths, along with additional relevant information (composition ratios, processing conditions). Common deep learning models validated the dataset’s effectiveness. This dataset aims to support researchers applying deep learning to fatigue life prediction, addressing the long-standing issue of data scarcity, thereby advancing the intersection of artificial intelligence and metal fatigue research.

Fatigue performance testing and life prediction of welded fuel pipes

The external piping system which connects power devices, valve control devices, actuators, etc. is an essential system on the aero engine. Under the combined effects of high fluid pressure and external vibration, multiaxial fatigue failure is the main factor that seriously affects the safety of the piping system. The objective of this paper is to establish the multiaxial fatigue life model for the typical welded fuel pipe of the piping system by combining fatigue testing, simulation and theoretical analysis which is of great guiding significance for the engineering application of the piping system. Firstly, the fatigue limits of welded fuel pipes under no and 13.5 MPa internal pressure are obtained by rotational bending fatigue tests using the up-and-down method. Three additional stress levels of rotational bending fatigue tests under no internal pressure are supplemented and then the S-N curve is further obtained by the group method. Since the corresponding fracture surface of the specimens locates at the weld toe near the fixed end, peak stress method is adopted to evaluate the fatigue performance of the weld toe on the pipe specimens. In addition, by comparing the fatigue limit with no and 13.5 MPa internal pressured pipes, it is obvious that the equivalent uniaxial stress corrected by Gerber formula is not applicable for the multiaxial fatigue condition which is caused by the combined effect of fluid pressure and displacement load. The local stress concentration factor caused by the weld toe is determined and based on Findley critical plane model, the multiaxial fatigue life model is established which simultaneously takes the local stress concentration effect, mean stress effect and multiaxial stress effect into consideration. The results of rotational bending fatigue tests under 13.5 MPa internal pressure are within the triple error dispersion band and the accuracy of the proposed life model are verified.

Generalizing multiaxial vibration fatigue criteria in the frequency domain: A data-driven approach

Random vibration fatigue of structures is intrinsically multiaxial, driven by complex stress states. Non-proportional multiaxial stresses exacerbate fatigue damage compared to proportional stresses. Frequency domain fatigue analysis is generally more efficient for structures operating near natural frequencies. However, handling non-proportional multiaxial stress effects in the frequency domain remains challenging. This paper introduces a data-driven framework that reformulates time domain multiaxial fatigue failure criteria into their frequency domain counterparts, explicitly addressing non-proportional effects. The method introduces a non-proportional correction factor into the power spectral density of equivalent stress, determined through a data-driven approach, converting various time domain multiaxial fatigue criteria into their frequency domain equivalents. Combined with modal decomposition analysis, this approach efficiently evaluates multiaxial vibration fatigue for engineering structures, effectively accounting for non-proportional stress effects.

Multiaxial failure behavior and fatigue life prediction of unidirectional composite laminates

Complex coupling mechanisms exist between longitudinal and shear stress on the multiaxial fatigue behavior of composites. A thorough reanalysis of matrix shear failure mechanism under multiaxial fatigue loading is presented. Longitudinal single splitting fracture were analyzed and validated as an independent failure mode under multiaxial loading by analogy to the failure mechanism of natural composites. A new multiaxial fatigue life prediction model was established by double projection on the critical and subcritical fracture planes. Experiments on unidirectional tubular specimens were carried out under combined tension-torsion loadings to separate and identify the multiaxial fatigue failure behavior of composites. The proposed model has been verified using unidirectional laminates subjected to cyclic tension-torsion and off-axis loading, and the results showed that the predicted life is in good agreement with the experimental ones. Applications of three-dimensional digital image correlation (3D-DIC) and microscopy regarding verification in multiaxial damage mechanism are also addressed.

Strain-based method for fatigue failure prediction of additively manufactured lattice structures

Lattice structures find application in numerous technological domains, including aerospace and automotive industries for structural components, biomedical sector implants, and heat exchangers. In many instances, especially those pertaining to structural applications, fatigue resistance stands as a critical and stringent requirement. The objective of this paper is to advance the analysis of fatigue failure in additively manufactured lattice structures by introducing a predictive fatigue failure model based on the finite element (FE) method and experimentally validating the results. The model utilizes linear homogenization to reduce computational effort in FE simulations. By employing a strain-based parameter, the most critical lattice cell is identified, enabling the prediction of fatigue crack nucleation locations. The Crossland multiaxial fatigue failure criterion is employed to assess the equivalent stress, furnishing the fatigue limit threshold essential for predicting component failure. Inconel 625 specimens are manufactured via the laser-based powder bed fusion of metals additive manufacturing process. In order to validate the model, cantilevers comprising octa-truss lattice cells in both uniform and graded configurations undergo experimental testing subjected to bending loads within the high cycle fatigue regime. The proposed methodology effectively forecasts the location of failure in seventeen out of eighteen samples, establishing itself as a valuable tool for lattice fatigue analysis. Failure consistently manifests in sections of uniform and graded lattice structures characterized by the maximum strain tensor norm. The estimated maximum force required to prevent fatigue failure in the samples is 20 N, based on the computed Crossland equivalent stress.

Multiaxial Fatigue Analysis of Connecting Bolt at High-Speed Train Axle Box under Structural Subharmonic Resonance.

Based on the dynamic characteristics of the axle box front cover of high-speed trains in the subharmonic resonance state, the nonlinear single-degree-of-freedom (SDOF) model was proved to be reasonable, and reasons for the ineffectiveness of the common prevention methods for preventing bolt failure were analyzed firstly. Then, dynamic stress of the bolt was simulated by innovatively adopting the linear method based on frequency response analysis. The stress simulation method was verified to be practical under the subharmonic resonance state by analyzing and comparing the experimental and numerical results of the bolted front cover. It was proved that the linear method was accurate enough to simulate the dynamic stress of bolts, which is of great engineering significance. In addition to the transverse resonance stress of bolts caused by drastic vertical vibration of the front cover, the tensile resonance stress at the root of the first engaged thread was too large to be neglected on account of the first-order bending modes of bolts. Next, equivalent stress amplitude of the multiaxial stresses was obtained by means of the octahedral shear stress criterion. Finally, fatigue life of bolts was predicted in terms of S-N curve suitable for bolt fatigue life analysis. It argued that the bolts were prone to multiaxial fatigue failure when the front cover was in subharmonic resonance for more than 26.8 h, and the fatigue life of bolts could be greatly improved when the wheel polygonization was eliminated by shortening the wheel reprofiling interval.

Predicting multiaxial fatigue life of FGH96 superalloy based on machine learning models by considering failure process and loading paths

Wide applications of powder metallurgy superalloys in mechanical engineering imply the great significance of studying their mechanical properties. Fatigue property of superalloys is complicated because of many influencing factors with variability. This means the difficulty to correctly predict a real-valued fatigue life due to the propagation of error. Specially, extreme dispersion of multiaxial fatigue life is an important challenge of fatigue life prediction for superalloys. In this paper, we focus on the difficulty and dispersion by developing machine learning (ML) models for predicting interval-valued fatigue life of FGH96 superalloy under multiaxial loadings. Some data extracted from fatigue failure process of FGH96 superalloy is used to develop ML methods such as back-propagation neural network (BP), support vector regression (SVR) and random forest (RF). Then considering the randomness in the data originating from multiaxial loading paths, measures of sample geometry and mechanical loading, testing system error and others, the low cycle fatigue life of FGH96 superalloy is predicted as an interval with a probability distribution. The obtained results are analyzed and compared with the fatigue experimental observations of FGH96 superalloy under six loading paths. It is found that the multiaxial fatigue failure behavior of FGH96 superalloy can be effectively described, and the developed ML models exhibit some advantages to tackle the difficulty and dispersion in predicting multiaxial fatigue life of alloys.

Cyclic stress–strain response and crystal plasticity finite element analysis of AISI 9310 steel in biaxial fatigue loading

AbstractThere are still many gaps in the research on the multiaxial fatigue failure mechanism of the gear shaft. In this paper, cyclic stress–strain response and biaxial fatigue damage characteristics of gear steel AISI 9310 were investigated. The specimens showed obvious cyclic softening characteristics at all phase angles, and the softening rate was directly associated with the initiation and propagation of cracks. The fractographies at different phase angles revealed that the specimens under out‐of‐phase loading suffered fatigue failure caused by a single crack source on the surface, while the fatigue crack under in‐phase loading was gathered together by the propagation of different crack sources. Finally, the established crystal plastic finite element model showed a good prediction of the plastic strain energy density at different phase angles, and the maximum error was 13.03%. Furthermore, a biaxial fatigue life prediction method was proposed, with a maximum error of 39.5%.

Multiaxial high-cycle fatigue failure and life prediction based on critical plane method

Multiaxial high-cycle fatigue failure criterion and life prediction is important for structural components under complex low stress. A new multiaxial high-cycle fatigue damage parameter based on the plane of maximum shear stress is proposed, which includes the maximum shear stress amplitude, normal stress amplitude and maximum equivalent normal stress. The maximum equivalent normal stress is defined in the form of SWT stress function considering the influence of mean stress. The feasibility of the proposed failure criterion and life prediction model is verified by test data of different materials. The predicted results show that the life prediction error of the proposed fatigue model is basically within three times by comparing with McDiarmid, Matake, Crossland and Papadopoulos fatigue models.

A multi-axial and high-cycle fatigue life prediction model based on critical plane criterion

Accurate prediction of fatigue failure behavior and fatigue life of structures or materials under multi-axial loading are important for engineering application. In this work, a multi-axial and high-cycle fatigue failure model based on the critical plane criterion is proposed with considering the influences of material property and loading path on the initiation and growth of fatigue cracks. A material parameter, defined as the ratio of tensile yield strength σy and torsional yield strength τy, is introduced to describe the mechanical properties of the material. For σy/τy<3, it is considered that the crack growth under the multi-axial fatigue load is mainly controlled by the maximum normal stress. While for σy/τy>3, it is considered that the crack growth under the multi-axial fatigue load is mainly controlled by the maximum shear stress. Experimental results of three kinds of material were applied for model validation. For all materials, most predictions are within the ±2 times scatter band of fatigue life and only few data are around ±3 times scatter band. Good agreements of the predicted fatigue life by the model with experimental results illustrated the model applicability. The model provides meaningful tool for predicting multi-axial fatigue life of materials under different loading parameters.

High‐efficiency algorithms for simulating metal failure effects under multiaxial repeated loadings

AbstractHigh‐efficiency algorithms are proposed for numerically integrating elasto‐plastic rate equations for the purpose of simulating metal failure effects under repeated loading conditions. Results are obtained with a newly established elasto‐plasticity model which can automatically simulate both low and high cycle fatigue failure effects, with reference to neither damage‐like variables nor ad hoc failure criteria. Novelties are incorporated in a few respects. First, multiaxial loading processes with arbitrarily changing principal stresses and axes can be treated in a broad sense beyond usually treated proportional loading cases. Second, by means of the commonly used ‐invariant of the deviatoric stress, multiaxial loading cases can be directly treated just as in the uniaxial loading case. Third, high cost in time consumption can be considerably reduced in evaluating both low and high cycle failure effects. Numerical examples are presented for simulating uniaxial and multiaxial fatigue failure effects and simulation results are in good agreement with experimental data. Results show that the computation speed with the new algorithms exceeds 600 times faster than usual integration algorithms.

Study on the Resonant Torsion Vibration in Hourglass Specimens under VHCF Loading

The problem of cyclic loading under pure torsion is an important problem for numerous different industrial applications, such as shafts, springs, blades, and others. The loading conditions for aircraft, railway, automobile industries are often corresponding to long fatigue life. The rough estimation shows that the number of cycles for springs in car engine is exceeds 108 cycle while blades for aircraft turbine may undergo more than 1010 loading cycles. Such, to provide a safety in service life for such elements a multiaxial fatigue failure criterion is needed to predict damage zone location and fatigue life. This paper is aimed to introduce the multi regime approach to predict fatigue damage zone evaluation and number of cycles to crack initiation and total fatigue life. The presented approach is based on damage theory supplemented by multiaxial failure criterion. The proposed model includes the algorithm for automatic determination the fatigue loading range (low-, high- or very-high cycle fatigue) and allows different crack opening modes. To show how to apply the proposed approach and verify the results of calculation the series of numerical simulation on hourglass specimen subjected to VHCF pure torsion is performed. The results of numerical simulation are compared to VHCF torsion tests.

Multiaxial stress mapping and fatigue failure prediction of aircraft hydraulic pipes

Frequent fatigue failures of aircraft hydraulic pipes were caused by a stress concentration site in the form of a circumferential groove at the constrained pipe ends. The grooves were formed as a result of the crimping of a metallic sleeve on the pipes. Internal hydraulic pressure fluctuations during aircraft flight resulted in multiaxial and alternating stresses at the constrained (fractured) end. The complete stress state was found using FEM ‘Frame 3D’ MATLAB® code and analytical stress concentration factors. The calculated stresses not only mapped well with the fractured patterns of a failed pipe but also correlated to the computational stress analysis performed separately in an FEA software. The stress calculations were further utilised for fatigue life estimation of the pipe with and without the presence of circumferential groove. The load spectrum of the pipe was developed using 73 flying hours data of hydraulic fluctuations and converting those into stresses. Various stress amplitudes and load ratios were segregated from the cyclic stresses using the rainflow counting method. A linear constant lifeline diagram and Miner’s rule of damage accumulation were used for fatigue life estimation. A significant decrease (from 12,500 to 165 flying hours) in the service life of the pipe was predicted due to the presence of the stress concentration. The predictions matched well with the observed failure trend (life) of the pipe.

The mean stress and phase angle effect on multiaxial fatigue behavior of a TiAl alloy: Failure analysis and life modeling

In the presence of multiaxial fatigue loadings with multiple loading variables, fatigue behavior of material differs from those under in-phase (IP) multiaxial fatigue loadings. The co-existence of non-zero mean stress and phase angle could be extremely harmful to fatigue resistance of material. In this case, it is vital for researchers engaging in relative fields to put forward capable life prediction methods. In this study, the mechanical property of a TiAl alloy under combined tension-torsion (CTT) fatigue loadings is investigated through experiments. The applied fatigue load contains non-zero mean stress components as well as phase angle components. The fracture of specimen is observed by scanning electron microscope (SEM) to investigate the correspondence between multiaxial fatigue life and failure behavior. Susmel and Lazzarin's (S-L) fatigue criterion is critically reviewed to put forward a modification on its intrinsic drawback. In parallel, a correction factor is introduced to make the modified Wӧhler curve method (MWCM) feasible for multiaxial fatigue life prediction with multiple loading variables. Verified by experimental results of present work, the proposed method is of good accuracy compared with Matake method and McDiarmid method.

Multiaxial and Uniaxial Fatigue Failure Evaluation Using Modal Velocities

The presented work aims at evaluating the results of uniaxial and multiaxial fatigue failure tests using velocity and acceleration measurements. A specimen containing damaging modes at different eigenfrequencies is introduced. The tests are conducted on an electrodynamic 3D-shaker system using a random vibration environment. Different fatigue times are observed between uniaxial and multiaxial excitation. Based on the velocity and acceleration measurements, fatigue damage values are calculated for each test. While the fatigue damage values of velocities are similar between uniaxial and multiaxial tests, large deviations can be detected when using accelerations as base for the calculation. Thus, experimental verification for recently proposed multiaxial fatigue damage calculations based on different vibrational quantities is made possible.

Through calculation method of fatigue damage

A kinetic model of damage development under cyclic loading is proposed to describe the process of fatigue failure. To determine the coefficients of the kinetic equation of damage, the well-known criterion of multiaxial fatigue failure is used. A numerical method for calculating crack-like zones up to macro fracture is proposed. The results of fatigue experiments for various geometries and asymmetry coefficients were reproduced; the operability of the model and calculation algorithm were verified.

A novel model for low-cycle multiaxial fatigue life prediction based on the critical plane-damage parameter.

Multiaxial fatigue of the components is a very complex behavior. This analyzes the multiaxial fatigue failure mechanism, reviews and compares the advantages and disadvantages of the classic model. The fatigue failure mechanism and fatigue life under multiaxial loading are derived through theoretical analysis and formulas, and finally verified with the results of multiaxial fatigue tests. The model of multiaxial fatigue life for low-cycle fatigue life prediction model not only improves the prediction accuracy of the classic model, but also considers the effects of non-proportional additional hardening phenomena and fatigue failure modes. The model is proved to be effective in low-cycle fatigue life prediction under different loading paths and types for different materials. Compared with the other three classical models, the proposed model has higher life prediction accuracy and good engineering applicability.

Numerical tool with mean-stress correction for fatigue life estimation of composite plates

In this paper a numerical fatigue assessment method is presented for the cyclic life estimate of composite plates via continuous strength and stiffness degradation calculation combined with mean stress correction and multiaxial fatigue failure criterion check. The most value-adding features of this methodology are the simultaneous monitoring of mean stress dependent strength and stiffness degradation over successive cycles using empirical interaction type degradation rules. The procedure has also been coded in a form of a complex automated workflow where the actual stress state for each ply is evaluated by appropriate Finite Element assessment and the residual strength and the ply-based stiffness analysis combined with failure check is executed in an external Python routine. The practical use of the automated workflow is presented via the virtual analysis of load- and strain-controlled tension-tension type fatigue tests of unidirectional specimens as well as a cross-ply open-hole test piece. Based on the results the expected damage mechanism is discussed.

Formulation of multiaxial fatigue failure criteria for spectral method

Fatigue life assessment under multiaxial loading requires the use of multiaxial fatigue failure criteria which are defined in time and frequency domain. Frequency domain criteria are created via formulations using former criteria in the time domain. Therefore, there is a need for a general approach to formulate criteria in the frequency domain based on existing proposals. We discuss methods to determine parameters appearing in the frequency domain criteria; in particular, we present the critical plane approach proposed by Macha and other proposals based on stress invariants. An attempt to generalize the problem is presented and discussed in the section of conclusions.

Design optimization of composite wind turbine blades considering tortuous lightning strike and non-proportional multi-axial fatigue damage

This article presents a design optimization framework which integrates realistic lightning strike electrostatic and fatigue analyses for designing reliable and economical composite wind turbine blades. The novel aspects of this work include: a parametric tortuous lightning stepped leader model that reflects one of the true natural characteristics of the lightning phenomenon; and characterization of both the lightning strike dielectric breakdown failure and multi-axial fatigue failure mechanisms for structural design of composite wind turbine blades. A case study of the structural design optimization of a 5 MW composite wind turbine blade is tested using the framework with two optimization solvers: sequential quadratic programming (SQP) and Bayesian optimization (BO). SQP produces a superior optimal design to BO. In the optimum blade design based on the SQP algorithm, the lightning safety ratio increased by 32% and the expected fatigue life increased more than 15 times compared with the initial blade design.