Fatigue Failure Criterion Research Articles

Effect of different fatigue constraints on optimal topology of structures with minimum weight

As one of the failure criteria with ascending importance for engineering problems, fatigue has recently been considered in topology optimization and different optimal topologies have been obtained which satisfying one or two fatigue failure criteria considered in the codes. The topologies and performance of those optimal designs are different if a different fatigue criterion is considered. Those difference may bring some concerns when those topologies are used in the real practice. In this paper, three different fatigue criteria are considered as constraints in structural optimization based on bi-directional evolutionary structural optimization. A modified p-norm approach is employed to decrease the computational cost for all examples. Comparisons of topologies and performance of the resultant optimal designs together with that from traditional compliance minimization designs clarify the effect of different fatigue criteria on those optimal designs for different design problems. These results will provide useful reference for engineers to design structures to avoid high frequency fatigue failure.

A Mini-Review on the Thermal Fatigue Properties of Copper Materials Applied at the Front-End of Synchrotron Radiation Facilities.

Oxygen-free high-conductivity copper (OFHC), chromium-zirconium copper (CuCrZr), and Glidcop® AL-15 are widely used in the high heat load absorber elements at the front end of synchrotron radiation facilities. It is necessary to choose the most suitable material according to the actual engineering conditions (such as the specific heat load, material performance, and costs). In the long-term service period, the absorber elements have to bear hundreds or kilowatts of high heat load and its "load-unload" cyclic loading mode. Therefore, the thermal fatigue and thermal creep properties of the materials are critical and have been extensively studied. In this paper, based on the published pieces of the literature, the thermal fatigue theory, experimental principles, methods, test standards, test types of equipment, and key indicators of the thermal fatigue performance of typical copper metal materials used in the front end of synchrotrons radiation Facilities are reviewed, as well as the relevant studies carried out by the well-known synchrotron radiation institutions. In particular, the fatigue failure criteria for these materials and some effective methods for improving the thermal fatigue resistance performance of the high-heat load components are also presented.

A numerical investigation of the interaction between interlaminar and intralaminar damages in a fatigued composite panel

AbstractThe fatigue behavior of composite materials is still a very challenging issue for the scientific community. So far, several numerical methodologies allow us to faithfully simulate the propagation of delamination due to fatigue. However, the reduction of material properties due to the applied cyclic load should be considered. The main objective of this work is to investigate the role of the material property degradation and the intralaminar damages on the propagation of delamination in composite laminates under fatigue loads. The numerical tool FT‐SMXB, based on the Paris Law and virtual crack closure technique, for the mimic of fatigue‐driven delamination, has been integrated with a user material subroutine, based on the generalized residual material property 7degradation model and the Hashin fatigue failure criteria. Typical aeronautical stiffened panel has been considered as test case. Matrix damages and strength degradation due to fatigue cycles have been found to influence the propagation of delamination.

Study of Fatigue-Damage Characteristics of Recycled Asphalt Mixture

To investigate the influence of methyl styrene block copolymers (SMC) modifier on the fatigue performance and damage evolution of recycled asphalt mixture (RAM), RAM with reclaimed asphalt pavement (RAP) ratios of 30%, 50%, and 70% and 90# asphalt mixture were used for four-point bending fatigue test. The fatigue performance and damage evolution process of RAM were analyzed using the stiffness attenuation rate and the relative change rate of dissipated energy (RDEC). Linear amplitude sweep (LAS) tests and atomic force microscopy (AFM) tests were carried out for mixed asphalt in the mixture. The results show that under the same test conditions, with the increase of RAP content, the damage development of RAM is faster, and the fatigue damage resistance is worse. Compared with 90# asphalt mixture, RAM has better fatigue resistance. The fatigue property of the mixed asphalt is better than that of the 90# asphalt. With different RAP contents, the modulus changes of RAM and mixed asphalt are almost the same on macro and micro scales, which proves that the difference of fatigue performance between 90# asphalt mixture and RAM probably is caused by asphalt. A fatigue failure criterion based on the peak dissipation energy is proposed for the LAS test, and the applicability and accuracy of the criterion were proved by grey correlation analysis. Under this criterion, the power function model is introduced to describe the development process of fatigue damage in LAS test, which has high fitting reliability.

Побудова критерію довготривалого руйнування втоми для тонкостінних шаруватих оболонок

A model and criterion of long-term fatigue failure for thin-walled layered shells is built, taking into account the influence of the type of stress state. The problem of calculating the number of cycles to failure under combined loading is considered. Solutions are built on the basis of the concept of equivalent stresses. The problem of determining local stresses in composites of random structure is formulated within the framework of the second-order nonlinear theory. The solution of the stochastic boundary value problem on determining the stress concentration in a unidirectional composite with a metal matrix (MMC) was obtained. To build a complete system of equations of the second order, the method of successive approximations is used. The parameters of the stress concentration at the boundary of the components are determined. The given examples show the importance of the influence of nonlinear properties on the redistribution of stresses near the fibers. The possibility of predicting the long-term strength of the material is shown. The necessary information about the material for the formulation of failure criteria is the S-N curves for individual components of the combined stresses.

Structural fatigue reliability evaluation based on probability analysis of the number of zero-crossings of stochastic response process

Structural fatigue failure is closely related to the number of stress cycles. Therefore, the number of the intersections between stochastic response process and zero-boundary is a key problem in structural fatigue reliability analysis. In this paper, the relationship between the number of the multiple intersections and the fatigue cumulative damage index is derived according to the Miner rule-based high cycle fatigue random cumulative damage index. Then, use random walk to approximately simulate Wiener process, and get the first intersection probability between Wiener process and the zero-boundary. Next, further utilize the renewal process to solve the distribution law of the number of intersections between the Wiener process and the zero-boundary in a period of time. Finally, based on the fatigue failure criterion considering the randomness of the failure threshold, the calculation formula the structural fatigue reliability is derived. As a practical example, the fatigue reliabilities of the key part of Metro Bogie under different operation periods are analyzed using the proposed method.

Comparison of some selected time-domain fatigue failure criteria dedicated for multi input random non-proportional loading conditions in industrial components

This paper presents time-domain procedure to evaluate High-Cycle Fatigue (HCF) life of industrial components with complicated geometries and subjected to multi-input random loading conditions. To this end, the authors discuss some well-known equivalent stress criteria which can consider the orientation of critical plane changes with the time in non-proportional loading conditions to estimate the time history of equivalent stress. This task is successfully accomplished by knowing time histories of local stress tensor components in a critical area of the part that is prone to failure. Next, two different categories were used to predict fatigue life of component: 1- Linear Damage Accumulation (LDA) rule by employing Rain-flow cycle counting and 2- probabilistic approach by utilizing level crossing counting method. To apply these methodologies and awareness of their challenges, a case study was performed on the automotive steering knuckle. Finally, the predicted lives were compared to experimental results, and the accuracies of different fatigue life assessment techniques were reported. The obtained results show that combination of Rain-flow cycle counting with the Liu-Zenner criterion and especially, with the Energy-based instant fatigue damage tracing proposed by Shariyat lead to the highest accuracies. However, using the probabilistic approach, we will get the response in a much shorter time compared to another category. Therefore, the choice which method to use also depends on the parameters of the research situation, and the interaction of the two factors of prediction accuracy and prediction time in the industry.

Study on fatigue life prediction method of composite laminates

Advanced composites have been widely used in aerospace field and transportation field in ground due to their excellent mechanical properties. Fatigue damage and life prediction of composites have always been the important and difficult issues in the field of composite mechanics. In this paper, the maximum stress criterion and Puck criterion were extended to fatigue failure criterion, and the fatigue damage analysis model of composite laminates was established by combining the gradual degradation model of material properties, the regularized fatigue life analysis method and the fatigue damage accumulation theory. Then, the model was used to predict the damage evolution and failure mechanism of composite laminates, and the fatigue tests with three stress levels (55%, 60% and 65%) were conducted. The fatigue life and failure mode of the numerical results matches well with the test results. Under fatigue loadings, the fatigue damage initiated from free edges on both sides of the plate to the inside of the laminates. The matrix damage first appeared in the 90° plies on two free sides, then the matrix damage and fiber damage of 45° plies were induced. The fiber damage of 0° ply finally appears and rapidly spreads to the center of laminates until the damage covers the entire cross section.

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.

Traction stress-based fatigue failure mode identification of load-carrying welded cruciform joints

This paper proposes an analytical solution of traction stress at the weld root of load-carrying welded cruciform joints, incorporating the effects of weld geometry, especially the gap between the loading and intermediate plates. Additionally, this study suggests fatigue failure criteria to differentiate toe and root failures and verifies these criteria by 372 experimental data. Results indicate that: (1) the analytical solution can quantify the stress state at the weld root and predict the root cracking angle; (2) the failure criteria are adequate to judge toe and root failures with high accuracy. Finally, weld geometry effects are discussed, and fatigue design for joints is suggested.

Modeling the temperature dependence of fatigue strength of metallic materials

In this study, a temperature-dependent fatigue failure criterion was proposed. A maximum energy density related to the fatigue failure of the material which is comprised of the strain energy and its equivalent heat energy was put forward at different temperatures. Two temperature-dependent fatigue strength models without fitting parameters were developed. The quantitative relationship between temperature, fatigue strength, Young's modulus, and melting point was established by the models. The model predictions were in good agreement with all the available experimental data for 17 metallic materials. A fast and simple non-destructive method for predicting temperature-dependent fatigue strength is realized in this work.

Experimental investigation on in-plane shear fatigue failure criteria of ± 45˚ angle-ply carbon epoxy composite

Designing load-bearing composite elements significantly relies on the material's response under different loading conditions, particularly fatigue. To improve the fatigue life prediction of composite structures, one of the role-playing properties, the in-plane shear properties variation, is focused on in this paper. Because of the ± 45˚ angle-ply tensile fatigue test advantages in terms of reliability and cost-efficiency, several fatigue experiments are conducted at certain stress levels using [±45]2s T300/L20 Carbon/Epoxy laminates. The surface temperature of specimens was measured using an infrared thermography camera during the fatigue test of Carbon/Epoxy composites. A strain-based fatigue life criterion capable of predicting the in-plane shear life is presented. The suggested maximum 5 percent strain limit could distinguish the in-plane shear fatigue failure from final laminate fracture. Furthermore, tangent shear modulus, secant shear modulus, strain energy density per cycle and cumulative strain energy density results approved the proposed strain-based life model, while each could be considered as a distinct criterion.

Computational and Experimental Methods of Strength Analysis of Polyurethane Diaphragms Operating under Cyclic Loadings

In this paper, the algorithm for strength analysis of diaphragms made of elastomers is described, and the strength analysis of the diaphragm made of polyurethane "Vitur" T-1413-85 is carried out. The results obtained showed that the description of the material behavior using the Moony-Rivlin model (5 parameters) gives the greatest accuracy. A comparison of the results of modeling the stress-strain state of the diaphragm and the experimental studies carried out to determine the displacements confirmed the adequacy of the chosen model (average correlation coefficient between numerical simulation and experiment R2= 0.98) for both studied diaphragm thicknesses. The conducted evaluation of the diaphragm resource according to the criteria of fatigue failure showed the correctness of the selected models of durability.

Inspection and maintenance planning for offshore wind structural components: integrating fatigue failure criteria with Bayesian networks and Markov decision processes

Exposed to the cyclic action of wind and waves, offshore wind structures are subject to fatigue deterioration processes throughout their operational life, therefore constituting a structural failure risk. In order to control the risk of adverse events, physics-based deterioration models, which often contain significant uncertainties, can be updated with information collected from inspections, thus enabling decision-makers to dictate more optimal and informed maintenance interventions. The identified decision rules are, however, influenced by the deterioration model and failure criterion specified in the formulation of the pre-posterior decision-making problem. In this paper, fatigue failure criteria are integrated with Bayesian networks and Markov decision processes. The proposed methodology is implemented in the numerical experiments, specified with various crack growth models and failure criteria, for the optimal management of an offshore wind structural detail under fatigue deterioration. Within the experiments, the crack propagation, structural reliability estimates, and the optimal policies derived through heuristics and partially observable Markov decision processes (POMDPs) are thoroughly analysed, demonstrating the capability of failure assessment diagram to model the structural redundancy in offshore wind substructures, as well as the adaptability of POMDP policies.

Low cost estimation of Wöhler and Goodman–Haigh curves of Ti‐6Al‐4V samples by considering the stress ratio effect

AbstractThe stress ratio effect on the fatigue life of materials is a topic which have been studied by two different approaches. On the one hand, several experiments, performed under different stress ratios are necessary to estimate the corresponding Wöhler curves. Afterwards, these curves are considered to estimate the fatigue life under a particular stress range. On the other hand, fatigue failure criteria for fluctuating stress like the Goodman–Haigh relationship, are applied to estimate the stress amplitude for a constant fatigue life. Based on the Stüssi function, this paper presents a low cost model to estimate Wöhler curves and constant fatigue Goodman–Haigh diagrams. This procedure requires a set of tests performed under a particular stress ratio from LCF to HCF, and data from minimum two additional stress ranges for each subsequent stress ratio. An application on data from Ti‐6Al‐4V samples manufactured by selective laser melting (SLM) is presented.

Investigation on Fatigue Performance of Asphalt Mixture Reinforced by Basalt Fiber.

Basalt fiber has been widely used in asphalt mixture due to its excellent mechanical properties and good combination with asphalt. In order to systematically evaluate the enhancement effect of basalt fiber on the fatigue performance of the mixtures, gradations of Stone Mastic Asphalt and Superpave with different nominal maximum aggregate sizes, namely SMA-13, SUP-20 and SUP-25, were prepared, and a four-point bending beam fatigue test was adopted under the strain control mode. The fatigue damage mode was assessed based on the phenomenology theory, energy dissipation theory and change rate of dissipated energy. The results showed that basalt fiber could well increase the fatigue life of the mixtures. Basalt fiber could also increase the cumulative dissipated energy of the mixtures, and it was linearly correlated with the fatigue life in double logarithmic coordinates. In the meantime, adding basalt fiber could increase the change rate of dissipated energy of the mixtures. Furthermore, it is not appropriate to take the stiffness modulus declined to 50% of the original as the fatigue failure criterion of the mixture; this paper suggested that it is reasonable when the stiffness modulus was 15–25% that of the initial. These findings provide a theoretical basis for exploring the fatigue failure of asphalt pavements.

Modelling the stiffness development in asphalt concrete to obtain fatigue failure criteria

The study of fatigue is critical to good usability and durability of asphalt pavements. Inaccurate calculation of the fatigue failure criteria can cause incorrect evaluation of the fatigue performance, leading to inaccurate prediction of the pavement performance and poor maintenance planning. This paper develops a stiffness change tendency method (SCTM) that can be used to model the stiffness evolution in asphalt concrete and determine critical laboratory fatigue failure points to characterise different fatigue damage stages. A logistic model was selected to represent the relationship between the log of the stiffness (E) and the log of the number of cycles (N) obtained from two-point bending (2PB) fatigue tests. The measured stiffness reduction versus loading curves were determined for a range of asphalt mixtures in unaged, aged and moisture damaged conditions by testing at various temperatures and strains. By analysing the derivatives of the logistic model, it is possible to identify three transition points associated with fatigue progression. There is good agreement between the laboratory data and the logistic model proposed, confirming that the logistic model is a good approximation to the stiffness reduction curves. The number of loading cycles associated with the first two transition points in the SCTM (NP1 and NP2) were compared to the value of N1 and Nfm obtained from the energy ratio (ER) method and the ratio of dissipated energy change (RDEC) method, respectively. There are no statistically-significant differences between the SCTM and two energy-based methods, proving that P1 can be viewed as the number of cycles to micro-crack initiation and propagation, and P2 can be defined as the macro-crack generation point (the true failure point). Three different mixtures are subjected to four-point bending (4PB) fatigue tests to demonstrate the applicability of the SCTM with different bitumen types, mixture grades and test methods. The SCTM provides a method to model stiffness development, obtain different fatigue failure criteria and characterise different fatigue damage stages, which could be useful in a simulation of pavement deterioration.

Uncertainty evaluation for bearing fatigue property of CFRP double-lap, single-bolt joints

The considerable uncertainty in mechanical properties of composite bolted joints not only prevents advanced composite materials from efficient applications, but also threatens the safety and reliability of the aircraft structures. In this paper, the uncertainty in bearing fatigue properties of a CFRP double-lap, single-bolt joint was evaluated by combing a Progressive Fatigue Damage Model (PFDM) with the interval analysis method. In the PFDM, a residual-strain-based gradual material degradation model and a strain-based fatigue failure criterion were combined with a micromechanics-based sudden material degradation model to predict fatigue properties of the joint. Based on the interval analysis, the key uncertain parameters, which were firstly picked out from eighteen structural parameters of the joint, were described by estimated intervals, and the envelope cases were determined to estimate the lower and upper bounds of fatigue properties of the joint. The predicted results have the same tendency with the experimental results in literatures, which indicates that the PFDM combined with the interval analysis shows potential in efficiently evaluating the fatigue reliability of the complex bolted joints with an adequate accuracy.

A Multi-Scale Submodel Method for Fatigue Analysis of Braided Composite Structures.

A multi-scale fatigue analysis method for braided ceramic matrix composites (CMCs) based on sub-models is developed in this paper. The finite element shape function is used as the interpolation function for transferring the displacement information between the macro-scale and meso-scale models. The fatigue failure criterion based on the shear lag theory is used to implement the coupling calculation of the meso-scale and micro-scale. Combining the meso-scale cell model and the fatigue failure criterion based on the shear lag theory, the fatigue life of 2D SiC/SiC is analyzed. The analysis results are in good agreement with the experimental results, which proves the accuracy of the meso-scale cell model and the fatigue life calculation method. A multi-scale sub-model fatigue analysis method is used to study the fatigue damage of 2D SiC/SiC stiffened plates under random tension–tension loads. The influence of the sub-models at different positions in the macro-model element on the analysis results was analyzed. The results shows that the fatigue analysis method proposed in this paper takes into account the damage condition of the meso-structured of composite material, and at the same time has high calculation efficiency, and has low requirements for modeling of the macro finite element model, which can be better applied to the fatigue analysis of CMCs structure.

Energy dissipation and rheological property degradation of asphalt binder under repeated shearing with different oscillation amplitudes

Time sweep test with four oscillation amplitudes was conducted to investigate the energy dissipation behavior and rheological property evolution of asphalt binder under repeated shearing. It was found that the energy dissipation behavior and rheological property evolution strongly depend on the oscillation amplitudes of fatigue loads and can both be majorly separated into two types. Variations in dissipated energy (DE) were related to the different damage modes of asphalt binder. In addition, the fatigue failure criteria derived from DE were evaluated. The dissipated energy ratio and cumulative energy ratio are not suitable for identifying fatigue failure point of asphalt binder.