Constant Amplitude Cyclic Loading Research Articles

Experimental study of mechanical properties of artificial dam for coal mine underground reservoir under cyclic loading and unloading

This study investigates the stability of an artificial dam used in an underground reservoir in a coal mine under periodic weighting imposed by overlying rock strata. For this purpose, cyclic loading and unloading tests with different stress amplitudes were designed. Differences in the mechanical performance of the artificial dam with and without overlying strata were analyzed using a uniaxial compression test. The mechanical properties of the structure under constant-amplitude cyclic loading and unloading were characterized. Further, the law of influence of stress amplitude on stability was discussed. A formula for predicting the mechanical performance of the artificial dam with its overlying rocks (hereafter referred to as the complex) was finally derived and was suitable for clarifying the law of damage in the complex under cyclic loading and unloading. The results showed that the complex had changed the internal structure of rocks. The strength and deformation of the complex were intermediate to that of either single structure. All three underwent brittle failure. During the constant-amplitude loading and unloading tests, the hysteresis loop could be divided into three phases, namely, sparse, dense, and sparse again, with a shift in the turning point in rock deformation memory effect. As the stress amplitude increased during the test, the damping ratio of the specimens decreased, and the area of the hysteresis loop increased non-linearly. The dynamic elastic modulus decreased first and then increased. The confidence interval for the formula fitted based on the test results was above 97%. Damage to the complex caused by constant-amplitude loading and unloading could be divided into three stages. An increase in peak stress served as a catalyst for the evolution of small cracks within the specimens into median and large cracks, thereby accelerating the damage process.

Unidirectional horizontal cyclic behaviors of the monopile-wheel composite foundation in sand

The monopile-wheel composite foundation is an innovative type of offshore wind turbine (OWT) foundation with good bearing capacity. The foundation is subjected to cyclic loads from wind, waves, and tides, so it is necessary to study its horizontal cyclic characteristics. By introducing cyclic degradation constitutive and Rayleigh damping parameters, numerical models are generated and validated by comparing with laboratory experiment results. The laws of horizontal accumulated displacement of the composite foundation are then explored through changes in the cycle amplitude, number, wheel diameter, height of loading point and pre-vertical load. The main findings are that the composite foundation is more likely to reach a stable displacement under constant amplitude cyclic loading compared to that of monopile. Under transient dynamic response (74 % of the horizontal ultimate bearing capacity), accumulated displacement will increase rapidly regardless of the foundation form. The composite foundation has smaller hysteresis loop area and slower accumulation rate of bending moment. The soil pressure weakening of the monopile mainly occurs in front of the pile, while that of the composite foundation mainly occurs under the wheel. After cyclic loading, the V–H envelopes for the composite foundation contract unevenly inwards. Above these, prediction methods for the cumulative displacement, maximum bending moment and V–H envelopes for composite foundation considering cyclic degradation are proposed.

Experimental study on damage evolution process, seepage characteristics, and energy response of columnar jointed basalt under true triaxial cyclic loading

The physical response of Columnar Jointed Basalt (CJB) under a stress–seepage coupling field is of great significance for dam safety and oil and gas reservoir evaluation. A true triaxial experimental machine was used for investigating the deformation, damage evolution characteristics, seepage properties, and energy response of the CJB. Before the start of the test, a series of uniaxial compression tests were used to determine the ratio of similar materials, and the cyclic loading test results indicate that: The strength characteristics of CJB decreases slowly and then increases rapidly as the dip angle β varies from 0° to 90° under two loading conditions of the tiered cyclic loading (T–C) and the constant amplitude cyclic loading (CA–C), showing an obvious U–shaped trend, and four different loading stages can be distinguished by characteristic stress. In the yield stage, the stress–strain curve shows an obvious plastic hysteresis loop, there is a strong correlation between the failure modes of the CJB and β of the specimen, the joint surface gradually deteriorates owing to loading and unloading conditions, and structural control failure occurs widely in specimens. The damage evolution process is discussed in combination with the Load–Unloading Response Ratio, and the relative damage amount (Df) is defined by cycle index. The permeability–axial stress relationship of the specimen conforms to the power exponential relationship, and the permeability evolution characteristics are strongly correlated with the degree of damage. The energy response of the CJB were investigated by tress–strain curve, under two loading modes, T–C and CA–C, the cumulative curves of dissipation energy Ed can be fitted by an exponential function and a logarithmic function, respectively. The findings of this research hold immense importance for clarifying the mechanical and seepage properties of CJB under a stress–seepage coupling field.

Mechanical response and microscopic damage mechanism of pre-flawed sandstone subjected to monotonic and multilevel cyclic loading: A laboratory-scale investigation

This study aims to investigate the mechanical response and acoustic emission (AE) characteristic of pre-flawed sandstone under both monotonic and multilevel constant-amplitude cyclic loads. Specifically, we explored how coplanar flaw angle and load type impact the strength and deformation behavior and microscopic damage mechanism. Results indicated that being fluctuated before rising with increasing fissure angle under monotonic loading, the peak strength of the specimen first increased slowly and then steeply under cyclic loading. The effect of multilevel cyclic loading on the mechanical parameters was more significant. For a single fatigue stage, the specimen underwent greater deformation in early cycles, which subsequently stabilized. Similar variation pattern was also reflected by AE count/energy/b-value. Crack behaviors were dominated by the fissure angle and load type and medium-scale crack accounted for 74.83%–86.44% of total crack. Compared with monotonic loading, crack distribution of specimen under cyclic loading was more complicated. Meanwhile, a simple model was proposed to describe the damage evolution of sandstone under cyclic loading. Finally, SEM images revealed that the microstructures at the fracture were mainly composed of intergranular fracture, and percentage of transgranular fracture jumped under cyclic loading due to the rapid release of elastic energy caused by high loading rate.

Experimental study on effects of cyclic loading paths on cracking behavior and fracture characteristics of granite

To investigate the impact of cyclic loading paths on the Mode I fracture characteristics of granite, a series of fracture tests were conducted on semi-circular bend (SCB) specimens using acoustic emission (AE), digital image correlation (DIC) and 3D scanning. The tests included monotonic loading, variable amplitude (VA) cyclic loading, and tiered constant amplitude (TCA) cyclic loading. The results demonstrated that VA cyclic loading leads to an average enhancement of 5.6% in fracture toughness, whereas TCA cyclic loading results in an average reduction of 3.7% in fracture toughness. During cyclic loading and unloading, the TCA loading path exhibits a higher rate of cumulative plastic deformation growth and greater magnitude cumulative plastic deformation compared to the VA loading path. Additionally, detailed observations from 3D scanning revealed that under cyclic loading, the fracture trajectories and surface morphology exhibit more tortuosity and roughness compared to monotonic loading, particularly in the case of TCA cyclic loading. Furthermore, according to the AE and DIC analysis, the proportion of microcrack initiation and stable propagation stage, cumulative AE counts and fracture process zone (FPZ) size generated under VA cyclic loading are greater than those generated under TCA cyclic loading, displaying a consistent variation pattern with fracture toughness. The changes of fracture properties can be attributed to a competition between the compaction-induced hardening effect and the cracking-induced damage effect. A higher cyclic upper limit and incomplete unloading are more likely to accelerate the growth of the irreversible crack damage and rapid crack extension, resulting in weakened rock fracture properties. These findings provide important references for rock instability control in underground rock engineering.

Mesoscopic hysteretic model and parameter study on cemented sand and gravel material

According to the hysteresis loop characteristics of the cemented sand and gravel (CSG) material under an equal amplitude cyclic loading test, taking into account the influence of cycle times and plastic residual strain, a plastic mesoscopic hysteretic model of the CSG material was established based on the theoretical Preisach-Mayergoyz model. The sensitivity of the mechanical characteristics corresponding to the shape parameters, the fatigue life (frequency), the total number of hysteretic mesoscopic elastic units (HMEU), and the size of the load step in the model was analyzed. The results showed that the shape parameters mainly affect the form of the hysteresis loop curves in the loading and unloading sections, the total amount of HUEU affects the accuracy of expressing the mechanical properties of CSG materials, and the load step affects the fitting accuracy of the hysteresis loop curves. Based on the parameter analysis, the theoretical range of the mesoscopic parameters suitable for the mesoscopic hysteretic model of CSG are shown that, the shape parameter ξ is 1.2–3.0 and η is less than 0.3, the total number of HMEU is 500–10,000, the load step should not be significant when its value is greater than 0.08 MPa. The mesoscopic hysteretic model of CSG can also predict the fatigue life of CSG materials under constant amplitude cyclic loading. The research results can provide a theoretical basis for the dynamic characteristics and fatigue failure analysis of CSG materials.

Analysis of crack closure and wake of plasticity with the distributed dislocation technique

A new method for the analysis of plasticity-induced closure of finite cracks is developed based on the distributed dislocation technique. The method is applied to analyse closure and opening processes for an embedded fatigue crack propagating under constant amplitude cyclic loading. The obtained solution and presented results can serve as a benchmark for numerical procedures utilising the same yield-strip methodology. Comparison with past numerical studies reveals similar trends, though there are some differences in the crack tip opening values, particularly for low and negative R-ratios. The latter may indicate the need for a better approach to the discretisation of the contact, direct and reverse plasticity zones in the numerical procedures which utilise the same methodology. The developed method is general, and it can be adapted to evaluate the crack tip opening stress for other crack geometries and loading conditions.

Mechanical fatigue testing in silico: Dynamic evolution of material properties of nanoscale biological particles

Biological particles have evolved to possess mechanical characteristics necessary to carry out their functions. We developed a computational approach to "fatigue testing in silico", in which constant-amplitude cyclic loading is applied to a particle to explore its mechanobiology. We used this approach to describe dynamic evolution of nanomaterial properties and low-cycle fatigue in the thin spherical encapsulin shell, thick spherical Cowpea Chlorotic Mottle Virus (CCMV) capsid, and thick cylindrical microtubule (MT) fragment over 20 cycles of deformation. Changing structures and force-deformation curves enabled us to describe their damage-dependent biomechanics (strength, deformability, stiffness), thermodynamics (released and dissipated energies, enthalpy, and entropy) and material properties (toughness). Thick CCMV and MT particles experience material fatigue due to slow recovery and damage accumulation over 3-5 loading cycles; thin encapsulin shells show little fatigue due to rapid remodeling and limited damage. The results obtained challenge the existing paradigm: damage in biological particles is partially reversible owing to particle's partial recovery; fatigue crack may or may not grow with each loading cycle and may heal; and particles adapt to deformation amplitude and frequency to minimize the energy dissipated. Using crack size to quantitate damage is problematic as several cracks might form simultaneously in a particle. Dynamic evolution of strength, deformability, and stiffness, can be predicted by analyzing the cycle number (N) dependent damage, [Formula: see text] , where α is a power law and Nf is fatigue life. Fatigue testing in silico can now be used to explore damage-induced changes in the material properties of other biological particles. STATEMENT OF SIGNIFICANCE: Biological particles possess mechanical characteristics necessary to perform their functions. We developed "fatigue testing in silico" approach, which employes Langevin Dynamics simulations of constant-amplitude cyclic loading of nanoscale biological particles, to explore dynamic evolution of the mechanical, energetic, and material properties of the thin and thick spherical particles of encapsulin and Cowpea Chlorotic Mottle Virus, and the microtubule filament fragment. Our study of damage growth and fatigue development challenge the existing paradigm. Damage in biological particles is partially reversible as fatigue crack might heal with each loading cycle. Particles adapt to deformation amplitude and frequency to minimize energy dissipation. The evolution of strength, deformability, and stiffness, can be accurately predicted by analyzing the damage growth in particle structure.

A Study on Fatigue Crack Closure Associated with the Growth of Long Crack in a New Titanium Alloy

In this article, the fatigue crack closure in a new titanium alloy is carried out under constant amplitude cyclic loading with the combination of the simulation method and experiments. A numerical simulation of the crack closure effect on a new titanium alloy under different load ratios was carried out to analyze the effect of grid size on the crack closure level and to obtain the fatigue crack opening load level under different load ratios. The experimental study of the fatigue crack growth rate of the new titanium alloy under different load ratios has demonstrated that the fatigue crack growth rate is affected by the stress ratio. With the increase in load ratio, the crack expansion rate of new titanium also increases. Combined with the simulation, the experiments show that the crack closure effect induced by the plastic region at the crack tip is the main reason for the load ratio effect on the fatigue crack expansion rate of the new titanium alloy.

Resistivity and damage of coal under cyclic loading and unloading

The stability of the coal in underground coal mining can be reduced greatly by mining activities and seepage water. Studying the failure and damage evolution of water-saturated coal under cyclic loading is therefore of great importance. Conducting single-axis equal-amplitude cyclic loading and unloading tests of water-saturated coal, this paper studied the resistivity response and analyzed the relationship between resistivity and strain field with Digital Image Correlation (DIC) in coal cyclic loading. The damage in coal cyclic loading was quantitatively characterized by the damage variables and damage constitutive equations based on electrical resistivity. The results show that the response of resistivity and DIC is regular and complementary. In the loading stage, the strain field has an opposite trend to the resistivity, which decreases as the load force increases; In the unloading stage, the resistivity increases correspondingly, but the shearing strain decreases. The above responses correlate with the sample failure: as the number of cycles increases, the sample's internal damage accumulates, and the resistivity and strain increase accordingly. The two damage variables and the trend of plastic strain are in good agreement. The damage constitutive model's calculation agrees with the experimental results. The resistivity method is able to objectively describe the whole damage process of saturated water coal under constant amplitude cyclic loading, thus contributing to the understanding of the damage mechanism of coal and rock subjected to complex stresses, which is of great practical significance and value to the safe and efficient production of coal mines.

Deformation Behaviour and Damage Evolution of Carbonaceous Phyllite under Cyclic Triaxial Loading.

Rocks present complex deformation behaviours and damage processes under triaxial cyclic loading-a subject not yet sufficiently researched. This paper performed triaxial multistage constant-amplitude cyclic loading experiments under different confining stresses on carbonaceous phyllite. The degradation process is analysed by investigating the variation of elastic modulus ES, Poisson's ratio υ, irreversible strain εirr and energy. Moreover, the rock's failure mode is explored from both macro and micro perspectives. The results showed that the increase in stress level caused the decrease of ES in a step-like form, and the constant-amplitude cyclic loading in each stress level caused a slow decrease of ES, while the υ increased with stress level and constant-amplitude cycles in a similar form. εirr accumulated rapidly at first and then slowly at each stress level; the stress level and irreversible axial strain are related by an exponential function. In terms of energy evolution analysis, the damage to rock can be represented by the cumulative damage energy, there were deceleration accumulations and stability accumulation stages of damage at all stress levels, and an acceleration accumulation stage occurred when the rock was close to failure. The failures of rock under cyclic loading are mainly shear failures, accompanied by grain crushing.

Mean stress correction and fatigue failure criteria for hyperelastic adhesive joints

ABSTRACT The work investigates failure criteria and mean stress correction approaches for the fatigue lifetime prediction of two hyperelastic adhesives (a polyurethane, PU, and a silicon-modified polymer, SMP). Fatigue experiments are carried under constant amplitude cyclic loading at RT and 40°C/60% r.h with butt- and the thick-adherend-shear-test-joints at three stress ratios R = −1, 0.1 and 0.5. Three mean stress correction approaches are evaluated: Goodman (static strength based), Schütz (mean stress sensitivity based) and Kujawski & Ellyin (parameter optimisation based). Fatigue failure criteria considered are: Drucker-Prager (linear-relation with the hydrostatic stress), Beltrami (quadratic relationship with the hydrostatic stress), and a multivariable nominal shear and tensile stresses criterion (data-based). The comparison is based on prediction accuracy (R-squared of master SN curves) and complexity of parameter determination. The highest values of R-squared were obtained by the Kujawski and Ellyin correction, followed by Schütz and then Goodman. However, the complexity of parameter determination follows an opposite trend with Goodman being the lightest approach. Failure criteria yielded comparable results with the multivariable criterion having the advantage of not dealing with FEA, but being limited to joints with nearly uniform stress distribution. Finally, compared to Drucker-Prager, the Beltrami criterion had a more robust parameter determination.

Study on Granite Damage and Fracture Behavior and Theoretical Model Based on Pre-Peak Constant Amplitude Cyclic Loading Test Combined with Acoustic Emission Technology

Study on Granite Damage and Fracture Behavior and Theoretical Model Based on Pre-Peak Constant Amplitude Cyclic Loading Test Combined with Acoustic Emission Technology

Rutting Predictions in Flexible Airfield Pavements Using a Newly Modified Drucker–Prager Combined Hardening Model with Progressively Evolving Yield Surface

Granular materials subjected to compressive cyclic loading of constant amplitude when modeled using an isotropic hardening, elastoplastic Drucker-Prager (DP) model do not accumulate significant plastic strain beyond the first loading cycle. This can lead to predictions of permanent deformations in airfield asphalt pavements that do not compare well with experimental observations. Accordingly, this paper proposes a modification to the existing DP model as a means of accounting for this shortcoming. A new parameter, γ, is introduced, which causes the yield surface to progressively evolve and shrink in size during successive load cycles to account for microphysical restructuring of the granular material during constant amplitude cyclic loading. The constitutive model is implemented within the finite element code ABAQUS through the user material subroutine UMAT. The model is subsequently tested via 2D finite element analysis on pavement sections by applying it to the granular base and modeling all other layers as linear elastic. Validation is undertaken by comparing rutting with field experimental values from an accelerated pavement testing program. Increased equivalent plastic strain and vertical plastic strains are observed with this modification, thereby resulting in rutting values that are significantly closer to the experimental data than those obtained with the classical DP model.

Fatigue Damage Mitigation for Welded Beam-to-Column Connections in Steel High-Rise Buildings Using Passive Vibration Control

To investigate the use of vibration control systems in fatigue damage mitigation for welded beam-to-column connections in steel high-rise buildings, cases of both a single connection under constant amplitude cyclic loading and multi-connections in a high-rise building under the stochastic wind, with and without the fluid viscous damper (VFD) and the tuned mass damper (TMD), are discussed respectively. The finite element analysis and the fatigue assessment are conducted so that the mitigation effect, the effect of technical parameters and the conditions of both high-cycle fatigue and low-cycle fatigue are all discussed. The results show that the VFD and the TMD systems are both effective in the mitigation of local fatigue damage along with the structural displacement for both cases. The VFD generally has a better mitigation effect than the TMD and it starts to take effect instantly with the external loading, but it causes a phase difference in structural responses, while the situation of the TMD is quite the opposite. The displacement and the local stress show similar and synchronous mitigation trends so that the damping systems can be designed based on either of them. The VFD should be designed with a smaller damping exponent and a larger damping coefficient in a braced installation form, while the TMD can be designed using the optimal parameters. The optimized VFD layout plan is that VFDs are placed between the two connections with large relative displacement and relative velocity on higher floors and these two connections with VFDs should be near to the targeted connection. The negative fatigue damage mitigation mainly stems from insufficient lateral support force so that the direct installation of VFDs may result in a negative fatigue damage mitigation effect in the connections with limited lateral support.

저주기 피로를 고려한 3ply 벨로즈형 신축관이음의 내진성능 실험

Pipes can be damaged by strong external forces such as earthquakes. In particular, gas leaks and interruptions to water supply can cause serious secondary damage. This is one of the damage factors caused by earthquakes in urban areas. Bellows-type expansion joints for pipes are flexible and have low rigidity and good adaptability to relatively large deformations. Therefore, bellows-type expansion joints can be applied as seismic separation joints to improve the seismic performance of pipes. In this study, seismic performance considering low cycle fatigue was estimated for bellows-type expansion joints. Monotonic and cyclic loading tests for bending were performed on 80A 3ply bellows- type expansion joints manufactured by laminating three layers of 0.3 mm stainless steel plates. In the cyclic loading test, the multi-step increasing amplitude cyclic loading test to which the displacement history is amplified stepwise was applied and a constant-amplitude cyclic loading test considering various amplitudes was used to estimate the low-cycle fatigue life. In the case of the constant- amplitude cyclic loading tests, low cycle fatigue behavior was observed for 1/4 amplitudes of leakage displacements of monotonic loading tests.

Effect of internal defect on the low-cycle bending fatigue behavior of a single-strand wire rope

• The low-cycle bending fatigue behavior of a defective wire rope is analyzed. • The minimum fatigue life of the wire rope occurs near the defective area. • The internal defect increases the risk of stress yielding of the wire rope. • The internal defect reduces the minimum fatigue life of the wire rope. • An increment in radial position of defect causes a worse performance of the rope. In order to explore the evolution rules and failure mechanism of bending fatigue behavior of a defective single-strand wire rope under cyclic bending load, the influence of average stress and elasto-plasticity on the bending fatigue behavior is considered in this paper. Based on the characteristics of constant amplitude cyclic load, a finite element analysis model of the low-cycle bending fatigue behavior of the single-strand wire rope with an internal defect is established. Then the fatigue lives of the defective rope and non-defective rope are compared, and the influence of the defect’s radial position on the bending fatigue behavior of the rope is discussed. The results show that under the cyclic bending load, the minimum fatigue life of the defective rope in the cross section occurs in the defective area, while that of the non-defective rope lies in the interwire contact area. The defect changes the fatigue life distribution of the single-strand wire rope, and improves the fatigue life locally but reduces the rope’s bearing capacity. Additionally, a larger distance between the defect and neutral layer causes an earlier stress yielding in defective area and makes a greater risk of fatigue failure.

Low-cycle fatigue behaviour and fracture feature of stainless-clad bimetallic steel

The stainless-clad (SC) bimetallic steel that is manufactured by metallurgically bonding stainless steels as cladding metal and conventional mild (CM) steel as substrate metal, is a kind of advanced steel with low cost, high strength and outstanding corrosion-resistant performance. Such advanced steels are especially competitive in the application of engineering structures with demands of high corrosion resistance. Unfortunately, the cyclic behaviour of the SC bimetallic steel is different from that of CM steel or stainless steel, and the research work on the SC bimetallic steels from material level to structural design level for the applications in structural engineering field is very limited. Therefore, this paper aims to investigate the low-cycle fatigue behaviour of the SC bimetallic steel made by hot roll bonding of austenitic stainless steel (S31603) and CM steel (Q355B). The test adopted a constant strain amplitude cyclic loading system with strain ratios of −1 and 0, a strain rate of 0.5%·s−1 and strain amplitudes varying from 1.00% to 2.50%. The fracture feature, cyclic characteristic, stress-strain response and the influence of surface defect and strain rate are analysed herein, and the strain-fatigue life curves are fitted and predicted by adapting the Basquin-Coffin-Manson model and Kuroda model. Research outcomes show that the introduction of cladding steel could significantly improve its ductility and low-cycle fatigue life; the fatigue life of the SC bimetallic steel is generally 30% ~ 60% higher compared with the corresponding CM steel, indicating its excellent low-cycle fatigue behaviour. The low-cycle fatigue life of the two steels could be well predicted by the strain-life relationship with adapted Basquin-Coffin-Manson model and Kuroda model, and the former is indicated superior to the latter in terms of the essential meaning and applicability.

Macro‐meso damage cracking and volumetric dilatancy of fault block‐in‐matrix rocks induced by freeze–thaw‐multistage constant amplitude cyclic (F‐T‐MSCAC) loads

AbstractIn this study, we experimentally investigated the mechanical behaviors of a fault unwelded bimrock exposed to first freeze–thaw weathering and then disturbed stress conditions. The impact of freeze–thaw damage on volumetric deformation, damage propagation, and mesoscopic instability mode was studied. Test results show that the block‐matrix interface cracking easily occurs after freeze–thaw treatment. The strain rate increases with the increase of the freeze–thaw cycle, and an early instability precursor is issued from the evolution of volumetric strain rare. In addition, a coupled evolution model considering the mechanical damage and the freeze–thaw weathering damage was defined, and it was suggested that the model pattern has obviously correlation with the occurrence of freeze–thaw damage. Moreover, posttest CT scanning revealed the influence of freeze–thaw on meso‐cracking and volumetric dilatancy pattern. It is found that the block contact, interlocking, occlusion, and separation contribute a lot to bimrock volumetric expansion.

Failure Rate Model of Materials under Uncertain Constant Amplitude Cyclic Load

Failure rate is an important reliability index of mechanical components. Failure rate is usually used to characterize the degradation rule of material performance under the cyclic load, which is critical to fatigue life prediction as well as reliability assessment of Ti–6Al–2Sn–4Zr–6Mo (Ti-6246) alloy. In order to reveal the probability characteristics of failure rate of Ti-6246 alloy under uncertain cyclic load, the equation of P-S-N curve is studied in this paper. Firstly. The probability density function for fatigue life under uncertain cyclic loading is derived from the probability density function for external stresses. A probabilistic model for the failure rate is then presented based on the basic assumptions. It is assumed that the failure rate and fatigue life of the material depend on the same damage state. Finally, the validity of the proposed model is verified by the Ti-6246 alloy fatigue test. The results show that the fatigue life of Ti-6246 alloy is more affected by material parameters (internal factors) than stress (external factors) under uncertain constant amplitude cyclic loading.