Fatigue Life Of Steel Wires Research Articles

Fatigue life prediction of corroded hangers with parallel steel wire in a network arch bridge under vehicle-bridge interaction based on a novel noniterative simplified method

Fatigue damage is a main concern during the life-cycle maintenance of bridges with corroded hangers under vehicle-bridge interaction (VBI). In this study, a novel noniterative simplified method for VBI is proposed to analyze the responses of hangers in a network arch bridge, considering the effects of vehicle types, driving lanes, and road surface roughness. Furthermore, the fatigue life of corroded hangers is investigated, considering the actual traffic flow and uneven distribution of stress in the hanger’s cross-section. The results show that longitudinal and transverse bending moments of the hanger significantly affect the stress of steel wires in one hanger but have limited influence on stress amplitudes. The fatigue lives of steel wires are considerably reduced when subjected to both uniform and pitting corrosion. The fatigue life of steel wires is reduced under deteriorating road surface conditions. Moreover, as the fatigue life of steel wires in the hangers declines, the variations in fatigue life among individual steel wires within a single hanger gradually decrease. Consequently, this trend leads to a heightened likelihood of continuous wire breakage.

Fatigue Behavior and Fracture Surface Analysis of Corroded High-Strength Bridge Cable Wires.

Bridge cable wires suffer from alternating stress and environmental erosion, leading to premature failure prior to its design life. This paper investigates the fatigue and mechanical behaviors of corroded bridge cable wires with a zinc-aluminum (Zn-Al) alloy coating. Based on the salt spray corrosion test and microstructure analysis, the anti-corrosion resistance and corrosion appearance characteristics of the Zn-Al alloy coating and galvanized coating were investigated. The Zn-Al alloy coating was superior in resistance to corrosion fatigue for the improvement in toughness and the generation of anti-corrosion Zn-Al and Fe-Zn-Al phases. Equations of the accelerated corrosion depth of the steel wires had been regressed to roughly estimate the corrosion life of the Zn-Al alloy coating, which can reach 29.1 years with a thickness of 70 μm. The fatigue and mechanical properties of the bare wires after the salt spray test were further studied based on tensile tests and fatigue tests. The fatigue properties of the bridge cable wire would decrease with the corrosion degree due to the deterioration and embrittlement of materials, where ductility characterized by the elongation rate was the most affected. Fracture surfaces of the wires were captured and analyzed based on a method for recognizing graphical contours. Insufficient fatigue life may occur in the steel wires after corrosion and increase with the degree of corrosion. The pit depth logarithmically weakened the fatigue life of steel wires for the weakening of fatigue toughness and the bearing area. The flat fracture was more common with a single fatigue source, while multiple fatigue sources led to step-like fractures for the generation of multiple dispersed crack propagation regions. Corrosion fatigue was more sensitive to the existence of fatigue sources than the reduction. Multiple initiation sources significantly reduced the fatigue life due to the cracking facilitation of the joint effect of multiple pits. The electrochemical reactions of corrosion can lead to material embrittlement and a reducing effect on the fracture toughness of the steel wires.

Fatigue of Bridge Steel Wire: A Corrosion Pit Evolution Model under the Effects of Wind and Vehicles

To investigate the damage evolution behavior of corroded steel wires under the influence of alternating loads, a damage evolution model for steel wires based on the theory of continuous damage mechanics was established. The damage evolution process at corrosion pits was simulated by using the element birth and death technique in ANSYS 2020R2. Then, a certain cable-stayed bridge was chosen as the research subject, the stress–time data of the sling were computed using a traffic–bridge–wind simulation analysis model, and the influence of corrosion pit distribution on the mechanical properties and fatigue life of wires under an alternating load was discussed. The results show that, in comparison to single-pitted steel wires, double-pits distributed circumferentially across the cross-section of the steel wires lead to more severe stress concentration, accelerating the damage evolution process and significantly reducing the fatigue life of the steel wires. Conversely, the stress concentration caused by double pits distributed along the longitudinal direction of steel wire is similar to that caused by single pits, and it will be even weaker than that caused by single pits with the change in the relative distance of the double pits. Based on the calculation results of the damage evolution model of steel wire, it was found that the corrosion pit crack nucleation life of steel wire under alternating load accounts for nearly 80% of the fatigue life of steel wire, and different corrosion pit distribution modes will significantly affect the fatigue life of steel wire.

Numerical prediction of fretting fatigue life for cold-drawn eutectoid carbon steel wire using continuum damage mechanics and effective slip amplitude

The effective and safe use of wire ropes in various applications relies on a comprehensive understanding of the fretting fatigue phenomena that occur between internal wires. Estimating the fatigue life of steel wires subjected to fretting loading through numerical simulation techniques requires significant computational capacity and time, especially when considering wear process. In this study, a more straightforward and practical approach for predicting fretting fatigue life is developed using Continuum Damage Mechanics (CDM). This involves introducing damage stresses that account for relative slip amplitude and modified maximum principal stresses into the CDM framework. Additionally, the Effective Slip Amplitude (ESA) approach is utilized, incorporating relative slip amplitude and Walker effective stress, to evaluate fretting fatigue lifetime. A finite element model is replicated to obtain the relative slippages and stresses at the contact region. The accuracy of the CDM approach and the ESA approach is individually validated and verified by comparing them to experimental data and simulation results including the wear process from published literature. The results indicate that the CDM and ESA approaches, which combine relative slip amplitude and Walker effective stress, effectively predict the fretting fatigue lifetime of cold-drawn eutectoid carbon steel wires.

Experimental and numerical study of the fatigue properties of stress-corroded steel wires for bridge cables

In this paper, the fatigue tests of stress-corroded steel wires were carried out to investigate the effects of corrosion age, stress level, stress range on the failure mode, fatigue life and S-N curve of steel wires. Then, the fatigue fracture and crack growth rate of steel wires with different corrosion degrees were analyzed by SEM scanning, revealing the crack initiation and propagation mechanism of corroded steel wires. Finally, a numerical analyzing method for the fatigue life of steel wires considering the corrosion surface was proposed, and the relationship between the surface stress distribution and fatigue life was studied. The results shows that the fatigue life of steel wires decreased gradually with the increase of corrosion degree. When the corrosion degree was 5.0%, 10% and 20%, the fatigue life of steel wires decreased by 32.67%, 48% and 67.84%, respectively. The influence of corrosion degree on the fatigue life of steel wire was first sensitive and then insensitive. Meanwhile, compared with the unstressed corrosion state, the fatigue life of stress-corroded steel wires decreased by a maximum of 56.45%. In addition, stress corrosion affected the crack initiation location and shortened the crack propagation depth. The higher corrosion depth and the sharp surface were more likely to be the fatigue crack source. With the increase of corrosion degree, the striation spacing and crack growth rate of fatigue fracture increased, and the proportion of crack initiation and propagation zone decreased from 45% of the diameter to 28% of the diameter of the cable. Finally, the proposed numerical analysis method considering the real corroded surface can effectively reveal the fatigue failure mechanism and evaluate the residual fatigue life of corroded steel wires.

Study on Fatigue Performance of 2200 MPa High-Strength Wire of Main Cables Based on FE-SAFE

In order to estimate the fatigue life of 2200 MPa high-strength steel wire for main cables at the outlet of the cable saddle, a fatigue loading test of a single steel wire was designed, and the value of the friction coefficient in finite element simulation and the scale factor in fatigue life analysis were determined. The fatigue life of the steel wire was analyzed by two-stage modelling. The results showed that the fatigue life of steel wire can be simulated effectively when the friction coefficient is 0.21 and the scale factor is 1.15. The fatigue life of 2200 MPa main cable wire at the saddle outlet is 4.78 million loading cycles. The research results laid a foundation for practical engineering application of high-strength steel wire for 2200 MPa main cables.

Evaluation of Flexible Central Buckles on Short Suspenders’ Corrosion Fatigue Degradation on a Suspension Bridge under Traffic Load

Suspenders are the crucial load-bearing components of long-span suspension bridges, and are sensitive to the repetitive vibrations caused by traffic load. The degradation of suspender steel wire is a typical corrosion fatigue process. Although the high-strength steel wire is protected by a coating and protection system, the suspender is still a fragile component that needs to be replaced many times in the service life of the bridge. Flexible central buckles, which may improve the wind resistance of bridges, are used as a vibration control measure in suspension bridges and also have an influence on the corrosion fatigue life of suspenders under traffic load. This study established a corrosion fatigue degradation model of high-strength steel wire based on the Forman crack development model and explored the influence of flexible central buckles on the corrosion fatigue life of suspenders under traffic flow. The fatigue life of short suspenders without buckles and those with different numbers of buckles was analyzed. The results indicate that the bending stress of short suspenders is remarkably greater than that of long suspenders, whereas the corrosion fatigue life of steel wires is lower due to the large bending stress. Bending stress is the crucial factor affecting the corrosion fatigue life of steel wires. Without flexible central buckles, short suspenders may have fatigue lives lower than the design value. The utilization of flexible central buckles can reduce the peak value and equivalent stress of bending stress, and the improved stress state of the short suspender considerably extends the corrosion fatigue life of steel wires under traffic flow. However, when the number of central buckles exceeds two, the increase in number does not improve the service life of steel wire.

Fatigue life evaluation of high-strength steel wires with multiple corrosion pits based on the TCD

The stay cable composed of high-strength steel wires is susceptible to external corrosion during service, and multiple pitting damage will occur on the surface of steel wires. For the sake of simplifying the pitting morphology, this paper used artificial notches to simulate corrosion pits, and the fatigue properties of high-strength steel wires with multiple notches were systematically studied. First, fatigue tests of steel wires with multiple pits were performed, and the finite element models were established by ABAQUS software. The fitting equations related to stress concentration factor (SCF) and corrosion pit parameters were obtained. Subsequently, the fatigue life of corroded high-strength steel wires was predicted by the Point method (PM) and the Line method (LM) originated from the Theory of Critical Distances (TCD). Finally, the prediction results compared with the experimental results. The results show that the fatigue life of steel wires with a single pit is mainly related to the pit depth-to-length ratio. The fatigue life of steel wires with double pits located on the same side mainly depends on deeper pits, but it slightly decreases as the increase of the depth of shallow pits. The effect of the spacing of double pits is very small. The fatigue life of steel wires with double pits in the circumferential direction decreases as the angle between the double pits increases. The reliability of the TCD for fatigue evaluation of multi-notch components is verified.

Fatigue life evaluation model for high-strength steel wire considering different levels of corrosion

This article studies the quantitative influences of corrosion on the fatigue life of high-strength steel wires, considering a wide variation in the degree of corrosion. A multiparameter Weibull model for corrosion-stress-life (C-S-N) is proposed, and the Goodman relation is employed to deal with the dependences of stress ranges on positive stress ratios. Fatigue data are collected from the literature for three groups with different ultimate tensile strengths and the degree of corrosion ranging from 0.18% to 18.67%. This data is then used to estimate the parameters of the Weibull model; subsequently, quantitative influences of corrosion on fatigue life for steel wires with a wide range in the degree of corrosion are illustrated and discussed. The results indicate that the influence of ultimate tensile strengths on fatigue life for corroded steel wire can be ignored, because corrosion causes crack nucleation faster, especially at lower stress ranges. The fatigue life decreases sharply as the corrosion increases, and reduction is much pronounced under a lower stress range. Negative correlation of fatigue life and corrosion increases as the stress range decreases, which further confirms that corrosion has a higher influence at lower stress ranges. The proposed model can provide quantitative evaluation on the fatigue life of steel wires at specified survival probabilities, considering a wide range in the degree of corrosion; these results can be used by engineering designers to ensure the safety for cable-supported bridges during their lifetime.

Experimental study and residual fatigue life assessment of corroded high-tensile steel wires using 3D scanning technology

Fatigue damage of bridge suspender is a serious problem under long-term environmental erosion and repeated vehicle loads. This paper quantifies the effects of corrosion on the residual fatigue life of steel wires in bridge suspender. A predictive model was proposed to estimate the fatigue life of corroded steel wires based on the equivalent initial flaw size method, in which both corrosion growth stage and fatigue crack propagation stage were considered. The pitting corrosion-induced stress concentration was incorporated into the stress intensity factor model. The theoretical residual fatigue life can be obtained by integrating the fatigue crack growth model from the equivalent initial crack size to a critical crack length. The effects of corrosion on the fatigue performance of steel wires with various corrosion degrees were investigated by fatigue loading tests. The fracture morphology of the steel wires after fatigue was observed using scanning electron microscopy. The relationships between corrosion degrees and fatigue lives of the steel wires were provided. The surface morphology of corroded steel wire was scanned by 3D scanning technology, and a three-dimension model was established. A finite element model of corroded steel wires was established after the scanning model was processed by the Geomagic software. Following that, the relationship between stress concentration factor and corrosion degree was analyzed. A fatigue life prediction method based on the equivalent initial crack size was verified by the experimental observation of various corroded steel wires and the data in open literature.

Experimental study on the fatigue behavior of corroded steel wire

To investigate the fatigue behavior of corroded steel wire, the fatigue tests of 102 natural corrosion steel wires in service for 23 years and 84 artificial prefabricated steel wires with corrosion pits have been carried out. The influences of corrosion degree and pit parameters on the fatigue life are discussed. The relationships between fatigue fracture, S-N curve and corrosion degree are studied, and the expression of S-N curves of corroded steel wire is established. The results show that the fatigue fracture is mainly related to the corrosion degree and can be divided into four kinds, such as conical shape, oblique shape, cup-shaped and stepped shape. The fatigue life of steel wires without corrosion damage in service is still significantly lower than that of the new ones at the low stress amplitude, and the degradation ratio is as high as 23%. The fatigue life degradation of steel wire with prefabricated pits is as high as 95% compared with that without corrosion under low stress amplitude. Therefore, the lower the stress amplitude, the higher the corrosion degree, and the more significant the degradation of fatigue life is. The low stress amplitude makes the fatigue crack propagation of steel wires fully, and there are multiple fatigue crack source regions and some of them appear multiple cracks. In addition, the influences of corrosion time and pit depth on the fatigue life are higher than pit width.

Effects of characteristic parameters of corrosion pits on the fatigue life of the steel wires

To study the influence of corrosion pits on fatigue life of high-strength steel wire, 69 cable steel wires with different characteristic parameters of pits were obtained by manual prefabrication. The effects of pit depth, width, location and stress amplitude on the fatigue life of steel wires were investigated through the fatigue test. Then, the prediction model of fatigue life of steel wire with corrosion pits was established. Finally, 236 finite element models (FEM) of steel wire with corrosion pits were established by the software ANSYS and nCode designLife, and the SN curves of steel wires with different sizes of pit and stress ratios were also analyzed. The results showed that the fatigue life of steel wire decreased significantly when the depth of pit was in the range of 0.2–0.6 mm, with a maximum reduction of 99.25%. The slight change of stress amplitude would result in the fatigue life by several times or even ten times. The superposition effect of pits would slightly increase the fatigue life of steel wire. In addition, when the stress ratio increased from −1 to 0.44, the SN curve of steel wire with 0.16 of depth-width ratio of pits would move down more than twice than that of steel wire with 0.75 of depth-width ratio of pits. For finite life design, the fatigue life of steel wire changed from high cycle fatigue to low cycle fatigue with the increase of depth-width ratio of pits. When the depth-width ratio was >1, the corresponding stress amplitude was not affected by the pit sizes under the same fatigue life. The effect of stress ratio on wide-shallow pits was greater than that on deep-narrow pits.

Finite Element Modeling of Fatigue Life of Steel Wire

In this work, bending fatigue life of steel wire has been studied using finite element modeling by ANSYS program. To verify the finite element results; a fatigue setup was designed and constructed, and the wire was tested using this setup. The results showed that the fatigue life of the wire that bent over the smaller bending diameter has the lower fatigue life, while increasing the bending diameter has a great effect on increasing the fatigue life of steel wire. The finite element results were almost near the experimental results with an accepted percent of deviation. The other values such as, equivalent (Von-Mises) stress, elastic strain, plastic strain, total strain, and the total deformation were estimated using finite element modeling. The Von-Mises parameters results showed that the wire bent over the bigger bending diameter has the lower values in which affect its fatigue life in a positive way.

Simulation of Damage Evolution and Study of Multi-Fatigue Source Fracture of Steel Wire in Bridge Cables Under the Action of Pre-Corrosion and Fatigue

A numerical simulation method for the damage evolution of high-strength steel wire in a bridge cable under the action of pre-corrosion and fatigue is presented in this paper. Based on pitting accelerated crack nucleation theory in combination with continuum mechanics, cellular automata technology (CA) and finite element (FE) analysis, the damage evolution process of steel wire under pre-corrosion and fatigue is simulated. This method automatically generates a high-strength steel wire model with initial random pitting defects, and on the basis of this model, the fatigue damage evolution process is simulated; thus, the fatigue life and fatigue performance of the corroded steel wire can be evaluated. A comparison of the numerical simulation results with the experimental results shows that this method has strong reliability and practicability in predicting the fatigue life of corroded steel wire and simulating the damage evolution process. Based on the method proposed in this paper, the fatigue life of steel wires with different degrees of corrosion under the action of different stress levels is predicted. The results show that as the degree of corrosion increases, the fatigue properties of steel wire gradually decrease, and the influence of existing pitting corrosion on fatigue life is far greater than that on mass loss.Stress concentration is the main cause of fatigue life of corroded steel wire in advance attenuation. In addition, the fracture process of steel wire with multi-fatigue sources and the effect of the number and distribution of pits on the fatigue life of steel wire are studied. The results show that, compared with a stepped pitting distribution, a planar pitting distribution has a greater impact on the damage evolution process. The fatigue life of steel wire is positively correlated with the number of pits and the angle and distance between pits.

Fatigue crack growth of cable steel wires in a suspension bridge: Multiscaling and mesoscopic fracture mechanics

Intrinsically, fatigue failure problem is a typical multiscale problem because a fatigue failure process deals with the fatigue crack growth from microscale to macroscale that passes two different scales. Both the microscopic and macroscopic effects in geometry and material property would affect the fatigue behaviors of structural components. Classical continuum mechanics has inability to treat such a multiscale problem since it excludes the scale effect from the beginning by introducing the continuity and homogeneity assumptions which blot out the discontinuity and inhomogeneity of materials at the microscopic scale. The main obstacle here is the link between the microscopic and macroscopic scale. It has to divide a continuous fatigue process into two parts which are analyzed respectively by different approaches. The first is so called as the fatigue crack initiation period and the second as the fatigue crack propagation period. Now the problem can be solved by application of the mesoscopic fracture mechanics theories developed in the recent years which focus on the link between different scales such as nano-, micro- and macro-scale. On the physical background of the problem, a restraining stress zone that can describe the material damaging process from micro to macro is then introduced and a macro/micro dual scale edge crack model is thus established. The expression of the macro/micro dual scale strain energy density factor is obtained which serves as a governing quantity for the fatigue crack growth. A multiscaling formulation for the fatigue crack growth is systematically developed. This is a main contribution to the fundamental theories for fatigue problem in this work. There prevail three basic parameters μ ∗, σ ∗ and d ∗ in the proposed approach. They can take both the microscopic and macroscopic factors in geometry and material property into account. Note that μ ∗, σ ∗ and d ∗ stand respectively for the ratio of microscopic to macroscopic shear modulus, the ratio of restraining stress to applied stress and the ratio of microvoid size ahead of crack tip to the characteristic length of material microstructure. To illustrate the proposed multiscale approach, Hangzhou Jiangdong Bridge is selected to perform the numerical computations. The bridge locates at Hangzhou, the capital of Zhejiang Province of China. It is a self-anchored suspension bridge on the Qiantang River. The cables are made of 109 parallel steel wires in the diameter of 7 mm. Cable forces are calculated by finite element method in the service period with and without traffic load. Two parameters α and β are introduced to account for the additional tightening and loosening effects of cables in two different ways. The fatigue crack growth rate coefficient C 0 is determined from the fatigue experimental result. It can be concluded from numerical results that the size of initial microscopic defects is a dominant factor for the fatigue life of steel wires. In general, the tightening effect of cables would decrease the fatigue life while the loosening effect would impede the fatigue crack growth. However, the result can be reversed in some particular conditions. Moreover, the different evolution modes of three basic parameters μ ∗, σ ∗ and d ∗ actually have the different influences on the fatigue crack growth behavior of steel wires. Finally the methodology developed in this work can apply to all cracking-induced failure problems of polycrystal materials, not only fatigue, but also creep rupture and cracking under both static and dynamic load and so on.

FATIGUE PERFORMANCE OF STEEL WIRES WITH FRETTING WORN NOTCH

A series of experiments on the fretting wear of steel wires are performed on self-made fretting wear test rig. The worn wires after fretting tests are put into fatigue test at different stress ratio and different stress amplitude on the servo-fatigue test machine. The research results demonstrate that the fretting wear depth of the steel wires increase with the increasing fretting cycles and contact loads. The fretting worn notch is the source of crack initiation because of stress concentration, which decrease the fatigue life of steel wires. The fatigue life of the steel wires with fretted damage is inverse proportional to the wear depth. The fretting fatigue mechanisms are analyzed through SEM morphologies of fracture sections, which indicate that fatigue are divided into crack initiation, crack propagation and crack break corresponding to different fatigue phases.