Papers by Keyword: Fretting Fatigue

Abstract: Fretting fatigue is one of the major factors in the design of hydrogen equipment. The effect of internal hydrogen on the fretting fatigue strength of austenitic stainless steels was studied. The internal hydrogen reduced the fretting fatigue strength. The reduction in the fretting fatigue strength became more significant with an increase in the hydrogen content. The reason for this reduction is that the internal hydrogen assisted the crack initiation. When the fretting fatigue test of the hydrogen-charged material was carried out in hydrogen gas, the fretting fatigue strength was the lowest. Internal hydrogen and gaseous hydrogen synergistically induced the reduction in the fretting fatigue strength of the austenitic stainless steels. In the gaseous hydrogen, fretting creates adhesion between contacting surfaces where severe plastic deformation occurs. The internal hydrogen is activated at the adhered part by the plastic deformation which results in further reduction of the crack initiation limit.

Abstract: nfluence of frequency on fretting fatigue damage behavior of Al-Zn-Mg alloy was studied in this paper. Fretting fatigue lives and damage characteristics of Al-Zn-Mg alloy were researched under different frequencies. Macroscopic tests and microscopic analysis were used to study on influence of frequency on fretting fatigue damage behavior of Al-Zn-Mg alloy. Fatigue lives would be greatly reduced by fretting under the experimental conditions in this paper. With frequency increasing, fretting fatigue lives were firstly decreased and then increased (f=9Hz). Fretting scar, which was the important reason for fretting fatigue crack initiation, was caused by embedding debris; eventually, crack initiated at the edge of the fretting scar. Fretting fatigue fracture is a whole process of crack initiation, propagation and final fracture. And final fracture increased with frequency reducing, which was generally occurred near the center of the fracture.

Abstract: The objective of this study is to propose the effective method of reducing the maximum contact pressure at the contact edge of press-fitted shaft by optimizing the location and the size of stress relief groove in hub face. Finite element analysis was performed in order to determine the contact pressure and stress state on a press-fitted assembly and optimization were applied to select optimal size and location of stress relief groove. In order to reduce the cost of optimization design, approximation optimization method is used and the optimum results obtained by Sequential Quadratic Programming and genetic algorithm are compared. Optimized results show that the maximum contact pressure at the contact edge of press-fitted shaft with optimal stress relief groove decreased about 30%. And the both optimization algorithms can effectively reduced the maximum contact pressure at the contact edge of press-fitted shaft.

Abstract: In this paper, Continuum Damage Mechanics (CDM) theory is applied to low cycle and high cycle fatigue problems. Damage evolution laws are derived from thermodynamic principles and the fatigue number of cycles to crack initiation is expressed in terms of the range of applied stresses, triaxiality function and material constants termed as damage parameters. Low cycle fatigue damage evolution law is applied to adhesively bonded single lap joint. Damage parameters as function of stress are extracted from the fatigue tests and the damage model. High cycle fatigue damage model is applied to fretting fatigue test specimens and is integrated within a Finite Element Analysis (FEA) code in order to predict the number of cycles to crack initiation. Fretting fatigue problems involve two types of analyses; namely contact mechanics and damage/fracture mechanics. The high cycle fatigue damage evolution law takes into account the effect of different parameters such as contact geometry, axial stress, normal load and tangential load.

Abstract: The riveting is widely used for fitting together two or more components of structure in the same or different materials. And mechanics characteristic is very complex. The paper work focus on study fretting fatigue crack formation with different friction coefficient and fatigue loading, by analyzing the stress field of upper hole edge and outer boundary of contact area. And comparing with the experimental, founding the risk point of single bolt riveted aluminum components.

Abstract: Ion-beam-assisted deposition (IBAD) was investigated as a potential way to increase the fretting fatigue resistance of Ti-8Al-1Mo-1V alloy at elevated temperature. Three coating systems, hard TiN film, Al film and Cu/Ni multilayer films have been applied on the base material. Coefficients of friction and fretting fatigue lives of the specimens with and without film were compared. The results indicate that the IBAD technique can prepare all films with high bonding strength and excellent lubricating properties. The fretting fatigue life of the Ti-8Al-1Mo-1V alloy with the TiN film was improved by a factor of 2.4 as compared to the uncoated substrate at elevated temperature because of the excellent wear and fatigue resistance and good toughness of the film. The IBAD Al film significantly improved the fretting fatigue resistance of the Ti-8Al-1Mo-1V alloy at elevated temperature for good lubricating property. The fretting fatigue resistance of the Ti-8Al-1Mo-1V alloy was improved by all the Cu/Ni multilayer films. However, the fretting fatigue resistance did not increase monotonically with the modulation period of the films.

Abstract: Ion-beam-assisted deposition (IBAD) was investigated as a potential way to increase the fretting fatigue resistance of Ti-8Al-1Mo-1V alloy at elevated temperature. Three coating systems, hard TiN film with good toughness and soft Al film of low friction and Cu/Ni multilayer films with modulation period thickness of 20~600nm have been applied on the base material. Coefficients of friction and fretting fatigue lives of the specimens with and without film were compared. The film damage was characterized through scanning electron microscopy. The results indicate that the IBAD technique can prepare all films with high bonding strength and excellent lubricating properties. The fretting fatigue life of the Ti-8Al-1Mo-1V alloy with the TiN film was improved by a factor of 2.4 as compared to the uncoated substrate at elevated temperature because of the excellent wear and fatigue resistance and good toughness of the film. Excellent wear resistance and good anti-fatigue properties could be simultaneously obtained by a single hard film to control the fretting fatigue damage. The IBAD Al film significantly improved the fretting fatigue resistance of the Ti-8Al-1Mo-1V alloy at elevated temperature for good lubricating property. The fretting fatigue resistance of the Ti-8Al-1Mo-1V alloy was improved by all the Cu/Ni multilayer films. However, the fretting fatigue resistance did not increase monotonically with the modulation period of the films. Films with a modulation period of 200 nm had the highest fretting fatigue resistance among the multilayer films prepared owing to their high toughness and strength and good lubricating and anti-fatigue action. The fretting fatigue resistance of films with a modulation period of 20 nm was low because of the poor fracture toughness and crack propagation resistance, even though these films had the highest hardness and good fretting wear resistance. Thus, comprehensive properties, including high toughness and strength, must be considered for multilayer films used to improve the fretting fatigue resistance of titanium alloys.

Abstract: Interference-Fit Components, Especially under Rotating Bending Loads, Usually Suffer Fretting Fatigue, which Tremendously Reduces Service Lives of the Components. by Taking Specimens with Different Interference-Fit Parameters for Fatigue Test, their Fretting Fatigue Lives Could Be Obtained. and through Using Finite Element Analysis (FEA) Software ABAQUS, the Ruiz Fretting Damage Parameter K_(x) for each Tested Fatigue Specimen Were Achieved. then, According to the Test Data and the Results of Calculations, Two Fretting-Fatigue Life Prediction Models (model 1：N=c•K^-α, and Model 2：N=λN_{0—m•Kⁿ) )based on the Ruiz Fretting Damage Parameter Were Fitted, and their Ratλionalities and Validities Were Analyzed. at the same Time, the Influences of Interference-Fit Parameters -Interference Value (V), Casing outside Diameter (D), and Casing Length (L), Contact Pressure (p) and Friction Shear Stress (τ) on Fretting Fatigue Life Have Been Analyzed. the Results Showed that the Two Fitalic Textretting Fatigue Life Prediction Models Used in this Paper Were Valid, but, in Contrast, the Second One Was More Accurate and Rational; and that Fretting Fatigue Life (N) Decreased as V, D, L, P or τ Increasing.}

Abstract: Fretting fatigue cracks always initial at the tralling of contact region, because the stresses in the vicinity of the contact zone exhibit steep gradients. A fracture mechanics approach is usually used to estimate fretting fatigue propagation life. In this paper, extended finite element method combined with fracture mechanics is used to study fretting crack propagation behaviors. The computation results reveal that fretting crack nucleation is mainly decided by fretting, and the cycle bulk stress is the main reason for crack propagation. Also the X-FEM exhibits merits in fretting fatigue problem.

Abstract: Fretting fatigue becomes a typical failure mode for engine cylinder block caused by the increasing of the gas pressure and rotating speed, but the mechanism of fretting fatigue under diesel engine load condition hasn’t been systematic studied. In this paper, the fretting behaviors are mainly discussed by using fretting friction work parameter W and crack initiation location parameter G.