Showing papers on "Vibration fatigue published in 2008"
TL;DR: In this paper, the experimental research and modeling of fiber reinforced polymer composite materials subjected to variable amplitude fatigue is reviewed and compared by applying them to four material systems for which extensive fatigue data was available.
182 citations
TL;DR: In this article, a method to characterize fatigue resistance of the fine portion of the asphalt mixture using the dynamic mechanical analyzer (DMA) was presented, and three mixtures were characterized in controlled-strain and controlled-stress modes of loading.
Abstract: Fatigue cracking is one of the primary distresses in asphalt pavements. This study presents a method to characterize fatigue resistance of the fine portion of the asphalt mixture using the dynamic mechanical analyzer (DMA). Three mixtures were characterized in controlled-strain and controlled-stress modes of loading. The new method has several advantages as it requires reasonable testing time, uses a small amount of material, utilizes fundamental properties of the mixture, and is able to unify the results from controlled-strain and controlled-stress modes of loading. The unified method relies on identifying the different mechanisms of energy dissipation during fatigue cracking that are related to changes in the phase angle, changes in stiffness, and development of permanent deformation during the fatigue damage process. Two fatigue damage parameters are derived in this paper. The parameters are shown to have reasonable and lower coefficients of variation than conventional parameters such as number of load...
127 citations
TL;DR: In this paper, the thermal effects associated with the propagation of a fatigue crack in a gigacycle fatigue regime were studied. But the authors focused on the time evolution of the temperature fields in specimens and showed a good correlation with experiment and provided experimental proof that the propagation stage constitutes a small part of the lifetime of the specimen.
125 citations
TL;DR: A methodology that combines the vibration failure test, finite element analysis (FEA), and theoretical formulation for the calculation of the electronic component’s fatigue life under vibration loading is developed and it is believed that the methodology is effective in predicting component's life and may be applied further in improving the reliability of electronic systems.
90 citations
TL;DR: In this paper, a procedure for fatigue analysis of a general wide-band stationary Gaussian process is developed in the frequency domain using a trimodal spectral formulation, based on a generalization of the principle proposed by Jiao and Moan for predicting bimodal fatigue damage.
90 citations
TL;DR: In this paper, the Modified Wohler Curve Method (MWCM) is applied in conjunction with the Theory of Critical Distance (TCD) to estimate fatigue lifetime of mechanical components subjected to multiaxial cyclic loading and experiencing stress concentration phenomena.
Abstract: This paper is concerned with the use of the Modified Wohler Curve Method (MWCM) applied in conjunction with the Theory of Critical Distances (TCD) to estimate fatigue lifetime of mechanical components subjected to multiaxial cyclic loading and experiencing stress concentration phenomena. In more detail, our engineering approach takes as its starting point the idea that accurate estimates can be obtained by simply assuming that the value of the critical length, LM, to be used to evaluate fatigue damage in the medium–cycle multiaxial fatigue regime is a function of the number of cycles to failure, Nf. In other words, the MWCM, which is a bi-parametrical critical plane approach, is suggested here to be applied by directly post-processing the linear-elastic stress state damaging a material point whose distance from the notch tip increases as Nf decreases. According to the main feature of the TCD, the above LM versus Nf relationship is assumed to be a material property to be determined experimentally: such an hypothesis results in a great simplification of the fatigue assessment problem because, for a given material, the same critical length can be used to estimate fatigue damage independent of the considered geometrical feature. The accuracy of the devised approach was checked by analysing about 150 experimental results we generated by testing V-notched cylindrical samples made of a commercial cold-rolled low-carbon steel. The above specimens were tested under in-phase and out-of-phase combined tension and torsion, considering the damaging effect of superimposed static stresses as well. Moreover, in order to better check its accuracy in assessing notched components subjected to complex loading paths, our method was also applied to several data sets taken from the literature. This extensive validation exercise allowed us to prove that the MWCM applied along with the TCD is successful in estimating medium-cycle multiaxial fatigue damage (Nf values in the range 104–106), resulting in predictions falling within the widest scatter band between the two used to calibrate the method itself. Such a high accuracy level is very promising, especially in light of the fact that the proposed approach predicts multiaxial fatigue lifetime by post-processing the linear elastic stress fields in the fatigue process zone: this makes our method suitable for being used to assess real components by performing the stress analysis through simple linear-elastic FE models.
84 citations
TL;DR: In this paper, the authors present a system for treating of the actual measured data for load histories, which consists of two steps: stress analysis and fatigue damage prediction, which is conducted for the component in question to obtain detailed stress-strain responses.
Abstract: This paper presents a system for treating of the actual measured data for load histories. The approach consists of two steps: stress analysis and fatigue damage prediction. Finite element analysis is conducted for the component in question to obtain detailed stress-strain responses. A significant number of failures occurred in a brake end beam which led to economic losses and disruption of service. The cracks appeared to be fatigue cracks caused by the dynamic load produced in the loaded bogie frame. Strain gauge data were analyzed, and fatigue cycles were calculated from this data. Rainflow cycle counting was used to estimate cumulative damage of the end beam under in-service loading conditions. The fatigue life calculated with the rainflow cycle counting method, the P-S-N curve, and the modified Miner’s rule agreed well with actual fatigue life within an error range of 2.7%~31%.
82 citations
TL;DR: In this paper, the effects of variable amplitude loading conditions on the fatigue lives of multiaxial rubber specimens were investigated and compared with other approaches, including the applicability of Miner's linear damage rule for predicting fatigue lives.
82 citations
TL;DR: In this article, a continuum approach to modeling of high-cycle fatigue is proposed, based on the concepts of a moving endurance surface in the stress space and an evolving damage variable.
75 citations
TL;DR: In this article, the problem of estimating the material fatigue properties for assessing real mechanical components was addressed, and some practical rules were proposed to estimate the fully reversed plain fatigue limit, Δσ 0, using the material tensile stress.
Abstract: This paper addresses the problem of estimating the material fatigue properties for assessing real mechanical components. Initially, some practical rules are proposed to estimate the fully reversed plain fatigue limit, Δσ 0 , using the material tensile stress. These rules are obtained by subdividing materials into five different groups: carbon steels, low-alloy steels, high-alloy steels, aluminium alloys and cast irons. Subsequently, using a large database of fatigue data found in the literature, it is demonstrated that the fully reversed torsional plain fatigue limit can be directly estimated from the fully reversed uniaxial plain fatigue limit by simply using Von Mises' formula. Finally, some empirical equations are proposed to estimate El Haddad's short crack constant, a 0 . These equations are based on the assumption that this material property can be derived from the plain fatigue limit determined at a given load ratio, R. Since the a 0 values depend on the load ratio, so a 0 versus Δσ 0 relationships can directly account for the R influence. The aim of this paper is to provide engineers engaged in assessing real structural components with empirical rules to estimate the material fatigue properties. All these pieces of information are needed to apply the most modern methods suitable for assessing components weakened by any kind of geometrical feature and subjected to any kind of fatigue loading.
74 citations
TL;DR: In this article, a novel stress invariant based approach was proposed for estimating fatigue damage in the presence of complex multiaxial fatigue loadings by studying the components of the deviator path projected along the axes of a convenient frame of reference.
TL;DR: In this paper, the microstructural development of SnAgCu solder joints under different loading conditions (isothermal storage, thermal cycling and vibration) was investigated with respect to grain growth and grain refinement, crack formation and crack growth.
Abstract: Purpose – The purpose of this paper is to investigate the microstructural development of SnAgCu solder joints under different loading conditions (isothermal storage, thermal cycling and vibration).Design/methodology/approach – The observed microstructural changes have been studied with respect to grain growth and grain refinement, crack formation and crack growth. The growth kinetics of the intermetallic phases encountered as particles in the bulk as well as a reaction layer on the copper pad, were studied in the temperature range of 125‐175°C.Findings – Dynamic recrystallisation of the tin matrix leads to a change in the diffusion controlled growth mechanism, which causes an increase of the particle growth rate compared to isothermal storage. Thus, these grain boundaries are separated forcibly by crack growth during thermal cycling. This stress causes intergranular cracks while vibration stress induces transgranular cracks.Originality/value – The paper adds insight into microstructural changes of lead‐fr...
15 Jun 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a finite element analysis of rubber component was performed based on a hyper-elastic material model determined from material test and the Green-Lagrange strain at the critical location determined from the finite element method was used to evaluate the fatigue damage parameter of the natural rubber.
Abstract: Fatigue life prediction and evaluation are very important in design procedure to assure the safety and reliability of the rubber components. Fatigue lifetime prediction methodology of the rubber component was proposed by incorporating the finite element analysis and fatigue damage parameter from fatigue test. Finite element analysis of rubber component was performed based on a hyper-elastic material model determined from material test. The Green–Lagrange strain at the critical location determined from the finite element method was used to evaluate the fatigue damage parameter of the natural rubber. Fatigue life of rubber components was predicted by using the fatigue damage parameter at the critical location. Predicted fatigue life of the rubber component agreed fairly well with the experimental fatigue lives.
TL;DR: In this article, an acceleration factor is defined that indicates how much faster plastic strain is accumulated by a cyclic signal compared to its static mean stress, and analytical solutions of the acceleration factor are presented for triangular and square waves.
Abstract: A method is presented that allows fatigue life predictions on the basis of creep life data. The approach is based on the assumption that the time-dependent failure of polymers is determined by the intrinsic strain softening that is initiated when a critical threshold value of the plastic strain is surpassed. To facilitate fatigue predictions, an acceleration factor is defined that indicates how much faster plastic strain is accumulated by a cyclic signal compared to its static mean stress. Analytical solutions of the acceleration factor are presented for triangular and square waves, which predict that only the stress amplitude of the cyclic signal and the material's stress dependency affect fatigue life, whereas frequency plays no role. Verification using several glassy and semicrystalline polymers demonstrates that this method yields accurate quantitative lifetime predictions not only for polymers that exhibit ductile failure but also for those that display brittle fracture, provided that fracture is preceded by (localized) plastic flow.
TL;DR: A general methodology for fatigue reliability degradation of railroad wheels is proposed in this paper and both fatigue crack initiation and crack propagation life are included in the proposed methodology using previously developed multiaxial fatigue models by the same authors.
TL;DR: In this paper, a new equivalent stress that can be used as a uniaxial stress time history suitable for the application of damage evaluation methods has been developed, which is not accepted by the majority of researchers because a definition in agreement with experimental results has not been found yet.
TL;DR: In this paper, an engineering method based on linear elastic finite element (FE) analyses oriented to fatigue strength assessment of fillet-welded joints made of steel or aluminium alloys and subjected to mode I loading in the weld toe region where fatigue cracks nucleate is presented.
Abstract: The aim of this work is to present an engineering method based on linear elastic finite element (FE) analyses oriented to fatigue strength assessments of fillet-welded joints made of steel or aluminium alloys and subjected to mode I loading in the weld toe region where fatigue cracks nucleate. The proposed approach combines the robustness of the notch stress intensity factor approach with the simplicity of the so-called ‘peak stress method’. Fatigue strength assessments are performed on the basis of (i) a well-defined elastic peak stress evaluated by FE analyses at the crack initiation point (design stress) and (ii) a unified scatter band (design fatigue curve) dependent on the class of material, i.e. structural steel or aluminium alloys. The elastic peak stress is calculated by using rather coarse meshes with a fixed FE size. A simple rule to calculate the elastic peak stress is also provided if a FE size different from that used in the present work is adopted. The method can be applied to joints having complex geometry by adopting a two-step analysis procedure that involves standard finite element (FE) models like those usually adopted in an industrial context. The proposed approach is validated against a number of fatigue data published in the literature.
TL;DR: In this paper, a framework using both the elastic shakedown concept and the weakest link theory to account for loading mode, loading path and data scatter in high cycle fatigue is presented by means of observations conducted on a mild steel submitted to purely reversed torsion and push pull fatigue tests.
TL;DR: In this article, a probabilistic method for the simulation of fatigue crack growth from crack-like defects in the combined operating and residual stress fields of an arbitrary component is presented.
TL;DR: In this paper, a model of a deformation process under the conditions of mechanical and thermal interactions has been developed, which enables extensive investigations of the influence of various types of relations between fatigue process parameters on changes of the uniaxial stress-strain characteristics.
TL;DR: In this paper, an effective stress is calculated by solving a second-order differential equation over all the component (the implicit gradient approach) independently of its geometric shape, which is obtained by assuming the isotropic linear elastic constitutive law for the material and the maximum principal stress as equivalent stress.
TL;DR: In this paper, the authors investigated the high cycle fatigue behavior of metals in the case of multiaxial loading where the stresses are of different frequencies and compared the results from tests where the shear and normal stress are of the same frequency and in-phase.
TL;DR: In this paper, a unique set of crack growth data has been generated for tubular test pieces in 316L(N) stainless steel subjected to cyclic thermal loads in a specially designed rig, by accurate modelling of the thermal loads and nonlinear material behaviour using the finite element method, it was possible to reliably estimate the number of cycles to initiation, using standard isothermal fatigue life curves.
TL;DR: In this paper, the probability of failure of concrete beams under fatigue loading is computed using a modified fatigue law by considering different parameters responsible for fatigue failure as randomly distributed, and the sensitivity of different parameters involved in fatigue process pertaining to failure is also studied using stochastic sensitivity analysis.
18 May 2008
TL;DR: In this article, two techniques, fracture mechanics with strain intensity factor (DeltaK epsiv) and electrical-thermal-structural coupled analysis, were developed to estimate the fatigue life of aluminum bonding wires.
Abstract: Two techniques, one for estimating fatigue life of aluminum bonding wires and one for estimating fatigue life of solders under repeated thermal load, were developed. In one method, fracture mechanics with strain intensity factor (DeltaK epsiv) is used to estimate the fatigue life of aluminum bonding wires. In the other method, "electrical-thermal-structural coupled analysis" is used to estimate fatigue life of solders. The simulated crack propagation in aluminum bonding wires agrees well with the experimentally measured propagation. Moreover, the simulations show that fatigue life of aluminum bonding wires has a lower fatigue limit at a temperature-cycling range of 30degC.
TL;DR: In this article, an analysis and testing process of the prototype of a helicopter's mission system sensor (MSS)-cowling assembly is described, which involves accelerated life testing (ALT) establishes an appropriate methodology for such integration projects.
TL;DR: In this paper, a non-local area approach was proposed to reduce non-uniform distribution of shear and normal stresses on the critical plane to the uniform ones. But the reduced stress histories were introduced to the algorithm of fatigue life calculation and verified by fatigue tests on the hourglass shaped specimens subjected to the combined proportional or non-proportional bending and torsion.
TL;DR: In this article, a multiscale reduction of the stress distribution along the potential crack initiation plane is performed by averaging process for shear and normal stresses over two critical areas (multiscale concept).
TL;DR: In this paper, a finite element based fatigue life prediction of cylinder head for a two-stroke free piston linear engine subjected to variable amplitude loading, applicable to electric power generation, is described.
Abstract: This study describes the finite element based fatigue life prediction of cylinder head for a two-stroke free piston linear engine subjected to variable amplitude loading, applicable to electric power generation. A set of aluminum alloys, cast iron and forged steel for cylinder head are considered in this study. The finite element modeling and analysis were performed utilizing the finite element analysis codes. The fatigue life analysis was carried out using finite element based fatigue analysis commercial codes. Fatigue stress-life approach was used when the piston is subjected to variable amplitude at different loading conditions. The effects of mean stress and sensitivity analysis on fatigue life are discussed. From the results, it was shown that the Goodman mean stress correction method is predicted more conservative (minimum life) results. It was found to differ significantly the compressive and tensile mean stresses. The compressive mean stress are beneficial however tensile mean stress detrimental to the fatigue life. The effect of materials and components S-N was also investigated and not found to give any large advantages, however the effect of certainty of survival was found to give noticeable advantages and it concluded that the 99.9% are fond to be design criteria. The proposed technique is capable of determining premature products failure phenomena.
TL;DR: In this paper, a high-cycle fatigue life model for structures subjected to variable amplitude multiaxial loading is presented, which is characterized by the choice of a damage factor related to the accumulated mesoscopic plastic strain per stabilised cycle, and the use of a mesoscopic mechanical behaviour taking into account the fatigue mechanisms such as plasticity and void growth.
Abstract: A high-cycle fatigue life model for structures subjected to variable amplitude multiaxial loading is presented in this paper. It treats any kind of repeated blocks of variable amplitude multiaxial loading without using a cycle counting method. This model based on a mesoscopic approach is characterized by the following features: (i) the choice of a damage factor related to the accumulated mesoscopic plastic strain per stabilised cycle; (ii) the use of a mesoscopic mechanical behaviour taking into account the fatigue mechanisms such as plasticity and void growth. This behaviour is a von Mises elastoplastic model with linear kinematic hardening and hydrostatic stress dependent yield stress. The fatigue life model has six parameters identified with one SN curve and two fatigue limits. In-phase and out-of-phase experimental tests from the literature are simulated. The predicted fatigue lives are compared to experimental ones.