Showing papers on "Vibration fatigue published in 2003"
TL;DR: In this paper, a fatigue model for glass fiber-reinforced plastic composites that includes the non-linear effect of stress ratio and load frequency on the fatigue life was proposed.
Abstract: Current models used to predict the fatigue life of glass fibre-reinforced plastic composites do not accurately consider the effects of load stress ratios and load frequencies. These models usually require significant amount of experimental data to establish a set of characteristic fatigue curves for a given composite. This paper proposes a fatigue model for glass fibre-reinforced plastic composites that includes the non-linear effect of stress ratio and load frequency on the fatigue life. The model can be used to predict the fatigue behavior of a composite material using a well-defined minimum number of tests. Fatigue data from the literature and selected research laboratories were used to test the model. Predictions were found to be in good agreement with all experimental data adequately accounting for the influence of test frequency and stress ratio on the fatigue life of composites.
191 citations
TL;DR: In this paper, a stress-based method for low/medium-cycle fatigue assessment was proposed by considering the plane of maximum shear stress amplitude coincident with the microcrack initiation plane, which requires the calculation both of the maximum normal stress relative to the same plane.
Abstract: This paper extends to low/medium-cycle fatigue a stress-based method recently proposed by the same authors for high-cycle multiaxial fatigue assessments. By considering the plane of maximum shear stress amplitude coincident with the microcrack initiation plane, the method requires the calculation both of the maximum shear stress amplitude and the maximum normal stress relative to the same plane. Multiaxial fatigue life estimates are made by means of bi-parametric modified Wohler curves, which take into account the mean stress effect, the influence of the out-of-phase angle and the presence of notches by using a generalization to multiaxial fatigue of the fatigue strength reduction factor K f . Approximately 700 experimental data taken from the literature are used to demonstrate that the method is a useful tool to summarize fatigue strength data of both smooth and notched components, subjected to either in-phase or out-of-phase loads. Finally, a simple practical rule for the calculation of the multiaxial fatigue strength reduction factor is proposed.
148 citations
TL;DR: In this paper, a multiaxial fatigue criterion for random loading is proposed, where the orientation of the critical plane, where fatigue life estimation is carried out, is determined from the weighted mean position of the principal stress directions.
Abstract: A multiaxial fatigue criterion for random loading is proposed. Firstly, the orientation of the critical plane, where fatigue life estimation is carried out, is determined from the weighted mean position of the principal stress directions. Then, the scalar value of the normal stress vector N(t) perpendicular to the critical plane is taken as the cycle counting variable since the direction of such a vector is fixed with respect to time (conversely to the time-varying direction of the shear stress vector C(t)), and a nonlinear combination of normal and shear stress components acting on the critical plane is used to define an equivalent stress amplitude. Finally, a damage accumulation model is employed to process such an equivalent stress amplitude and to determine fatigue endurance. This criterion is herein applied to some relevant random fatigue tests (proportional bending and torsion).
114 citations
TL;DR: In this paper, the use of the acoustic emission technique to monitor fatigue crack propagation in steel compact tension specimens and T-section girders is described, based on correlations between crack propagation rates, acoustic emission count rates and stress intensity factor range procedures are suggested for predicting remaining fatigue life.
105 citations
TL;DR: In this article, a full-scale cable model was constructed in the field, and aerodynamic behavior of this cable model is observed under various weather conditions, which might be considered as the rain-wind-induced vibration, was observed.
81 citations
27 May 2003
TL;DR: The fatigue strength of the Pb-free solder and Pb solder was evaluated on the basis of the maximum principal stress calculated by FEM and the experimental results, and it was revealed that themaximum principal stress is the driving force to package failure.
Abstract: In this paper, a new method is proposed for evaluating the high-cycle fatigue strength of BGA (Ball Grid Array) packages with Pb-free solder and Pb–Sn solder due to vibration. An attached weight induced mixed mode stress in the solder ball of a package was used. To consider the effect of the mixed mode stress that occurred in a solder ball and the frequency to fatigue strength of the solder ball, a test was carried out with the three kinds of weights (σn/τn = 4, 5, and 6) at various frequencies (10–27 Hz). To clarify the effect of frequency, a nonlinear analysis with a viscoplastic model was carried out within the range of 0.001–3450 Hz. From the continuous observation of the cross-section of the package and finite element method (FEM) analysis results, it was revealed that the maximum principal stress is the driving force to package failure. Although an intermetallic compound in both packages and a Pb-rich region in a Pb–Sn solder based package were confirmed by EDX microprobe analysis, they do not contribute to the initiation of a crack in a solder ball. The fatigue strength of the Pb-free solder and Pb solder was evaluated on the basis of the maximum principal stress calculated by FEM and the experimental results.
69 citations
TL;DR: In this paper, a mathematical model of the material's behavior under cyclic loading taking into account the dynamics of the fatigue process, including the number of cycles to failure, induced by the mean stress value is presented.
46 citations
TL;DR: In this paper, a finite element (FE) model of a large suspension steel bridge for fatigue stress analysis is presented, and the verification of the model is carried out with the help of the measured bridge modal characteristics and the online data measured by the structural health monitoring system installed on the bridge.
45 citations
TL;DR: In this article, a new structural optimisation algorithm based on fatigue life is introduced, and the two key decisions in implementing this algorithm are firstly what assumption about the stress state (uniaxial or multiaxial proportional or non-proportional) should be made and secondly what method of stress calculation should be used (quasi-static, transient dynamic or harmonic modal stress analysis).
43 citations
TL;DR: In this paper, an analytical and experimental investigation of the fatigue crack growth behavior in attachment lugs subjected to a randomized flight-by-flight spectrum was conducted, where experiments were performed under a load spectrum and compared with the fatigue life prediction using the stress intensity factors by different methods.
41 citations
TL;DR: A damage tolerance reliability analysis methodology for automotive spot-welded joints under multi-axial and variable amplitude loading history and a probabilistic crack growth model combined with a randomized strain-life curve family and the stress analysis result to develop a strain-based probabilism fatigue crack initiation life prediction for spot welds.
TL;DR: In this article, the effects of fatigue on damping factor were studied for 6061-T6511 aluminium alloy and the experiments showed that the damping energy changes with the number of fatigue cycles.
Abstract: Studies in fatigue can be summarized into two stages, fatigue crack initiation and crack propagation. Fatigue damage may increase the risk of failure under cyclic load. Energy dissipation, termed damping, occurs in engineering metals and is a function of the cyclic loading history. Damping behaviour of materials has been estimated using many different experimental techniques, and parameters i.e. the loss factor vs. strain amplitude, frequency range, etc. However, micro-structural changes in the form of fatigue damage are also contributors to damping in engineering materials. In order to measure energy dissipation, a damping monitoring method has been used. Under a constant cyclic load up to the point of fatigue crack initiation, the effects of fatigue on damping factor were studied for 6061-T6511 aluminium alloy. In the experiments, the stress levels were below yield point, 50% and 70% of ultimate strength. Experimental results showed that the damping factor changes with the number of fatigue cycles. Percentage increase in damping energy was calculated using experimental data.
Journal Article•
TL;DR: In this article, the authors evaluated the fatigue life of ship structures based on a probabilistic approach that considers the stochastic nature of the ocean environmental loading and the service profile of the ship.
Abstract: The paper addresses the evaluation of the fatigue life of ship structures based on a probabilistic approach that considers the stochastic nature of the ocean environmental loading and the service profile of the ship. The method is based on a linear spectral analysis of the stress range response. The local stress range response transfer functions are obtained by using a three-dimensional finite element model. The response process for each short-term sea state is modelled by a Rayleigh distribution. The long-term response period and long-term stress range distribution are then determined and are fitted as a Weibull distribution. The Palmgren-Miner linear cumulative damage model is applied. An example calculation is presented for a tanker and the influence of several scatter diagrams on the fatigue life of structural details is examined.
TL;DR: In this paper, an experimental framework is developed to automatically track the health of the structure on-line with the performance of fatigue tests using a combination of the maximum likelihood estimator and an auto-regressive model.
10 Dec 2003
TL;DR: In this paper, a vibration fatigue test and analysis methodology for flip chip solder joint fatigue life prediction have been developed using accelerometer and high speed camera measurements during vibration tests and a sinusoidal sweep test within a narrow band near the fundamental resonant frequency was used.
Abstract: Vibration fatigue tests and analysis for flip chip solder joint reliability assessments were investigated. Dynamic characterizations of flip chip on board (FCOB) assemblies were evaluated using accelerometer and high speed camera measurements during vibration tests. A vibration fatigue test and analysis methodology for flip chip solder joint fatigue life prediction have been developed. Out-of-plane vibration fatigue tests were investigated for constant G-level tests at 3 G, 5 G and 10 G respectively. A sinusoidal sweep test within a narrow band near the fundamental resonant frequency was used. Solder joint failure detection was made by daisy chained resistance monitoring during the test. A plot of G-level versus mean time to failure (MTTF) was developed. A varying G-level vibration test with 3 G, 5 G and 10 G blocks arranged in ascending sequence was conducted for cumulative fatigue damage assessment study. The linear cumulative damage analysis method (Miner's rule) predicted non-conservative results for vibration fatigue failures in the flip chip solder joints. Finite element analysis (FEA) using a global-local beam modeling method was used to compute the fundamental natural frequency result compared to experimental data. A quasi-static analysis method was developed to model the effect of flip chip location on solder joint fatigue life.
09 Apr 2003
TL;DR: The use of nonlinear acoustics, and in particular harmonic generation, continues to gain interest as a means to characterize microstructural changes in engineering materials as a result of processing and in-service conditions as mentioned in this paper.
Abstract: The use of nonlinear acoustics, and in particular harmonic generation, continues to gain interest as a means to characterize microstructural changes in engineering materials as a result of processing and in‐service conditions Typical measurements involve the propagation of a monochromatic longitudinal wave toneburst through the bulk of a sample in a through‐transmission arrangement This arrangement is not well suited for field applications, where two sided access is limited and parallel surfaces are rare Harmonic generation measurements to monitor fatigue damage in acro engine alloys subject to fatigue will be presented The use of Rayleigh waves has allowed one sided access and accommodates a small amount of surface curvature while restricting the probing wave to the surface where fatigue damage is typically initiated Early results using uncalibrated receiving transducers on Ni‐based alloys demonstrate a sensitivity to damage accumulation in low cycle fatigue, where damage is spread over the sample surface Damage accumulation in high cycle fatigue is concentrated in small regions on the sample surface and so has not yet been revealed by changes in the generation of harmonics using the uncalibrated probes
DOI•
01 Jan 2003
TL;DR: Mei et al. as mentioned in this paper presented a finite element modal formulation for large amplitude free vibration of arbitrary laminated composite shallow shells, which was transformed into general Duffing-type modal equations with modal amplitudes of coupled linear bending-inplane modes.
Abstract: NONLINEAR RESPONSE AND FATIGUE ESTIMATION OF AEROSPACE CURVED SURFACE PANELS TO ACOUSTIC AND THERM AL LOADS Adam Przekop Old Dominion University, 2003 Director: Dr. Chuh Mei This work presents a finite element modal formulation for large amplitude free vibration of arbitrary laminated composite shallow shells. The system equations of motion are formulated first in the physical structural-node degrees of freedom (DOF). Then, the system is transformed into general Duffing-type modal equations with modal amplitudes of coupled linear bending-inplane modes. The linear bending-inplane coupling is due to the shell curvature as well as unsymmetric lamination stacking. Multiple modes, inplane inertia, and the first-order transverse shear deformation for composites are considered in the formulation. A triangular shallow shell finite element is developed from an extension of the triangular Mindlin (MIN3) element with the improved shear correction factor. Time numerical integration is employed to determine nonlinear frequency of vibration. An iterative procedure to determine the judicious initial conditions for periodic panel response is developed and presented. By neglecting the inplane inertia effect, the general Duffing modal equations in functions of modal amplitudes of linear bending modes only are also formulated and presented. This approach is used for comparison of results with existing classic analytical methods. The Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. differences in characterizing a shallow shell behavior with modal amplitudes of coupled linear bending-inplane and bending only modes are demonstrated and discussed. Then the finite element modal formulation for large amplitude random response of shallow shell panels to acoustic excitation and elevated temperature is presented. Reduced order integration is used to determine strains. Rainflow counting method and SN curves are combined by means of damage accumulation theory to predict panel fatigue life. Factors contributing the softening effect, namely unsymmetrical lamination and curvature are investigated along with their impact on the fatigue life. Two types of excitation inputs are considered. Responses and fatigue life estimations to simulated band-limited Gaussian white noise and to in-flight recorded pressure fluctuation microphone data are presented and compared. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
TL;DR: In this article, a systematic method has been outlined to find the fatigue damage in the continuous bridge girder based on stress range frequency histogram and fatigue strength parameters of the bridge materials.
Abstract: The fatigue damage assessment of bridge components by conducting a full scale fatigue testing is often prohibitive. A need, therefore, exists to estimate the fatigue damage in bridge components by a simulation of bridge-vehicle interaction dynamics due to the action of the actual traffic. In the present paper, a systematic method has been outlined to find the fatigue damage in the continuous bridge girder based on stress range frequency histogram and fatigue strength parameters of the bridge materials. Vehicle induced time history of maximum flexural stresses has been obtained by Monte Carlo simulation process and utilized to develop the stress range frequency histogram taking into consideration of the annual traffic volume. The linear damage accumulation theory is then applied to calculate cumulative damage index and fatigue life of the bridge. Effect of the bridge span, pavement condition, increase of vehicle operating speed, weight and suspension characteristics on fatigue life of the bridge have been examined.
TL;DR: In this paper, the simulation of rolling contact fatigue is conducted under spherical contact to predict a crack initiation life accurately, it is necessary to calculate contact stress and subsurface stresses accurately Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions and the subsural stress field is obtained using rectangular patch, solutions Based on these stress values, several multiaxial high-cycle fatigue criteria are used and the critical loads corresponding to fatigue limits are calculated.
Abstract: In this study, the simulation of rolling contact fatigue is conducted under spherical contact To predict a crack initiation life accurately, it is necessary to calculate contact stress and subsurface stresses accurately Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions and the subsurface stress field is obtained using rectangular patch, solutions Based on these stress values, several multiaxial high-cycle fatigue criteria are used and the critical loads corresponding to fatigue limits are calculated The criteria were classified into three categories, namely the critical plane approach, the stress invariant approach and the approach based on the mesoscopic scale The simulation results show that the critical load is decreasing rapidly and the site of crack initiation also moves rapidly to the surface from the subsurface when the friction coefficient exceeds a specific value for all three fatigue criteria Presented as a Society of Tribolo
TL;DR: Based on the crack tip plasticity, a theoretical analysis has been performed and a model has been set up to consider the effect of the applied stress ratio on fatigue threshold as mentioned in this paper, which is very easy to use and no fatigue crack closure measurement is needed.
TL;DR: In this paper, a load spectrum and an engineering analysis from first principles for estimating the fatigue life of GRP blades of horizontal axis wind turbines are presented, where the distributions of aerodynamic loads, w hich affect the fatigue lifetime of the blade, are analyzed using strip theory.
Abstract: This tutorial paper presents a load spectrum and an engineering analysis from first principles for estimating the fatigue life of GRP blades of horizontal axis wind turbines. The distributions of aerodynamic loads, w hich affect the fatigue life of the blade, are analyzed using strip theory. The stiffening effect on a rotating blade is discussed using the multi-body dynamics method. The influences of this dynamic stiffening effect and composite material anisotropy on the blade vibration modes are analyzed. Then, the dynamic stress response caused by the deterministic dynamic loads, such as aerodynamic load, gravitational load and rotating centrifugal load etc, is calculated using finite element modal superposition method. Fatigue damage performance, fatigue damage rule and the fatigue life estimate method for GRP blades are included. Finally, applying the Palmgren Miner rule for linear fatigue damage accumulation, an estimate of safe working life is made. The fatigue life estimate for a 1.5 MW wind turbin...
TL;DR: In this article, two fatigue life analysis approaches, the strain-life approach and the crack growth fracture mechanics approach, are applied for bending fatigue life prediction of carburized U-Notch bar samples.
Abstract: Axle primary gearing is normally carburized for high and balanced resistance to contact fatigue, wear, bending fatigue, and impact loading. The focus of this work is on bending fatigue which is a key design consideration of automotive and commercial vehicle axle gearing. Since a carburized component is basically a composite material with steep gradients in carbon content, hardness, tensile strength and microstructure from surface to the middle of the cross section combined with non-linear residual stress, its bending fatigue life prediction is a complex and challenging task. Many factors affect the bending fatigue performance of axle gearing, such as gear design, gear manufacturing, loading history during service, residual stress distribution, steel grade, and heat treatment. In this paper, the general methodology for bending fatigue life prediction of a carburized component is investigated. Carburized steel composites are treated as two homogeneous materials: case and core. Materials properties are evaluated separately with simulated case and simulated core samples. Two fatigue life analysis approaches are applied for bending fatigue life analysis: the strain-life approach and the crack growth fracture mechanics approach. The fundamental materials fatigue properties needed include strain controlled axial fatigue test data, crack growth rates and fracture toughness. Residual stress distributions are characterized and their effect on bending fatigue life is included in both fatigue life analysis approaches. Bending fatigue tests are conducted on carburized U-Notch bar samples, and the test results are compared with the life prediction results. Several important factors in bending fatigue life analysis of carburized components are discussed and included in the life prediction, such as bending stress gradient, mean stress, initial defect size, and residual stress. Finally the pros and cons of the two fatigue life analysis approaches are compared and summarized.
01 Jan 2003
TL;DR: In this paper, the use of stress predictions from equivalent linearization analyses in the computation of high-cycle fatigue life is examined, and the authors make comparisons of fatigue life predictions based upon the stress response obtained from comparable linear and numerical simulation analyses to determine the range over which the equivalent linear analysis is applicable.
Abstract: The use of stress predictions from equivalent linearization analyses in the computation of high-cycle fatigue life is examined. Stresses so obtained differ in behavior from the fully nonlinear analysis in both spectral shape and amplitude. Consequently, fatigue life predictions made using this data will be affected. Comparisons of fatigue life predictions based upon the stress response obtained from equivalent linear and numerical simulation analyses are made to determine the range over which the equivalent linear analysis is applicable.
25 Aug 2003-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a new damage parameter, which combines the critical plane theory, shear stress work, the micro-mechanism of fatigue damage and additional hardening is introduced as a friction coefficient.
Abstract: This paper provides a new damage parameter, which combines the critical plane theory, shear stress work, the micro-mechanism of fatigue damage and additional hardening. In addition, the non-proportional scale representing the grade of additional hardening is introduced as a friction coefficient. Based on this parameter, the relationship between the damage parameter and fatigue cycle is derived to build up a fatigue damage accumulation model using finite element program and numerical simulation. Effort is also focused on evaluating the fatigue life.
01 Jan 2003
TL;DR: In this article, the fatigue life of wind turbine blades that are exposed to the random loading environment of atmospheric winds is described with random data analysis procedures, and the incident wind speed and the stresses caused by these winds are expressed in terms of probability density functions, while the fatigue-life vs stress level relationship is treated deterministically.
Abstract: The fatigue life of wind turbine blades that are exposed to the random loading environment of atmospheric winds is described with random data analysis procedures. The incident wind speed and the stresses caused by these winds are expressed in terms of probability density functions, while the fatigue life vs stress level relationship is treated deterministically. This approach uses a "damage density function" to express fatigue damage as a function of wind speed. By examining the constraints on the variables in the damage density expression, some generalizations of the wind turbine fatigue problem are obtained. The area under the damage density function is inversely related to total fatigue life. Therefore, an increase in fatigue life caused by restricted operation in certain wind regimes is readily visualized. An "on parameter", which is the percentage of total time at each wind speed that the turbine actually operates, is introduced for this purpose. An example calculation is presented using data acquired from the DOE 100-kW turbine program. *This work was performed at Sandia National Laboratories and was supported by the US Department of Energy under Contract Number DE-AC04-76DP00789.
TL;DR: In this article, a multiscale approach has been developed to design the structures against fatigue, starting from the dynamics of the vehicle and ending with the calculation of structural details using a local approach to assess the fatigue life.
Abstract: The moving of vehicles on chaotic ground induces dynamic multiaxial loading on structures and mechanical components. As a consequence, early fatigue damage occurs especially in structural details such as notched areas and welded parts. A multiscale approach has been developed to design the structures against fatigue, starting from the dynamics of the vehicle and ending with the calculation of structural details using a local approach to assess the fatigue life. The methodology of the local approach developed is introduced. The evaluation of the prediction capability of this local approach is described. Finally, the application to the fatigue life assessment of welded elements is presented and compared to experimental results. The major parameters of the weld geometry that govern the material resistance against fatigue are pointed out. They concern geometrical features depending on the quality of the weld. Their influence on the weld durability is outlined and the way the proposed assessment method accounts for them in a quantitative manner is detailed.
01 Jan 2003
TL;DR: In this article, the authors proposed a unified fatigue life prediction method to predict the fatigue life of marine structure using fatigue crack propagation (FCP) theory instead of the currently used cumulative fatigue damage (CFD) theory using S N curves.
Abstract: Recently, the second author proposed a unified fatigue life prediction method. The essence of the unified method is to predict the fatigue life of marine structure using fatigue crack propagation (FCP) theory instead of the currently used cumulative fatigue damage (CFD) theory using S N curves. There have been some fatigue life prediction methods in the recent decades, but most of them cannot explain some known fatigue phenomena. However, Unified Fatigue Life Prediction Method can manage to explain them. It can consider the influences of initial defects and load sequences. The main obstacle of adoptimg the unified fatigue life prediction method is the determination of the fatigue crack growth rate. Based on a comparative study of several existing crack growth rate laws, a new 9 parameter fatigue crack growth rate law was proposed by the second author which was derived from extending the McEvily crack growth rate law. It offers a general formula which can illustrate the condition from threshold to unstable fracture, also, it uses the conception of virtual strength (σ V), which can solve the paradox that the static test of the material′s ultimate strength (σ u) is generally higher than the yield stress (σ Y). The purpose of this paper is to address the problem how to estimate the 9 model parameters using the existing fatigue data. To solve this problem, nonlinear curve fitting theory is used. A sensitivity analysis is also carried out for the 9 model parameters to show some parameter′s sensitivity property. Based on the collection of some experimental data, fatigue crack growth rates for some metals are given.
Journal Article•
TL;DR: In this paper, a damping monitoring method that estimates damping factor by vibration excitation has been used in order to measure energy dissipation, and experimental results showed that the damping condition changes with the number of fatigue cycles.
Abstract: The fatigue behavior of materials has been estimated using many different experimental techniques in order to describe damage. Fatigue damage may increase the risk of failure under cyclic load. Energy dissipation occurs in engineering metals as a function of the cyclic loading history. In order to measure energy dissipation, a damping monitoring method that estimates damping factor by vibration excitation has been used in this study. Under constant cyclic axial loads, 50% and 70% of ultimate strength, the effects of the number of fatigue cycles on the damping factor were measured for two different low carbon steels. The experimental results showed that the damping factor changes with the number of fatigue cycles.
Patent•
28 Apr 2003
TL;DR: In this paper, the authors predict the life of engine parts until resulting in breakage by three breaking factors of low cycle fatigue, creep and high cycle fatigue without constructing a large-scale database requiring immense man-hours.
Abstract: PROBLEM TO BE SOLVED: To accurately predict the life of engine parts until resulting in breakage by three breaking factors of low cycle fatigue, creep and high cycle fatigue without constructing a large-scale database requiring immense man-hours. SOLUTION: The life of engine parts when each breaking factor is independently applied is obtained by an experiment and set to databases DB11-13. When predicting a composite fatigue life by three breaking factors, time series simulation data of thermal load and vibration applied to the engine parts when operating an engine is obtained by an FEM analysis, and based on this data and the life data of the databases DB11-13, the amount of damage by each breaking factor of low cycle fatigue, creep and high cycle fatigue is obtained. The amount of creep fatigue damage is computed considering the influence of stress relaxation by interaction. The amount of high cycle fatigue damage is computed considering the influence of damage caused by vibration of a fatigue limit or less. Breaking is determined when the total of the damage amounts by three breaking factors becomes a prescribed value. COPYRIGHT: (C)2005,JPO&NCIPI
TL;DR: In this article, an original critical plane high cycle multiaxial fatigue life prediction method can deal with sequential application of nonsimilar loading, where the plastic strain accumulated at the scale of the grain is considered the damage variable.