Fatigue Damage Research Papers - Academia.edu (original) (raw)

This paper presents the theoretical modeling of carbonation in fatigue-damaged concrete. First, a residual strain-based effective carbon dioxide diffusion coefficient in fatigue-damaged concrete was proposed. Based on that, the general carbonation equations were established for concrete with uniform compres-sive, gradient compressive and gradient tensile damage patterns. Then a numerical program was written to solve the established partial differential carbonation equations. Subsequently, the numerical carbon-ation model was validated by comparing the predicted carbonation depths with experimental results. Finally, parametric studies were conducted on carbonation in commonly used concretes with various fatigue damage patterns, which separated the effects of residual strains and residual curvatures. The parametric studies showed that fatigue damage did not alter the widely accepted proportional relationships between carbonation depths and square roots of exposure durations. Moreover, the effects of exposure conditions on carbonation of concrete were far more influenced by residual strains than by residual curvatures.

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- Carbonation of Concrete, Fatigue Damage
- by Nouari Abdessamed
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- Design of Experiments, Accelerated Life Testing, Reliability, Estimation

In material engineering it is important to determine the cause of the failure & prevention of the failure .In present day the failure of the machine component is about 90% of the failure is because of the fatigue. In present study the failure of the shaft in the yaw gear box is analyzed .As we the shaft is rotating part of the engine it transmit the power from the one part of the engine to another part. It holds the maximum stress. In this case shaft of heat treated component with ultimate tensile strength Su= 2100Mpa is analysis done with ANSYS (FEA) software & compared with the theoretical calculation. There are dif erent methods which are used to predict fatigue life include stress life(S-N), strain Life (E-N) and Linear Elastic Fracture Mechanics (LEFM). In this project study, S-N approach is used to predict fatigue life for out-put shaft.

- by IAEME Publication
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- Fatigue Life, Fatigue Damage, Shaft, Iaeme Ijmet

In this work, the problem of fatigue damage prediction in the entire body of metallic structures through sparse output-only vibration measurements is investigated. The use of limited vibration measurements for output-only estimation of fatigue
accumulation in structural systems was first proposed in [1]. Online strain estimates for multiple structural locations, derived from vibrational response measurements may be combined with S-N fatigue curves, damage accumulation models and rain-flow cycle counting procedures to predict accumulation of fatigue damage over the entire body of the metallic structure. In order to reliably predict fatigue damage, an accurate estimate of stress time histories is required, and the aforementioned necessitates high quality estimates of the states at corresponding degrees-of-freedom of the model. State estimation in presence of modeling uncertainties have been studied extensively, however, the input itself is typically assumed to be either known or broadband. In practice, the acquisition of precise load measurements is often impractical and sometimes impossible. Moreover, in operational cases the condition of stationarity is seldom satisfied. The latter substantiates the need to profit from the schemes developed for joint state and input estimation. Eftekhar Azam et al. [24] have recently proposed a novel dual Kalman filter (DKF) to accomplish the task of input-state estimation for linear time invariant systems via sparse acceleration measurements. In this article, the DKF and other state-of-the-art methods such as the augmented Kalman filter are employed for dynamic strain estimation enabling the development of fatigue damage accumulation maps. The effect of sensor configuration (number and location of sensors) on the accuracy of the fatigue estimates is also studied.

- by Saeed Eftekhar Azam and +1
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- Structural Health Monitoring, Vibration measurement, Fatigue Damage, Dual Kalman Filter

This paper first introduced a numerical carbonation model (NCM) for fatigue-damaged concrete. Then, based on the NCM, a simplified carbonation model (SCM) for fatigue-damaged concrete was established, comprised of a non-damaged concrete contribution term and a fatigue damage contribution term, through Monte Carlo simulations. Both the NCM and SCM were verified by experimental results reported in the literature. Subsequently, an incremental method was proposed to consider the time-variant fatigue damage and exposure conditions. Finally, a case study was conducted, which determined that cumulating fatigue damage could have a big influence on carbonation depth evolution. Meanwhile, differences in the cumulating fatigue damage could lead to noticeable differences in carbonation depth evolution among different points in the same concrete bridge. Moreover, drastic increases of CO 2 concentration and temperature could induce relationships of carbonation depths with square roots of service times to remarkably deviate from the proportional laws widely accepted under a time-invariant environment.

- by Chao Jiang
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- Carbonation of Concrete, Fatigue Damage
- by Beena Jawalkar
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- Civil Engineering, Thermodynamics, Concrete, Damage Mechanics