Finite element based fatigue analysis of 6082 Aluminum alloy under random loading (original) (raw)
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Engineering, Technology & Applied Science Research
Fatigue damage increases with applied load cycles in a cumulative manner. Fatigue damage models play a key role in life prediction of components and structures subjected to random loading. The aim of this paper is the examination of the performance of the “Damaged Stress Model”, proposed and validated, against other fatigue models under random loading before and after reconstruction of the load histories. To achieve this objective, some linear and nonlinear models proposed for fatigue life estimation and a batch of specimens made of 6082T6 aluminum alloy is subjected to random loading. The damage was cumulated by Miner’s rule, Damaged Stress Model (DSM), Henry model and Unified Theory (UT) and random cycles were counted with a rain-flow algorithm. Experimental data on high-cycle fatigue by complex loading histories with different mean and amplitude stress values are analyzed for life calculation and model predictions are compared.
MATEC Web of Conferences
The work presents a non-linear fatigue computation method together with finite element method, in which energy parameter has been used. The Proposed model has been used for simulation computations, based on experimental testing of Al-2024 aluminum alloy specimens subjected to two types of loads, i.e. variable blocs loading and random loading. Computations of energy parameter value have been donebased on the results of FEM elastic–plastic analysis of cyclic properties of a material. A computing Matlab-based algorithm of the fatigue life prediction methodology was developed. The proposed damage indicator is connected cycle by cycle to the Wöhler curve. Cycles were counted with the rain-flow algorithm, and damage was accumulated with this model and with the Palmgren–Miner rule. On the grounds of which fatigue life has been read off from only characteristics of specimens. An experimental verification shows a satisfactory agreement between the fatigue life calculation results by the prop...
The International Journal of Advanced Manufacturing Technology, 2016
This paper proposes an engineering approach to determine the probabilistic Kitagawa diagram of defective A356-T6 aluminum alloy considering the modification introduced by varying the secondary dendrite arming spacing (SDAS). The developed approach is carried out by coupling of FE analysis, defect stress gradient (DSG) criterion, and Monte Carlo simulation (MCS) method. In this context, a 3D-finite element analysis (FEA) for different cases of defect sizes and loading conditions using ABAQUS commercial software is established. The nonlinear isotropic/kinematic hardening model implemented in ABAQUS is used to characterize material behavior. Comparing with experimental results, the developed probabilistic approach presents an efficient numerical tool for predicting fatigue limit under fully reserved tension and torsion loadings due to the random distribution of the SDAS parameter. These probabilistic Kitagawa diagrams allow the engineer to be engaged in a practical problem to evaluate the fatigue limit in a more efficient and safe way. In addition, the sensitivity effects of defect size and SDAS parameter for predicting fatigue limit of A356-T6 aluminum alloy under alternate tension and torsion loadings is discussed using response surface methodology (RSM).
Fatigue Life Under Random Load History Derived from Exceedance Curves Using Different Algorithms
Fatigue & Fracture of Engineering Materials and Structures, 1993
Low cycle fatigue life and crack growth rates were analytically estimated for random load sequences, generated from three combat aircraft load exceedance curves using different algorithms, including simulated rainflow cycle count, extreme-to-extreme excursions, upper to lower bound excursions and unrestricted peak-trough excursions. Also, the response of a fatigue meter to a random load sequence was simulated. Fatigue damage for the different load histories was computed using material constants for an A l C u alloy. Computed fatigue damage was relatively insensitive to the algorithm used for load sequence generation from combat aircraft load exceedance curves. Fatigue meter data based damage estimates were, however, sometimes unconservative.
Influence of the Transient Material Behaviour in the Fatigue Life Estimation Under Random Loading
Procedia Engineering, 2015
The estimation of the fatigue life under variable amplitude loading is a fundamental step in the design phase. To consider variable amplitudes in the fatigue design the linear damage accumulation is applied, thus disregarding non linearity. When materials show cyclic hardening/softening, the hypotheses from Palmgren and Miner are not valid and this causes appreciable errors in the fatigue life estimation. Fatigue tests were carried out on the steel HC340LA. The influence of strain softening and mean stress relaxation is shown. A simplified method for considering this transient phase is presented. More accurate results can be achieved by applying this method.
International Journal of Mechanical Sciences, 2002
Analytical approaches concerning size, stress gradient and technological e ects such as surface roughness and residual stresses induced during manufacturing processes are presented and discussed in this paper. Their implementation into the Short-Crack-Model for fatigue-life (lifetime to initiation of cracks of a size of 0.5 -1 mm) prediction of engineering components subjected to cyclic loading is explained in detail. The procedures to consider the aforementioned e ects are demonstrated by using an example of a forged and tempered steering shaft made of low-alloyed steel subjected to variable amplitude bend loading. The corresponding experimental results are used to check the accuracy of the analytical fatigue-life prediction. The comparison between analytically calculated and experimentally determined fatigue-life values emphasises the signiÿcance of technological e ects (surface roughness, residual stresses) on fatigue-life estimation and the usefulness of the Short-Crack-Model for fatigue-resistant design of engineering components. ?
International Journal of Fatigue, 2016
Aim of this study is an interpretation of the influence of variable-amplitude (VA) cycles superimposed to low-frequency loads on fatigue life of 7075-T651 Al-alloys. Constant-amplitude (CA) 20 kHz stress/ strain-life (S-N) and (e-N)-curves with and without superimposed mean loads serve as basis. For combined fatigue loading, lifetime measurements were performed. Lifetime estimations based on the S-N results reveal a damaging effect of the superimposed ultrasonic vibrations in the high cycle fatigue (HCF) and the very high cycle fatigue (VHCF) regimes. The CA and VA-life time results are correlated with fractographic observations. An interpretation of fatigue lives under combined low and high-frequency VA-loading is proposed considering small/short-crack propagation and arrest mechanisms.
A method for calculation of finite fatigue life under multiaxial loading in high-cycle domain
""A method for fatigue life assessment in high-cycle domain under multiaxial loading is presented in this paper. This approach allows fatigue assessment under any kind of load history, without limitations. The methodology lies on the construction - at a macroscopic level - of an “indicator” in the form of a set of cycles, representing plasticity that can arise at mesoscopic level throughout fatigue process. During the advancement of the loading history new cycles are created and a continuous evaluation of the damage is made.
Design Life Prediction of Structural Components Subjected to Various Fatigue Loadings
Procedia Engineering, 2013
Many structural components are subjected to cyclic assessment and reliability prediction of engineerin irregular and random nature, are obviously critical iss and design life assessment of the structural compone has been carried out by linear elastic fracture mecha FORTRAN(R) programming language. Modified W applied to evaluate fatigue crack growth and its retar (single, multiple and spectrum). The MWM is based crack and CCM is based on the crack closure effects structural members subjected to tensile-compressive models. Quantitative retardation based on the residua using MWM and applied to the material specimen: with edge crack for 6061-T6-Al-Alloy to predict the obtained have been compared with the experiment amplitude loading models in conjunction with Whe compared with the experimental data and are in good
Methodology to evaluate fatigue damage under multiaxial random loading
Engineering Fracture Mechanics, 2017
Manufacturers must assure the reliability of their products, what implies guaranteeing optimal working conditions during their service life. In this work, a methodology is proposed to estimate the damage experienced by a component under non-proportional loading to be made aiming at predicting when the component will fail and where the failure location will happen. In the present case, a novel cyclic counting model is introduced based on a hybrid variant of the rainflow algorithm applied to the results of the Papadopoulos critical plane approach using the Basquin fatigue model. In this way, the damage model is achieved.