Early Fatigue Damage of Magnesium Alloy On-Line Monitoring by Nonlinear Ultrasonic

2010 ◽  
Vol 139-141 ◽  
pp. 194-197
Author(s):  
Bing Sheng Yan ◽  
Bin Wu ◽  
Cun Fu He ◽  
Jing Pin Jiao
Keyword(s):  
Fatigue Life ◽  
Magnesium Alloy ◽  
Yield Stress ◽  
Fatigue Damage ◽  
Stress Level ◽  
Second Harmonic ◽  
Experimental Results ◽  
Nonlinearity Parameter ◽  
Acoustic Nonlinearity Parameter ◽  
On Line

This research develops a robust experimental procedure to monitor the evolution of early fatigue damage in AZ31 magnesium alloy with the acoustic nonlinearity parameter , and demons- trats its reliability by measuring the linear relationship between amplitudes of the second-harmonic waves and fundamental waves squared. Using this system, of two sets of specimens with different stress level is measured. The experimental results show that there is a significant increase in linked to fatigue degree in the early stages of fatigue life and reaches the maximum about 55%of fatigue life, when the stress level is ±60%of the yield stress, can characterize the early fatigue damage of magnesium alloy. However, when the stress level is ±70%of the yield stress, there is a regular fluctuation in linked to fatigue degree, this experimental results can’t be explained.

scholarly journals Experimental Investigation of Second-Harmonic Lamb Wave Generation in Additively Manufactured Aluminum

2018 ◽  
Vol 1 (4) ◽  
Author(s):  
Benjamin Steven Vien ◽  
Wing Kong Chiu ◽  
L. R. Francis Rose
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Second Harmonic ◽  
Low Cycle Fatigue ◽  
Propagation Distance ◽  
Nonlinearity Parameter ◽  
Harmonic Amplitude ◽  
Cycle Fatigue ◽  
Fatigue Damage Accumulation

The correlation between the nonlinear acousto-ultrasonic response and the progressive accumulation of fatigue damage is investigated for an additively manufactured aluminum alloy AlSi7Mg and compared with the behavior of a conventional wrought aluminum alloy 6060-T5. A dual transducer and wedge setup is employed to excite a 30-cycle Hann-windowed tone burst at a center frequency of 500 kHz in plate-like specimens that are 7.2 mm thick. This choice of frequency-thickness is designed to excite the symmetric Lamb mode s1, which, in turn, generates a second-harmonic s2 mode in the presence of distributed material nonlinearity. This s1-s2 mode pair satisfies the conditions for internal resonance, thereby leading to a cumulative build-up of amplitude for the second-harmonic s2 mode with increasing propagation distance. Measurements of a nonlinearity parameter β derived from the second-harmonic amplitude are plotted against propagation distance at various fractions of fatigue life under constant amplitude loading, for three different stress levels corresponding to low-cycle fatigue (LCF), high-cycle fatigue (HCF), and an intermediate case. The results show both qualitative and quantitative differences between LCF and HCF, and between the additively manufactured specimens and the wrought alloy. The potential use of this nonlinearity parameter for monitoring the early stages of fatigue damage accumulation, and hence for predicting the residual fatigue life, is discussed, as well as the potential for quality control of the additive manufacturing (AM) process.

Decomposition Method to Detect Fatigue Damage Precursors in Thin Components Through Nonlinear Ultrasonic With Collinear Mixing Contributions

2020 ◽  
Vol 3 (2) ◽  
Author(s):  
Gheorghe Bunget ◽  
Stanley Henley ◽  
Chance Glass ◽  
James Rogers ◽  
Matthew Webster ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Crack Nucleation ◽  
Second Harmonic ◽  
Turbine Blades ◽  
Nonlinearity Parameter ◽  
Decomposition Technique ◽  
Acoustic Nonlinearity Parameter ◽  
Acoustic Nonlinearity ◽  
Nonlinear Ultrasonic ◽  
Short Time

Abstract Cyclic loading of mechanical components promotes the formation of dislocation substructures in metals as precursors to crack nucleation leading to final failure of the metallic components. It is well known within the ultrasonic community that the acoustic nonlinearity parameter is a meaningful indicator of the microstructural damage accumulation. However, current nonlinear ultrasonic techniques suffer from response saturation and limited resolution after 50% fatigue life of the metallic medium. The present study investigates the feasibility of incorporating collinear wave mixing interactions into second harmonic assessments to improve the sensitivity of the nonlinear parameter to a microstructural accumulation of damage precursors (DP). To this end, a decomposition technique was explored to obtain higher harmonics from short time-domain pulses propagating through thin metallic components such as jet engine turbine blades. The results demonstrate the effectiveness of the decomposition technique to measure the acoustic nonlinearity parameter as an early and continuous indicator of fatigue damage precursors throughout the service life of critical aircraft components. A micrographic study showed a strong correlation between the nonlinearity parameter and the increase in damage precursors throughout the life of the specimens.

scholarly journals Study on the Effect of Laser Quenching on Fretting Fatigue Life

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 566 ◽  
Author(s):  
Hongjian Zhang ◽  
Xufeng Yang ◽  
Haitao Cui ◽  
Weidong Wen
Keyword(s):  
Fatigue Life ◽  
Stress Level ◽  
High Stress ◽  
Fretting Fatigue ◽  
Test System ◽  
Experimental Results ◽  
Laser Quenching ◽  
Error Band ◽  
Hydraulic Servo ◽  
High Stress Level

Laser quenching hardening is one of the most used surface treated technologies. In order to study the effect of laser quenching on the fretting fatigue life, fretting fatigue experiments of TC11 (Ti-6.5Al-1.5Zr-3.5Mo-0.3Si) titanium alloy specimens with different surface conditions were carried out on a special hydraulic servo fatigue test system. The experimental results showed that laser quenching hardening has a good performance in increasing the fretting fatigue lives of the TC11 alloy. However, the effects of laser quenching on fretting fatigue are more obviously at low stress level than at high stress level, the fretting fatigue life was increased by 110.78% at low stress level and 17.56% at high stress level, respectively. Based on the critical plane approach, the traditional SWT (Smith–Watson–Topper) parameter was modified and used to describe the fretting fatigue life of the TC11 alloy after hardening by the consideration of the variations of the hardening layer’s elastic modulus. Compared with the experimental results, all the errors of the predicted results lied in the error band of two.

The Effect of Seabottom Proximity of the Vortex-Induced Vibrations and Fatigue Life of Offshore Pipelines

1983 ◽  
Vol 105 (4) ◽  
pp. 464-468 ◽  
Author(s):  
D. T. Tsahalis
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Experimental Results ◽  
Offshore Pipelines ◽  
Vortex Induced Vibrations

The effect of the seabottom proximity on the vortex-induced vibrations of suspended spans of offshore pipelines is discussed in the light of recent relevant experimental results. It is shown that the effect of the seabottom proximity is to drastically alter the vortex-induced vibrations of supsended spans resulting into longer fatigue lives or equivalently longer safe lengths. A “generalized” fatigue damage is formulated universally applicable to all suspended spans.

scholarly journals Research on Fatigue Damage of Compressor Blade Steel KMN-I Using Nonlinear Ultrasonic Testing

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Pengfei Wang ◽  
Weiqiang Wang ◽  
Jianfeng Li
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Ultrasonic Testing ◽  
Early Stage ◽  
Compressor Blade ◽  
Nonlinearity Parameter ◽  
Nonlinear Ultrasonic ◽  
Blade Steel ◽  
Scanning Electron ◽  
Peak Value

The fatigue damage of compressor blade steel KMN-I was investigated using nonlinear ultrasonic testing and the relation curve between the material nonlinearity parameter β and the fatigue life was obtained. The results showed that the nonlinearity parameter increased first and then decreased with the increase of the fatigue cycles. The microstructures were observed by scanning electron microscopy (SEM). It was found that some small defects like holes and pits appeared in the material matrix with the increase of the fatigue cycles, and the nonlinearity parameter increased correspondingly. The nonlinearity parameter reached the peak value when the microcracks initiated, and the nonlinearity parameter began to decrease when the microcracks further propagated to macrocracks. Therefore, it is proved that the nonlinearity parameter can be used to characterize the initiation of microcracks at the early stage of fatigue, and a method of evaluating the fatigue life of materials by nonlinear ultrasonic testing is proposed.

An elasto-plastic damage accumulation model for fatigue life predication of ductile metals at the yield stress

2021 ◽  
pp. 105678952110454
Author(s):  
Jindong Huo ◽  
Xiaochuan You ◽  
Jianan Hu ◽  
Zhuo Zhuang
Keyword(s):  
Fatigue Life ◽  
Yield Stress ◽  
Fatigue Test ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Cycle Fatigue ◽  
Ductile Metals ◽  
Plastic Damage ◽  
Proposed Model ◽  
Damage Accumulation Model

From the analysis of massive fatigue test data, we find a mismatch between the fatigue life predictions done by stress-life method (SN) and those by strain-life method (εN) around the yield stress of ductile metals. Since the SN and εN methods are widely used in engineering applications, this work aims to explain such mismatch and thereby to address the fatigue life prediction at material’s yield stress, at which the material’s elastic damage and plastic damage are comparable. Based on a normalized damage concept, we propose an elasto-plastic damage accumulation model, a data-driven approach, to evaluate the fatigue damage at the yield stress. By differentiating the damage caused by the elastic from the plastic, the damage of each loading cycle is formulated as a function of both stress and strain amplitudes to accurately capture the material’s response state. With introducing the strain-energy-density based weighting factor, the proposed model can accord well with the classical methods from low-cycle fatigue to high-cycle fatigue. When it comes to the yield stress, the fatigue life estimated by the proposed model compares favorably with the fatigue test data. Therefore, beyond clarifying the mismatch between the classical approaches, the proposed model is expected to improve the accuracy in fatigue damage evaluation of ductile metals at the yield stress.

Fatigue damage detection and prediction of fatigue life on a cantilever beam

2017 ◽  
Vol 8 (6) ◽  
pp. 648-655
Author(s):  
Manuel L. Aenlle ◽  
F. Pelayo ◽  
Alfonso Fernandez-Canteli
Keyword(s):  
Fatigue Life ◽  
Modal Analysis ◽  
Cantilever Beam ◽  
Fatigue Damage ◽  
Structural Engineering ◽  
Dynamic Properties ◽  
Element Model ◽  
Experimental Results ◽  
Content Type ◽  
Eurocode 3

Purpose Fatigue failure is an important criterion to be considered in the design of structures and mechanical components. Catastrophic failure of structures in service conditions can be avoided using adequate techniques to detect and localize fatigue damage. Modal analysis is a tool used in mechanical and structural engineering to estimate dynamic properties and also to monitor the health of structures. If modal analysis is applied periodically to a structure, fatigue damage can be detected and localized and the fatigue life can be extended by means of suitable reinforcement and repairing. The paper aims to discuss these issues. Design/methodology/approach The experimental results corresponding to the fatigue tests carried out on a steel S-275 cantilever beam are presented. Operational modal analysis was applied periodically to the beam in order to study the variation of modal parameters during the tests and the stresses were estimated combining a numerical model and the acceleration modal coordinates measured at discrete points of the structure. The experimental results are compared with those predicted applying the S-N model of Eurocode 3. Findings A methodology that combines a finite element model and the experimental responses of a structure has been applied to estimate the stress time histories of a cantilever beam clamped to a foundation through a steel plate. The estimated stresses have been used to predict the fatigue damage according to the Eurocode 3. Due to the fact that no information of the scatter is provided by this code (EC3), only the number of cycles corresponding to a probability of failure of 5 percent can be predicted. Originality/value The proposed methodology can be applied to real structures in order to know the accumulated fatigue damage in real time.

scholarly journals Novel 2D strain-rate-dependent lamina-based and RVE/phase-based progressive fatigue damage criteria for randomly loaded multi-layer fiber-reinforced composites

2021 ◽  
Vol 16 (59) ◽  
pp. 423-443
Author(s):  
M. Shariyat
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
Fatigue Damage ◽  
Rate Dependence ◽  
Experimental Results ◽  
Life Assessment ◽  
Strain Rate Dependence ◽  
Transverse Load ◽  
2D Strain ◽  
Stress Components

Two implicit progressive fatigue damage models that rely on new equivalent-damage and equivalent-stress criteria are presented for the prediction of various failure modes of the composites. The criteria are coupled with lamina-based and representative-volume-element-based damage progression approaches. The common concepts of residual strength and residual stiffness are revisited and modified. A fatigue life assessment algorithm that incorporates the strain-rate-dependence of the fatigue strengths and stiffnesses, and random and asynchronous changes of the stress components, distinct mean values, and phase shifts of the stress components is employed. New ideas and new post-processing procedures are employed in the current research. It is the first time that the significant impacts of the strain-rate-dependence of the properties of the composites on stress and fatigue life analyses are investigated. Results of the proposed fatigue criteria are first implemented to a composite plate with a complex lamination scheme under a random transverse load and the predicted fatigue lives are verified by the experimental results. Then, these criteria are implemented to a composite chassis frame of an SUV car under realistic random road inputs and the theoretical results are verified by the experimental results. Results confirm the significant role of the strain-rate-dependence effects on the fatigue lives.

Fatigue Life Prediction under Variable Loading Based a Non-Linear Energy Model

2016 ◽  
Vol 22 ◽  
pp. 14-21
Author(s):  
Abdelkader Djebli ◽  
Mostefa Bendouba ◽  
Aid Abdelkarim
Keyword(s):  
Fatigue Life ◽  
Aluminium Alloy ◽  
Fatigue Damage ◽  
Damage Model ◽  
Experimental Results ◽  
Random Loading ◽  
Random Load ◽  
Complex Load ◽  
Proposed Model ◽  
Fatigue Damage Accumulation

A method of fatigue damage accumulation based upon application of energy parameters of the fatigue process is proposed in the paper. Using this model is simple, it has no parameter to be determined, it requires only the knowledge of the curve W–N (W: strain energy density N: number of cycles at failure) determined from the experimental Wöhler curve. To examine the performance of nonlinear models proposed in the estimation of fatigue damage and fatigue life of components under random loading, a batch of specimens made of 6082 T6 aluminium alloy has been studied and some of the results are reported in the present paper. The paper describes an algorithm and suggests a fatigue cumulative damage model, especially when random loading is considered. This work contains the results of uni-axial random load fatigue tests with different mean and amplitude values performed on 6082 T6 aluminium alloy specimens. The proposed model has been formulated to take into account the damage evolution at different load levels and it allows the effect of the loading sequence to be included by means of a recurrence formula derived for multilevel loading, considering complex load sequences. It is concluded that a ‘damaged stress interaction damage rule’ proposed here allows a better fatigue damage prediction than the widely used Palmgren–Miner rule, and a formula derived in random fatigue could be used to predict the fatigue damage and fatigue lifetime very easily. The results obtained by the model are compared with the experimental results and those calculated by the most fatigue damage model used in fatigue (Miner’s model). The comparison shows that the proposed model, presents a good estimation of the experimental results. Moreover, the error is minimized in comparison to the Miner’s model.

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