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.

scholarly journals Fatigue Damage Evaluation of Compressor Blade Based on Nonlinear Ultrasonic Nondestructive Testing

2021 ◽  
Vol 9 (12) ◽  
pp. 1358
Author(s):  
Pengfei Wang ◽  
Weiqiang Wang ◽  
Sanlong Zheng ◽  
Bingbing Chen ◽  
Zengliang Gao
Keyword(s):  
Fatigue Damage ◽  
Ultrasonic Testing ◽  
Evaluation Method ◽  
Early Stage ◽  
Nonlinear Coefficient ◽  
Crack Size ◽  
Compressor Blade ◽  
Three Dimensional Model ◽  
Micro Cracks ◽  
Nonlinear Ultrasonic

Nonlinear ultrasonic testing is highly sensitive to micro-defects and can be used to detect hidden damage and defects inside materials. At present, most tests are carried out on specimens, and there are few nonlinear ultrasonic tests for fatigue damage of compressor blades. A vibration fatigue test was carried out on compressor blade steel KMN, and blade specimens with different damage degrees were obtained. Then, the nonlinear coefficients of blade specimens were obtained by nonlinear ultrasonic testing. The results showed that the nonlinear coefficient increased with the increase in the number of fatigue cycles in the early stage of fatigue, and then the nonlinear coefficient decreased. The microstructures were observed by scanning electron microscopy (SEM). It was proven that the nonlinear ultrasonic testing can be used for the detection of micro-cracks in the early stage of fatigue. Through the statistical analysis of the size of the micro-cracks inside the material, the empirical formula of the nonlinear coefficient β and the equivalent crack size were obtained. Combined with the β–S–N three-dimensional model, an evaluation method based on the nonlinear ultrasonic testing for the early fatigue damage of the blade was proposed.

Evaluation of the Fatigue Life in Aluminum Alloy Welded Joint by Nonlinear Ultrasonic Testing

2013 ◽  
Vol 762 ◽  
pp. 673-679
Author(s):  
Tie Gang ◽  
Chu Hao Wan ◽  
Rong Hua Zhu ◽  
Li Bin Zhao
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Ultrasonic Testing ◽  
Welded Joint ◽  
Ultrasonic Waves ◽  
Second Order ◽  
Testing Method ◽  
Nonlinear Ultrasonic ◽  
6N01 Aluminum Alloy

Fatigue is a common phenomenon in welded structures. Prediction of fatigue life of welded joints in-service is still an unsolved puzzle by the conventional linear ultrasonic testing method. However, the nonlinear ultrasonic waves or the acoustic nonlinear signal can provide clear signs of the accumulative fatigue damage in materials, as reported by a number of researchers. Hence, the nonlinear ultrasonic testing method has revealed a tremendous potential for fatigue damage evaluation. This paper presents a study to characterize the fatigue damage using the analysis of the signal characteristics and a new nonlinear parameter. Based on the very high-cycle fatigue testing results for a 6N01 aluminum alloy welded joint, the relationship between the amplitude of the second-order harmonic and fatigue cycling has been established. The nonlinear ultrasonic system test results show that the amplitude of the second-order harmonic increases at the early fatigue stage, with further increase in cyclic loading until reaching a peak. Metallographic examinations show that a fatigue crack will nucleate in the weld joint in the stage as the amplitude reaches the peak value. Finally, theoretical and experimental results confirm that the amplitude of the second-order harmonic is useful for assessing the fatigue life of a 6N01 aluminum alloy welded joint.

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 Numerical Study on Vibration Response and Fatigue Damage of Axial Compressor Blade Considering Aerodynamic Excitation

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1835
Author(s):  
Xi Fu ◽  
Chao Ma ◽  
Jiewei Lin ◽  
Junhong Zhang
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Equivalent Stress ◽  
Axial Compressor ◽  
Compressor Blade ◽  
Torsional Shear ◽  
Fatigue Damage Accumulation ◽  
Fatigue Model

Axial compressor blades with a deformed initial torsion angle caused by aerodynamic excitation resonated at the working speed and changed the rule of fatigue damage accumulation. The fatigue life of a blade has a prediction error, even causing serious flight accidents if the effect of torque causing damage deterioration of the blade fatigue life is neglected. Therefore, in this paper, a uniaxial non-linear fatigue damage model was modified using the equivalent stress with torsional shear stress, and the proposed fatigue model including the torsional moment was used to study the compressor blade fatigue life. Then, the blade numerical simulation model was established to calculate the vibration characteristics under complex loads of airflow excitation and a rotating centrifugal force. Finally, the blade fatigue life under actual working conditions was predicted using the modified fatigue model. The results show that the interaction between centrifugal and aerodynamic loads affects the natural frequency, as the frequencies in modes dominated by bending deformation decreased whereas those dominated by torsional deformation increased. Furthermore, the blade root of the suction surface showed stress concentration, but there is an obvious difference of stress distribution and amplitude between the normal stress and the equivalent stress including torsional shear stress. The additional consideration of the torsional shear stress decreased the predicted fatigue life by 4.5%. The damage accumulation rate changes with the loading cycle, and it accelerates fast for the last 25% of the cycle, when the blade fracture may occur at any time. Thus, the aerodynamic excitation increased the safety factor of blade fatigue life prediction.

scholarly journals Research on Residual Life Estimation Method for KMN Steel Based on Nonlinear Ultrasonic Testing

2021 ◽  
Vol 11 (23) ◽  
pp. 11385
Author(s):  
Pengfei Wang ◽  
Weiqiang Wang ◽  
Sanlong Zheng ◽  
Zengliang Gao
Keyword(s):  
Fatigue Life ◽  
Ultrasonic Testing ◽  
Residual Life ◽  
Fatigue Cracks ◽  
Nonlinear Coefficient ◽  
Estimation Method ◽  
Microscopic Analysis ◽  
Gumbel Distribution ◽  
Micro Cracks ◽  
Nonlinear Ultrasonic

The testing of KMN steel bending fatigue with different cycles was carried out using a nonlinear ultrasonic detector to obtain its nonlinear coefficient. The experimental results show that the nonlinear coefficient first increases and then decreases with an increase in fatigue cycles. The relationship between the propagation of the micro-cracks inside the material and the nonlinear coefficient was researched by microscopic analysis in the dangerous position of the specimens. As the fatigue cycles increase, the microstructure of the specimen gradually deteriorates and cracks occur, which proves that nonlinear ultrasonic detection can be used to characterize the initiation of micro-cracks in the early fatigue stages of the material and that the nonlinear coefficient β of the material can be used to reflect the fatigue damage degree and fatigue life of the interior of the material. An analysis of the numerical statistics of the fatigue cracks inside the specimens was carried out, and the extreme value of fatigue cracks was calculated using the Gumbel distribution. An empirical formula for the nonlinear coefficient and crack growth size of KMN steel was established and then a method for estimating the fatigue life of KMN steel based on nonlinear ultrasonic testing was proposed.

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.

A Procedure to Predict Influence of Acceleration and Damping of Blades Passing Through Critical Speeds on Fatigue Life

2009 ◽  
Author(s):  
J. S. Rao ◽  
Rejin Ratnakar ◽  
S. Suresh ◽  
R. Narayan
Keyword(s):  
Fatigue Life ◽  
Stress Response ◽  
Fatigue Limit ◽  
Fatigue Damage ◽  
Critical Speed ◽  
Turbine Blades ◽  
Peak Stress ◽  
Start Up ◽  
Number Of Cycles ◽  
Peak Value

Turbine Blades suffer fatigue damage when they cross over a critical speed during start up and shut down conditions. The stress response is usually determined from quasi-steady analysis through resonance with an assumed damping. This response above fatigue limit can be divided into several steps to reach the peak value at critical speed and then fall after passing the critical. For a given acceleration of the rotor, one can then determine the number of cycles at each of these stress levels and assess cumulative damage for one crossing. In this paper, the effect of acceleration and damping on the magnitude of peak stress and where it occurs in the vicinity of critical speed is included in determining the damage suffered by a blade while passing through the critical speed.

scholarly journals Investigation of Changes in Fatigue Damage Caused by Mean Load under Block Loading Conditions

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2738
Author(s):  
Roland Pawliczek ◽  
Tadeusz Lagoda
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Strain Curve ◽  
Mean Value ◽  
Fatigue Properties ◽  
Stress Strain ◽  
Reference Case ◽  
Block Loading ◽  
The Mean ◽  
Mean Strain

The literature in the area of material fatigue indicates that the fatigue properties may change with the number of cycles. Researchers recommend taking this into account in fatigue life calculation algorithms. The results of simulation research presented in this paper relate to an algorithm for estimating the fatigue life of specimens subjected to block loading with a nonzero mean value. The problem of block loads using a novel calculation model is presented in this paper. The model takes into account the change in stress–strain curve parameters caused by mean strain. Simulation tests were performed for generated triangular waveforms of strains, where load blocks with changed mean strain values were applied. During the analysis, the degree of fatigue damage was compared. The results of calculations obtained for standard values of stress–strain parameters (for symmetric loads) and those determined, taking into account changes in the curve parameters, are compared and presented in this paper. It is shown that by neglecting the effect of the mean strain value on the K′ and n′ parameters and by considering only the parameters of the cyclic deformation curve for εm = 0 (symmetric loads), the ratio of the total degree of fatigue damage varies from 10% for εa = 0.2% to 3.5% for εa = 0.6%. The largest differences in the calculation for ratios of the partial degrees of fatigue damage were observed in relation to the reference case for the sequence of block n3, where εm = 0.4%. The simulation results show that higher mean strains change the properties of the material, and in such cases, it is necessary to take into account the influence of the mean value on the material response under block loads.

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