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.

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 Evaluation of Damage Process of a Coating by Using Nonlinear Ultrasonic Method

Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 440
Author(s):  
Chunguang Xu ◽  
Lei He ◽  
Shiyuan Zhou ◽  
Dingguo Xiao ◽  
Pengzhi Ma
Keyword(s):  
Tensile Stress ◽  
Order Parameter ◽  
Evaluation Method ◽  
Early Stage ◽  
Ultrasonic Method ◽  
Nonlinear Coefficient ◽  
Damage Index ◽  
Second Order ◽  
External Loading ◽  
Nonlinear Ultrasonic

During the service or external loading of the surface coating, the damage accumulation may develop in the coating or at the interface between the substrate and the coating, but it is difficult to measure directly in the early stage, so the acoustic nonlinear parameters are used as the early damage index of the coating. In this paper, the nonlinear wave motion equation is solved by the perturbation method and the new relationship between the relative ratio of second-order parameter and third-order parameter was derived. The nonlinear ultrasonic testing system is used to detect received signals during tensile testing of for the specimen with Al2O3 coatings. It is found that when the stress is less than 260 MPa, the appearance of the coating has no obvious change, but the nonlinear coefficients measured by the experiment increase with the increase of the tensile stress. By comparing the curves of nonlinear coefficients and stress respectively, the fluctuation of curves the second-order nonlinear coefficient A2 and the relative nonlinear coefficient β′ to stress is relatively small, and close to the linear relationship with the tensile stress, which indicates that the two parameters of the specimen with Al2O3 coatings are more sensitive to the bonding conditions, and can be used as an evaluation method to track the coating damage.

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.

Metal Surface Fatigue Detection Using Nonlinear Ultrasonic

2014 ◽  
Vol 510 ◽  
pp. 156-162 ◽  
Author(s):  
Hong Juan Yan ◽  
Chun Guang Xu ◽  
Qi Lin ◽  
Hai Chao Cai
Keyword(s):  
Fatigue Life ◽  
Nonlinear Coefficient ◽  
304 Stainless Steel ◽  
2024 Aluminum Alloy ◽  
Surface Fatigue ◽  
Micro Cracks ◽  
Nonlinear Ultrasonic ◽  
Ultrasonic Propagation ◽  
Fatigue Detection ◽  
The Relationship

Based on theory of ultrasonic nondestructive testing on surface fatigue damage of metal components, the wave law of ultrasonic nonlinearity caused by fatigue is studied. When there are lattice defects in metal material, second-order nonlinear coefficient β changes during ultrasonic propagation. According to the point, the system of nonlinear ultrasonic testing is build. The change trends of harmonic amplitudes and ultrasonic coefficients are measured during fatigue bending testing of materials such as 45 steel, 2024 aluminum alloy and 304 stainless steel. The results shows: in elastic phase, the ratios of harmonic and fundamental waves monotonically increase with fatigue life, and in plastic phase, deformations appear and micro-cracks expand into macro-cracks in materials, the ratios firstly decrease and then increase with fatigue life. However the quadratic sums of nonlinear coefficient are approximately linear with the fatigue life. Therefore, when the relationship between the quadratic sums and fatigue life is known, it can be used to characterize fatigue state of metal materials.

Micro-cracking monitoring and fracture evaluation for crumb rubber concrete based on acoustic emission techniques

2017 ◽  
Vol 17 (4) ◽  
pp. 946-958 ◽  
Author(s):  
Jie Xu ◽  
Zhengwu Fu ◽  
Qinghua Han ◽  
Giuseppe Lacidogna ◽  
Alberto Carpinteri
Keyword(s):  
Acoustic Emission ◽  
Evaluation Method ◽  
Early Stage ◽  
Damping Ratio ◽  
Crumb Rubber ◽  
Acoustic Emission Technique ◽  
Statistical Parameters ◽  
Micro Cracks ◽  
Crumb Rubber Concrete ◽  
Rubber Concrete

A micro-cracking monitoring and fracture evaluation method for crumb rubber concrete based on the acoustic emission technique was developed. The precursory micro-cracking activity and fracture behavior of crumb rubber concrete with different rubber contents, 0%, 10%, and 15%, were analyzed. The various acoustic emission statistical parameters including cumulative event, frequency distribution, amplitude distribution, and b-value were used for the analysis. The general fracture process is similar for all normal and crumb rubber concretes and can be divided into three distinct stages of micro-crack activity, namely, early stage, main collapse stage, and post-fracture stage. The following conclusions were drawn from the analysis: (1) more micro-cracks initiated and grew at early stage in the normal concrete, while less micro-cracks in the crumb rubber concrete but with longer stage duration; (2) the duration and crack number are both increasing with the increase in the rubber contents in main collapse and post-fracture stages; (3) new crack types associated with the rubber particles were recorded due to the change of the peak frequencies; and (4) the amplitude of the cracks decrease with the increase in the rubber content due to the damping ratio and interface improvement by the mixed rubbers. The results obtained in this article demonstrate that the acoustic emission technique can provide valuable information for a better understanding of micro-cracking and fracture monitoring of crumb rubber concrete.

Creep-Fatigue Damage and Life Evaluation for Boiler Header Stub Weldment

2002 ◽  
Author(s):  
Takuya Ito ◽  
Isamu Nonaka ◽  
Hideo Umaki ◽  
Hidetaka Nishida ◽  
Shizuma Shintani
Keyword(s):  
Fatigue Damage ◽  
Early Stage ◽  
Crack Depth ◽  
Prediction Method ◽  
Fatigue Tests ◽  
Short Cracks ◽  
Micro Cracks ◽  
Creep Fatigue ◽  
Damage Process ◽  
Maximum Crack

In order to clarify the creep-fatigue damage process and to evaluate the creep-fatigue life for boiler 2.25Cr-1Mo header stub welds, a series of creep-fatigue tests were performed on partial mock-up specimens of actual plant under simulated plant loading conditions. Creep voids and micro-cracks occurred along the weld toes at an early stage of life and grew to form many short cracks. These short cracks grew both on the surface and through the wall of the stub tube and later coalesced to form one crack. It was proved that there was a correlation between the maximum crack depth and life ratio and also that there was a correlation between the maximum crack depth and the maximum crack length on the surface. A life prediction method was proposed based on these two correlations.

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.

Plastic Slip and Early Stage of Fatigue Damage in Polycrystals: Comparison between Experiments and Crystal Plasticity Finite Elements Simulations

2014 ◽  
Vol 891-892 ◽  
pp. 1711-1716 ◽  
Author(s):  
Loic Signor ◽  
Emmanuel Lacoste ◽  
Patrick Villechaise ◽  
Thomas Ghidossi ◽  
Stephan Courtin
Keyword(s):  
Fatigue Crack ◽  
Finite Elements ◽  
Crack Initiation ◽  
Fatigue Damage ◽  
Crystal Plasticity ◽  
Early Stage ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Plastic Slip

For conventional materials with solid solution, fatigue damage is often related to microplasticity and is largely sensitive to microstructure at different scales concerning dislocations, grains and textures. The present study focuses on slip bands activity and fatigue crack initiation with special attention on the influence of the size, the morphology and the crystal orientation of grains and their neighbours. The local configurations which favour - or prevent - crack initiation are not completely identified. In this work, the identification and the analysis of several crack initiation sites are performed using Scanning Electron Microscopy and Electron Back-Scattered Diffraction. Crystal plasticity finite elements simulation is employed to evaluate local microplasticity at the scale of the grains. One of the originality of this work is the creation of 3D meshes of polycrystalline aggregates corresponding to zones where fatigue cracks have been observed. 3D data obtained by serial-sectioning are used to reconstruct actual microstructure. The role of the plastic slip activity as a driving force for fatigue crack initiation is discussed according to the comparison between experimental observations and simulations. The approach is applied to 316L type austenitic stainless steels under low-cycle fatigue loading.

Effect of Rotational Stiffness Evolution at Crack Part on Critical Crack Size in SFR

2012 ◽  
Author(s):  
Takashi Wakai ◽  
Hideo Machida ◽  
Shinji Yoshida
Keyword(s):  
Evaluation Method ◽  
Large Diameter ◽  
Crack Size ◽  
Evolution Model ◽  
Piping System ◽  
Rotational Stiffness ◽  
Critical Crack ◽  
Rotational Spring Model ◽  
Size Evaluation ◽  
Critical Crack Size

This paper describes the efficiency of the deployment of rotational stiffness evolution model in the critical crack size evaluation for Leak Before Break (LBB) assessment of Sodium cooled Fast Reactor (SFR) pipes. The authors have developed a critical crack size evaluation method for the thin-walled large diameter pipe made of modified 9Cr-1Mo steel. In this method, since the SFR pipe is mainly subjected to displacement controlled load caused by thermal expansion, the stress at the crack part is estimated taking stiffness evolution due to crack into account. The stiffness evolution is evaluated by using the rotational spring model. In this study, critical crack sizes for several pipes having some elbows were evaluated and discuss about the effect of the deployment of the stiffness evolution model at the crack part on critical crack size. If there were few elbows in pipe, thermal stress at the crack part was remarkably reduced by considering the stiffness evolution. In contrast, in the case where the compliance of the piping system was small, the critical crack size could be estimated under displacement controlled condition. As a result, the critical crack size increases by employing the model and LBB range may be expected to be enlarged.

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