Damage Assessment of Specimens Made of Steel 09G2S Exposed to Low-Cycle Fatigue with the Help of Acoustic Emission Monitoring Method

2020 ◽  
Vol 992 ◽  
pp. 964-970 ◽  
Author(s):  
A.S. Valiev ◽  
G. Khalikova ◽  
I.R. Kuzeev
Keyword(s):  
Acoustic Emission ◽  
Damage Accumulation ◽  
Low Cycle Fatigue ◽  
Cyclic Fatigue ◽  
Test Methods ◽  
Raw Material ◽  
Monitoring Method ◽  
Damage Degree ◽  
Daily Change ◽  
Cyclic Impact

Cyclic impact of external parameters on the structure, such as the daily change of temperature, change of operating parameters (pressure, temperature, volumes of loaded raw material) may lead to the brittle fracture of the equipment material with fast propagation of the main crack. In view of this, there is a need to use the nondestructive test methods which allow determining the critical level of damage accumulation. The article considers the pattern of change in properties as a result of low-cyclic loading by studying the parameters of acoustic signal. Changes in acoustic emission (AE) parameters were measured in the process of uniaxial tension of specimens with different degrees of accumulated damage. Upon processing of these AE parameters, stages of damage accumulation in cyclic fatigue were determined. Thus, is was determined that acoustic-emission diagnostics is sensitive to the said changes and may be used for assessment of the damage degree of 09G2S steel specimens.

scholarly journals NUMERICALLY MODELING FATIGUE LIFE OF STRUCTURAL ELEMENTS UNDER THERMAL CYCLIC LOADING

2020 ◽  
Vol 82 (2) ◽  
pp. 168-188
Author(s):  
I.A. Volkov ◽  
L.A. Igumnov ◽  
D.N. Shishulin ◽  
V.A. Eremeev
Keyword(s):  
Plastic Deformation ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Strength Criterion ◽  
Cyclic Fatigue ◽  
Defining Relations ◽  
Damage Degree ◽  
Fatigue Damage Accumulation ◽  
Main Effects

The paper considers processes of fatigue life of materials and structures in the exploitation conditions characterized by multiparametric nonstationary thermal-mechanical effects In the framework of mechanics of damaged media, a mathematical model is developed that describes processes of thermal-plastic deformation and fatigue damage accumulation in materials with degradation according to low- and high-cycle fatigue mechanisms (accounting for their interaction). The model consists of three interconnected parts: relations determining cyclic thermal-plastic behavior of a material, accounting for its dependence on the failure process; equations describing kinetics of fatigue damage accumulation; a strength criterion of the damaged material. The version of the defining relations of thermal plasticity is based on the notion of the yield surface and the principle of orthogonality of the plastic strain rate vector to the yield surface at the loading point and reflects the main effects of the process of cyclic plastic deformation of the material for arbitrarily complex trajectories of combined thermal-mechanical loading. The version of kinetic equations of fatigue damage accumulation is based on introducing a scalar parameter of damage degree and on energy-based principles, and takes into account the main effects of the nucleation, growth and merging of microdefects under arbitrarily complex loading regimes. A generalized form of an evolutionary equation of fatigue damage accumulation in low-cycle and high-cycle fatigue regions is introduced. The condition when the damage degree reaches its critical value is taken as the strength criterion of the damaged material. To assess the reliability and the scope of applicability of the developed defining relations of mechanics of damaged media, processes of thermal-plastic deformation and fatigue damage accumulation have been numerically analyzed, and the numerical results obtained have been compared with the data of full-scale experiments for a particular applied problem. The effect of the dropping frequency of a distillate on thermal cyclic fatigue life of the material of a heated surface of a tube has been numerically analyzed. The computational results for the fatigue damage accumulation processes under thermal pulsed loading are compared with experimental data. It is shown that the developed model describes both qualitatively and, accurately enough for engineering purposes, quantitatively the experimental data and can be effectively used for evaluating thermal-cyclic fatigue life of structures working in the conditions of multiaxial non-proportional regimes of combined thermal-mechanical loading.

Damage accumulation near a hole under low cycle fatigue proceeding from measurements of local deformation response

2020 ◽  
Vol 86 (10) ◽  
pp. 46-55
Author(s):  
S. I. Eleonsky ◽  
Yu. G. Matvienko ◽  
V. S. Pisarev ◽  
A. V. Chernov
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Damage Accumulation ◽  
Stress Ratio ◽  
Low Cycle Fatigue ◽  
Accumulation Process ◽  
Stress Range ◽  
Cycle Fatigue ◽  
Deformation Response

A new destructive method for quantitative determination of the damage accumulation in the vicinity of a stress concentrator has been proposed and verified. Increase of damage degree in local area with a high level of the strain gradient was achieved through preliminary low-cycle pull-push loading of plane specimens with central open holes. The above procedure is performed for three programs at the same stress range (333.3 MPa) and different stress ratio values 0.33, – 0.66 and – 1.0, and vice versa for two programs at the same stress ratio – 0.33 and different stress range 333.3 and 233.3 MPa. This process offers a set of the objects to be considered with different degree of accumulated fatigue damages. The key point of the developed approach consists in the fact that plane specimens with open holes are tested under real operation conditions without a preliminary notching of the specimen initiating the fatigue crack growth. The measured parameters necessary for a quantitative description of the damage accumulation process were obtained by removing the local volume of the material in the form of a sequence of narrow notches at a constant level of external tensile stress. External load can be considered an amplifier enhancing a useful signal responsible for revealing the material damage. The notch is intended for assessing the level of fatigue damage, just as probe holes are used to release residual stress energy in the hole drilling method. Measurements of the deformation response caused by local removing of the material are carried out by electronic speckle-pattern interferometry at different stages of low-cycle fatigue. The transition from measured in-plane displacements to the values of the stress intensity factor (SIF) and the T-stress was carried out on the basis of the relations of linear fracture mechanics. It was shown that the normalized dependences of the stress intensity factor on the durability percentage for the first notch (constructed for four programs of cyclic loading with different parameters), reflect the effect of the stress ratio and stress range of the loading cycle on the rate of damage accumulation. The data were used to obtain the explicit form of the damage accumulation function that quantitatively describes damage accumulation process. The functions were constructed for different stress ratios and stress ranges.

Acoustic emission and X-ray computed microtomography characterization of damage accumulation in a woven Cf/SiC composite

2019 ◽  
Vol 155 ◽  
pp. 109748
Author(s):  
Yudong Xue ◽  
Qinglei Wang ◽  
Jianbao Hu ◽  
Haijun Zhou ◽  
Qingliang Shan ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Damage Accumulation ◽  
X Ray ◽  
Computed Microtomography ◽  
X Ray Computed

Cumulative acoustic emission energy for damage detection in composites reinforced by carbon fibers within low-cycle fatigue regime at various displacement amplitudes and rates

2021 ◽  
pp. 096739112098570
Author(s):  
Mohammad Azadi ◽  
Mohsen Alizadeh ◽  
Seyed Mohammad Jafari ◽  
Amin Farrokhabadi
Keyword(s):  
Acoustic Emission ◽  
Carbon Fibers ◽  
Polymer Matrix Composites ◽  
Low Cycle Fatigue ◽  
Energy Parameter ◽  
Fatigue Tests ◽  
Matrix Cracking ◽  
Matrix Composites ◽  
Cycle Fatigue ◽  
Cumulative Energy

In the present article, acoustic emission signals were utilized to predict the damage in polymer matrix composites, reinforced by carbon fibers, in the low-cycle fatigue regime. Displacement-controlled fatigue tests were performed on open-hole samples, under different conditions, at various displacement amplitudes of 5.5, 6.0, 6.5 and 7.0 mm and also under various displacement rates of 25, 50, 100 and 200 mm/min. After acquiring acoustic emission signals during cycles, two characteristic parameters were used, including the energy and the cumulative energy. Obtained results implied that the energy parameter of acoustic emission signals could be used only for the macroscopic damage, occurring at more than 65% of normalized fatigue cycles under different test conditions. However, the cumulative energy could properly predict both microscopic and macroscopic defects, at least two failure types, including matrix cracking at first cycles and the fiber breakage at last cycles. Besides, scanning electron microscopy images proved initially such claims under all loading conditions.

scholarly journals Statistical Approach for Risk Assessment of Aflatoxin Sampling Plan Used by Manufacturers for Raw Shelled Peanuts

2002 ◽  
Vol 85 (4) ◽  
pp. 925-932 ◽  
Author(s):  
Mark Vandeven ◽  
Thomas Whitaker ◽  
Andy Slate
Keyword(s):  
Test Methods ◽  
Sampling Plan ◽  
Raw Material ◽  
Contamination Level ◽  
Acceptance Probability ◽  
Preparation Methods ◽  
Crop Varieties ◽  
Analytical Test ◽  
Acceptance Sampling Plans ◽  
Methods Analytical

Abstract Processed food manufacturers often use acceptance sampling plans to screen out lots with unacceptable levels of contamination from incoming raw material streams. Sampling plan designs are determined by specifying sample sizes, sample preparation methods, analytical test methods, and accept/reject criteria. Sampling plan performance can be indicated by plotting acceptance probability versus contamination level as an operating characteristic (OC) curve. In practice, actual plan performance depends on the level of contamination in the incoming lot stream. This level can vary considerably over time, among different crop varieties, and among locales. To better gauge plan performance, a method of coupling an OC curve and crop distributions is proposed. The method provides a precise probabilistic statement about risk and can be easily performed with commercial spreadsheet software.

A novel monitoring method of nanosecond laser scribing float glass with acoustic emission

2022 ◽  
Author(s):  
Weinan Liu ◽  
Guojun Zhang ◽  
Yu Huang ◽  
Wenyuan Li ◽  
Youmin Rong ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Float Glass ◽  
Nanosecond Laser ◽  
Monitoring Method ◽  
Laser Scribing
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