Damage evaluation for the dispersed microdefects with the aid of M-integral

2018 ◽  
Vol 28 (5) ◽  
pp. 647-663 ◽  
Author(s):  
JunNan Lv ◽  
WenJie Zhu ◽  
Qun Li
Keyword(s):  
Damage Evolution ◽  
Evolution Rate ◽  
Damage Evaluation ◽  
Engineering Structures ◽  
Damage Level ◽  
Damage Area ◽  
Total Potential ◽  
Actual Damage ◽  
Fatigue Driving ◽  
M Integral

A unified method of evaluating the dispersed microdefects’ equivalent damage area/volume is innovatively proposed by using the M-integral. The corresponding damage evolution rate and fatigue driving force is preliminarily studied for the dispersed microdefects. First, the analytical expression of M-integral is deduced by using the Lagrangian energy density function (Λ), and the corresponding physical meaning of the M-integral is elucidated as the change of the total potential energy due to the damage evolution. Second, the actual damage area/volume induced by underlying dispersed microdefects are assumed equivalent to the area/volume of an individual circular/spherical void while the corresponding values of the M-integral for both cases are equal. As examples, the equivalent damage area associated with the M-integral for a series of representative defect(s) configurations is calculated, including the singular defect (void, crack, and ellipse) and the interactive defects (two voids, two cracks, one void, and one crack). The influences of the defects interaction effect and distribution on the damage level are analyzed quantitatively. Finally, the present method of damage evaluation is proposed to predict fatigue problems of the dispersed defects. A unified fatigue damage evolution law for the dispersed microdefects is preliminarily defined, and a protocol to experimentally measure the damage evolution rate is proposed. The present research will be beneficial to the damage tolerance design and lifetime prediction of engineering structures with dispersed microdefects.

An Effective Damage Evaluation Method for Crane Girder Based on SVI and LSSVM

2014 ◽  
Vol 602-605 ◽  
pp. 370-374
Author(s):  
Hong Bo Xu ◽  
Jia Yu Li
Keyword(s):  
Evaluation Method ◽  
Damage Identification ◽  
Health Assessment ◽  
Support Vector ◽  
Damage Evaluation ◽  
Damage Level ◽  
Variation Index ◽  
Stiffness Variation ◽  
Actual Damage

Health assessment of the girder is crucial to an overhead traveling crane. This paper presents an intelligent damage identification method for the girder based on stiffness variation index (SVI) and least squares support vector machine (LSSVM). In the method, the SVI indicators, which have high resolution to environmental noise, serve as the damage feature to detect damage locations. Moreover, the SVI indicators are input to the LSSVM classifier for identifying the actual damage level of the girder. A case study on girder damage identification demonstrates that the method could determine the actual conditions of the girder structure accurately.

The M-Integral Description for a Brittle Plane Strip With Two Cracks Before and After Coalescence

2009 ◽  
Vol 76 (6) ◽  
Author(s):  
Hu Yi-Feng ◽  
Chen Yi-Heng
Keyword(s):  
New York ◽  
Nondestructive Evaluation ◽  
Brittle Material ◽  
Damage Evolution ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Release Rates ◽  
Before And After ◽  
Energy Release Rates ◽  
M Integral

In this paper we extend the M-integral concept (Eshelby, J. D., 1956, The Continuum Theory of Lattice Defects, Solid State Physics, F. Seitz and D. Turnbull, eds., Academic, New York, pp. 79–141; Eshelby, J. D., 1970, The Energy Momentum Tensor in Continuum Mechanics, Inelastic Behavior of Solids, M. F. Kanninen, ed., McGraw-Hill, New York, pp. 77–115; Eshelby, J. D., 1975, “The Elastic Energy-Momentum Tensor,” J. Elast., 5, pp. 321–335; Knowles, J. K., and Sternberg, E., 1972, “On a Class of Conservation Laws in Linearized and Finite Elastostatics,” Arch. Ration. Mech. Anal., 44, pp. 187–211; Budiansky, B., and Rice, J. R., 1973, “Conservation Laws and Energy Release Rates,” ASME J. Appl. Mech., 40, pp. 201–203; Freund, L. B., 1978, “Stress Intensity Factor Calculations Based on a Conservation Integral,” Int. J. Solids Struct., 14, pp. 241–250; Herrmann, G. A., and Herrmann, G., 1981, “On Energy Release Rates for a Plane Cracks,” ASME J. Appl. Mech., 48, pp. 525–530; King, R. B., and Herrmann, G., 1981, “Nondestructive Evaluation of the J- and M-Integrals,” ASME J. Appl. Mech., 48, pp. 83–87) to study the degradation of a brittle plan strip caused by irreversible evolution: the cracks coalescence under monotonically increasing loading. Attention is focused on the change of the M-integral before and after coalescence of two neighborly located cracks inclined each other. The influences of different orientations of the two cracks and different coalescence paths connecting the two cracks on the M-integral are studied in detail. Finite element analyses reveal that different orientations of the two cracks lead to different critical values of the M-integral at which the coalescence occurs. It is concluded that the M-integral does play an important role in the description of the damage extent and damage evolution. However, it only provides some outside variable features. This means that the complete failure mechanism due to damage evolution cannot be governed by a single parameter MC as proposed by Chang and Peng, 2004, “Use of M integral for Rubbery Material Problems Containing Multiple Defects,” J. Eng. Mech., 130(5), pp. 589–598. It is found that there is an inherent relation between the M-integral and the reduction of the effective elastic moduli as the orientation of one crack varies, i.e., the larger the M-integral is, the larger the reduction is. Of great significance is that the M-integral is inherently related to the change of the total potential energy for a damaged brittle material regardless of the detailed damage features or damage evolution. Therefore, this provides a useful and convenient experimental technique to measure the values of M-integral for a damaged brittle material from initial damage to final failure without use of many stain gages (King, R. B., and Herrmann, G., 1981, “Nondestructive Evaluation of the J- and M-Integrals,” ASME J. Appl. Mech., 48, pp. 83–87).

scholarly journals A Strain Rate-Dependent Damage Evolution Model for Concrete Based on Experimental Results

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Bin Xu ◽  
Xiaoyan Lei ◽  
P. Wang ◽  
Hui Song
Keyword(s):  
Strain Rate ◽  
Uniaxial Compression ◽  
Damage Evolution ◽  
Damage Model ◽  
Evolution Model ◽  
Experimental Results ◽  
Strain Rates ◽  
Compression Tests ◽  
Stress Strain ◽  
Actual Damage

There are various definitions of damage variables from the existing damage models. The calculated damage value by the current methods still could not well correspond to the actual damage value. Therefore, it is necessary to establish a damage evolution model corresponding to the actual damage evolution. In this paper, a strain rate-sensitive isotropic damage model for plain concrete is proposed to describe its nonlinear behavior. Cyclic uniaxial compression tests were conducted on concrete samples at three strain rates of 10−3s−1, 10−4s−1, and 10−5s−1, respectively, and ultrasonic wave measurements were made at specified strain values during the loading progress. A damage variable was defined using the secant and initial moduli, and concrete damage evolution was then studied using the experimental results of the cyclic uniaxial compression tests conducted at the different strain rates. A viscoelastic stress-strain relationship, which considered the proposed damage evolution model, was presented according to the principles of irreversible thermodynamics. The model results agreed well with the experiment and indicated that the proposed damage evolution model can accurately characterize the development of macroscopic mechanical weakening of concrete. A damage-coupled viscoelastic constitutive relationship of concrete was recommended. It was concluded that the model could not only characterize the stress-strain response of materials under one-dimensional compressive load but also truly reflect the degradation law of the macromechanical properties of materials. The proposed damage model will advance the understanding of the failure process of concrete materials.

The Complementary Nature of Electron Microscopy and ION Channeling for the Assessment of Radiation Damage Evolution in Ceramics

1998 ◽  
Vol 4 (S2) ◽  
pp. 558-559
Author(s):  
K. E. Sickafus
Keyword(s):  
Damage Evolution ◽  
Ion Irradiation ◽  
Ion Beam ◽  
Quantitative Measure ◽  
Heavy Ion ◽  
Damage Parameter ◽  
Irradiation Damage ◽  
Damage Level ◽  
Ion Channeling ◽  
Typical Experiment

In ion irradiation damage studies on ceramics, damage evolution is often assessed using Rutherford backscattering spectroscopy and ion channeling (RBS/C) techniques. In a typical experiment, a single crystal ceramic sample is irradiated with heavy ions and then the crystal is exposed to He ions along a low-index crystallographic orientation. Simultaneously, the backscattered He ion yield is measured as a function of ion energy loss. For He ions scattered from the heavy ion irradiated volume, the He ion yield increases in proportion to the heavy ion dose. The RBS/C yield rises because the He ion beam is dechanneled by, for instance, interstitial point defects and clusters and their associated strain fields. A quantitative measure of dechanneling is denoted by χmin, defined as the ratio of the He ion yield along a low-index crystal orientation, to the yield obtained in a random (non-channeling) orientation. The damage parameter xmin varies from 0 to 1, where 1 represents the maximum damage level that can be measured by RBS/C.

Elastic–plastic-damage model of nano-indentation of the ion-irradiated 6061 aluminium alloy

2020 ◽  
Vol 29 (8) ◽  
pp. 1271-1305
Author(s):  
A Ustrzycka ◽  
B Skoczeń ◽  
M Nowak ◽  
Ł Kurpaska ◽  
E Wyszkowska ◽  
...  
Keyword(s):  
Damage Evolution ◽  
Damage Mechanics ◽  
Ion Irradiation ◽  
Damage Model ◽  
Indentation Test ◽  
Gtn Model ◽  
Damage Level ◽  
Nano Indentation ◽  
Wide Range ◽  
Radiation Induced

The paper presents experimental and numerical characterization of damage evolution for ion-irradiated materials subjected to plastic deformation during nano-indentation. Ion irradiation technique belongs to the methods where creation of radiation-induced defects is controlled with a high accuracy (including both, concentration and depth distribution control), and allows to obtain materials having a wide range of damage level, usually expressed in terms of displacements per atom (dpa) scale. Ion affected layers are usually thin, typically less than 1 micrometer thick. Such a low thickness requires to use nano-indentation technique to measure the mechanical properties of the irradiated layers. The He or Ar ion penetration depth reaches approximately 150 nm, which is sufficient to perform several loading-partial-unloading cycles at increasing forces. Damage evolution is reflected by the force-displacement diagram, that is backed by the stress–strain relation including damage. In this work the following approach is applied: dpa is obtained from physics (irradiation mechanisms), afterwards, the radiation-induced damage is defined in the framework of continuum damage mechanics to solve the problem of further evolution of damage fields under mechanical loads. The nature of radiation-induced damage is close to porosity because of formation of clusters of vacancies. The new mathematical relation between radiation damage (dpa) and porosity parameter is proposed. Deformation process experienced by the ion irradiated materials during the nano-indentation test is then numerically simulated by using extended Gurson–Tvergaard–Needleman (GTN) model, that accounts for the damage effects. The corresponding numerical results are validated by means of the experimental measurements. It turns out, that the GTN model quite successfully reflects closure of voids, and increase of material density during the nano-indentation.

scholarly journals TREE STRATIFICATION BASED ON ERUPTION DAMAGE LEVEL IN MOUNT MERAPI NATIONAL PARK YOGYAKARTA INDONESIA

2021 ◽  
Vol 26 (1) ◽  
pp. 71-81
Author(s):  
Inggita Utami ◽  
Radhitiya Anjar Pramana Putra ◽  
Muhammad Saputra Wibowo ◽  
Febriant Isabella Yusuf ◽  
Fahmiatul Husna ◽  
...  
Keyword(s):  
National Park ◽  
Tree Height ◽  
Tree Density ◽  
Forest Damage ◽  
Secondary Forests ◽  
Damage Level ◽  
Damage Area ◽  
Vegetation Parameters ◽  
Maximum Tree Height ◽  
Heavy Damage

Mount Merapi’s eruption has caused damage to the forests in the Mount Merapi National Park (MMNP). Nine years after the eruption, the vertical structure of vegetation can illustrate the progress of succession. This study aimed to analyze the tree composition and stratification in different forest damage levels after the 2010 Merapi eruption. The study was conducted in March 2019 at three stations, namely station A (heavy damage area), station B (moderate damage area), and station C (minor damage area). Vegetation parameters in each station were taken in a 10x100 plot and were processed using a tree profile diagram. Abiotic parameters were measured in each plot and analyzed using the correlation test. The results showed that the three stations were still dominated by the tree in Stratum C, but the tree density and tree height varied in proportion to the damage level. Station A in the heavy damage area has the lowest tree density (23 trees/0.1 ha) with a maximum tree height of 12 meters, in contrast to Station C in the minor damage area with tree density reaching 195 trees/0.1 ha and maximum tree height reaching 30 meters. Nine years after the Mount Merapi big eruption, the MMNP forests in Yogyakarta Province are still classified as young secondary forests.  Key words: diagram, profile, succession, structure, vertical

scholarly journals EVALUATION OF THE SEISMIC INERTIA FORCES ON THE ACTUAL DAMAGE OF BRIDGES

2020 ◽  
pp. 28-33
Author(s):  
T. Kalachuk ◽  
I. Kolmykova ◽  
E. Shin
Keyword(s):  
Working Conditions ◽  
Dynamic Theory ◽  
Practical Interest ◽  
Seismic Resistance ◽  
Engineering Structures ◽  
Strong Earthquakes ◽  
Spectral Curves ◽  
Actual Damage ◽  
Seismic Forces ◽  
Inertia Forces

because of the constant threat of earthquakes in seismic hazardous areas, it is necessary to study the issues of seismic resistance of structures and development of methods of their design, taking into account the seismic factor. A significant share in the total volume of engineering structures permanent and built on canals and roads is occupied by artificial structures, such as aqueducts, small and medium bridges (overpasses). In this regard, the provision of seismic resistance of these structures is of practical interest. Buildings and structures located in seismic areas are affected by factors that cause the occurrence of seismic forces and changes in the working conditions of structures during earthquakes The article presents the results of comparison of calculations in the dynamic theory (by the method of spectral curves) and static seismic coefficient determination with the actual data on damage to structures in strong earthquakes. A formula for calculating the coefficient of seismicity is proposed.

scholarly journals Statistical Constitutive Model of Thermal Damage for Deep Rock considering Initial Compaction Stage and Residual Strength

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Lingjie Zhu ◽  
Xiaoli Xu ◽  
Xiaojian Cao ◽  
Shaoyong Chen
Keyword(s):  
Constitutive Model ◽  
Residual Strength ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Thermal Damage ◽  
Peak Stress ◽  
Confining Pressure ◽  
Evolution Rate ◽  
Correction Coefficient ◽  
Initial Compaction

From the theory of damage mechanics, based on the Hoek-Brown strength criterion and Weibull distribution law of rock microelement strength, a statistical constitutive model of rock thermal damage is established by using equivalent strain hypothesis, and the theoretical model is modified by considering the compression coefficient and residual strength correction coefficient. The rationality of the modified model is verified by experimental data. The results show that the stress-strain curves of rock can be divided into four stages: initial compaction, stable damage propagation, damage strengthening expansion, and damage failure according to the characteristics of rock damage evolution. The peak stress of rock increases exponentially with the increase of confining pressure, and the maximum damage evolution rate decreases exponentially with the increase of confining pressure, which indicates that confining pressure delays the development of cumulative damage. The peak stress and maximum damage evolution rate of rock decrease exponentially with the increase of temperature, which accelerates the damage of rock. The initial damage of rock is thermal damage caused by temperature, and the damage value increases with the increase of temperature. The revised theoretical curve reflects the characteristics of rock compaction stage and residual strength and improves the coincidence with the experimental curve. The research results provide a reference for the establishment of thermal damage constitutive model of rock in deep engineering.

Air Base Damage Evaluation Using Cloud Barycenter Evaluation Method

2012 ◽  
Vol 430-432 ◽  
pp. 803-807 ◽  
Author(s):  
Cheng Zhang ◽  
Quan Shi ◽  
Tie Lin Liu
Keyword(s):  
Index System ◽  
Damage Assessment ◽  
Evaluation Method ◽  
Evaluation Index System ◽  
Perfect State ◽  
Damage Evaluation ◽  
Base Damage ◽  
Damage Level ◽  
Battle Damage Assessment ◽  
The Index System

Cloud barycenter evaluation method is applied to battle damage assessment for air base on basis of the establishment of the evaluation index system and damage level classification. The index system of battle damage assessment for air base is established and the application step of cloud barycenter evaluation method to air base damage evaluation is analyzed. The battle damage level of air base is achieved using weighted deflection degree which is used to demonstrate the deflection degree between battle damage and its perfect state. The correctness and validity of the proposed method is verified by the calculating result, which provide an efficient way for battle damage assessment.

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