Critical damage degree model of spall fracture in ductile metals

2021 ◽  
Vol 130 (12) ◽  
pp. 125105
Author(s):  
Hao Zhang ◽  
Hui Peng ◽  
Xiaoyang Pei ◽  
Songlin Yao ◽  
Hongliang He ◽  
...  
Keyword(s):  
Spall Fracture ◽  
Ductile Metals ◽  
Damage Degree ◽  
Critical Damage

Percolation-Relaxation Model with Critical Damage for Describing the Dynamic Tensile Spall of Ductile Metals

2006 ◽  
Vol 324-325 ◽  
pp. 121-124 ◽  
Author(s):  
Yong Gang Wang ◽  
Hong Liang He ◽  
Li Li Wang ◽  
Fu Qian Jing
Keyword(s):  
Stress Relaxation ◽  
Void Growth ◽  
Percolation Theory ◽  
Constitutive Relations ◽  
Void Coalescence ◽  
Relaxation Model ◽  
Coalescence Process ◽  
Ductile Metals ◽  
Coalescence Model ◽  
Critical Damage

In the framework of percolation theory, a simple void-coalescence model combined with the constitutive relations for describing the stress relaxation and material softening during the void-coalescence process, name as the percolation-relaxation (P-R) model, is proposed to describe the dynamic tensile spallation of ductile metals. A critical damage is introduced and coupled into the model to identify the onset of the void coalescence. Mesoscopically, the critical damage corresponds to the critical intervoid ligament distance (ILD), indicating the start of transition from the void-growth to the void-coalescence.

Critical Damage Evolution model for spall failure of ductile metals

2013 ◽  
Vol 56 ◽  
pp. 131-141 ◽  
Author(s):  
Yonggang Wang ◽  
Hongliang He ◽  
Lili Wang
Keyword(s):  
Damage Evolution ◽  
Evolution Model ◽  
Ductile Metals ◽  
Critical Damage ◽  
Spall Failure

scholarly journals A fracture criterion for ductile metals based on critical damage parameters

2020 ◽  
Author(s):  
Michael Brünig ◽  
Marco Schmidt ◽  
Steffen Gerke
Keyword(s):  
Stress State ◽  
Fracture Criterion ◽  
Evolution Equations ◽  
Damage Model ◽  
Strain Tensor ◽  
Ductile Metals ◽  
Fracture Modes ◽  
Damage And Fracture ◽  
Damage Condition ◽  
Critical Damage

Abstract The paper deals with the effect of different stress-state-dependent damage mechanisms on the onset of fracture in ductile metals. A continuum damage model is discussed using a strain tensor as an appropriate damage variable. It takes into account the influence of stress state on the damage condition and on the evolution equations of damage strains. A fracture condition based on critical damage parameters is developed analyzing results of a series of new experiments with different biaxially loaded specimens. After the tests, fracture modes are visualized by scanning electron microscopy. Numerical simulations of the biaxial experiments elucidate the stress states in critical regions of the specimens which are used to explain formation of different damage and fracture modes on the micro-level. Analysis of numerically predicted damage strains for different loading cases leads to a generalized fracture criterion.

scholarly journals Damage Ratio Based on Statistical Damage Constitutive Model for Rock

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Ying Chen ◽  
Lin Zhang ◽  
Hui Xie ◽  
Jianfeng Liu ◽  
Hong Liu ◽  
...  
Keyword(s):  
Rock Mass ◽  
Constitutive Model ◽  
Damage Mechanics ◽  
Damage Index ◽  
Confining Pressure ◽  
Peak Strain ◽  
Rock Damage ◽  
Damage Degree ◽  
Damage Constitutive Model ◽  
Critical Damage

The study of damage characteristics of rock mass is of great significance to the analysis of rock mass structure. According to the characteristics of the microscopic unit strength of rock with random distribution, the Weibull distribution is widely used as the statistical functions of the strength of the microunit of rock to establish the damage constitutive model. The concepts of damage ratio De and damage index Cc are proposed. Damage ratio is mainly used to describe the law of damage evolution in rock. Damage index can be used to evaluate the damage degree of rock. The influence of confining pressure on distribution parameters and damage ratio is analyzed through uniaxial and triaxial compression tests of sandstone. The results show that damage ratio is an index of structural characteristics of rock damage, which can reflect the evolution characteristics of microcracks in rock under spatial stress. Critical damage ratio refers to the damage ratio corresponding to the peak stress of rock and can be used as a parameter to characterize the strength of rock for corresponding to the peak strain one to one. The critical damage ratio is linearly related to the logarithmic function of confining pressure. Its relationship is as follows: Der=Ccln⁡σ3+b. With the increase of σ3, the increasing trend of Der slows down and gradually tends to a certain value. The larger the damage index is, the more serious the damage of rock is. The smaller the damage index is, the less serious the damage of rock is. Therefore, the damage index can be used to evaluate the damage degree of rock. It will be an important direction of rock damage mechanics research to distinguish the severity of rock damage by using damage index as the limit value.

ALLOCATION OF SOURCES AND DONORS OF ECONOMICALLY VALUABLE TRAITS FROM THE COLLECTION MATERIAL OF CUCUMBER TO CREATE HIGHLY PRODUCTIVE VARIETIES AND HYBRIDS

1970 ◽  
pp. 45-49
Author(s):  
N. V. Kulyakina ◽  
G. A. Kuzmitskaya ◽  
T. K. Yurechko
Keyword(s):  
Genetic Resources ◽  
Downy Mildew ◽  
Geographical Origin ◽  
Plant Genetic Resources ◽  
Eastern Region ◽  
Biotic And Abiotic Stress ◽  
Climate Conditions ◽  
Damage Degree ◽  
Economically Valuable Traits ◽  
Far Eastern

The downy mildew (peronosporosis) is the most dangerous and harmful cucumber disease in the Far-Eastern region. Its harmfulness is the highest during the period of flowering – fruiting, because it may completely ruin the cucumber plants both in open and protected ground. Use of cucumber sorts with effective genes that are resistant to the disease is the most efficient way to fight cucumber peronosporosis. In this connection the publication adduces the facts of study the sorts and hybrids of different ecological and geographical origin from the genetic resources collection of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR) in comparison with three zoned sorts of DV NIISH selection – Mig, Khabar, Amurchonok. The aim of researches – to identify the sort samples cucumber according to the main economically valuable traits and also to the degree resistance of genetypes to the main disease of the culture in the region – downy mildew (peronosporosis), for allow to select the source material for the creation of sorts and hybrids, highly productive and resistant to biotic and abiotic stress environmental factors in the monsoon climate conditions of Khabarovsk region. The perspective genetypes having both the resistance to the diseases and productivity are not revealed as a result of the evaluation of the collection of cucumber samples according to their susceptibility by fungus diseases and productivity. Slavyanskiy (Belarus) is more resistant to peronosporosis, especially in 2016 year conditions, although it was inferior to the damage degree of disease to the zoned sorts – Mig, Khabar, Amurchonok. This perspective sample is planned to be used as a source of donors of the main economically valuable traits in a further selective work.

Comparison of corrosion resistance properties of Ni-P and Ni-W-P coatings obtained by electroless deposition

2020 ◽  
Vol 25 (2) ◽  
pp. 66-71
Author(s):  
A.B. Drovosekov
Keyword(s):  
Corrosion Resistance ◽  
Sulfuric Acid ◽  
Electroless Deposition ◽  
Corrosion Damage ◽  
Electrochemical Activity ◽  
High Porosity ◽  
Environment Analysis ◽  
Damage Degree ◽  
Lower Porosity ◽  
Electroless Coatings

Corrosion resistance properties, such as porosity, stability in the atmosphere of NaCl mist, and anodic electrochemical activity in a sulfuric acid solution are studied and compared for Ni-W-P and Ni-P coatings obtained by electroless deposition. The studied coatings were obtained from solutions with glycine as the main ligand and contained 10.2 to 15.6 at.% of phosphorus and up to 3.3 at.% of tungsten. It is shown that Ni-W-P coatings with a tungsten content of 2.3 to 3.3 at.% and a thickness of 15 μm have a significantly lower porosity as compared with nickel-phosphorus coatings of the same thickness. Also, significantly better stability of Ni-W-P coatings in a NaCl mist atmosphere was observed, their corrosion damage degree is less than that of Ni-P coatings, and relatively little depends on the duration of exposure in a corrosive environment. Analysis of anodic polarization curves showed an almost similar electrochemical activity upon dissolution of Ni-P and Ni-W-P coatings in sulfuric acid. Both these types of electroless coatings showed a markedly better tendency to anodic dissolution than pure nickel. Taking into account the obtained experimental data, a conclusion is made as to the better protective characteristics of Ni-W-P coatings in comparison with nickel-phosphorus coatings. The main reason of the inferior protective properties of Ni-P coatings is their relatively high porosity.

Phenomenon of Spall Fracture during Tension

2020 ◽  
Vol 2020 (10) ◽  
pp. 1230-1234
Author(s):  
A. V. Grinevich ◽  
A. V. Slavin ◽  
N. O. Yakovlev ◽  
I. V. Gulina
Keyword(s):  
Spall Fracture

scholarly journals A Fusion Algorithm for Online Reliability Evaluation of Microgrid Inverter IGBT

Electronics ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1294 ◽  
Author(s):  
Chuankun Wang ◽  
Yigang He ◽  
Chenyuan Wang ◽  
Xiaoxin Wu ◽  
Lie Li
Keyword(s):  
Aging Process ◽  
Short Term Memory ◽  
Coupling Model ◽  
Reliability Evaluation ◽  
Junction Temperature ◽  
Stable Operation ◽  
Practical Case ◽  
Fusion Algorithm ◽  
Insulated Gate Bipolar Transistor ◽  
Damage Degree

Due to the diversity of distributed generation sources, microgrid inverters work under complex and changeable conditions. The core device of inverters, an insulated gate bipolar transistor (IGBT), bears a large amount of thermal stress impact, so its reliability is related to the stable operation of the microgrid. The effect of the IGBT aging process cannot be considered adequately with the existing reliability evaluation methods, which have not yet reached the requirements of online evaluation. This paper proposes a fusion algorithm for online reliability evaluation of microgrid inverter IGBT, which combines condition monitoring and reliability evaluation. Firstly, based on the microgrid inverter topology and IGBT characteristics, an electrothermal coupling model is established to obtain junction temperature data. Secondly, the segmented long short-term memory (LSTM) algorithm is studied, which can accurately predict the aging process of the IGBT and judge the aging state via the limited monitoring data. Then, the parameters of the electrothermal coupling model are corrected according to the aging process. Besides, the fusion algorithm is applied to the practical case. Finally, the data comparison verifies the feasibility of the fusion algorithm, whose cumulative damage degree and estimated life error are 5.10% and 5.83%, respectively.

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