Experimental Characterization of the Elastic-Plastic Strain Fields at the Crack Tip Due to Cyclic Loading

1994 ◽  
Vol 116 (2) ◽  
pp. 187-192 ◽  
Author(s):  
N. Ranganathan ◽  
K. Jendoubi ◽  
N. Merah
Keyword(s):  
Cyclic Loading ◽  
Plastic Strain ◽  
Crack Tip ◽  
High Strength ◽  
Elastic Plastic ◽  
Strain Behavior ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Aluminum Alloy 2024

Some mechanical components cease to function satisfactorily, failing either under excessive elastic deformation or extensive plastic yielding. In the case of constrained plastification, the researcher is faced with some difficulties in evaluating plastic and elastic-plastic strain behavior near the crack tip. In the present study local strains are measured by microstrain gages, mounted near the crack tip on CT specimens made from the high strength aluminum alloy 2024-T351 under cyclic loading at constant ΔK. The behavior and the evolution of the elastic-plastic zone are studied as a function of the stress ratio R, the thickness of the specimen and the level of ΔK. The experimental results are compared with those given by numerical and theoretical analyses based on the concepts of linear elastic fracture mechanics (LEFM).

Investigation on Stress and Strain Singularity in LEFM

2006 ◽  
Vol 306-308 ◽  
pp. 31-36
Author(s):  
Zheng Yang ◽  
Wanlin Guo ◽  
Quan Liang Liu
Keyword(s):  
High Stress ◽  
Crack Tip ◽  
Plane Stress State ◽  
Stress And Strain ◽  
Linear Elastic ◽  
Geometrical Nonlinear ◽  
Maximum Crack ◽  
Elastic Fracture ◽  
Plain Strain ◽  
Strain Singularity

Stress and strain singularity at crack-tip is the characteristic of Linear Elastic Fracture Mechanics (LEFM). However, the stress, strain and strain energy at crack-tip may be infinite promoting conflicts with linear elastic hypothesis. It is indicated that the geometrical nonlinear near the crack-tip should not be neglected for linear elastic materials. In fact, the crack-tip blunts under high stress and strain, and the singularity vanishes due to the deformation of crack surface when loading. The stress at crack-tip may still be very high even though the singularity vanishes. The low bound of maximum crack-tip stress is the modulus of elastic in plane stress state, while in plain strain state, it is greater than the modulus of elastic, and will increase with the Poisson’s ratio.

Fracture Mechanics Assessment of Hydrogen Storage Vessel

2021 ◽  
Author(s):  
Xiaoliang Jia ◽  
Zhiwei Chen ◽  
Fang Ji
Keyword(s):  
High Pressure ◽  
Fracture Mechanics ◽  
Hydrogen Storage ◽  
High Strength Steel ◽  
High Strength ◽  
Linear Elastic Fracture Mechanics ◽  
Storage Vessel ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Hydrogen Storage Vessel

Abstract High strength steel is usually used in fabrication of hydrogen storage vessel. The fracture toughness of high strength steel will be decreased and the crack sensitivity of the structures will be increased when high strength steels are applied in hydrogen environment with high pressure. Hence, the small cracks on the surface of pressure vessel may grow rapidly then lead to rupture. Therefore, this paper makes a series of research on how to evaluate the 4130X steel hydrogen storage vessel with fracture mechanics. This study is based on the assumption that there is a semi-elliptic crack on internal surface of hydrogen storage vessel. First of all, based on linear elastic fracture mechanics, the stress intensity factors and crack tolerance of 4130X steel hydrogen storage vessel have been calculated by means of finite element method based on interaction integral theory and polynomial-approximated approach from GB/T 34019 Ultra-high pressure vessels. Then, a comparative study has been made from the results of above methods to find out the difference between them. At last, the fatigue life of a 4130X steel hydrogen storage vessel has been predicted based on linear elastic fracture mechanics and Paris formula. The calculation methods and analysis conclusion can be used to direct the design and manufacture of hydrogen storage vessel.

Experimental Research on Seismic Behavior of RC Column with Different Concrete under Horizontal Low Cyclic Loading

2011 ◽  
Vol 374-377 ◽  
pp. 2041-2045
Author(s):  
Jing Wu ◽  
Fa Zhou Wang ◽  
Yue Li ◽  
Wen Yang ◽  
Shu Guang Hu
Keyword(s):  
Cyclic Loading ◽  
Seismic Behavior ◽  
Lightweight Concrete ◽  
Concrete Strength ◽  
High Strength ◽  
Frame Structure ◽  
Dead Weight ◽  
Elastic Plastic ◽  
Rc Column ◽  
Low Cyclic Loading

On the premise of maintaining certain vertical bearing capacity, the frame structure dissipates seismic energy by elastic-plastic deformation in elastic-plastic stage of earthquake action. Using lightweight concrete in structure not only can reduce the its dead weight, decrease the earthquake power; also meet the concrete strength, stiffness and elastic modulus requirements of important structure, so as to improve its energy dissipation capacity. This paper researched the effect of concrete materials, including or such as C60 high strength Lightweight concrete (HSLC), high strength concrete (HSC) and high strength Light weight aggregate concrete (HSLAC), on the seismic behavior of RC column under horizontal low cyclic loading, respectively and the match relationship between concrete and steel reinforcement cage was analyzed.

scholarly journals Experimental Study on the Caustics of Moving Cracks and Elliptical Curvature under Impact Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Haohao Luo ◽  
Renshu Yang ◽  
Yanbing Wang ◽  
Guoliang Yang ◽  
Chengxiao Li ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Impact Loading ◽  
Crack Tip ◽  
Test System ◽  
Moving Crack ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Crack Tip Stress

A dynamic caustics test system was used, and different moving cracks were analysed to study the interaction between the crack growth rate, stress intensity factor, and curvature of the elliptical end of a moving crack under impact loading. Based on the linear elastic fracture mechanics theory, linearly fitting of the crack tip stress intensity factor and the elliptical curvature were employed to obtain the specific functional expressions. ABAQUS software was used to numerically simulate the moving crack fracture process passing through different elliptical curvatures. The crack tip stress intensity factor was calculated by the stress extrapolation method. The stress intensity factor obtained from the numerical calculation and the caustics test was consistent. The test and numerical simulation results showed that the direction of moving cracks entering and passing through the elliptical defects shows a certain regularity. As the ellipse curvature increased, the moving crack stress intensity factor passing through the ellipse gradually decreased, and the moving crack also passed easily through oval defects.

Multiaxial Fatigue Life Prediction for Notched Components under Proportional and Non-Proportional Cyclic Loading

2012 ◽  
Vol 197 ◽  
pp. 585-589
Author(s):  
Hong Chen ◽  
De Guang Shang ◽  
Yu Jie Tian ◽  
Guang Wei Xu
Keyword(s):  
Fatigue Life ◽  
Cyclic Loading ◽  
Life Prediction ◽  
Elastic Solution ◽  
Fatigue Life Prediction ◽  
Elastic Plastic ◽  
Linear Elastic ◽  
Equivalent Parameter ◽  
Non Linear ◽  
Notched Components

Fatigue life estimation of notched components is mostly dependent on notch stress and strain calculation with non-linear finite element analysis (FEA). For multiaxial cyclic loading, the stress-strain analysis of notch root is rather complex and the non-linear FEA is also very time-consuming. In this paper, a new fatigue life prediction method for notched components under multiaxial loading is proposed. First, a linear elastic solution needs to be solved for notched components under multiaxial cyclic loading. Then, an elastic equivalent parameter is computed using the linear elastic solution. On the basis of the elastic equivalent parameter combined with the Neuber’s rule, an elastic-plastic equivalent parameter is obtained. Finally, the elastic-plastic equivalent parameter is used to estimate fatigue crack initiation life of notched components. The proposed method needs only elastically calculated notch strain history as the basic input and is convenient for engineering application. The method is verified with experimental data of SAE 1045 notched shaft specimens under proportional and non-proportional loading. The results showed that the method can provide good life estimates.

Crack-Induced Stress Concentration Is Suppressed in Nacreous Composites

2015 ◽  
Vol 813 ◽  
pp. 323-336
Author(s):  
Hai Min Yao
Keyword(s):  
Critical Size ◽  
Brittle Materials ◽  
High Strength ◽  
Crack Size ◽  
Linear Elastic ◽  
High Toughness ◽  
Induced Stress ◽  
Brick And Mortar ◽  
Elastic Fracture ◽  
Insight Into

Linear elastic fracture mechanics (LEFM) indicates that crack-like flaws tend to intensify stress in brittle materials with stress intensity proportional to the square root of the crack size. Under given loading, monolithic brittle materials can only endure cracks smaller than a critical size. In this paper, however, our exploration into the stress state of nacreous composites shows that the crack-induced stress intensification/concentration and its dependence on crack size can be suppressed in composites with ‘brick-and-mortar’ structure. This feature can be attributed to the unique ‘brick-and-mortar’ (B-and-M) structure and the complementary dissimilarity between ‘brick’ (e.g. minerals) and ‘mortar’ (e.g. proteins) phases in mechanical properties. Our findings provide a profound insight into the origin of high strength and high toughness in nacreous composites.

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