Mean Strain Effect on Crack Initiation Lives for Notched Specimens Under Biaxial Nonproportional Loading Paths

1997 ◽  
Vol 119 (1) ◽  
pp. 104-112 ◽  
Author(s):  
Ming-Chuen Yip ◽  
Yi-Ming Jen
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Initiation ◽  
Strain Effect ◽  
Nonproportional Loading ◽  
Notched Specimens ◽  
Loading Paths ◽  
The Mean ◽  
Mean Strain ◽  
Element Method

This paper discusses the mean strain effect on the crack initiation lives for notched specimens under biaxial nonproportional loading paths. Elastic-plastic finite element method was used to evaluate the local stresses and strains. Several prediction models related to the mean stress/strain effect were employed to correlate the experimental results with reference fatigue data for smooth specimens. It is found that Fatemi-Socie model gives good prediction for the present research with the assistance of finite element method. The stress behavior in this deflection-controlled tests is discussed in this study, and the failure surfaces are also examined after tests.

Numerical Simulation of Deflection Fracturing with Finite Element Method Considering Crack Initiation Angle

2013 ◽  
Vol 712-715 ◽  
pp. 1027-1031
Author(s):  
Zhen Yu Liu ◽  
Ping Ping Zhang ◽  
Hu Zhen Wang ◽  
Xiang Rong Zhu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Initiation ◽  
Working Condition ◽  
Oil Production ◽  
Oil Well ◽  
Two Phase ◽  
Crack Initiation Angle ◽  
Object Of Study ◽  
Element Method

Aimed at deflection fracturing by oriented perforation, a two-dimensional, non-steady and two-phase Finite Element Method (FEM) is established. Taking a battery of wells in the inverted nine-spot rhombus pattern as object of study, it is reported that law of different crack initiation angle (CIA) affecting deflection fracturing. In the respect of daily oil production and cumulative oil production, the dual fracture with different CIA is more than straight fracture. So it is feasible to use deflection fracturing of oriented perforation to increase the production of the special low permeability oilfield. In contrast to dual fractures with different fracturing initiation angles, we can see that the wider CIA, the higher cumulative oil production. So we can draw such a conclusion that when deflection fracturing is implemented, angle should be increased if the working condition is permitted so as to increase the production of oil well.

Finite Element Method for Stochastic Beams Based on Variational Principles

1997 ◽  
Vol 64 (3) ◽  
pp. 664-669 ◽  
Author(s):  
Y.-J. Ren ◽  
I. Elishakoff ◽  
M. Shinozuka
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Covariance Function ◽  
Variational Principles ◽  
Joint Probability ◽  
Accurate Solution ◽  
Joint Probability Distribution ◽  
Covariance Functions ◽  
The Mean ◽  
Element Method

This paper proposes a new version (fundamentally different from the existing ones) of finite element method for the mean and covariance functions of the displacement for bending beams with spatially random stiffness. Apart from the conventional finite element method for stochastic problems, which utilizes either perturbation or series expansion technique or the Monte Carlo simulation, the present method is based on the newly established variational principles. The finite element scheme is formulated directly with respect to the mean function and covariance function, rather than perturbed components of the displacement. It takes into account an information on joint probability distribution function of the random stiffness to obtain the covariance function of the displacement. Therefore, the accurate solution can be obtained even if the coefficient of variation of the random stiffness is large, in contrast to conventional technique. Several examples are given to illustrate the advantage of the proposed method, compared with the conventional ones.

scholarly journals An XFEM-Based Analysis of Concrete Face Cracking in Rockfill Dams

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Binpeng Zhou ◽  
Junrui Chai ◽  
Jing Wang ◽  
Heng Zhou ◽  
Lifeng Wen
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Model ◽  
Crack Initiation ◽  
Rockfill Dam ◽  
Initiation And Propagation ◽  
The Face ◽  
Stress And Deformation ◽  
Concrete Face ◽  
Element Method

The concrete face of a rockfill dam is a long and thin slab structure, which is highly susceptible to fracture when subjected to the settlement of the dam. The study of the generation and propagation of cracks in the concrete face of rockfill dams is of great significance to dam construction and face crack prevention. In this study, the initiation and propagation of cracks in the concrete face of a rockfill dam are investigated using an extended finite element method (XFEM) and ABAQUS software for the Gongboxia concrete-face rockfill dam. A numerical model for this dam is established using a finite element method, and the face stress and deformation distributions are obtained. Based on the results, a numerical model is built to find the location where cracks are initiated in the face. The displacement of the entire model is treated as the equivalent displacement for the numerical model. XFEM is utilized throughout the modeling process to obtain the stress concentration, crack initiation, and crack propagation in the concrete face, and an analysis of crack initiation and propagation is conducted. Finally, the effects of the thickness of concrete covers and reinforcement layers on the stress intensity of crack tips are also discussed using the established numerical model, and techniques for controlling the fracturing of the concrete face have been proposed in this paper.

Resonance Reliability Assessment of Turbine Blade with Parametric Uncertainty

2007 ◽  
Vol 353-358 ◽  
pp. 2636-2639 ◽  
Author(s):  
Yong Qing Ge ◽  
Li Qiang An ◽  
Zhang Qi Wang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Turbine Blade ◽  
Parametric Uncertainty ◽  
Stochastic Finite Element Method ◽  
Stochastic Finite Element ◽  
Probabilistic Characteristic ◽  
The Mean ◽  
Mean Variance ◽  
Element Method

Stochastic finite element method and reliability technique are used to determine the safety degree of the turbine blade with parametric uncertainty. The material, geometric parameters and rotating speed of blade exhibit notable random fluctuations, so the conventional deterministic analysis of blade can’t provide complete information. The stochastic analysis can tackle the uncertainties in structural parameters and obtain the probabilistic characteristic of the vibration characteristic. In this paper, the study focuses on the reliability assessment of the blade with uncertainty parameters based on the stochastic finite element method (SFEM) and the mean-variance method. The perturbation stochastic finite element method (PSFEM) is used to calculate probabilistic characteristic of the natural vibration of the turbine blade. Based on the stochastic finite element method, the mean-variance method is used to calculate the resonance reliability of the blade. The example shows that the present method is valid.

scholarly journals Investigation of the Effect of Inhomogeneous Material on the Fracture Mechanisms of Bamboo by Finite Element Method

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5039
Author(s):  
Raviduth Ramful ◽  
Atsushi Sakuma
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Initiation ◽  
Transverse Isotropy ◽  
Axial Direction ◽  
Fracture Mechanisms ◽  
Homogeneous Material ◽  
Shear Modes ◽  
Element Erosion ◽  
Element Method

Bamboo is a remarkably strong and sustainable material available for construction. It exhibits optimized mechanical characteristics based on a hollow-inhomogeneous structure which also affects its fracture behavior. In this study, the aim is to investigate the effect of material composition and geometrical attributes on the fracture mechanisms of bamboo in various modes of loading by the finite element method. In the first part of the investigation, the optimized transverse isotropy of bamboo to resist transverse deformation was numerically determined to represent its noticeable orthotropic characteristics which prevail in the axial direction. In the second part of this study, a numerical investigation of fracture mechanisms in four fundamental modes of loading, namely bending, compression, torsion, and shear, were conducted by considering the failure criterion of maximum principal strain. A crack initiation stage was simulated and compared by implementing an element erosion technique. Results showed that the characteristics of bamboo’s crack initiation differed greatly from solid geometry and homogeneous material-type models. Splitting patterns, which were discerned in bending and shear modes, differed in terms of location and occurred in the outside-center position and inside-lowermost position of the culm, respectively. The results of this study can be useful in order to achieve optimized strength in bamboo-inspired bionic designs.

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