scholarly journals Dynamic Fracture Analysis of Functional Gradient Material Coating Based on the Peridynamic Method

Coatings ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 62 ◽  
Author(s):  
Yu Zhang ◽  
Zhanqi Cheng ◽  
Hu Feng
Keyword(s):  
Elastic Modulus ◽  
Crack Propagation ◽  
Dynamic Fracture ◽  
Gradient Material ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Functional Gradient ◽  
Damage And Failure ◽  
Functional Gradient Material ◽  
Graded Material

Functional gradient materials (FGMs) have tremendous potential due to their characteristic advantage of asymptotic continuous variation of their properties. When an FGM is used as a coating material, damage and failure of the interface with the substrate component can be effectively inhibited. In order to study the dynamic crack propagation in FGM coatings, a new method, peridynamics (PD), was used in the present study to simulate dynamic fractures of FGM coatings bonded to a homogeneous substrate under dynamic loading. The bond-based PD theory was employed to study crack propagation and branching in the FGM coating. The influences of the coating gradient pattern, loading, and the geometry and size of the structure on crack curving and propagation under impact loading were investigated. The numerical results show that different forms of the elastic modulus of graded material, the geometry of the structure, and the loading conditions have considerate effects on crack propagation in FGM coatings, but a specific form of elastic modulus had a limited effect on the dynamic fracture of FGM coating.

scholarly journals Buckling of a composite bar made of a functional-gradient material with an inhomogeneous pre-stress field

2018 ◽  
Vol 226 ◽  
pp. 01014
Author(s):  
Vadim V. Eremeev ◽  
Denis V. Ivashchenko
Keyword(s):  
Stress Field ◽  
Circular Cylinder ◽  
Nonlinear Elasticity ◽  
Linear Instability ◽  
Initial Stresses ◽  
Gradient Material ◽  
Material Inhomogeneity ◽  
Functional Gradient ◽  
Functional Gradient Material ◽  
Graded Material

Within the 3D nonlinear elasticity we discuss the linear instability of a composite bar made of a functially graded material and having initial stresses. The bar consists of two layers which are inflated for a annular wedge of a circular cylinder. We present the linearized boundary0value problem and obtain its non-trivial solutions. The influence of the material inhomogeneity and the initial stresses are discussed.

scholarly journals STRESS CONCENTRATION IN A HOMOGENEOUS PLATE WITH A CIRCULAR HOLE REINFORCED BY AN INCLUSION FROM A FUNCTIONAL-GRADIENT MATERIAL

2021 ◽  
pp. 110-115
Author(s):  
Eteri Hart ◽  
Terokhin Bohdan
Keyword(s):  
Elastic Modulus ◽  
Stress Concentration ◽  
Circular Hole ◽  
Strain State ◽  
Isotropic Plate ◽  
Gradient Material ◽  
Homogeneous Material ◽  
Functional Gradient ◽  
Homogeneous Plate ◽  
Functional Gradient Material

Computer simulation of the stress-strain state of a thin rectangular homogeneous isotropic plate with a circular hole, reinforced by an annular inclusion made of a functional-gradient material (FGM) has been carried out. The influence of the geometric (width) and mechanical (elastic modulus) parameters of the inclusion is investigated when various laws of change in the elastic modulus of the FGM are set on the stress concentration around the hole. Recommendations for the use of inclusions are given. If there is a "hard" annular inclusion in a homogeneous plate with a hole, it is expedient to use an FGM with a nonlinear law of change in the modulus of elasticity in comparison with an inclusion made of a homogeneous material. Despite the fact that the inclusion leads to a slight increase in the stress concentration factor in comparison with a homogeneous material, it makes it possible to increase the rigidity of the system as a whole. The width of FGM inclusions affects the nature of the stress distribution: the wider the inclusion, the more smoothly the stress redistribution in the main matrix occurs.

scholarly journals Relationship Between Apparent (Total) Charpy Vee-Notch Toughness and the Corresponding Dynamic Crack-Propagation Resistance

1998 ◽  
Author(s):  
Brian N. Leis ◽  
Robert J. Eiber ◽  
L. Carlson ◽  
A. Gilroy-Scott
Keyword(s):  
Crack Propagation ◽  
Ductile Fracture ◽  
Dynamic Fracture ◽  
Empirical Models ◽  
Full Scale ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Propagation Resistance ◽  
Crack Propagation Resistance ◽  
Arrest Toughness

The consequences of a dynamic fracture in a gas-transmission pipeline require that pipelines be designed to avoid such incidents at a high level of certainty. For this reason, the related phenomonology has been studied since the early 1970s when the possibility of a dynamic ductile fracture was recognized. Full-scale experiments were done to characterize the fracture and gas dynamics associated with this process and empirical models were developed as a means to represent these experiments in a design or analysis setting. Such experiments focused on pure methane gas, and in the early days used steels with toughnesses less than 100 J, consistent with the steel making capabilities of the 1970s. Subsequently, interest shifted to larger diameter, higher pressure, higher BTU “rich” gases requiring higher toughness steels. The full-scale tests conducted to validate the arrest toughness levels determined that these empirical models were non-conservative. This paper presents a relationship between the dynamic crack propagation resistance and the apparent crack propagation resistance as measured by Charpy vee-notch (CVN) test specimens. This relationship is used in conjunction with the existing Battelle empirical criterion for dynamic-fracture arrest to determine the apparent toughness required to arrest a propagating ductile fracture in gas-transmission pipelines. The validity of this relationship is illustrated by successful predictions of arrest toughness in pipelines under a range of conditions including rich gases and high-toughness steels, including those showing a rising upper-shelf behavior.

Theoretical Research on the Dynamic Crack Propagation Velocity Based on Nonlocal Field Theories

2009 ◽  
Vol 417-418 ◽  
pp. 953-956
Author(s):  
Cai Ping Liu ◽  
Qing Quan Duan ◽  
Jian Ping Zuo
Keyword(s):  
Crack Propagation ◽  
Dynamic Fracture ◽  
Propagation Velocity ◽  
Characteristic Length ◽  
Theoretical Research ◽  
Field Theories ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Crack Propagation Velocity ◽  
Nonlocal Field

The purpose of this paper is to discuss the nonlocal effect on dynamic crack propagation velocity. Some experimental phenomena in dynamic fracture and simulative results using molecular & atom dynamics were analyzed and discussed in this paper. The authors found that there were still some disagreements on the dynamic crack propagation velocity. Based on these researches, we introduced nonlocal field theories into the estimation of dynamic crack propagation velocity. The dynamic crack propagation velocity is affected not only by the crack instability, but by characteristic length of material. A nonlocal characteristic length parameter M is defined through a double pile-up dislocation model. According to the Mott’s research method for crack velocity in dynamic fracture and the nonlocal field theories, an approximate theoretical dynamic propagation velocity is obtained. And we conclude that the velocity is related to the combined activity of the nonlocal characteristic length parameter M, the velocity of longitudinal wave, constant k, crack length and Poisson’s ratio.

Characteristics of dynamic crack propagation in a weak snowpack layer over its entire life cycle

2021 ◽  
Author(s):  
Bastian Bergfeld ◽  
Alec van Herwijnen ◽  
Gregoire Bobillier ◽  
Jürg Schweizer
Keyword(s):  
Life Cycle ◽  
Elastic Modulus ◽  
Crack Propagation ◽  
Effective Elastic Modulus ◽  
Crack Arrest ◽  
Image Correlation ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Displacement Fields ◽  
Weak Layer

<p>For a slab avalanche to release, a weak layer buried below a cohesive snow slab is required, and the system of weak layer and slab must support crack propagation over large distances. This process, called “dynamic crack propagation”, is highly relevant for avalanche release, and computational models are nowadays able to model crack propagation over increasingly larger scales. Field measurements on dynamic crack propagation are however very scarce, although these are required to validate models. We therefore performed a series of flat field PST experiments up to ten meters long over a period of 10 weeks. During this time, PST results evolved from crack arrest to full propagation and back to crack arrest – reflecting the life cycle of the weak layer. All PST experiments were analyzed using digital image correlation to derive high-resolution displacement fields to compute dynamic crack propagation metrics, including crack length and speed as well as touchdown distance, the distance from the crack tip to the trailing point where the slab comes into contact with the substratum. Comparing the displacement fields during sawing to a mechanical model, we estimated the effective elastic modulus of slab and weak layer as well as the specific fracture energy of the weak layer. Our results show how dynamic crack propagation characteristics change over the life cycle of a weak layer and how these measures relate to snowpack properties such as load and effective elastic modulus of the slab. We found that crack speed was highest for PSTs resulting in full propagation and that the touchdown length increased with increasing elastic modulus of the slab. Our dataset provides unique insight into the dynamics of crack propagation, and provides valuable data to validate models used to study sustained crack propagation.</p>

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