scholarly journals Characterization of Discontinuity and Mechanical Anisotropy of Shale Based on Continuum Damage Mechanics

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qinglin Shan ◽  
Peng Yan ◽  
Hengjie Luan ◽  
Yujing Jiang ◽  
Sunhao Zhang
Keyword(s):  
Mechanical Properties ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Element Model ◽  
Degradation Process ◽  
Fracture Network ◽  
Mechanical Anisotropy ◽  
Model Parameters ◽  
Continuum Damage ◽  
The Matrix

The effect of the bedding structure on the mechanical properties of layered shale was studied by means of experiment and numerical simulation. Based on continuum damage theory and discrete fracture network modeling method (D-DFN), a finite element model describing structural discontinuity and mechanical anisotropy of shale is established. In this model, the degradation process of stiffness and strength of shale after failure is described based on the stress-displacement relationship of elements. In order to distinguish the mechanical properties between the bedding and the matrix, a nonzero initial damage variable is set in bedding elements to show initial lower elastic modulus and strength of bedding elements compared with initially nondamaged matrix elements. The calibration of model parameters is discussed, and the simulation results are compared with the experimental results. The results show that the D-DFN method can effectively simulate the anisotropic characteristics of shale deformation and strength, which verifies the effectiveness of the method.

Modelling the asymmetric tension–compression properties of additively manufactured alloys using continuum damage mechanics

2021 ◽  
pp. 146442072110134
Author(s):  
A Nayebi ◽  
H Rokhgireh ◽  
M Araghi ◽  
M Mohammadi
Keyword(s):  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Element Model ◽  
Continuum Damage ◽  
Compression Tests ◽  
Compression Properties ◽  
Mechanics Model ◽  
Stress Components ◽  
Tension And Compression ◽  
Closure Effect

Additively manufactured parts often comprise internal porosities due to the manufacturing process, which needs to be considered in modelling their mechanical behaviour. It was experimentally shown that additively manufactured parts’ tensile and compressive mechanical properties are different for various metallic alloys. In this study, isotropic continuum damage mechanics is used to model additively manufactured alloys’ tension and compression behaviours. Compressive stress components can shrink discontinuities present in additively manufactured alloys. Therefore, the crack closure effect was employed to describe different behaviours during uniaxial tension and compression tests. A finite element model embedded in an ABAQUS’s UMAT format was developed to account for the isotropic continuum damage mechanics model. The numerical results of tension and compression tests were compared with experimental observations for additively manufactured maraging steel, AlSi10Mg and Ti-6Al-4V. Stress–strain curves in tension and compression of these alloys were obtained using the continuum damage mechanics model and compared well with the experimental results.

scholarly journals Failure Analysis of Composite Pinned Joints Based on Continuum Damage Mechanics

2018 ◽  
Vol 36 (5) ◽  
pp. 848-855
Author(s):  
Hongliang Tuo ◽  
Xiaoping Ma ◽  
Zhixian Lu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Element Model ◽  
Fracture Plane ◽  
Continuum Damage ◽  
Bearing Strength ◽  
Matrix Damage ◽  
Pinned Joints

The paper conducted bearing tests on composite pinned joints with four different stacking sequences. The bearing strength and bearing chord stiffness were obtained. The influence of stacking sequences on failure modes, bearing strength and bearing chord stiffness was discussed. Based on continuum damage mechanics, a three-dimensional finite element model of composite pinned joint under bearing load was built, where the maximum strain criterion was employed for initiation and bi-liner damage constitutive relation for revolution of fiber damage, while the physical-based Puck criterion was used for matrix damage initiation, and matrix damage revolution depended on the effective strain on the fracture plane. The failure mode, bearing strength and bearing chord stiffness of composite pinned joint were discussed with this model under which the non-linear shear behavior and in-situ strength effects were considered. Good agreements between test results and numerical simulations validates the accuracy and applicability of the finite element model.

scholarly journals On continuum damage mechanics

2019 ◽  
Vol 52 (3) ◽  
pp. 125-147
Author(s):  
Kari Juhani Santaoja
Keyword(s):  
Stress Tensor ◽  
Effective Stress ◽  
Elastic Strain ◽  
Damage Mechanics ◽  
Volume Fraction ◽  
Strain Tensor ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
The Matrix ◽  
Elastic Strain Tensor

A material containing spherical microvoids with a Hookean matrix response was shown to take the appearance usually applied in continuum damage mechanics. However, the commonly used variable damage D was replaced with the void volume fraction f , which has a clear physical meaning, and the elastic strain tensor \Bold {ε}^e with the damage-elastic strain tensor \Bold {ε}^{de}. The postulate of strain equivalence with the effective stress concept was reformulated and applied to a case where the response of the matrix obeys Hooke’s law. In contrast to many other studies, in the derived relation between the effective stress tensor \Bold {\Tilde{σ}} and the stress tensor \Bold {σ}, the tensor \Bold {\Tilde{σ}} is symmetric. A uniaxial bar model was introduce for clarifying the derived results. Other candidates for damage were demonstrated by studying the effect of carbide coarsening on creep rate.

Effects of different design parameters on the stone-impact resistance of automotive windshields

2005 ◽  
Vol 219 (9) ◽  
pp. 1059-1067 ◽  
Author(s):  
X Sun ◽  
M A Khaleel
Keyword(s):  
Damage Mechanics ◽  
Impact Resistance ◽  
Continuum Damage Mechanics ◽  
Element Model ◽  
Design Parameters ◽  
Continuum Damage ◽  
Mechanics Model ◽  
Linear Viscoelastic ◽  
Glass Surfaces ◽  
Vinyl Butyral

A constitutive model based on continuum damage mechanics is used to study the stone-impact resistance of automotive windshields. An axisymmetric finite element model is created to simulate the transient dynamic response and impact-induced damage tensors for laminated glass layers subject to stone-impact loading. The windshield glass consists of two glass outer layers laminated by a thin poly(vinyl butyral) (PVB) layer. The constitutive behaviour of the glass layers is simulated using the continuum damage mechanics model with linear damage evolution. The PVB layer is modelled with a linear viscoelastic solid. The model is used to predict and examine damage patterns on different glass surfaces for different windshield designs including variations in ply thickness and curvatures.

A Computer Simulation on Human Injury during the Aircrew/Seat Through-the-Canopy-Ejection

2011 ◽  
Vol 55-57 ◽  
pp. 179-182
Author(s):  
Zhi Qiang Li ◽  
Xiao Hu Yao ◽  
Long Mao Zhao
Keyword(s):  
Damage Mechanics ◽  
Human Head ◽  
Continuum Damage Mechanics ◽  
Material Model ◽  
Element Model ◽  
Continuum Damage ◽  
Viscoplastic Material ◽  
Simplified Finite Element Model ◽  
Design And Manufacture ◽  
Human Injury

For through-the-canopy-ejection-saving system with miniature detonation cord (MDC), screw/seat system has penetrated canopy to successfully escape after the strength of canopy weaken by MDC in the case of emergency. Injury of human head and spine is serious due to striking between aircrew/seat and canopy during the ejection. In the paper, considering MDC installed along all-around of canopy, the initial cut slot is used to model the damage of canopy impacted by detonation wave from MDC. Simplified finite element model of through-the-canopy-ejection-system has been established according to ergonomics. In FEM, canopy as PMMA employs elastic viscoplastic material model combined with continuum damage mechanics, crew is modeled as 50% deformable dummy. FEM is solved using nonlinear dynamics explicit code LS-DYNA3D. Head impact force and dynamic response index (DRI) of spine are obtained, and meet the requirement of nation army standard. Simulation results indicate that MDC installation way is avail to reduce physiology damage of airscrew. It also provides science foundation for safe design and manufacture of through-the-canopy-ejection-system.

Evolution of Damage in Near α IMI-834 Titanium Alloy Under Monotonic Loading Condition: A Continuum Damage Mechanics Approach

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Jalaj Kumar ◽  
S. Padma ◽  
B. Srivathsa ◽  
N. Vyaghreswara Rao ◽  
Vikas Kumar
Keyword(s):  
Titanium Alloy ◽  
Loading Condition ◽  
Damage Mechanics ◽  
Equivalent Stress ◽  
Damage Model ◽  
Continuum Damage Mechanics ◽  
Monotonic Loading ◽  
Model Parameters ◽  
Continuum Damage ◽  
Imi 834

In the present work, a continuum damage mechanics model, based on Lemaitre’s concept of equivalent stress hypothesis (1986, “Local Approach to Fracture,” Eng. Fract. Mech., 25, pp. 523–537), has been applied to study the evolution of damage under monotonic loading condition in a near α IMI-834 titanium alloy, used for aeroengine components in compressor module. The damage model parameters have been experimentally identified by in situ measurement of damage during monotonic deformation using alternating current potential drop technique. The damage model has been applied to predict damage evolution in an axisymmetrically notched specimen using finite element analysis. A reasonably good agreement has been observed between numerically simulated and experimentally measured damage behaviors. Damage micromechanisms operative in this alloy have also been identified which show multiple damage events.

A homogenisation-based continuum damage mechanics model for cyclic damage in 3D composites

2009 ◽  
Vol 113 (1144) ◽  
pp. 371-383 ◽  
Author(s):  
S. Ghosh ◽  
J. R. Jain
Keyword(s):  
Fourth Order ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Constitutive Law ◽  
Model Parameters ◽  
Zone Model ◽  
Continuum Damage ◽  
Proposed Model ◽  
Micromechanical Damage ◽  
Cyclic Damage

Abstract This paper develops a 3D homogenisation based continuum damage mechanics (HCDM) model for fibre-reinforced composites undergoing micromechanical damage under cyclic loading. Micromechanical damage in a representative volume element (RVE) of the material occurs by fibre-matrix interfacial debonding, which is incorporated in the model through a hysteretic bilinear cohesive zone model. The proposed model expresses a damage evolution surface in the strain space in the principal damage co-ordinate system or PDCS. PDCS enables the model to account for the effect of non-proportional load history. The material constitutive law involves a fourth order orthotropic tensor with stiffness characterised as a macroscopic internal variable. Cyclic damage parameters are introduced in the monotonic HCDM model to describe the material degradation due to fatigue. Three dimensional damage in composites is accounted for through functional forms of the fourth order damage tensor in terms of components of macroscopic strain and elastic stiffness tensor. The HCDM model parameters are calibrated from homogenisation of micromechanical solutions of the RVE for a few representative cyclic strain histories. The proposed model is validated by comparing results of the HCDM model with pure micromechanical analysis results followed by homogenisation. Finally, the potential of cyclic HCDM model as a design tool is demonstrated through macro-micro analysis of cyclic damage progression in composite structures.

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