Mode I Stress Intensity Factor for a Cracked Plate with an Integrated Piezoelectric Actuator

2015 ◽  
Vol 1115 ◽  
pp. 517-522 ◽  
Author(s):  
Ahmed Abuzaid ◽  
Meftah Hrairi ◽  
Mohd Sultan Dawood
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Piezoelectric Actuator ◽  
Crack Tip ◽  
Critical Stress Intensity Factor ◽  
Mode I ◽  
Singular Stress ◽  
Cracked Plate

The fracture performance of cracked structures is dominated by singular stress in the crack tip vicinity. In fracture mechanics most interest is focused on stress intensity factors, which describe the singular stress field ahead of a crack tip and govern fracture of structures when a critical stress intensity factor is reached. In the present work linear fracture mechanics is applied in order to obtain the fracture toughness parameters of a cracked plate integrated with piezoelectric actuator under mode I loading. Analytical model was derived to represent the relation between piezoelectric parameters and stress intensity factor and energy release rate. The results indicate that the stress intensity factor decreases linearly with the application of the different piezoelectric actuator voltages.

scholarly journals Applicability of Continuum Fracture Mechanics in Atomistic Systems

2011 ◽  
Author(s):  
Shao-Huan Cheng ◽  
C. T. Sun
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Stress Singularity ◽  
Critical Stress Intensity Factor ◽  
Singular Stress ◽  
Virial Stress ◽  
Atomistic Systems ◽  
Definition Of

Stress intensity factor is one of the most significant fracture parameters in linear elastic fracture mechanics (LEFM). Due to its simplicity, many researchers directly employed this concept to explain their results from molecular simulation. However, stress intensity factor defines the amplitude of the singular stress, which is the product of continuum elasticity. Under atomistic systems without the stress singularity, the concept of stress intensity factor must be examined. In addition, the difficulty of studying the stress intensity factor in atomistic systems may be traced back to the ambiguous definition of the local atomistic stress. In this study, the definition of the local virial stress is adopted. Subsequently, through the consideration of K-dominance, the approximated stress intensity factor based on the atomistic stress can be projected within a reasonable region. Moreover, the influence of cutting interatomic bonds to create traction free crack surfaces and the critical stress intensity factor is also discussed.

Direct Measurements of Fracture Toughness and Crack Growth in Polysilicon MEMS

2004 ◽  
Vol 854 ◽  
Author(s):  
I. Chasiotis ◽  
S.W. Cho ◽  
K. Jonnalagadda
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Critical Stress ◽  
Polycrystalline Silicon ◽  
Crack Tip ◽  
Critical Stress Intensity Factor ◽  
Mode I ◽  
Direct Measurements

ABSTRACTDirect measurements of Mode-I critical stress intensity factor and crack tip displacements were conducted in the vicinity of atomically sharp edge cracks in polycrystalline silicon MEMS using our in situ Atomic Force Microscopy (AFM)/Digital Image Correlation (DIC) method. The average Mode-I critical stress intensity factor for various fabrication runs was 1.00 ± 0.1 MPa√m. The experimental crack tip displacement fields were in very good agreement with linear elastic fracture mechanics solutions. By means of an AFM, direct experimental evidence of incremental crack growth in polycrystalline silicon was obtained for the first time via spatially resolved crack growth measurements. The incremental crack growth in brittle polysilicon is attributed to its locally anisotropic polycrystalline structure which also results in different local and macroscopic (apparent) stress intensity factors.

Modeling approach to evaluating reduction in stress intensity factor in center-cracked plate with piezoelectric actuator patches

2016 ◽  
Vol 28 (10) ◽  
pp. 1334-1345 ◽  
Author(s):  
Ahmed Abuzaid ◽  
Meftah Hrairi ◽  
MSI Shaik Dawood
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Piezoelectric Actuator ◽  
Piezoelectric Actuators ◽  
Mode I ◽  
Damage Propagation ◽  
Piezoelectric Patch ◽  
Cracked Structure

Active repairs using piezoelectric actuators can play a significant role in reducing the crack damage propagation in thin plate structures. Mode-I crack opening displacement is the most predominant one in tension, and it is responsible for the failure which in turn affects the load carrying capability of the cracked structure. In addition, there are limited studies that investigated the effect of the piezoelectric actuator over mode-I active repair. In this study, the mode-I stress intensity factor for a plate with a center crack, and a bonded piezoelectric actuator was modeled using the linear elastic fracture mechanics. For this, an analytical closed-form solution is developed using the virtual crack closure technique taking into account mode-I as the only effective mode, coupling effects of the piezoelectric patch, and the singular stress at the crack tip. In addition, the total stress intensity factor was obtained by the superposition of the stress intensity factor obtained from the stresses produced by the piezoelectric actuators on the crack surfaces as the only external loads on the cracked plate and the stress intensity factor due to the far-field tension load. The proposed analytical model for mode-I stress intensity factor was verified by a finite element–based approach using ANSYS finite element software. The results demonstrated a good agreement between the analytical and finite element models with a relative error of less than 4% in all the cases studied. The results illustrated that the piezoelectric patch is efficient in reducing stress intensity factor when an extension mode of the actuator is applied. However, applying a contraction mode of the piezoelectric actuators produced negative strain which increased the stress intensity factor and thus the severity of the cracked structure and could lead to damage propagation.

Mode I critical stress intensity factor of wood and medium-density fiberboard measured by compact tension test

Holzforschung ◽  
2011 ◽  
Vol 65 (5) ◽  
Author(s):  
Hiroshi Yoshihara ◽  
Ami Usuki
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Critical Stress ◽  
Medium Density Fiberboard ◽  
Compact Tension ◽  
Critical Stress Intensity Factor ◽  
Mode I ◽  
Medium Density ◽  
Single Edge

Abstract The critical stress intensity factor of mode I (K Ic) obtained by compact tension (CT) tests of wood and medium-density fiberboard (MDF) was experimentally and numerically analyzed. A double cantilever beam (DCB) test was also conducted and the results were compared with those of the CT tests. Similar to the results of single-edge-notched bending (SENB) and single-edge-notched tension (SENT) tests previously conducted, the value of K Ic was obtained properly from the CT test when an additional crack length was taken into account.

Fracture Mechanics Fatigue Evaluation of a Flowline Clamp Connector Using Finite Element Modeling of a Crack

2019 ◽  
Author(s):  
Curtis Sifford ◽  
Ali Shirani
Keyword(s):  
Finite Element Analysis ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Crack Tip ◽  
Element Analysis

Abstract This paper presents the application of the rules from ASME Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code for a fracture mechanics evaluation to determine the damage tolerance and fatigue life of a flowline clamp connector. The guidelines from API 579-1 / ASME FFS-1 Fitness-For-Service for the stress analysis of a crack-like flaw have been considered for this assessment. The crack tip is modeled using a refined mesh around the crack tip that is referred to as a focused mesh approach in API 579-1 / ASME FFS-1. The driving force method is used as an alternative to the failure assessment diagram method to account for the influence of crack tip plasticity. The J integral is determined using elastic-plastic finite element analysis and converted to an equivalent stress intensity factor to be compared to the fracture toughness of the material. The fatigue life is calculated using the Paris Law equation and the stress intensity factor calculated from the finite element analysis. The allowable number of design cycles is determined using the safety factors required from Division 3 of the ASME Pressure Vessel Code.

Fracture Mechanics Fatigue Evaluation of a Flowline Clamp Connector Using Finite Element Modeling of a Crack

2018 ◽  
Author(s):  
Curtis Sifford ◽  
Ali Shirani
Keyword(s):  
Finite Element Analysis ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Crack Tip ◽  
Element Analysis

This paper presents the application of the rules from ASME Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code for a fracture mechanics evaluation to determine the damage tolerance and fatigue life of a flowline clamp connector. The guidelines from API 579-1 / ASME FFS-1 Fitness-For-Service for the stress analysis of a crack-like flaw have been considered for this assessment. The crack tip is modeled using a refined mesh around the crack tip that is referred to as a focused mesh approach in API 579-1 / ASME FFS-1. The driving force method is used as an alternative to the failure assessment diagram method to account for the influence of crack tip plasticity. The J integral is determined using elastic-plastic finite element analysis and converted to an equivalent stress intensity factor to be compared to the fracture toughness of the material. The fatigue life is calculated using the Paris Law equation and the stress intensity factor calculated from the finite element analysis. The allowable number of design cycles is determined using the safety factors required from Division 3 of the ASME Pressure Vessel Code.

Evolution of Tenacity in Mixed Mode Fracture – Volumetric Approach

2020 ◽  
Vol 22 (4) ◽  
pp. 931-938
Author(s):  
O. Zebri ◽  
H. El Minor ◽  
A. Bendarma
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Mixed Mode ◽  
Local Stress ◽  
Critical Stress Intensity Factor ◽  
Mixed Mode Fracture ◽  
Intensity Factors ◽  
Singular Stress

AbstractIn fracture mechanics most interest is focused on stress intensity factors, which describe the singular stress field ahead of a crack tip and govern fracture of a specimen when a critical stress intensity factor is reached. In this paper, stress intensity factors which represents fracture toughness of material, caused by a notch in a volumetric approach has been examined, taking into account the specific conditions of loading by examining various U-notched circular ring specimens, with various geometries and boundary conditions, under a mixed mode I+II. The bend specimens are computed by finite element method (FEM) and the local stress distribution was calculated by the Abaqus/CAE. The results are assessed to determine the evolution of the stress intensity factor of different notches and loading distances from the root of notch. This study shows that the tenacity is not intrinsic to the material for all different geometries notches.

Effect of Grain Size on the Fracture Toughness of Bimodal Nanocrystalline Materials

2014 ◽  
Vol 936 ◽  
pp. 400-408 ◽  
Author(s):  
Ying Guang Liu ◽  
Xiao Dong Mi ◽  
Song Feng Tian
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Grain Size ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Cohesive Zone ◽  
Critical Stress ◽  
Crack Tip ◽  
Critical Stress Intensity Factor ◽  
Coarse Grain

To research the effect of grain size on the fracture toughness of bimodal nanocrystalline (BNC) materials which are composed of nanocrystalline (NC) matrix and coarse grains, we have developed a theoretical model to study the critical stress intensity factor (which characterizes toughness) of BNC materials by considering a typical case where crack lies at the interface of two neighboring NC grains and the crack tip intersect at the grain boundary of the coarse grain, the cohesive zone size is assumed to be equal to the grain sizedof the NC matrix. Blunting and propagating processes of the crack is controlled by a combined effect of dislocation and cohesive zone. Edge dislocations emit from the cohesive crack tip and make a shielding effect on the crack. It was found that the critical stress intensity factor increases with the increasing of grain sizedof the NC matrix as well as the coarse grain sizeD. Moreover, the fracture toughness is relatively more sensitive to the coarse grain size rather than that of NC matrix.

Fracture Toughness and Subcritical Crack Growth in Polycrystalline Silicon

2005 ◽  
Vol 73 (5) ◽  
pp. 714-722 ◽  
Author(s):  
I. Chasiotis ◽  
S. W. Cho ◽  
K. Jonnalagadda
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Crack Growth ◽  
Critical Stress ◽  
Polycrystalline Silicon ◽  
Subcritical Crack Growth ◽  
Crack Tip ◽  
Critical Stress Intensity Factor ◽  
Mode I ◽  
Intensity Factors

The fracture behavior of polycrystalline silicon in the presence of atomically sharp cracks is important in the determination of the mechanical reliability of microelectromechanical system (MEMS) components. The mode-I critical stress intensity factor and crack tip displacements in the vicinity of atomically sharp edge cracks in polycrystalline silicon MEMS scale specimens were measured via an in situ atomic force microscopy/digital image correlation method. The effective (macroscopic) mode-I critical stress intensity factor for specimens from different fabrication runs was 1.00±0.1MPa√m, where 0.1MPa√m is the standard deviation that was attributed to local cleavage anisotropy and grain boundary effects. The experimental near crack tip displacements were in good agreement with the linearly elastic fracture mechanics solution, which supports K dominance in polysilicon at the scale of a few microns. The mechanical characterization method implemented in this work allowed for direct experimental evidence of incremental (subcritical) crack growth in polycrystalline silicon that occurred with crack increments of 1-2μm. The variation in experimental effective critical stress intensity factors and the incremental crack growth in brittle polysilicon were attributed to local cleavage anisotropy in individual silicon grains where the crack tip resided and whose fracture characteristics controlled the overall fracture process resulting in different local and macroscopic stress intensity factors.

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