Description of Strengthening Mechanism in Layered Ceramic Composites

2015 ◽  
Vol 665 ◽  
pp. 93-96 ◽  
Author(s):  
Kateřina Štegnerová ◽  
Luboš Náhlík ◽  
Pavel Hutař
Keyword(s):  
Residual Stresses ◽  
Crack Propagation ◽  
Ceramic Composite ◽  
Strengthening Mechanism ◽  
Ceramic Composites ◽  
Zirconia Ceramic ◽  
Linear Elastic ◽  
Density Factor ◽  
Elastic Fracture ◽  
Layered Ceramic

The aim of this paper is to describe specific crack behaviour in the layered alumina-zirconia ceramic composite with strong interfaces and its strengthening mechanism. Different coefficients of thermal expansion of individual constituents of ceramic composite cause high residual stresses inside the layers during the sintering process. Compressive residual stresses can significantly influence the crack propagation through the laminate hereby improve the resistance of the material to the crack propagation. Estimation of crack behaviour in laminate was performed assuming the validity of linear elastic fracture mechanics using the criterion based on the strain energy density factor derived by Sih. This paper describes the strengthening mechanism in layered ceramic composites and prediction of their failure which contributes to better understanding of the fracture behaviour of the layered ceramic composites.

Influence of the Interface and Residual Stresses on the Apparent Fracture Toughness of Layered Ceramic Composites Based on Alumina-Zirconia

2014 ◽  
Vol 606 ◽  
pp. 209-212
Author(s):  
Luboš Náhlík ◽  
Bohuslav Máša ◽  
Pavel Hutař
Keyword(s):  
Residual Stresses ◽  
Crack Propagation ◽  
Ceramic Composites ◽  
Layered Composites ◽  
Material Interfaces ◽  
Linear Elastic ◽  
Apparent Fracture Toughness ◽  
Elastic Fracture ◽  
Layered Ceramic ◽  
Good Agreement

This paper deals with the fracture behaviour of layered ceramic composite with residual stresses. The main goal is to investigate the effect of residual stresses and material interfaces on crack propagation by more complex 3D finite element models. The crack behaviour was described by analytical procedures based on linear elastic fracture mechanics (LEFM) and generalized LEFM. The influence of laminate composition with residual stresses on critical values for crack propagation through the laminate interfaces was also determined. Good agreement has been found to exist between numerical results and experimental data. The results obtained can be used for a design of new layered composites with improved resistance against crack propagation.

Estimation of the Crack Behaviour in the Compressive Layer of the Alumina-Zirconia Ceramic Laminate

2014 ◽  
Vol 627 ◽  
pp. 41-44
Author(s):  
Luboš Náhlík ◽  
Bohuslav Máša ◽  
Pavel Hutař
Keyword(s):  
Crack Propagation ◽  
Direct Method ◽  
Zirconia Ceramic ◽  
Finite Element Models ◽  
Linear Elastic ◽  
Dimensional Finite Element ◽  
Density Factor ◽  
Elastic Fracture ◽  
Energy Density Factor ◽  
Good Agreement

This paper deals with a description of the crack behaviour in the layered alumina-zirconia ceramic laminate. The main aim is to investigate the crack behaviour in the compressive layer. The crack propagation was investigated on the basis of linear elastic fracture mechanics. Two dimensional finite element models were developed in order to obtain a stress distribution around the crack tip. The stress intensity factors were computed numerically employing the direct method. The change in the crack propagation direction was estimated using criterion based on the strain energy density factor. Sharp crack deflection in the compressive layer was predicted by mentioned approach. The determined crack behaviour is qualitatively in a good agreement with experimental observations.

Study of Influence of Residual Stresses on Crack Propagation in Particulate Ceramic Composites

2016 ◽  
Vol 258 ◽  
pp. 178-181 ◽  
Author(s):  
Zdeněk Majer ◽  
Luboš Náhlík ◽  
Kateřina Štegnerová ◽  
Pavel Hutař ◽  
Raúl Bermejo
Keyword(s):  
Residual Stresses ◽  
Crack Propagation ◽  
Element Model ◽  
Ceramic Composites ◽  
Particulate Composites ◽  
Micro Cracks ◽  
Dimensional Finite Element ◽  
Density Factor ◽  
Energy Density Factor

The aim of the present work is to analyze the influence of residual stresses in the particulate ceramic composite on the crack propagation. The crack propagation direction was estimated using Sih’s criterion based on the strain energy density factor. A two-dimensional finite element model was developed for determination of crack path. The residual stresses resulting from the mismatch of coefficients of thermal expansion during the fabrication process of the composite were implemented to the computational model. The effect of the particles shape on the crack propagation was investigated. Conclusions of this paper can contribute to a better understanding of the propagation of micro-cracks in particulate composites in the field of residual stresses.

Critical Value for Crack Propagation from Sharp V-Notch

2013 ◽  
Vol 592-593 ◽  
pp. 177-180
Author(s):  
Luboš Náhlík ◽  
Kateřina Štegnerová ◽  
Pavel Hutař ◽  
Zdeněk Majer
Keyword(s):  
Crack Propagation ◽  
Stress Singularity ◽  
Critical Value ◽  
Opening Angle ◽  
Singular Stress ◽  
Linear Elastic ◽  
Density Factor ◽  
Singularity Exponent ◽  
Elastic Fracture ◽  
Energy Density Factor

The contribution is focused on estimation of a critical value of generalized stress intensity factor for crack propagation from sharp V-notches. Stress distribution around the tip of the V-notch is described on the base of generalized linear elastic fracture mechanics, because V-notch is a singular stress concentrator with stress singularity exponent different from 0.5 (depending on V-notch opening angle). Then also stability criteria based on strain energy density factor and average critical stress are generalized for the stress singularity different from 0.5. Using FE analysis the critical stresses for crack initiation was estimated and compared with experimental data from the literature.

Residual Lifetime Determination of Low Temperature Co-Fired Ceramics

2016 ◽  
Vol 713 ◽  
pp. 266-269
Author(s):  
Zdeněk Majer ◽  
Kateřina Štegnerová ◽  
Pavel Hutař ◽  
Martin Pletz ◽  
Raul Bermejo ◽  
...  
Keyword(s):  
Low Temperature ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Particulate Composite ◽  
Ceramic Materials ◽  
Ceramic Composites ◽  
Residual Lifetime ◽  
Density Factor

The effect of subcritical crack growth is nowadays intensively studied mainly in relation to the strength of ceramic materials. The main aim of the contribution is to describe behavior of micro-crack propagating in the Low Temperature Co-fired Ceramics (LTCC) under subcritical crack growth (SCCG) conditions. The micro-crack behavior is significantly influenced by residual stresses developed in the LTCC due to different coefficients of thermal expansion of individual components. Two-dimensional numerical model was developed to simulate micro-crack propagation through the composite. The micro-crack propagation direction was determined using Sih’s criterion based on the strain energy density factor and the micro-crack path was obtained. The residual lifetime of the specific ceramic particulate composite (LTCC) was estimated on the basis of experimental data. The paper contributes to a better understanding of micro-crack propagation in particulate ceramic composites in the field of residual stresses.

Crack Behaviour in Laminar Ceramics with Strong Interfaces

2009 ◽  
Vol 417-418 ◽  
pp. 301-304 ◽  
Author(s):  
Luboš Náhlík ◽  
Lucie Šestáková ◽  
Pavel Hutař
Keyword(s):  
Crack Propagation ◽  
Propagation Direction ◽  
External Loading ◽  
Small Scale ◽  
Material Interface ◽  
Linear Elastic ◽  
Crack Propagation Direction ◽  
Density Factor ◽  
Scale Yielding ◽  
Elastic Fracture

The paper deals with crack propagation in ceramic laminates. Assumptions of linear elastic fracture mechanics and small scale yielding are considered. Crack behaviour in a ceramic laminate body under external loading is investigated. Strong residual stresses due to different coefficients of thermal expansion of individual material layers are taken into account in finite element calculations. The change of crack propagation direction at the material interface is estimated on the base of the strain energy density factor and maximum tangential stress criteria. The influence of thickness of laminate layers on crack propagation direction is estimated. The stepwise crack propagation through the Al2O3-ZrO2 ceramic laminate is numerically estimated. It can be concluded that good agreement between the estimated crack path and experimental data was found.

THE EFFECT OF RESIDUAL STRESSES IN FILLET WELDS ON THE FATIGUE BEHAVIOR: A LEFM APPROACH

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Wim Nagy ◽  
Hans De Backer ◽  
Philippe Van Bogaert
Keyword(s):  
Residual Stresses ◽  
Crack Propagation ◽  
Fatigue Behavior ◽  
Growth Direction ◽  
Steel Bridge ◽  
Civil Structures ◽  
Linear Elastic ◽  
Real Behavior ◽  
Crack Growth Direction ◽  
Elastic Fracture

Residual stresses are present in many civil structures due to manufacturing actions causing plastic deformations. Nevertheless, these stresses are not often taken into account when considering the design of these structures, especially when assessing fatigue problems. This remains true for orthotropic steel bridge decks. Due to their many complex welding details, these decks are sensitive to fatigue. To increase the understanding of the fatigue behavior of welded details, an improved analyzing tool using linear elastic fracture mechanics is proposed in this paper. Apart from the fatigue life of the weld detail, the crack propagation and crack growth direction are also evaluated with an XFEM model. Application of this method to the case of the orthotropic steel Temse Bridge in Belgium results in crack propagation very similar to reality. It also demonstrates that the fatigue calculations need to include residual stresses to comply with the real behavior of crack propagation.

3D Model of Crack Propagation in Particulate Ceramic Composite Containing Residual Stresses

2017 ◽  
Vol 754 ◽  
pp. 103-106
Author(s):  
Kateřina Štegnerová ◽  
Zdeněk Majer ◽  
Pavel Hutař ◽  
Luboš Náhlík
Keyword(s):  
Residual Stresses ◽  
Crack Propagation ◽  
Ceramic Composite ◽  
Volume Fraction ◽  
Numerical Models ◽  
Ceramic Composites ◽  
Fe Method ◽  
Critical Crack ◽  
Alumina Particles

A crack propagation and fracture behaviour of particulate ceramic composite were investigated. Influence of 3D shape of particles on the crack propagation was studied together with influence of the presence of residual stresses, which are developed inside the composite during manufacturing process. Finite element (FE) method was used for numerical simulation of propagating crack in the composite. Basic numerical models of low-temperature co-fired ceramics (LTCC) with alumina particles homogenously dispersed in the glass matrix were developed. Volume fraction of alumina phase was 20vol.%, which is typical amount for LTCC. The results show that existence of residual stresses retards the crack propagating under conditions of sub-critical crack growth (SCG). Presented results contribute to a better understanding of the role of residual stresses in particulate ceramic composites.

Application of Multi-Parameter Fracture Mechanics to Study of Crack Propagation Angle in Selected Mixed-Mode Geometry

2013 ◽  
Vol 592-593 ◽  
pp. 209-212 ◽  
Author(s):  
Lucie Šestáková Malíková ◽  
Václav Veselý
Keyword(s):  
Fracture Mechanics ◽  
Crack Propagation ◽  
Mixed Mode ◽  
Initial Crack ◽  
Propagation Angle ◽  
Linear Elastic ◽  
Higher Order Terms ◽  
Elastic Fracture ◽  
Cracked Specimens ◽  
Crack Propagation Angle

The multi-parameter fracture mechanics becomes more and more significant, because it is shown that it can help to describe fracture processes occurring in cracked specimens more precisely than conventional linear elastic fracture mechanics. In this paper, the concept based on the Williams expansion derived for approximation of stress/displacement crack-tip fields is presented and applied on a mixed-mode configuration. Two fracture criteria for estimation of the initial crack propagation angle are introduced. A parametric study is performed in order to investigate the dependence of the crack propagation angle on the stress intensity factors ratio. Influence and importance of taking into account the so-called higher-order terms of the Williams expansion are discussed and some recommendations are stated.

Estimation of the Crack Propagation Direction of a Crack Touching the Interface between Two Elastic Materials

2007 ◽  
Vol 567-568 ◽  
pp. 225-228 ◽  
Author(s):  
Luboš Náhlík ◽  
Lucie Šestáková ◽  
Pavel Hutař
Keyword(s):  
Crack Propagation ◽  
Protective Coatings ◽  
The Body ◽  
Elastic Behavior ◽  
Layered Composites ◽  
The Finite Element Method ◽  
Elastic Materials ◽  
Linear Elastic ◽  
Composites Materials ◽  
Elastic Fracture

The objective of the paper is to investigate the direction of a further crack propagation from the interface between two elastic materials. The angle of crack propagation changes when the crack passes the interface. The suggested procedure makes it possible to estimate an angle of propagation under which the crack will propagate into the second material. The assumptions of linear elastic fracture mechanics and elastic behavior of the body with interfaces are considered. The finite element method was used for numerical calculations. The results obtained might contribute to a better understanding of the failure of materials with interfaces (e.g. layered composites, materials with protective coatings) and to a more reliable estimation of the service life of such structures.

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