Ceramics Toughening Mechanism Study of Mixed-Mode I-III Cracks with a New Yield Criterion

2011 ◽  
Vol 27 (3) ◽  
pp. 409-414 ◽  
Author(s):  
Z.-J. Yang ◽  
Z.-Q. Wang ◽  
L.-Q Tang ◽  
X.-Y. Sun
Keyword(s):  
Phase Transformation ◽  
Steady State ◽  
Mixed Mode ◽  
Yield Criterion ◽  
Zirconia Ceramic ◽  
Mode I ◽  
Mode I Crack ◽  
Transformation Toughening ◽  
Phase Transformation Toughening ◽  
Growing Cracks

ABSTRACTConsidering the SD (strength differential) effect on compressive strength and tensile strength in zirconia ceramic material, a yield criterion with a special parameter is introduced. In addition, by analogy with associated flow rule, the constitutive model of phase transformation ceramic material has been established. Under generalized plane strain condition, the theoretical toughening expressions of mixed-mode I-III stationary cracks and steady-state growing cracks have been developed with the constitutive model. The crack toughening effect has been discussed in detail with the Poisson ratio, parameters k / α (the ratio of nominal yield strength and SD effect factor) and ω (the scale factor of mode I crack and mode III). The integral calculation shows that phase transformation toughening of stationary cracks is negative shielding effect and the toughening effect of the steady-state growing cracks change obviously with the increase of parameter k / α. Comparison between experimental data and theoretical data indicates that the yield criterion is in accord with the actual characteristics of the zirconia ceramic, when the expression of mixed-mode I-III crack is reduced to mode I crack. The results obtained in present paper can provide the useful theoretical reference for the research of phase transformation toughening in ceramic materials.

Toughening Analysis of Mixed Cracks in Transformation Toughened Ceramics on Influence of SD Effect

2010 ◽  
Vol 452-453 ◽  
pp. 145-148
Author(s):  
Zhen Qing Wang ◽  
Zeng Jie Yang ◽  
Li Qiang Tang
Keyword(s):  
Phase Transformation ◽  
Poisson Ratio ◽  
Yield Criterion ◽  
Parabolic Type ◽  
Zirconia Ceramic ◽  
Flow Rule ◽  
Mode I ◽  
Transformation Toughening ◽  
Ceramic Phase ◽  
Phase Transformation Toughening

Considering the SD effect, the parabolic-type yield criterion is obtained by using a new parameter. And by analogy with associated plastic flow rule, the ceramic phase transformation constitutive model is established. Under plane strain condition, the theoretical toughening expressions of mixed-mode I-II stationary cracks and steady-state growing cracks are developed by applying the weight function method. And the toughening effect is discussed under the influence of Poisson ratio, parameter and . The simulation results show that these phase transformation toughening effects are in good agreement with experimental results. And comparing with other yield criterions, it is more in line with actual characteristics of zirconia ceramic materials, when the expression of mixed I-II crack is reduced to mode I crack. And it also could provide theoretical support and reference for the further research of ceramic phase transformation toughening.

Trajectories of unstably growing cracks in mixed mode I?II loading of marble beams

1997 ◽  
Vol 30 (1) ◽  
pp. 19-33 ◽  
Author(s):  
G. S. Xeidakis ◽  
I. S. Samaras ◽  
D. A. Zacharopoulos ◽  
G. E. Papakaliatakis
Keyword(s):  
Mixed Mode ◽  
Mode I ◽  
Growing Cracks

The Dynamic Energy Release Rate for a Steadily Propagating Mode I Crack in an Infinite, Linearly Viscoelastic Body

1990 ◽  
Vol 57 (2) ◽  
pp. 343-353 ◽  
Author(s):  
J. R. Walton
Keyword(s):  
Steady State ◽  
Crack Propagation ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Viscoelastic Body ◽  
Mode I ◽  
Mode I Crack ◽  
Failure Zone ◽  
Special Cases

An analysis is presented for the dynamic, steady-state propagation of a semi-infinite, mode I crack in an infinite, linearly viscoelastic body. For mathematical convenience, the material is assumed to have a constant Poisson’s ratio, but the shear modulus is only assumed to be decreasing and convex. An expression for the Stress Intensity Factor (SIF) is derived for very general tractions on the crack faces and the Energy Release Rate (ERR) is constructed assuming that a fully developed Barenblatt type failure zone with nonsingular stresses exists at the crack tip and the loadings have a simple exponential form. For comparative purposes, expressions for the ERR are derived for the special cases of dynamic steady-state crack propagation in elastic material and quasi-static crack propagation in viscoelastic material, both with and without a failure zone. Sample calculations are included for power-law material and a standard linear solid in order to illustrate the combined influence of inertial effects, material viscoelasticity, and a failure zone upon the ERR.

Two Morphologies of Tetragonal Phase in the MgO-PSZ Ceramics

2013 ◽  
Vol 750-752 ◽  
pp. 497-500
Author(s):  
Yun Fei Wang ◽  
Yun Kai Li ◽  
Chun Sun
Keyword(s):  
Heat Treatment ◽  
Phase Transformation ◽  
Tetragonal Phase ◽  
Isothermal Holding ◽  
Transformation Toughening ◽  
Treatment Processes ◽  
Result Show ◽  
Phase Transformation Toughening ◽  
T Phase ◽  
The Relationship

The relationship between microstructures and sintering, heat treatment processes have been investigated in 8mol% MgO-0.5mol% Y2O3-PSZ ceramics. The result show that the T phase exhibits two different morphologies during sintering below 1800°C and isothermal holding or aging anew at 1500°C. Their shape, size, distribution and stability all have obvious difference, so they have different effects on the phase transformation toughening.

scholarly journals A theoretical and computational investigation of mixed mode creep crack growth along an interface

2021 ◽  
Author(s):  
Elsiddig Elmukashfi ◽  
Alan Cocks
Keyword(s):  
Steady State ◽  
Crack Growth ◽  
Mixed Mode ◽  
Damage Zone ◽  
Creep Crack Growth ◽  
Analytical Models ◽  
Mode I ◽  
Mode Mixity ◽  
Creep Crack ◽  
Coupling Parameters

Abstract In this paper, we propose a theoretical framework for studying mixed mode (I and II) creep crack growth under steady state creep conditions. In particular, we focus on the problem of creep crack growth along an interface, whose fracture properties are weaker than the bulk material, located either side of the interface. The theoretical framework of creep crack growth under mode I, previously proposed by the authors, is extended. The bulk behaviour is described by power-law creep, and damage zone models that account for mode mixity are proposed to model the fracture process ahead of a crack tip. The damage model is described by a traction-separation rate law that is defined in terms of an effective traction and separation which couple the different fracture modes. Different models are introduced, namely, a simple critical displacement model, empirical Kachanov type damage models and a micromechanical based model. Using the path independence of the C * -integral and dimensional analysis, analytical models are developed for mixed mode steady-state crack growth in a double cantilever beam specimen (DCB) subjected to combined bending moments and tangential forces. A computational framework is then implemented using the Finite Element method. The analytical models are calibrated against detailed Finite Element models and a scaling function (C k ) is determined in terms of a dimensionless quantity Φ 0 (which is the ratio of geometric and material length scales), mode mixity χ and the deformation and damage coupling parameters. We demonstrate that the form of the C k -function does not change with mode mixity; however, its value depends on the mode mixity, the deformation and damage coupling parameters and the detailed form of the damage zone. Finally, we demonstrate how parameters within the models can be obtained from creep deformation, creep rupture and crack growth experiments for mode I and II loading conditions.

Towards a Process for the Assessment of Mixed Mode I+II Fracture Toughness

2018 ◽  
Author(s):  
Afaf Bouydo ◽  
Valéry Lacroix ◽  
Rachid Chaouadi ◽  
Vratislav Mares
Keyword(s):  
Fracture Toughness ◽  
Mixed Mode ◽  
Ferritic Steel ◽  
Crack Opening ◽  
Pressure Vessels ◽  
Mode I ◽  
J Integral ◽  
Mode I Crack ◽  
Standard Mode ◽  
Material Fracture

In fracture mechanics, a flaw behavior in pressure vessels is assessed with respect to the material fracture toughness. Fracture toughness which most Fitness-for-Service (FFS) codes relies on, only considers mode-I crack opening. However, in presence of tilted flaws, like quasi-laminar hydrogen flakes, this mode-I toughness may be too severe, and a mixed mode I+II fracture toughness seems to be more appropriate. In order to address the assessment of the fracture toughness curve, mixed mode I+II tests were performed by the authors on ferritic steel samples by adjusting the standard mode I CT specimen geometry to a geometry subjected to mixed mode I+II. Then, XFEM simulations of the mixed mode tests were performed in order to calculate the J-integral along the crack front. Based on tests and calculations results, the paper explains how the authors work towards proposing a method to measure the material fracture toughness in case of flaws subjected to mixed mode (I+II) loading.

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