Fracture behaviour of engineering stone material

Purpose Engineered stone is a material which can be described as an artificial stone. The exemplary application area is sink production. There are very few research projects about this type of material. In fact, most of them are research conducted by the manufacturing company, which are limited to the basic properties of the material. However, knowledge about fracture mechanic of this material may be crucial in terms of usage. The paper aims to discuss this issue. Design/methodology/approach Analysis of the inside structure was made using an optical microscope as well as SEM. In the paper, methods which can be used to obtain data about fracture behaviour of material are presented. Using eXtended Finite Element Method and experimental data from three-point bending of notched specimens stress intensity factors (SIFs) for I and II load modes were obtained. Finally, a comparison between the fracture initiation angle in the function of the ration of SIFs for I/II load modes and maximum tangential stress hypothesis prediction was presented. Findings Analysis of the inside structure proves that this type of material has an uneven distribution of particle size. This can follow to void and micronotches formation and, later, to the failure of the material. A method of obtaining stress intensity factors for the discussed type of material and specimens can be successfully applied to other similar material, as proposed in this work. Standard crack angle propagation criteria are not sufficient for this type of material. Originality/value There are very few research papers about this type of material. The subject of fracture mechanic is not properly discovered, despite the fact that IT is important in terms of the application area of these materials.

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Effect fracture resistance on retardation of crack growth

International Journal of Structural Integrity ◽

10.1108/ijsi-10-2014-0053 ◽

2015 ◽

Vol 6 (4) ◽

pp. 510-521

Author(s):

Jirí Behal ◽

Petr Homola ◽

Roman Ružek

Keyword(s):

Fatigue Crack ◽

Stress Intensity ◽

Fatigue Crack Growth ◽

Crack Propagation ◽

Aluminium Alloy ◽

Crack Growth ◽

Stress Intensity Factors ◽

High Stress ◽

Intensity Factors ◽

Content Type

Purpose – The prediction of fatigue crack growth behaviour is an important part of damage tolerance analyses. Recently, the author’s work has focused on evaluating the FASTRAN retardation model. This model is implemented in the AFGROW code, which allows different retardation models to be compared. The primary advantage of the model is that all input parameters, including those for an initial plane-strain state and its transition to a plane-stress-state, are objectively measured using standard middle-crack-tension M(T) specimens. The purpose of this paper is to evaluate the ability of the FASTRAN model to predict correct retardation effects due to high loading peaks that occur during variable amplitude loading in sequences representative of an aircraft service. Design/methodology/approach – This paper addresses pre-setting of the fracture toughness K R (based on J-integral J Q according to ASTM1820) in the FASTRAN retardation model. A set of experiments were performed using specimens made from a 7475-T7351 aluminium alloy plate. Loading sequences with peaks ordered in ascending-descending blocks were used. The effect of truncating and clipping selected load levels on crack propagation behaviour was evaluated using both experimental data and numerical analyses. The findings were supported by the results of a fractographic analysis. Findings – Fatigue crack propagation data defined using M(T) specimens made from Al 7475-T7351 alloy indicate the difficulty of evaluating the following two events simultaneously: fatigue crack increments after application of loads with maximum amplitudes that exceeded J Q and subcritical crack increments caused by loads at high stress intensity factors. An effect of overloading peaks with a maximum that exceeds J Q should be assessed using a special analysis beyond the scope of the FASTRAN retardation model. Originality/value – Measurements of fatigue crack growth on specimens made from 7475 T7351 aluminium alloy were carried out. The results indicated that simultaneously evaluating fatigue crack increments after application of the load amplitude above J Q and subcritical increments caused by the loads at high stress intensity factors is difficult. Experiments demonstrated that if the fatigue crack reaches a specific length, the maximal amplitude load induces considerable crack growth retardation.

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Study on Stress Intensity Factor of PMMA with Double Cracks Using Coherent Gradient Sensing (CGS) Technique

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.109.114 ◽

2011 ◽

Vol 109 ◽

pp. 114-119 ◽

Cited By ~ 4

Author(s):

Ling Tao Mao ◽

Cai Ping Liu ◽

Ke Chen ◽

Li Qian An ◽

Xin Xin Zhu

Keyword(s):

Stress Intensity Factor ◽

Stress Intensity ◽

Intensity Factor ◽

Stress Intensity Factors ◽

Fracture Behaviour ◽

Intensity Factors ◽

Gradient Sensing ◽

Coherent Gradient Sensing ◽

Three Point Bending ◽

Fringe Patterns

In this paper, the principle of coherent gradient sensing (CGS) technology is briefly introduced. Fracture behaviour of the PMMA specimens with single or double cracks under three-point-bending are studied using the CGS optical method. A series of CGS fringe patterns under different loading are abtained. With these fringes, stress intensity factors are caculated. The influences of the different spacing on stress intensity factors are discussed. These results will be useful for researching on strength of PMMA materials.

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Numerical study of fractured sandwich beams with homogenous or FGM faces under three point bending

International Journal of Structural Integrity ◽

10.1108/ijsi-05-2014-0022 ◽

2015 ◽

Vol 6 (1) ◽

pp. 142-156

Author(s):

Simonidis D. Vartholomaios ◽

Efstathios E. Theotokoglou

Keyword(s):

Stress Intensity ◽

Stress Intensity Factors ◽

Core Material ◽

Sandwich Beams ◽

Intensity Factors ◽

Displacement Fields ◽

Lower Face ◽

Content Type ◽

Three Point Bending ◽

Material Gradation

Purpose – In this study composite and sandwich beams with homogeneous core and homogeneous or Functional Graded Materials (FGM) faces under three point bending have been confronted. The purpose of this paper is to study numerically sandwich beams with homogeneous core and homogeneous or FGM faces under three point bending and to compare the results for the stress and displacement fields with those resulted of coating – substrate and homogeneous beams. Considering a crack in the lower face sheet to study the influence of the material gradation on the stress intensity factors. Design/methodology/approach – At first a static finite element analysis is performed throughout the composite and sandwich beams, which is taking into account the graded character or not of the faces. For this reason five plane models are considered in order to have a comparable study for the stress and displacement fields of composite beams, which are subjected to three point bending. Second a crack in the lower face is considered parallel to the axis of gradation. When subjected to three point bending, this crack will propagate slowly perpendicular to the lower face. Findings – Computed distributions of the stress fields across the core material and near the interfaces are given for different materials gradation of the faces; and possible crack-initiation positions have been identified. Stress intensity factors are calculated using finite element method, and assuming linear fracture mechanics and plane strain conditions. Originality/value – The originality of the proposed analysis is to investigate for the first time numerically the influence of the FGMs or homogeneous faces in the core material of sandwich beams under three point bending relative to the coating – substrate and to the homogeneous beams. Second to study the influence of a crack in the lower graded face sheet on the overall behavior of the composite beam and to investigate the influence of the material gradation on the values of stress intensity factors.

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