A Measure for the Fracture Toughness of Cement Based Materials

1984 ◽  
Vol 42 ◽  
Author(s):  
Y. S. Jenq ◽  
S. P. Shah
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Direct Method ◽  
Maximum Load ◽  
Nonlinear Finite Element ◽  
Linear Elastic ◽  
Cement Based Materials ◽  
Notch Length ◽  
Elastic Fracture ◽  
A Direct Method

It is frequently reported that the higher the strength of cement based materials, the more brittle is their behavior. It could he useful to quantitatively express the degree of brittleness. Many attempts [1–13] have been made to use linear elastic fracture mechanis (LEFM) to quantitatively express the degree of brittleness. For example, by testing notched beams one can calculate, using the formulas developed from LEFM, a quantity called fracture toughness and termed KIC from the measured maximum load and the initial notch-length. Unfortunalely, it has been observed that K thus calculated is dependent on the dimension of the beams. Many researchers have attempted to analyze this size dependency. Such approaches are usually quite cumbersome and are often based on expensive nonlinear finite element programs. In this paper a direct method is suggested to calculate two size-independent fracture toughness parameters from the experimental results. The method was developed based on tests on notched-beams of different mix proportions and different sizes.

scholarly journals Evaluation of linear-elastic fracture toughness of the teeth restored with different post and core systems

2015 ◽  
Vol 7 (8) ◽  
pp. 125-129
Author(s):  
Lamartine De Moraes Melo Neto Clovis ◽  
Afonso Franciscone Paulo ◽  
Mondelli Jose ◽  
Sbeghen Sabio Silvia ◽  
Lorenzi Poluha Rodrigo ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Post And Core

Crack Propagation Simulation: A Local Deformation-Based Mesh Mapping Method for Crack Modeling and a Direct Method for Residual Stress Representation in Welds

2011 ◽  
Author(s):  
Heqin Xu ◽  
Samer Mahmoud ◽  
Ashok Nana ◽  
Doug Killian
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Crack Front ◽  
Direct Method ◽  
Local Deformation ◽  
Front Shape ◽  
A Direct Method ◽  
Mesh Mapping

Cracks found in a nuclear power plant reactor coolant system (RCS), such as primary water stress corrosion cracking (PWSCC) and intergranular stress corrosion cracking (IGSCC), usually have natural crack front shapes that can be very different from the idealized semi-elliptical or rectangular shapes considered in engineering handbooks and other analytical solutions based on limited shapes. Simplifications towards semi-elliptical shape or rectangular shape may potentially introduce unnecessary conservatism when the simplified shape has to contain the actual crack shape. On the other hand, it is very time-consuming to create a three-dimensional (3D) finite element (FE) model to simulate crack propagation in a natural shape using existing public-domain software like ABAQUS or ANSYS. In this study, a local deformation-based mesh-mapping (LDMM) method is proposed to model cracks with a natural front shape in any 3D structures. This methodology is first applied to model circumferential surface cracks with a natural crack front shape in the cross-sectional plane of a cylinder. The proposed new method can be applied to simulate both shallow and deep cracks. Also discussed in this paper is a direct method to reproduce welding residual stresses in the crack model using temperature fields combined with other sustained loads to predict crack propagations. With this novel LDMM method, natural crack fronts and non-planar crack faces can be easily modeled. The proposed new method can be used to generate a high-quality finite element model that can be used for both linear-elastic fracture mechanics (LEFM) and elastic-plastic fracture mechanics (EPFM) analyses. The study case illustrates that the proposed LDMM method is easy to implement and more efficient than the existing commercial software.

The Damage Tolerance of a Sandwich Panel Containing a Cracked Honeycomb Core

2009 ◽  
Vol 76 (6) ◽  
Author(s):  
I. Quintana Alonso ◽  
N. A. Fleck
Keyword(s):  
Finite Element ◽  
Sandwich Panel ◽  
Finite Element Simulations ◽  
Analytical Models ◽  
Tensile Fracture ◽  
Linear Elastic ◽  
Statistical Variation ◽  
Wall Strength ◽  
Elastic Fracture ◽  
Weibull Theory

The tensile fracture strength of a sandwich panel, with a center-cracked core made from an elastic-brittle diamond-celled honeycomb, is explored by analytical models and finite element simulations. The crack is on the midplane of the core and loading is normal to the faces of the sandwich panel. Both the analytical models and finite element simulations indicate that linear elastic fracture mechanics applies when a K-field exists on a scale larger than the cell size. However, there is a regime of geometries for which no K-field exists; in this regime, the stress concentration at the crack tip is negligible and the net strength of the cracked specimen is comparable to the unnotched strength. A fracture map is developed for the sandwich panel with axes given by the sandwich geometry. The effect of a statistical variation in the cell-wall strength is explored using Weibull theory, and the consequences of a stochastic strength upon the fracture map are outlined.

Development of a New Artificial Knee Joint for an Asian and Middle Eastern Population

2013 ◽  
Author(s):  
Harcharan Singh Ranu
Keyword(s):  
Finite Element ◽  
Body Weight ◽  
Maximum Load ◽  
The Body ◽  
The Other ◽  
Elastic Behavior ◽  
Loading Conditions ◽  
Load Bearing Capacity ◽  
Linear Elastic ◽  
Materials Used

Design of an artificial knee was developed using computer 3-D modeling, the high flexion knee was obtained by using a multi-radii design pattern, The increase of final 20 degrees in flexion was obtained by increasing the condylar radii of curvature. The model of the high flexion knee was developed and one of the models was subjected to finite element modeling and analysis. The compositions of components in the artificial knee were, femoral component and the tibial component were metal, whereas the patellar component and the meniscal insert were made using polyethylene. The metal component used for the analysis in this study was Ti6Al4V and the polyethylene used was UHMWPE. Overall biomaterials chosen were: meniscus (UHMWPE, mass = 0.0183701 kg, volume = 1.97518e-005 m3), tibial component (Ti6Al4V, mass = 0.0584655 kg, volume = 1.32013e-005 m3), femoral component (Ti6Al4V, mass = 0.153122 kg, volume = 3.45742e-005 m3), total artificial assembly (mass = 0.229958 kg, volume = 6.75e-005m3). However, in this design the load had been taken to 10 times the body weight. The weight over single knee is only half the maximum load as the load is shared between the two knee joints. Following were the loading conditions, taking average body weight to be 70Kgs and taking extreme loading conditions of up to 10 times the body weight, i.e. 700Kgs on each of the leg performed the Finite Element Analysis (FEA) over the newly designed knee. The loading was done at an increment of 100 Kgs. The loading conditions and the meshing details for the analysis of the assembly were Jacobian check: 4 points, element size: 0.40735 cm, tolerance: 0.20367 cm, quality: high, number of elements: 80909, number of nodes: 126898. A maximum load of 600 Kgs is optimum for this model. The other components observed linear elastic behavior for the applied loads. Based on these results it was determined that the load bearing capacity of the model were well within the failure levels of the materials used for the analysis. A maximum load of 600 Kgs is optimum for this model. The other components observed linear elastic behavior for the applied loads. Based on these results it was determined that the load bearing capacity of the model were well within the failure levels of the materials used for the analysis. Conclusion drawn from this is that for the first time an innovative new design of an artificial knee joint to suite a segment of some religious population has been developed. This allows them to pray, bend in different positions and squat without too much difficulty.

SIFs for Radial Cracks in Annular Discs Under Internal and External Shrinkage Pressure and Constant Angular Velocity

2007 ◽  
Author(s):  
A. Sakhaee-Pour ◽  
A. R. Gowhari-Anaraki ◽  
S. J. Hardy
Keyword(s):  
Finite Element ◽  
Angular Velocity ◽  
Constant Angular Velocity ◽  
Coefficient Of Determination ◽  
Linear Elastic ◽  
Crack Configuration ◽  
Wide Range ◽  
Elastic Fracture ◽  
Radial Cracks

Finite element method has been implemented to predict stress intensity factors (SIFs) for radial cracks in annular discs under constant angular velocity. Effects of internal and external uniform pressure on the SIFs have also been considered. Linear elastic fracture mechanics finite element analyses have been performed and results are presented in the form of crack configuration factors for a wide range of components and crack geometry parameters. These parameters are chosen to be representative of typical practical situations. The extensive range of crack configuration factors obtained from the analyses is then used to develop equivalent prediction equations via a statistical multiple non-linear regression model. The accuracy of this model is measured using a multiple coefficient of determination, R2, where 0 ≤ R2 ≤ 1. This coefficient is found to be greater than or equal to 0.98 for all cases considered in this study, demonstrating the quality of the model fit to the data. These equations for the SIFs enable designers to predict fatigue life of the components easily.

Validation of Linear Elastic Fracture Mechanics in Predicting the Fracture Toughness of Polyethylene Pipe Materials

2015 ◽  
Author(s):  
Tarek M. A. A. El-Bagory ◽  
Hossam E. M. Sallam ◽  
Maher Y. A. Younan
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Linear Elastic Fracture Mechanics ◽  
Operating Conditions ◽  
Specimen Thickness ◽  
Crosshead Speed ◽  
Linear Elastic ◽  
Piping Systems ◽  
Elastic Fracture ◽  
Point Bend

The main purpose of the present paper is to compare between the fracture toughness based on linear elastic fracture mechanics (GIC), and that based on nonlinear fracture mechanics (JIC). The material of the investigated pipe is a high-density polyethylene (HDPE), which is commonly used in natural gas piping systems. The welds at the pipe junction are produced by butt-fusion (BF), welding. Curved three-point bend (CTPB), fracture specimens are used. The crosshead speed ranged from 5 to 500 mm/min and specimen thickness ranged from 9 to 45mm for both welded and unwelded specimens at room temperature Ta, equal 23°C. The study reveals that the crosshead speed has a significant effect on the fracture toughness of both welded and unwelded specimens. The results of GIC for different specimen thickness and crosshead speed found previously by the authors [1] have been compared with JIC under the same operating conditions [2]. The comparison between welded and unwelded specimens revealed that in the welded specimens there is a marginal difference between fracture toughness measured using linear elastic fracture mechanics LEFM and elastic plastic fracture mechanics EPFM, for both crosshead speeds.

scholarly journals Explanation of tension-side notch design provisions for glulam in CSA Standard 086-14

2015 ◽  
Vol 42 (10) ◽  
pp. 787-796 ◽  
Author(s):  
Ian Smith ◽  
Henry Meleki Kiwelu ◽  
Jan Weckendorf
Keyword(s):  
World War Ii ◽  
Solid Wood ◽  
Shear Capacity ◽  
World War ◽  
Linear Elastic ◽  
Depth Ratio ◽  
Glued Laminated Timber ◽  
The Usa ◽  
Notch Length ◽  
Elastic Fracture

Traditionally unreinforced tension-side notches at supports of glued-laminated-timber (glulam) bending members have been designed in Canada assuming shear capacity is reduced in proportion to the square of the residual depth ratio. The origin of that practice lies in World War II era studies in the USA on solid wood members. More recent research in Canada, US, and Europe has focussed on application of linear elastic fracture mechanics (LEFM) methods to such problems, reflecting that such approaches can account for effects of variables other than notch depth ratio. Canadian wood design code CSA Standard 086 “Engineering Design in Wood” first capitalized on availability of LEFM approaches in 1994 by adopting such a method for design of sawn lumber members with tension-side notches at supports. The same was not done then for glulam members because of paucity of supporting test data. That gap has now been filled and the 2014 edition of CSA Standard 086 employs consistent LEFM based design approaches for both sawn lumber and glulam members with tension-side notches. New provisions for glulam recognize influences that notch length and shape, and how laminations in members are fabricated have on member capacities. Discussion here addresses the logic that underpins the new glulam provisions and how application of those provisions impacts design solutions. Overall impact of the new design provisions is to discourage use of relatively large tension-side notches at supports of larger glulam bending members, while not discouraging use of notches in smaller glulam members.

Mechanical Modal and Numerical Simulation of Fracture Process of Block Wall

2011 ◽  
Vol 217-218 ◽  
pp. 1438-1443
Author(s):  
Yan Li ◽  
Xin Sheng Yin ◽  
Bo Wang
Keyword(s):  
Numerical Simulation ◽  
Fracture Toughness ◽  
Fracture Process ◽  
Concrete Block ◽  
Critical Value ◽  
Specimen Size ◽  
Linear Elastic ◽  
Block Wall ◽  
Elastic Fracture ◽  
Aerated Concrete

Aerated concrete is a typical non-uniform quasi-brittle materials, the fracture process is very complicated. To slove the problem of cracks in this block walls, a practical analytical method was proposed based on the vertical mortar joint model to solve the equivalent fracture toughness (the critical value which the crack occurred to spread unstable) With the use of the basic principle of composite material mechanics and linear elastic fracture mechanics. Against the results of the related experiments, the standard deviation and the coefficient of variation of Analytical Solution are smaller, , and the equivalent fracture toughness is the effective fracture parameters of independent of specimen size. So the suggested method is more feasible and applicable, which can forecast autoclaved aerated concrete block wall’s cracking and destroying.

Fatigue analysis of groove weld with steel bar backing by fracture mechanics finite elements

1988 ◽  
Vol 15 (4) ◽  
pp. 524-533 ◽  
Author(s):  
Farid Taheri ◽  
Aftab A. Mufti
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Stress Ratio ◽  
Stress Range ◽  
Cyclic Life ◽  
Linear Elastic ◽  
Steel Bar ◽  
Elastic Fracture ◽  
Number Of Cycles ◽  
Cycles To Failure

The purpose of this paper is to analyze the fatigue crack growth rate in groove weld with backing steel bar. The linear elastic fracture mechanics approach is used. This approach is coded in a special purpose fracture mechanics package FAST. By using FAST, the structure is modeled and analyzed by its finite element module FAST-I, and the cyclic life is estimated by its crack propagation module FAST-II.An example recently studied by Baker and Kulak is investigated by the FAST program. The S–N curve (stress range versus number of cycles to failure) obtained by FAST is compared with the curve presented by Baker and Kulak. Key words: Engineering, finite element, fracture mechanics, fatigue, steel, stress intensity factor, numerical, computer analysis, weld, stress ratio, enriched element.

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