The fracture of wood in tension parallel to the grain

1977 ◽  
Vol 4 (4) ◽  
pp. 412-416 ◽  
Author(s):  
Sidney Mindess
Keyword(s):  
Fracture Toughness ◽  
Flexural Strength ◽  
Physical Interpretation ◽  
Crack Extension ◽  
High Moisture ◽  
Linear Elastic ◽  
Moisture Contents ◽  
Apparent Fracture Toughness ◽  
Elastic Fracture ◽  
Uncracked Ligament

The fracture of commercial Hem-Fir boards in the LR and LT modes was studied, using both saturated and air-dry specimens. Notched samples were tested in flexure (third-point loading). It was found that the concepts of linear elastic fracture mechanics could be applied, even when the crack extension was in a direction perpendicular to the initial notch. However, the physical interpretation of the apparent fracture toughness, [Formula: see text], remains unclear. It was also found that the apparent flexural stsrength increased as the size of the uncracked ligament decreased. Finally, the results indicated that both the nominal flexural strength and the fracture toughness were greater for the saturated specimens, probably due to an increase in viscoelastic behaviour at high moisture contents.

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.

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

Stress Corrosion Cracking Behavior of Uranium Alloys

CORROSION ◽  
1974 ◽  
Vol 30 (5) ◽  
pp. 181-189 ◽  
Author(s):  
W. F. CZYRKLIS ◽  
M. LEVY
Keyword(s):  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Threshold Stress ◽  
Crack Extension ◽  
Corrosion Cracking ◽  
Nacl Solution ◽  
Cracking Behavior ◽  
Linear Elastic ◽  
Elastic Fracture

Abstract The stress corrosion cracking (SCC) behavior of U-3/4% Ti, and uranium alloys 3/4% Quad, 1% Quad, and 1% Quint have been studied utilizing a linear elastic fracture mechanics approach. The threshold stress intensities for stress corrosion crack propagation for these alloys have been determined in distilled H2O and NaCl solutions containing 50 ppm Cl− and 21,000 ppm Cl−. All of the alloys studied may be classified as very susceptible to SCC in aqueous solutions since they exhibit SCC in distilled H2O (<1 ppm Cl−) and have low KIscc values in NaCl solutions. Crack extension in all of the alloys in all environments was transgranular and failure occurred by brittle quasicleavage fracture in NaCl solution.

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.

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.

Fracture Toughness Study on Zr-based Bulk Metallic Glasses

2007 ◽  
Vol 1048 ◽  
Author(s):  
Jin-yoo Suh ◽  
Mary Laura Lind ◽  
C. Paul Kim ◽  
R. Dale Conner ◽  
William L Johnson
Keyword(s):  
Electron Microscopy ◽  
Fracture Toughness ◽  
Metallic Glasses ◽  
Shear Bands ◽  
Bulk Metallic Glasses ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Fracture Surfaces ◽  
Linear Elastic ◽  
Elastic Fracture

AbstractThe fracture toughness of Zr-based bulk metallic glasses of various compositions was studied in the as-cast and annealed condition. Properties were characterized using x-ray and differential scanning calorimetry (DSC) and fracture surfaces were examined using electron microscopy (SEM). Quaternary Zr-Ti-Cu-Be alloys consistently had linear elastic fracture toughness values greater than 80 MPa·m1/2, while Vitreloy 1, a Zr-Ti-Cu-Ni-Be alloy, had an average fracture toughness of 48.5 MPa·m1/2 with a large amount of scatter. The addition of iron to Vitreloy 1 reduced the fracture toughness to 25 MPa·m1/2. Fracture surfaces were carefully analyzed using electron microscopy. Some samples had highly jagged patterns at the beginning stage of crack propagation, and the roughness of this jagged pattern correlated well with the measured fracture toughness values. These jagged patterns, the main source of energy dissipation in the sample, were attributed to the formation of shear bands inside the sample. The Zr-Ti-Cu-Be alloy, having KQ=85 MPa·m1/2 as cast, was annealed at various time/temperature combinations. When the alloy was annealed 50°C below Tg, the fracture toughness dropped to 6 MPa·m1/2, while DSC and X-ray showed the alloy to still be amorphous. The roughness of the fracture surfaces on relaxed samples also compared well with the relative fracture toughness.

scholarly journals Void Content and its Influence on the Fracture Behaviour of Long Fibre Reinforced Injection Molded Polypropylene

2004 ◽  
Vol 13 (6) ◽  
pp. 096369350401300
Author(s):  
Victor Iliev Rizov
Keyword(s):  
Fracture Toughness ◽  
Testing Machine ◽  
Compact Tension ◽  
Void Content ◽  
Linear Elastic ◽  
Static Testing ◽  
Glass Fibre Reinforced ◽  
Injection Molded ◽  
Elastic Fracture ◽  
Static Testing Machine

The influence of void content on the fracture performance of discontinuous long glass fibre reinforced injection molded polypropylene was studied. Compact tension specimens were machined from simple plate-tools and were loaded in a static testing machine in a laboratory environment. From the resulting load-displacement curves the fracture toughness was determined on the basis of the linear elastic fracture mechanics. It was found that higher void content causes a decrease in the fracture toughness.

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.

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