Fracture Behaviour of Modified Spruce Wood: A Study Using Linear and Non Linear Fracture Mechanics

Holzforschung ◽  
2002 ◽  
Vol 56 (2) ◽  
pp. 191-198 ◽  
Author(s):  
Alexander Reiterer ◽  
Gerhard Sinn
Keyword(s):  
Fracture Energy ◽  
Heat Treatments ◽  
Critical Stress Intensity Factor ◽  
Mode I ◽  
Mode Iii ◽  
Fracture Properties ◽  
Specific Fracture Energy ◽  
Wedge Splitting Test ◽  
Splitting Test ◽  
Specific Fracture

Summary The fracture properties of unmodified and modified (heat treatments under various conditions and acetylation) sprucewood are investigated using the wedge splitting test. Fracture parameters measured include critical stress intensity factor and specific fracture energy under Mode I loading and specific fracture energy under Mode III loading. The Mode I fracture properties are reduced by all kinds of modification. However, acetylation leads to a reduction of only 20%whereas heat treatments reduce the properties to a much greater extent, approximately 50%to 80%. The Mode III fracture properties are influenced less. SEM pictures of the fracture surfaces support the described findings.

Damage and Fracture Mechanisms during Mode I and III Loading of Wood

Holzforschung ◽  
2001 ◽  
Vol 55 (5) ◽  
pp. 525-533 ◽  
Author(s):  
E.K. Tschegg ◽  
K. Frühmann ◽  
S.E. Stanzl-Tschegg
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Fracture Energy ◽  
Fracture Mechanisms ◽  
Mode I ◽  
Mode Iii ◽  
Initiation Energy ◽  
Specific Fracture Energy ◽  
Damage And Fracture ◽  
Specific Fracture

Summary Tests under mode I and mode III loading were performed on side grooved Compact-Tension specimens of larch and beech under steady state crack propagation to study the damage and fracture behaviour and the influence of two fibre orientations. From the complete load-displacement diagram, all important damage and fracture mechanical values (stiffness/compliance, microstructural damage, crack initiation energy, specific fracture energy, etc.) have been determined. Crack initiation energy and specific fracture energy are approximately ten times higher for mode III loading than for mode I loading in both wood species. Crack initiation occurs in mode III under external mode III loading, crack propagation, however, takes place under mode I, owing to crack surface interference. The influence of fibre orientation on the (fracture) mechanical properties of beech and larch is different. This difference may be explained mainly by the high number of rays in beech.

scholarly journals Wedge-Splitting Test on Carbon-Containing Refractories at High Temperatures

2019 ◽  
Vol 9 (16) ◽  
pp. 3249 ◽  
Author(s):  
Stückelschweiger ◽  
Gruber ◽  
Jin ◽  
Harmuth
Keyword(s):  
Tensile Strength ◽  
Fracture Energy ◽  
Laser Speckle ◽  
Displacement Measurement ◽  
Ambient Atmosphere ◽  
Specific Fracture Energy ◽  
Wedge Splitting Test ◽  
Splitting Test ◽  
Specific Fracture ◽  
Wedge Splitting

The mode I fracture behavior of ordinary refractory materials is usually tested with the wedge-splitting test. At elevated temperatures, the optical displacement measurement is difficult because of the convection in the furnace and possible reactions of refractory components with the ambient atmosphere. The present paper introduces a newly developed testing device, which is able to perform such experiments up to 1500 °C. For the testing of carbon-containing refractories a gas purging, for example, with argon, is possible. Laser speckle extensometers are applied for the displacement measurement. A carbon-containing magnesia refractory (MgO–C) was selected for a case study. Based on the results obtained from tests, fracture mechanical parameters such as the specific fracture energy and the nominal notch tensile strength were calculated. An inverse simulation procedure applying the finite element method yields tensile strength, the total specific fracture energy, and the strain-softening behavior. Additionally, the creep behavior was also considered for the evaluation.

Fracture Energy Test for Highway Concrete: Determining the Effect of Coarse Aggregate on Crack Propagation Resistance

2000 ◽  
Vol 1730 (1) ◽  
pp. 10-17 ◽  
Author(s):  
Elin A. Jensen ◽  
Will Hansen
Keyword(s):  
Fracture Toughness ◽  
Blast Furnace ◽  
Crack Propagation ◽  
Fracture Energy ◽  
Blast Furnace Slag ◽  
Coarse Aggregate ◽  
Fracture Properties ◽  
Specific Fracture Energy ◽  
Specific Fracture ◽  
Furnace Slag

Portland cement concrete fracture properties—specific fracture energy, fracture toughness, and brittleness—were investigated for typical Michigan highway concretes containing different coarse aggregates and varying in age: 7,28, and 91 days. These fracture properties can be determined from the complete load-deflection curve of a notched beam. The effective beam is 965 mm long, 100 mm wide, and 200 mm high, with a 100-mm center notch. Results show that the specific fracture energy, which determines the resistance to crack propagation, for a concrete pavement mix is controlled primarily by the coarse aggregate type. Differences of 100 percent were obtained between aggregate types. A glacial gravel yielded the highest resistance (160 N/m), and the dolomitic limestones and blast furnace slag yielded the lowest resistance (80–100 N/m), although the concretes all had similar strength properties. The fracture toughness, resistance to crack initiation, was found to be linear related with concrete strength. Typically this results in improved early age fracture toughness for concretes containing dolomitic limestone and blast furnace slag as coarse aggregate, compared to glacial gravel, because natural aggregate concrete typically has slower strength gain initially. Concrete brittleness, based on the entire load-deflection response, showed that concretes containing stronger coarse aggregate, such as glacial gravel, are significantly less brittle at early ages than are concretes containing weaker aggregate. However, these stronger aggregate concretes become more brittle, and thus crack sensitive, over time.

Simulation of Refractory Fracture as a Tool for Advanced Material Testing

2014 ◽  
Vol 92 ◽  
pp. 232-241
Author(s):  
Dietmar Gruber ◽  
Sheng Li Jin ◽  
Harald Harmuth
Keyword(s):  
Tensile Strength ◽  
Fracture Energy ◽  
Test Method ◽  
Evaluation Procedure ◽  
Crack Model ◽  
Refractory Materials ◽  
Specific Fracture Energy ◽  
Splitting Test ◽  
Specific Fracture ◽  
Ceramic Refractory

The work presented here deals with simulation assisted evaluation of fracture testing of ordinary ceramic refractory materials. Two tests are applied. One of them, a wedge splitting test, is already established for this purpose. An inverse evaluation procedure was developed to derive more information from the test results: It enables the simultaneous determination of the specific fracture energy, the tensile strength and the Young’s modulus. Moreover specific fracture energy can also be determined in the case that the test has to be interrupted at some residual load due to relatively low material brittleness. The other test method, a laser irradiation disc test, was developed in order to determine specific fracture energy and tensile strength for fine ceramic refractory materials behaving relatively brittle. From the time elapsed until crack initiation occurs (t1) and a stable/instable transition of crack propagation takes place (t2), respectively, the tensile strength and the specific fracture energy are calculated based on a simulation of the mode I fracture behavior which applies the fictitious crack model according to Hillerborg.

Studies on effect of steel fiber and coarse aggregate on fracture properties of self compacting concrete using wedge splitting test

2019 ◽  
Vol 11 (6) ◽  
pp. 751-767
Author(s):  
Raja Rajeshwari B. ◽  
Sivakumar M.V.N.
Keyword(s):  
Fracture Energy ◽  
Coarse Aggregate ◽  
Peak Load ◽  
Mouth Opening ◽  
Test Method ◽  
Crack Mouth Opening Displacement ◽  
Fine Aggregate ◽  
Content Type ◽  
Fracture Properties ◽  
Splitting Test

Purpose Fracture properties depend on the type of material, method of testing and type of specimen. The purpose of this paper is to evaluate fracture properties by adopting a stable test method, i.e., wedge split test. Design/methodology/approach Coarse aggregate of three different sizes (20 mm, 16 mm and 12.5 mm), three ratios of coarse aggregate, fine aggregate (CA:FA) (50:50, 45:55, 40:60), presence of steel fibers, and specimens without and with guide notch were chosen as parameters of the study. Findings Load-crack mouth opening displacement curves indicate that for both fibrous and non-fibrous mixes, higher volume of aggregate and higher size of coarse aggregate have high fracture energy. Originality/value For all volumes of coarse aggregate, it was noticed that specimens with 12.5 mm aggregate size achieved highest peak load and abrupt drop post-peak. The decrease in coarseness of internal structure of concrete (λ) resulted in the increase of fracture energy.

scholarly journals Probabilistic Fracture Energy Assessment of Natural Fibre Reinforced Concrete by Two Parameter Weibull Distribution

2018 ◽  
Vol 7 (3.12) ◽  
pp. 407
Author(s):  
Neha P Asrani ◽  
Murali G ◽  
Arthika J ◽  
Karthikeyan. K ◽  
Haridharan. M.K
Keyword(s):  
Weibull Distribution ◽  
Fracture Energy ◽  
Plain Concrete ◽  
Natural Fibre ◽  
Test Results ◽  
Specific Fracture Energy ◽  
Energy Assessment ◽  
Experimental Process ◽  
Specific Fracture ◽  
Two Parameter

Fracture energy is the post-crack energy absorption ability of the material that represents the energy absorbed by the structure at the time of failure. Its analysis has gained importance and hence requires a powerfulmethod for its development. A two parameter Weibull distribution proves to be an efficient tool in analysing the scattered experimental test results. In this paper, the specific fracture energy of plain concrete and concrete reinforced with natural fibres of hemp, wheat straw and elephant grass are statistically analysed by two parameter Weibull distribution by using graphical method. For determining Weibull parameters, 21 equations have been used and the best equation is taken for the reliability analysis. A Weibull reliability curve is plotted, which shows the specific fracture energy at each reliability level. This curve enables an engineer to choose the fracture energy of a particular mix based on its reliability requirement and safety limit. Therefore, reliability curves are a pioneer in statistical analysis as they eliminate the time-consuming and costly experimental process. This method can be applied in areas with similar uncertainties.  

Fracture Energy of Elastomers in Mode I (Cleavage) and Mode III (Lateral Shear)

1975 ◽  
Vol 48 (5) ◽  
pp. 896-901 ◽  
Author(s):  
A. Ahagon ◽  
A. N. Gent ◽  
H. J. Kim ◽  
Y. Kumagai
Keyword(s):  
Fracture Energy ◽  
Strain Energy ◽  
Sheet Thickness ◽  
Shear Mode ◽  
Mode I ◽  
Input Energy ◽  
Mode Iii ◽  
Lateral Shear ◽  
Test Sheet ◽  
Filled Elastomers

Abstract Attention has been drawn here to three different reasons why measurements of fracture energy by different methods may not agree: (1) When the test involves propagation of a tear by stored strain energy, as in the method shown in Figure 1, the energy available to cause rupture will be less than that supplied, because of dissipation within the elastomer. Calculation of the fracture energy on the basis of input energy would then lead to an overestimate, by about 100 per cent or more for typical filled elastomers. (2) As shown in Figures 4a and 5, the tear path is sometimes wider than the thickness of the test sheet. In consequence, fracture energy calculated from the sheet thickness would be too large, by about 40 per cent in the cases considered here. (3) Even when allowance is made for the true width of the tear path, measurements of fracture energy in shear (Mode III) are about 50 per cent larger than in cleavage (Mode I). This is attributed to frictional work expended in sliding the rough torn surfaces past each other.

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