scholarly journals Impact of specific fracture energy investigated in front of the crack tip of three-point bending specimen

2017 ◽  
Vol 11 (41) ◽  
pp. 183-190
Author(s):  
J. Klon ◽  
J. Sobek ◽  
L. Malíkova ◽  
S. Seitl
Keyword(s):  
Fracture Energy ◽  
Crack Tip ◽  
Three Point Bending ◽  
Specific Fracture Energy ◽  
Specific Fracture

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.

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.  

Utilization of Williams’ Power Series for Estimation of Crack Behavior under Mixed-Mode Loading

2019 ◽  
Vol 827 ◽  
pp. 203-208
Author(s):  
Lucie Malíková ◽  
Petr Miarka ◽  
Hana Šimonová
Keyword(s):  
Fracture Mechanics ◽  
Mixed Mode ◽  
Crack Tip ◽  
Field Approximation ◽  
Bending Test ◽  
Mixed Mode Loading ◽  
Three Point Bending ◽  
Crack Behavior ◽  
Higher Order Terms ◽  
Specific Fracture

Multi-parameter fracture mechanics concept has been applied to investigate crack behavior under mixed-mode loading, particularly in a semi-circular bending disc. The so-called Williams’ series expansion is used for the crack-tip stress field approximation. It has been shown that application of the generalized fracture mechanics concept can be crucial for materials with specific fracture behavior, such as elastic-plastic or quasi-brittle one, when fracture occurs not only in the very vicinity of the crack tip, but also in a more distant surrounding. Then, considering the higher-order terms of the Williams’ expansion in fracture criteria can be helpful. The attention is devoted to the analysis of the influence of various distances between the supports during the three-point bending test on the results of the further crack propagation direction.

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 Dynamic crack propagation in weak snowpack layers: Insights from high-resolution, high-speed photography

2021 ◽  
Author(s):  
Bastian Bergfeld ◽  
Alec van Herwijnen ◽  
Benjamin Reuter ◽  
Grégoire Bobillier ◽  
Jürg Dual ◽  
...  
Keyword(s):  
High Resolution ◽  
Crack Propagation ◽  
Fracture Energy ◽  
High Speed ◽  
Image Correlation ◽  
Crack Speed ◽  
Specific Fracture Energy ◽  
Weak Layer ◽  
Specific Fracture ◽  
Insight Into

Abstract. To assess snow avalanche release probability, information on failure initiation and crack propagation in weak snowpack layers underlying cohesive slab layers are required. With the introduction of the Propagation Saw Test (PST) in the mid-2000s, various studies used particle tracking analysis of high-speed video recordings of PST experiments to gain insight into crack propagation processes, including slab bending, weak layer collapse, crack propagation speed and the frictional behavior after weak layer fracture. However, the resolution of the videos and the methodology used did not allow insight into dynamic processes such as the evolution of crack speed within a PST or the touchdown distance, which is the length from the crack tip to the trailing point where the slab sits on the crushed weak layer at rest again. Therefore, to study the dynamics of crack propagation we recorded PST experiments using a powerful portable high-speed camera with a horizontal resolution of 1280 pixels at rates up to 20,000 frames per second. By applying a high-density speckling pattern on the entire PST column, we then used digital image correlation (DIC) to derive high-resolution displacement and strain fields in the slab, weak layer, and substrate. The high frame rates allowed time derivatives to obtain velocity and acceleration fields. On the one hand, we demonstrate the versatile capabilities and accuracy of the DIC method by showing three PST experiments resulting in slab fracture, crack arrest and full propagation. On the other hand, we present a methodology to determine relevant characteristics of crack propagation: the crack speed and touchdown distance within a PST, and the specific fracture energy of the weak layer. To estimate the effective elastic modulus of the slab and weak layer as well as the weak layer specific fracture energy we used a recently proposed mechanical model. A comparison to already established methods showed good agreement. Furthermore, our methodology also provides insight into the three different propagation results found with the PST and reveals intricate dynamics that are otherwise not accessible.

Identification of AAAS Composites Mechanical Fracture Parameters

2021 ◽  
Vol 322 ◽  
pp. 66-71
Author(s):  
Martin Lipowczan ◽  
David Lehký ◽  
Iva Rozsypalová ◽  
Petr Daněk ◽  
Pavla Rovnaníková ◽  
...  
Keyword(s):  
Fracture Energy ◽  
Modulus Of Elasticity ◽  
Crack Mouth Opening Displacement ◽  
Crack Model ◽  
Mechanical Fracture ◽  
Specific Fracture Energy ◽  
Static Modulus ◽  
Fracture Parameters ◽  
Static Modulus Of Elasticity ◽  
Specific Fracture

The paper deals with selected alkali-activated aluminosilicate (AAAS) composites based on ceramic precursors in terms of characterization by mechanical fracture parameters. Two composites made of brick dust as a precursor and an alkaline activator with a silicate modulus Ms = 1.0 were investigated. The composites differed in the fineness of grinding of the precursor – in the first set it was 0 to 1 mm, in the second set 0 to 0.3 mm. The filler was crushed brick. The test specimens had nominal dimensions of 40 × 40 × 160 mm and were provided with notches in the middle of the span up to 1/3 of the depth of the specimens after 28 days of hardening. Five to six specimens from each composite set were tested. The specimens were subjected to three-point bending tests, in which force vs. displacement (deflection in the middle of the span) diagrams (F–d diagrams) and force vs. crack mouth opening displacement (F–CMOD) diagrams were recorded. After correction of these diagrams, the values of static modulus of elasticity, effective fracture toughness, effective toughness and specific fracture energy were determined using the Effective Crack Model and the Work-of-Fracture method. After the fracture experiments, the values of informative compressive strength were determined on one of the fractured parts. At the same time, the values of static modulus of elasticity, tensile strength and specific fracture energy were identified using artificial neural networks and F–d diagrams measured and simulated in the ATENA FEM software. All evaluations included the determination of basic statistics of parameters.

Sign in / Sign up

Export Citation Format

Share Document