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.

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 Fatigue Crack Growth under Non-Proportional Mixed Mode Loading in Rail and Wheel Steel Part 2: Sequential Mode I and Mode III Loading

2019 ◽  
Vol 9 (14) ◽  
pp. 2866 ◽  
Author(s):  
Makoto Akama ◽  
Akira Kiuchi
Keyword(s):  
Crack Growth ◽  
Mixed Mode ◽  
Fatigue Cracks ◽  
Rolling Contact ◽  
Material Strength ◽  
Shear Mode ◽  
Mode I ◽  
Mode Iii ◽  
Plane Shear ◽  
Branch Crack

Rolling contact fatigue cracks in rail and wheel undergo non-proportional mixed mode I/II/III loading. Fatigue tests were performed to determine the coplanar and branch crack growth rates on these materials. Sequential and overlapping mode I and III loading cycles were applied to single cracks in round bar specimens. Experiments in which this is done have been rarely performed. The fracture surface observations and the finite element analysis results suggested that the growth of long (does not branch but grown stably and straight) coplanar cracks was driven mainly by mode III loading. The cracks tended to branch when increasing the material strength and/or the degree of overlap between the mode I and III loading cycles. The equivalent stress intensity factor range that can consider the crack face contact and successfully regressed the crack growth rate data is proposed for the branch crack. Based on the results obtained in this study, the mechanism of long coplanar shear-mode crack growth turned out to be the same regardless of whether the main driving force is in-plane shear or out-of-plane shear.

Stress Intensity Factors for Cracks Emanating from a Notch under Shear-Mode Loading

2018 ◽  
Vol 774 ◽  
pp. 48-53
Author(s):  
Jana Horníková ◽  
Pavel Šandera ◽  
Stanislav Žák ◽  
Jaroslav Pokluda
Keyword(s):  
Stress Intensity ◽  
Critical Length ◽  
Shear Mode ◽  
Mode I ◽  
Mode Ii ◽  
Mode Iii ◽  
Loading Mode ◽  
Notch Stress ◽  
Notch Geometry ◽  
Mode Ii Loading

The influence of the notch geometry on the stress intensity factor at the front of the emanating cracks is well known for the opening loading mode. The critical length of the crack corresponding to a vanishing of the influence of the notch stress concentration can be approximately expressed by the formula aI,c = 0.5ρ(d/ρ)1/3, where d and ρ are the depth and radius of the notch, respectively. The aim of the paper was to find out if this formula could be, at least nearly, applicable also to the case of shear mode loading. The related numerical calculations for mode II and III loading were performed using the ANSYS code for various combinations of notch depths and crack lengths in a cylindrical specimen with a circumferential U-notch. The results revealed that, for mode II loading, the critical length was much higher than that predicted by the formula for mode I loading. On the other hand, the critical lengths for mode I and mode III were found to be nearly equal.

scholarly journals Comparative study of elastic properties and mode I fracture energy of carbon nanotube/epoxy and carbon fibre/epoxy laminated composites

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Jyotikalpa Bora ◽  
Sushen Kirtania
Keyword(s):  
Carbon Nanotube ◽  
Carbon Fibre ◽  
Fracture Energy ◽  
Elastic Properties ◽  
Volume Fraction ◽  
Laminated Composites ◽  
Laminated Composite ◽  
Fe Analysis ◽  
Mode I ◽  
Mode I Fracture

Abstract A comparative study of elastic properties and mode I fracture energy has been presented between conventional carbon fibre (CF)/epoxy and advanced carbon nanotube (CNT)/epoxy laminated composite materials. The volume fraction of CNT fibres has been considered as 15%, 30%, and 60% whereas; the volume fraction of CF has been kept constant at 60%. Three stacking sequences of the laminates viz.[0/0/0/0], [0/90/0/90] and [0/30/–30/90] have been considered in the present analysis. Periodic microstructure model has been used to calculate the elastic properties of the laminated composites. It has been observed analytically that the addition of only 15% CNT in epoxy will give almost the same value of longitudinal Young’s modulus as compared to the addition of 60% CF in epoxy. Finite element (FE) analysis of double cantilever beam specimens made from laminated composite has also been performed. It has been observed from FE analysis that the addition of 15% CNT in epoxy will also give almost the same value of mode I fracture energy as compared to the addition of 60% CF in epoxy. The value of mode I fracture energy for [0/0/0/0] laminated composite is two times higher than the other two types of laminated composites.

scholarly journals Antiplane–inplane shear mode delamination between two second-order shear deformable composite plates

2016 ◽  
Vol 22 (3) ◽  
pp. 259-282 ◽  
Author(s):  
András Szekrényes
Keyword(s):  
Plate Theory ◽  
Plate Thickness ◽  
State Space Model ◽  
Boundary Surface ◽  
Plate Boundary ◽  
Composite Plates ◽  
Second Order ◽  
Shear Mode ◽  
Mode Iii ◽  
Double Plate System

The second-order laminated plate theory is utilized in this work to analyze orthotropic composite plates with asymmetric delamination. First, a displacement field satisfying the system of exact kinematic conditions is presented by developing a double-plate system in the uncracked plate portion. The basic equations of linear elasticity and Hamilton’s principle are utilized to derive the system of equilibrium and governing equations. As an example, a delaminated simply supported plate is analyzed using Lévy plate formulation and the state-space model by varying the position of the delamination along the plate thickness. The displacements, strains, stresses and the J-integral are calculated by the plate theory solution and compared with those by linear finite-element calculations. The comparison of the numerical and analytical results shows that the second-order plate theory captures very well the mechanical fields. However, if the delamination is separated by only a relatively thin layer from the plate boundary surface, then the second-order plate theory approximates badly the stress resultants and so the mode-II and mode-III J-integrals and thus leads to erroneous results.

Rock fracture under anti-plane shear (Mode III) loading

2005 ◽  
Vol 12 (S1) ◽  
pp. 125-128 ◽  
Author(s):  
Qiu-hua Rao ◽  
Zhen-feng Liao
Keyword(s):  
Rock Fracture ◽  
Shear Mode ◽  
Mode Iii ◽  
Plane Shear
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