scholarly journals Direct Evaluation of Mixed Mode I+II Cohesive Laws of Wood by Coupling MMB Test with DIC

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 374
Author(s):  
Jorge Oliveira ◽  
José Xavier ◽  
Fábio Pereira ◽  
José Morais ◽  
Marcelo de Moura
Keyword(s):  
Mixed Mode ◽  
Crack Tip ◽  
Linear Functions ◽  
Image Correlation ◽  
Bending Test ◽  
Mode I ◽  
Cohesive Law ◽  
Crack Tip Opening Displacement ◽  
Direct Evaluation ◽  
Cohesive Laws

Governing cohesive laws in mixed mode I+II loading of Pinus pinaster Ait. are directly identified by coupling the mixed mode bending test with full-field displacements measured at the crack tip by Digital Image Correlation (DIC). A sequence of mixed mode ratios is studied. The proposed data reduction relies on: (i) the compliance-based beam method for evaluating strain energy release rate; (ii) the local measurement of displacements to compute the crack tip opening displacement; and (iii) an uncoupled approach for the reconstruction of the cohesive laws and its mode I and mode II components. Quantitative parameters are extracted from the set of cohesive laws components in function of the global phase angle. Linear functions were adjusted to reflect the observed trends and the pure modes (I and II) fracture parameters were estimated by extrapolation. Results show that the obtained assessments agree with previous experimental measurements addressing pure modes (I and II) loadings on this wood species, which reveals the appropriateness of the proposed methodology to evaluate the cohesive law under mixed mode loading and its components.

Cohesive Laws for Delamination of CFRP: Experiments and Model

2010 ◽  
Author(s):  
Ulf Stigh
Keyword(s):  
Mixed Mode ◽  
Mode I ◽  
J Integral ◽  
Small Length ◽  
Cohesive Law ◽  
Small Length Scale ◽  
Reinforced Composite ◽  
Dcb Specimen ◽  
Cohesive Laws ◽  
Mode Ii Loading

In the present paper, we study delamination of a carbon fibre reinforced composite at a small length scale, i.e. without consideration of crack bridging. The study is performed within the framework of cohesive modelling. We propose methods based on the applications of the path independent J-integral to measure the cohesive law for delamination. With a DCB-specimen, the cohesive law corresponding to mode I loading is measured and with an ENF-specimen, the law corresponding to mode II loading is measured. These laws are used to calibrate a mixed-mode cohesive law. It is argued that the most important parameters of a cohesive law are the ability to provide the correct fracture energy and strength. The cohesive law is developed using a minimum of adjustable parameters to provide a transparent calibration process.

In-Plane Mixed-Mode Fracture of the Thin Sheet Metal

2013 ◽  
Vol 444-445 ◽  
pp. 1301-1304
Author(s):  
Jing Lv ◽  
Bang Cheng Yang ◽  
Chun Ran ◽  
Yong Ping Shao
Keyword(s):  
Crack Initiation ◽  
Mixed Mode ◽  
Crack Extension ◽  
Thin Sheet ◽  
Crack Tip ◽  
Deformation Mode ◽  
Image Correlation ◽  
Mode I ◽  
Mixed Mode Fracture ◽  
Sheet Metals

The length of crack extension under stable crack extension is measured by digital image correlation technology and based on mixed-mode I/II fracture test. Quantitative analyses of the fracture properties are provided for thin sheet metals at stable crack extension under mode I, mode II and mixed-mode I/II loading conditions. The strain field of the crack tip at crack initiation is calculated by VIC-2D. It is suggested that the location of crack initiation is not at the crack tip. The fracture of recycled thin sheet metals is tough due to the large plastic deformation; mode I crack is the most difficult to extend; the load-carrying capacity is the minimum in 45° loading.

scholarly journals The J-integral for mixed-mode loaded cracks with cohesive zones

2020 ◽  
Vol 227 (1) ◽  
pp. 79-94
Author(s):  
Johannes Scheel ◽  
Alexander Schlosser ◽  
Andreas Ricoeur
Keyword(s):  
Cohesive Zone ◽  
Mixed Mode ◽  
Cohesive Zone Model ◽  
Crack Tip ◽  
Constitutive Law ◽  
Zone Model ◽  
J Integral ◽  
Cohesive Law ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement

AbstractThe J-integral quantifies the loading of a crack tip, just as the crack tip opening displacement (CTOD) emanating from the cohesive zone model. Both quantities, being based on fundamentally different interpretations of cracks in fracture mechanics of brittle or ductile materials, have been proven to be equivalent in the late 60s of the previous century, however, just for the simple mode-I loading case. The relation of J and CTOD turned out to be uniquely determined by the constitutive law of the cohesive zone in front of the physical crack tip. In this paper, a J-integral vector is derived for a mixed-mode loaded crack based on the cohesive zone approach, accounting for the most general case of a mode-coupled cohesive law. While the $$J_1$$ J 1 -coordinate, as energy release rate of a straight crack extension, is uniquely related to the cohesive potential at the physical crack tip and thus to the CTOD, the $$J_2$$ J 2 -coordinate depends on the solution of the specific boundary value problem in terms of stresses and displacement gradients at the cohesive zone faces. The generalized relation is verified for the Griffith crack, employing solutions of the Dugdale crack based on improved holomorphic functions.

Atomistic Study of Cleavage and Dislocation Emission in NiAl

1994 ◽  
Vol 364 ◽  
Author(s):  
M. Ludwig ◽  
P. Gumbsch
Keyword(s):  
Finite Element ◽  
Mixed Mode ◽  
Crack Tip ◽  
Mode I ◽  
Crack Plane ◽  
Dislocation Emission ◽  
Dislocation Generation ◽  
Embedded Atom ◽  
Atomistic Study ◽  
Eam Potential

AbstractThe atomistic processes during fracture of NiAl are studied using a new embedded atom (EAM) potential to describe the region near the crack tip. To provide the atomistically modeled crack tip region with realistic boundary conditions, a coupled finite element - atomistic (FEAt) technique [1] is employed. In agreement with experimental observations, perfectly brittle cleavage is observed for the (110) crack plane. In contrast, cracks on the (100) plane either follow a zig-zag path on (110) planes, or emit dislocations. Dislocation generation is studied in more detail under mixed mode I/II loading conditions.

scholarly journals Analysis of Inclined Cracks in Thin-Walled Circular Tube under Mixed-Mode I + II Fracture

Proceedings ◽  
2018 ◽  
Vol 2 (8) ◽  
pp. 517 ◽  
Author(s):  
Boy Raymond Mabuza
Keyword(s):  
Fracture Mechanics ◽  
Mixed Mode ◽  
Crack Tip ◽  
Theoretical Models ◽  
Mode I ◽  
Mixed Mode Fracture ◽  
Shear Stresses ◽  
Inclined Crack ◽  
Mode Fracture ◽  
Thin Walled

This paper provides a study on mixed-mode fracture mechanics in thin-walled tube which is subjected to tension, shear and torsion loading. This type of loading causes an inclined crack to develop and generate a mixture of normal and shear stresses ahead of a crack tip. The stress state ahead of a crack tip is frequently based on mixed-mode type of interactions which designate the amplitude of the crack tip stresses. The analytical expressions for the stress intensity factors for mixed-mode I + II approach are presented. The Paris law for mixed-modes I + II has been discussed. Mixed-mode fracture mechanics is used with theoretical models to predict the path of crack growth when an inclined crack is subjected to a combination of mode I and mode II deformations. The torque at which crack propagation can be expected has been determined. The numerical calculations have been carried out by using MATLAB code. The results are good and could be useful for companies working with thin-walled circular tubes.

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