A Model for a Propagating Shear Band on the Basis of a Tilt Wall Dislocation Array

1992 ◽  
Vol 45 (3S) ◽  
pp. S71-S74 ◽  
Author(s):  
J. P. Hirth
Keyword(s):  
Shear Band ◽  
Mixed Mode ◽  
Mode I ◽  
Pure Mode ◽  
Rotor Steel ◽  
Mode Iii ◽  
Microstructural Parameters ◽  
Plane Strain Tension ◽  
First Case ◽  
Propagating Shear

Microstructural parameters influencing shear band propagation and, ultimately, fracture in steels are reviewed for two types of test. These are the plane strain tension characteristics of spheroidized steels and the mixed mode I/III J-resistance behavior of a rotor steel. In the former case, shear band propagation is associated with voids forming at carbide particles because of incompatibility effects. In the latter case, the mixed mode I/III toughness is less than that in either pure mode I or pure mode III because local plastic flow in the path of the crack produces damage in the form of voids by a process analogous to the first case. A model for the interaction of a shear band and particles, suggested by these results, is proposed in the form of a discontinuous tilt wall of dislocations that breaks away and propagates past the particles. The model is shown to be consistent with several experimental observations, both of shear band characteristics and of the stress required to propagate the band.

Fracture Study on Mode I-III Crack of Rock

2006 ◽  
Vol 324-325 ◽  
pp. 1217-1220 ◽  
Author(s):  
Li Yun Li ◽  
Feng Guang Xu ◽  
He Ping Xie ◽  
Wei Ning
Keyword(s):  
Mixed Mode ◽  
Loading Condition ◽  
Fracture Propagation ◽  
Mode I ◽  
Pure Mode ◽  
Mode Iii ◽  
Element Analysis ◽  
Out Of Plane ◽  
Engineering Designs ◽  
Fracture Study

This paper illustrates some preliminary experimental, numerical and theoretical analysis results of mixed mode I-III rock cracks under apparent mode III loading. Some edge notched granite specimens are tested under out-of-plane four-points shearing loading condition, i.e., an apparent mode III loading condition. A series finite element analysis was conducted to understand the mechanism of the crack fracture propagation under this loading condition. The stress intensity factor distributions along the 3-D crack tips are also obtained. All crack fracture propagation surfaces of the specimens are similar helicoids which radius can be mainly influenced by the loading patterns, i.e., the action width s. The crack fracture initiates at the midpoint of the crack front. From the numerical calculation and experimental investigation, it has been revealed that all of these crack fracture initiations are caused by maxima tensile stress σ1. Based on this stress σ1, a new fracture criterion of mixed mode I-III is proposed. Its predictions agree well with the experiment results. This criterion can be applied to practice engineering designs which are related with mixed mode I-III or pure mode III rock crack fracture problems.

Mixed-Mode I/III Fracture Characterization of Aluminum Alloy

2013 ◽  
Vol 853 ◽  
pp. 187-191
Author(s):  
R. Ravichandaran ◽  
G. Thanigaiyarasu
Keyword(s):  
Fracture Toughness ◽  
Aluminum Alloy ◽  
Mixed Mode ◽  
Mode I ◽  
Pure Mode ◽  
Mode Iii ◽  
Fracture Characterization ◽  
Inclination Angles ◽  
Point Bend ◽  
Work Done

Aluminum alloy 5083 is taken for the study of fracture parameters in mixed-mode I/III. Three point bend specimens with load inclination and notch inclination are fabricated and precracked. They are tested with various inclination angles and for two different thicknesses. The results are analyzed and found that the fracture toughness decreases for larger inclination angles. Also, it is found that the thinner specimens are found to be tougher than the thicker specimens. Material and methods Symmetrical three-point bend cracked specimens have been used extensively in fracture mechanics to study mode I fracture properties because they are one of the standard types of specimens used in the ASTM codes for determining the fracture toughness JIc..In the mixed-mode I/III fracture, there is only a limited amount of experimental work done so far. The observations on combined mode I - mode III fracture have been very scarce and there is no general agreement among researchers on the effect of the addition of a mode III component to pure mode I loading. Limited study (Avci et al 2005 [, Kamat and Hirth 1996 [) has been done on bend specimens subjected to mixed-mode I/III when compared to the mode I case, i.e., a center-loaded specimen.

Experimental Study on Out-Plane Crack Extension in Rimmed Steel

2013 ◽  
Vol 690-693 ◽  
pp. 1767-1770
Author(s):  
Bang Cheng Yang ◽  
Jian Xiong Liu ◽  
Rong Xin Guo ◽  
Hai Ting Xia
Keyword(s):  
Mixed Mode ◽  
Crack Extension ◽  
Thin Sheet ◽  
Mode I ◽  
Pure Mode ◽  
Sheet Metals ◽  
Mode Iii ◽  
Steel Sheets ◽  
Fracture Tests ◽  
Plane Mode

Study on the fractural mechanism of thin sheet metals focuses on how to efficiently fracture and recycle the scrapped vehicles and electrical equipments. By using the experimental fracture mechanics, the failure mode was studied for 10F rimmed steel sheets to be crushed and recycled. In-plane mode I, out-plane mixed mode I /III and mode III fracture tests were conducted under different loading angles. The effects and contributions of mixed mode crack extensions for 10F rimmed steel sheets were analyzed and some sensitive fractural factors were studied. The experimental results show that pure mode III is most viable to fracture the thin sheet 10F rimmed steels.

scholarly journals Mixed-Mode Interlaminar Fracture Toughness of Glass and Carbon Fibre Powder Epoxy Composites—For Design of Wind and Tidal Turbine Blades

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2103
Author(s):  
Christophe Floreani ◽  
Colin Robert ◽  
Parvez Alam ◽  
Peter Davies ◽  
Conchúr M. Ó. Brádaigh
Keyword(s):  
Fracture Toughness ◽  
Carbon Fibre ◽  
Composite Structures ◽  
Mixed Mode ◽  
Epoxy Composites ◽  
Mode I ◽  
Mode Ii ◽  
Pure Mode ◽  
Interlaminar Fracture Toughness ◽  
Interlaminar Fracture

Powder epoxy composites have several advantages for the processing of large composite structures, including low exotherm, viscosity and material cost, as well as the ability to carry out separate melting and curing operations. This work studies the mode I and mixed-mode toughness, as well as the in-plane mechanical properties of unidirectional stitched glass and carbon fibre reinforced powder epoxy composites. The interlaminar fracture toughness is studied in pure mode I by performing Double Cantilever Beam tests and at 25% mode II, 50% mode II and 75% mode II by performing Mixed Mode Bending testing according to the ASTM D5528-13 test standard. The tensile and compressive properties are comparable to that of standard epoxy composites but both the mode I and mixed-mode toughness are shown to be significantly higher than that of other epoxy composites, even when comparing to toughened epoxies. The mixed-mode critical strain energy release rate as a function of the delamination mode ratio is also provided. This paper highlights the potential for powder epoxy composites in the manufacturing of structures where there is a risk of delamination.

Pre-Strain Effects on Mixed-Mode Fatigue Crack Propagation Behaviour of the P355NL1 Pressure Vessels Steel

2018 ◽  
Author(s):  
João Ferreira ◽  
José A. F. O. Correia ◽  
Grzegorz Lesiuk ◽  
Sergio Blasón González ◽  
Maria Cristina R. Gonzalez ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Mixed Mode ◽  
Pressure Vessels ◽  
Mode I ◽  
Pure Mode

Pressure vessels and piping are commonly subjected to plastic deformation during manufacturing or installation. This pre-deformation history, usually called pre-strain, may have a significant influence on the resistance against fatigue crack growth of the material. Several studies have been performed to investigate the pre-strain effects on the pure mode I fatigue crack propagation, but less on mixed-mode (I+II) fatigue crack propagation conditions. The present study aims at investigating the effect of tensile plastic pre-strain on fatigue crack growth behavior (da/dN vs. ΔK) of the P355NL1 pressure vessel steel. For that purpose, fatigue crack propagation tests were conducted on specimens with two distinct degrees of pre-strain: 0% and 6%, under mixed mode (I+II) conditions using CTS specimens. Moreover, for comparison purposes, CT specimens were tested under pure mode I conditions for pre-strains of 0% and 3%. Contrary to the majority of previous studies, that applied plastic deformation directly on the machined specimen, in this work the pre-straining operation was carried out prior to the machining of the specimens with the objective to minimize residual stress effects and distortions. Results revealed that, for the P355NL1 steel, the tensile pre-strain increased fatigue crack initiation angle and reduced fatigue crack growth rates in the Paris region for mixed mode conditions. The pre-straining procedure had a clear impact on the Paris law constants, increasing the coefficient and decreasing the exponent. In the low ΔK region, results indicate that pre-strain causes a decrease in ΔKth.

scholarly journals A three-dimensional elastoplastic analysis of mixed-mode KI/KII around the crack front

2019 ◽  
Vol 300 ◽  
pp. 11002
Author(s):  
Luiz Fernando Nazaré Marques ◽  
Jaime Tupiassú Pinho de Castro ◽  
Luiz Fernando Martha ◽  
Marco Antonio Meggiolaro
Keyword(s):  
Crack Front ◽  
Mixed Mode ◽  
Three Dimensional ◽  
Local Stress ◽  
Mode I ◽  
Pure Mode ◽  
Mode Effects ◽  
Fatigue And Fracture ◽  
Edge Tension ◽  
Combined Mode

Engineering problems that involve fatigue crack growth and fracture frequently can be studied by taking into account only mode-I features. However, many important problems that involve combined mode I and II loadings cannot be properly analyzed by a pure mode-I approach, which in particular may not be sufficient to estimate fracture toughness for practical purposes in such cases. Such mixed-mode problems involve crack orientation and/or load conditions that lead to combined local Stress Intensity Factors (SIFs) KI/KII around the crack front. Using multiaxial crack tip condition characterized by the crack inclination angle βin a mixed-mode KI/KII modified single edge tension SE(T) specimen, such mixed-mode effects on plastic zone shapes, volumes and plastic work UPL are taken into account to evaluate problems that involve fatigue and fracture.

The Contribution of Different Fracture Modes on Drilling Delamination Crack Propagation

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Mohammad Reza Vaziri Sereshk ◽  
Hamed Mohammadi Bidhendi
Keyword(s):  
Crack Propagation ◽  
Crack Nucleation ◽  
Dominant Mode ◽  
Mode I ◽  
Minor Effect ◽  
Pure Mode ◽  
Mode Iii ◽  
Major Mode ◽  
Drill Point ◽  
Drilling Conditions

Delamination as the main defect created during drilling of composite laminate is principally a crack nucleation and propagation phenomenon. The fracture-based investigation is performed to identify the significance of different modes involving in this process. The sensitivity analysis is implemented to evaluate magnitude and importance of each mode. As a result, mode I is a dominant mode while drill point removes the material; however, the crack continues to propagate under pure mode III for a while after drilling due to contact of flutes with spalls. This paper investigates the crack formation process for wide variety of drilling conditions and tool geometries. It is demonstrated that although mode III contributes, its minor effect might be neglected if comparing with fracture mode I. Therefore, it may be vanished as a tool design strategy. It is indicated that chisel edge plays a great role in crack propagation under major mode I; therefore, any further design approach which limits or eliminates opening action of chisel edge decreases delamination significantly. Material removal starting from hole perimeter as well as implementing small predrilled holes (such as action of primary cutting lips in step drill) are examined as solutions based on this approach.

Asymptotic Crack-Tip Fields in Perfectly Plastic Solids Under Mixed Mode II/III Loading Conditions

2006 ◽  
Vol 129 (4) ◽  
pp. 664-669
Author(s):  
J. Pan ◽  
P.-C. Lin
Keyword(s):  
Mixed Mode ◽  
Crack Tip ◽  
Shear Loading ◽  
Mode Ii ◽  
Pure Mode ◽  
Loading Conditions ◽  
Mode Iii ◽  
Plane Shear ◽  
Crack Tip Fields ◽  
Perfectly Plastic

In this paper, governing equations and solutions for asymptotic singular and nonsingular crack-tip sectors in perfectly plastic materials are first summarized under combined in-plane and out-of-plane shear loading conditions. The crack-tip fields under mixed mode II/III loading conditions are then investigated. An assembly of crack-tip sectors is adopted with stress discontinuities along the border of the two constant stress sectors. The solutions of the crack-tip fields under pure mode II, mixed mode II/III, and nearly pure mode III loading conditions are presented. The trends of the angular variations of the mixed mode II/III crack-tip stresses agree with those of the available computational analysis and the asymptotic analysis for low strain hardening materials. The pure mode II crack-tip stresses are similar to those of Hutchinson, and the nearly pure mode III stresses are similar to those of the pure mode III crack-tip field of Rice.

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