Fracture Mechanics

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5 Semi-elliptical crack modeling 3D, SIF, ANSYS
By Amit Bedare · Vellore Institute of Technology

Alaaeldin Elsisi · University of Missouri

I solved problems like this before, it works good. Try to solve half the model before if it works good, it means that you have a problem with the mer... [more]

I solved problems like this before, it works good. Try to solve half the model before if it works good, it means that you have a problem with the merging command.

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5 Can any one help me in the modelling of composite material damage, using damage mechanics techniques?
By Alaaeldin Elsisi · University of Missouri

Alaaeldin Elsisi · University of Missouri

Thank you very much.

Thank you very much.

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New Has anyone worked with the Theta Projection technique (Creep life prediction using short term stress rupture tests)?
I am trying to use the 4 theta projection technique to estimate the remaining life of components subjected to creep. I am having problems using non-l... [more]

I am trying to use the 4 theta projection technique to estimate the remaining life of components subjected to creep. I am having problems using non-linear regression analysis to calculate the individual theta values. I would really appreciate it if anyone can share their experiences and suggestions working with the theta projection technique.

By Sai Vadlamani · University of Illinois at Chicago

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23 Why is plane stress given for thin plates and plain strain conditions given for thick plates?
By Abhinav Varshney · Indian Institute of Technology Kanpur

Venkata Kiran Kumar Ravi

When thin plate/sheet/plane is subjected to loading, stresses induced normal to the plate is negligible as it is non material direction and shear str... [more]

When thin plate/sheet/plane is subjected to loading, stresses induced normal to the plate is negligible as it is non material direction and shear stresses corresponding to normal direction of plate becomes zero.But all normal and shear strains are present.-------------------------Plane stress.

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8 How to find GI and GII values from KI and KII (fracture toughness and critical strain energy release rate relation).
By Jamal Jamali · The University of Western Ontario

Venkata Kiran Kumar Ravi

Use Stress intensity factor while analyzing Linear Elastic materials and J integral for Elasto-plastic analysis i.e non linear Elastic materials. ... [more]

Use Stress intensity factor while analyzing Linear Elastic materials and J integral for Elasto-plastic analysis i.e non linear Elastic materials. While using FEA softwares to overcome singularites near the crack tip, Crack Tip Opening Displacements and forces required to close them are estimated over the virtual crack extension and Strain Energy Release Rate G is calculated . For Linear Elastic isotropic and orthotropic materials & and for the fracture Toughness Predictions at Bi-Material interfaces ENERGY RELEASE RATE(G) is used. For Linear Elastic Materials J-Integral=ENERGY RELEASE RATE(G) For Elasto Plastic Analysis Use J-Integral

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3 Why ceramics have low fracture toughness?
By Siva Reddy · Indian Institute of Science

Pavel Komarov · Russian Academy of Sciences

I agree with S. Sivaprasad that the introducing of fibers and other ductile of fillers can reduce the brittleness of ceramics. Looking for articles on... [more]

I agree with S. Sivaprasad that the introducing of fibers and other ductile of fillers can reduce the brittleness of ceramics. Looking for articles on Ceramic Matrix Composites e.g. DOI:10.1080/10426910802612437 , DOI:10.1016/j.msea.2006.08.102

Following
Question:
Open Why small force to initate and propagate a tearing crack and there is very small deformation of the material as compared to thin ductile polymers?
http://www.youtube.com/watch?v=2iPoBps3ofk

http://www.youtube.com/watch?v=2iPoBps3ofk

By Nasir Mehmood · Blekinge Institute of Technology

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Question:
Open how to do non linear analysis for ROPS?
For a compactor vehicle.

For a compactor vehicle.

http://files.solidworks.com/whitepapers/2010/Nonlinear_Analysis_2010_ENG_FINAL.pdf ×

By Vishnu Pagatur · Don Bosco Technical Institute

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Answer added to:
1 A sodium chloride crystal is brittle when tested in air but becomes ductile when tested under water. Why is this so?
By Ankur Chauhan · Indian Institute of Technology Roorkee

Ivan Jandrlić · University of Zagreb

I'm no expert on this issue, but one explanation may be because in the crystals of sodium chloride, when placed in water, crystal embedd H2O in crysta... [more]

I'm no expert on this issue, but one explanation may be because in the crystals of sodium chloride, when placed in water, crystal embedd H2O in crystal structure. Something like the clay when it becomes ductile when wet, it is known that salt is hydroscopic.

Following
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Open Parallelisation of continuum model based fracture simulations
I would like to pose a question that is relatively open. Computational simulation of fracture (crack initiation, crack growth and crack propagation in... [more]

I would like to pose a question that is relatively open. Computational simulation of fracture (crack initiation, crack growth and crack propagation including bifurcation and branching) is a very popular field in applied mechanics research. The complexities of the mechanics involved have prompted numerous approaches to modelling fracture such as eXtended FEM, Cohesive Zone Modelling etc., which have been applied to parallel simulations rather successfully. For my part, I have been working on Continuum Mechanics based models, such as gradient modelling, phase field modelling, micromorphic modelling etc. The biggest advantage of using this type of approach is the possibility to develop a unified model that can simulate different mechanical processes as a material model (elasticity, plasticity, damage, heat transfer etc.), at various scales of the materials (nano-, micro-, meso- and macro-scale). Via my PhD work I am convinced that this approach to modelling is fairly robust in terms of handling coupled phenomena. Furthermore, it allows for a relatively easy implementation using standard FEM, with or without slightly modified elements (depending on the case). The problem with these approaches lies in the parallelisation of the simulations. I am wondering if anyone in the RG community has had any experience, or has had any problems in attempting such parallelisation or has developed any algorithm to address this issue. If anyone has succeeded in parallel simulations, could you kindly indicate the numerical details of your simulations (if possible of course). For example, how many nodes, improvement in time observed, type of integration schemes used, elements used, global resolution algorithms used, time stepping techniques, error detection/correction, type of material tested etc. Looking forward to replies. To be clear, by "parallelisation" I mean computing spread over different nodes on a cluster, which is not the same as "multi-threading", which is relatively straight forward to implement and is a completely different approach.

By Prajwal Sabnis · École Nationale Supérieure des Mines de Paris

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5 Why did hardness of aluminium alloy AA6061-T6 increase after fatigue test at elevated temperature?
By Kamarul Ariffin Zakaria · Technical University of Malaysia Malacca

Patrick N.B. Anongba · University "Félix Houphouët-Boigny"

You may prepare TEM thin foils from the fractured surfaces at different temperatures and look for changes in substructure ( defects such as dislocatio... [more]

You may prepare TEM thin foils from the fractured surfaces at different temperatures and look for changes in substructure ( defects such as dislocations could increase the hardness if the density increases)

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6 What is the J integral?
By Prakash Shinde ·

S. Sivaprasad · National Metallurgical Laboratory

You know the toughness of a material is measured by its resistance to crack initiation (and /or crack propogation), known as fracture toughness. In b... [more]

You know the toughness of a material is measured by its resistance to crack initiation (and /or crack propogation), known as fracture toughness. In brittle materials (here the term brittle is in relative sence, for eg., glass is brittle when compared to cast steel; cast steel is brittle when compared to stainless steel and so forth). In case of brittle materials, as soon as a crack initiates, it will zip through the material, meaning it requires less enegry for its initiation and/or propogation. These materials are characterised by linear elastic fracture mechanics employing theory of elasticity. On contrary, for sufficiently ductile materials, since the material can absorbe lot of energy prior to crack initiation and its growth, such a simple approach based on elstic theory cannot be employed. An alternatve approach is use of plasticity theory to measure the energy requied for crack initiation and propogation.. J integrtal is a volume integral formulation used for such calculation. For further reading on J integral refer the fracture mechanics book by T L Anderson.

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2 Crack zone

Luis H Hernandez · National Polytechnic Institute

I HAD A QUICK GLANCE TO THE ENCLOSED PAPER. An energetic approach has been followed. You have to keep in mind that a cracked body can be loaded by dif... [more]

I HAD A QUICK GLANCE TO THE ENCLOSED PAPER. An energetic approach has been followed. You have to keep in mind that a cracked body can be loaded by different conditions (tension, bendinding, etc,) However, the mode I is developed by the maximum principal stress at the crack tip. So, as far as I understand, the key point is to find a relation between the external load and the SIF. You cab easily find with the Castigliano Theorem.

Following
Question:
Open The mechanics of self-similar and self-affine fractal crack.pdf
The mechanics of self-similar and self-affine fractal crack.pdf

The mechanics of self-similar and self-affine fractal crack.pdf

The mechanics of self-similar and self-affine fractal crack.pdf ×

By Bojing Zhu

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About Fracture Mechanics

Fracture mechanics is the study of the influence of loading, crack size, and structural geometry on the fracture resistance of materials containing natural flaws and cracks. When applied to design, the objective of the fracture mechanics analysis is to limit the operating stress level so that a preexisting crack would not grow to a critical size during the service life of the structure.

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Thomas Guénet

University Laval
Marcelino Pereira do Nascimento

Universidade Estadual Paulista
Luis Kosteski

Universidade Federal do Pampa (Unipampa)
Alberto Corigliano

Politecnico di Milano
Hardayal Mehta

General Electric Company
Michael Plecko

University of Zurich
Luca Andena

Politecnico di Milano
R. K. Sabat

Indian Institute of Science
Baoxing Xu

Columbia University
Alexander Ovchinnikov

Southern Ural State University

Fracture Mechanics

About Fracture Mechanics

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