Dear Colleagues We are looking for a post-doctoral level researcher for a 18 month project in collaboration with a startup company EMTD lab and the European Space Agency. The work to be done is related to radiation shielding and fatigue fracture. We are looking for people with a background in polycrystalline fracture, phase field/enriched finite element methods and multi-scale methods. Knowledge of metallurgy and crystallography would be welcome. Due to confidentiality, we cannot divulge more information at this stage. The position is based at the University of Luxembourg Interdisciplinary Centre for Security and Trust. Please contact me if you have interested candidates. Best wishes from Luxembourg, Stéphane Bordas, FLSWProf. in Computational MechanicsHead, Data and Computational Sciences www.legato-team.eustephane . bordas @ gmail . com

The Department of Materials Science and Engineering of the Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg is inviting applications for three doctoral research positions to begin immediately. The successful applicants will work together with Prof. Erik Bitzek on studying the atomistic origins of materials failure in the context of (1) semi-brittle fracture in the ERC-funded Project microKIc: Microscopic Origins of Fracture Toughness; (2) nanomechanics and small-scale plasticity within the research training group GRK 1896 “In Situ Microscopy with Electrons, X-rays and Scanning Probes”; (3) properties of defects in complex intermetallic phases within the Collaborative Research Center SFB 1394 “Structural and Chemical Atomic Complexity: From Defect Phase Diagrams to Material Properties”.

Applicants should have a master’s degree with good to excellent marks in Physics, Material Science, Mechanical Engineering, Chemistry, or a related field. Experience in performing numerical simulations, preferably using Molecular Dynamics, and in scientific programming are advantageous. In addition, a solid background in mechanical behavior of materials, physical metallurgy and thermodynamics is highly desirable. Excellent oral and written communication skills and the ability to work well in a dynamic and collaborative research environment are essential.

The position is full-time, and payment follows the German TV-L 13 scale. The starting date is as soon as possible. The FAU Erlangen-Nürnberg intends to increase the number of women in research and teaching positions and, therefore, strongly encourages female researchers to apply. Disabled applicants will be preferentially considered in case of equivalent qualification.

Please send your application (including a cover letter describing your research interests, curriculum vitae, transcript of records as well as contact information of two references) to comp-mat-sci-jobs@ww.uni-erlangen.de.

About FAU: The FAU is Germany 10th largest university and has been ranked Germany’s most innovative university in the 2019 Reuters Innovation Ranking. It is located in the metropolitan area of Nuremberg (3.5 Mio inhabitants), in the northern part of Bavaria. The FAU is home to Germany’s largest and oldest Materials Science and Engineering Department, which is consistently ranked amongst the top 2 according to the German Science Foundation (DFG).

This is the second announcement about the upcoming Workshop on Computational Fatigue Analysis 2017, this year dedicated to Design and Fatigue of Weldments (WCFA2017-DFW - http://www.pragtic.com/DFW.php). The workshop is held in Prague, Czech Republic in November 13-16, 2017. The key lecturer, who guides the audience through various issues of the fatigue analysis in welds, is Dr Zuheir Barsoum from KTH - Royal Institute of Technology in Sweden. A separate day will be spent on introducing or reviving the topic of general computational fatigue analysis. This day will be lectured by Prof Milan Růžička, Jan Papuga PhD and Josef Jurenka PhD.

More about the workshop can be found in the leaflet available on http://www.pragtic.com/dfw/WCFA17_DFW_Invitation_v2.pdf

Let us remind you that there are various variants depending on the experience or interests of the participants. A 10% price reduction is valid for all registered members of the Czech Society for Mechanics. And above all, there is a special reduced Early Bird rate valid for all registrations and payments finished up to September 22, 2017.

Thank you for sharing this information with other people who might be interested in it.

Best regards

Jan Papuga

WCFA2017-DFW chairman

Sandra Korte-Kertzel, Peter Gumbsch and I are organizing a Symposium on the Fundamentals of Fracture

at the joint meeting of the German and European Physical Societies (DPG and EPS) in Berlin, March 11-13 2018.

This symposium is intended as an international forum for the presentation and discussion of the latest scientific developments regarding the physics and mechanics of fracture. Rather than addressing specific engineering problems and approaches, this symposium will cover fracture of brittle and semi-brittle materials at a fundamental level, with a focus on crack nucleation and crack-microstructure interactions. We aim at bringing together specialists from the fields of solid state physics, materials science, continuum mechanics, statistical physics and mathematics to cover theory, multi-scale modeling and experiments related to

• Initiation of fracture and crack nucleation
• Grain boundary fracture and interface cracks
• Crack – obstacle interactions
• Interplay of fracture and plasticity
• Fracture of nanostructures and disordered materials
• Fracture of composites
• Statistical aspects of fracture
• Micromechanical and local approaches to fracture

A special joint session on advanced micro- and nanomechanical fracture testing methods is envisaged with the planed EPS mini-colloquium “Mechanical properties at small scales” organized by Gerhard Dehm, Olivier Thomas and Laurent Pizzagalli.

For more information see

http://www.eam.fau.de/fundfracture/

Because of the increasing need of energy, the plants installed by electricity supply utilities throughout the world are becoming larger and more highly stressed. Thus, the risk of turbogenerator shaft cracking is increasing also. The development and propagation of a crack represents the most common and trivial beginning of integrity losses in engineering structures. For rotating shafts, a propagating fatigue crack can have detrimental effects on the reliability of a process or utility plant where theses vital parts are subjected to very arduous working conditions in harsh environment. It is one of the most serious causes of accidents and, an early warning is essential to extend the durability and increase the reliability of these machines. The vibration analysis and modeling of the shaft and cracks are necessary for a reliable identification of the crack location and depth to avoid catastrophic failures. In fact, cracks can develop and propagate to relevant depths without affecting consistently the normal operating conditions of the shaft. Another feature related to the problem of modeling cracked rotating shafts is the consideration of the opening−closing phenomenon of the crack during the shaft rotation.

An elegant, simple and comprehensive model has been suggested for the nonlinear dynamics and stability analysis of a cracked rotating shaft. It is known that the gap between the lips of a fatigue-induced crack are very small and that closure of the crack occurs when the shaft rotates. Accordingly, the breathing mechanism of the crack is taken into account by considering a more realistic function describing the periodic variation of the global stiffness of the shaft. In particular, a partial opening−closing of the crack in both directions is allowed since a switching crack model is not adequate to examine the stability of shafts with deep cracks. Moreover, the breathing mechanism is depending not only but substantially on the shaft dynamics response and, thus, the obtained equilibrium equations are nonlinear. Additional work is required for deeper exploration of this complex mechanical system and to establish quantitative results and diagrams that could be useful for engineers in power stations industry.

This program is open to highly qualified Chinese students interested in carrying on doctoral training at ParisTech with financial support of the CSC.

http://paristech-china.com/sites/default/files/program-list/Arts%20et%20...

http://orbilu.uni.lu/handle/10993/25835 Link to PDF: http://orbilu.uni.lu/bitstream/10993/25835/1/report.pdf

Isogeometric boundary element methods for linear elastic fracture mechanics

http://smai.emath.fr/canum2016/

[Link]

Congratulations, Xuan! It was a pleasure to work with you. Thank you to Pierre Kerfriden and Elena Atroshchenko for their wonderfully effective co-supervision.

We thank the funding from the ITN INSIST from FP7 (FP7 ; 289361 - INSIST - Integrating Numerical Simulation and Geometric Design Technology) www.itn-insist.com/

-- Stéphane Bordas

The project is between BITS Pilani (India) and Wuhan University (China), funded by the Ministry of Mines, Govt. of India. It is in the area of computational fracture mechanics.

Details of the project and application process is in the attachment.

A Postdoctoral fellowship is available at The Johns Hopkins University, Baltimore, U.S.A. in the area of fracture and fragmentation under dynamic loading conditions. The potential candidate should have a Ph.D. in an engineering discipline, a strong background in fracture mechanics and extensive computational modeling experience working with the finite element methods or some other numerical method with application to solid mechanics.

If you are interested, please send an email to Dr. Nitin Daphalapurkar at nitin@jhu.edu with your curriculum vitae and the names of at least two references. Please use the subject line "Postdoc Application: Modeling dynamic fragmentation." The Johns Hopkins University practices Equal Employment Opportunity and Affirmative Action.

Nitin Daphalapurkar, Ph.D.

Assistant Research Professor

Hopkins Extreme Materials Institute

Department of Mechanical Engineering

The Johns Hopkins University

3400 N Charles St, Baltimore, MD 21218, U.S.A.

Self-positioned nanomembranes such as rolled-up tubes and wrinkled thin films have been potential systems for a variety of applications and basic studies on elastic properties of nanometer-thick systems. Although there is a clear driving force towards elastic energy minimization in each system, the exploration of intermediate states where specific characteristics could be chosen by a slight modification of a processing parameter had not been experimentally realized. In this work, arrays of freestanding III-V nanomembranes (NM) supported on one edge and presenting a coexistence of these two main behaviors were obtained by design of strain conditions in the NMs and controlled selective etching of patterned substrates. As the etching process continues a mixture of wrinkled and rolled-up states is achieved. For very long etching times an onset of plastic cracks was observed in the points with localized stress. The well-defined morphological periodicity of the relaxed NMs was compared with finite element simulations of their elastic relaxation. The evolution of strain in the NMs with etching time was directly evaluated by X-ray diffraction, providing a comprehensive scenario of transitions among competing and coexisting strain states.

http://pubs.rsc.org/en/Content/ArticleLanding/2014/NR/C4NR03986F#!divAbs...

Related previous articles:

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.79.085429

http://link.aip.org/link/?APL/89/043119/1

http://link.aps.org/abstract/PRL/v90/e074302

In phase field method how one can specify the crack in fixed grid?

In case of finite element method one uses two overlapping nodes to model crack, which nodes separate after crack propagation. In case of phase-field, generally people use fixed grid finite difference method. My question is how the same node point can show two different displacements when crack has passed through it like FEM?

Hello

I am using Abaqus/CAE 6.10 to simulate a Debonding test (cohesive behavior for composite delamination).

I ran a Abaqus debonding simulation example (from Abaqus online documentation - Abaqus Benchmark Manual - 2.7.1 Delamination analysis of laminated composites).

The Abaqus/Explicit three-dimensional model with surface-based traction-separation behavior used a surface contact interaction property with:

- default Cohesive behavior

- XFEM-based LEFM (using VCCT) fracture criterion.

The following ERROR message appeared after submiting the job:

"The direction parameter is not available for *fracture criterion with surface-based cohesive behavior."

I tried to run the model without the XFEM fracture criterion and it went allright.

Do anyone knows why can't I apply this fracture criterion in this DCB test?

Thank you for your time and attention.

Best regards,

David Melo - PORTUGAL

This paper could be Downloaded at: http://sam.ensam.eu/handle/10985/7489

In this paper, the effects of a breathing crack on the vibratory characteris-

tics of a rotating shaft are investigated. A new, simple and robust model composed of

two rigid bars connected with a nonlinear flexural spring is proposed. The nonlinear

spring, located at the cracked transverse section position, concentrates the global stiff-

ness of the cracked shaft. The breathing mechanism of the crack is described by a more

realistic periodic variation of the global stiffness depending not only but substantially

on the system vibratory response. It is based on an energy formulation of the problem

of 3D elasticity with unilateral contact conditions on the crack lips. A possible partial

opening and closing of the crack is considered which makes the approach more appro-

priate for deep cracks modeling. The harmonic balance method, direct time-integration

schemes and nonlinear dynamics tools are used to characterize the global dynamics of

the system. The effects of the crack depth and rotating frequency have been metic-

ulously examined and it was found that the cracked shaft never exhibits chaotic or

quasi-periodic vibratory response.

This paper could be Downloaded at: http://sam.ensam.eu/handle/10985/7489

Macroscopic
cracks do not appear as a result of an ideal separation of two adjacent atomic
layers. Just the opposite, cracks appear as a result of the development of
multiple micro-cracks triggered by the massive breakage of atomic bonds. The microcracking
and the bond breakage are not confined to two neighbor atomic planes: the
process involves thousands atomic planes within the representative characteristic
volume of size h. This size defines the width (not the lenth) of the damage
localization zone and it can be called the crack thickness. The knowledge of
the crack thickness is especially important for modeling crack propagation. In
the attached three notes I calculate the crack thickness for natural rubber: h
~0.2 mm; DH36 steel: h ~10 μm; and plain concrete: h ~2 cm.

doi:10.1088/0964-1726/22/6/065001 (FEATURED ARTICLE of IOP)

The nonlinear electromechanical behavior of a cracked ferroelectric single crystal subjected to pure electrical loading is investigated by a three-dimensional phase field model for different crack face electrical boundary conditions. Phase field simulations show that crack face electrical boundary conditions have significant influence on the electrical and mechanical responses of the ferroelectric single crystal to an external electric field. The coercive field for the polarization switching of a single crystal with an electrically permeable crack is about 50% larger than that for a single crystal with an electrically impermeable crack. The remanent strain and the strain variation induced by polarization switching in a single crystal with a permeable crack are larger than those with an impermeable crack. The different macroscopic nonlinear behaviors are attributed to different polarization switching processes. It is found that domain switching takes place from the surface of a single crystal with a permeable crack, while it begins from the vicinity of the crack tip when the crack is impermeable. A ferroelectric single crystal with an impermeable crack exhibits strip 90° domain switching under a negative electric field, which is consistent with experimental observation.

I've modelled a DCB specimen and applied Boundary conditions and load... I followed the same procedures given in abaqus documentation... As expected the crack initiates and propagates along the interface... I can get the Resultant force vs displacement plot from the analysis.. But i dont know how to plot the fracture toughness vs crack length plot in ABAQUS..

Please help me... Your suggestion would really help me a lot..

Dear Colleague

I am modelling a 2D three point bending to analysis the crack propagation , i have a question in the part of damage evaluation, does anybody know what is different between, B.K , power law and mod.independent? means when we select one of them. Thanks

The position concerns contribution to the development of Morfeo, a manufacturing oriented finite element software. For any of the project activities, the candidate is expected to develop the numerical methodology up to industrial maturity. First of all, the candidate will contribute to the fracture analysis module of Morfeo. Morfeo relies on an innovative approach based on the extended finite element method (X-FEM) in order to easily handle complex industrial applications. Developments include general modeling of the crack propagation and the damage tolerant approach, contact, multi-crack analysis and parallel implementation of the algorithms. Targeted applications include e.g. determination of crack propagation paths on industrial large-scale components and fatigue analysis.

Cenaero (http://www.cenaero.be) is an applied research center focused on the development of advanced simulation technologies for aeronautics. Located within the Aerop^ole de Gosselies in Belgium, it employs about 50 highly skilled researchers working on virtual manufacturing, multi-scale material modeling, CFD-based multi-physics and optimization. To further grow its fracture mechanics research activity, Cenaero invites applications for a research engineer position at Cenaero headquarters in Belgium, available immediately.

As member of the Morfeo development team, the candidate will also have to tackle more general developments within the nite element software, write portable code, stick to development rules already in place and write relevant test cases.

For additional informations, please see attached offer and senda cover letter and a resume viae-mail to rh@cenaero.be with mention to the reference number MORFEO-2012-002

I'm modeling rock fracture problem with cohesive element. I konw the propertiey of the solid element around the fracture because we can measure it (rock sample) in the lab. but as regard to how to define the propeties of cohesive element, I'm completely lost.

in fact, the cohseive element is a fictitious one, not a real matearial in the physical world, we can't mearsure its propety by physical means. then how can we know what parameters we should enter ?

need your help, thanks

Large EPSILON 3D

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how to do a crack propagation analysis?

can abaqus be used for doing crack propagation analysis for plates with multiple cracks?

Nano Lett., DOI: 10.1021/nl201376j

The lithiation reaction of single ZnO nanowire (NW) electrode in a Li-ion nanobattery configuration was observed by in-situ transmission electron microscopy. Upon first charge, the singlecrystalline NW was transformed into a nanoglass with multiple glassy nanodomains (H. Gleiter, MRS Bulletin 34 (2009) 456), by an intriguing reaction mechanism. First, partial lithiation of crystalline NW induced multiple nanocracks ~70 nm ahead of the main lithiation front, which traversed the NW crosssection and divided the NW into multiple segments. This was followed by rapid surface diffusion of Li+ and solid-state amorphization along the open crack surfaces. Finally the crack surfaces merged, leaving behind a glass-glass interface (GGI). Such reaction front instability also repeated in the interior of each divided segment, further subdividing the NW into different nanoglass domains (nano-amorphization). Instead of the profuse dislocation plasticity seen in SnO2 NWs (Science 330 (2010) 1515), no dislocation was seen and the aforementioned nanocracking was the main precursor to the electrochemically-driven solid-state amorphization in ZnO. Ab initio tensile decohesion calculations verified dramatic lithium embrittlement effect in ZnO, but not in SnO2. This is attributed to the aliovalency of Sn cation (Sn(IV), Sn(II)) in contrast to the electronically more rigid Zn(II) cation.