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PhD Position in Fracture Mechanics @ University of Leuven

Reza Talemi's picture

Ductile and brittle fracture assessment of pipeline steels using advanced dynamic tensile tear testing methodology

https://www.kuleuven.be/personeel/jobsite/jobs/54616118

University of Leuven

Founded in 1425, the multidisciplinary and research-driven University of Leuven (KU Leuven) has been a centre of learning for almost six centuries. Today, it is Belgium's largest university and is one of the oldest and most renowned universities in Europe. For the third year in a row, KU Leuven tops the Reuters ranking of Europe’s most innovative universities.

Offer

A fully funded PhD position in an international context at the KU Leuven: a top European university and a hub for interdisciplinary research in the fields of characterizing mechanical behaviour of materials. You will be embedded in the Mechanics of Materials, Products and Processes (MeM2P) research group of the Department of Materials Engineering (MTM). You will work in world-class facilities with highly qualified experts,and will benefit from the training scheme developed based on the expertise of academic and industrial partners. This PhD studentship involves regular contact with industry including visits to OCAS research facilities and giving presentations to industrial experts. In addition, you will have opportunities to attend and present your research at major international conferences, as well as publish scientific papers in the relevant journals. The successful candidates will receive a contract as a researcher for two years, starting in October 2018 and renewable up to four years, resulting in a PhD degree in EngineeringTechnology if successful, along with a doctoral training not only on materials science and fracture mechanics but also with the possibility to follow the skills and competence courses from the Arenberg doctoral school. 

Project

Accurate and reliable prediction of fracture propagation in pipelines is of significant interest for safe design of pipelines transporting high-pressure fluids in various industries, including process industry, power generation and etc. Of particular concern are scenarios of pipeline failure when pipeline punctureor rupture happens due to accidental damage to the pipeline material. To properly maintain structural integrity for several decades, avoiding brittle fracture is one of the most important subjects in high toughness pipelines transporting natural gas, CO2 and chemical products. As such, to ensure safe operation of steel pipelines used for different applications, the risk for brittle fracture and its consequences need to be correctly assessed.

In order to qualify for pipeline applications, steels usually need to fulfil requirements from the Drop Weight Tear Test (DWTT), an impact test on a notched three-point bending sample, usually performed on full pipe wall thickness specimens. However, it has been reported in many studies that abnormal fracture, which is also known as inverse fracture, is an issue in the DWTT for high toughness linepipe steels. Moreover, relevance of the DWTT is only valid by the use of correlations issued from extensive campaigns of full-scale burst tests of pipelines. Therefore, a ductile-to-brittle transition behaviour of a pipeline steel is usually evaluated by conducting the pressure vessel fracture test which is also called West Jefferson fracture test.

The West Jefferson fracture test can be considered as a good alternative for full scale burst test. However, the test itself is an expansive destructive experiment and should be performed as a validation step for the DWTT. The main objective of this research project is to develop and introduce a new advanced Dynamic Tensile Tear Test (DT3) apparatus which can be placed between the DWTT and the West Jefferson test to address issues related to the DWTT such as inverse fracture. For this propose, extensive testing campaign will be carried out at different temperatures to validate the proposed set-up against the DWTT. The DT3 equipment was used in the framework of a European FP7 funded research programme and tested at room temperature. However, the set-up needs to be equipped for data acquisitioning and testing at low temperatures (down to-80°C) which will be performed during this research study. Moreover, advanced experimental techniques such as Digital Image Correlation (DIC) and high speed cameras will be used for monitoring fracture mechanics parameters.

Concerning numerical modelling, the purpose of this work is to develop finite element simulations of dynamic ductile and brittle fracture of pipeline steels by means of a coupled damage model. The simulation tool is then used to numerically investigate the effect of testing temperature, plate thickness, plastic anisotropy and through-thickness hardness gradients on the crack growth resistance.

This research project is sponsored by the KU Leuven internal funding scheme (FLOF-beurs). The experimental part of the project will be executed in collaboration with ArcelorMittal Global R&D-Gent, OCAS N.V. The main objectives of present research project can be written as follows:

  • Equipping and developing DT3 machine for performing experiments at low temperatures,
  • Analysing ductile and brittle fracture of pipeline steel using the developed set-up,
  • Analysing fracture surface of broken samples and comparing them with the fracture surfaces of the CVN and the DWTT at different testing temperatures ranging from room temperature to -80°C,
  • Comparing the obtained ductile to brittle transition curves from the DT3 against the CVN and the DWTT,
  • Simulating ductile and brittle dynamic fracture of pipeline steel using coupled damage models,
  • Addressing problems associated with the CVN and the DWTT such as size effect and inverse fracture, respectively,
  • Writing a general guideline for ductile and brittle fracture assessment of pipeline steels using the DT3 machine.for ductile and brittle fracture assessment of pipeline steels using the DT3 machine.

Profile

  • You will have a Master degree in Materials engineering, Mechanical engineering, Civil engineering, Physics or a related subject with good grades (at least distinction in Master degree).
  • You are an enthusiastic and self-motivated person who meets the academic requirements for enrolment for the PhD degree at the KU Leuven.
  • You have an enquiring and rigorous approach to research. A strong interest for multidisciplinary research in mechanical and materials engineering is required.
  • You are interested in fracture mechanics, finite element modelling, mechanical testing and steels.
  • You have good knowledge of working with ABAQUS software and programming languages such as Fortran and Python.
  • Good knowledge of English language, both spoken and written, is essential.
  • Strong commitment, open-minded, ability to work in a team, and eager for international mobility.

Interested?

For more information please contact Prof. dr. ir. Reza Talemi, tel.: +32 9 331 65 01, mail: reza.hojjatitalemi@kuleuven.be.

You can apply for this job no later than June 15, 2018 via the online application tool 

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