IRP8—engineering mechanics

Research topic:	Strength scaling in fibre networks
Recruiting organization:	KTH Royal Institute of Technology, Stockholm, Sweden
Application deadline:	March 11th 2018
Starting time:	June 2018 or as mutually agreed (1-2 months changes to the intended starting time are possible)
Contract duration:	36 months
Benefits	The candidate will be fully employed at KTH on a graduate student position. For such a position the benefits of the Swedish welfare system are available.

 

Scientific content

This research project contributes to the FibreNet objectives by increased knowledge on the impact of the stochastic nature of the fiber materials on their final properties and performance.

In this project, we will study the factors that control the strength distributions in fibre-based products. The importance of strength distribution has been recognized in connection with failures of products made of fibre-based materials. Inability to account for stochastic nature of failures often leads to over-dimensioning paper products. Our goal is to be able to predict strength uniformity parameters from a microscale analysis and discover the factors controlling them. It is vital for predicting performance of the fibre-based materials in end-use applications and saving material through selecting appropriate safety factors.

Both the network strength and strength distribution are size-dependent in fibre-based materials. With increased linear size, the average strength decreases. At the same time, the strength distribution follows the extreme Weibull distribution with a long tail toward zero. It was shown, for example, that the strength distributions of dry pulp fibre networks follow weakest links scaling laws starting from a certain size. This means that once we establish strength statistics at this critical size, we can effectively predict the statistics of a larger sample, which is often applicable to the practical cases giving a possibility to predict the strength of the fibre-based products. We will use the micromechanical computational tools to connect the variability of the constitutive response of paper products with properties of raw materials and important process parameters. This will enable new possibilities for material design not available presently.

Results: The project will develop the methodology from predicting the strength of a large sample from the statistics acquired from the small scale. More specifically, it will:

1. Derive the factors controlling the strength distributions of the fibre-based materials at relevant sizes from which the strength scaling applies.

2. Connect the strength statistics from the micro- and mesoscale to the production or product scale strength statistics.

3. Provide knowledge for developing more reliable predictions regarding the lifetime of the package.

 

The general requirements for all FibreNet positions apply here, i.e.:

• you may already be in a PhD program, but you cannot be a PhD holder,
• you must have less than 4 years of research experience, i.e., you should be an early-stage researcher,
• you must not have resided or carried out your main activity in the country of the hiring organization for more than 12 months during the last 3 years immediately prior to the recruitment (short stays such as holidays and/or compulsory national service are not taken into account), and
• you should have a high-level knowledge of the English language.

 

Furthermore, the position-related requirements are:

• A suitable background for this position would be a Master of Science in Engineering Mechanics, preferably with a Solid Mechanics or a Material Mechanics background.
• In addition to traditional academic merits, a relevant degree project, international experience, and language skills are regarded as advantageous qualifications. Programming skills (Fortran or C) and modelling skills are also of a great advantage for this position.
• Applicants must be strongly motivated for doctoral studies, possess the ability to work independently and perform critical analysis as well as possessing good levels of cooperative and communicative abilities.
• To address its varied work, KTH aims to employ a diversity of talents and, thus, welcomes applicants who will add to the variety of the university, especially as concerns its gender structure.

 

How to apply:

Log into KTH's recruitment system in order to apply for this position: https://www.kth.se/en/om/work-at-kth/lediga-jobb/what:job/jobID:189846/where:4/ ("Login and apply" -button at the bottom of the page). You are the main responsible to ensure that your application is complete according to the advertisement. Your complete application must be received at KTH no later than the last day of application, midnight CET/CEST (Central European Time/Central European Summer Time). The position-specific link will be added here soon.

 

Mandatory appendices:

• a Curriculum Vitae,
• a letter of motivation (maximum of one page),
• the contact details of two referees,
• a copy of B.Sc. and M.Sc. certificates with annexes, and
• a language certificate (IELTS, TOEFL, PTE Academic, Cambridge Language Certificate (Proficiency CPE or Advanced CAE) if available.

 

For more information on:

• the research topic (scientific content), contact the supervisors: Associate Professor Artem Kulachenko or Professor Sören Östlund.
• application procedure, contact: Ms. Eva Lundmark Berg.

 

In case no suitable candidates are found, KTH reserves the right to re-open the call.