Doctoral student in Solid Mechanics with a focus on constitutive modeling of two-phase flows with interacting particles in cellulose-based materials - Hiring in process/Finished, not possible to apply

Description of the workplace

Solid Mechanics was the first division established at LTH and is today a part of the Department of Construction Sciences. The division operates in an international environment and has contact with research organizations and companies both nationally and internationally. Today, the Division of Solid Mechanics consists of approximately 25 employees, of which approximately 15 are doctoral students. The working climate is open and welcoming and strives for every employee to be given the opportunity to develop personally and professionally.

The subject of Solid Mechanics deals with methods and principles to describe deformable bodies. Solid Mechanics is a fundamental subject in mechanical engineering and of fundamental importance for related discipline. The problems and questions that are dealt with in solid mechanics have clear relevance for industrial applications.

The research in the subject is particularly focused on constitutive mechanics, numerical methods, microstructural mechanics, structural optimisation and experimental methods.

Work duties

The main duties of doctoral students are to devote themselves to their research studies which includes participating in research projects and third cycle courses. The work duties will also include teaching and other departmental duties (no more than 20%).

The main goal of the research project is to derive a constitutive model for two-phase flow with physio-chemical interactions in cardboard. The constitutive model will be an extension of two models previously established in the Department of Solid Mechanics at LTH.

The first model, [1], focused on the coupled temperature and moisture response in cardboard but also included simpler couplings to the mechanical response. This model is limited to moisture interactions with water vapor and was used to investigate the response of moist cardboard to rapid heating. 

In the work presented in [2], the model was expanded to include interactions with water in the liquid phase, and hygroexpansion of the fiber network was also added. The new model was used to investigate the response of cardboard during autoclaving, where the cardboard is exposed to high humidity, direct contact with water, high pressure, and high temperature over a relatively long period.

Both of these models were derived within a theoretical framework called mixture theory. In simplified terms, mixture theory involves identifying different components of a material and then considering these components as individual continua that are allowed to interact with each other. Mixture theories are a very powerful framework that enables the handling of multiphysics in a systematic and thermodynamically consistent manner.

The main goal of the advertised doctoral position is to further develop the previous models to include two-phase flow with physio-chemical interactions. Physio-chemical interactions affect how different fluids move through cardboard, and their inclusion is necessary to understand how chemical treatment of cardboard can affect resistance to various liquids. Another important aspect that the model is expected to assist in is understanding how, for example, heat treatment or long-term storage of cardboard affects physio-chemical interactions and, consequently, the response of cardboard.

In addition to the main goal, the research project also includes the following sub-goals:

• Improve and calibrate the capillary pressure model, as presented in [2], for dynamic conditions. The new model should also consider hygroexpansion and differentiate between sorption hysteresis and capillary hysteresis.
• In parallel with the construction of the theoretical model, create numerical sub-models to test and validate the behavior of the theoretical models. 

[1] H. Askfelt, Continuum modeling of the coupled transport of mass, energy, and momentum in paperboard. PhD Thesis, Lund University, 2016

[2] M. Alexandersson, Macroscopic modeling of coupled Multiphysics in swelling cellulose-based materials. PhD Thesis, Lund University, 2020

Admission requirements 

A person meets the general admission requirements for third-cycle courses and study programmes if the applicant: 

• has been awarded a second-cycle qualification, or
• has satisfied the requirements for courses comprising at least 240 credits of which at least 60 credits were awarded in the second cycle, or
• has acquired substantially equivalent knowledge in some other way in Sweden or abroad.

A person meets the specific admission requirements for third cycle studies in research subject if the applicant has: 

• at least 90 credits in the field, including at least 45 second-cycle credits and a second-cycle degree project of 30 credits in the field, or
• a MSc in engineering physics, engineering mathematics, mechanical engineering, or civil engineering.

Additional requirements:

• Good knowledge in solid mechanics and materials sciences
• Good knowledge in mathematics
• Good knowledge in computer programming
• Good knowledge in constitutive modelling 
• Good knowledge in numerical methods, such as the finite element method
• Very good oral and written proficiency in English.

Assessment criteria

Selection for third-cycle studies is based on the student’s potential to profit from such studies. The assessment of potential is made primarily on the basis of academic results from the first and second cycle. Special attention is paid to the following: 

1. Knowledge and skills relevant to the thesis project and the subject of study. 
2. An assessment of ability to work independently and to formulate and tackle research problems. 
3. Written and oral communication skills.
4. Other experience relevant to the third-cycle studies, e.g. professional experience.

Other assessment criteria:

• Knowledge in advanced continuum mechanics, especially mixture theories.
• Good knowledge in computer programing using Fortran, Matlab or Phyton or other languages.

Consideration will also be given to good collaborative skills, drive and independence, and how the applicant, through experience and skills, is deemed to have the abilities necessary for successfully completing the third cycle programme.

We offer

Lund University is a public authority which means that employees get particular benefits, generous annual leave and an advantageous occupational pension scheme. It is advisable to enter information on what your unit specifically can offer as a workplace.
Read more on the University website about being a Lund University employee Work at Lund University. 

Terms of employment 

Only those admitted to third cycle studies may be appointed to a doctoral studentship. Third cycle studies at LTH consist of full-time studies for 4 years. A doctoral studentship is a fixed-term employment of a maximum of 5 years (including 20% departmental duties). Doctoral studentships are regulated in the Higher Education Ordinance (1993:100), chapter 5, 1-7 §§.

How to apply

Applications shall be written in English and include a cover letter stating the reasons why you are interested in the position and in what way the research project corresponds to your interests and educational background. The application must also contain a CV, degree certificate or equivalent, and other documents you wish to be considered (grade transcripts, contact information for your references, letters of recommendation, etc.).

We welcome your application!