Internship | Redistribution of residual stresses in small specimen

Fatigue is one of the decisive factors for maintenance of steel structures. Accurately describing the fatigue crack growth rate is crucial in determining the fatigue life. The fatigue crack growth rate is influenced by the residual stresses. Several techniques are available for the measurement of residual stresses such as the hole drilling method, X-ray diffraction, neutron diffraction and the crack compliance method. However often when preparing specimen for these measurements the structure needs to be cut in smaller pieces. Due to the self-balancing nature the residual stresses in a sample will redistribute. This leads to large uncertainty and the question when measuring the measured residual stresses on a small specimen does this still represent the real residual stresses in the whole structure. The focus of this project is on rails. Residual stresses in rails arise from manufacturing as well and redistribution during operation. An accurate description of the residual stress field throughout the whole cross section of the rail is therefore important.

This graduation projects aims to identify the influence of the specimen size on the residual stress distribution, develop a method to predict the residual stress distribution in the full rail based on a small specimen residual stress measurements and if required propose an experimental method to overcome this problem. To reach this goal, the use of (advanced) numerical models, as for instance the finite element method (FEM), are foreseen, complemented with a validation measurement

The intended steps:

• Literature review
  • State-of-the-art residual stress measurement techniques
  • Residual stress fields in rails, for both as manufactured and used rail
  • Finite Element (FE) modelling of residual stresses
• Numerical modelling
  • Modelling of a residual stress field in a rail
  • Development of a framework to mimic the cutting of small specimen
  • Develop a method to calculate the residual stress distribution in a full rail based on small specimen experimental results.
• Experimental research
  • Residual stress measurements on a rail to validate FE model, using for example hole drilling
  • Proposal for residual stress measurements on full rails. These experiments are not necessarily done within this graduation research.

This graduation position is offered to students that:

• Follow a master in civil engineering, mechanical engineering, maritime engineering, architecture or the built environment.
• Have an affinity with steel structures
• Have an affinity with numerical modelling
• Have an investigative and critical attitude, you want to know why certain phenomena occur and determine its effect.
• Like to cooperate with others and are creative;
• Live in The Netherlands, and is willing to work at least one day a week at our office in Delft.
• Have excellent oral and written communication skills in English, and preferably Dutch.

You want an internship opportunity on the precursor of your career; an internship gives you an opportunity to take a good look at your prospective future employer. TNO goes a step further. It’s not just looking that interests us; you and your knowledge are essential to our innovation. That’s why we attach a great deal of value to your personal and professional development. You will, of course, be properly supervised during your work placement and be given the scope for you to get the best out of yourself. Furthermore, we provide:

• A highly professional, innovative internship environment, within a team of top experts.
• A suitable internship allowance (615 euro for wo-, hbo- and mbo-students, for a full-time internship).
• Possibility of eight hours of free leave per internship month (for a full-time internship).
• A free membership of Jong TNO, where you can meet other TNO professionals and join several activities, such as sports activities, (work-related) courses or the yearly ski-trip.
• Use of a laptop.
• An allowance for travel expenses in case you don’t receive an OV-card.

At TNO, we innovate for a healthier, safer and more sustainable life. And for a strong economy. Since 1932, we have been making knowledge and technology available for the common good. We find each other in wonder and ingenuity. We are driven to push boundaries. There is all the space and support for your talent and ambition. You work with people who will challenge you: who inspire you and want to learn from you. Our state-of-the-art facilities are there to realize your vision. What you do at TNO matters: impact makes the difference. Because with every innovation you contribute to tomorrow’s world. Read more about TNO as an employer.

At TNO we encourage an inclusive work environment, where you can be yourself. Whatever your story and whatever unique qualities you bring to the table. It is by combining our unique strengths and perspectives that we are able to develop innovations that make a real difference in society. Want to know more? Read what steps we are taking in the area of diversity and inclusion.

After the first CV selection, the application process will be conducted by the concerning department. TNO will provide a suitable internship agreement. If you have any questions about this vacancy, you can contact the contact person mentioned below.

Important to be aware of before applying:

• Before the start of the internship, the internship agreement from TNO needs to be signed. For students at a college or university based in the Netherlands, TNO uses the UNL-template (supplemented with a number of specific agreements from TNO). For students of foreign and MBO educational institutions, the TNO internship agreement applies. TNO does not sign any other internship agreements.
• Before the start of the internship, the educational institution will need to confirm in writing that:
  • you are enrolled at the educational institution during the internship, and;
  • the internship takes place as part of the programme of the study.
• The confirmation of educational institution takes place by signing the UNL template or forms prepared by TNO.
• Interns at TNO must be in possession of a Dutch residential address at the start of the internship. Performance of internship activities from abroad is not possible.