November 4, 2016
M.Sc. Matti Lindroos has successfully demonstrated the use of Integrated Computational Materials Engineering (ICME) approach combining experiments and simulations to bring new perspectives to the development of wear resistant steels. His dissertation is the first one from the DIMECC Breakthrough Materials Doctoral School active since 2014. This largest industrial doctoral school in Finland produces results faster than expected.
The demand for more wear resistant materials originates from modern applications of many industries, such as mining, automotive, aerospace and civil structures. The motivation to develop more efficient engineering structures and components can be seen beneficial in both economically and environmentally. In the DIMECC Breakthrough Steels and Applications (BSA) program, th
e target has been lighter, higher strength, and more wear resistant solutions that give savings in energy consumption, higher load bearing capability, and increased component lifespan enhancing efficiency. This study was made in the Design beyond present codes project of DIMECC BSA in collaboration with SSAB Europe Oy and Metso Minerals Oy.
The wear resistance of a material itself is not a property but rather a measure of its performance in certain type of conditions. In his thesis, Matti Lindroos focused on the controlled wear testing and characterization of high and ultrahigh strength steel under abrasive and impact conditions to increase understanding of complex wear-property relationship of the materials. The in-situ characterization of the wear processes taking place at different time and length scales is difficult, but they can be studied with simulation models. Lindroos developed numerical crystal plasticity models to describe the deformation behaviour in the microstructural level.
Video: Evolution of microstructure scale a) stresses and b) distribution of deformation twins in high manganese austenitic steel (Hadfield steel) during crushing of 50 granite rocks.
“The microstructure of the material and the phenomena taking place at microscopic scale has a great relevance to the wear performance of the material because wear initiates from the fine scale deformation and fracture processes. When the aim is to develop and improve materials and their wear resistance, the simulation models that can describe material behaviour in the microscopic level are often more usable than common macroscopic models. However, it is crucial to verify the model responses with experiments. This is one of the driving forces for the combined experimental and simulations work in the dissertation”, Matti Lindroos states.
“My research exchange period at the École Nationale Supérieure des Mines de Paris brought a new perspective to the crystal plasticity modelling. Professor Georges Cailletaud and his group work in the Centre des Matériaux work with similar issues in material and damage modelling in multiscale and multiphysics environments. Although their focus has not been in wear research, I got invaluable help from them.”
According to Lindroos, the simplified and well-controlled experimental conditions reduce the complexity of the wear process. Moreover, the test procedures used in the thesis were found especially suitable for wear resistant steels revealing must desired critical characteristics affecting the wear behaviour. The use of controlled wear experiments also allows verifying of macroscopic wear models as it is possible to have same operational conditions in both experiments and simulations. An essential aspect of the simulation models is related usability of the modelling up to industrial scale applications and components. It was demonstrated that the meso-scale models, acting between microscopic and macroscopic scales, can offer this upscaling, making the multi-scale modelling really attractive approach for material research and development. In the future, the performed implementation of the modelling tools into widely used finite element method can enable the use of microstructure modelling also as a part of a typical designer tool set.
”The strength of our doctoral school is the intensive working mode, co-creation by 37 doctoral students with each other and their mentors, topnotch international research partners and the companies involved. Together we solve the critical application related research problems from our industry utilizing and developing novel modelling tools and specific experimental methods. The successful work by Matti Lindroos is a prime example of this”, says Prof. Kenneth Holmberg from VTT, the rector of DIMECC Breakthrough Materials Doctoral School.
“Our concept has already been proven efficient and successful, creating concrete competitive solutions for demanding applications and generating great value to Finnish industry. Another key outcome is building novel multi-disciplinary competence needed both in our industry and research. Next five new Doctors with capabilities for wide cooperation and industrial problem solving will be having their dissertations soon, and ready to take new challenges”, says Docent Markku Heino from Spinverse, Program Manager of DIMECC BSA & HYBRIDS.
Public defence of a doctoral dissertation on Friday 4th of November
M.Sc. Matti Lindroos will publicly defend his doctoral thesis “Experimental and Numerical Studies on the Abrasive and Impact Behavior of Wear Resistant Steels” on Friday, 4th of November 2016 starting at 12 in Tampere University of Technology, Konetalo, K1702. Dr. Samuel Forest from Centre des Matériaux of MINES Paris Tech, France and Prof. Lars-Erik Lindgren from Luleå University of Technology, Sweden, will act as opponents. The Custos is Prof. Veli-Tapani Kuokkala, from the department of Materials Science.
The dissertation is available online at: http://urn.fi/URN:ISBN:978-952-15-3828-5
Further information: Matti Lindroos, email@example.com
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The release in Finnish here