Simple lessons to keep in mind when adding complexity to numerical models – inaugural address of Prof Schalk Kok

Posted on October 05, 2021

Congratulations to Prof Schalk Kok, professor in the Department of Mechanical and Aeronautical Engineering, who delivered his virtual inaugural address, titled Simple lessons to keep in mind when adding complexity to numerical models, on 14 September 2021. The Dean of the Faculty of Engineering, Built Environment and Information Technology (EBIT), Prof Sunil Maharaj, welcomed the guests and invited Prof Themba Mosia, Vice-Principal of Student Life, to introduce Prof Kok and deliver a summary of his career path.

Prof Kok obtained his BEng degree from the University of Pretoria in 1994. He completed his MEng on numerical optimisation to solve structural mechanics problems at the same institution in 1996. He obtained his PhD from the University of Illinois at Urbana-Champaign in 2002. Kok developed a polycrystal plasticity code to model strain rate and the temperature-dependent response of metals. Prof Kok started his career at Sasol Secunda in 2002, after which he joined the University of Pretoria in 2003. Between 2009 and 2013, he worked at the CSIR but ultimately returned to the University in 2013. Prof Kok’s primary research interest focuses on developing material models used in the numerical modeling of mechanical systems.

According to Prof Kok, they increasingly use numerical modeling to predict the response of physical systems. His address focused on predicting material response (displacements, stresses, and strains). Prof Kok added that a crucial ingredient for numerical prediction is a constitutive model, a mathematical formulation that predicts material stress due to any imposed pressure. Should the constitutive model not fit the experimental dataset, it may seem attractive to add complexity to the model to serve the experimental dataset better. His address illustrated the pitfalls in this approach if the experimental dataset does not contain sufficient information to identify all the constitutive model parameters. Prof Kok explained that one strategy to determine which parameters they can locate from the experimental dataset is to solve a virtual inverse problem. They replace the observed data with simulated data, so the solution to the inverse problem is known and allows one to determine which parameters are identifiable. To identify the elusive parameters, scientists can propose additional experiments if they are familiar with the constitutive model. They use numerous examples ranging from engineering materials (steel) to biomaterials (human cornea) to demonstrate this concept.

Prof Sunil Maharaj, the Dean of EBIT, thanked Prof Kok for his deep and insightful presentation. He added that the exhibition is critical to take South Africa and the African continent to a new dimension to be innovative in investigating various challenges. Sincere congratulations once more to Prof Kok for his hard-earned success and this milestone achievement.

For Prof Kok’s entire inaugural address, please visit the following link:


- Author Suzanne de Wit
Published by Dudu Mathe

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