Below a number of the projects I have carried out since the 1980's are briefly presented. The selection is based on my own perception of value for the stakeholders involved, how much I learned in the project and how much fun it was to do the research with colleagues and partners.

Thermomechanical fatigue of welds in a steel boiler
In 1980, during my MS study Mechanical Engineering at Eindhoven University of Technology,  I worked for a year together with Gerrit Peters under supervision of Leo Braak on prediction of lifetime under cyclic thermomechanical loading of welds in a steel boiler. The welds in the boiler cracked after a few hundred cycles and the manufacturer urgently needed a solution for economic reasons. Together with a colleague student I worked on the development of an axisymmetric thin shell finite element and carried out multiscale FEM analyses, made lifetime predictions using available material data and optimized the geometry of the bolier and the welds.

Lesson learned: the value of numerical simulations in combination with experimental data to solve real problems for industry.

Motions in the cervical spine
In 1981, during my MS study Mechanical Engineering at Eindhoven University of Technology,  I worked for a year at Maastricht University under supervision of Henk van Mameren to develop a computer program that allows for calculation of motions in the cervical spine. Starting point were successive 2D photographs with markers at selected reference points. I developed a FORTRAN IV program on a PDP11 computer in combination with a digitizer to acquire the successive positions of the markers. This resulted in absolute and relative motions of the vertebrae in the spine.

The project later resulted in a publication on calculation of 3D motions of rigid bodies: F.E. Veldpaus, H.J. Woltring and L.J.M.G. Dortmans, A Least-Squares Algorithm for the equiform transformation from spatial marker coordinates, J. Biomechanics, 21(1):45-54 (1988). This paper has many citations, even after 35 years, and can be considered as a standard computational method with many different applications.

This project triggered my interest for biomechanical engineering and resulted in my PhD thesis on Aspects of the dynamic behaviour of the human knee joint in 1988, promotors Jan Janssen (TU/e) and Toon Huson (UL), co-promotor Fons Sauren.

Lessons learned: the value of computer programming in combination with experimental data in biomechanics. The complexity of understanding needs from a scientist in a completely different discipline.

CEN TC184/VAMAS Grainsize measurement
In 1991-1992 I carried out a project for testing measurement methods to determine the grain size distribtion of a sintered ceramic material. The Round Robin project was in collaboration with Bert de With, Roger Morrell (NPL,UK) and George Quinn (NIST, USA). The outcome of the project was pubslished as a CEN TC184/VAMAS report in 1993 and later incorporated in a CEN TC184 and ISO TC206 standard in 2012, which is still confirmed.

Lessons learned: the need for international networking and collaboration to realise international projects and standards.

Mechanical properties of MnZn ferrite cores
Between 1993 and 1999, I was involved in a set of projects focussing on mechanical reliability of MnZn ferrite cores for power applications, both at TNO and TU/e. This resulted in a number of publications and the thesis by Maurice Donners on fracture of MnZn ferrites. Research was on various failure modes under mechanical loading, defects in relation to processing, slow crack growth and glueing. The projects were under the supervision of Bert de With and Mart de Graaf (Philips Components, Ferroxcube/Yageo). These projects included valuable collaborations with production locations in Hamburg (D), Southport (UK) and Saugerties (USA). In these projects we could transfer all fundamental knowledge on fracture mechanics of brittle materials we had developed since 1988 into a real application. Unfortunately by the end of the era, Philips sold most of its component activities and the research activities stopped. The contacts established also led to a nice related project on reliability of hexaferrites with Philippe Tenaud (Ugimag/Carbone Lorraine).

Lessons learned: the value of fracture mechanics and fractography to solve real problems for industry. Industry has detailed practical knowledge and know-how.

Fracture of fingertype ceramic lambda sondes
In 2000 I conducted a project focussing on reliability of fingertype lambda sondes, a ceramic high temperature sensor for measuring the residual oxygen content of the exhaust gas of an automobile. These sensors are made from a functionally coated ceramic and need to withstand a quality control test after production. Too many of the sensors fractured during this test for unknown reasons. Together with colleagues from FGK we conducted a series of experiments, and through careful fractography the cause for the fractures was identified and remedied. Optical and SEM imaging proved most important to identify the fracture origins, the defects at these origins and their origin (processing and handling)

Lessons learned: the value of fracture mechanics and fractography to solve real problems for industry.

Crack growth in laminated automotive windscreens
In 1999-2000 I worked on a project on crack growth in automotive windscreens, together with my colleague Yvonne Vossen. The laminated windscreens are damaged due to impact with a sharp object (a stone e.g.). The cracks are subjected to a combination of wind, thermal and mechanical loading, in particular as a result of heating a cold windscreen during winter. The induced stresses lead to crack growth and the need to replace the windscreen for safety reasons, unless the crack is repaired. The project focused on the determination of the imposed stresses, the crack morphology and the crack growth speed as a function of environmental conditions (moisture). The overall conclusion was that rapid heating of a cold windscreen leads to accelerated crack growth and urgency for repair or replacement of the windscreen.

Lessons learned: the value of fracture mechanics and fractography to solve real problems for industry.

Nanocomposite reinforced porous PMMA pressure casting moulds
Nanocomposite materials: from lab-scale experiments to prototypes

Knowledge worker scheme
How the Dutch economy in 2009 kept her knowledge workers

Plasmonic particles
Plasmonic particles for energy conversion

Growth Fund Duurzame MaterialenNL
From 2020-2022 I was member of the steering committee of the Growth Fund Duurzame MaterialenNL. Together with Albert Polman, Hans van der Weijden, Esther van den Beuken, Bruno Ehrler and Maurits Boeije we prepared an important material wide research proposal with significant industrial, scientific and governmental support. By 2023 most of the original 1.5 BEUR proposal was granted, leading to an significant impulse for materials research in the Netherlands. Circular Plastics is one of the proposals granted, which I picked up during my work at Brightlands Chemelot Campus in Brightlands Circular Space. For me this project was the culmination of many years presence and activity in the materials research field in the Netherlands, through academia, NWO, MinEZK, MinIenW, Topsector Chemistry, NEN etc. etc.

Lessons learned: the succes of a BIG proposal depends on a few people doing all the hard work and many many people doing a lot of support and story telling, networks are most important.