Research
Division of Applied Mechanics has research in fundamental science as well as in collaboration with industry. Below we summarize some of the current research projects for convincing the broad expertise in applied mechanics.
Additive manufacturing on the spotlight
We like 3-D printers and want to make them more useful than they are. Regarding their layer-by-layer production idea, it is possible to construct designs with cavities or inclusions. A repeated substructure in form of a honeycomb is often used for this purpose. Also a cellular structure, like we have it in our bones, is a typical example. Such porous structures are great for weight reduction, but what happens to the mechanical stiffness? We characterize materials response by simulations and experiments in order to get the full out of additive manufacture in applications.
We preserve our cultural heritage
Wood is a material for the future, since it is renewable, and a material of the past, widely present in our cultural heritage. We address the load carrying capacity and deformation of wood structures and wood materials, both new and old. Ongoing research spans from the molecular level, over the cell level, tissue and to timber structures. With experiments combined with modeling, we predict deformations and failure, and thereby provide a tool in design and preservation of wooden objects. In these efforts, we employ molecular dynamics, microscopy, X-ray computed tomography, composite mechanics, mechanical testing of wood samples and structures in controlled climate under static and creep conditions.
Metamaterials research: smaller gets stiffer
Mechanics is challenged by the miniaturization, where we want to have smaller and smaller mechanisms. As the geometry gets small in size, the molecular structure gets important how grains in metals or chains in polymers are distributed. For many engineering materials, smaller gets stiffer and such materials are called metamaterials with a mechanical response significantly altered by their substructures. We model and examine their properties. A well-known phenomenon, size effect, is seen on the simulation, the same beam in meter, millimeter, and in micrometer length is bending differently.
Smartphone stopped working, is this by design?
Hundreds of electronic components work continuously in a smartphone. As they manipulate electric signals, they get heated up, and then cool down. They are connected to motherboard by solders and other layers. As a consequence of temperature change, they expand and shrink, leading to thermomechanical loading. After many years of such a cyclic loading, the material gets fatigue, cracks are nucleated, and eventually, they hinder electric signals. All of a sudden, smartphone is non-responsive. A bit of bending may help, but not a real solution at all. One may wonder if the company can design such a behavior. The short answer: not even close! We develop multiphysics computations, where electro-thermo-mechanical processes are characterized. A better understanding of fatigue in such systems will help engineers to estimate replacement time or simply design components with longer service life.
Piezoceramics combine the two world
Classical school example is the frog's leg contraction under applied electricity. We know intuitively that electric energy is transferred to mechanical energy (motion). This phenomenon happens at the material level and called, piezoelectricity. Piezoceramics are used in automatic braking system (ABS), where en electric field brakes and releases the tires several times in a second, so the tires grasp the road better. More fun is to simulate a plastic with piezoceramic patches on it for using on a hot summer day as an air ventilator. Technically, electromechanical coupling is an electric motor, without any moving parts in it, so we can build it as small as we want. This technique is used in micropumps for very accurate transport of drugs into the vein.