W. Theisen

Mechanical properties of blood clots - a new test method

A blood clot needs to have the right degree of mechanical, chemical and biological properties to stem the flow of blood and yet to be suitable for lytic enzymes or mechanical thrombectomy so as not to form a thrombotic event. The origin and understanding of these mechanical properties are still unknown. Clots are made of a threedimensional network of fibrin fibers stabilized through ligation with a transglutaminase, factor XIIIa. New methods to achieve information about the in-situ mechanical properties were established. We performed compressive strength experiments of aged human blood clots. After the set up of a new test environment, we were able to perform in-situ tensile strength measurements of aged animal and human blood clots. Stress strain curves of aged clots were measured and discussed. The viscoelastic properties of the clot material were quantitatively described. This work should finally give a better understanding of the behaviour of aged blood thrombus bulk material and induced mechanical stress.

Finite element modelling of process-integrated powder coating by radial axial rolling of rings

The process‐integrated powder coating by radial axial rolling of rings represents a new hybrid production technique applied in the manufacturing of large ring‐shaped work pieces with functional layers. It is thought to break some limitations that come along with the hot isostatic pressing (HIP) which is used nowadays to apply the powdery layer material onto the rolled substrate ring. Within the new process the compaction of the layer material is integrated into the ring rolling and HIP becomes dispensable. Following this approach the rolling of such compound rings brings up some new challenges. The volume of a solid ring stays nearly constant during the rolling. This behaviour can be exploited to determine the infeed of the rollers needed to reach the desired ring shape. Since volume consistency cannot be guaranteed for the rolling of a compound ring the choice of appropriate infeed of the rollers is still an open question. This paper deals with the finite element (FE) simulation of this new process. Firs...