Anisotropic cardiovascular tissue characterization

Although health care systems have made great strides in reducing death rates associated with cardiovascular diseases, they are still ranked amongst the main mortality causes in the western world.  It is known that the progression of cardiovascular diseases is associated with pathological alterations of the biomechanical performance of the cardiovascular system. Consequently, the characterization of normal and pathological cardiovascular tissue properties may help to further understand disease progression and even to optimize currently implemented health care therapies.  At KTH Solid Mechanics both, biaxial and uniaxial tensile testing systems are used to characterize viscoelastic and failure properties of a large range of vascular tissues. This information is used to develop anisotropic and finite strain constitutive descriptions, which in turn simulate the in-vivo conditions of normal and diseased vessels. 

Experiments and modelling for analysis of 3-D forming of paperboard

Deep-drawing and hydroforming are two methods under consideration for forming of complex shaped paperboard structures for packaging applications.  The objective of this project is to study deformation and damage mechanisms and to develop analysis tools for such 3-D forming techniques.  The Solid Mechanics laboratory within the Odqvist Laboratory has a unique hydroforming device which allows for the manufacturing of 3-D formed paperboard structures and the deep-drawing studies are carried out in cooperation with Dresden University of Technology. In the research work forming experiments using different types of commercial and laboratory materials are combined with finite element modelling of the manufacturing processes.  Recent advances in this thesis work have led to better understanding of the combined effects of moisture and temperature on the elastic-plastic behaviour of paper materials. Understanding of the effects of moisture and temperature is important for 3-D forming processes, because the application of temperature and/or moisture is typically necessary for 3-D forming success.

Hydrogen Embrittlement in High strength Steels

High Strength Steel (HSS) can be susceptible to Environmentally Assisted Cracking (EAC) and like any other susceptible material may suffer premature failure due to loss of ductility (embrittlement) and load bearing capacity. In this project, a fracture mechanics and material mechanics approach will be used in order to study the effect of EAC in HSS. The environments that will be studied have high hydrogen content which may lead to embrittlement of steels and could result in premature failure. The goal with the project is to develop a fracture mechanics testing method that gives reliable results and to implement the test method on real life applications for automotive-, vehicle-, offshore- and nuclear industry.

Characterization of High Strength Bearing Steel

High strength bearing steels are developed for very high contact pressures and compressive stresses. Local tensile stresses may however develop phase transformation. A side effect of the high strength is that stresses can become sufficiently large for unusual material behaviour. One such behaviour is solid to solid phase transformation which is dependent on temperature. Not only the phase change but also low temperature creep is also observed where low temperature can be defined as from room temperature to about 150 C. The purpose of the experiments is to measure the amount of phase change under different temperature and loading, and to quantify and predict the risk of creep rupture of existing cracks in a high strength bearing steel.

The work contains experiments and modelling of the crack behaviour at high static loads. The crack propagation and the material creep will be small which places high demands on accuracy in the experimental work and in the crack growth measurements. The measurements uses the potential drop techniques.

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