Mechanical Properties of Hydrogels - Comparison between DMA and AFM Measurements of Elastic Modulus

Polymer hydrogels consist of polymer network that is able to absorb large amount of water. They have plenty of real-life applications - for example in medicine and diagnostics. The aim of this thesis is to study elastic modulus of several hydrogel samples by two different methods - dynamical mechanical analysis (DMA) and atomic force microscopy (AFM). Dynamical mechanical analysis represents a traditional method, which is expected to supply very reliable data. On the other hand - there has not been done much research in the field of studying mechanical properties with atomic force microscopy yet. This thesis should result into comparison of these two methods and describing effects that influence the measurement

Mechanical Properties of Hydrogels - Comparison between DMA and AFM Measurements of Elastic Modulus

Polymerní hydrogely jsou zesíťované polymery, které jsou schopné do sebe absorbovat velké množství vody. Mají řadu využití v mnoha oblastech lidské činnosti - zejména v lékařství a diagnostice. Tato práce si klade za cíl studovat modul pružnosti několika hydrogelových vzorků za pomocí dvou metod - dynamické mechanické analýzy (DMA) a mikroskopie atomárních sil (AFM). Dynamická mechanická analýza je tradičně používaná metoda, která poskytuje velmi spolehlivé výsledky. Oproti tomu studium modulu pružnosti hydrogelů pomocí mikroskopie atomárních sil je oblastí, která dosud není příliš dobře prozkoumána. Výsledkem této práce by mělo být porovnání dat získaných těmito dvěma metodami a popis vlivů, které měření ovlivnily.Polymer hydrogels consist of polymer network that is able to absorb large amount of water. They have plenty of real-life applications - for example in medicine and diagnostics. The aim of this thesis is to study elastic modulus of several hydrogel samples by two different methods - dynamical mechanical analysis (DMA) and atomic force microscopy (AFM). Dynamical mechanical analysis represents a traditional method, which is expected to supply very reliable data. On the other hand - there has not been done much research in the field of studying mechanical properties with atomic force microscopy yet. This thesis should result into comparison of these two methods and describing effects that influence the measurement.Kabinet výuky obecné fyzikyLaboratory of General Physics EducationMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Fatigue properties of magnesium alloy AZ31 prepared by rotary swaging method

Magnesium alloys are considered to have a high potential for applications in many engineering fields. Specifically, AZ alloys are of low weight, good castability and strength and they are also fairly resistant to corrosion. Moreover, the mechanical properties can be further improved by metalworking tech- niques. Methods of severe plastic deformation are often used for this purpose. Rotary swagging, which is one of those methods, is used for tubes and rods crafting. This method allows the material structure to reach homogeneous microstructure in its full volume. There has already been a fine amount of research effort and studies done in regards to mechanical properties of AZ alloys prepared with the methods of severe plastic de- formation. The ultimate goal of this thesis is to study fatigue properties of said alloys, which have not been subjected to such research in sufficient volume as of yet.

Mechanical Properties of Hydrogels - Comparison between DMA and AFM Measurements of Elastic Modulus

Polymer hydrogels consist of polymer network that is able to absorb large amount of water. They have plenty of real-life applications - for example in medicine and diagnostics. The aim of this thesis is to study elastic modulus of several hydrogel samples by two different methods - dynamical mechanical analysis (DMA) and atomic force microscopy (AFM). Dynamical mechanical analysis represents a traditional method, which is expected to supply very reliable data. On the other hand - there has not been done much research in the field of studying mechanical properties with atomic force microscopy yet. This thesis should result into comparison of these two methods and describing effects that influence the measurement

Fatigue in an AZ31 Alloy Subjected to Rotary Swaging

The magnesium AZ31 alloy was swaged with rotary pressure with the aim of redefining the microstructure and improving mechanical and fatigue properties. The rotary swaging process and subsequent ageing improved the yield stress in tension and compression. In the present study, the investigation was focused on fatigue behaviour. The samples were cycled in a symmetric regime with a frequency of 35 Hz. A dependence of the stress amplitude on the number of cycles up to the fracture was estimated. The microstructure of the samples and fracture surfaces was analysed with a scanning electron microscope. The fatigue process was influenced by the pronounced texture formed in the swaging process. The fatigue properties of the swaged samples improved substantially—the endurance limit based on 107 cycles was approximately 120 MPa—compared to those of the cast alloy. The analysis of the fracture surfaces showed a transcrystalline fatigue fracture