In the last two decades, the reliability of small electronic devices used in automotive or consumer electronics gained researchers attention. Thus, there is the need to understand the fatigue properties and damage mechanisms of thin films. In this thesis a novel high-throughput testing method for thin films on Si substrate is presented. The specialty of this method is to test one sample at different strain amplitudes at the same time and measure an entire lifetime curve with only one experiment.

The grain microstructure and damage mechanisms at the grain level are the key factors that influence fatigue of metals at small scales. This is addressed in this work by establishing a new micro-mechanical model for prediction of multiaxial high cycle fatigue (HCF) at a length scale of 5-100?m. The HCF model considers elasto-plastic behavior of metals at the grain level and microstructural parameters, specifically the grain size and the grain orientation.

Single crystalline, μm-sized cantilevers are fabricated out of epitaxially grown Ag thin films by a lithography-based procedure and are deflected by a nanoindenter system. The microstructure of the plastically deformed cantile-vers is investigated using transmission Kikuchi diffraction (TKD) on the cantilever cross section. 3D discrete dislocation dynamics simulations (DDD) are performed for further analysis. A mechanism to explain the formation of dislocation networks upon loading is suggested.

This book investigates the fatigue mechanisms and crack initiation of Ni, Al and Cu on a small-scale in the Very High Cycle Fatigue regime by means of innovative fatigue experimentation. A novel custom-built resonant fatigue setup showed that the sample resonant frequency changes with increasing cycle number due to fatigue damage. Mechanisms such as slip band formation have been observed. Cyclic hardening, vacancy and oxidation formation may be considered as early fatigue mechanisms.

Ink-jet printed devices on the flexible substrate are inexpensive and large area compatible as compared to rigid substrates. However, during fabrication and service they are subjected to complex strains, resulting in crack formation or delamination within the layers, affecting the device performance. Therefore, it is necessary to understand their failure mechanisms by correlating their electrical or structural properties with applied strain, supported by detailed microstructural investigations.

Custom built setups were developed to investigate micro samples during quasistatic and cyclic testing in tension, compression and bending. Micro molded CuAl10Ni5Fe4-samples showed similar fatigue behavior compared to macroscopic samples due to both the sample size and microstructure being scaled down with the manufacturing process. Results from cyclic three-point bending tests on micro molded 3Y-TZP suggested that a minimum crack extension is necessary to develop cyclically degradable shielding.

To determine the characteristics and properties of cellular solids for an application, and to allow a systematic practical use by means of correlations and modelling approaches, we perform experimental investigations and develop numerical methods. In view of coupled multi-physics simulations, we employ the phase-field method. Finally, the applicability is demonstrated exemplarily for open-cell metal foams, providing qualitative and quantitative comparison with experimental data.

Hierarchically structured active materials in electrodes of lithium-ion cells are promising candidates for increasing gravimetric energy density and improving rate capability of the system. To investigate the influence of cathode structures on the performance of the whole cell, efficient tools for calculating effective transport properties of granular systems are developed and their influence on the electrochemical performance is investigated in specially adapted cell models.

This book summarizes the found insights of grain growth behavior, of multidimensional decomposition for regular grids to efficiently parallelize computing and how to simulate recrystallization by coupling the finite element method with the phase-field method for microstructure texture analysis. The frame of the book is created by the phase-field method, which is the tool used in this work, to investigate microstructure phenomena.

Solid state batteries with a lithium metal electrode are considered the next generation of high energy battery technology. Unfortunately, lithium metal is prone to harmful protrusion or dendrite growth which causes dangerous cell failure. Within this work the problem of protrusion growth is tackled by deriving a novel electro-chemo-mechanical theory tailored for binary solid state batteries which is then used to discuss the impact of mechanics on interface stability by numerical studies.