Experimental Investigation of Crack Initiation in Face-Centered Cubic Materials in the High and Very High Cycle Fatigue Regime

Experimental Investigation of Crack Initiation in Face-Centered Cubic Materials in the High and Very High Cycle Fatigue Regime
Author: Straub, Thomas
Publisher: KIT Scientific Publishing
Total Pages: 234
Release: 2016
Genre: Technology (General)
ISBN: 3731504715

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.

Fatigue of Materials at Very High Numbers of Loading Cycles

Fatigue of Materials at Very High Numbers of Loading Cycles
Author: Hans-Jürgen Christ
Publisher: Springer
Total Pages: 624
Release: 2018-11-19
Genre: Technology & Engineering
ISBN: 365824531X

This book represents the final reports of the scientific projects funded within the DFG-SPP1466 and, hence, provides the reader with the possibility to familiarize with the leading edge of VHCF research. It draws a balance on the existing knowledge and its enhancement by the joint research action of the priority program. Three different material classes are dealt with: structural metallic materials, long-fiber-reinforced polymers and materials used in micro-electro-mechanical systems. The project topics address the development of suitable experimental techniques for high-frequency testing and damage monitoring, the characterization of damage mechanisms and damage evolution, the development of mechanism-based models and the transfer of the obtained knowledge and understanding into engineering regulations and applications.

A novel micro-mechanical model for prediction of multiaxial high cycle fatigue at small scales

A novel micro-mechanical model for prediction of multiaxial high cycle fatigue at small scales
Author: Eslami, Reza
Publisher: KIT Scientific Publishing
Total Pages: 142
Release: 2017-05-03
Genre: Technology (General)
ISBN: 3731505835

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.

Microplasticity of idealized single crystalline Ag cantilevers characterized with methods of high resolution

Microplasticity of idealized single crystalline Ag cantilevers characterized with methods of high resolution
Author: Wobrock, Mark
Publisher: KIT Scientific Publishing
Total Pages: 252
Release: 2017-11-22
Genre: Diffraction
ISBN: 3731506823

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.

Safe, Supportive, and Inclusive Learning Environments for Young People in Crisis and Trauma

Safe, Supportive, and Inclusive Learning Environments for Young People in Crisis and Trauma
Author: Patty Towl
Publisher: Routledge
Total Pages: 0
Release: 2020-06-02
Genre: Education
ISBN: 9781000051513

Children and young people from diverse populations are statistically more at risk of exclusion, however education providers can make a difference to all children and young persons’ learning outcomes no matter what their personal circumstances. To achieve this, not only must educators form closer and more authentic relationships with these children and their communities, but the governments that fund learning environments must also be prepared to provide adequate resourcing and training opportunities. Safe, Supportive, and Inclusive Learning Environments for Young People in Crisis and Trauma addresses both the general and specific issues that may prevent children and young people from diverse populations from being safe, supported, and included in learning environments. Some chapters focus on general factors that contribute to both inclusion and exclusion at early childhood and in formal school environments, while others present research-based best practice and practical advice to enable good education outcomes for indigenous, migrant, and LGBTQI children and those who experience mental health problems, drug misuse, and abuse. Lastly, the book includes information about how to negotiate and set up programmes that have been shown to be effective with communities that differ from the dominant culture. This book provides practitioners in education, health, and social work with information and practical advice on how to retain all children and young people in early childhood, formal school education, and tertiary settings.

Multiscale Modeling of Curing and Crack Propagation in Fiber-Reinforced Thermosets

Multiscale Modeling of Curing and Crack Propagation in Fiber-Reinforced Thermosets
Author: Schöller, Lukas
Publisher: KIT Scientific Publishing
Total Pages: 230
Release: 2024-03-15
Genre:
ISBN: 3731513404

During the production of fiber-reinforced thermosets, the resin material undergoes a reaction that can lead to damage. A two-stage polymerization reaction is modeled using molecular dynamics and evaluations of the system including a fiber surface are performed. In addition, a phase-field model for crack propagation in heterogeneous systems is derived. This model is able to predict crack growth where established models fail. Finally, the model is used to predict crack formation during curing.

Characterisation and Modelling of Continuous-Discontinuous Sheet Moulding Compound Composites for Structural Applications

Characterisation and Modelling of Continuous-Discontinuous Sheet Moulding Compound Composites for Structural Applications
Author: Trauth, Anna
Publisher: KIT Scientific Publishing
Total Pages: 468
Release: 2020-12-11
Genre: Technology & Engineering
ISBN: 3731509504

The main objective of this work is to significantly deepen the understanding of the material and the structural behaviour of continuous-discontinuous SMC composites, following a holistic approach to investigate microscopic aspects, macroscopic mechanical behaviour as well as failure evolution at the coupon, structure and component level. In addition, criteria to evaluate the effect of hybridisation are introduced and modelling approaches are presented and discussed.

On the Electro-Chemo-Mechanical Coupling in Solid State Batteries and its Impact on Morphological Interface Stability

On the Electro-Chemo-Mechanical Coupling in Solid State Batteries and its Impact on Morphological Interface Stability
Author: Ganser, Markus
Publisher: KIT Scientific Publishing
Total Pages: 272
Release: 2021-03-09
Genre: Technology & Engineering
ISBN: 3731510472

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.

Phase-field Modeling of Phase Changes and Mechanical Stresses in Electrode Particles of Secondary Batteries

Phase-field Modeling of Phase Changes and Mechanical Stresses in Electrode Particles of Secondary Batteries
Author: Zhang, Tao
Publisher: KIT Scientific Publishing
Total Pages: 224
Release: 2021-09-27
Genre: Technology & Engineering
ISBN: 3731510022

Most storage materials exhibit phase changes, which cause stresses and, thus, lead to damage of the electrode particles. In this work, a phase-field model for the cathode material NaxFePO4 of Na-ion batteries is studied to understand phase changes and stress evolution. Furthermore, we study the particle size and SOC dependent miscibility gap of the nanoscale insertion materials. Finally, we introduce the nonlocal species concentration theory, and show how the nonlocality influences the results.