Impact of structure and relaxation on fatigue and micromechanical properties of oxide glasses - the role of volatiles and bonding state

结构和松弛对氧化物玻璃疲劳和微机械性能的影响——挥发物和键合状态的作用

• 批准号: 224489083
• 负责人: Professor Dr. Harald Behrens
• 金额: --
• 依托单位: Institut für Mineralogie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/224489083?language=en
• 关键词: Impact; structure; relaxation; fatigue; micromechanical

As subcritical crack growth (SCCG) can reduce tensile strength of glasses by many orders of magnitude, the potential for improvement of fatigue behaviour is most intriguing in developing ultra-strong glasses. An essential bottleneck is the basic understanding of the numerous interplaying pressure- temperature- and water- affected relaxation phenomena at the crack tip and related toughening strategies.Therefore, the present proposal aims to advance the basic understanding of structural relaxation effects and local properties caused by increased volatile concentration and tensile stresses at the crack tip. For this sake, glass topology will be designed physically by preparation of glasses of different P-T histories as well as compositionally by incorporation of volatiles (the focus will be on H2O) into the compressed glass structure. Both are expected to have a strong influence on the viscoelastic properties (complex moduli) of the near-tip glass structur.Therefore the project is composed in the first funding period by three interrelated experimental tasks: Task 1) Synthesis of glasses with different volatile contents and different P-T histories and characterization of structural and bulk mechanical properties of the glasses, Task 2) Studies of sub-Tg relaxation processes in these glasses by mechanical spectroscopy, Task 3) Experimental investigation of crack formation and propagation using in situ and ex situ (indentation) techniques. Cooperation within SPP 1594 will provide basis to implement time-dependent viscoelastic properties into theoretical descriptions of fracture mechanics and will deliver sub-Tg onset temperatures for modelling topological constraints down to room temperature. The project aims therefore to advance the basic understanding of the local relaxation mechanism controlling SCCG and micro-mechanical properties in oxide glasses as they are a key for structural toughening designs to develop SCCG-free glasses and glass surfaces.

由于亚临界裂纹的生长（SCCG）可以通过许多数量级来降低玻璃的拉伸强度，因此改善疲劳行为的可能性在开发超强玻璃杯中最吸引人。必不可少的瓶颈是对裂纹尖端和相关韧性策略的众多相互作用压力温度和受影响的放松现象的基本理解。因此，本提案旨在提高对结构放松效应的基本理解，以及对裂纹尖端的挥发性浓度和拉伸应力引起的局部特性。为此，玻璃拓扑是通过制备不同P-T历史的玻璃以及通过将挥发物（将焦点放在H2O上）在压缩玻璃结构中进行物理设计的。预计两者都对近尖玻璃结构的粘弹性特性（复杂模式）都有很大的影响。因此，该项目在第一个相互关联的实验任务中在第一个资金期间组成：任务1）与玻璃的合成不同的波动性内容和不同的P-T历史和不同的玻璃的机械性能，玻璃的机械性能2）的玻璃的镜头，这些玻璃的机械性能2）光谱，任务3）使用原位和原位（压痕）技术对裂纹形成和传播的实验研究。 SPP 1594中的合作将提供基础，以将时间依赖性的粘弹性特性实施到断裂力学的理论描述中，并将提供亚电-TG的发作温度，以将拓扑结构降低到室温。因此，该项目旨在促进对氧化物玻璃杯中控制SCCG和微机械特性的局部放松机制的基本了解，因为它们是结构性韧性设计的关键，以开发无SCCG的无SCCG玻璃杯和玻璃表面。