Collaborative Research: Understanding and Controlling the Resistance to Scratching in Alkali-Free Glasses

随着LCD/OLED面板的基板玻璃和触摸屏计算设备的防损坏保护盖的出现，人类与玻璃表面的物理交互比以往任何时候都要多。然而，由此产生的划痕引起的损坏的风险仍然是一个关键问题，这严重限制了玻璃在许多应用中的适用性。实际上，由磨损产生的残留槽倾向于影响玻璃的视觉方面，这进而使它们的透明度劣化。更重要的是，表面损伤的存在大大降低了玻璃的强度，从而引起安全问题。为了解决这些问题，本研究旨在揭示钙铝硅酸盐玻璃中玻璃划伤的物理特性，钙铝硅酸盐玻璃是用于显示应用的无碱玻璃的典型模型。这项努力旨在提供一个基于科学的基础，以开发对刮擦有定制反应的新眼镜。这将有助于促进国民健康，繁荣和福利，通过允许眼镜被设计和用于具有期望的故障机制的更广泛的应用，例如允许手持计算设备上的屏幕更耐破碎。通过整合多个学科，包括物理学，材料科学和力学，这项研究将在工程的各个方面培养多样化的学生群体，并有助于形成美国玻璃行业迫切需要的下一代科学家，以在全球范围内竞争。此外，该奖项将支持两个机构的几项教育和外联活动，例如，本科生研究，女性和少数民族学生的参与，以及高中STEM活动。玻璃表面损伤是玻璃表面损伤的主要类型之一，会大大降低玻璃的耐用性。实际上，通常由于刮擦瑕疵而形成的径向和中间裂纹充当玻璃表面上的应力放大器或奇点，并且因此通过降低其机械强度而对玻璃的结构完整性具有直接影响。然而，迄今为止，玻璃刮擦的力学仍然主要是经验性的。为了解决这一知识差距，一个综合的，多尺度的方法，依靠计算和实验任务，计划揭示物理划伤无碱钙铝硅酸盐玻璃。为此，我们采用了多尺度，自下而上的方法，其中分子动力学模拟，结构表征测试，和纳米级的机械实验被用来通知连续的周期性模型，目的是解构的贡献，每个能量耗散机制在刮擦。将通过划痕试验系统地验证周波模型的预测。多个尺度之间的握手将提供一些新的基础知识，作为指导，阐明玻璃的成分和原子结构如何控制作用于刮擦的每个能量耗散机制的性质和程度。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the advent of substrate glasses for LCD/OLED panels and damage-resistant protective covers for touch-screen computing devices, humans physically interact with glass surfaces now more than ever. However, the resulting risk for scratch-induced damage remains a key concern, which seriously limits glass's suitability to many applications. Indeed, residual troughs resulting from abrasion tend to impact the visual aspect of glasses, which, in turn, deteriorates their transparency. More importantly, the presence of surface damage greatly decreases glass's strength, thereby raising safety issues. To address these concerns, this research aims to reveal the physics of glass scratching in calcium aluminosilicate glasses, an archetypical model for alkali-free glasses used in display applications. This effort seeks to provide a science-based foundation to develop new glasses with tailored responses to scratching. This will contribute towards the advancement of national health, prosperity, and welfare, by allowing glasses to be designed and used for a broader range of applications with desired failure mechanisms, for example allowing screens on handheld computing devices to be more resistant to shattering. By integrating multiple disciplines, including physics, material science, and mechanics, this research will train a diverse group of students in various aspects of engineering and contribute to forming the next generation of scientists that the U.S. glass industry critically needs to compete globally. Additionally, the award will support several educational and outreach activities at both institutions, e.g., undergraduate research, female and minority student participation, and high school STEM events. Scratching remains one of the main types of surface damage and can greatly reduce the durability of a glass. Indeed, the radial and median cracks that often develop as a result of a scratching flaw act as stress amplifiers or singularities on the surface of glasses and, thereby, have a direct influence on glass's structural integrity by decreasing its mechanical strength. Yet, the mechanics of glass scratching has remained chiefly empirical thus far. To address this gap of knowledge, an integrated, multiscale approach relying on both computational and experimental tasks is planned to reveal the physics of scratching in alkali-free calcium aluminosilicate glasses. To this end, we adopt a multiscale, bottom-up approach wherein molecular dynamics simulations, structure characterization tests, and nanoscale mechanical experiments are used to inform continuum peridynamic models with the aim to deconstruct the contribution of each energy dissipation mechanism during scratching. The predictions from peridynamic models will be systematically validated by scratch testing. The handshake between multiple scales will provide some new fundamental knowledge serving as a guide to elucidate how the composition and atomic structure of a glass control the nature and extent of each energy dissipation mechanism that acts upon scratching.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.