Collaborative Research: Improving contact fatigue and wear properties using graded nanostructured surfaces in metallic materials

非技术概述具有从表面区域的纳米级到内部区域的微米级的粒度梯度的分级纳米结构金属材料是一类新型材料，其表现出优异的机械性能的前景。然而，目前，人们对这些纳米级金属和合金的表面耐磨性和接触疲劳行为的了解非常有限。与具有均匀粒度的材料的情况不同，其中表面区域仅提供一种类型的表面磨损保护，在纳米级材料中，表面区域具有通过增加对损伤引发和随后损伤进展到材料内部的抵抗力来提供两种类型的保护的潜力。通过建模和实验，斯托尼布鲁克和麻省理工学院之间的合作项目，旨在获得一个科学的理解，在金属材料的梯度纳米结构表面的损伤启动和损伤演化过程。通过推进当前对梯度纳米结构材料的表面磨损保护和抗接触疲劳性相关机制的理解，该项目促进了在数十亿美元的摩擦学行业中可靠引入新材料的路线图的开发，该行业包括飞机，汽车，电子包装，核能和生物医学应用。技术总结本项目的重点是获得一个基本的了解接触疲劳裂纹阻力梯度纳米结构金属材料。特别是，位错活动的晶粒尺寸梯度和屈服强度梯度，裂纹尖端钝化和裂纹尖端屏蔽的影响，进行了评估。建立了一个基于粘附的分析模型框架，用于预测梯度纳米材料接触疲劳裂纹萌生的条件。采用基于位错堆积的多尺度塑性有限元模型预测梯度纳米结构金属和合金的接触疲劳损伤演化路径。接触疲劳和磨损实验的目的是提供一个定量评估的接触疲劳和磨损行为的梯度纳米材料和验证的分析和数值模型开发，而微观结构的观察识别变形机制，有助于接触疲劳抗力和磨损损伤保护。一个新的设计范例工程功能梯度纳米材料，提供增强的接触疲劳损伤抵抗力，超出了经典的限制，已在传统上获得的材料（大多是均匀的）表面改性层，被identified.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

Non-technical summaryGraded nanostructured metallic materials, with grain-size gradients ranging from the nanometer-level in the surface regions to the micrometer-level in the interior regions, are a novel class of materials that have exhibited promise for exceptional mechanical properties. However, at present, there is very limited understanding of the surface wear resistance and contact fatigue behavior of these nano-graded metals and alloys. Unlike in the case of materials with a uniform grain-size, where the surface region provides only one type of surface wear protection, in the nano-graded materials, the surface region has the potential to provide two types of protection by increasing the resistance to both damage initiation and subsequent damage progression into the interior of the material. Through modeling and experiments, this collaborative project between Stony Brook and MIT, seeks to obtain a scientific understanding of damage initiation and damage evolution processes in metallic materials with graded nanostructured surfaces. By advancing the current understanding of the mechanisms associated with surface wear protection and contact fatigue resistance of graded nanostructured materials, this project facilitates the development of a road-map for the reliable introduction of novel materials in the multi-billion dollar tribology industry that includes aircraft, automotive, electronic packaging, nuclear energy, and biomedical applications. Technical SummaryThis project is focused on obtaining a fundamental understanding of the contact fatigue crack resistance in graded nanostructured metallic materials. In particular, the influence of dislocation activities that are dictated by grain-size gradients and yield strength gradients, on crack tip blunting and crack tip shielding, is assessed. An adhesion-based analytical modeling framework is developed to predict the conditions for contact fatigue crack initiation in graded nanomaterials. A dislocation pile-up based multi-scale plasticity model is implemented in finite elements to predict contact fatigue damage evolution pathways in graded nanostructured metals and alloys. Contact fatigue and wear experiments are designed to provide a quantitative assessment of contact fatigue and wear behavior of graded nanomaterials and validation for the analytical and numerical models developed, while microstructural observations identify deformation mechanisms that contribute to contact fatigue resistance and wear damage protection. A new design paradigm for engineering functionally-graded nanomaterials that provides enhancements in contact fatigue damage resistance, beyond the classical limit that has been traditionally obtained in materials with (mostly uniform) surface modified layers, is identified.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.