Microstructural Length Scale in Rolling and Sliding Contacts

滚动和滑动接触中的微观结构长度尺度理查德·W·诺伊乔治·W·伍德拉夫机械工程学院和材料科学与工程学院佐治亚理工学院佐治亚州亚特兰大由于接触点和附件处发生的疲劳和断裂过程而导致在用部件失效，这对消费者和企业来说是沉重的年度成本负担。 目前，人们对摩擦的微观结构-性能-性能关系知之甚少，缺乏计算材料科学工具的大量输入，特别是在介观微观结构长度尺度上。 这项研究根据明确捕获晶体金属和合金中的微观结构长度尺度，重新审视了牵引滚动和滑动接触中的摩擦能量耗散。 晶体结构本身无法解释摩擦力的差异，必须研究晶体塑性框架中变形的细节。 为了探索该方法的优点，将使用弹性晶体粘塑性材料模型重新审视表面层弹塑性变形的基础研究。 这些模型将使用捕获微观结构长度尺度的新实验方法进行校准和验证。基于电子背散射衍射（EBSD）的最先进的定向成像显微镜将用于绘制表面层的空间微观结构变化，以确定微观纹理、晶粒和位错亚结构形成以及牵引滚动和滑动接触过程中发生的微裂纹的演变。 这项研究是开发基础材料模型的一步，这些模型可以作为摩擦学相关涂层和薄膜材料设计应用的构建模块。 这项研究将有助于建立下一代计算材料设计方法，用于耐磨涂层、微动疲劳和磨损的缓和剂、结构附件的材料界面以及微型机械中的摩擦学界面。

Microstructural Length Scale in Rolling and Sliding ContactsRichard W. NeuThe George W. Woodruff School of Mechanical Engineeringand School of Materials Science and EngineeringGeorgia Institute of TechnologyAtlanta, GeorgiaFailure of in-service components due to fatigue and fracture processes occurring at points of contact and attachments is a heavy annual cost burden on consumers and corporations. Microstructure-property-performance relations for friction are poorly understood at present, lacking substantial input from computational materials science tools particularly at the mesoscopic microstructural length scale. This research revisits friction energy dissipation in tractive rolling and sliding contacts in light of explicitly capturing the microstructural length scale in crystalline metals and alloys. Crystal structure alone cannot explain differences in friction and one must look at the details of the deformation in a crystal plasticity framework. To explore the merits of the approach, fundamental studies of elastic-plastic deformation of the surface layer will be reexamined using an elastic - crystal viscoplasticity material model. The models will be calibrated and validated using new experimental approaches that capture the microstructural length scale. State-of-the-art orientation imaging microscopy based on electron backscatter diffraction (EBSD) will be use to map out the spatial microstructural changes in the surface layers to establish the evolution of microtexture, grain and dislocation substructure formation, and microcracks occurring during tractive rolling and sliding contacts. This research serves as a step in developing fundamental materials models that can serve as building blocks for applications of materials design applied to tribological-relevant coatings and thin films. This research will help to establish next generation computational materials design approaches for wear resistance coatings, palliatives for fretting fatigue and wear, materials interfaces at structural attachments, and tribological interfaces in micro-machines.