SGER: Investigation of Auxetic Metals

摘要：本SGER研究项目包括对表现出失活或负泊松比行为的金属进行调查，并对利用这种效应的工程应用进行可行性研究。形变材料是在拉伸或拉伸载荷作用下其横向尺寸增大的材料。这种新颖的、违反直觉的行为已被用于各种复合结构系统、泡沫和聚合物。然而，表现出形变特性的金属是罕见的，并且为了观察这种效应，需要相对于分子晶格取向仔细地定位结构成员的取向。这项研究工作将包括分析和测量单晶和纹理多晶金属的机械性能，如弹性模量和泊松比，特别关注铁铝合金（Alfenol）和一种相对较新的材料，铁镓合金（Galfenol）。[110]取向Alfenol和Galfenol泊松比的初步预测分别表明，可以实现低至-0.44和-0.75的值。该研究将对这些材料进行研究，并开发有限元模型，用于识别具有最适合设计和开发紧固件的特性的auxetic金属成分，这些紧固件由于材料的auxetic特性引起的横向膨胀而在拉伸载荷下产生摩擦而起作用。如果成功，这项研究将带来广泛的商业影响，因为紧固件的应用为连接结构成员提供了一种经济实惠的替代方法。如果作为单组件紧固件有效，那么在许多用途中，双组件螺母和螺栓连接器可能会被取代，特别是在空间应用和微系统应用中，在这些应用中，操纵螺母紧固螺栓存在固有的困难。此外，在学年和夏季期间，首席研究员在吸引代表性不足的本科生参与实验室研究经验方面有着良好的记录，并将在整个项目过程中为女性和少数民族学生提供研究机会。

PI: Alison FlatauInstitution: University of MarylandTitle: Investigation of auxetic metalsAbstract:This SGER research project entails an investigation of metals that exhibit auxetic or negative Poisson's ratio behavior and a feasibility study into engineering applications that use this effect. An auxetic material is one that increases in its lateral dimension in response to stretching or tensile loading. This novel and counterintuitive behavior has been used to advantage in a variety of composite structural systems, cellular foams, and polymers. However, metals that exhibit auxetic properties are rare and require careful orientation of a structural member relative to the molecular crystal lattice orientation for observation of this effect. This research effort will include analysis and measurement of mechanical properties such as elastic modulus and Poisson's ratio in single crystal and textured polycrystal metals, with a particular focus iron-aluminum alloys (Alfenol) and on a relatively new material, the iron-gallium alloy known as Galfenol. Preliminary predictions of Poisson's ratio's for Alfenol and Galfenol in a [110] orientation indicate respectively that values of as low as -0.44 and -0.75 can be realized. The study will investigate these materials and develop finite element models for use in identifying compositions of auxetic metals with properties best suited for the design and development of fasteners that function because of friction induced under tensile loading due to transverse expansion resulting from the auxetic nature of the material. The proposed research offers the potential for a broad commercial impact if successful, as the fastener application suggested offers an affordable alternative to nut-and-bolt methods for joining structural members. If effective as a single component fastener, there should be many uses in which two-component nut-and-bolt connectors might be replaced, especially in space applications and in microsystem applications, where there are inherent difficulties in manipulation of the nut to secure a bolt. Additionally, the principal investigator has a strong track record for engaging underrepresented undergraduate students in laboratory research experiences both during the academic year and summers, and will offer research opportunities for both women and minorities students throughout the course of this project.