Localized Finishing of Freeform Geometries using Dynamic Magnetic Field-Manipulated Magneto-Viscoelastic Fluids

生物医学假体植入物（如全髋关节）的需求正以每年5%的速度增长，预计到2019年这个市场将超过350亿美元。局部精加工的目标区域的表面的各种接头是必不可少的，他们的寿命保证。该行业在很大程度上依赖于费力和昂贵的手工或化学蚀刻方法进行局部精加工。该奖项支持基础研究，这些研究可以导致使用磁能和磨料混合的磁性“斑点”（非磁性流体中的半固体球体）进行表面局部精加工的新机床。这些机床对于定制，功能自由零件（例如，耐用的单件假体部件）的经济实惠制造至关重要。本研究的重点是研究磁流体的组成和外磁场的时空变化对1-10 sq范围内材料的选择性和去除率的影响。由抗磁性或弱顺磁性材料制成的自由零件上的Cm面积。第一个研究目标是建立磁流体团块的流变特性与其胶体组成和外部磁场时空变化之间的定量关系：这一知识对于选择磁场模式至关重要，这些磁场模式可以产生有利于磁流体最佳流动和选择性的梯度，并使团块施加适当的下降压力。为了实现这一目标，一项实验研究将采用一种专门的流变仪，该流变仪配备了磁体阵列、高斯计以及力和振动传感器。流变仪提供了一种可控的方法来估计磨料颗粒流体的磁粘弹性特性（基于橡胶弹性理论），以及不同流体成分和工件表面的材料去除率，并测量感应磁场、力和下压。第二个目标是建立磁团上产生的局部磁场梯度与应用的时空磁场之间的关系：所得知识将为在指定位置实现尖锐磁梯度提供指导，并设计能够创建这些图案的磁外壳。为了实现这一目标，将采用一种新的隐式粘弹性建模方法。该方法利用从第一个目标中收集的性质关系，提供了一种计算效率高的方法来捕获团块行为，包括从类磁弹性固体响应到磁粘弹性流体响应的平滑过渡。

Demand for biomedical prosthetic implants (e.g., total hip joints) is growing by 5 percent annually and this market is expected to exceed $35B by 2019. Local finishing of targeted regions of the surfaces of various joints is essential for their life assurance. The industry largely depends on laborious and expensive manual or chemical etching methods for localized finishing. This award supports fundamental research that can lead to new machine tools that use magnetic energy and abrasive-mixed magnetic "blob" (semisolid globule in a nonmagnetic fluid) for localized finishing of surfaces. These machine tools can be vital for affordable manufacturing of custom, functional free-form parts (e.g., durable, single piece prosthetic components). The focus of this research is on the effects of the composition of the magnetic fluid as well as the spatio-temporal variation of the external magnetic fields on the selectivity and material removal rates over 1-10 sq. cm area on freeform parts made of diamagnetic or weak paramagnetic materials. The first research objective is to establish quantitative relationships connecting the rheological properties of magnetic fluid blobs with their colloidal compositions and the spatio-temporal variation of external magnetic fields: This knowledge is essential to select magnetic field patterns that can create gradients conducive for optimal flow and selectivity of magnetic fluids, and make a blob exert appropriate down pressures. To achieve this objective, an experimental study will be conducted employing a specialized rheometer instrumented with array of magnets, Gauss meters, as well as force and vibration sensors. The rheometer provides a controlled means to estimate both the magneto-viscoelastic properties of the abrasive granular fluid (based on rubber elasticity theory) as well as the material removal rates for different fluid compositions and workpiece surfaces, and measure the induced magnetic field, forces, and the down pressure. The second objective is to establish a relationship between the localized magnetic field gradients induced over a magnetic blob and the applied spatio-temporal magnetic field: The resulting knowledge will provide guidance to realize sharp magnetic gradients at specified locations, and design magnetic enclosures capable of creating these patterns. To achieve this objective, a novel implicit viscoelastic modeling approach will be employed. This approach uses the property relationships gathered from the first objective to provide a computationally efficient means to capture the blob behaviors, including smooth transition from a magneto-elastic solid like response to that of a magneto-viscoelastic fluid.