The unique rheological properties of discontinuously shear thickening fluids (STF) have been employed in various engineering applications in recent years. In a commercial aspect, this has most notably been body armor and protective equipment, but also specialized smart structures in damping and force-coupling applications. The topic of this work is the application of STF in an articulating prosthetic foot for adaptable force response. Connected in series and parallel to a spring system, a STF based element can be used to affect the force transfer within the system, and thereby, influence the stiffness of the prosthetic foot dynamically over the gait cycle. The device described, prototyped and tested in this work, is a STF filled piston/cylinder design. The objective is a velocity dependent force response over the translational motion. Ranging from dampened, compliant deflection at low velocity, to a more efficient force transfer (coupling) for energy storage and return in the spring system, at higher speed. The rapid viscosity increase in the STF at a critical shear rate is used to approach a stepwise force response, thereby enabling adaptive response of the foot for different load rates. The adaptive response results in a greater range of motion with easier rollover for slow movement, for instance standing up from a seated position and adaptation to inclined surfaces, without sacrificing the energy return favorable for normal walking.

中文翻译：

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基于剪切增稠液流变学特性的变刚度假足

近年来，不连续剪切增稠液 (STF) 的独特流变特性已被用于各种工程应用。在商业方面，最引人注目的是防弹衣和防护设备，但也有专门用于阻尼和力耦合应用的智能结构。这项工作的主题是 STF 在关节式假足中的应用，以实现适应性力响应。与弹簧系统串联和并联连接，基于 STF 的元件可用于影响系统内的力传递，从而在步态周期内动态影响假足的刚度。在这项工作中描述、原型化和测试的设备是一种 STF 填充活塞/气缸设计。目标是平移运动上的速度相关力响应。从低速下的阻尼、柔顺偏转，到更有效的力传递（耦合），以在更高的速度下在弹簧系统中存储和返回能量。STF 在临界剪切速率下的快速粘度增加用于接近逐步的力响应，从而使脚能够对不同的负载速率进行自适应响应。自适应响应导致更大的运动范围，更容易翻滚缓慢移动，例如从坐姿站起来并适应倾斜的表面，而不会牺牲有利于正常行走的能量返回。STF 在临界剪切速率下的快速粘度增加用于接近逐步的力响应，从而使脚能够对不同的负载速率进行自适应响应。自适应响应导致更大的运动范围，更容易翻滚缓慢移动，例如从坐姿站起来并适应倾斜的表面，而不会牺牲有利于正常行走的能量返回。STF 在临界剪切速率下的快速粘度增加用于接近逐步的力响应，从而使脚能够对不同的负载速率进行自适应响应。自适应响应导致更大的运动范围，更容易翻滚缓慢移动，例如从坐姿站起来并适应倾斜的表面，而不会牺牲有利于正常行走的能量返回。