Design and analysis of passive variable stiffness device based on shear stiffening gel

Abstract Shear thickening materials are utilized as the core of variable stiffness devices in various engineering applications in recent years. However, due to the used materials being liquid, most of these devices are suffered from the problem of liquid leakage and coagulation. To address this issue, this paper proposes a design method of a passive variable stiffness device (pVSD) based on shear stiffening gel (SSG), which integrates the core SSG and spring into a compact structure to obtain well stability. The used SSG can affect the force transfer within the device, thereby influencing the system's stiffness dynamically over the external impact load. Due to the core SSG being good shear thickening properties, the device is highly sensitive to frequency and shows variable stiffness characteristics. When the frequency of external load increased from 0.1Hz to 5Hz, the equivalent stiffness of the device could be increased by 105.74%. An equivalent nonlinear model is used to represent the overall stiffness of the device as a function of the frequency and displacement amplitude of the load. The output of the equivalent nonlinear model agrees well with the experimental data. The cross-validation also proves the accuracy of the model fitting, which provides a quantitative description of the dynamic performance of the variable stiffness device. By combining different types of SSGs and springs with different stiffness, the design principle of the variable stiffness device proposed in this paper can be utilized in various impact-loading applications, such as designing the lower limb prosthetic joints and vehicle suspension systems. The work of this paper has guiding significance for the design of adaptive variable stiffness devices.