It is shown that a compound elastic structure, which displays a dynamic instability, may be designed as the union (or ‘fusion’) of two structures which are stable when separately analysed. The compound elastic structure has two degrees of freedom and is made up of a rigid rod connected with two springs to a smooth support, which evidences a jump in the curvature at the equilibrium configuration. Instability is proven in a linearized context and is related to the application of a non-conservative load of the follower type so that the instability disappears under dead loads. In the fully nonlinear range, the instability is also confirmed through numerical simulations. The obtained results may be useful in the design of new mechanical sensors, devices for energy harvesting, or architected materials. In addition, our findings have conceptual implications on piecewise-linear theories of mechanics such as for instance plasticity or frictional contact.

结果表明，显示动态不稳定性的复合弹性结构可以设计为两个结构的联合（或“融合”），这两个结构在单独分析时是稳定的。复合弹性结构具有两个自由度，由连接两个弹簧的刚性杆组成，以平滑支撑，证明了曲率的跳跃在平衡配置。不稳定性在线性化环境中得到证明，并且与从动类型的非保守负载的应用有关，因此不稳定性在恒载下消失。在完全非线性范围内，不稳定性也通过数值模拟得到证实。获得的结果可能有助于设计新的机械传感器、能量收集设备或建筑材料。此外，我们的发现对分段线性力学理论（例如塑性或摩擦接触）具有概念上的影响。