临界载荷粘弹性击倒引起的球壳延迟屈曲
Delayed buckling of spherical shells due to viscoelastic knockdown of the critical load
摘要：
我们进行了动态压力屈曲实验缺陷种子球壳制成的一种常见的硅橡胶。与准静态实验不同的是，壳体在表面上亚临界的压力下（即低于弹性屈曲发生的实验确定的载荷）屈曲，通常伴随着显著的时间延迟。在强调与弹性壳屈曲的密切联系的同时，我们依靠粘弹性来解释我们的观察结果。特别是，我们证明，较低的临界载荷可以确定的材料性能，这是合理的一个简单的类比弹性球壳屈曲。然后，我们介绍了一个模型为中心的经验量表明，粘弹性蠕变变形降低临界载荷在同一个可预测的，可量化的方式，一个不断增长的缺陷将在弹性壳。这使我们能够捕获临界偏转和延迟时间如何取决于所施加的压力、材料特性和缺陷几何形状。这些量在实验中很容易测量。因此，我们的工作不仅提供了直观的粘弹性行为从弹性壳屈曲的角度来看，但也提供了一个可访问的途径，引入可调的，时间控制的驱动现有的机械致动器，例如气动夹具。
英文摘要：
We performed dynamic pressure buckling experiments on defect-seeded spherical shells made of a common silicone elastomer. Unlike in quasi-static experiments, shells buckled at ostensibly subcritical pressures (i.e. below the experimentally-determined load at which buckling occurs elastically), often following a significant time delay. While emphasizing the close connections to elastic shell buckling, we rely on viscoelasticity to explain our observations. In particular, we demonstrate that the lower critical load may be determined from the material properties, which is rationalized by a simple analogy to elastic spherical shell buckling. We then introduce a model centered on empirical quantities to show that viscoelastic creep deformation lowers the critical load in the same predictable, quantifiable way that a growing defect would in an elastic shell. This allows us to capture how both the critical deflection and the delay time depend on the applied pressure, material properties, and defect geometry. These quantities are straightforward to measure in experiments. Thus, our work not only provides intuition for viscoelastic behavior from an elastic shell buckling perspective, but also offers an accessible pathway to introduce tunable, time-controlled actuation to existing mechanical actuators, e.g. pneumatic grippers.
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