Suresh Srinivasan A, Hajj-Ahmad Amar, Hawkes Elliot W, Cutkosky Mark R
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA.
Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106, USA.
J R Soc Interface. 2021 Jan;18(174):20200730. doi: 10.1098/rsif.2020.0730. Epub 2021 Jan 13.
Materials are traditionally tested either by imposing controlled displacements and measuring the corresponding forces, or by imposing controlled forces. The first of these approaches is more common because it is straightforward to control the displacements of a stiff apparatus and, if the material suddenly fails, little energy is released. However, when testing gecko-inspired adhesives, an applied force paradigm is closer to how the adhesives are loaded in practice. Moreover, we demonstrate that the controlled displacement paradigm can lead to artefacts in the assumed behaviour unless the imposed loading trajectory precisely matches the deflections that would occur in applications. We present the design of a controlled-force system and protocol for testing directional gecko-inspired adhesives and show that results obtained with it are in some cases substantially different from those with controlled-displacement testing. An advantage of the controlled-force testing approach is that it allows accurate generation of adhesive limit curves without prior knowledge of the expected behaviour of the material or the loading details associated with practical applications.
传统上，材料测试要么是通过施加受控位移并测量相应的力，要么是通过施加受控力来进行。前一种方法更为常见，因为控制刚性仪器的位移很直接，而且如果材料突然失效，释放的能量很少。然而，在测试受壁虎启发的粘合剂时，施加力的模式更接近粘合剂在实际中的加载方式。此外，我们证明，除非施加的加载轨迹与实际应用中会出现的挠度精确匹配，否则受控位移模式可能会导致假定行为出现假象。我们展示了一种用于测试定向受壁虎启发粘合剂的控制力系统和测试方案的设计，并表明用该系统获得的结果在某些情况下与受控位移测试的结果有很大不同。控制力测试方法的一个优点是，它无需事先了解材料的预期行为或与实际应用相关的加载细节，就能准确生成粘合剂极限曲线。
