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.

中文翻译：

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强行解决问题：测试受壁虎启发的粘合剂

传统上通过施加受控位移并测量相应的力或施加受控力来测试材料。这些方法中的第一种更常见，因为它可以直接控制刚性装置的位移，并且如果材料突然失效，几乎不会释放能量。然而，在测试受壁虎启发的粘合剂时，施加的力范式更接近于粘合剂在实践中的加载方式。此外，我们证明了受控位移范式会导致假设行为中的伪影，除非施加的加载轨迹与应用中可能发生的偏转精确匹配。我们提出了用于测试定向壁虎式粘合剂的受控力系统和协议的设计，并表明在某些情况下获得的结果与受控位移测试的结果大不相同。受控力测试方法的一个优点是它允许准确生成粘合极限曲线，而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。