IEEE Trans Haptics. 2022 Jan-Mar;15(1):32-38. doi: 10.1109/TOH.2021.3138640. Epub 2022 Mar 18.
The judgment of elastic softness is determined not only by mechanical parameters related to hardness, such as the elastic modulus and stiffness, but also by macroscopic surface features. This study experimentally demonstrates that objects with a finger-sized concave with a depth of 1-3 mm feel softer than flat surfaces made of the same materials when they are pushed by a finger. In Experiment 1, participants judged the surfaces of a rigid material with thumb-sized concaves to be softer than the flat and convex surfaces. Experiment 2 used rubbers of various elastic moduli, and the softness of a concave object with a Young's modulus of 0.55 MPa was subjectively equal to that of a flat object with an average Young's modulus of 0.23 MPa. Furthermore, the softness of a convex object was subjectively equal to that of a 1.68 MPa flat object. The contact phenomena between a finger pad and concave or convex objects are different from those between a finger pad and flat objects, and they influence the softness judgment. Such phenomena include the relationship between the pressing force and contact area. These results provide insights into surface design and improve comprehension of the perceptual principles of softness.
弹性柔软度的判断不仅取决于与硬度相关的机械参数，如弹性模量和刚度，还取决于宏观表面特征。本研究通过实验证明，当手指推动具有 1-3mm 深度的手指大小的凹面的物体时，其感觉比由相同材料制成的平面更柔软。在实验 1 中，参与者判断具有拇指大小凹面的刚性材料的表面比平面和凸面更柔软。实验 2 使用了各种弹性模量的橡胶，具有 0.55MPa 杨氏模量的凹面物体的柔软度主观上与平均杨氏模量为 0.23MPa 的平面物体相同。此外，凸面物体的柔软度主观上与 1.68MPa 的平面物体相同。指垫与凹面或凸面物体之间的接触现象与指垫和平坦物体之间的接触现象不同，它们影响柔软度的判断。这些现象包括压力和接触面积之间的关系。这些结果为表面设计提供了启示，并提高了对柔软度感知原理的理解。
