非圆形软质黏着接触中的接触形成与黏弹性脱离
Contact Formation and Viscoelastic Detachment in Non-Circular Soft Adhesive Contacts
AI总结：
本文通过PDMS交叉圆柱实验，研究非圆形软质黏着接触的形成与脱离，发现接触形成遵循面积等效缩放，脱离受几何和历史依赖的耗散分离支配，建立了可描述卸载响应的黏弹性模型。
AI中文摘要：
软质聚合物的黏着接触测量通常采用针对圆形接触的Johnson-Kendall-Roberts（JKR）理论进行解释。本文通过聚二甲基硅氧烷（PDMS）交叉圆柱实验，研究非圆形软质黏着接触中的接触形成与脱离过程。交叉角在30°至90°范围内变化，在保持材料对固定的同时，使接触区域从高度拉长的椭圆过渡到接近圆形的几何形状。加载过程中，接触的纵横比b/a迅速趋近于与角度相关的平台值，表明接触呈现近似自相似生长，这促使我们采用面积等效半径c=√(a*b)和几何平均曲率半径Reff=√(R1*R2)。加载分支遵循JKR型线性化，得到几乎与角度和预载荷无关的黏着功W_load=24 mJ/m²，Johnson-Greenwood椭圆接触拟合给出了可比的数值。相反，卸载和脱附过程具有强烈的历史依赖性：卸载分支需要显著更大的有效分离能W_unload,eff，该能量随预载荷增加和交叉角减小而增大。基于相同面积等效描述的简化黏弹性模型，利用跨角度和预载荷的单一共享参数集，可捕捉50°至80°范围内的主要卸载响应。这些结果表明，接触形成主要由面积等效缩放规律支配，而脱离则由与几何形状和历史相关的耗散分离过程支配。
英文摘要：
Adhesive contact measurements on soft polymers are commonly interpreted using Johnson-Kendall-Roberts (JKR) theory, which is formulated for circular contacts. Here, we examine contact formation and detachment in non-circular soft adhesive contacts using PDMS crossed-cylinder experiments. The crossing angle was varied from 30 to 90 degrees, producing contacts from highly elongated ellipses to nearly circular geometries while keeping the material pair fixed. During loading, the contact aspect ratio b/a rapidly approached an angle-dependent plateau, indicating approximately self-similar growth. This motivates use of the area-equivalent radius c=sqrt(a*b) and geometric-mean curvature radius Reff=sqrt(R1*R2). The loading branches follow a JKR-type linearization and yield a nearly angle- and preload-independent work of adhesion, W_load=24 mJ/m^2. Johnson-Greenwood elliptical-contact fits give comparable values. In contrast, unloading and pull-off are strongly history dependent. The unloading branches require a substantially larger effective separation energy, W_unload,eff, which increases with preload and decreasing crossing angle. A reduced viscoelastic model based on the same area-equivalent description captures the principal unloading response over 50-80 degrees using a single shared parameter set across angles and preloads. These results show that contact formation is governed primarily by area-equivalent scaling, whereas detachment is governed by geometry- and history-dependent dissipative separation.
