Depending on processing technologies and working conditions, imperfect bonding at the layer-substrate interface may occur, resulting in diverse mechanical responses compared to a perfectly bonded layer-substrate system. This study focuses on an imperfect interface under force-like conditions and incorporates it into a nanoscale adhesive contact model to explore the influences of interfacial imperfection on the adhesive contact behaviors of the layered medium. The adhesive contact model is formulated based on the Lennard-Jones (LJ) potential and the Hammaker summation method. The adhesive contact problem is addressed by solving the nonlinear surface gap equations between the contact bodies. The deformation within the gap equations, accounting for the influence of imperfections, is computed using the fast Fourier transform (FFT) algorithm. This study explores the influence of three stress jumping coefficients t1, t2 and t3, which quantitatively characterize the interfacial imperfection, and their coeffects with material parameters, including imperfection depth (layer thickness), adhesion work, and elastic modulus, on the adhesive contact behaviors of the layered medium. The findings underscore that the normal stress jumping coefficient t3 exerts the most significant impact, wherein a higher t3 value corresponds to a smaller adhesive force and a larger absolute contact approach, while tangential stress jumping coefficients t1 and t2 exhibit negligible influence. Decreasing t3 values correspond to varying interaction force-contact approach responses and contribute to alleviating contact stability in cases with large Tabor parameters. Interfacial imperfections manifest their influence by modifying the pressure-displacement response, with noticeable effects only within a specific imperfection depth range h¯<40. While the introduction of interfacial imperfections does not alter the fundamental impact of material parameters—such as imperfection depth, adhesion work ratios, and elastic modulus ratios—on adhesive force and contact approach, it does modify the magnitude of these effects. Furthermore, imperfections alter stress distribution, increasing maximal von Mises stress and causing stress concentration within the layer and at the interface. In summary, force-like imperfections reduce surface displacement, resulting in a smaller region of positive pressure and ultimately contributing to a larger adhesive force. However, this effect is accompanied by increased stress concentration at the imperfect interface. This heightened stress level poses a potential risk to the system's reliability.

中文翻译：

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界面缺陷对层状介质纳米级胶粘剂接触的影响


根据加工技术和工作条件，层-基板界面处可能会出现不完美键合，与完美键合的层-基板系统相比，会导致不同的机械响应。本研究侧重于类似力条件下的不完美界面，并将其纳入纳米级胶粘剂接触模型，以探索界面缺陷对层状介质胶粘剂接触行为的影响。胶粘剂接触模型是根据 Lennard-Jones （LJ） 电位和 Hammaker 求和方法制定的。通过求解接触体之间的非线性表面间隙方程来解决粘附接触问题。考虑到缺陷的影响，间隙方程中的变形使用快速傅里叶变换 （FFT） 算法计算。本研究探讨了三个应力跳跃系数 t1、t2 和 t3 的影响，它们定量表征了界面缺陷，以及它们与材料参数的相互作用，包括缺陷深度（层厚度）、粘附功和弹性模量，对层状介质的胶粘剂接触行为。研究结果强调，法向应力跳跃系数 t3 产生的影响最显着，其中较高的 t3 值对应于较小的粘附力和较大的绝对接触方法，而切向应力跳跃系数 t1 和 t2 的影响可以忽略不计。减小的 t3 值对应于不同的相互作用力-接触接近响应，并有助于在具有较大 Tabor 参数的情况下减轻接触稳定性。 界面缺陷通过改变压力-位移响应来体现其影响，仅在特定的缺陷深度范围 h ̄<40 内产生明显影响。虽然界面缺陷的引入不会改变材料参数（如缺陷深度、粘附功比和弹性模量比）对粘附力和接触方法的根本影响，但它确实改变了这些影响的大小。此外，缺陷会改变应力分布，增加最大 von Mises 应力，并导致应力集中在层内和界面处。总之，类似力的缺陷减少了表面位移，从而产生了更小的正压区域，并最终导致了更大的粘附力。然而，这种效应伴随着不完美界面处应力集中的增加。这种升高的应力水平对系统的可靠性构成了潜在风险。