近日，博士生严洁以第一作者在JCR力学一区期刊“Mechanics of Materials”第112卷（2017）上发表题为“On the receding contact between an inhomogeneously coated elastic layer and a homogeneous half-plane”的研究论文，谨致热烈祝贺！论文官方网页和简要内容如下。
论文官方网页：
Highlights
Receding contact between a coated layer and a halfplane is semianalytically solved.
A hard and thick coating can effectively reduce receding contact pressure.
A soft halfplane substrate also helps to alleviate the receding contact pressure.
Contact stress is inversely proportional to contact area at either contact surface.
Large indentation loads result in both large contact pressures and contact area.
Abstract:
The general double contact problem of an inhomogeneously coated elastic layer indented against a homogeneous half-plane by a rigid punch is investigated. The problem is solved under the assumptions that the contact at both interfaces is frictionless, the three materials possess different shear modulus, and the shear modulus of the functionally graded coating varies exponentially. By the standard method of Fourier integral transforms, the problem is reduced to a system of singular integral equations, which are subsequently transformed into algebraic ones by Gauss–Chebyshev integration formulas. Massive numerical experiments are performed to quantify the influence of stiffness distribution in coating, material and geometric properties of the compound structure, and indentation load on the contact pressure and contact length at both surfaces of contact. The results suggest that in the case of a hard and thick coating large pressure reduction can be achieved for the receding contact at the layer/substrate interface.
Keywords:
Receding contact; Functionally graded coating; Singular integral equation; Rigid punch; Contact pressure
Conclusions:
In this paper, we analyzed in detail the frictionless indentation problem of an elastic structure composed of a coated elastic layer and an elastic half-plane substrate. Both the elastic layer and the half-plane substrate are assumed to be homogeneous continua, whilst the coating is treated as functionally graded material with exponentially varying stiffness. The classical method of Fourier integral transform was implemented to address the double contact problem. We focused our attention on the contact length and pressure at both contact surfaces. Systematic numerical analysis on two rigid punches with circular and parabolic profiles led to the following observations and conclusions:
A hard and thick coating tends to most effectively reduce the receding contact pressure at the interface between the elastic layer and the half-plane substrate. The cost of this reduction is the presence of high advancing contact stress at the indenter/coating interface.
A soft half-plane substrate also helps to alleviate the receding contact pressure. We have thus traded the advancing contact for the receding contact. This will be an advantageous trade-off, provided that receding contact damage is of top priority.
Force equilibrium conditions at both surfaces of contact dictate the inverse proportionality between contact stress and contact length.
In any scenario, large indentation loads result in both large contact stress and contact size, for both the advancing and receding contact.
The solution algorithm presented in this paper was specifically tailored for functionally graded coating with exponentially varying properties. Other property distributions, e.g. power and linear functions, require the reformulation of the solution procedure and could be future lines of research. The examination of possible preference of the FGM coating to the receding contact surface could also be an extension to the present work.
