Interfacial Mechanics Analysis of a Brittle Coating–Ductile Substrate System Involved in Thermoelastic Contact
In this paper, interfacial stress analysis for a brittle coating/ductile substrate system, which is involved in a sliding contact with a rigid ball, is presented. By combining interface mechanics theory and the image point method, stress and displacement responses within a coated material for normal load, tangential load, and thermal load are obtained; further, the Green’s functions are established. The effects of coating thickness, friction coefficient, and a coating’s thermoelastic properties on the interfacial shear stress, τxz, and transverse stress, σxx, distributions are discussed in detail. A phenomenon, where interfacial shear stress tends to be relieved by frictional heating, is found in the case of a coating material’s thermal expansion coefficient being less than a substrate material’s thermal expansion coefficient. Additionally, numerical results show that distribution of interfacial stress can be altered and, therefore, interfacial damage can be modified by adjusting a coating’s structural parameters and thermoelastic properties.
Study on the coated isotropic thermoelastic material based on the three-dimensional Green’s function for a point heat source
Abstract Three-dimensional Green׳s function for a point heat source acting on the surface of a coated isotropic thermoelastic material is investigated in this paper to improve our understanding about the interface mechanisms of coating/substrate system. Based on the general solution of isotropic thermoelastic materials expressed by harmonic functions, the corresponding harmonic functions with undetermined constants for coating layer and semi-infinite substrate are constructed by the trial-and-error method, respectively. The thermoelastic field can be obtained by substituting the harmonic functions into the general solution. The constants can be determined by the boundary conditions of the surface and the continuous conditions of the interface between the coating layer with the semi-infinite substrate. Numerical results are exhibited in form of contours and some valuable conclusions for interface effect, interface debonding and stress field distortion are presented.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.