Surface roughness is one of the main indexes in qua li ty assessment of machined components. Surface generation by material removal pro cess depends on the machining process mechanism. The material removal mechanisms are different for machining common materials and heterogeneous materials. Machi ned surface profiles of conventional engineering materials are determined by the moving tracks of tool edges on workpiece surface, the roughness mainly depends on the cutting parameters and the geometrical shape of cutting tool. Heterogeneo us materials consist of two or more separate materials, their properties vary fr om one phase to another and change along with measurement direction. When he terogeneous materials are cut, a quantity of machining-conduced imperfections o ccurs in the machined surface, part of the surface profiles do not directly result from the cutting of tool edges but from the imperfections, the surface te xture may confuse or disappears. The imperfections distribute randomly and their shapes are irregular, the spacing of profile peaks and valleys is irregular and un-periodical, therefore, they cannot be distinguished by wavelength. The prof iles of machined surface of heterogeneous materials have dense, narrow and sharp peaks and valleys. The amplitude distribution of profile peak and valley is dis persed and unsymmetrical, and usually the profile has a positive skewness. Ten p oint height of irregularities or root-mean-square deviation of the profile is more appropriate parameter than maximum height or arithmetical mean deviation of the profile for describing the height characteristics of roughness, and statist ical method and random process method are used to describe the irregularity distribution of the profile.
展开▼
