Abstract. Th e objective of the article is to scientifi cally evaluate supply chain reliability (SCR). We argue that this problem relates to two aspects -the cognition and expression of SCR. Th e paper considers SCR as a unifi cation of a fuzzy and random meaning in a dynamic environment. Furthermore, intrinsic relationship between the theoretical foundation of SCR evaluation and the cloud theory is discovered, accordingly to which, the cloud theory is applied to study the evaluation of SCR from a holistic perspective. According to the comprehensive invalidation degree of a supply chain, SCR is diff erentiated as six grades and the infl uencing factors of SCR are classifi ed taking into account fi ve aspects. A comprehensive performance model is developed to measure fi ve aspects of infl uencing factors and to evaluate the exact class SCR belongs to. As we know, the cognition of SCR depends on human mind while the natural language is an appropriate medium to express human mind. Th erefore, linguistic terms are adopted to express uncertain transformation between qualitative concepts and their corresponding quantitative values. Th is method is further demonstrated using a numerical example.
In order to overcome the defects of conventional magnetorheological finishing (MRF) processes that are unable to finish small curvature radius concave surfaces of diameter within 10 mm, a novel precision MRF process using small ball-end permanent-magnet polishing head with a diameter of 4 mm is proposed in this paper. And experimental setup of a four-axis linkage MRF machine tool is fabricated. Magnetostatic simulation of the distribution of magnetic flux density indicates that the magnetic field uniformity of produced polishing head is 93.3 %. Magnetizing force analysis is done to analyze the formation of magnetorheological fluid in finishing region. In addition, the suitable range of C-axis angular position for finishing is generated to be 60°~70°. Finishing experiments on both nonmetallic and metallic specimens with different surface shapes have been conducted. The ability of the developed method of finishing process to improve surface characteristics of a workpiece is demonstrated to reach the surface roughness of finished surfaces below Ra 6 nm. It confirms that the present MRF process is capable of improving surface quality and performing the nanofinishing on small curvature radius concave surfaces.
In order to achieve the deterministic finishing of optical components with concave surfaces of a curvature radius less than 10 mm, a novel magnetorheological finishing (MRF) process using a small ball-end permanent-magnet polishing head with a diameter of 4 mm is introduced. The characteristics of material removal in the proposed MRF process are studied. The model of the material removal function for the proposed MRF process is established based on the three-dimensional hydrodynamics analysis and Preston's equation. The shear stress on the workpiece surface is calculated by means of resolving the presented mathematical model using a numerical solution method. The analysis result reveals that the material removal in the proposed MRF process shows a positive dependence on shear stress. Experimental research is conducted to investigate the effect of processing parameters on the material removal rate and improve the surface accuracy of a typical rotational symmetrical optical component. The experimental results show that the surface accuracy of the finished component of K9 glass material has been improved to 0.14 μm (PV) from the initial 0.8 μm (PV), and the finished surface roughness Ra is 0.0024 μm. It indicates that the proposed MRF process can be used to achieve the deterministic removal of surface material and perform the nanofinishing of small curvature radius concave surfaces.
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