Applied Mechanics and Materials Vols. 395-396

Abstract: Through grinding experiment on mica glass ceramic, the mechanism of material removal was analysed, the fracture and removal of engineering ceramics was suitable for Griffiths fracture strength theory. And the factors of affected surface roughness were studied. The results indicated, The surface roughness was significantly affected by the grinding depth, inclining angle and deflecting angle in quick-point grinding engineer ceramics. The surface roughness value decreased with increasing of the wheel velocity, increased with increasing of the workpiece feed, decreased with increasing of grinding depth, increased with increasing of grinding wheel inclining angle and decreased with increasing of grinding wheel deflecting angle.

Abstract: ELID for SiC which enables the improvement of surface quality is put forward. ELID grinding technology is new technology of ultra-precision grinding, and the oxide film is formed on grinding wheel by electrolytic in-process technology, thus the wheel is in-process dressed. SiC material removal mechanism and ELID grinding mechanism is analyzed, the character and condition of brittle to ductile transition of SiC and surface formation mechanism of ductile mode grinding of SiC are studied, the results show that ELID grinding can realize ductile grinding ,this will lower the surface damage and improve the machining efficiency.

Abstract: First, quadratic regression general rotary combination experimental design is adopted in this paper. The cutting force prediction model based on tool rake angle and helix angle is established using regression analysis. And the proper cutter for milling Ti6Al4V is selected, rake angle = 12.5 °, helix angle = 34.5 °.Secondly, milling temperature during different milling process is simulated by the use of finite element simulation software. And the variation rule of milling temperature along with the rake angle and helix angle is obtained which provided the basis for the selecting tool.

Abstract: Chatter has been a problem in CNC machining process especially during machining thin-walled components with low stiffness. For accurately predicting chatter stability in machining Ti6Al4V thin-walled components, this paper establishes a chatter prediction method considering of cutting parameters and tool path. The fast chatter prediction method for thin-walled components is based on physical simulation software. Cutting parameters and tool path is achieved through the chatter stability lobes test and finite element simulation. Machining process is simulated by the physical simulation software using generated NC code. This proposed method transforms the NC physical simulation toward the practical methodology for the stability prediction over the multi-pocket structure milling.

Abstract: Large size optical aspheric lens is an important component in optical engineering. Aiming at the demand of precision processing for optical aspheric lens, this paper develops a precision grinding technique for large size optical aspheric lens. Based on precision surface grinding machine (MGK7160), grating-type parallel grinding method is put forward to realize grinding paths planning for optical aspheric lens. An on-machine measurement system is built to obtain surface measurement and evaluation after grinding. In order to ensure machining precision and efficiency, a diamond truer which self-developed is adopted to precision dress for arc diamond wheel. Finally, the experiment of precision grinding and error compensation validates machining accuracy for large size optical aspheric lens.

Abstract: The surface integrity of powder metallurgical high speed steel (S390) cut by wire electrical discharge machining (WEDM) has a great influence on the its fatigue life. In this paper, a study focused on surface integrity including white layer, surface finish, retained austenite, carbide and residual stress changed with multi-cutting has been described. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrograph (EDS) analysis were performed in the examination of the evolution of surface integrity. The experimental results reveal that the surface roughness, micro-cracks, white layer thickness and surface residual stress decrease with the increase of cutting pass, but the amount of retained austenite in the resolidified layer of the surface after the second cutting pass is the highest, compared with the other cutting passes. The content of carbides increases with the cutting pass and few carbides appear in the top section of the white layer of the first two cutting passes.

Abstract: This paper presents the experimental results of cutting force and surface roughness of 7050-T7451 aluminum alloy under the cutting speed of 3000~5000m/min. The cutting forces and surface roughness with different cutting parameters were analyzed. Experimental results suggested that increasing cutting speed would engender thermal softening, which would in return affect the cutting force and surface roughness in high speed milling. The cutting force and surface roughness were affected by cutting depth and feed rate obviously. Surface roughness was also affected by cutting width which changed the cutting force slightly. According to the results, proper parameters could be selected and thermodynamic relationship needed to be discussed for further research.

Abstract: This paper makes an experiment in high-speed milling of Inconel 718. Cutting tests were performed using round and ceramic tools, at feeds from 0.06 to 0.14 mm/tooth, Axial Depth of Cut from0.5 to 1.5mm,and cutting speeds ranging from 500 to 1037 m/min. The behaviour of the cutting forces during machining was then measure. The results show that cutting force increases first and then decreases with the increase of feed per tooth, the tool chipping and groove wear were found with the increase of axial cutting depth, and cutting force is increased; the increase in cutting force with the cutting speed increases, when the cutting speed reaches a critical speed, the cutting force as the cutting speed increases began to decline.

Abstract: This study aimed to investigate the effect of cutting speed, feed and depth of cut on the arithmetic mean surface roughness (Ra). The optimal cutting condition in dry turning brass with carbide cutting tool was also recommended. The experimentation was designed by using Taguchi Method (L₉). Three investigated factors with 3-level each were cutting speed (42, 68 and 110 m/min), feed (0.05, 0.1 and 0.15 mm/rev), and depth of cut (0.15, 0.25 and 0.5 mm). The results indicated that speed and feed were significantly affected at average surface roughness. The optimal cutting conditions were cutting speed at 68 m/min, feed at 0.05 mm/rev and depth of cut at 0.15 mm.

Abstract: To achieve ultra-precision machining efficiently, the tiny grinding wheel based on MR effect is used as a grinding tool. In this paper, the state of abrasive in cutting process was analyzed through modeling, and the grinding experiment was performed on the optical glass (K9). Study results show that, with the increasing of grinding time, the surface roughness of workpiece is reduced and tends to be uniform, but the material removal rate is reduced. The abrasive of tiny grinding wheel based on MR effect can automatically adjust its grinding pressure and depth of cut to improve the surface quality.