Advanced Materials Research Vol. 500

Abstract: AISI 12L14 as a typical free-cutting steel has been widely employed in machinery, energy and metallurgy fields due to its excellent machinability. This research was concerned with the experimental investigation on high-speed turning of AISI 12L14 in terms of cutting force and tool wear with multi-layer (Al₂O₃/TiCN) CVD coated carbide tool. Results showed that: Depth of cut a_p had the dominant effect on the main cutting force, and feed rate f followed. Increase of cutting speed v_c was observed to decrease the turning forces. Optimal factor level combination (v_c=500m/min, f=0.05mm/r and a_p=0.5mm) was obtained through the method of extremum difference analysis. The cutting tool was observed to form sulfide lubricant zone along its rake and flank faces. Ascribed to the presence of sulfide lubricant zone the tool can obtain excellent protection and minor flank wear in the entire turning process. Crater wear was observed occurring on tool rake face and no BUE was found along the cutting edge. In addition, tool flank face suffered abrasive wear and adhesive wear.

Abstract: Based on the 3D finite element simulation software DEFORM-3D V6.1, the cutting process of three kinds of typical hard processing materials (titanium alloy, nickel alloy, stainless steel materials) were simulated. Main cutting force and cutting temperature of above materials were observed at different cutting parameters and cutting performance was studied. Results show that: under the same conditions, the main cutting force of nickel alloy IN718 was maximum, followed by TI-6AL-4V titanium alloy, stainless steel AISI-316h was minimum; the cutting temperature of nickel alloy IN718 was the highest, followed by TI-6AL-4V titanium alloy, stainless steel AISI-316h was minimum.

Abstract: Basing the foundation on the cutting experiments of 2.25Cr-1Mo-0.25V steel which is the material of hydrogenated cylindrical shell, the dynamic mechanical characteristics of the excessively heavy-duty cutting were analyzed. Then through researching the influence that the dynamic mechanical characteristics had on tools failure in limited heavy-duty cutting process, and the model of dynamic shearing force in cutting area was established. However, the experimental results showed that the dynamic shear-flowing-stress in cutting area had great influence on tools fatigue, and the mainly damaged form of the heavy-duty cutting tool was shearing fracture. Analyzing the theory comprehensively, the critical condition of tools fracture which was under the terms of extreme loading had been established finally.

Abstract: An alternative physical explanation for process damping where a distributed cutting force model, along with a function distribution over the tool-chip interface, is assumed, is described. An exponential shape function is used to approximate the force distribution on the tool-chip interface. The distributed force model results in a more complicated governing equation, a second-order delayed integrodifferential equation, which involves both a discrete and distributed delay. An approach to transform and normalize the governing equation of motion into a third-order discrete system is described and the state-space representation of the new system is obtained. The semi-discretization method is then used to chart the stability boundaries for turning operation.

Abstract: In the PCB micro drilling, because the force signal is tiny, and when the micro-drill drill to a certain degree of multilayer PCB, alternate force signals will not appear obvious, through to the drilling force signal analysis, we can know the drill bit position and the materials to the influence of the drill failure, so the drilling force signals denoise seems extremely important. In the processing of the non-stationary signal, traditional signal processing method has a certain extent of insufficient, using the wavelet packet decomposition signal, the white noise variance and amplitude decrease with the increase of wavelet scales, but the signal variance and amplitude has nothing to do with the wavelet transform. According to the view of the signal energy, first of all, we make the multiscale decomposition of the signal, then, by using some of the wavelet packet that has efficient energy to reconstruct the original signal. Comparing with the traditional threshold denoising ,using this method in the test signal to deal with the noise can effectively eliminate the white noise interference, and has good denoising effects besides the simple calculation.

Abstract: 7CrSiMnMoV (HRC65) hardened steel mold was cutted to investigate the effects of cutting parameters (cutting speed, feed speed, radial cutting depth, axial cutting depth) on cutting force and cutting temperature. Cutting was done with the ball-mill tool coating with TiAlN and without coolant with a high-speed. The aim of this study is putting forward the principle of reasonable choice of cutting parameters and optimizing cutting parameters.

Abstract: Powder metallurgy (PM) nickel-based superalloy is regarded as one of the most important aerospace industry materials, which has been widely used in advanced turbo-engines. This paper presents an experimental study of high speed milling of powder metallurgy nickel-based superalloy with PVD (TiAlN-TiN) coated carbide tools. Experimental measurements of milling temperature and milling force were performed. Then the surface roughness and tool wear were analyzed and discussed under dry machining conditions. The results might be helpful to guiding the selection and design of tool materials and control of tool wear in high speed milling PM nickel-based superalloy.

Abstract: This study presents experimental results of machined surface integrity of die material (AISI D2 hardened steel) when hot machining (induction heating) assisted end milling using coated carbide is applied. The aim of this work was to study the influence of induction heating temperature, cutting speed, and feed on the effects induced by hard milling on surface integrity (microhardness and work-hardening). Microhardness was measured to observe the distribution of the hardness beneath the surface and to determine the effect of induction heating on the micro-hardness distribution and work-hardening phenomena. The behaviour of microhardness induced in the subsurface region when end milling under room and induction heating cutting conditions using coated carbide inserts was also investigated. The surface integrity and subsurface alteration have been investigated by employing scanning electron microscope (SEM) and Vickers microhardness tester.

Abstract: nconel 718 is a typical difficult-to-machine material, and its high speed end milling process has wide applications in manufacturing parts for aerospace and power industry. Surface integrity of these parts greatly influences the final characteristics. This paper presents an experimental investigation to evaluate surface integrity behaviors of Inconel 718 with finishing cutting parameters in terms of surface topography, surface roughness Ra, residual stresses and subsurface microstructure and microhardness. The results show that high cutting speed is advisable to get better surface topography and roughness. Residual stresses and subsurface microhardness barely increase after 80m/min. Microstructure in surface layer has only slight deformation after high speed milling.