Papers by Author: Ming Chen

Abstract: Reasonable tool condition has crucial importance to prevent tool malfunction such as abnormal wear, chipping and cutting teech breakage when broaching expensive components i.e. gas turbine engines disks. This paper proposes a broaching simulation test method of using customized single tooth groove tools with a variety of rake angle and clearance angle to simulate broaching processing at shaper machine under different cutting depth. The effects of tool condition and cutting depth on cutting forces, surface roughness analyzed by Response Surface Methodology and surface morphology of machined surface were discussed, which revealed that the changes of cutting depth play a dominate role in processing quality, followed by tool rake angle, and tool clearance is subordinate. Good tool edge strength should be assured from prevent shock and vibration during the selection of tool condition.

Abstract: Both aluminum alloy and titanium alloy have been widely used in aerospace, aviation, military and automotive industries. This research presents a study of modified drills for drilling aluminum alloy and titanium alloy. The modified drills can be expected to reduce the cutting forces and torque. A set of experiment was carried on to investigate the performance of the modified drills. A method to quantitative assess of the reduction of the thrust force and torque was given below, and the calculation shows that the modified drills can reduce the thrust force and the torque by as high as 21.16% and 90.48%, respectively, as compared to the conventional drills under the same conditions.

Abstract: Studying the dynamic properties of a material are an important method to understand the dynamic processes and deformation mechanism of material at different working conditions, particularly at high strain rate. The constitutive equation of a material has the highest significance to represent the mechanical properties, and is the principal research basis for the numerical simulation. In this paper, an important titanium alloy TC11 was studied through the quasi-static tensile test and the split Hopkinson pressure bar (SHPB) tests. Dynamic compressive behavior of TC11 alloy was discussed. Moreover, this paper gave the constitutive model of TC11 alloy and established the Johnson-Cook (J-C) constitutive equation.

Abstract: This paper investigates the surface integrity of premium thread gauge material 9Mn2V in reciprocating surface grinding using SG abrasive, which includes metallographic structure for grinding crack, specific grinding energy and surface residual stress. The specific grinding energy and the surface residual stress can be reduced after the workpiece gets tempered, so small grinding depth can lead to the generation of cracks when the workpiece is not tempered. Otherwise, the depth of heat affected zone increases with the increase of grinding depth, but not increases proportionally. After 9Mn2V is tempered, the occurrence of grinding burn and grinding cracks can be improved.

Abstract: Carbon fiber reinforced plastics (CFRP) has increasing applications in aerospace and other fields, due to low density, high strength, high stiffness, great resistance to corrosion, etc. Although, delamination damages in drilling holes for assembly influence the final characteristics of CFRP components. This paper presents an experimental investigation to analyze delamination damage, in which acoustic emission and thrust force are monitored during drilling CFRP laminates to clarify the relationship between AE signals and delamination damages. The results show that delamination damage has close correlation with thrust force and acoustic emission energy. AE root mean square (rms) is recommended to be selected as AE signal parameter. Abrupt peak feature of AE rms can be used as a dependable trigger for delamination monitoring. The number of abrupt pulses of AE rms can be counted online to predict the degree of delamination damages, based on which delaminations can be monitored and controlled online.

Abstract: The concept of multi-constrained analysis of the cutting process is presented for the first time in the paper. The paper adopts a method to solve an important problem which is how to judge the influence of constrains during the cutting process. The research results are applied for HSS drills for cutting stainless steel. On the basis of the multi-constrained analysis combined with methods of simulations and standard experiments, the optimum methods are provided for structure, coating and cutting parameters of cutting tools. For geometric structure of tools, optimization is to increase thickness of cutting and rake angle. Coating optimization strategy is choosing high temperature hardness and low thermal conductivity coating. Optimization of cutting parameter is to adjust feed fate, then select proper cutting speed. The conclusion of paper is helpful for the cutting optimization.

Abstract: External thread turning is a complex 3-D process in which the cutting conditions vary over the thread cutter profile. There are a lot of factors that affect the thread precision. This paper focuses on the influences of the lubrication method, cutting speed and the number of passes on the thread precision. Several stainless steel turning tests were conducted. The results showed that lubrication method was the most important factor that affected the thread precision, while the number of passes was the least important one. MQL (Minimum Quantity Lubrication) could reach the effect corresponding to wet cutting at specific cutting parameters and showed great potential to replace traditional lubrication method.

Abstract: Ultra-high-strength steel 30Cr3SiNiMoVA (30Cr3) which has excellent mechanical properties is usually used to manufacture the key parts in aviation industry. Precision hard milling is an efficiency way to machine 30Cr3 instead of grinding. Rounded cutting edge radius has important influence on the machining process due to small depth of cut. In order to better understanding the influence of rounded cutting edge radius, cutting forces, cutting temperature, critical depth of cut, etc., is analyzed by using finite element method (FEM). The results show that cutting forces in the y direction are more sensitively to the rounded cutting edge radii. Ploughing effect is also observed at the end of the climb milling process and it has significant influence on the quality of the machined surface. Simulation reveals that the increment of rounded cutting edge radius can lead to the increment of critical depth of cut correspondingly and the proportionality factor is about 14%.

Abstract: High-strength carbon fiber reinforced plastic (CFRP) T800S/250F is used as the large commercial aircraft material for manufacturing the main load-bearing structural components. Drilling is the mostly used in final machining process of CFRP laminates, while the delamination and burrs occur frequently at the drill exit in the CFRP laminate. In this paper, the machinability of T800S/250F was investigated in term of drilling force and hole quality by using a twist drill and a dagger drill. The experimental results indicated that high spindle speed and low feed rate favor the reduction of thrust force for both drill bits. High spindle speed is a preference to gain the good hole quality at drill exit especially for the dagger drill, which also shows excellent drilling performance than the twist drill and was more suitable for drilling of T800S/250F CFRP laminate.

Abstract: With the development of the coating technology, coated tools have been widely used in processing industries. Thread turning is one of its applications. The performance of coated thread inserts varies with the change of coating material, coating thickness, matrix material and tool structure. Two tungsten-cobalt type alloy matrix, TiAlN coated thread inserts with different coating thickness, rake face type had been employed to conduct the thread turning experiments. By analyzing the cutting forces, chip formation and tool wear, it was found that insert with coating thickness of 4.35 μm would result in less tool wear under MQL condition, smaller cutting force, better chip morphology under dry condition compared with insert with coating thickness of 2.38 μm.