Papers by Author: Gang Liu

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Authors: Dong Jin Zhang, Chen Wang, Gang Liu, Ming Chen
Abstract: As a typical difficult-to-cut material, the nickel-based superalloy GH4169 has been used in many kinds of aeronautical key structures and turbine components because of its high yield stress and anti-fatigue performance even in high temperature. In this paper, finite element method (FEM) is introduced to study the saw-tooth chip formation in detail. By the way of Lagrange approach, adiabatic shear band (ASB) is simulated and the chip forming mechanism is interpreted by adiabatic shearing theory via the comparison of two models, one of which has a failure criterion and another not. The comprehensive comparison and analysis of chip morphology between simulation and experiment are also presented in this paper.
Authors: Gang Liu, Ming Chen
Abstract: The wrought nickel-based superalloy has been the indispensable material for aviation manufacturing industry, but it is also one of extremely difficult-to-cut materials. Now many researches were focused on the machinability of wrought nickel-based superalloy, and many useful and favorable results can be collected. But most of these researches studied on single kind of wrought nickel-based superalloy, the general and integrated study is absent. In this paper, six typical wrought nickel-based superalloys (GH80A, GH738, GH3030, GH3044, GH4033 and GH4169) were studied. By means of studies on tool wear rate, cutting forces, cutting vibration and tool wear mechanism, the comprehensive comparison of the machinability of wrought nickel-based superalloys was showed. The influences of major elements on the machinability were investigated. The machinability of the six kinds of wrought nickel-based superalloys queues from easiness to difficulty as follows: GH3030, GH3044, GH4033 and GH80A, GH4169, GH738. Finally the comprehensive comparisons of tool failure modes and wear mechanism of these wrought nickel-based superalloys were also presented. Experiment results are comprehensive and have great practical significance to the high efficient machining of wrought superalloys.
Authors: Wei Wei Ming, Gang Liu, Ming Chen
Abstract: The grind-hardening process integrates heat treatment processing into the production line, reduces the number of producing procedures, shortens machining period and lowers the cost. Meanwhile, grind-hardening machining doesn’t use cutting fluid. So the grind-hardening process is a green manufacturing method with an extending application in future. Grinding hardening is an effective method in machining SKD-11 hardened steel due to its good quenched property. In this paper, the grind-hardening characteristics of SKD-11 hardened steel are discussed, and the impacts on the hardened surface layer varying with the grinding parameters are also studied. Optimization of grinding parameters of SKD-11 hardened steel is conducted based on the study.
Authors: Kai Xue, Xiang Ming Xu, Gang Liu, Ming Chen
Abstract: The chip formation and morphology are definitely affected by tool geometry and cutting parameters such as cutting speed, feed rate, and depth of cutting. An experiment investigation was presented to study the influence of tool geometry on chip morphology, and to clarify the effect of different cutting parameters on chip deformation in orthogonal turning the wheel steel. The result obtained in this study showed that tool geometry affected the chip morphology significantly; cutting speed was the most contributive factor in forming saw-tooth chip.
Authors: Dong Jin Zhang, Gang Liu, X. Sun, Ming Chen
Abstract: The nickel-based superalloy GH4169 is a typical difficult-to-cut material, but it has been used in a good many kinds of aeronautical key structures because of its high yield stress and anti-fatigue performance at the temperature below 650°C. In this paper, finite element method (FEM) was introduced to study the saw-tooth chip forming process in detail when machining nickel-based superalloy GH4169. By the way of Lagrangian visco-elastic plastic approach, adiabatic shear band (ASB) was simulated in high speed machining condition by general commercial finite element code, and the mechanism of the adiabatic shearing phenomenon at primary shear zone was analyzed with the help of finite element analysis (FEA). The comprehensive comparisons of saw-tooth chip morphology under a wide range of cutting speed were also presented.
Authors: Lu Lu Jing, Gang Liu, Ming Chen
Abstract: In die and mold industry, there is a tendency to use milling in the finishing machining of dies and molds as an alternative to the traditional EDM process, consequently the surface integrity in milling is considered as one of the most important indices. In this study, surface roughness, micrograph of machined surface, surface microhardness, residual stress, and metallurgical texture of the surface layer were considered. The influence of geometrical characteristics of cutting tools and tool wear on surface integrity was studied. The results showed that hard milling of hardened die steel could yield a quite satisfied surface integrity by proper process; compressive residual stress was induced on machined surface, and the compressive stress induced in transversal direction was almost 3 times of that in longitudinal direction; tool wear had a significant negative influence on surface finish and caused the machined surface soften. These conclusions revealed the effects of tool conditions on surface integrity and would play a practical significance in the machining of hardened die steel.
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