Materials Science Forum Vols. 800-801

Abstract: Machining induced residual stress is influenced by many factors. Extensive studies on the influence of cutting parameters, tool parameters, as well as basic properties of materials have been carried out during the past decades, while another important factor, initial stress distribution in workpiece, was often ignored. In this paper a relatively complete FEM simulation on the formation mechanism of machining induced residual stress in high speed machining is carried out, illustrating the three stress zones affected by mechanical and thermal loads, and their influence on ultimate residual stress. And the influence of initial compressive stress on stress formation and cutting forces is analyzed. Initial compressive stress weakens the tensile effect caused by the shear deformation, and the residual stress tend to be more compressive with larger initial compressive stress. Cutting force becomes larger with the increase of initial compressive stress. And the results in this FEM study can be used to explain some unaccounted experimental phenomena in former researches.

Abstract: The discrete element method (DEM) model which describes the friction and abrasion behavior of the interface between Sialon ceramic tool and superalloy chip in machining were established, effects of cutting speed and depth of cut on tool abrasion were numerically investigated. The abrasion behaviors of the Sialon ceramic tool mainly appear in terms of abrasive wear, fatigue wear, adhesion wear and diffusion wear. The DEM simulation results show that, within a certain range, the higher cutting speed effectively results in the slighter wear of Sialon ceramic tools, meanwhile the deeper depth of cut leads to more serious tool wear. It is further validated that discrete element method is feasible to simulate the tool wear behavior.

Abstract: A certain thickness of two, three and four layers of axisymmetric finite element bellows model were built by Abaqus firstly. Then the axial stiffness and stress and strain distribution of multi U-shaped bellows were simulated by finite element analysis. The results showed that in the case of a constant thickness, with the increase of the number of layers of the bellows, the stiffness of the bellows would be significantly reduced, and in the case of large deformation, the overall stiffness of the bellows would change significantly and was divided into elastic stiffness and plastic stiffness.

Abstract: This paper proposed an algorithm called “Revolution-Rotation” for two-dimensional irregular leather nesting based on heuristic search. The algorithm simplified the process of searching, constructing an evaluation system which evaluates by the center of gravity of the leather to meet the demands of actual requirement. The nesting test shows that the balance of material utilization and efficiency can be controlled by the adjustment of research parameter.

Abstract: To solve the problem of irregular leather nesting, a “Revolution-Rotation” algorithm is put forward on the base of heurism search in this paper. The system can be applied in nesting problem in both regular and irregular motherboard, and can achieve the balance of material utilization and nesting efficiency.

Abstract: The determination of the minimum uncut chip thickness is essential in micro machining in order to achieve desired surface integrity and accuracy. The parameters being considered in determination the minimum uncut chip thickness include the cutting tool geometry, workpiece material, cutting parameters and so on. In this paper, five different materials including OFHC Copper, Al 7050, AISI 4340, Ti-6Al-4V and IN 718 with unequal materials’ properties were investigated to find materials parameters’ effect on the minimum uncut chip thickness. An Arbitrary Lagrangian Eulerian (ALE)-based numerical modeling is proposed to determine the minimum uncut chip thickness for the five different materials by changing depth-of-cut. The Johnson-Cook (J-C) constitutive model is employed to describe the work material behavior. Results show that the flow stress of different materials has significant effect on the minimum uncut chip thickness.

Abstract: This paper adopts composite structure system analysis method to perform modal analysis of high-speed face milling cutter which is mounted on the machine tool through FEM modal analysis. The key problem of this method is to obtain joint surface parameters between the machine tool spindle and face milling cutter through experimental modal analysis and MATLAB software. The joint surface parameters consist of linear stiffness, linear damping, rotation stiffness and rotation damping. After getting the frequency response function (FRF) at the tool tip of the face milling system through experimental modal analysis, the contact surface parameters can be used to eliminate the influence of the machine tool to get modal parameters of the face-milling cutter itself. Based on the finite element model of face milling cutter, composite structure system analysis method can be used easily to acquire the dynamic performance of the face milling system through FEM modal analysis, greatly to improve the reliability of modal analysis, and is helpful to the dynamic design and the structure improvement of high speed face milling cutter.

Abstract: Capto shank is widely used in high speed machining, especially in Turning/Milling center. Some of shank’s dimensions exert a tremendous influence on its working performance. In order to find out these key dimensions, finite element method is used to analyze how the change of Capto C5 shank’s nine dimensions affects its radial stiffness. Some key dimensions which have great effects on Capto shank’s properties are found. The research results provide theoretical basis for manufacturing and measurement of Capto shank.

Abstract: The paper investigates the effects of cutting edge preparation on cutting force, cutting temperature and tool wear for hard turning. An optimized characterization approach is proposed and five kinds of cemented tools with different edge preparation are adopted in the simulations by DEFROM-2D^TM. The results show that both the forces and cutting temperature on the rake face climb up and then declines with the increasing of factor K (S_γ/S_α). While the temperature on flank face decrease with the increasing of the factor K. When the cutting conditions are identical, flank wear reduces while crater wear exacerbates before easing with the increasing of the factor K. The simulation results will provide valuable suggestions for optimization of cutting edge preparation for hard turning in order to obtain excellent machining quality and longer tool life.

Abstract: TiN-TiB₂ composite ceramic cutting tool material was prepared with hot pressed sintering in vacuum. The effects of sintering temperature and Ni additive on mechanical properties and microstructure were investigated. It is shown in the results that the fracture toughness decreases consistently with an increase of the sintering temperature, while the flexural strength of the TiN-TiB₂ composite increases firstly and then decreases with an increase of the sintering temperature. The flexural strength of the TiN-TiB₂ composite increases firstly and then decreases with an increase of the Ni additive, while the fracture toughness increases consistently with an increase of the Ni additive. The optimum comprehensive mechanical properties were obtained with the additive of 5wt.% Ni while sintered at 1650°C; the corresponding values were as follows: flexural strength of 966.1±190MPa, fracture toughness of 6.36± 0.9MPa·m^1/2 and hardness of 18.8±2.4GPa respectively.