Analytical Predictive Modeling of Serrated Chip Formation in High Speed Machining of 7075-T6 Aluminum Alloy

2004 ◽  
Author(s):  
Ning Fang ◽  
Juhchin Yang ◽  
Nan Liu
Keyword(s):  
Aluminum Alloy ◽  
Chip Formation ◽  
High Speed ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Shear Plane ◽  
Tool Geometry ◽  
High Speed Machining ◽  
Serrated Chip ◽  
Serrated Chip Formation

High speed machining has received increasingly broad applications in various industries, especially in the aircraft and aerospace industry, where a large number of structural frames are machined. Based on Manyindo and Oxley’s descriptive model of serrated chip formation, this paper proposes a new mathematical model for high speed machining of 7075-T6 aluminum alloy. The new model integrates Johnson-Cook’s material model with Oxley’s machining theory and is validated by using the published experimental data. A good agreement between the predicted and experimental degree of chip segmentation is reached. The effects of cutting conditions and tool geometry on the serrated chip geometry, the cutting forces, and the shear-plane angles are quantitatively investigated. The analysis shows that a large undeformed chip thickness, a negative tool rake angle, and a high cutting speed strengthen the degree of chip segmentation in high speed machining.

Research on Adiabatic Shear during Serrated Chip Formation of High Speed Turning of Hardened Steel

2010 ◽  
Vol 139-141 ◽  
pp. 743-747
Author(s):  
Chun Zheng Duan ◽  
Hai Yang Yu ◽  
Min Jie Wang ◽  
Bing Yan ◽  
Yu Jun Cai
Keyword(s):  
Chip Formation ◽  
Cutting Forces ◽  
High Speed ◽  
Cutting Speed ◽  
Chip Morphology ◽  
Rake Angle ◽  
Adiabatic Shear ◽  
Cutting Condition ◽  
Serrated Chip ◽  
Serrated Chip Formation

The development of chip morphology, critical cutting condition of adiabatic shear during serrated chip formation and cutting forces were observed and measured by high speed turning experiment for 30CrNi3MoV hardened steel. Results show that the cutting speed and rake angle are leading factors to influence chip morphology and cutting forces. With the increase of cutting speed, the continuous band chip transforms into serrated chip at a certain critical value. As the rake angle is changed from positive to negative, the critical cutting speed of adiabatic shear significantly decreases, the cutting forces abruptly reduces when the serrated chip forms. The results from predicting critical cutting speed using the critical cutting condition criterion of adiabatic shear in metal cutting process show that the leading reason of serrated chip formation is that the adiabatic shear fracture repeatedly occurs in the primary shear zone.

Theoretical Analysis of Serrated Chip Formation Based on Ideal Models in High Speed Cutting

2010 ◽  
Vol 154-155 ◽  
pp. 239-245
Author(s):  
Chong Yang Gao ◽  
Bin Fang ◽  
Yuan Tong Gu
Keyword(s):  
Chip Formation ◽  
High Speed ◽  
Engineering Application ◽  
Chip Thickness ◽  
Chip Morphology ◽  
Formation Model ◽  
Serrated Chip ◽  
Serrated Chip Formation ◽  
Serrated Chips ◽  
The Ideal

In this paper, two ideal formation models of serrated chips, the symmetric formation model and the unilateral right-angle formation model, have been established for the first time. Based on the ideal models and related adiabatic shear theory of serrated chip formation, the theoretical relationship among average tooth pitch, average tooth height and chip thickness are obtained. Further, the theoretical relation of the passivation coefficient of chip’s sawtooth and the chip thickness compression ratio is deduced as well. The comparison between these theoretical prediction curves and experimental data shows good agreement, which well validates the robustness of the ideal chip formation models and the correctness of the theoretical deducing analysis. The proposed ideal models may have provided a simple but effective theoretical basis for succeeding research on serrated chip morphology. Finally, the influences of most principal cutting factors on serrated chip formation are discussed on the basis of a series of finite element simulation results for practical advices of controlling serrated chips in engineering application.

Chip Formation Characteristics in High-Speed Machining of Hardened AISI1045 Steel

2012 ◽  
Vol 565 ◽  
pp. 484-489
Author(s):  
Bing Wang ◽  
Zhan Qiang Liu ◽  
Qi Biao Yang
Keyword(s):  
Shear Band ◽  
Chip Formation ◽  
High Speed ◽  
Adiabatic Shear Band ◽  
Cutting Speed ◽  
Adiabatic Shear ◽  
High Speed Machining ◽  
Micro Hardness ◽  
Serrated Chip ◽  
Aisi1045 Steel

Analyzing mechanism of the chip formation is a significant way to understand the metal cutting process better. The characterization of serrated chip formation in high speed machining of hardened AISI1045 steel is investigated with the aid of optical microscopy and micro-hardness measurement in this paper. The chip morphology evolving from continuous one to serrated one with the cutting speed increasing from 100-1500m/min is observed. Compared with the continuous chip pattern, serrated chip has its particular characterization parameters. The characteristics of serration degree and the segmentation frequency of the serrated chip are presented. The micro-hardness at the adiabatic shear band of serrated chip is then measured. The results show that the serration degree and segmentation frequency of serrated chip have a tendency of enhancement with the cutting speed increasing. The micro-hardness along the adiabatic shear band increases with the cutting speed increasing due to severe strain hardening. With a critical speed at about 100-200m/min, micro-hardness decreases from the tool-chip interface to the free surface of the chip.

Characteristics of serrated chip formation in high-speed machining of metallic materials

2016 ◽  
Vol 86 (5-8) ◽  
pp. 1201-1206 ◽  
Author(s):  
Qibiao Yang ◽  
Yin Wu ◽  
Dun Liu ◽  
Lie Chen ◽  
Deyuan Lou ◽  
...  
Keyword(s):  
Chip Formation ◽  
High Speed ◽  
High Speed Machining ◽  
Metallic Materials ◽  
Serrated Chip ◽  
Serrated Chip Formation

Serrated Chip Formation Induced Periodic Distribution of Morphological and Physical Characteristics in Machined Surface During High-Speed Machining of Ti6Al4V

2021 ◽  
Vol 143 (10) ◽  
Author(s):  
Binbin Xu ◽  
Jun Zhang ◽  
Hongguang Liu ◽  
Xiang Xu ◽  
Wanhua Zhao
Keyword(s):  
Chip Formation ◽  
High Speed ◽  
High Speed Machining ◽  
Serrated Chip ◽  
Machined Surface ◽  
Periodic Distribution ◽  
Serrated Chip Formation ◽  
Simulation Results ◽  
Periodic Profile ◽  
Machined Surfaces

Abstract Difficult-to-cut materials are widely used in aerospace and other industries. Titanium alloys are the most popular ones among them due to their high strength-to-weight ratio and high temperature resistance. However, in high-speed machining, the alloys are prone to produce serrated chips, which have a serious influence on surface integrity. In this study, a coupled Eulerian–Lagrangian method is used to simulate the orthogonal cutting of Ti6Al4V due to its advantages of avoiding element distortion and improving the data extraction efficiency. The internal relationship between serrated chip formation and periodic profile of machined surfaces is analyzed by the simulation results and experimental data which are obtained by optical microscope and white light interferometer. Furthermore, thermal–mechanical loads on machined surfaces are reconstructed based on the simulation results, and a coupled finite element and cellular automata approach is used to describe the dynamic recrystallization process within the area of the machined surface during the formation of a single serration. According to the results, the periodic fluctuation of cutting forces is attributed to the serrated chip formation phenomenon, which then leads to the periodic profile of machined surfaces. The period is about 60–70 µm, and its amplitude decreases with the increase of cutting speeds. Moreover, the loads on machined surfaces also show the same period due to serrated chip formation. As a result, the grain refinement layer thickness (about 2 ∼ 5 µm) in machined surfaces is related to the surface temperature and exhibits the same periodic characteristics along the cutting direction.

Investigation of Chip Morphology in High-Speed Milling of Nickel-Based Superalloy GH706

2014 ◽  
Vol 800-801 ◽  
pp. 113-118
Author(s):  
Sheng Lei Xiao ◽  
Xian Li Liu ◽  
Yu Wang ◽  
Kai Li
Keyword(s):  
Chip Formation ◽  
High Speed ◽  
Cutting Speed ◽  
Chip Morphology ◽  
Adiabatic Shear ◽  
Shear Instability ◽  
Serrated Chip ◽  
High Speed Milling ◽  
Nickel Based Superalloy ◽  
Serrated Chip Formation

This paper analyzed the serrated chip formation process and mechanism in high-speed milling of nickel-based superalloy GH706. Firstly, analyzed two theories of serrated chip formation: cyclical fracture theory and adiabatic shear theory. Secondly, used the simulation of chip formation in high-speed milling of GH706 process, and concluded that the two major theories have achieved dialectical unity when machining for such difficult machining materials. Finally experiments for serrated chip, when cutting speed exceeded 200/min, serrated chips became more obvious. Research has shown that for nickel-based superalloy, adiabatic shear instability of the unstable thermoplastic in the first deformation zoon become the leader of formation of serrated chip, followed as the speed increases, fracture aggravate the degree of serrated chip.

Mechanism of Material Softening in Primary Shear Zone during Serrated Chip Formation in High Speed Machining of High Strength Steel

2009 ◽  
Vol 407-408 ◽  
pp. 504-508
Author(s):  
Chun Zheng Duan ◽  
Min Jie Wang ◽  
Yu Jun Cai
Keyword(s):  
Shear Zone ◽  
Chip Formation ◽  
High Speed ◽  
High Strength ◽  
Shear Zones ◽  
Adiabatic Shear ◽  
Microstructural Development ◽  
High Speed Machining ◽  
Serrated Chip ◽  
Serrated Chip Formation

The metallurgical observations of microstructure characteristics of the adiabatic shear bands(ASB) within the primary shear zones of the serrated chips produced during high speed machining high strength steel have been performed by using optical microscope, SEM and TEM. The observations showed that the microstructure between the matrix and the center of the ASB gradually was changed, the fine equiaxed grains appeared with size of about 0.4～0.6μm in the center of the adiabatic shear band. The serrated chip formation was likely due to material softening that occurred in the primary shear zones. The microstructural development of dynamic recovery and rotational dynamic recrystallization is the dominant metallurgical process leading to material softening in primary shear zone during high speed machining. A model of microstructural development in primary shear zone during serrated chip formation in high speed machining was suggested by analyzing material softening mechanism.

Control and Mechanism Analysis of Serrated Chip Formation in High Speed Machining of Aluminum Alloy 7050-T7451

2020 ◽  
Vol 990 ◽  
pp. 13-17 ◽  
Author(s):  
Qi Hang Shi ◽  
Zong Cheng Hao ◽  
Shuai Wang ◽  
Xiu Li Fu ◽  
Hui Wang
Keyword(s):  
Aluminum Alloy ◽  
Chip Formation ◽  
High Speed ◽  
Morphological Evolution ◽  
Cutting Speed ◽  
Mechanism Analysis ◽  
Serrated Chip ◽  
Machined Surface ◽  
High Speed Cutting ◽  
Cutting Speeds

Aluminum alloy 7050-T7451 is widely used in aeronautical large structural parts, and high speed cutting is often used in machining. The serrated chip is a critical state for chip formation in high speed cutting, and its formation and control mechanism are of great significance for actual machining. To study the chip formation of high speed cutting aluminum alloy 7050-T7451, the chips at different cutting speeds are obtained by high speed cutting experiments. Combined with microscopic observation, the chip shape evolution, chip localization fracture process and mechanism of different cutting speeds are analyzed. The morphological evolution of chips and the mechanism of chip breaking during high speed cutting of aluminum alloy are revealed. According to the machined surface of the chip root and the angle of the chip, the formation mechanism of the curl radius formed by the chip is analyzed. The critical cutting speed of plastic-brittle transformation of aluminum alloy 7050-T7451 in high speed cutting is obtained by studying the critical condition for strip-to-serration transition of chip morphology.

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