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.

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

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.

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.

Finite Element Investigation of the Influence of Thermophysical Parameters on Segmented Chip Formation during High Speed Cutting

2011 ◽  
Vol 130-134 ◽  
pp. 2817-2821
Author(s):  
You Xi Lin ◽  
Cong Ming Yan
Keyword(s):  
Thermal Conductivity ◽  
Finite Element ◽  
Specific Heat ◽  
Chip Formation ◽  
High Speed ◽  
Element Model ◽  
Serrated Chip ◽  
High Speed Cutting ◽  
Thermophysical Parameters ◽  
Serrated Chip Formation

A 2D fully thermal mechanical coupled finite element model is applied to study the influence of material parameters on serrate chip formation during high speed cutting process. The serrated chip formation during high speed machining was predicted. Of interests are the effects of thermal conductivity, specific heat and density. Results showed significant influence of these thermophysical parameters on the serrated chip phenomena, especially in the case of the density. Increasing thermal conductivity specific heat and density lead to a decreasing degree of segmentation. The influence of the thermal conductivity on the cutting force and the specific heat on maximum temperatures in the shear band is also discussed.

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.

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