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.

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.

Prediction of Chip Morphology and Formation in High Speed Milling of Hardened Steels

2015 ◽  
Vol 1120-1121 ◽  
pp. 1145-1152
Author(s):  
Jun Zhong Pang ◽  
Xiao Bin Huang ◽  
Dou Dou Chang ◽  
Jie Pan
Keyword(s):  
Chip Formation ◽  
High Speed ◽  
Shear Banding ◽  
Chip Morphology ◽  
Material Model ◽  
Adiabatic Shear ◽  
Serrated Chip ◽  
Adiabatic Shear Banding ◽  
Serrated Chip Formation ◽  
Material Constitutive Equation

A P20 steel are machined in the milling speed range of 200 to 942m/min. The morphology and formation of the chips are investigated at various speeds. The serrated chips with adiabatic shear band are observed at a high milling speed. The transition from continuous to serrated chip formation is favored by the increase in work material hardness and milling speed. The study assumes that the chip segmentation is only induced by adiabatic shear banding, without material failure in the primary shear zone. Based on adiabatic shear theory, using the JC and the power material constitutive equation, the modified material model which takes into a strain softening is developed for prediction of the serrated chip formation. Experimental measurements are compared with the simulation results.

Experimental and FEM Study of Serrated Chip Formation in High Speed Turning Processes

2011 ◽  
Vol 264-265 ◽  
pp. 1021-1026
Author(s):  
U. Umer ◽  
Li Jing Xie ◽  
Syed Jawid Askari ◽  
S.N. Danish ◽  
S.I. Butt
Keyword(s):  
Chip Formation ◽  
Cutting Forces ◽  
High Speed ◽  
Metal Cutting ◽  
Orthogonal Cutting ◽  
Cutting Speed ◽  
Chip Morphology ◽  
Serrated Chip ◽  
High Speed Turning ◽  
Serrated Chip Formation

The finite element method (FEM) has been used to model high speed turning processes with orthogonal cutting conditions. In most of the situations, continuous chip formation is used to analyze the turning process due to its stability and allowing many conditions to simplify the process. However with the increasing applications of high speed turning, serrated chip formation is becoming a more common phenomenon in metal cutting. Serrated chips usually occur in machining of difficult to cut materials at or above a threshold speed. An updated Lagrangian formulation has been used in this study which works with element deletion technique based on a failure criterion. The Johnson Cook strain-hardening thermal-softening material model is used to model serrated chip formation. In addition high speed turning experiments were conducted on AISI H13 tubes using PCBN to analyze serrated chip phenomenon. The chips were analyzed after surface treatment using scanning electron microscope. It has been found that the length of cuts in the chip increases with the cutting speed and the chip changes from serrated to discontinuous. Different process variables like cutting forces, chip morphology, stress, strain and temperature distributions are predicted at different process parameters using FEM. The results show cyclic variation in the cutting forces at high cutting speeds due to varying chip load.

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.

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.

Chip Morphology in High Speed Precision Turning Process of Hardened Steel GCr15

2013 ◽  
Vol 579-580 ◽  
pp. 12-15
Author(s):  
Guang Jun Chen ◽  
Ling Guo Kong ◽  
Qun Gao ◽  
Xian Li Liu
Keyword(s):  
Chip Formation ◽  
High Speed ◽  
Hard Turning ◽  
Chip Morphology ◽  
Hardened Steel ◽  
Adiabatic Shear ◽  
Apical Surface ◽  
Turning Process ◽  
Serrated Chip ◽  
Precision Turning

The main characteristic of hard turning process is easy to produce serrated chip. The chip deformation will impact greatly turning process. It is very important to analysis the chip formation and morphology during precision turning process of hardened steel. The deformation mechanism of serrated chip formation process and its chip morphology of chips produced during precision turning process of the hardened steel GCr15 is studied in hard cutting experiment by the methods such as numerical simulation of two-dimensional finite element analysis of turning, chip cross-sectional microscopic analysis and other methods .High speed precision turning of hardened steel GCr15 produces morphology of continuous chip and serrated chip; Serrated chip has the typical characteristics of the adiabatic shear slip after section such as apical surface of the serrated chip is composed of multilayer rolling dentate shear plane, a single surface of one tooth is not smooth, but no crack. Extrusion grooves is produced from tooth root to tip; Intensive slip line on serrated chip cross-section can be saw by microscopic observation; Fracture surface of the serrated chip presents small tumor tissues. The results show that the reason of hardened GCr15 steel forming serrated chip is periodic adiabatic shear fracture, and the research provides a theoretical reference application of hard turning technology.

Study on Chip Morphology and Adiabatic Shear in High Speed Cutting of Alloy Steels with Different Hardness

2010 ◽  
Vol 26-28 ◽  
pp. 875-879
Author(s):  
Chun Zheng Duan ◽  
Hong Hua Li ◽  
Min Jie Wang ◽  
Yu Jun Cai
Keyword(s):  
Shear Band ◽  
High Speed ◽  
Adiabatic Shear Band ◽  
Shear Bands ◽  
Cutting Speed ◽  
Chip Morphology ◽  
Optical Microscope ◽  
Adiabatic Shear ◽  
Serrated Chip ◽  
High Speed Cutting

The chip morphology and the formation and development of the adiabatic shear band within the serrated chips formed in high speed cutting of 30CrNi3MoV steel with two tempering hardness were observed and analyzed using optical microscope and SEM. The investigation shows that as the adiabatic shear phenomenon occurs and develops, the chip morphology changes as follows: ribbon chip→serrated chip with deformed band→serrated chip with transformed band→fractured chip. The cutting speed and tempering hardness is the two main factors affecting adiabatic shear, in the case of lower cutting speed the formation and development of adiabatic shear band are more sensitive to tempered hardness increase. The deformed shear bands are constituted by large deformed microstructure, while the formation of the transformed shear bands has experienced the large plastic deformation and grain refinement.

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