Identification of Machining Process Damping Using Output-Only Modal Analysis

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
K. Ahmadi ◽  
Y. Altintas
Keyword(s):  
Orthogonal Cutting ◽  
Machining Process ◽  
Damping Coefficient ◽  
Chatter Stability ◽  
Force Coefficient ◽  
Workpiece Material ◽  
Process Damping ◽  
Indentation Force ◽  
Output Only ◽  
Cutting Speeds

The existing chatter stability prediction algorithms fail in low-speed machining of difficult to cut alloys, unless process damping contributed by the tool flank face–finish surface contact is considered. This paper presents a new method in predicting the material dependent process damping coefficient from chatter free orthogonal cutting tests. An equivalent process damping coefficient of the dynamic system is estimated from the frequency domain decomposition (FDD) of the vibration signals measured during stable cutting tests. Subsequently, the specific indentation force of the workpiece material is identified from the process damping coefficients obtained over a range of cutting speeds. The specific indentation force coefficient is used in an explicit formula of process damping which considers the radius and clearance angle of the cutting edge. It is experimentally shown that when the proposed process damping model is included, the accuracy of chatter stability predictions in turning and milling improves significantly at low cutting speeds.

Identification of Process Damping Coefficient Based on Material Constitutive Property

2014 ◽  
Author(s):  
Xiaoliang Jin
Keyword(s):  
Energy Dissipation ◽  
Flank Wear ◽  
Orthogonal Cutting ◽  
Element Model ◽  
Machining Process ◽  
Damping Coefficient ◽  
Chatter Stability ◽  
Workpiece Material ◽  
Process Damping ◽  
Constitutive Property

The contact between the tool flank wear land and wavy surface of workpiece causes energy dissipation which influences the tool vibration and chatter stability during a dynamic machining process. The process damping coefficient is affected by cutting conditions and constitutive property of workpiece material. This paper presents a finite element model of dynamic orthogonal cutting process with tool round edge and flank wear land. The process damping coefficient is identified based on the energy dissipation principle. The simulated results are experimentally validated.

Study on the Orthogonal Cutting Process of Al7050T7451 with Uncoated and Coated Tools

2008 ◽  
Vol 392-394 ◽  
pp. 990-995 ◽  
Author(s):  
Hui Yue Dong ◽  
Pu Jin Huang ◽  
Y.B. Bi
Keyword(s):  
Finite Element ◽  
High Speed ◽  
High Strain ◽  
Bulk Material ◽  
Orthogonal Cutting ◽  
Cutting Temperature ◽  
Machining Process ◽  
Workpiece Material ◽  
Coated Tool ◽  
The Impact

Tool wear during high speed machining process plays an important role in machining cost and efficiency. The purpose of this study is to examine the impact of tribological properties of coatings on cutting performance. Finite element methods (FEM) were used to model the effect of coated and uncoated cutting tools (K10) on the machinability of the aluminum alloy 7050T7451. Uncoated, Single coated, such as TiC, TiN and Al2O3 and multi-coated tool were studied. All finite element models were assumed to be plane strain. To achieve constitutive model of Al7050T7451 under conditions of machining that high strain rate, high strain and high temperature occur, high speed impact experiment and material drawing experiment were done. Comparison of FEM results shows that the highest temperatures in tools, the temperature change rates of different tools from surface to its bulk material, and the temperatures in chips are changed greatly. It also shows that the cutting temperature of coated tool is lower than uncoated tools, but cutting forces change very little. All these results show that coatings can be used to reduce adhesion between a tool and a workpiece material. The wear resistance of coated tool can be improved effectively and tool life is increased correspondingly.

Analytical Modeling of Process Damping in Machining

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Oguzhan Tuysuz ◽  
Yusuf Altintas
Keyword(s):  
Contact Pressure ◽  
End Milling ◽  
Cutting Edge ◽  
Machining Process ◽  
Chatter Stability ◽  
Experimental Calibration ◽  
Process Damping ◽  
Low Speed ◽  
Edge Geometry ◽  
Five Axis

The machining process induced damping caused by the indentation of the cutting edge into the wavy cut surface greatly affects the process stability in low-speed machining of thermally resistant alloys and hardened steel, which have high-frequency vibration marks packed with short wavelengths. This paper presents an analytical model to predict the process damping forces and chatter stability in low-speed machining operations. The indentation boundaries are evaluated using the cutting edge geometry and the undulated surface waveform. Contact pressure due to the interference of the rounded and straight sections of the rigid cutting edge with the elastic-plastic work material is analytically estimated at discrete positions along the wavy surface. The overall contact pressure is obtained as a function of the cutting edge geometry, vibration frequency and amplitude, and the material properties of the workpiece. The resulting specific indentation force is evaluated by integrating the overall pressure along the contact length. Then, the process damping force is linearized by an equivalent specific viscous damping, which is used in the frequency domain chatter stability analysis. The newly proposed analytical process damping model is experimentally validated by predicting the chatter stability in orthogonal turning, end milling, and five-axis milling of flexible blades. It is shown that the proposed model can replace currently used empirical models, which require extensive experimental calibration approach or computationally prohibitive finite elements based numerical simulation methods.

Finite Element Modeling for Prediction of Stress – Strain at Several Feed Rates and Cutting Speeds for Titanium (Ti-6Al-4V) Alloy

2012 ◽  
Vol 587 ◽  
pp. 11-15
Author(s):  
Moaz H. Ali ◽  
Basim A. Khidhir ◽  
Bashir Mohamed
Keyword(s):  
Finite Element ◽  
Orthogonal Cutting ◽  
Cutting Speed ◽  
Equivalent Strain ◽  
Machining Process ◽  
Depth Of Cut ◽  
General Corrosion ◽  
Explicit Finite Element ◽  
Finite Element Software ◽  
Cutting Speeds

Titanium (Ti-6Al-4V) alloy is a desirable material for the aircraft industry because of their excellent properties behaves of high specific strength, fracture resistant characteristics, lightweight and general corrosion resistance. This paper presents a study on a two-dimensional orthogonal cutting process by using a face-milling operation through ABAQUS/EXPLICIT finite-element software. Several tests were performed at various feed rates and cutting speeds while the depth of cut remains constant. The results led to the conclusion that the stress components at integration points (Von - Mises) and the equivalent strain (PEEQ) were increased with increasing the feed rate and cutting speed during the machining process.

An Experimental Study of High Speed Orthogonal Cutting

1998 ◽  
Vol 120 (1) ◽  
pp. 169-172 ◽  
Author(s):  
G. Sutter ◽  
A. Molinari ◽  
L. Faure ◽  
J. R. Klepaczko ◽  
D. Dudzinski
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Orthogonal Cutting ◽  
Cutting Speed ◽  
High Speed Machining ◽  
Workpiece Material ◽  
Wide Range ◽  
Longitudinal Cutting ◽  
Material Interaction ◽  
Cutting Speeds

A new high speed machining experiment is designed to obtain orthogonal cutting in a wide range of cutting speeds from 7 m/s to 100 m/s. Quasi-stationary cutting conditions are obtained. The measurement of the longitudinal cutting force reveals the existence of an optimal cutting speed for which the energy consumption is minimum. The genuine tool-workpiece material interaction can be analyzed with that experimental device.

scholarly journals An Evaluation of Ploughing Models for Orthogonal Machining

1999 ◽  
Vol 121 (4) ◽  
pp. 550-558 ◽  
Author(s):  
D. J. Waldorf ◽  
R. E. DeVor ◽  
S. G. Kapoor
Keyword(s):  
Cutting Tool ◽  
Metal Removal ◽  
Orthogonal Cutting ◽  
Cutting Edge ◽  
Machining Process ◽  
Separation Point ◽  
Workpiece Material ◽  
Orthogonal Machining ◽  
Edge Component ◽  
Material Separation

An analytical comparison is made between two basic models of the flow of workpiece material around the edge of an orthogonal cutting tool during steady-state metal removal. Each has been the basis for assumptions in previous studies which attempt to model the machining process, but no direct comparison had been made to determine which, if either, is an appropriate model. One model assumes that a separation point exists on the rounded cutting edge while the other includes a stable build-up adhered to the edge and assumes a separation point at the outer extreme of the build-up. Theories of elastic-plastic deformation are employed to develop force predictions based on each model, and experiments are performed on 6061-T6 aluminum alloy to evaluate modeling success. The experiments utilize unusually large cutting edge radii to isolate the edge component of the total cutting forces. Results suggest that a material separation point on the tool itself does not exist and that the model that includes a stable build-up works better to describe the experimental observations.

Chatter Stability in Micro Milling Processes Considering Ploughing and Process Damping Effects

2009 ◽  
Author(s):  
Ramin Rahnama ◽  
Mozhdeh Sajjadi ◽  
Simon S. Park
Keyword(s):  
Time Domain ◽  
Chip Thickness ◽  
Experimental Tests ◽  
Micro Milling ◽  
Chatter Stability ◽  
Workpiece Material ◽  
Process Damping ◽  
Milling Operations ◽  
Milling Operation ◽  
Cutting Mechanisms

Micro milling operations utilize miniature tools to remove workpiece material, in order to create the desired 3D miniature components. One of the challenges in a micro milling operation is the unstable phenomenon called regenerative chatter. The occurrence of chatter in the micro domain, as in macro machining, is detrimental to part finishes and significantly reduces the longevity of tools. There are two different cutting mechanisms in micro milling operations, which are determined by the critical chip thickness. When the chip thickness is less than the critical chip thickness, no chip forms and ploughing occurs; whereas, when the chip thickness is greater than the critical chip thickness, a chip forms and shearing cutting happens. During each rotation of the tool, the cutting mechanisms switch from ploughing to shearing and vice versa. This paper introduces a time domain chatter model to investigate the effects of the ploughing and shearing mechanisms on stability. The model also considers the effects of process damping in micro milling, especially at low spindle speeds. Several experimental tests have been performed to validate the model.

Material Behavior Modeling in Machining Simulation of 7075-T651 Aluminum Alloy

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Shuhui Li ◽  
Bo Hou
Keyword(s):  
Aluminum Alloy ◽  
Flow Stress ◽  
Orthogonal Cutting ◽  
Material Behavior ◽  
Experimental Results ◽  
Machining Process ◽  
Dynamic Flow ◽  
Workpiece Material ◽  
Damage Criterion ◽  
Damage Initiation

Accurate modeling of workpiece material behavior in machining is critical to analyze and design a process. The workpiece material behavior in the machining process involves dynamic flow stress and damage/fracture behavior, which are very difficult to be determined. In this study, the extended split Hopkinson pressure bar (SHPB) test is conducted to determine the dynamic flow stress curves of 7075-T651 aluminum alloy, which enables the strain, strain rate and the temperature obtained in the test to approach that in the cutting condition. A damage criterion under the typical stress state of orthogonal cutting is established to reflect the material damage initiation in primary shear zone. The damage criterion parameters of 7075-T651 alloy are determined by comparing the numerical and experimental results of the proposed inner high-pressure piercing fracture test. The orthogonal cutting test and simulation of 7075-T651 alloy are conducted. It is demonstrated that the determined flow stress and the established damage criterion produces realistic process outputs in agreement with experimental results.

Studying The Effect of a New Mixed Cutting Fluid on Surface Roughness

2020 ◽  
Vol 38 (11A) ◽  
pp. 1593-1601
Author(s):  
Mohammed H. Shaker ◽  
Salah K. Jawad ◽  
Maan A. Tawfiq
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Cutting Parameters ◽  
Machining Process ◽  
Cutting Fluid ◽  
Depth Of Cut ◽  
Cutting Fluids ◽  
Machining Processes ◽  
Dry Cutting ◽  
Cutting Speeds

This research studied the influence of cutting fluids and cutting parameters on the surface roughness for stainless steel worked by turning machine in dry and wet cutting cases. The work was done with different cutting speeds, and feed rates with a fixed depth of cutting. During the machining process, heat was generated and effects of higher surface roughness of work material. In this study, the effects of some cutting fluids, and dry cutting on surface roughness have been examined in turning of AISI316 stainless steel material. Sodium Lauryl Ether Sulfate (SLES) instead of other soluble oils has been used and compared to dry machining processes. Experiments have been performed at four cutting speeds (60, 95, 155, 240) m/min, feed rates (0.065, 0.08, 0.096, 0.114) mm/rev. and constant depth of cut (0.5) mm. The amount of decrease in Ra after the used suggested mixture arrived at (0.21µm), while Ra exceeded (1µm) in case of soluble oils This means the suggested mixture gave the best results of lubricating properties than other cases.

scholarly journals Serrated Chips Formation in Micro Orthogonal Cutting of Ti6Al4V Alloys with Equiaxial and Martensitic Microstructures

Micromachines ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 197 ◽  
Author(s):  
ZeJia Zhao ◽  
Suet To ◽  
ZhuoXuan Zhuang
Keyword(s):  
Cutting Force ◽  
Unit Length ◽  
Orthogonal Cutting ◽  
Machining Process ◽  
Orthogonal Machining ◽  
Large Yield ◽  
Power Spectral ◽  
Straight Line ◽  
Serrated Chips ◽  
Electropulsing Treatment

The formation of serrated chips is an important feature during machining of difficult-to-cut materials, such as titanium alloy, nickel based alloy, and some steels. In this study, Ti6Al4V alloys with equiaxial and acicular martensitic microstructures were adopted to analyze the effects of material structures on the formation of serrated chips in straight line micro orthogonal machining. The martensitic alloy was obtained using highly efficient electropulsing treatment (EPT) followed by water quenching. The results showed that serrated chips could be formed on both Ti6Al4V alloys, however the chip features varied with material microstructures. The number of chip segments per unit length of the alloy with martensite was more than that of the equiaxial alloy due to poor ductility. Besides, the average cutting and thrust forces were about 8.41 and 4.53 N, respectively, for the equiaxed Ti6Al4V alloys, which were consistently lower than those with a martensitic structure. The high cutting force of martensitic alloy is because of the large yield stress required to overcome plastic deformation, and this force is also significantly affected by the orientations of the martensite. Power spectral density (PSD) analyses indicated that the characteristic frequency of cutting force variation of the equiaxed alloy ranged from 100 to 200 Hz, while it ranged from 200 to 400 Hz for workpieces with martensites, which was supposedly due to the formation of serrated chips during the machining process.

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