A Finite Element Analysis of Void Evolution in 2-D Machining

2002 ◽  
Author(s):  
Q. Cao ◽  
K. C. Ee ◽  
O. W. Dillon ◽  
I. S. Jawahir
Keyword(s):  
Damage Mechanics ◽  
Volume Fraction ◽  
Void Nucleation ◽  
Hydrostatic Stress ◽  
Effective Strain ◽  
Machining Process ◽  
Void Coalescence ◽  
Machining Parameters ◽  
Machined Surface ◽  
Void Evolution

The objective of this paper is to study void evolution and its effects on material failure during the machining process. The influence of cutting conditions on void nucleation, growth and coalescence is studied. The ultimate goal of this approach, as applied to machining, is to predict chip breakage and surface conditions via damage mechanics. A damage mechanics model proposed by Komori [1] is chosen to study the evolution of the void volume fraction in the chip and workpiece being machined with a grooved tool. A Thomason [2] type criterion as modified by Dhar et al. [3], that uses the variables calculated by FEM analysis, is used to predict void coalescence (failure). The distribution of the variables, such as effective strain-rate, nondimensional hydrostatic stress, and effective strain are obtained using the FEM methodology described by Zhang [4]. It is found that void coalescence always occurs in the newly machined surface below the flank face of the tool and in the chip flowing around the chip-groove region near the upper end of the face land. On the other hand, whether void coalescence occurs inside the chip or not, depends on the complex interactions between the machining parameters and chip geometry.

scholarly journals The Modified Void Nucleation and Growth Model (MNAG) for Damage Evolution in BCC Ta

2021 ◽  
Vol 11 (8) ◽  
pp. 3378
Author(s):  
Jie Chen ◽  
Darby J. Luscher ◽  
Saryu J. Fensin
Keyword(s):  
Growth Model ◽  
Damage Evolution ◽  
Volume Fraction ◽  
Void Nucleation ◽  
Nucleation And Growth ◽  
Void Coalescence ◽  
Hydrodynamic Simulations ◽  
Void Evolution ◽  
Void Nucleation And Growth ◽  
Nucleation Growth

A void coalescence term was proposed as an addition to the original void nucleation and growth (NAG) model to accurately describe void evolution under dynamic loading. The new model, termed as modified void nucleation and growth model (MNAG model), incorporated analytic equations to explicitly account for the evolution of the void number density and the void volume fraction (damage) during void nucleation, growth, as well as the coalescence stage. The parameters in the MNAG model were fitted to molecular dynamics (MD) shock data for single-crystal and nanocrystalline Ta, and the corresponding nucleation, growth, and coalescence rates were extracted. The results suggested that void nucleation, growth, and coalescence rates were dependent on the orientation as well as grain size. Compared to other models, such as NAG, Cocks–Ashby, Tepla, and Tonks, which were only able to reproduce early or later stage damage evolution, the MNAG model was able to reproduce all stages associated with nucleation, growth, and coalescence. The MNAG model could provide the basis for hydrodynamic simulations to improve the fidelity of the damage nucleation and evolution in 3-D microstructures.

scholarly journals Effects of the Tribological Behaviour of h-BN MQL Nano Cutting Fluid (NCF-MQL) on Turning Inconel 625

2019 ◽  
Vol 11 (4) ◽  
pp. 107-121 ◽  
Author(s):  
Chinmaya PADHY ◽  
Pariniti SINGH
Keyword(s):  
Optimization Technique ◽  
Minimum Quantity Lubrication ◽  
Chip Morphology ◽  
Machining Process ◽  
Cutting Fluid ◽  
Inconel 625 ◽  
Machining Parameters ◽  
Machining Performance ◽  
Tribological Behaviour ◽  
Machined Surface

Minimum quantity lubrication (MQL) is currently a widely used lubricating technique during machining, in which minimum amount of lubricant in the form of mist is delivered to the machining interface, thus helps to reduce the negative effects caused to the environment and human health. Further, to enhance the productivity of machining process specifically for hard-to-cut materials, nano cutting fluid (suitably mixed nano materials with conventional cutting fluid) is used as an alternative method to conventional lubrication (wet) in MQL. In this study, h-BN nano cutting fluid was formulated with 0.1% vol. concentration of h-BN in conventional cutting fluid (Servo- ‘S’) for NCF-MQL technique and its tribological behaviors on machining(turning) performance of Inconel 625 were studied and compared with other lubricating conditions (dry, wet, MQL conventional). The tribological effects were analyzed in terms of tool wear analysis, chip morphology along with statistical analysis for machined surface and evolved cutting forces during machining. The optimal input machining parameters for experiments were defined by the use of Taguchi and Grey relational based multi response optimization technique. Finally, the tribological study shows that the use of h-BN NCF-MQL is a viable and sustainable option for improving machining performance of hard- to- cut material like Inconel 625.

Micro-Mechanics of Creep-Fatigue Damage in PB-SN Solder Due to Thermal Cycling—Part I: Formulation

2002 ◽  
Vol 124 (3) ◽  
pp. 292-297 ◽  
Author(s):  
Pradeep Sharma ◽  
Abhijit Dasgupta
Keyword(s):  
Fatigue Damage ◽  
Damage Mechanics ◽  
Void Nucleation ◽  
Cyclic Creep ◽  
Diffusional Creep ◽  
Void Coalescence ◽  
Second Phase ◽  
Structural Stress ◽  
Damage Initiation ◽  
Creep Fatigue

This paper presents a micro-mechanistic approach for modeling fatigue damage initiation due to cyclic creep in eutectic Pb-Sn solder. Damage mechanics due to cyclic creep is modeled with void nucleation, void growth, and void coalescence model based on micro-structural stress fields. Micro-structural stress states are estimated under viscoplastic phenomena like grain boundary sliding, its blocking at second-phase particles, and diffusional creep relaxation. In Part II of this paper, the developed creep-fatigue damage model is quantified and parametric studies are provided to better illustrate the utility of the developed model.

Void Nucleation Effects in Biaxially Stretched Sheets

1980 ◽  
Vol 102 (3) ◽  
pp. 249-256 ◽  
Author(s):  
C. C. Chu ◽  
A. Needleman
Keyword(s):  
Plastic Strain ◽  
Volume Fraction ◽  
Void Nucleation ◽  
Hydrostatic Stress ◽  
Forming Limit ◽  
Stress Theory ◽  
Out Of Plane ◽  
Necking Criterion ◽  
Controlled Nucleation ◽  
Forming Limit Curves

The effects of void nucleation occurring during the deformation history on forming limit curves are considered for both in-plane and punch stretching employing a constitutive model of a porous plastic solid. Both plastic strain controlled and stress controlled nucleation processes are simulated by a two parameter void nucleation criterion. For in-plane stretching, plastic strain controlled nucleation can have, in certain circumstances, a significantly destabilizing effect on the forming limit curve. However, within the framework of plane stress theory which neglects the enhancement of the hydrostatic stress due to necking, a stress controlled nucleation process is not found to be significantly destabilizing. In punch stretching a ductile rupture criterion, which limits the maximum volume fraction of voids, as well as the appearance of a well defined thickness trough, is adopted as a localized necking criterion. Only plastic strain controlled void nucleation is considered here in out-of-plane stretching. The resulting forming limit curves have the same shape as those obtained previously with void nucleation neglected.

Evaluation of Electrical Discharge Machining Performance on Al (6351)–SiC–B4C Composite

2019 ◽  
pp. 109-124
Author(s):  
Uthayakumar M. ◽  
Suresh Kumar S. ◽  
Thirumalai Kumaran S. ◽  
Parameswaran P.
Keyword(s):  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Research Work ◽  
Machining Process ◽  
Electrode Wear ◽  
Machining Parameters ◽  
Machining Performance ◽  
Machined Surface ◽  
Output Performance ◽  
B4c Particles

Electrical discharge machining (EDM) process is a non-conventional machining process used for the material which are difficult to machine. In this research work, an attempt has been made to determine the influence of Boron Carbide (B4C) particles on the machinablity of the Al (6351) alloy reinforced with 5 wt. % Silicon Carbide (SiC) Metal Matrix Composite (MMC) through EDM. Influence of machining parameters such as pulse current (I), pulse on time (Ton), duty factor (τ), and gap voltage (V) on affecting the output performance characteristics namely Electrode Wear Ratio (EWR), Surface Roughness (SR) and Power Consumption (PC) which are studied. The result shows that the addition of B4C particles significantly affects the machinablity of the composite, with a contribution of 1.6% on EWR, 3.5% on SR and 19.8% on PC. The crater, recast layer formation, and Heat Affected Zone (HAZ) in the machined surface of the composite are also reported in detail.

scholarly journals Forward and Inverse Relational Models between Machined Surface Roughness and Key Parameters of Machining Process

2021 ◽  
Author(s):  
Ri Pan ◽  
Ren Xingfei ◽  
Zhenzhong Wang ◽  
Dongju Chen ◽  
Jinwei Fan
Keyword(s):  
Surface Roughness ◽  
Inverse Model ◽  
Forward Model ◽  
Machining Process ◽  
Relational Model ◽  
Universal Method ◽  
Machining Parameters ◽  
Machined Surface ◽  
Average Deviation ◽  
Machined Surface Roughness

Abstract The relational model between machined surface roughness (MSR) and the adopted key machining parameters (KMPs) significantly influences the predictability and controllability of the machining process; therefore, it has attracted considerable attention. However, two critical problems still persist in this field. First, although most existing studies focus on the prediction model for MSR (forward model), wherein the MSR is dependent on input KMPs values, the inverse model that can calculate the KMP based on input MSR value is equally important; however, the inverse model has not been investigated as extensively as the forward model. The second issue is that most of the existing forward models are mainly established based on mechanism analysis; however, due to the complexity of most machining processes, the accuracy and generality of the model are not optimal. Therefore, this paper proposes a universal method for mathematically establishing the inverse model of the relation between the MSR and KMP. Initially, based on the response surface methodology, orthogonal experiments were designed and conducted, and the results were used to establish the forward model between the MSR and KMP. Subsequently, by combining the forward model with a self-developed genetic algorithm-based multi-objective optimization algorithm, an establishing method for inverse model between MSR and KMPs was proposed. Finally, experiments were conducted to validate the developed models. The experimental results show that for the forward model, all the 10 experimental MSR values approach the MSR values predicted by the forward model, and the average deviation was only approximately 7%. Contrarily, for the inverse model, the average deviation was only approximately 7.64%. Both these results verify the accuracy and effectiveness of the proposed models. With this method, as long as the desired processing results and constraints are given, the process parameters can be accurately derived.

scholarly journals Effect of Micro-EDM Parameters on Material Removal Rate of Nonconductive ZrO2 Ceramic

2013 ◽  
Vol 465-466 ◽  
pp. 1329-1333 ◽  
Author(s):  
Abdus Sabur ◽  
Abdul Moudood ◽  
Mohammad Yeakub Ali ◽  
Mohammad Abdul Maleque
Keyword(s):  
Material Removal Rate ◽  
Material Removal ◽  
Removal Rate ◽  
Pyrolytic Carbon ◽  
Carbon Layer ◽  
Machining Process ◽  
Machining Parameters ◽  
Micro Edm ◽  
Machined Surface ◽  
Electro Discharge Machining

Micro-electro discharge machining (micro-EDM) technique, an advanced noncontact machining process, is used for structuring of nonconductive ZrO2 ceramic. In this study copper foil as a conductive layer is adhered on the workpiece surface to initiate the sparks and kerosene is used as dielectric for creation of continuous conductive pyrolytic carbon layer on the machined surface. Voltage (V) and capacitance (C) are considered as the parameters to investigate the process capability of machining parameters in continuous micro-EDM of ZrO2. Different voltage pulses are studied to examine the causes of lower material removal rate (MRR) in micro-EDM of nonconductive ceramics. The results showed that in micro-EDM of ZrO2 MRR increases with the increase of voltage and capacitance initially, but decreases at higher values and no significant materials are removed at capacitances higher than 1nF.

scholarly journals Application of Wavelet Analysis in Tool Wear Evaluation Using Image Processing Method

2018 ◽  
Vol 7 (4.36) ◽  
pp. 426
Author(s):  
Lee Woon Kiow ◽  
Syed Mohamad Aiman Tuan Muda ◽  
Ong Pauline ◽  
Sia Chee Kiong ◽  
Norfazillah Talib ◽  
...  
Keyword(s):  
Wavelet Analysis ◽  
Tool Wear ◽  
Cutting Tool ◽  
Wavelet Coefficient ◽  
Surface Profile ◽  
Machining Process ◽  
Machining Parameters ◽  
Continuous Wavelet ◽  
Monitoring Methods ◽  
Machined Surface

Tool wear plays a significant role for proper planning and control of machining parameters to maintain the product quality. However, existing tool wear monitoring methods using sensor signals still have limitations. Since the cutting tool operates directly on the workpiece during machining process, the machined surface provides valuable information about the cutting tool condition. Therefore, the objective of present study is to evaluate the tool wear based on the workpiece profile signature by using wavelet analysis. The effect of wavelet families, scale of wavelet and statistical features of the continuous wavelet coefficient on the tool wear is studied. The surface profile of workpiece was captured using a DSLR camera. Invariant moment method was applied to extract the surface profile up to sub-pixel accuracy. The extracted surface profile was analyzed by using continuous wavelet transform (CWT) written in MATLAB. The results showed that average, RMS and peak to valley of CWT coefficients at all scale increased with tool wear. Peak to valley at higher scale is more sensitive to tool wear. Haar was found to be more effective and significant to correlate with tool wear with highest R2 which is 0.9301.   

scholarly journals Cryogenic milling and formation of nanostructured machined surface of AISI 4340

2020 ◽  
Vol 9 (1) ◽  
pp. 1104-1117
Author(s):  
Shalina Sheik Muhamad ◽  
Jaharah A. Ghani ◽  
Che Hassan Che Haron ◽  
Hafizal Yazid
Keyword(s):  
End Milling ◽  
Testing Machine ◽  
Machining Process ◽  
Depth Of Cut ◽  
Case Hardening ◽  
Machining Parameters ◽  
Machined Surface ◽  
Radial Depth ◽  
Coated Carbide ◽  
Aisi 4340

AbstractHardened layers are commonly required for automotive components after their production using a machining process in order to enhance the service life of these components. This study investigates the possibility of producing a nanostructured machined surface which can increase the hardness of the machined surface by varying the machining parameters under cryogenic conditions in end milling of AISI 4340. The end milling experiments were performed using multi-layered TiAlN- and AlCrN-coated carbide. Prior to the experiment, a finite element method (FEM) was used to simulate the cutting temperature generated and it had been found that at cutting speed of 200–300 m/min, feed rate of 0.15–0.3 mm/tooth, axial depth of cut of 0.3–0.5 mm, and radial depth of cut of 0.2–0.35 mm, the temperature generated can be sufficiently high to cause austenitic transformation. A field emission scanning electron microscope (FESEM) equipped with angle selective backscattered (AsB) detection analysis was used to investigate the microstructure and machined-affected layers of the machined surfaces. The crystallographic orientation/phase change and nano-hardness were analysed through X-ray diffraction (XRD) and a nano-hardness testing machine. The results showed that the cryogenic machining had significantly affected the surface integrity characteristics of the AISI 4340 alloy due to refined microstructure, favourable phase structure, and higher hardness near the surface layer. The results of this study may be useful in providing an insight into a potential technological shift from conventional surface case hardening processes to the present technique.

Controlling Topography of Machined Surface for Adhesive-Sealing

2017 ◽  
Author(s):  
Shun Liu ◽  
Sun Jin ◽  
Xueping Zhang ◽  
Lixin Wang ◽  
Benfu Mei ◽  
...  
Keyword(s):  
Surface Topography ◽  
Adhesive Bonding ◽  
Bonding Process ◽  
Machining Process ◽  
Machining Parameters ◽  
Machined Surface ◽  
Sealing Performance ◽  
Joint Surfaces ◽  
Machining Productivity ◽  
Adhesive Performance

Adhesive is widely used in engine, airplane and other industry parts to bond and seal machined joint surfaces. Adhesive performance is important and mechanically complex, closely related to the adhesive material property, bonding process and topography of machined surfaces. The effects of material properties, bonding process, and the geometry and dimensions of adhesive layer on adhesive performance have been well studied in adhesive research field. However, the effect of the topography of machined surface on sealing performance was somehow neglected in literature. On the other hand, the texture of machined surface, especially at micro-level of surface roughness, usually used as the objective to determine process parameters in machining and also regarded as indicators of machining productivity, has been systemically and sufficiently studied. However sealing performance has not been widely investigated to relate to topography of machined surface generated from machining operation. Actually, the surface topography plays an important role in the both fields as an index for machining process and also a factor for functional performance. Desired surface should be determined firstly and then machining parameters are designed properly to achieve the desired surface, in order to improve the functional behavior such as the applied adhesive sealing performance of machined components. This research has objectives: 1) the desired surface topography is determined based on the relationship between machining operation and surface texture; 2) The effects of machined surface topography on the reliability of adhesive joint surfaces are analytically investigated. Thus, the research provides a systematic thinking for the selection of surface topography and parameters of face milling operation to improve the performance of adhesive bonding and sealing for its industry implementation.

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