scholarly journals Evaluation of Chip Formation Mechanisms in the Turning of Sintered ZnO Electro-Ceramics

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1422
Author(s):  
Jaka Dugar ◽  
Awais Ikram ◽  
Franci Pušavec
Keyword(s):  
Chip Formation ◽  
Formation Mechanisms ◽  
Machining Parameters ◽  
Cutting Mechanism ◽  
Pull Out ◽  
Careful Handling ◽  
Zno Varistors ◽  
Robust Measurements ◽  
Conventional Machining ◽  
Zno Ceramics

The sintered zinc oxide (ZnO) electro-ceramics are a brittle class of hard-to-cut materials such that shaping them with the post-finishing operations necessitates careful handling and precision machining. The conventional machining approach using the grinding and lapping processes represents limited productivity, an inability to produce the required geometries and frequent uncontrolled chipping of the edges of the final products. This study thus investigates the turning performance of dense sintered ZnO varistors and chip formations to obtain the parametric range (cutting mechanism) which causes the chipping or the trans-granular/sudden failure in these brittle materials. With the analysis of the cutting tool vibration in relation to the machining parameters (f and VC), the vibration-induced chipping correlations are made and interlinked with the occurrence of grain pull-out during the turning operation. The results show that the reflected vibratory motion of the tools is directly correlated with the chip formation mechanisms in the turning of ZnO ceramics and thus provide robust measurements for quality assurance in final products.

A new quick-stop device to study the chip formation mechanism in metal cutting: Computational and experimental investigation

2021 ◽  
pp. 095440622110342
Author(s):  
Mohamed Baccar Mhamdi ◽  
Wajdi Rajhi ◽  
Mohamed Boujelbene ◽  
Sahbi Ben Salem ◽  
Sonia Ezeddini ◽  
...  
Keyword(s):  
Chip Formation ◽  
Metal Cutting ◽  
Cutting Tools ◽  
Cutting Parameters ◽  
Hard Metal ◽  
Formation Mechanisms ◽  
Machining Parameters ◽  
Chip Formation Mechanism ◽  
Aisi D2 ◽  
Stop Test

Understanding the chip formation mechanisms during machining is an important factor to facilitate the choice of cutting tools and machining parameters. Despite the appearance of new sophisticated methods and advanced equipment, the technique so called quick-Stop Test (QST) remains efficient, less costly, and easier to apply in the investigation of chip formation in cutting process. In present paper a new Quick-Stop Device QSD is designed, numerically simulated, implemented, and tested. The reformed QST technique uses a QSD device which operates on the modified Charpy pendulum. Accordingly, design of new QSD is presented and deeply described, and 2D FE modeling of the new QST, including the application of the appropriate boundary conditions, has been carried out. Moreover, chip formation and morphology for different cutting conditions have been effectively simulated. Subsequently, quick stop cutting operations including metal cutting tests of high alloyed tool steel (AISI D2) using fabricated new QSD are performed. Preliminary results of quick-stop experiment from current investigation prove the effectiveness of the new designed QSD in matter of rigidity, safety, and absence of vibration, while providing a fast set up time and allowing extremely short workpiece-cutting tool separation time and guarantee the generation of chip with its root. The photomicrographs of chip root samples gathered from hard metal cutting experiments including various cutting speeds machining conditions, enables clear observation of segmented chip formation mechanisms, thereby, highly promising the new designed QSD for the purpose of investigation of the different cutting parameters influencing the chip formation and morphology.

Study on carbon epoxy composite surfaces machined by abrasive water jet machining

2018 ◽  
Vol 53 (20) ◽  
pp. 2909-2924 ◽  
Author(s):  
Ajit Dhanawade ◽  
Shailendra Kumar
Keyword(s):  
Surface Roughness ◽  
Composite Material ◽  
Process Parameters ◽  
Surface Finish ◽  
Epoxy Composite ◽  
Water Jet ◽  
Machining Parameters ◽  
Abrasive Water Jet ◽  
Abrasive Water Jet Machining ◽  
Pull Out

Traditional machining of carbon epoxy composite material is difficult due to excessive tool wear, excessive stresses and heat generation, delamination, high surface waviness, etc. In the present paper, research work involved in the experimental study of abrasive water jet machining of carbon epoxy composite material is described. The aim of present work is to improve surface finish and studying defects in machined samples. Taguchi's orthogonal array approach is used to design experiments. Process parameters namely hydraulic pressure, traverse rate, stand-off distance and abrasive mass flow rate are considered for this study. Analysis of machined surfaces and kerf quality is carried out using scanning electron microscope to evaluate microscopic features. Further, the effect of machining parameters on surface roughness is investigated using analysis of variance approach. It is found that traverse rate and pressure are most significant parameters to control surface roughness. Optimization of process parameters is performed using grey relational analysis. Thereafter, confirmation tests are carried out to verify the improvement in the surface quality with optimum set of process parameters. It is found that surface finish of machined samples is improved by 10.75% with optimum levels of process parameters. Defects like delamination, fiber pull-out and abrasive embedment are also studied using SEM. It is observed that delamination and fiber pull-out are prominent in samples machined at low pressure and high traverse rate.

scholarly journals A Comparative Study between the Effects of Magnetic and Nonmagnetic Dopants on the Properties of ZnO Varistors

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
A. Sedky ◽  
E. El-Suheel
Keyword(s):  
Comparative Study ◽  
Nonlinear Coefficient ◽  
Xrd Analysis ◽  
Breakdown Field ◽  
Doping Content ◽  
Leakage Currents ◽  
Electrical Conductivities ◽  
Zno Varistors ◽  
The Difference ◽  
Zno Ceramics

A comparative study between effects of Mn and Al on the properties of ZnO varistor sintered at 1200 is investigated by XRD, SEM hardness, and I-V measurements. Although both Mn and Al do not influence the well-known peaks related to wurtzite structure of ZnO ceramics, some other unknown peaks could be formed at higher doping content (). Also, the shape and size of grains are clearly different for both dopants. Average crystalline diameters, deduced from XRD analysis, are between 42 nm and 62 nm, which are 50 times lower than those obtained from SEM micrographs, while the oxygen vacancies deduced from EDAX analysis, are gradually decreased by doping content for both dopants. Interestingly, the values of breakdown field, nonlinear coefficient and barrier height are found to be higher in Mn samples as compared to Al samples, while the opposite is reported for leakage currents, hardness, and electrical conductivities. The values of are changed from 2.67 V/cm to 41.67 V/cm for Al, and from 1928 V/cm to 6571 V/cm for Mn. The conductivity of Al samples is higher than that of ZnO, and it is nearly (103–105) times the conductivity of Mn samples. These results are discussed in terms of the difference of magnetic moment and valence state between these two additives.

Strategies to Minimize Deburring Costs

1999 ◽  
Author(s):  
Jaramporn Hassamontr ◽  
David A. Dornfeld
Keyword(s):  
Decision Making ◽  
Process Planning ◽  
Burr Formation ◽  
Formation Mechanisms ◽  
Machining Parameters

Abstract A number of researchers have investigated burr formation mechanisms through careful observations and well thought-out experiments. The results of their studies help untangle underlying effects of key machining parameters on burr formation. However, so far, nobody has practically incorporated such knowledge into the area of process planning. The purpose of this paper is to develop general strategies to minimize deburring cost. Furthermore, it establishes basic decision making tools for efficient deburring planning.

Machining

2013 ◽  
pp. 213-270
Keyword(s):  
Electron Beam ◽  
Tool Wear ◽  
Electrical Discharge ◽  
Cutting Fluids ◽  
Machining Parameters ◽  
Machining Processes ◽  
Wire Cutting ◽  
Grinding Operations ◽  
Conventional Machining

Abstract This chapter covers the practical aspects of machining, particularly for turning, milling, drilling, and grinding operations. It begins with a discussion on machinability and its impact on quality and cost. It then describes the dimensional and surface finish tolerances that can be achieved through conventional machining methods, the mechanics of chip formation, the factors that affect tool wear, the selection and use of cutting fluids, and the determination of machining parameters based on force and power requirements. It also includes information on nontraditional machining processes such as electrical discharge, abrasive jet, and hydrodynamic machining, laser and electron beam machining, ultrasonic impact grinding, and electrical discharge wire cutting.

Investigation of the Dynamics of Microend Milling—Part I: Model Development

2006 ◽  
Vol 128 (4) ◽  
pp. 893-900 ◽  
Author(s):  
Martin B. G. Jun ◽  
Xinyu Liu ◽  
Richard E. DeVor ◽  
Shiv G. Kapoor
Keyword(s):  
Cutting Force ◽  
Chip Formation ◽  
Model Development ◽  
Chip Thickness ◽  
Fault System ◽  
Formation Mechanisms ◽  
Force Model ◽  
Line Field ◽  
Fault Parameters ◽  
Microend Milling

In microend milling, due to the comparable size of the edge radius to chip thickness, chip formation mechanisms are different. Also, the design of microend mills with features of a large shank, taper, and reduced diameter at the cutting edges introduces additional dynamics and faults or errors at the cutting edges. A dynamic microend milling cutting force and vibration model has been developed to investigate the microend milling dynamics caused by the unique mechanisms of chip formation as well as the unique microend mill design and its associated fault system. The chip thickness model has been developed considering the elastic-plastic nature in the ploughing process. A slip-line field modeling approach is taken for a cutting force model development that accounts for variations in the effective rake angle and dead metal cap. The process fault parameters associated with microend mills have been defined and their effects on chip load have been derived. Finally, a dynamic model has been developed considering the effects of both the unique microend mill design and fault system and factors that become significant at high spindle speeds including rotary inertia and gyroscopic moments.

Electrical Properties of ZnO-Bi2O3 Metal Oxide Heterojunction — A Clue of a Role of Intergranular Layers in ZnO Varistors

1981 ◽  
Vol 5 ◽  
Author(s):  
Kazuo Eda
Keyword(s):  
Thin Film ◽  
Electrical Properties ◽  
Metal Oxide ◽  
Oxide Thin Film ◽  
Thin Film Thickness ◽  
Metal Oxide Thin Film ◽  
Zno Varistors ◽  
Current Characteristics ◽  
Zno Ceramics

ABSTRACTZinc Oxide (ZnO) Ceramics-Bismuth Oxide (Bi2O3) Metal Oxide thin film heterojunction made by sputtering technique showed a highly non-Ohmic property. The voltage-current characteristics and the dielectric properties showed dependence on Bi2O3 metal oxide thin film thickness.In this paper after reviewing and discussing the electrical properties of ZnO varistors, the role of intergranular layers in the ZnO varistor is discussed based on experimental results with the heterojunction.

Recent Development of Abrasive Water Jet Machining Technology

2006 ◽  
Vol 315-316 ◽  
pp. 396-400 ◽  
Author(s):  
Chuan Zhen Huang ◽  
Jun Wang ◽  
Yan Xia Feng ◽  
Hong Tao Zhu
Keyword(s):  
Abrasive Waterjet ◽  
Thermal Distortion ◽  
Abrasive Water Jet ◽  
Cutting Mechanism ◽  
Abrasive Water Jet Machining ◽  
Abrasive Waterjet Machining ◽  
Machining Force ◽  
Waterjet Machining ◽  
Conventional Machining ◽  
Research Situation

Abrasive waterjet (AWJ) machining is a new non-conventional machining technology. Compared with other conventional and non-conventional machining technologies, AWJ offers the following advantages: no thermal distortion, small machining force, high machining versatility, etc. Therefore this technology is regarded as a high potential technology in the field of machining difficult-to-cut materials. In this paper, a comprehensive review of research situation about the cutting performance, the cutting mechanism and the measures to improve the cutting quality is given. The application of abrasive waterjet machining in turning, milling and drilling is reviewed finally.

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