Mechanical Engineering

Coated carbide inserts are considered vital components in machining processes and advanced functional surface integrity of inserts and their coating are decisive factors for tool life. Atomic Force Microscopy (AFM) implementation has gained acceptance over a wide spectrum of research and science applications. When used in a proper systematic manner, the AFM features can be a valuable tool for assessment of tool surface integrity. The aim of this paper is to assess the integrity of coated and uncoated carbide inserts using AFM analytical parameters. Surface morphology of as-received coated and uncoated carbide inserts is examined, analyzed, and characterized through the determination of the appropriate scanning setting, the suitable data type imaging techniques and the most representative data analysis parameters using the MultiMode AFM microscope in contact mode. The results indicate that it is preferable to start with a wider scan size in order to get more accurate interpretation of surface topography. Results are found credible to support the idea that AFM can be used efficiently in detecting flaws and defects of coated and uncoated carbide inserts using specific features such as ―Roughness‖ and ―Section‖ parameters. A recommended strategy is provided for surface examination procedures of cutting inserts using various AFM controlling parameters.

Hardness homogeneity of the commonly used structural ferrous and nonferrous
engineering materials is of vital importance in the design stage, therefore, reliable
information regarding material properties homogeneity should be validated and any
deviation should be addressed. In the current study the hardness variation, over wide
spectrum radial locations of some ferrous and nonferrous structural engineering materials,
was investigated. Measurements were performed over both faces (cross-section) of each
stock bar according to a pre-specified stratified design, ensuring the coverage of the entire
area both in radial and circumferential directions. Additionally the credibility of the
apparatus and measuring procedures were examined through a statistically based
calibration process of the hardness reference block. Statistical and response surface
graphical analysis are used to examine the nature, adequacy and significance of the
measured hardness values. Calibration of the apparatus reference block proved the
reliability of the measuring system, where no strong evidence was found against the
stochastic nature of hardness measures over the various stratified locations. Also, outlier
elimination procedures were proved to be beneficial only at fewer measured points.
Hardness measurements showed a dispersion domain that is within the acceptable
confidence interval. For AISI 4140 and AISI 1020 steels, hardness is found to have a slight
decrease trend as the diameter is reduced, while an opposite behavior is observed for AA 6082 aluminum alloy. However, no definite significant behavior was noticed regarding
the effect of the sector sequence (circumferential direction).

In forming processes, metal is usually subjected to multi-stages of deformation. In order to process one stage eectively, actual information in terms of mechanical and forming properties of the preceding stage should be available to start with.

Strain hardening or, cold work hardening, usually accompanies most forming manufacturing processes as also for many other processes. This inevitable consequences is, in a common functional sense, is undesirable from design and application safety points of views. Therefore, attempts are always being in progress to enhance the predeformed material in such a way to reduce such hardening effect. Annealing heat treatment is always one of the familiar effective techniques frequently employed. In the current work, two annealing methods are used separately to investigate their effect on the predeformed materials. These are the stress relief at 610 C° and the process annealing at 710 C°. Both techniques have enhanced the resulting hardening stress to different extents, depending on the degree of deformation and the value of true strain. Stress relief annealing tends to have the best outcome at the moderate deformation levels from 0.12 to 0.16 predeformation strain. However, little gain is obtained at higher levels especially at moderate to high true strain values. Process annealing is found to produce better qualitative and quantitative results than those obtained by stress relief annealing. Stress reduction has been achieved due to the process annealing within a wider domain of predeformation and true strain. However, the process annealing usually takes longer time and uses more facilities and, consequently higher manufacturing cost and, it is up to the designer to justify the selected annealing methods according to the functional manufacturing objectives and constraints imposed. It is one of our objectives to assist designer and decision makers taking the practical decision through the offered numerical database charts that are produced in forms of empirical equations together with 3-d plots and contours.

The importance of machining process in today’s industry requires the establishment of more practical approaches to clearly represent the intimate and severe contact on the tool-chip-workpiece interfaces. Mathematical models are developed using the measured force signals to relate each of the tool-chip friction components on the rake face to the operating cutting parameters in rough turning operation using multilayers coated carbide inserts. Nonlinear modeling proved to have high capability to detect the nonlinear functional variability embedded in the experimental data. While feedrate is found to be the most influential parameter on the friction coefficient and its related force components, both cutting speed and depth of cut are found to have slight influence. Greater deformed chip thickness is found to lower the value of friction coefficient as the sliding length on the tool-chip interface is reduced.