Gul Tosun

The drilling of an Al/SiCp metal-matrix composites. Part I: microstructure

Automotive, aircraft and train companies need to replace steel and cast iron in mechanical components with lighter high strength alloys like Al metal matrix composites (MMC). Despite the superior mechanical and thermal properties of particulate metal matrix composites, their poor machinability is the main deterrent to their substitution of metal parts. Machining is a material removal process and therefore is important for the final fabrication stage prior to application. Consequently the development of effective machining methods, leading to a reduction in the overall cost of components, is one of the major challenges yet to be solved. In this study, the influence of the type of drills, point angles of drills and ageing on the drilling performance of 2124 aluminum alloy reinforced with 17% SiC particulates was investigated experimentally. The workpiece material was drilled in four heat treatment conditions: as-received, solution treated, and solution treated and aged for 4 and 24 h. The experimental studies were conducted under different settings of spindle-speed and feed rate and point angles of drill. Drilling tests were carried out using high-speed steel (HSS), TiN coated HSS and solid carbide drills. The drills used were 5 mm diameter. The experimental results indicated that, the effect of point angles on the sub-surface damage caused by the drilling operation was changed with the type of drills.

Analysis of Process Parameters for Porosity in Porous NiTi Implants

This article presents optimization of process parameters for the porosity in NiTi alloy produced as implant material by self-propagating high-temperature synthesis (SHS) method. The experiments were conducted under the different process parameters, namely, compaction pressure, preheating temperature, and heating rate. A plan of experiments based on the Taguchi method was designed. The level of importance of the process parameters is determined by using analysis of variance (ANOVA). The optimum process parameter combination was obtained by using the analysis of signal-to-noise (S/N) ratio. Through statistical analysis of response variables and S/N ratios, the determined significant factors were the heating rate and pressure. By using regression analysis method, the variation of the porosity in the implant with production parameters is mathematically modeled.

Synthesis and characterization of hydroxyapatite powders from eggshell for functional biomedical application

Apatitic phosphates are considered within the category of bioceramics. HA and its derives are used of in the fields of medicine, orthopedics and dentistry in order to support a grow up of new bone cells. HA structures have a high biocompability and are widely in biomedical applications. On the other hand, synthesis of HA structures necessitates complex technologies (microwave sintering, hydrothermal synthesis etc.) and their production costs high. This study aims the production of nano apatitic structures with great biocompability from a natural material. Simple hotplate method was used to obtain natural, nano scale HA from eggshells. After calcination and sintering processes at different temperatures, the obtained apatitic phosphate powders have been structurally characterized by infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Morphological investigation has been conducted by FEG-SEM images. Biological investigations have been carried out for the produced nanosized bioceramics and the results reveal that these nanomaterials are promising for tissue engineering purposes.