Izman Sudin

Roughness models for sanded wood surfaces

The understanding of the effects of variables is crucial to achieve the desired sanded surface quality at optimum condition. In wood surface evaluation, it is known that anatomies on wood surface could distort the roughness value and cause a misinterpretation of the processing performance. In this study, statistical approaches were taken to characterize the influence of sanding variables as well as to analyze the anatomical noises that were inherited from intra- and inter-species of woods. Four available roughness parameters (Ra, Rq, Rk and Rap) were used to examine the surface of three distinct wood species, viz. kembang semangkok, red oak and spruce in wide-belt sanding. Based on the mean values, analysis of variance showed that species (anatomy) was significant to all conventional parameters except Rap which was filtered by monitoring the second derivative of Abbott-curve. In spite of this, Rap recorded a more widely dispersed deviation of random measurement values than Rk and Ra. The effects of grit size and feed rate were found to be significant. Empirical roughness models were established using response surface methodology, and the errors were calculated by comparing the model values to all the randomly measured values. Although exhibiting slight species-dependant effect by nature, Rk showed reliable consistency by recording the lowest error values (<10%) for both intra- and inter-species measurements. Experimental results also suggested that three random measurements at each run could be sufficient. The method of constructing machinability models can be readily applied in the industry as a quality control tool for wide-belt sander.

Preparation Methods for Improving PEEK’s Bioactivity for Orthopedic and Dental Application:A Review

There is an increased interest in the use of polyether ether ketone (PEEK) for orthopedic and dental implant applications due to its elastic modulus close to that of bone, biocompatibility, and its radiolucent properties. However, PEEK is still categorized as bioinert due to its low integration with surrounding tissues. Many studies have reported on methods to increase the bioactivity of PEEK, but there is still one-preparation method for preparing bioactive PEEK implant where the produced implant with desirable mechanical and bioactivity properties is required. The aim of this review is to present the progress of the preparation methods for improvement of the bioactivity of PEEK and to discuss the strengths and weaknesses of the existing methods.

Surface Roughness Study of Milled Carbon Fiber Reinforced Polymer (CFRP) Composite Using 4 mm 2-Flute Titanium Aluminum Nitride (TiAlN) Coated Carbide End Mills

As the goal for aircraft weight reduction and low fuel consumption becomes a dire concern in aerospace industries, there is driving desire for the increasing use of advanced exotic materials such as composites, titanium and Inconels in the aerospace industry because of their high strength to weight ratio. Nevertheless the inherent anisotropy, inhomogeneous properties of CFRP and low bonding strength within the laminates make machining of these composite materials results in several undesirable effects such as delamination, micro-cracking, burr, fiber pull out and breakage. This paper discusses an experimental investigation into the influence of machining parameters on surface roughness when milling CFRP using 4 mm-diameter 2-fluted carbide end-mill coated with Titanium Aluminium Nitride (TiAlN). Relationship between the machining variables and the output variables is established and a mathematical model is predicted for the surface roughness produced during the milling process for the machining conditions investigated.

Mathematical Modeling of Cutting Force in Milling of Medium Density Fibreboard Using Response Surface Method

This paper reports on the development of predicted mathematical model for cutting force (Fc) during side milling of medium density fiberboard (MDF) using uncoated carbide insert. Box-Behnken design (BBD) of experiment, coupled with response surface method (RSM) were employed to establish the cutting force model. Evaluation on the effects and interactions of the machining variables on the cutting force were carried out. The machining variables involved include spindle speed, feed rate, routing width and were denoted by A, B and C respectively. Statistical analysis conducted on the experimental results indicated that the mathematical model for cutting force was adequate within the limits of factors being investigated. After eliminating the insignificant factors or model terms in the reduced model, it was found that factors A, B, C, B2 (second order of B), C2 (second order of C), were the most significant factors affecting the cutting force. BC (interaction of B and C) and AC (interaction of A and C) are the subsequent significant factors. Three-dimensional plots displaying the interactions between these significant factors were presented. The reduced model was then verified experimentally and statistically using ANOVA. It was evident that Box-Behnken design proved to be an efficient tool in identifying and constructing maps of interactions between the significant factors. Experimental results showed that lower cutting force can be obtained by employing higher cutting speed, low feed rate and lower routing width when side milling MDF using uncoated carbide insert.

In situ synthesis of hydroxyapatite-grafted titanium nanotube composite

ABSTRACT The present study is an investigation to demonstrate the effectiveness of in situ approach in the synthesis of hydroxyapatite-grafted titanium nanotube composite (HA-TNT). This method involves combining the process of HA sol–gel and rapid breakdown anodisation of titanium in a novel solution consisting of NaCl and N3PO4. This new synthesis approach produced a uniform dispersion of Anatase and Rutile phases of TiO2 nanotubes with minimal agglomeration in the matrix of crystalline HA. The characterisation of homogenised HA-TNT composite was investigated via field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM) and X-ray diffraction (XRD). FESEM and TEM images indicated the nanostructure of composite with TiO2 nanotube diameter of approximately 10 nm. XRD and EDS analyses confirmed the formation of HA crystalline with the Ca/P ratio of 1.58 and formation of Anatase and Rutile phase of TiO2 nanotubes.

Effect of Carburization Process on Adhesion Strength of Ti Carbide Layer on Titanium Alloy Substrate

Titanium alloys are commonly used in biomedical application in hard tissues replacement especially for knee and hip implants. Surface modifications are required prior to diamond coating process for improving tribological and wear properties of the titanium alloy. In this study, experiments were carried out to investigate the effects of different carburizing times on the adhesion strength of carbide layer formed on the Ti-6Al-7Nb. Prior to carburization process, all samples were treated to remove residual stress and oxide scales by annealing and pickling processes respectively. Hard wood charcoal powder was used as a medium. The carburizing process was carried out for 6, 12 and 24 hours at 950 °C under normal atmospheric condition. Surface morphology, carbide layer thickness and adhesion strength were evaluated using SEM, XRD, 3D Surface Profilometer and Blast Wear Tester (BWT). It is found that a mixture of oxide and carbide layers formed on the substrate and the thickness of these layers increases with carburizing time. It is also revealed that the 24 hr carburizing time provides the strongest adhesion strength among the three and TiC as the dominant layer.

Thermal-Mechanical Responses of Ti-6Al-4V during Orthogonal Cutting Process

Orthogonal metal cutting process involves large plastic deformation accompanied by excessive heat generation. This work addresses the thermal-mechanical responses of the workpiece material at the tool-workpiece contact. In this respect, the orthogonal cutting process of Ti-6Al-4V using CVD diamond tool is simulated using finite element method. The cutting condition consists of cutting speed, V=180 m/min, feed rate, t=0.125 mm/rev and width of cut of 1.25 mm. Eulerian formulation with coupled thermal-mechanical analysis is employed in the model. The Johnson- Cook constitutive equation is employed for Ti-6Al-4V workpiece material to accurately simulate the formation of shear bands. The stick-slip friction condition is modeled at the tool-chip interface. The sliding coefficient of friction of 0.8 and the limiting shear stress of 700 MPa for stick-slip condition are determined experimentally. Results show that high temperature and temperature gradient concentrate in the primary shear zone and the contact area between the tool rake face and the chip. A primary shear band is predicted in the workpiece ahead of the tool-workpiece contact face while the secondary shear band is formed in the chip. This highly-deformed shear band is revealed in the microstructure of etched chips. The predicted high strain rate results in build-up edge at tool cutting edge-chip contact. Low cutting condition of V=150 m/min, t=0.125 mm/rev promotes stagnant zone formation that helps preserve the cutting edge of the tool. The maximum predicted temperature at the cutting edge is in excess of 700 °C. Such high temperature level facilitates diffusion of carbon elements into the chips and conversely, elements of titanium into the CVD diamond tool.

Enhancement of the Mechanical Properties of Hydroxyapatite/Sulphonated Poly Ether Ether Ketone Treated Layer for Orthopaedic and Dental Implant Application

The mechanical properties of coated layers are one of the important factors for the long-term success of orthopeadic and dental implants. In this study, the mechanical properties of the porous coated layer were examined via scratch and nanoindentation tests. The effect of compression load on the porous coated layer of sulphonated poly ether ether ketone/Hydroxyapatite was studied to determine whether it changes its mechanical properties. The water contact angle and surface roughness of the compressed coated layer were also measured. The results showed a significant increase in elastic modulus, with mean values ranging from 0.464 GPa to 1.199 GPa (p<0.05). The average scratch hardness also increased significantly from 69.9 MPa to 95.7 MPa after compression, but the surface roughness and wettability decreased significantly (p<0.05). Simple compression enhanced the mechanical properties of the sulphonated poly ether ether ketone/hydroxyapatite coated layer, and the desired mechanical properties for orthopaedic and dental implant application can be achieved.

Influence of homogenization treatment on the degradation behavior of Zn–3 Mg alloy in simulated body fluid solution:

This paper reports a degradation study of Zn–(3 wt%) Mg alloy proposed for biodegradable medical implants. The alloy was cast from high-purity raw materials and homogenized at 370 ℃ for 15 h under vacuum and water quenched. The effect of homogenization on microstructure and degradation behavior in simulated body fluid was investigated. Results showed that homogenization transformed the star-like dendritic Zn-rich shape into a network of precipitate phase along eutectic colony and dispersed Mg2Zn11 phase. The homogenized alloy showed higher degradation resistance compared to the as-cast alloy, pure Zn, and pure Mg samples. The relationship between microstructure and degradation behavior discussed further in this paper.

Effect of Cold Rolling Treatment on the Formation of Titanium Oxide Layer on Ti6Al4V Alloys by Thermal-electrochemical Anodizing Processes

The present work concerns on preparing suitable titanium alloy substrate that might induce better characteristic of titanium oxide layer on the substrate. Different degree of cold rolling treatments were applied on Ti6Al4V alloy before thermal-electrochemical anodizing processes. The later processes were performed to produce titanium oxide layer which combines thermal process by heat treatment and followed with electrochemical anodizing process. After thermal heat treatment process, it was observed more homogeneous titanium oxide layer for the samples given cold rolling treatment as compared with sample without the treatment. This condition is believed due to the finer substrate surface after cold rolling treatment as observed from surface roughness measurement. Similar situation was observed after anodizing process that irregular oxidized layer was observed for sample without cold rolling treatment, whereas more homogenous layer was observed for sample with cold rolling treatment. Except for sample without cold rolling treatment, anodizing treatment tends to create finer oxidized layer. Therefore, it can be concluded that cold rolling treatment on titanium substrate before oxidizing process induces the formation of homogeneous oxide layer, whereas additional anodizing process create finer titanium oxide layer.