Rahmat Azmi

FAILURE ANALYSIS OF CRANE WIRE ROPE

A failure analysis of a broken multi strand wire rope from an offshore platform crane was performed. The wire rope was operated for less than 5 years. The wire consists of seven strands, one central strand and six strands around it. The diameter of the small wires was about 0.78-0.94 mm and the larger wires was a round of 1.52 - 1.78 mm. The large size wires were found fractured by cyclic torsional stresses as characterized by the presence of fatigue cracking originating from the outer surface of the wire. Meanwhile the smaller wires were fractured in a ductile manner under excessive load after the larger wire broken out due to the fatigue mechanism.

Effects of Cobalt Addition and Temperature on Microstructure and Density of W-25Cu Composites Prepared via Liquid Infiltration

In this study, the effect of Co and sintering temperature on microstructure of W-25Cu composites prepared via copper melt infiltration has been investigated. The concentration of Co addition used ranged from 0.5 to 3wt. %. The infiltration temperatures were performed at 1150°C and 1250°C for 2 hr under vacuum. The microstructure and sintering density of W-25Cu composites are discussed. Results indicated that, the relative density (RD) and microstructure of W-25wt. % Cu were greatly affected by the addition of low Co concentration and sintering temperature. The concentration of 3 wt. % Co to tungsten-copper compact and infiltration temperature of 1250°C give high sintering density of 98.6% theoretical density (TD). The concentration of Co and infiltrating temperature have strong effects on the densification of W-Cu composite materials. The sintered compact microstructures and density were obtained using scanning electron microscope (SEM) coupled with EDX and Archimedes technique respectively.

The Development and Characterisation of Porous Clay - Precipitated Calcium Carbonate

Ceramic foams, a porous material with a gyroid structures, are becoming highly demanded for various applications such as heat insulation, bone implantation and filtration, because of their unique properties such as high specific surface area, high porosity and low heat transfer rate. In this study, the development of ceramic foam utilised white clay with a combination of precipitated calcium carbonate (PCC). The ceramic foam was successfully developed using this combination after the sample was sintered at 1250 °C for 2 hours holding time. The various compositions of PCC (10.0, 12.5, 15.0, 17.5, 20.0, 22.5 and 25.0 wt.%) affected the chemical composition and compressive strength of the ceramic foam. The chemical composition of ceramic foam was analysed by using X -ray fluorescence (XRF) and the result indicated that the PCC was successfully transformed into calcium oxide (CaO) after the sintering process. The mineralogical composition of the ceramic foam was evaluated using X-ray diffraction (XRD) and has shown the presence of mullite (3Al2O3.2SiO2), gehlenite (Ca2Al2SiO7) and anorthite (2CaAl2Si2O8) after the sintering process. The scanning electron microscope (SEM) analysis showed that the presence of porosity on the strut of the ceramic foam. Meanwhile, the compressive strength of the ceramic foam increased from 0.03 to 1.31 MPa, which is directly proportional to the increased amount of PCC.

The investigation of physical and mechanical properties of porous anorthite ceramics using statistical analysis

In this present study, the porous anorthite ceramics were prepared from white clay and precipitated calcium carbonate via polymeric foam replication method. The effects of various precipitated calcium carbonate additions (0, 10, 15, and 25 wt.%) on the properties of porous anorthite ceramics have been studied. The main phase that revealed after the additions of 20 and 25 wt.% of precipitated calcium carbonate was anorthite (CaO·Al2O3·2SiO2). The porosity of the porous anorthite ceramics was increased (from 67 to 77 percent) with the increasing amount of precipitated calcium carbonate. Meanwhile, the density of the porous anorthite ceramics was increased (from 0.463 to 0.703 g/cm3) with the increasing amount of precipitated calcium carbonate. The flexural strength of porous anorthite ceramics consisting of predominantly anorthite phase are ranged from 0.24 to 1.23 MPa. Finally, the correlation between the flexural strength on the foam density has been studied. The flexural strength was increased when the f...

Reactions of Limestone on the Slaking Process under Different Conditions of Parameters

The reaction of limestone in the slaking process has been studied under different conditions of parameters such as calcination times, soaking times and particle sizes. The reactivity of quicklime was determined by recording temperature rise and the rate of temperature rise during the slaking process. The obtained ‘milk of lime’ is characterized using instrumental measurements such as X-ray fluorescence (XRF) to identify the chemical composition that exists in the sample. In this paper, the quicklime used during slaking test indicates the differential of temperature pattern which influences by quicklime particle sizes, calcination temperatures and soaking times. Results indicate that the optimum and efficient distribution of heat transfer and thermal decomposition onto quicklime can be obtained by calcining at 1100 °C with 60 minutes of soaking time samples which produced a highly porous structure towards higher reactivity of quicklime.

The Electrical Resistivity of Geopolymer Paste by Using Wenner Four Probe Method

This paper presents an experimental study of the electrical resistivity of geopolymer paste by using a non-destructive test employing Wenner four probe method. Geopolymer is produced from a combination mixture of aluminosilicate materials which is rich in Si and Al such as fly ash with an alkaline activator. Geopolymer paste in this study was made from a mixture of class F fly ash, sodium hydroxide (NaOH) solution and sodium silicate (Na2SiO3) solution. An alkaline activator was prepared 24 hrs prior to use with the ratio mixture of Na2SiO3/NaOH being 2.5. Then, the prepared alkaline activator was mixed with the fly ash for about 30 minutes. After that, the mixture was placed in a 100 mm x 103 mm x 495 mm mould. After 24 hrs, the sample was taken out from the mould and cured at 60°C in the oven for 24 hrs. The sample was then tested after 7, 14 and 28 days. The current applied in this study was from 0.01 mA to 1.00 mA and the electrode spacing used were 0.02 m, 0.04 m, 0.06 m, 0.08 m and 0.10 m. The results showed that the geopolymer paste after 28 days with the current of 0.01 mA and 0.10 m electrode spacing showed the highest resistivity with 61575 Ω.m while the geopolymer paste after 7 days with 0.95 mA and 0.02 m electrode spacing showed the lowest resistivity with 537 Ω.m. Hence, the corrosion rate of geopolymer paste in this study was negligible and if occur, was very low.

Densification Behavior and Hardness Evaluation of Consolidated W-25Cu Composite Powder by Re-Compaction Method

In this work, one stage and two stages compaction technique were used to fabricate the tungsten-copper composite powder. Liquid infiltration technique was used to consolidate the W-Cu green compact and a low concentration iron powder was added as activation material to enhance the sintering behavior. In addition, two-steps compaction process was developed for improving mechanical properties of W-Cu composite as well as segregation of Fe around W grain. The green compact was directly infiltrated at 1250 °C for about 2 hours under vacuum conditions. The microstructure, inter-boundary layer and the contamination levels of the infiltrated compacts were characterized using the scanning electron microscope (SEM) and the energy dispersive X-ray analysis (EDX). Relative sintering density varied in the range of 97.1 to 99.3 % of theoretical density, and it was highly depended on Fe concentration and method of compaction. In contrast to one stage compaction, the experimental results showed that the composites fabricated by the two stages of compact ion had better homogeneous structure, high densification and a clear segregation of inter-boundary layer of Fe-W around W grains.

Development of dense hydroxyapatite-ni by modified electroless deposition technique.

Ni deposited on HA powder was prepared by electroless plating process without sensitization and activation treatment. The deposited powder obtained was characterized by energy dispersive spectroscopy (EDX) and x-ray diffraction (XRD). The microstructure and hardness of the sintered powder were examined by scanning electron microscopy (SEM) and Vickers hardness respectively. From the result, the nickel existence in the deposition was confirmed by the EDX analysis. The diffraction peaks at 44.5 and 64.7o (2θ) of planes (111) and (211) respectively were belong to nickel. Nickel are homogeneously dispersed in HA matrix with grain size between 0.25-2μm after sintered at 1250°C. The improvement of 93% and 180% in average hardness and flexural strength respectively were achieved with nickel presence in HA compared to pure HA.

Comparison of Liquid Phase Sintering and Cu-Melt Infiltration Methods to Consolidate 80W-Cu Composite Using Nickel as Sintering Activator

In this article, studies were conducted to evaluate the densification of W-Cu sintered compacts produced using two methods; liquid phase sintering (LPS) and combination of liquid phase sintering and liquid infiltration technique (LPS+LI) named Cu-melt infiltration (Cu-MI). Low concentration of nickel (1wt.%) was used to activate the sintering process in both methods. Isothermal sintering was carried out in alumina tube furnace at temperatures of 1150°C for 2 hr. under H2/Ar. as protective gas. The infiltration (Cu-MI) method proved to be effective in the densification, microstructure and hardness enhancement of the 80W-Cu compact as opposed to the other conventionally liquid phase sintered compacts. The relative densities of 80W-Cu-1Ni composites prepared by using insert method (Cu-melt infiltration) achieved 96.22% of theoretical density.

The Influence of Deposition Temperature on the Morphology and Corrosion Resistance of Zinc Phosphate Coating on Mild Steel

The influence of phosphating temperature on the surface morphology and corrosion resistance of zinc phosphate coatings on mild steel was investigated. The phosphate layers were deposited on steel from phosphating bath at different temperatures (45 ~ 75 C). The surface morphology and composition of phosphate coatings were investigated via scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). The corrosion resistance of the coatings was evaluated by polarization curves (anodic and cathodic) in an aerated 3.5% NaCl solution. The results showed that the increase in temperature of the phosphating bath up to 55 C caused an increase in surface coverage and in turn resulted in better corrosion resistance. At high temperature (65 °C and 75 °C) the deposition coverage decreased indicating that the best coverage for the phosphate layer on the metal surface was achieved at 55 °C