ORCID Profile
0000-0003-4525-2685
Current Organisations
Universiti Teknologi Brunei,
,
Ton Duc Thang University
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Publisher: Trans Tech Publications, Ltd.
Date: 06-2011
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.264-265.997
Abstract: Silicon being a typical hard-brittle material is difficult to machine to a good surface finish. Although ductile-mode machining (DMM) is often employed to machine this advanced material but this technique requires the use of expensive ultra-precision machine tools therefore limiting its applicability. However, by proper selection of grinding parameters, precision grinding which can be performed on conventional machine tools can be used to generate massive ductile surfaces thereby reducing the polishing time and improving the surface quality. Precision grinding should be planned with reliability in advance and the process has to be performed with high rates of reproducibility. Therefore, this study investigated the effect and optimization of grinding parameters using Taguchi optimization technique during precision grinding of silicon. Experimental studies were conducted under varying depths of cut, feed rates and spindle speeds. An orthogonal array (OA), signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) were employed to find the minimum surface roughness value and to analyze the effect of the grinding parameters on the surface roughness. Confirmation tests were carried out in order to illustrate the effectiveness of the Taguchi method. The results show that feed rate mostly affected the surface roughness. The predicted roughness (Ra) of 34 nm was in agreement with the confirmation tests. Massive ductilestreaked surface was also found corresponding to the minimal surface finish determined from the optimal levels.
Publisher: Elsevier BV
Date: 2021
Publisher: Springer Science and Business Media LLC
Date: 23-06-2011
Publisher: AIP Publishing
Date: 2023
DOI: 10.1063/5.0110440
Publisher: Elsevier BV
Date: 08-2019
DOI: 10.1016/J.JMBBM.2019.04.027
Abstract: This paper applied non-linear theory of elasticity (NLTE) to partition indentation-induced deformations into elasticity and plasticity for lithium metasilicate glass ceramic (LMGC), sintered and pressed lithium disilicate glass ceramics (SLDGC and PLDGC). It also used elastic plastic fracture mechanics (EPFM) approach to analytically predict machinability for these materials. Using the Sakai's series elastic and plastic deformation model that applied NLTE, the resistances to plasticity for LMGC, SLDGC and PLDGC were extracted from their respective indentation-extracted plane strain moduli and contact hardness values. Plane strain moduli and resistances to plasticity were used to calculate elasticity and plasticity for these materials. Furthermore, the EPFM approach in the Sakai-Nowak model was applied to deconvolute resistances to machining-induced cracking for these materials. All properties were extracted at 10 mN peak load and 0.1-2 mN/s loading rates to determine the loading-rate influence on these properties. The resistances to plasticity of LMGC and SLDGC were loading rate dependent (ANOVA, p 0.05). The strain rate sensitivity model was used to find the intrinsic resistances to plasticity for LMGC and SLDGC. The elastic displacement/deformation components were dominant for LMGC at all loading rates. For SLDGC and PLDGC, the deformation mechanisms were dynamic with the plastic and elastic deformation components dominating at low loading and high loading rates respectively, a phenomenon attributed to indentation energies. The decrease in plastic displacements for all materials with increase in loading rate was due to the strain hardening behaviour. Also, PLDGC revealed the highest absorbed energy followed by SLDGC and LMGC. Finally, PLDGC had the highest resistance to machining-induced cracking followed by SLDGC and LMGC. This study provides a quantitative basis to rank materials in terms of brittleness, ductility and resistance to mechanically-induced cracking.
Publisher: AIP Publishing
Date: 2023
DOI: 10.1063/5.0110351
Publisher: Inderscience Publishers
Date: 2011
Publisher: Trans Tech Publications, Ltd.
Date: 06-2011
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.264-265.1702
Abstract: Conventional diamond cutting of ferrous materials is rarely economical due to the rapid tool wears which result from diffusion and graphitization of the tools. Conventional machining of hard-brittle materials like silicon and germanium results in surface and subsurface damage due to their brittle fracture. Although ductile mode machining (DMM) concept can be used to have a flawless machining on these materials but the mirror surfaces can only be realized on expensive ultraprecision machine tools because the critical depth of cut must be on the order of 1μm or less. Furthermore, there is a need to eliminate or reduce the use of cutting fluids during machining due to their attendant ecological hazards. However, grinding is one of the most difficult processes with regard to eliminating cutting fluids. Vibration assisted machining (VAM) can be used to minimize the problems enumerated above. VAM combines precision machining with small- litude tool vibration to improve the fabrication process. It has been applied to a number of processes ranging from turning, drilling to grinding. Therefore, this paper discusses DMM, the general overview of VAM, the basic kinematics of one-dimensional VAM the advantages derived from using VAM and the ability of VAM to machine brittle materials in the ductile regime at increased depth of cut are described. Finally, the research directions in VAM are outlined.
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 12-2021
Publisher: IOP Publishing
Date: 08-2022
Abstract: Polymer-infiltrated zirconia-ceramic composite (PIZC) comprises a pre-sintered zirconia-ceramic matrix and a polymer. In this work, pre-sintered zirconia-ceramic was infiltrated with varied amounts of methacrylate-based polymer. Therefore, this paper reports the effect of polymer amount on the mechanical behavior of PIZC at 1100 °C–1300 °C pre-sintering temperatures. Conventional mechanical tests were performed to obtain the elastic modulus and fracture toughness while Vickers micro-indentations were employed to extract the Vickers hardness. Advanced mechanical behaviour analysis was characterized by plastic deformation resistance, elastic and plastic deformation components and brittleness index. Increasing the amount of polymer from 0 to 42% led to the corresponding decrease in elastic modulus, hardness and fracture toughness by at least 78, 85 and 75%, respectively. As the temperature was increased, both elastic modulus and hardness increased while the fracture toughness initially increased but decreased at higher temperature. Mechanical properties and polymer amount were well modelled by connected-grain models which usefully explained the densification process occurring at higher temperatures. Plastic deformation resistance and component and brittleness index confirmed better plastic properties for PIZC at higher polymer amounts and lower temperature. Therefore, in order to utilize the plastic properties of PIZC during the CAD/CAM process, these findings recommended the processing of PIZC at not-lower-than 26% polymer amount and 1100 °C, which could greatly facilitate its precision ductile machining mode realization. Finally, the results provide a technical guidance for the selection of appropriate polymer amount when fabricating dental restorations from this novel ceramic-composite.
Location: No location found
Location: Saudi Arabia
Location: Malaysia
No related grants have been discovered for Abdur-Rasheed Alao (CEng MIMechE, MASME).