Advanced Materials Research Vol. 974

Abstract: In orthopedic surgery, it is easy to do harm to surrounding tissues, so the study of bone cutting is necessary. In this article, a finite element model (FEM) of orthogonal bone cutting is developed. Cutting force intra-operatively can provide the surgeon with additional on-line information to support him to control quality of cutting surface. The obtained cutting force decreased little with cutting speed increasing, but ascended evidently with cutting depth increasing. The results of finite element simulations are aimed at providing optimization of cutting parameters and the basic information for hybrid force-velocity control of a robot-assisted bone milling system.

Abstract: Cratoxylum formosum is a plant widely distributed in mountainous area of various Asian countries. The extract prepared from the burnt bark has been used among the local people as a varnish to prevent tooth decay and other oral diseases. The aim of this study was to examine antifungal activity of C. formosum gum against Candida albicans and to evaluate its cytotoxicity. The gum prepared from the extract of C. formosum was investigated for antimicrobial activity against 3 strains of C. albicans. Inhibition of microbial growth was primarily tested by agar diffusion method. A two-fold broth dilution method was then used to determine the minimum inhibitory concentration (MIC) of the gum. Based on the MIC value, cytotoxicity test was performed on mouse fibroblasts (ATCC clone 929) using agar overlay technique. Inhibitory effect of the gum was seen against C. albicans with zones of inhibition ranging from 8.0 to 9.3 mm. MIC values were between 0.50 and 1.25 mg/mL. In term of cytotoxicity, C. formosum gum at the concentration of 20 MIC (25 mg/mL) was classified as grade 3 (moderate cytotoxicity) whereas those of 10 MIC and 1 MIC were grade 1 (slight cytotoxicity). In conclusion, the gum prepared from C. formosum extract exhibited antimicrobial activities against all the test strains of C. albicans. From the present study, it can be suggested that this plant can be used as a novel antifungal agent, effective against C. albicans infections, due to its inhibitory effects on C. albicans and acceptable biocompatibility. Further in vitro/in vivo studies should be conducted to understand the mechanisms of action and to establish the safe profile of this gum for clinical usage.

Abstract: Auxetic solids are materials that exhibit negative Poisson’s ratio. This paper evaluates the maximum stresses in point-loaded (a) auxetic plates on conventional elastic foundation, (b) conventional plates on auxetic elastic foundation, and (c) auxetic plates on auxetic elastic foundation vis-à-vis conventional plates on conventional elastic foundation. Using thick plate theory for infinite plates on elastic foundation, it was found that in most cases the auxetic plates and auxetic foundation play the primary and secondary roles, respectively, in reducing the plate’s maximum stresses. It is herein suggested that, in addition to materials selection technique and other design considerations, the use of auxetic plates and/or auxetic foundation be introduced for reducing stresses in plates on elastic foundations.

Abstract: A simple approach to multi-objective optimization of machining parameters is presented. Regression analysis of experimental data is carried out to obtain the correlation between cutting parameters and response variables. Finally, Genetic Algorithm (GA) toolbox of MATLAB is used to carry out multi-objective optimization of two objective functions (surface roughness “Ra” & material removal rate “MRR”). Genetic algorithm is found to be a powerful tool for multi-objective optimization of machining parameters in this study.

Abstract: This paper presents an unconventional method to optimize the governing process parameters of Friction Stir Welding (FSW) towards the mechanical properties and weld quality. The optimization approach attempts to consider simultaneously the multiple quality characteristics namely tensile strength, nugget zone hardness and weld quality class using Multi-objective Taguchi Method (MTM). The experimental study was conducted for plate thickness of 6.0 mm under different rotational and traverse speed. The optimum welding parameters were investigated using Taguchi method with L9 orthogonal array. The significant level of the welding parameters is to be investigated by using analysis of variance (ANOVA). Furthermore, the optimum value was analyzed by means of MTM which involved the calculation of total normalized quality loss (TNQL) and multi signal to noise ratio (MSNR).

Abstract: This paper applies a central composite design (CCD) to determine proper machine parameters to reduce the cycle time of a bore grinding process. There are 6 machine parameters, which are rough grinding 2 starting position, fine grinding starting position, speed of rough grinding 1, speed of rough grinding 2, speed of rough grinding 3 and speed of fine grinding and 2 types of responses, which are cycle time and surface roughness considered in this study. A half CCD is used to find the optimal machine setup parameters. The experiment shows that new machine conditions can reduce cycle time from 2.98 second per piece to 2.76 second per piece and control surface roughness within specification of 1.0 um. After implementing the new machine conditions in the real setting, we found that the average actual cycle time is 2.76 second per piece with roughness of 0.841 um.