Advanced Materials Research Vol. 845

Abstract: This paper investigates functional properties of natural fiber reinforced composites, such as strengthening characteristics, biodegradation behavior and thermal insulating properties. These functionalities are mainly derived from inherent physical and chemical characteristics of natural plant fiber. High-strength green composites can be fabricated by using strong natural fibers. The biodegradation speed of green composites is faster than that of neat biodegradable resin used as matrix. Such enhanced biodegradation properties are attributed to the preferential biodegradation reaction at interfaces between natural fiber and biodegradable matrix polymer. In addition, better thermal insulation performance is easily attained by using natural plant fibers having a larger lumen, which is the hollow middle area of the natural fibers. Thus the thermal insulation properties of the natural fiber composites can be controlled not only by changing the thermal conductivity values of matrix polymer but also by changing the internal microstructure of the natural plant fiber, namely the size of lumen.

Abstract: Pre-clinical experimental wear testing is very effective to evaluate new ankle replacement in the aspect of design and material used. However, both cost and time can be one of the constraints factors, particularly in the early stage of design or analysis. Numerical method has been addressed as an alternative to predict wear on ankle replacement. The computational wear simulation has been widely used on the hip and knee but very less found in study related to wear analysis of the ankle. The purpose of this research is to develop computational simulation to predict wear on total ankle replacement (TAR). Three dimensional (3D) models of the right ankle TAR were developed using BOX total ankle replacement model. Mobile bearing device was developed consisting of three components tibial, bearing and talar. Each component has different design and purposes representing its physiological behaviour of the ankle. The ankle load applied was based on the joint reaction force profile at the ankle joint. This is to determine the distribution of contact stress on the meniscal bearing surfaces contact with talar component for 25 discrete instant during stance phase of gait cycle. The sliding distance was obtained from predominates motion of plantar/dorsi flexion. The computed linear wear depth and cumulative volumetric wear were 0.01614 mm per million cycles and 30.5 mm³, respectively. The values obtained were proven to be consistent with the previous in vitro result.

Abstract: Lubricant potentiality of used cooking palm oil was examined through four-ball friction test with modified palm oils of two different types. One category of tested oils was the heat-treated type which is expected as degraded palm oil by heating during cooking. The degraded degree was controlled by the length of heating period, then the acid number, AN, was varied between 0 and 3.5[mgKOH/. For these oils, temperature dependence druing friction test was examined on friction and wear between 40-100 ̊C. Degraded palm oil of higher acid number showed wear much more, and the wear for AN=3.5 showed almost double of non-heat treaed oil, but half of mineral oil, VG32, up to 85 ̊C. Friction coefficient did not show strong dependence of the acid number, and the value was 20%-lower than VG32 between 40-100 ̊ C.The other was the free-fatty acid added type which is expected as degraded palm oil by hydrolysis during cooking where boiled water reacts with palm oil. Four model oils were prepared, and each of them contained one of major palm oil components, such as palmitic acid, stearic acid, oleic acid and linoleic acid, at 10mass% to refined palm oil. For these oils, friction test was performed at 40 and 100 ̊ C to examine the effect of temperature. Addition of stearic acid showed lowest wear and lowest friction at both temperatures among fatty acid added types. The experimental results are discussed with kinematic viscosity, apprent normal stress, and apprent tangential shear stress.

Abstract: Recently, Composite Sandwich Panel (CSP) technology considerably influenced the design and fabrication of high performance structures. Although using CSP increases the reliability of structure, the important concern is to understand the complex deformation and damage evolution process. This study is focused on the flexural and indentation behavior of CSP made of chopped strand mat glass fiber and polyester matrix as face sheets and polyurethane foam as foam core subject to flexural and indentation loading condition. A setup of three-point bending and indentation test is prepared using different strain rates of 1mm/min, 10mm/min, 100mm/min and 500mm/min to determine the effects of strain rate on flexural and indentation behavior of CSP material. The load-extension, stress-extension response and energy absorption of the panel show the relation between the flexural and indentation behavior of panels to strain rate as by increasing the strain rate, the flexural properties and the energy absorption of panel are increased.

Abstract: Linear elastic response of the bovine cortical bone has been examined under compression load. Experimental and computational methods were used to observe and predict the response of cortical bone. In computational method, two mechanical behaviors of isotropic and orthotropic were considered to simulate the cortical bone deformation. In experimental process, the specimens were designed to show maximum stiffness and strength by specifying osteon direction along loading axis during tests. The tests were controlled by displacement rate of 0.5 mm/minute and the overall stiffness responses of the structures were recorded to extract mechanical properties and also for validation aims. Finite Element Method (FEM) was used to model the linear response of the structure by using ABAQUS6.9EF. The FE results using orthotropic definition shows a good correlation with experimental data. A discussion was given based on overall stiffness and effective stress variation for both mechanical behaviors. In order to design the optimal implant structure, the presented study was proposed for prediction of bone structure deformation that attached to the orthopedic implants.

Abstract: Thermal barrier coating (TBC) system has been developed for high temperature applications along with the used of yttria stabilized zirconia (YSZ) as topcoat. Recently, developing coating material made from nanoparticles is widely explored. Thus, maerogel could become a potential candidate for this purpose because it consists of nano porous particle with low in density and low in thermal conductivity. The coating is expected to improve the formation of thermally grown oxide (TGO), thermal stability and increase the insulating capability. However, maerogel need agglomeration process before coating can be made because of it has low mass and high specific area.

Abstract: During daily activities, trabecular bone need to bear certain amount of load which also leads to movement of the bone marrow within the structure. The flow of the bone marrow within the trabecular bone structure cause the shear stress which affect the nutrient transport, the properties of the bone and also the bone fatigue life. The aim of this paper is to simulate the trabecular structure using FSI approach in order to study the effect of the fluid flow to the structure. In this study, idealized model with 50% of porosity was used in the simulation and 1mm displacement applied on top of the model. Three different types of analysis were used in order to differentiate between CFD, CSM and FSI results. The results showed significant value between these analyses was concluded that FSI approaches is the best to mimic the real body condition.

Abstract: This work presents a simulation study on a novel micro thermal sensor to evaluate a different range of temperature. Micro Electro Mechanical Systems (MEMS) technology is an interesting field in mechanics andmetrology. In this work, a capacitive micro thermal sensor based on tip deflection of Functionally Graded Micro-beam (FGM) was designed. The thermo-electric mechanical equations based on Euler-Bernoulli beam theory were derived and solved using step-by-step linearization method. The increase in temperature was expressed with respect to the changes in the capacitance. The beam deflections were compared with the existing results showing good conformity with the highest error obtained as 4.3% at 65°C.

Abstract: This paper used molecular dynamics (MD) simulations to investigate influences of cone arrangements (including the cone orientation, arrangement pattern and cone spacing) on hydrogen adsorption of open-tip carbon nanocone (CNC) arrays at temperatures of 100 and 300 K. To consider curvature effects for the cone structure of the CNCs, the curvature-modified Lennard-Jones potential parameters were adopted to describe the interactions between the hydrogen and carbon atoms. It was found that the cone orientation (aligned, opposite, and alternate) does not have obvious influences on hydrogen adsorption of the CNC arrays. The arrangement pattern (square and triangular), however, had significant influences on the hydrogen adsorption. The square-patterned CNC array was noticed to have higher storage weight percentage than the triangular-patterned one. Regarding to the influences of cone spacing, the storage weight percentage grew with the increase of the cone spacing and arrived at a stable value as the cone spacing reached a certain critical value. The influences cone arrangements could be ascribed to repulsive effects, which are evident as cone spacing become narrow.

Abstract: Excessive piping vibrations are a major cause of machinery downtime, leaks, fatigue failure, high noise, fires and explosions in refineries and petrochemical plants. In piping system, vibration excitation sources may come from mechanical sources, hydraulics sources or can be the combination of both. Low level vibration amplitude can be amplified when acoustic natural frequency of piping system coincide with the mechanical natural frequency of the piping system of which could lead to piping failure. To address these issues, several condition monitoring techniques to assess and detect excessive piping vibration is discussed in this paper.